Co-reporter:Pierre M. Beaujuge, Svetlana V. Vasilyeva, David Y. Liu, Stefan Ellinger, Tracy D. McCarley, and John R. Reynolds
Chemistry of Materials 2012 Volume 24(Issue 2) pp:255
Publication Date(Web):January 5, 2012
DOI:10.1021/cm202117d
The continuing search for relevant structure–property relationships in the area of organic electronics is expected to impact both intrinsic material performance capability and the viability of their implementation in a broad range of device applications. Cathodically coloring π-conjugated polymer electrochromes represent a class of materials potentially attractive for low-cost and nonemissive flexible display devices including e-paper. Nonetheless, both the synthetic access to a full range of visible colors and the ability to produce solution-processable systems that switch rapidly and durably from a colored neutral state to a highly transmissive doped state upon electrochemical oxidation require that material structure–property relationships be carefully examined. In this report, we correlate molecular structure effects, redox properties, and electrochromic performance for a series of rationally designed neutral-state green polymers composed of electron-rich 3,4-dioxythiophene (DOT) units and the electron-deficient core 2,1,3-benzothiadiazole (BTD). While homopolymers synthesized from 3,4-alkylenedioxy-bridged monomers including 3,4-ethylenedioxythiophene (EDOT) and 3,4-propylenedioxythiophenes (ProDOT) have shown particularly desirable redox-switching properties in the early years of electrochromic polymer development, their “unbridged” dialkoxythiophene counterparts (DalkOTs) have not raised the same initial interest. Herein, it is shown that low band gap systems relying on DalkOT units and electron-deficient BTD cores could represent viable alternatives to their ProDOT-based counterparts in electrochemical devices involving green-to-transmissive switching electrochromes. Interestingly, provided the set of materials examined in this study, the long-term switching stability of the ProDOT-co-BTD system remains superior to that of its polymeric analog relying on DalkOTs – exhibiting less than 15% loss of contrast over 20,000 switching cycles (atmospheric conditions). Long-term cycle life is further demonstrated in a window-type device integrating the ProDOT-co-BTD system. DFT calculations performed at the B3LYP/6-31G** level suggest subtle variations in the energy-band structure of the polymer repeat-units and predict the existence of the dual band of optical absorption exhibited by the low-band gap polymers.Keywords: 2,1,3-benzothiadiazole; 3,4-propylenedioxythiophene; dialkoxythiophene; dioxythiophene; donor−acceptor; electrochromic device; electrochromic polymer; green-to-transmissive electrochrome; low band gap; ProDOT; spray-processable;
Co-reporter:Dinesh G. (Dan) Patel, Kenneth R. Graham and John R. Reynolds
Journal of Materials Chemistry A 2012 vol. 22(Issue 7) pp:3004-3014
Publication Date(Web):03 Jan 2012
DOI:10.1039/C2JM14591J
We report on the synthesis of a polyfluorene derivative, PFO(X), with furan pendant groups capable of Diels–Alder crosslinking with a maleimide containing small molecule passive crosslinker (PC) and a maleimide containing red emitting donor–acceptor–donor dopant molecule, bE-BTD(X). It was initially intended that a blend of these three components would afford a system where the dopant concentration could be increased to the point where complete energy transfer from the host polymer to the emissive dopant would be achieved. Because such systems often suffer from quenching and shifts in emission maxima indicative of emitter aggregation, it was hypothesized that crosslinking the emissive dopant with the host polymer would lead to de-aggregation of the dopant emitter. In thin films of PFO(X) and bE-BTD(X), a 16 nm bathochromic shift is observed in the emission maximum when the dopant concentration is increased from 1% to 8%, suggesting that the dopant is aggregating. In similar films where PC is included and the film is heated to affect crosslinking, a comparable 16 nm shift in the emission maximum is observed indicating that aggregation is still occurring and not affected by the heating step. Similar decreases in luminance are observed independent of whether the heating step is included. Not unexpectedly, however, crosslinking does afford an insoluble network that allows for the subsequent solution deposition of additional layers. When an electron transport layer (ETL) is used in PFO(X)/PC devices, increases of 190% and 490% are observed in luminance and luminous efficiency, respectively, relative to devices without an ETL indicating that this Diels–Alder crosslinkable system is amenable to multilayer deposition by solution methods. When bE-BTD(X) is included as the dopant emitter, similar increases in luminance and luminous efficiency are observed with the ETL included compared to devices where this layer is omitted.
Co-reporter:Jegadesan Subbiah, Chad M. Amb, Irfan Irfan, Yongli Gao, John R. Reynolds, and Franky So
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 2) pp:866
Publication Date(Web):January 7, 2012
DOI:10.1021/am201537p
We have studied the performance of normal and inverted bulk-heterojunction solar cells with an active layer composed of a blend of poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl] (PDTS-BTD) and {6,6}-phenyl-C71 butyric acid methyl ester (PC71BM). For inverted cells, a thin layer of ZnO nanoparticles and MoO3 were used as interlayers for the bottom cathode and the top anode respectively. To enhance the device performance, a thin film of 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MTDATA) was used along with MoO3 as an anode interlayer to improve the hole extraction from the photoactive layer to the anode. The inverted polymer solar cells with double interlayer exhibit a higher power conversion efficiency of 6.45% compared to the conventional cell of 4.91% due to efficient charge extraction and favorable vertical morphology of active layer blend. Our ultraviolet photoemission spectroscopy results indicate that the formation of band bending due to interlayer leads to the enhancement in hole extraction.Keywords: bulk heterojunction; conjugated polymers; donor−acceptor; inverted solar cell; low bandgap; photovoltaic; silole polymer;
Co-reporter:Brian S. Aitken, Patrick M. Wieruszewski, Kenneth R. Graham, John R. Reynolds, and Kenneth B. Wagener
ACS Macro Letters 2012 Volume 1(Issue 2) pp:324
Publication Date(Web):February 3, 2012
DOI:10.1021/mz2001725
A set of six perfectly regioregular pendant 2,7-bis(phenyl-m-toluylamino)fluorene (TPF) functionalized polyolefins for use as charge transporting materials in polymer light emitting diodes (PLEDs) were prepared and characterized. Synthesis of these materials is straightforward, requiring only three or four steps, depending on the polymer, and final isolated yields over all steps combined were greater than 40% in all but one case. Most notably, these materials exhibit charge-carrier mobilities that can be controlled over 3 orders of magnitude by variation of the number of intermediary carbons (spacer length) between the pendant TPF groups. The range of hole mobilities encompasses the electron mobilities of common electron transport materials/emitters such as Alq3 and PBD, thus, affording the opportunity to fabricate electroactive polyolefin based PLEDs with well matched charge-carrier mobilities and improved performance. We believe this approach to charge-carrier mobility control in electroactive materials could be easily extended to other aryl systems with different HOMO–LUMO levels for energy level and mobility matching with various emitters.
Co-reporter:Romain Stalder, Caroline Grand, Jegadesan Subbiah, Franky So and John R. Reynolds
Polymer Chemistry 2012 vol. 3(Issue 1) pp:89-92
Publication Date(Web):27 Oct 2011
DOI:10.1039/C1PY00402F
The copolymer of isoindigo and dithieno[3,2-b:2′,3′-d]silole, P(iI-DTS), is reported as prepared by Stille coupling to yield a soluble high molecular weight material absorbing light throughout the visible spectrum up to 800 nm. With deep HOMO and LUMO energy levels (high ionization potential and electron affinity) electrochemically measured at −5.55 and −3.95 eV respectively, this new p-type polymer enabled the fabrication of high open circuit voltage polymer solar cells when blended with fullerene derivatives. By employing solvent additives, the morphology of the devices was optimized to yield power conversion efficiencies of 4%.
Co-reporter:Brian S. Aitken, Patrick M. Wieruszewski, Kenneth R. Graham, John R. Reynolds, and Kenneth B. Wagener
Macromolecules 2012 Volume 45(Issue 2) pp:705-712
Publication Date(Web):January 6, 2012
DOI:10.1021/ma202409k
Acyclic diene metathesis polymerization (ADMET) was used to synthesize a series of perfectly regioregular polyolefins, in which the number of backbone atoms between pendant terfluorene groups was precisely controlled at 8, 14, or 20 carbons. Analogous random copolymers containing identical chromophore densities were also synthesized to study the impact of regioregularity on the performance of this class of materials in polymer light emitting diodes (PLEDs). Additionally, the backbone alkene remnants of ADMET were saturated to generate materials with somewhat different ordering. These saturated derivatives led to improvements in PLED external quantum efficiencies (EQEs) over their unsaturated analogues in most cases, with a large improvement in one material. Charge mobility, as manifested in current density during PLED characterization, and relative solid-state fluorescence quantum yield (ΦF) also exhibit reasonable dependencies, with longer distances between electroactive groups yielding lower PLED current densities and higher ΦF. Regioregularity has the opposite effect, giving rise to higher current densities and lower ΦF as compared to regiorandom analogues.
Co-reporter:Song Chen;Kaushik Roy Choudhury;Jegadesan Subbiah;Chad M. Amb;Franky So
Advanced Energy Materials 2011 Volume 1( Issue 5) pp:963-969
Publication Date(Web):
DOI:10.1002/aenm.201100300
Abstract
Photo-current loss in donor-acceptor (DA) polymer-fullerene bulk heterojunction solar cells was studied via carrier transport and recombination measurements. Focusing on the DA polymer poly((4,4-dioctyldithieno (3,2-b:2',3'-d) silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl) (DTS-BTD) we found that the carrier transport is well-balanced and attribute the loss mechanism in DTS-BTD solar cells to carrier recombination. Using carrier extraction with linear increasing voltage (photo-CELIV) and transient photo-voltage (TPV), we show that carrier recombination plays an important role in photo-current extraction at open circuit conditions due to increase in photo-excited carrier concentration. Delay time dependent photo-CELIV and temperature dependent transport studies suggest that the recombination rate is related to the degree of energetic disorder in the polymer: fullerene blends.
Co-reporter:Chad M. Amb ; Song Chen ; Kenneth R. Graham ; Jegadesan Subbiah ; Cephas E. Small ; Franky So
Journal of the American Chemical Society 2011 Volume 133(Issue 26) pp:10062-10065
Publication Date(Web):June 6, 2011
DOI:10.1021/ja204056m
We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC70BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.
Co-reporter:Egle Puodziukynaite ; Justin L. Oberst ; Aubrey L. Dyer
Journal of the American Chemical Society 2011 Volume 134(Issue 2) pp:968-978
Publication Date(Web):December 29, 2011
DOI:10.1021/ja2065297
A combination of electrochromism and electroluminescence in functional materials could lead to single-layer dual electrochromic/electroluminescent (EC/EL) display devices, capable of simultaneous operation in emissive and reflective modes. Whereas such next generation displays could provide optimal visibility in any ambient lighting situation, materials available that exhibit such characteristics in the active layer are limited due to the required intrinsic multifunctionality (i.e., redox activity, electroluminescence, electrochromism, and ion conductivity) and to date can only be achieved via the rational design of ionic transition-metal complexes. Reported herein is the synthesis and characterization of a new family of acrylate-containing ruthenium (tris)bipyridine-based coordination complexes with multifunctional characteristics. Potential use of the presented compounds in EC/EL devices is established, as they are applied as cross-linked electrochromic films and electrochemiluminescent layers in light-emitting electrochemical cell devices. Electrochromic switching of the polymeric networks between yellow, orange, green, brown and transmissive states is demonstrated, and electrochemiluminescent devices based on the complexes synthesized show red-orange to deep red emission with λmax ranging from 680 to 722 nm and luminance up to 135 cd/m2. Additionally, a dual EC/EL device prototype is presented where light emission and multicolor electrochromism occur from the same pixel comprised of a single active layer, demonstrating a true combination of these properties in ionic transition-metal complexes.
Co-reporter:David Y. Liu;Andrew D. Chilton;Pengjie Shi;Michael R. Craig;Steven D. Miles;Aubrey L. Dyer;Vincent W. Ballarotto
Advanced Functional Materials 2011 Volume 21( Issue 23) pp:4535-4542
Publication Date(Web):
DOI:10.1002/adfm.201101605
Abstract
As electrochromic polymers can switch with a high transmittance contrast in the sub-second time frame, an analytical tool to rapidly probe the electrochemically-induced optical transition is required for characterization of these materials for electronic displays and smart windows. A novel technique is described to synchronize the electrochemical and optical measurements by utilizing an external trigger to facilitate coordinated communication between the potentiostat, which applies a voltage to the electrode supported electrochromic polymers, and the optical spectrometer that records the induced optical transitions. By using a spectrometer containing a photodiode array detector, these measurements are capable of rapid data acquisition to track the electrochromic change in the polymer films, with as many as 500 spectra captured during a one-second switch of the polymer from a colored, neutral to highly transmissive state. Additionally, with this rapid, full-spectral measurement, it is possible to trace the temporal evolution of the electrochromic change to determine the presence of intermediate color tones, as well as their duration. Here, three polymers are shown, ECP-Magenta, ECP-Green, and ECP-Black, which obtain high transmittance contrast between 40 to 50 Δ%T, with sub-second switching times measured in the range of 400 to 700 ms, demonstrating their potential for use in electrochromic windows and displays where rapid transitions are desired.
Co-reporter:Kenneth R. Graham, Yixing Yang, Jonathan R. Sommer, Abigail H. Shelton, Kirk S. Schanze, Jiangeng Xue, and John R. Reynolds
Chemistry of Materials 2011 Volume 23(Issue 24) pp:5305
Publication Date(Web):November 23, 2011
DOI:10.1021/cm202242x
A family of π-extended platinum(II) porphyrins has been synthesized and incorporated into solution processed polymer light emitting diodes (PLEDs) and vapor deposited multilayer organic light emitting diodes (OLEDs), giving rise to devices with peak emission ranging from 771 to 1005 nm. The longest wavelength emitter, platinum(II)-5,10,15,20-(3,5-di-tert-butylphenyl)tetraanthroporphyrin (Pt-Ar4TAP), shows an emission maximum at 1005 nm, an external quantum efficiency (EQE) of 0.12%, and a maximum radiant emittance (Rmax) of 0.23 mW/cm2 in single layer PLED architectures, which is enhanced to an EQE of 0.20% with an Rmax of 0.57 mW/cm2 upon vapor deposition of an electron transport layer. In an effort to understand substituent effects and enhance the performance of π-extended Pt-porphyrins in PLEDs and OLEDs, a family of Pt-tetrabenzoporphyrins (Pt-TBPs) with varying functionality was investigated. The luminescent lifetimes of the Pt-TBPs in solution and in films were measured, and a strong correlation was demonstrated between the film lifetimes and the PLED and OLED efficiencies. An improvement in external quantum efficiency (EQE) from 2.07 to 2.49% for PLEDs and from 8.0 to 9.2% for OLEDs was observed between the less substituted Pt-tetraphenyltetrabenzoporphyrin and the more substituted Pt-5,10,15,20-(3,5-di-tert-butylphenyl)tetrabenzoporphyrin. The PLED EQEs were further enhanced to 3.02% with the disubstituted Pt-5,15-(3,5-di-tert-butylphenyl)tetrabenzoporphyrin; however, this increase was not observed for the OLEDs where an EQE of 7.8% was measured.Keywords: electroluminescence; near-infrared; organic light emitting diode; platinum(II) porphyrin;
Co-reporter:Chad M. Amb, Aubrey L. Dyer, and John R. Reynolds
Chemistry of Materials 2011 Volume 23(Issue 3) pp:397
Publication Date(Web):November 10, 2010
DOI:10.1021/cm1021245
Solution-processable electrochromic (EC) polymers that can be switched from one distinct color state to a highly transmissive and near colorless state are required for applications in both EC windows and displays. Using a tour around the color wheel, we describe the various EC polymer (ECP) compositions that now make a full palette of colors available demonstrating a set of structure−property relationships. Electrochemical and electrochromic characterization methodologies are described and their application to ECPs demonstrated. Processing and patterning methods including spray casting, screen-, flexo-, and ink jet printing, along with photo- and soft lithography are described. Absorptive/transmissive (window type) and absorptive/reflective (display type) devices are described as platforms for practical applications.
Co-reporter:Unsal Koldemir, Kenneth R. Graham, Danielle H. Salazar, Tracy D. McCarley and John R. Reynolds
Journal of Materials Chemistry A 2011 vol. 21(Issue 18) pp:6480-6482
Publication Date(Web):29 Mar 2011
DOI:10.1039/C1JM10345H
We demonstrate the ability of a new alternating polyfluorene (APFO) type polymer employing dialkoxythiophene moieties to operate efficiently as both an electrochromic (EC) and electroluminescent (EL) material, thereby providing for incorporation into a dual EC/EL device. In addition, the new APFO type polymer was blended with PC[70]BM in a bulk heterojunction photovoltaic cell resulting in a power conversion efficiency of 1.66% with a high open circuit voltage of 0.87 volts.
Co-reporter:Svetlana V. Vasilyeva, Pierre M. Beaujuge, Shujun Wang, Joseph E. Babiarz, Vincent W. Ballarotto, and John R. Reynolds
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 4) pp:1022
Publication Date(Web):March 11, 2011
DOI:10.1021/am101148s
Black-to-transmissive switching polymer electrochromic devices (ECDs) were designed using a set of spray-processable cathodically coloring polymers, a non-color-changing electroactive polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) as the charge-compensating counter electrode, and a highly conducting gel electrolyte (6.5 mS cm−1). The color “black” was obtained by utilizing (1) individual copolymers absorbing across the visible spectrum, and (2) blends and bilayers of several polymer electrochromes with complementary spectral absorption. Neutral-state black and ink-like dark purple-blue (or “ink-black”) donor−acceptor (DA) copolymers composed of the electron-donor 3,4-propylenedioxythiophene (ProDOT) and the electron-acceptor 2,1,3-benzothiadiazole (BTD) building units, which possess relatively homogeneous absorption profiles across the visible spectrum, were chosen for their propensity to switch to transmissive states upon electrochemical oxidation. A blend of magenta and cyan polymers (PProDOT-(CH2OEtHx)2 and P(ProDOT-BTD-ProDOT), respectively) was produced with the goal of generating the same dark purple-blue color as that obtained with the “ink-black” DA copolymer. While the multi-polymer ECDs demonstrate high contrasts (up to 50%T), and switch from a saturated purple-blue color (L* = 32, a* = 13, b* = −46) to a light green-blue transmissive state (L* = 83, a* = −3, b* = −6), devices made with the DA electrochromic copolymers switch more than two times faster (0.7 s to attain 95% of the full optical change) than those involving the polymer blends (1.6 s), and exhibit more neutral achromatic colors (L* = 38, a* = 5, b* = −25 for the colored state and L* = 87, a* = −3, b* = −2 for the bleached state, correspondingly). The results obtained suggest that these materials should prove to be applicable in both transmissive- (window-type) and reflective-type ECDs.Keywords: conjugated polymer; electrochromic device; electrochromism
Co-reporter:Aubrey L. Dyer, Emily J. Thompson, and John R. Reynolds
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 6) pp:1787
Publication Date(Web):April 15, 2011
DOI:10.1021/am200040p
The field of electrochromic polymers has now reached an important milestone with the availability of a yellow to fully transmissive, cathodically coloring, solution-processable electroactive polymer. This is in addition to previously published electrochromic polymers that have neutral state colors that span from orange, red, magenta, blue, cyan, green, and black, that also attain highly transmissive states upon switching. With this, the full color palette is now complete allowing the largest variety of colors for transmissive and reflective electrochromic display applications. Here, we report on how we have been able to obtain this full color palette through synthetic modifications and color tuning utilizing electron rich and donor−acceptor repeat units, electron-donating substituents, and steric interactions with our 3,4-alkylenedioxythiophene family of polymers. Additionally, using solubilizing pendant groups for both organic and aqueous compatibility, we have been able to create this color palette with fully solution processable materials, paving the way for materials patterning, printing, and incorporation into devices for display and window applications.Keywords: conjugated electroactive polymers; electrochromic windows; electrochromics; information displays; multicolor polymers
Co-reporter:Kenneth R. Graham, Jianguo Mei, Romain Stalder, Jae Won Shim, Hyeunseok Cheun, Fred Steffy, Franky So, Bernard Kippelen, and John R. Reynolds
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 4) pp:1210
Publication Date(Web):March 15, 2011
DOI:10.1021/am2000328
The effect of the macromolecular additive, polydimethylsiloxane (PDMS), on the performance of solution processed molecular bulk heterojunction solar cells is investigated, and the addition of PDMS is shown to improve device power conversion efficiency by ∼70% and significantly reduce cell-to-cell variation, from a power conversion efficiency of 1.25 ± 0.37% with no PDMS to 2.16 ± 0.09% upon the addition of 0.1 mg/mL PDMS to the casting solution. The cells are based on a thiophene and isoindigo containing oligomer as the electron donor and [6,6]-phenyl-C61 butyric acid methyl ester (PC61BM) as the electron acceptor. PDMS is shown to have a strong influence on film morphology, with a significant decrease in film roughness and feature size observed. The morphology change leads to improved performance parameters, most notably an increase in the short circuit current density from 4.3 to 6.8 mA/cm2 upon addition of 0.1 mg/mL PDMS. The use of PDMS is of particular interest, as this additive appears frequently as a lubricant in plastic syringes commonly used in device fabrication; therefore, PDMS may unintentionally be incorporated into device active layers.Keywords: additive processing; bulk heterojunction; molecular photovoltaic cell; morphology control; organic solar cell
Co-reporter:Chad M. Amb, Justin A. Kerszulis, Emily J. Thompson, Aubrey L. Dyer and John R. Reynolds
Polymer Chemistry 2011 vol. 2(Issue 4) pp:812-814
Publication Date(Web):01 Feb 2011
DOI:10.1039/C0PY00405G
In order to create multicolour displays using electrochromic (EC) technologies, the modulation of the intensity of three primary subtractive colours (red, yellow, blue, or cyan, magenta, yellow) could be used to express any colour in the spectrum. Herein we report the first cathodically colouring yellow-to-transmissive switching EC polymer, which completes a full colour palette and promises to fulfil the requirements necessary to create multicolour EC displays.
Co-reporter:Quentin Bricaud, Roxane M. Fabre, Robert N. Brookins, Kirk S. Schanze, and John R. Reynolds
Langmuir 2011 Volume 27(Issue 8) pp:5021-5028
Publication Date(Web):March 29, 2011
DOI:10.1021/la105113k
We present a study of Förster resonance energy transfer (FRET) between two emissive conjugated polyelectrolytes (CPEs) in layer-by-layer (LbL) self-assembled films as a means of examining their organization and architecture. The two CPEs are a carboxylic acid functionalized polyfluorene (PFl-CO2) and thienylene linked poly(phenylene ethynylene) (PPE-Th-CO2). The PFl-CO2 presents a maximum emission at 418 nm, while the PPE-Th-CO2 has an absorption λmax centered at 431 nm, in sufficient proximity for effective FRET. Several LbL films have been constructed using varied concentrations of the deposition solutions and identity of the buffer layers separating the two emissive layers, using a system of either weak polyelectrolytes, poly(allylamine hydrochloride) (PAH)/poly(sodium methacrylate) (PMA), or strong polyelectrolytes, poly(diallylammonium chloride) (PDDA)/poly(styrene sulfonate) sodium (PSS). The efficiency of FRET has been monitored using fluorescence spectroscopy. Initially, the fluorescence of the PFl-CO2 (Eg ∼ 3.0 eV), which emits at 420 nm, is quenched by the lower band gap PPE-Th-CO2 (Eg ∼ 2.5 eV). For films using the PAH/PMA system as buffer bilayers and deposited from 1 mM solutions, the PFl-CO2 fluorescence is progressively recovered as the number of intervening buffer bilayers is increased. Ellipsometry measurements indicate that energy transfer between the two emissive layers is efficient to a distance of ca. 7 nm.
Co-reporter:Frank A. Arroyave and John R. Reynolds
The Journal of Organic Chemistry 2011 Volume 76(Issue 21) pp:8621-8628
Publication Date(Web):October 13, 2011
DOI:10.1021/jo201770j
A general scheme for the synthesis of π-conjugated molecules based on 3,4-dioxypyrroles is presented. The π-conjugated molecules were synthesized via Pd-mediated decarboxylative cross-coupling using various 3,4-propylenedioxypyrrole carboxylic acids and aryl bromides, including the base-sensitive electron acceptor 4,7-dibromobenzo[c][1,2,5]thiadiazole (BTD). N-Methylpyrrolidone was used as solvent, Pd(acac)2 was employed as the palladium source and P(o-tol)3 as the ligand. The methodology was applied to 3,4-dioxypyrrole monoacids and 3,4-dioxypyrrole diacids to produce multi-ring π-conjugated systems containing phenyl, thiophenyl, BTD, and pyridinyl units. In general, the method has yielded a practical approach for the synthesis of 3,4-dioxypyrrole-based π-conjugated molecules in acceptable to high yields of 44–94%.
Co-reporter:Dinesh G. “Dan” Patel;Yu-ya Ohnishi;Yixing Yang;Sang-Hyun Eom;Richard T. Farley;Kenneth R. Graham;Jiangeng Xue;So Hirata;Kirk S. Schanze
Journal of Polymer Science Part B: Polymer Physics 2011 Volume 49( Issue 8) pp:557-565
Publication Date(Web):
DOI:10.1002/polb.22224
Abstract
We report the synthesis of a 3-ethylhexyloxy substituted poly(meta-phenylene), EHO-PMP that shows absorption and solid state photoluminescence exclusively in the UV region of the electromagnetic spectrum with an emission maximum of 345 nm. Computational analysis of model oligomers by DFT methods indicates that EHO-PMP is a wide bandgap polymer with the HOMO being localized on a dimeric (biphenyl) unit and with the LUMO being more delocalized. The energy of the LUMO, however, suggests that inefficient electron injection would occur from currently available cathode materials in standard light-emitting device architectures, and this was observed experimentally. The computational results, coupled with experimental observation, lead us to believe that efficient electroluminescence from organic polymer UV emitters requires advances in electron transport layers and cathode materials. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Co-reporter:Romain Stalder, Jianguo Mei, Jegadesan Subbiah, Caroline Grand, Leandro A. Estrada, Franky So, and John R. Reynolds
Macromolecules 2011 Volume 44(Issue 16) pp:6303-6310
Publication Date(Web):July 29, 2011
DOI:10.1021/ma2012706
The conjugated electron acceptor isoindigo was used to synthesize two conjugated polymers with backbones composed exclusively of electron-deficient units. Suzuki polycondensation afforded the homopolymer of isoindigo and a copolymer with 2,1,3-benzothiadiazole as repeat unit. The materials are thermally stable up to 380 °C, along with being soluble in and processable from common organic solvents. The polymers absorb light broadly throughout the visible spectrum, with optical bandgaps of 1.70 and 1.77 eV, respectively. Both polymers reduce reversibly with LUMO energy levels at −3.84 and −3.90 eV for the homopolymer and the copolymer, respectively, close to the value of −4.10 eV found for fullerenes such as PC60BM when measured under identical conditions. The polymers HOMO levels were calculated at −5.54 and −5.67 eV, respectively, based on their optical band gaps. Spectroelectrochemical measurements on thin films of the homopolymer showed the generation of stable negative charge carriers, accompanied by colored-to-transmissive electrochromism in the films upon reduction. The n-type character of these polymers motivated the fabrication of all-polymer solar cells using blends of poly(3-hexylthiophene) and the homopolymer of isoindigo, yielding efficiencies approaching 0.5%, with room for optimization based on the observed surface morphology of the blend films.
Co-reporter:Pierre M. Beaujuge, Chad M. Amb, and John R. Reynolds
Accounts of Chemical Research 2010 Volume 43(Issue 11) pp:1396
Publication Date(Web):August 20, 2010
DOI:10.1021/ar100043u
With the development of light-harvesting organic materials for solar cell applications and molecular systems with fine-tuned colors for nonemissive electrochromic devices (e.g., smart windows, e-papers), a number of technical challenges remain to be overcome. Over the years, the concept of “spectral engineering” (tailoring the complex interplay between molecular physics and the various optical phenomena occurring across the electromagnetic spectrum) has become increasingly relevant in the field of π-conjugated organic polymers. Within the spectral engineering toolbox, the “donor−acceptor” approach uses alternating electron-rich and electron-deficient moieties along a π-conjugated backbone. This approach has proved especially valuable in the synthesis of dual-band and broadly absorbing chromophores with useful photovoltaic and electrochromic properties. In this Account, we highlight and provide insight into a present controversy surrounding the origin of the dual band of absorption sometimes encountered in semiconducting polymers structured using the “donor−acceptor” approach. Based on empirical evidence, we provide some schematic representations to describe the possible mechanisms governing the evolution of the two-band spectral absorption observed on varying the relative composition of electron-rich and electron-deficient substituents along the π-conjugated backbone. In parallel, we draw attention to the choice of the method employed to estimate and compare the absorption coefficients of polymer chromophores exhibiting distinct repeat unit lengths, and containing various extents of solubilizing side-chains along their backbone. Finally, we discuss the common assumption that “donor−acceptor” systems should have systematically lower absorption coefficients than their “all-donor” counterparts. The proposed models point toward important theoretical parameters which could be further explored at the macromolecular level to help researchers take full advantage of the complex interactions taking place in π-conjugated polymers with intramolecular “donor−acceptor” characteristics.
Co-reporter:Chad M. Amb;Pierre M. Beaujuge
Advanced Materials 2010 Volume 22( Issue 6) pp:724-728
Publication Date(Web):
DOI:10.1002/adma.200902917
Co-reporter:Pengjie Shi;Chad M. Amb;Eric P. Knott;Emily J. Thompson;David Y. Liu;Jianguo Mei;Aubrey L. Dyer
Advanced Materials 2010 Volume 22( Issue 44) pp:4949-4953
Publication Date(Web):
DOI:10.1002/adma.201002234
Co-reporter:Pierre M. Beaujuge;Chad M. Amb
Advanced Materials 2010 Volume 22( Issue 47) pp:5383-5387
Publication Date(Web):
DOI:10.1002/adma.201003116
Co-reporter:Pierre M. Beaujuge, Jegadesan Subbiah, Kaushik Roy Choudhury, Stefan Ellinger, Tracy D. McCarley, Franky So and John R. Reynolds
Chemistry of Materials 2010 Volume 22(Issue 6) pp:2093
Publication Date(Web):February 4, 2010
DOI:10.1021/cm903495b
With the perspective of producing power-generating displays of various colors based on π-conjugated semiconducting polymers, we have developed a synthetic design aimed at addressing color states commonly difficult to attain. Herein, we report on the structure−property relationships and performance in photovoltaic devices of a series of green-colored donor−acceptor (DA) π-conjugated polymers comprised of electron-rich 3,4-dioxythiophenes (DOTs) and the electron-deficient 2,1,3-benzothiadiazole (BTD). In particular, the synthesis and chemical polymerization of two DOT-BTD regiosymmetric oligomers (pentamers M2 and M3), that can be chemically oxidized to yield two-band absorbing polymers with a transmission window in the 480−560 nm range hence reflecting/transmitting the color green (P2 and P3), is reported. The optical and electrochemical properties of P2 and P3 are described and compared to those of a blue-colored parent polymer (P1) obtained via the polymerization of a smaller DOT-BTD oligomeric precursor (trimer M1). The photovoltaic (PV) properties of P1−P3 were investigated in DA bulk heterojunction (BHJ) devices with PC60BM as the acceptor. P2 and P3 afforded green-colored devices with up to 1.9% power conversion efficiency (PCE) under AM 1.5 G solar illumination. Taking into account the differences in polymer energy band structure, we have replaced PEDOT:PSS by MoO3 and optimized the solar-cell device configuration for the most efficient polymer derivative (P3), demonstrating up to a 2.71% PCE. Insight into the morphology and charge transport of these polymers in blends with PCBM is provided and related to the synthetic design and PV device performance.
Co-reporter:Yixing Yang, Pamela Cohn, Aubrey L. Dyer, Sang-Hyun Eom, John R. Reynolds, Ronald K. Castellano and Jiangeng Xue
Chemistry of Materials 2010 Volume 22(Issue 12) pp:3580
Publication Date(Web):May 25, 2010
DOI:10.1021/cm100407n
Co-reporter:Xuan Zhang, Timothy T. Steckler, Raghunath R. Dasari, Shino Ohira, William J. Potscavage, Shree Prakash Tiwari, Séverine Coppée, Stefan Ellinger, Stephen Barlow, Jean-Luc Brédas, Bernard Kippelen, John R. Reynolds and Seth R. Marder
Journal of Materials Chemistry A 2010 vol. 20(Issue 1) pp:123-134
Publication Date(Web):16 Nov 2009
DOI:10.1039/B915940A
A series of highly soluble donor–acceptor (D–A) copolymers containing N-(3,4,5-tri-n-decyloxyphenyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP) or N-(2-decyltetradecyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP′) as donor and three different acceptors, 4,7-dithien-2-yl-[2,1,3]-benzothiadiazole, 4,9-dithien-2-yl-6,7-di-n-hexyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline and 4,8-dithien-2-yl-2λ4δ2-benzo[1,2-c;4,5-c′]bis[1,2,5]thiadiazole (BThX, X = BTD, TQHx2, BBT, respectively) were synthesized by Stille coupling polymerizations. The optical and electrochemical properties of these copolymers were investigated, along with their use in field-effect transistors and photovoltaic devices. The band gaps (eV) estimated from UV-vis-NIR spectra and electrochemical measurements of the copolymers varied from ca. 1.5–0.5 eV, and were consistent with quantum-chemical estimates extrapolated using density functional theory. Oxidative and reductive spectroelectrochemistry of the copolymers indicated they can be both p-doped and n-doped, and three to four differently colored redox states of the polymers can be accessed through electrochemical oxidation or reduction. The DTP-BThBTD and DTP-BThTQHx2 copolymers exhibited average field-effect hole mobilities of 1.2 × 10−4 and 2.2 × 10−3 cm2/(Vs), respectively. DTP-BThBBT exhibited ambipolar field-effect characteristics and showed hole and electron mobilities of 1.2 × 10−3 and 5.8 × 10−4 cm2/(Vs), respectively. Bulk heterojunction photovoltaic devices made from blends of the copolymers with 3′-phenyl-3′H-cyclopropa[1,9](C60-Ih)[5,6]fullerene-3′-butanoic acid methyl ester (PCBM) (1:3 weight ratio) exhibited average power conversion efficiencies as high as 1.3% under simulated irradiance of 75 mW/cm2.
Co-reporter:David Y. Liu and John R. Reynolds
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 12) pp:3586
Publication Date(Web):November 22, 2010
DOI:10.1021/am1007744
We report on the electrochemical and capacitive behaviors of poly(2,2-dimethyl-3,4-propylene-dioxythipohene) (PProDOT-Me2) films as polymeric electrodes in Type I electrochemical supercapacitors. The supercapacitor device displays robust capacitive charging/discharging behaviors with specific capacitance of 55 F/g, based on 60 μg of PProDOT-Me2 per electrode, that retains over 85% of its storage capacity after 32 000 redox cycles at 78% depth of discharge. Moreover, an appreciable average energy density of 6 Wh/kg has been calculated for the device, along with well-behaved and rapid capacitive responses to 1.0 V between 5 to 500 mV s−1. Tandem electrochemical supercapacitors were assembled in series, in parallel, and in combinations of the two to widen the operating voltage window and to increase the capacitive currents. Four supercapacitors coupled in series exhibited a 4.0 V charging/discharging window, whereas assembly in parallel displayed a 4-fold increase in capacitance. Combinations of both serial and parallel assembly with six supercapacitors resulted in the extension of voltage to 3 V and a 2-fold increase in capacitive currents. Utilization of bipolar electrodes facilitated the encapsulation of tandem supercapacitors as individual, flexible, and lightweight supercapacitor modules.Keywords: 3,4-propylenedioxythiophene; electroactive conjugated polymer; energy storage; tandem supercapacitor
Co-reporter:Jianguo Mei, Kenneth R. Graham, Romain Stalder and John R. Reynolds
Organic Letters 2010 Volume 12(Issue 4) pp:660-663
Publication Date(Web):January 25, 2010
DOI:10.1021/ol902512x
Isoindigo, as a new electron acceptor unit for organic electronic materials, was integrated into two low-energy gap oligothiophenes. Optical and electrochemical studies of the newly synthesized oligomers demonstrate broad absorption through the visible spectrum, along with appropriate energy levels, as desired for light harvesting donors for organic solar cells when blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM). Molecular heterojunction solar cells were fabricated using these oligomers and exhibit a power conversion efficiency up to 1.76% with a Voc of 0.74 V, Isc of 6.3 mA/cm2 and fill factor of 0.38.
Co-reporter:Frank A. Arroyave and John R. Reynolds
Organic Letters 2010 Volume 12(Issue 6) pp:1328-1331
Publication Date(Web):March 1, 2010
DOI:10.1021/ol100231g
An effective decarboxylative cross-coupling involving a 3,4-dioxypyrrole is reported. Several conjugated oligomers were synthesized in high yields using various aryl bromides. No copper salt or other transmetalating agent was required. The reaction conditions employed displayed relatively low sensitivity toward the presence of water.
Co-reporter:Jegadesan Subbiah, Pierre M. Beaujuge, Kaushik Roy Choudhury, Stefan Ellinger, John R. Reynolds, Franky So
Organic Electronics 2010 Volume 11(Issue 5) pp:955-958
Publication Date(Web):May 2010
DOI:10.1016/j.orgel.2010.02.006
The performance of bulk-heterojunction solar cells fabricated from a donor–acceptor structured polymer designed to exhibit the color green (PGREEN) as the electron-donor, along with [6,6]-phenyl-C71 butyric acid methyl ester (PC70BM) as the electron-acceptor, are demonstrated with power conversion efficiency (PCE) up to 3.2% under air mass 1.5G, 100 mW/cm2. The effects of anode interface layers (PEDOT:PSS, MoO3) and different acceptors (PC60BM, bis-PC60BM, PC70BM) on the cell performance were investigated. We found that the combined effect of PC70BM and a MoO3 anode interlayer exhibits a 69% enhancement in PCE compared to cells with PEDOT:PSS and PC60BM. This enhancement in PCE is attributed to combined effects of improved charge transport and strong light absorption by PC70BM, and efficient hole extraction by the MoO3 interlayer.
Co-reporter:Aubrey L. Dyer, Michael R. Craig, Joseph E. Babiarz, Kelly Kiyak and John R. Reynolds
Macromolecules 2010 Volume 43(Issue 10) pp:4460-4467
Publication Date(Web):April 28, 2010
DOI:10.1021/ma100366y
As the color palette of available solution processable electrochromic polymers expands, there has remained the need for red, orange, and yellow to transmissive switching materials. Here we report on the synthesis and characterization of two such polymers, the orange to transmissive switching (poly{3,4-di(2-ethylhexyloxy)thiophene}) electrochromic polymer-orange (ECP-orange) and the red to transmissive switching processable polymer (poly{3,4-di(2-ethylhexyloxy)thiophene-co-3,4-di(methoxy)thiophene}) electrochromic polymer-red (ECP-red). The ECP-orange has a bandgap of 2.04 eV, an absorption λmax centered at 483 nm, and an E1/2 of 0.37 V versus Ag/Ag+. The electrochromic contrast is 48% T at 483 nm with a time to reach 95% of the full optical contrast of 5.3 s for a film that has an absorbance of 0.98 au at λmax. Because of steric relaxations from the random copolymerization of a branched dialkoxy-substituted thiophene with a dimethoxy-substituted thiophene, the red to transmissive switching ECP-red has a bandgap of 2.00 eV, a λmax red-shifted by 42 to 525 nm, and an E1/2 decreased to 0.21 V versus Ag/Ag+. Additionally, the red polymer has a higher contrast of 60% T and a shorter time to reach 95% of the full optical contrast of 2.3 s. These two reported polymers allow the field of electrochromics to come closer to a full set of fully solution processable materials that yield films whose optical absorption covers the full visible spectrum while switching to a highly transmissive oxidized state as needed for full color displays.
Co-reporter:Jianguo Mei, Brian S. Aitken, Kenneth R. Graham, Kenneth B. Wagener and John R. Reynolds
Macromolecules 2010 Volume 43(Issue 14) pp:5909-5913
Publication Date(Web):June 30, 2010
DOI:10.1021/ma100863h
Co-reporter:Romain Stalder, Jianguo Mei, and John R. Reynolds
Macromolecules 2010 Volume 43(Issue 20) pp:8348-8352
Publication Date(Web):September 22, 2010
DOI:10.1021/ma1018445
Co-reporter:Pierre M. Beaujuge ; Wojciech Pisula ; Hoi Nok Tsao ; Stefan Ellinger ; Klaus Müllen
Journal of the American Chemical Society 2009 Volume 131(Issue 22) pp:7514-7515
Publication Date(Web):May 15, 2009
DOI:10.1021/ja900519k
Four new DTS−BTD copolymers (P1−P4) differing by the concentration of electron-donating and -withdrawing substituents along the backbone have been synthesized and characterized by 2D-WAXS and in bottom-contact FETs. While all copolymers can self-assemble into lamellar superstructures, only P2 and P4 show a propensity to π-stack. P4 exhibits a hole mobility as high as 0.02 cm2 V−1 s−1 in excellent agreement with the close π-stacking and lamellar distances found by structural analysis (0.36 and 1.84 nm, respectively) and absorbs homogenously across the entire visible spectrum as solar cell applications require.
Co-reporter:Ece Unur, Pierre M. Beaujuge, Stefan Ellinger, June-Ho Jung and John R. Reynolds
Chemistry of Materials 2009 Volume 21(Issue 21) pp:5145
Publication Date(Web):October 9, 2009
DOI:10.1021/cm902069k
We introduce the first π-conjugated polymer-based, black-to-transmissive and multicolored switching electrochromic device (ECD) constructed in a Pseudo 3-Electrode Electrochromic Device (P3-ECD) architecture. In this ECD, the non-electrochromic, yet electroactive, polymer poly(3,4-propylenedioxypyrrole-N-propionitrile) (PProDOP-N-EtCN) serves as a counter electrode material. This transmissive polymer helps eliminate the contrast limitations seen in dual polymer ECDs that use combinations of anodically and cathodically coloring polymers. The P3-ECD adds colors by transmitting light through two independently controlled working electrodes (coated with two different electrochromic polymer films) and two counter electrodes (coated with PProDOP-N-EtCN) stacked together with a gel electrolyte. The two cathodically coloring EC polymers that were used in this work are, a diester-substituted poly(3,4-propylenedioxythiophene) (PProDOT-(CH2CO2C12H25)2) for the first one, namely PProDOT-ester, and a donor−acceptor analogue, namely PProDOT-BTD, which consists of a specific alternation of donor and acceptor building units spanning the electron-rich 3,4-ethylenedioxythiophene (EDOT), 2-ethylhexyloxy-substituted 3,4-propylenedioxythiophene ProDOT-(CH2O(2-EtHx))2 and the electron-deficient 2,1,3-benzothiadiazole (BTD). The PProDOT-ester switches from a deep purple (L* = 41 a* = 22 b* = −48) to a highly transmissive gray/blue (L* = 87 a* = −2 b* = −7), while the PProDOT-BTD switches from a deep green (L* = 60, a* = −23, b* = 12) to transmissive sky blue (L* = 84, a* = −4, b* = −6). Utilizing PProDOT-ester and PProDOT-BTD in their neutral form in the P3-ECD yields a deep blue-black with color coordinates of L* = 26 ,a* = −3, b* = −17 switching to a transmissive state with color coordinates of L* = 75, a* = −7, b* = −7. The device has a high Michelson contrast of 0.8 (which can range from 0 to 1). Separate potential control over the electrodes allows color mixing of the polymers in intermediate oxidation states in the P3-ECD. As such, a full palette of colors is accessible through proper choice of EC materials as desired for the construction of multicolored information displays, and in the case of black-to-transmissive electronic paper.
Co-reporter:Robert N. Brookins, Erik Berda and John R. Reynolds
Journal of Materials Chemistry A 2009 vol. 19(Issue 24) pp:4197-4204
Publication Date(Web):11 May 2009
DOI:10.1039/B820002E
Two poly(benzo[1,2-b:4,3-b′]dithiophene)s [PBDTs] with linear and branched substituents have been synthesized as freely soluble polymers using Colon/Kelsey and Suzuki polymerizations (Mn = 6.6–12.7 kDa, DP: 15–29). Polymers with linear substituents show effects due to increased polymer aggregation as evidenced bathochromic spectral bands. The electrochemical results also show the influence of interchain interactions where the aggregate of the linear derivative has oxidative processes at 0.5 V lower potentials than the branched derivative.
Co-reporter:Jonathan R. Sommer, Richard T. Farley, Kenneth R. Graham, Yixing Yang, John R. Reynolds, Jiangeng Xue and Kirk S. Schanze
ACS Applied Materials & Interfaces 2009 Volume 1(Issue 2) pp:274
Publication Date(Web):February 3, 2009
DOI:10.1021/am800236x
The new metalloporphyrin Pt(tptnp), where tptnp = tetraphenyltetranaphtho[2,3]porphyrin, has been prepared and subjected to photophysical and electrooptical device studies. In degassed toluene solution at room temperature Pt(tptnp) features efficient phosphorescence emission with λmax 883 nm with a quantum efficiency of 0.22. The complex has been used as the active phosphor in polymer and organic light-emitting diodes. Polymer light-emitting diodes based on a spin-coated emissive layer consisting of a blend of Pt(tptnp) doped in poly(9-vinylcarbazole) and 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole exhibit near-IR emission with λmax 896 nm, with a maximum external quantum efficiency (EQE) of 0.4% and a maximum radiant emittance of 100 μW/cm2. Organic light-emitting diodes prepared via vapor deposition of all layers and that feature an optimized multilayer hole injection and electron blocking layer heterostructure with an emissive layer consisting of 4,4′-bis(carbazol-9-yl)biphenyl (CBP) doped with Pt(tptnp) exhibit a maximum EQE of 3.8% and a maximum radiant emittance of 1.8 mW/cm2. The polymer and organic light-emitting diodes characterized in this study exhibit record high efficiency for devices that emit in the near-IR at λ >800 nm.Keywords: electrophosphorescence; metalloporphyrin; near-infrared; organic light emitting diodes; polymer light emitting diodes
Co-reporter:Jianguo Mei, Katsu Ogawa, Young-Gi Kim, Nathan C. Heston, Daniel J. Arenas, Zahra Nasrollahi, Tracy D. McCarley, David B. Tanner, John R. Reynolds and Kirk S. Schanze
ACS Applied Materials & Interfaces 2009 Volume 1(Issue 1) pp:150
Publication Date(Web):January 13, 2009
DOI:10.1021/am800104k
We report on two pairs of platinum acetylide based polymers and model oligomers utilizing a 2,1,3-benzothiadiazole (BTD) acceptor moiety flanked on either side by either 2,5-thienyl donor units (Pt2BTD-Th and p-PtBTD-Th) or (3,4-ethylenedioxy)-2,5-thienyl donors (Pt2BTD-EDOT and p-PtBTD-EDOT). Both oligomer/polymer pairs absorb strongly throughout the visible region; however, because the (ethylenedioxy)thiophene moiety is a stronger donor than thiophene, the latter oligomer/polymer pair has a correspondingly lower band gap and, therefore, harvests light more efficiently at longer wavelengths. p-PtBTD-Th exhibits a relatively narrow molecular weight distribution with a number-average molecular weight (Mn) of 22 kDa, while p-PtBTD-EDOT exhibits a comparable Mn of 33 kDa but has a high polydispersity index likely due to aggregation. We provide a complete report of the photophysical and electrochemical characterization of the two oligomer/polymer pairs. The photophysical studies reveal that the materials undergo relatively efficient intersystem crossing. In a discussion of the energetics of photoinduced electron transfer from the platinum polymers to [6,6]-phenyl C61 butyric acid methyl ester (PCBM), it is noted that while the singlet state is quenched efficiently, the triplet state is not quenched, indicating that charge generation in the photovoltaic materials must ensue from the singlet manifold. Finally, organic photovoltaic devices based on blends of p-PtBDT-Th or p-PtBDT-EDOT with PCBM were characterized under monochromatic and simulated solar (AM1.5) illumination. Optimized devices exhibit an open-circuit voltage (Voc) of ∼0.5 V, a short-circuit current density (Isc) of ∼7.2 mA cm−2, and a fill factor of ∼35%, which yields overall power conversion efficiencies of 1.1−1.4%.Keywords: conjugated polymer; fullerene; organometallic polymer; solar cell; triplet state
Co-reporter:Jegadesan Subbiah, Pierre M. Beaujuge, Kaushik Roy Choudhury, Stefan Ellinger, John R. Reynolds and Franky So
ACS Applied Materials & Interfaces 2009 Volume 1(Issue 6) pp:1154
Publication Date(Web):May 28, 2009
DOI:10.1021/am900116p
In this contribution, we report on bulk-heterojunction solar cells using a solution-processable neutral green conjugated copolymer based on 3,4-dioxythiophene and 2,1,3-benzothiadiazole as the donor and [6,6]phenyl-C61 butyric acid methyl ester (PCBM) as the acceptor. We have found that the short-circuit current is very sensitive to the composition of the donor−acceptor blend and it increases with increasing acceptor concentration. The device with a donor−acceptor ratio of 1:8 gives the best performance with a short-circuit current of 5.56 mA/cm2, an open-circuit voltage of 0.77 V, and a power conversion efficiency of 1.9% under AM 1.5 solar illumination. The incident photon-to-current efficiency (IPCE) of the green solar cells shows two bands, one with a maximum of 57% in the UV region corresponding to absorption of PCBM and a second one with a maximum of 42% at longer wavelengths corresponding to the absorption of the green polymer.Keywords: bulk heterojunction; conjugated polymers; donor−acceptor; green solar cell; low band gap
Co-reporter:Svetlana V. Vasilyeva, Ece Unur, Ryan M. Walczak, Evan P. Donoghue, Andrew G. Rinzler and John R. Reynolds
ACS Applied Materials & Interfaces 2009 Volume 1(Issue 10) pp:2288
Publication Date(Web):September 16, 2009
DOI:10.1021/am900435j
Dual polymer absorptive/transmissive electrochromic (EC) window devices have been assembled using the solution-processable and high-EC-contrast polymer PProDOT-(CH2OEtHx)2 as the EC material, along with a non-color-changing electroactive polymer, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), as the counter electrode material. Indium−tin oxide (ITO) and highly transmissive single-walled carbon nanotube (SWNT) film coated glass electrodes are used as electrode substrates. The use of the EC/non-color-changing polymer combination allowed us to construct window devices that rapidly switch between magenta and highly transmissive (>95% T for ITO and ∼79% T for SWNT) states with large optical modulation (>71% ΔT for ITO and 66% ΔT for SWNT). The devices showed effective coloration and bleaching: the lightness parameter (L*) changing from 67 to 95 for ITO (∼50−92 for SWNT), essentially reaching a diffuse white upon oxidation. The color modulates from highly pure magenta with a* = 28 (red hue) and b* = −28 (blue chroma) for ITO (a* = 40 and b* = −36 for SWNT) to nearly colorless with a* = 1 and b* = −1 for ITO (a* = −2 and b* = −3 for SWNT) devices. Increasing the switching voltage from 2.55 V up to 3.5 V resulted in faster SWNT-based window device performance.Keywords: conjugated polymer; electrochromic device; electrochromism; single-walled carbon nanotube films
Co-reporter:Hui Jiang Dr.;Prasad Taranekar Dr.;JohnR. Reynolds Dr. ;KirkS. Schanze Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 24) pp:4300-4316
Publication Date(Web):
DOI:10.1002/anie.200805456
Co-reporter:Hui Jiang Dr.;Prasad Taranekar Dr.;JohnR. Reynolds Dr. ;KirkS. Schanze Dr.
Angewandte Chemie 2009 Volume 121( Issue 24) pp:4364-4381
Publication Date(Web):
DOI:10.1002/ange.200805456
Co-reporter:Pierre M. Beaujuge, Svetlana V. Vasilyeva, Stefan Ellinger, Tracy D. McCarley and John R. Reynolds
Macromolecules 2009 Volume 42(Issue 11) pp:3694-3706
Publication Date(Web):May 13, 2009
DOI:10.1021/ma9002787
The perspective of generating new colors commonly difficult to attain such as cyan blue and greens of various tones and saturations has motivated the design of conjugated polymer finely tuned in their molecular structure to reassemble the optical features desired in the context of non-emissive electrochromic device (ECD) applications. Herein, we report on a series of soluble donor−acceptor (DA) conjugated polymers involving 3,4-dioxythiophenes (DOTs) and 2,1,3-benzothiadiazole (BTD) constructed in combination with unsaturated linkages, namely ethynylene and trans-ethylene, and compare these to their fully polyheterocyclic DA control analogues with careful emphasis on optical, electrochemical, and electrochromic (EC) properties. As confirmed by spectroelectrochemical analysis, ethynylene linkers hindered the formation of a defined bipolaronic transition in the near-IR and were thus found disruptive with respect to the EC potential of their subsequent alternating copolymers. On the other hand, the presence of trans-ethylene spacers incorporated in the DA polymeric backbones allowed further narrowing of the energy gap so that new colors distinct from that exhibited by the control polymers were accessed including saturated green, a complementary color in the realization of polymeric EC displays. Systematic spectroelectrochemical analysis of each novel DA polymer is provided that offers clear evidence of the requirement for conformational freedom and stable quinoidal geometries upon electrochemical oxidation as cathodically coloring electrochromic polymers (ECPs) are switched reversibly to their transmissive doped state.
Co-reporter:Jianguo Mei, Nathan C. Heston, Svetlana V. Vasilyeva and John R. Reynolds
Macromolecules 2009 Volume 42(Issue 5) pp:1482-1487
Publication Date(Web):February 17, 2009
DOI:10.1021/ma802779m
A facile approach to synthesize vinylene-linked donor−acceptor conjugated polymers is reported and can now be considered for general use. This approach led to a low-bandgap, structurally defect-free vinylene-linked benzothiadiazole−thiophene (PTVBT) polymer and its corresponding model compound bisTVBT using a set of three reactions: Heck coupling, Hunsdiecker reaction, and Suzuki coupling reaction. The polymer and the model compound were fully characterized by 1H and 13C NMR, IR, and elemental analysis. GPC revealed that the number-average molecular weights of PTVBT ranged from 20 000 to 31 000 Da and polydispersity indices from 1.7 to 2.4. Thermal analysis demonstrated that the polymer was stable up to 380 °C under nitrogen without decomposition. Spectroelectrochemical results showed the PTVBT had an optical bandgap of 1.5 eV and was both p- and n-type dopable. The energetic positions of the band edges were determined by cyclic voltammetry and differential pulse voltammetry and suggested that the polymer had a HOMO level at 5.2−5.4 eV, as well as a LUMO level at 3.5−3.6 eV, which renders a strong tendency for photoinduced charge transfer to fullerene acceptors. The polymer has been investigated as an electron donor in photovoltaic devices in blends with PCBM ([6,6]-phenyl C61-butyric acid methyl ester) as an electron acceptor. Power conversion efficiencies ∼0.2−0.3% have been obtained with an open-circuit voltage (Voc) of 0.61 V and a short-circuit current density (Isc) of 1.6 mA/cm2. The relatively low conversion efficiencies may result from low content of polymer in the blends and phase separation as revealed by AFM studies.
Co-reporter:Ryan M. Walczak, Robert N. Brookins, Alice M. Savage, Eveline M. van der Aa and John R. Reynolds
Macromolecules 2009 Volume 42(Issue 5) pp:1445-1447
Publication Date(Web):February 16, 2009
DOI:10.1021/ma802462v
Co-reporter:Pierre M. Beaujuge;Stefan Ellinger
Advanced Materials 2008 Volume 20( Issue 14) pp:2772-2776
Publication Date(Web):
DOI:10.1002/adma.200800280
Co-reporter:Ece Unur, June-Ho Jung, Roger J. Mortimer and John R. Reynolds
Chemistry of Materials 2008 Volume 20(Issue 6) pp:2328
Publication Date(Web):February 22, 2008
DOI:10.1021/cm703354q
We report an analytical method which allows the systematic variation of color states of pairs of electrochromic conjugated conducting polymers with simultaneous spectroelectrochemical and colorimetric characterization of the resulting color summation. This method measures colors by transmitting light through two polymer films stacked together in electrolyte and under separate potentiostatic control. The polymers that were used in this work are poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-propylenedioxypyrrole) (PProDOP), and dihexyl-substituted poly(3,4-propylenedioxythiophene) (PProDOT-Hx2). These are all cathodically coloring polymers, PEDOT switching from a transmissive sky blue to a deep blue, PProDOP switching from a highly transmissive gray/blue to a brown and then to an orange, and PProDOT-Hx2 switching from a transmissive sky blue to a purple/magenta color upon reduction. Coupling these polymers logically by the dual-polymer electrochromic film characterization technique led us to obtain new colors which were not observed when these polymers were studied separately. For example, coupling PEDOT and PProDOP films in their neutral state resulted in a new red/brown color (L* = 59, a* = 25, and b* = 50), which is different from the original colors these polymers show in their neutral states, deep blue (L* = 64, a* = −5, and b* = −37) and orange (L* = 76, a* = 31, and b* = 75), respectively. A full palette of colors is accessible by coupling existing electrochromic polymers by this new bipotentiostatic technique.
Co-reporter:A. L. Dyer;C. R. G. Grenier;J. R. Reynolds
Advanced Functional Materials 2007 Volume 17(Issue 9) pp:
Publication Date(Web):27 APR 2007
DOI:10.1002/adfm.200601145
Disubstituted poly(3,4-propylenedioxythiophene)s (PProDOTs) exhibit large electrochromic contrasts in the near infrared (NIR) while showing essentially no color change in the visible region when incorporated into a reflective device platform. The source of this is attributed to a conductive front that propagates through the insulating polymer film, extending from the polymer/electrode interface to the top of the polymer film. A utility of the large contrasts seen in the NIR region is demonstrated with application of the device as an electrochromic variable optical attenuator modulating fiber-optic signals for optical telecommunications. With bis(ethylhexyloxy)-substituted PProDOT as the active electrochromic polymer in the device, an optical attenuation of 11 dB at the telecommunications wavelengths of 1.31 and 1.55 μm is achieved with only a 0.1–0.2 dB optical loss in the bleached state. Other favorable properties include optical memory in the absorbing state, switching speeds of under 1 s, a low operating voltage of ±1.2 V, and an improved processability that allows spray-casting from organic solvents.
Co-reporter:Timothy T. Steckler, Khalil A. Abboud, Matt Craps, Andrew G. Rinzler and John R. Reynolds
Chemical Communications 2007 (Issue 46) pp:4904-4906
Publication Date(Web):05 Oct 2007
DOI:10.1039/B709672K
An electron donor/acceptor π-conjugated polymer composed of a bi-EDOT and benzobis(thiadiazole) repeat unit exhibits two reductions with a band gap ranging from ∼0.5 to 0.8 eV depending on the method of band gap determination.
Co-reporter:Christophe R. G. Grenier;Wojciech Pisula Dr.;Thomas J. Joncheray;Klaus Müllen Dr.;John R. Reynolds Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 5) pp:
Publication Date(Web):7 DEC 2006
DOI:10.1002/anie.200602894
Colored ribbons: The soluble, electron-rich conjugated title polymer (alkyl=dodecyl) with a regiosymmetric structure was synthesized by Grignard metathesis. The polymer displays strong thermochromism in solution. AFM images of spin-coated films show the formation of nanoribbons, and 2D-WAXS analysis reveals 2D order in the bulk material (see picture). The polymer is thus a promising candidate for device applications.
Co-reporter:Christophe R. G. Grenier;Wojciech Pisula Dr.;Thomas J. Joncheray;Klaus Müllen Dr.;John R. Reynolds Dr.
Angewandte Chemie 2007 Volume 119(Issue 5) pp:
Publication Date(Web):7 DEC 2006
DOI:10.1002/ange.200602894
Farbige Bänder: Das lösliche, elektronenreiche konjugierte Titelpolymer (Alkyl=Dodecyl) mit regiosymmetrischer Struktur wurde durch Grignard-Metathese erhalten. Das Polymer ist in Lösung ausgeprägt thermochrom. Die AFM-Untersuchung schleuderbeschichteter Filme ergibt die Bildung von Nanobändern, und nach einer 2D-WAXS-Analyse liegt eine 2D-Ordnung im Material vor (siehe Bild). Das Polymer sollte sich daher für den Bau von Funktionseinheiten eignen.
Co-reporter:R. M. Walczak;J. R. Reynolds
Advanced Materials 2006 Volume 18(Issue 9) pp:1121-1131
Publication Date(Web):24 APR 2006
DOI:10.1002/adma.200502312
The poly(3,4-dioxypyrrole) (PXDOP) family of conducting and electroactive polymers has now been developed to the point that multiple synthetic routes allow many functionalized polymers with controllable optoelectronic and redox properties. These properties, which include high conductivity, multicolor cathodic and anodic electrochromism, and rapid redox switching, allow these materials to be used in a variety of applications that potentially include conducting coatings, electrochromic windows and displays, chemical sensors, bioactive materials, and mechanical actuators. Surprisingly, the scientific literature published on the PXDOP derivatives has been isolated and sparse compared to that of other conducting polymers. This report will highlight the synthesis and materials properties of PXDOPs and show how these powerful materials fit into the frontier of conducting polymers research.
Co-reporter:Fengqi Guo, Young-Gi Kim, John R. Reynolds and Kirk S. Schanze
Chemical Communications 2006 (Issue 17) pp:1887-1889
Publication Date(Web):21 Mar 2006
DOI:10.1039/B516086C
Relatively efficient photovoltaic devices were fabricated using blends of a phosphorescent platinum–acetylide polymer and a fullerene (PCBM); involvement of the triplet excited state of the platinum–acetylide polymer in photoinduced charge transfer is believed to contribute to the device efficiency.
Co-reporter:A. A. Argun;M. Berard;P.-H. Aubert;J. R. Reynolds
Advanced Materials 2005 Volume 17(Issue 4) pp:
Publication Date(Web):24 JAN 2005
DOI:10.1002/adma.200401353
Patterned electrodes on porous substrates, where the contacts to address these electrodes are hidden on the back of the substrates are described. To demonstrate the applicability of this method in fabricating organic electronic devices, a reflective-type polymer electrochromic device is constructed. A 7-pixel numerical-display device, showing the number “6” in the Figure, benefits from the color contrast between gold and a poly(3,4-propylenedioxythiophene) derivative.
Co-reporter:Avni A. Argun and John R. Reynolds
Journal of Materials Chemistry A 2005 vol. 15(Issue 18) pp:1793-1800
Publication Date(Web):04 Mar 2005
DOI:10.1039/B417607C
We have applied the line patterning method, which involves printing of patterns on a plastic or paper substrate using a commercial printer followed by coating of the non-printed areas by a conductive polymer, or metal conductor, to build laterally configured polymer and metallic interdigitated electrodes (IDEs) for electrochromic devices (ECDs). Selective deposition of transparent poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonate)
(PEDOT–PSS) or electroless gold films resulted in lateral electrode resolution values of ∼30 µm as determined by optical microscopy. These ECDs comprise complementary colored, dioxythiophene based electrochromic polymers deposited on alternating fingers of gold coated IDEs and a viscous electrolyte layer to enable ion transport between the polymers. The devices are switched by stepping the applied voltage between −1.2 V to +1.2 V and pass a maximum of 1.3 mA cm−2 and a switching charge of 1.2 mC cm−2 in ∼3 s to switch the device from a highly reflective gold state to an absorptive blue state. Three IDEs with different anode to cathode distances have been line patterned via electroless gold deposition. Electrochromic switching kinetics of 2-lane, 4-lane, and 6-lane ECDs have been studied by applying potential steps from −1.0 V to +0.8 V and monitoring the reflectance change as a function of time. The switching times to reach 85% of the full contrast are 4.3 s, 1.5 s, and 0.8 s for the 2-lane, 4-lane, and 6-lane devices, respectively. The extent of interdigitation noticeably improves the switching performance of lateral ECDs due to shorter diffusion distances for dopant ions and minimal electrolyte resistance.
Co-reporter:Barry C. Thompson;Luis G. Madrigal;Mauricio R. Pinto;Tae-Sik Kang;Kirk S. Schanze
Journal of Polymer Science Part A: Polymer Chemistry 2005 Volume 43(Issue 7) pp:1417-1431
Publication Date(Web):15 FEB 2005
DOI:10.1002/pola.20578
We report a comparative study of two organic soluble, vinylene-based, alternating donor–acceptor copolymers with 1,4-(2,5-dihexadecyloxyphenylene) as the donor; the acceptor is either a 2,5-linked pyridine or a 5,8-linked 2,3-diphenylpyrido[3,4-b]pyrazine. The polymers are synthesized via a Heck coupling methodology from a dihalo monomer and a divinyl monomer to yield number-average molecular weights of 16,000 g/mol for the pyridine polymer (PPyrPV) and 6500 g/mol for the pyridopyrazine polymer (PPyrPyrPV), with high solubility in common chlorinated solvents and lower solubility in less polar solvents (e.g., tetrahydrofuran). Thin-film measurements show band gaps of 2.2 and 1.8 eV for PPyrPV and PPyrPyrPV, respectively. Both polymers exhibit photoluminescence in solution and in the solid state and exhibit electroluminescence when incorporated into light-emitting diodes. In this case, a broad red emission centered at 690 nm for PPyrPV and a near-infrared emission centered at 800 nm for PPyrPyrPV have been observed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1417–1431, 2005
Co-reporter:A.A. Argun;A. Cirpan;J.R. Reynolds
Advanced Materials 2003 Volume 15(Issue 16) pp:
Publication Date(Web):18 AUG 2003
DOI:10.1002/adma.200305038
Co-reporter:T.-S. Kang;B.S. Harrison;T.J. Foley;A.S. Knefely;J.M. Boncella;J.R. Reynolds;K.S. Schanze
Advanced Materials 2003 Volume 15(Issue 13) pp:
Publication Date(Web):30 JUN 2003
DOI:10.1002/adma.200304692
Co-reporter:S. Alkan;C.A. Cutler;J.R. Reynolds
Advanced Functional Materials 2003 Volume 13(Issue 4) pp:
Publication Date(Web):11 APR 2003
DOI:10.1002/adfm.200304307
Electrochemical polymerization in the strong Lewis acid, boron trifluoride ethylether (BFEE), has been used to prepare electrochromic polythiophene (PTh) and its derivatives: poly(3-methylthiophene) (PMeTh), poly(3-bromothiophene) (PBrTh), and poly(3,4-dibromothiophene) (PDBrTh). The polymerization processes and properties of the resultant films are compared, where possible, to those carried out in traditional organic electrochemical solvents. The polymerization of these high oxidation potential thiophene monomers in BFEE yielded good-quality, homogenous, and smooth electroactive and electrochromic films that could be repeatedly switched in common electrochemical solvents up to 240, 1380, 560, and 420 cycles for PTh, PMeTh, PBrTh, and PDBrTh, respectively, for 50 % retention of electroactivity. A colorimetric study of these films showed distinctive color changes between red and blue as they were switched between reduced and oxidized states. These findings allow the use of commercially available high oxidation potential thiophene monomers to provide electrochromic polymers, avoiding the use of other custom-synthesized monomers.
Co-reporter:T.-S. Kang;B.S. Harrison;M. Bouguettaya;T.J. Foley;J.M. Boncella;K.S. Schanze;J.R. Reynolds
Advanced Functional Materials 2003 Volume 13(Issue 3) pp:
Publication Date(Web):7 MAR 2003
DOI:10.1002/adfm.200390031
Near-infrared-emitting electroluminescent (EL) devices using blue-light-emitting polymers blended with the Yb complexes Yb(DBM)3phen (DBM = dibenzoylmethane), Yb(DNM)3phen (DNM = dinaphthoylmethane), and Yb(TPP)L(OEt) (L(OEt) = [(C5H5)Co{P(O)Et2}3]–) have been studied. EL devices composed of Yb(DNM)3phen blended with PPP-OR11 showed enhanced near-IR output at 977 nm when compared to those fabricated with Yb(DBM)3phen/PPP-OR11 blends. The maximum near-IR external efficiencies of the devices with Yb(DBM)3phen and Yb(DNM)3phen are, respectively, 7 × 10–5 (at 6 V and at 0.81 mA mm–2) and 4 × 10–4 (at 7 V, and 0.74 mA mm–2). The optimal blend composition for EL device performance consisted of PPP-OR11 blended with 10–20 mol-% Yb(DNM)3phen. A device fabricated using Yb-(TPP)L(OEt)/PPP-OR11 showed significantly enhanced near-IR output efficiency, and future efforts will focus on devices fabricated using porphyrin-based materials.
Co-reporter:C.J. DuBois;J.R. Reynolds
Advanced Materials 2002 Volume 14(Issue 24) pp:
Publication Date(Web):23 DEC 2002
DOI:10.1002/adma.200290016
Co-reporter:B.D. Reeves;B.C. Thompson;K.A. Abboud;B.E. Smart;J.R. Reynolds
Advanced Materials 2002 Volume 14(Issue 10) pp:
Publication Date(Web):17 MAY 2002
DOI:10.1002/1521-4095(20020517)14:10<717::AID-ADMA717>3.0.CO;2-D
Co-reporter:C.A. Cutler;M. Bouguettaya;J.R. Reynolds
Advanced Materials 2002 Volume 14(Issue 9) pp:
Publication Date(Web):6 MAY 2002
DOI:10.1002/1521-4095(20020503)14:9<684::AID-ADMA684>3.0.CO;2-7
Co-reporter:Kyukwan Zong, Luis Madrigal, L. “Bert” Groenendaal and John R. Reynolds
Chemical Communications 2002 (Issue 21) pp:2498-2499
Publication Date(Web):26 Sep 2002
DOI:10.1039/B205907J
3,4-Alkylenedioxy ring functionalized thiophenes (XDOT’s) have been synthesized by double Mitsunobu reactions to yield precursors to monomers for conjugated and electrically conducting polymers, including the commercially important 3,4-ethylenedioxythiophene (EDOT).
Co-reporter:Carleton L. Gaupp;Dean M. Welsh
Macromolecular Rapid Communications 2002 Volume 23(Issue 15) pp:885-889
Publication Date(Web):5 NOV 2002
DOI:10.1002/1521-3927(20021001)23:15<885::AID-MARC885>3.0.CO;2-X
The synthesis and electrochemical polymerization of 3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]dioxepine (ProDOT-Et2) was performed resulting in a stable electrochromic polymer capable of switching between an absorbing blue neutral state and a highly transmissive sky-blue oxidized state in sub-second time frames. High optical switching contrast ratios (up to 75% at λmax) and high composite coloration efficiencies (505 cm2/C) were measured.
Co-reporter:Jean-Michel Pernaut, Kyukwan Zong, John R. Reynolds
Synthetic Metals 2002 Volume 130(Issue 1) pp:1-8
Publication Date(Web):31 August 2002
DOI:10.1016/S0379-6779(02)00047-4
A new fused tetramethyl substituted 14-crown-4 3,4-pyrrole (TMC-DOP) has been polymerized and the redox switching properties of the resultant polymer investigated such as its possibility of lithium ion sensing. Especially, interesting redox properties have been obtained when the polymerization is carried out galvanostatically at a low current density of less than 50 μA cm−2. In this instance, two redox processes labeled α (E0∼−0.65 V) and β (E0∼+0.15 V) are reproducibly observed. A cation sensing study revealed a clear cyclic voltammetric response due to a β→α process conversion with a slightly higher sensitivity for lithium ions when compared to sodium ions. The poly(TMC-DOP) exhibited a strong electrochromic response, changing from yellow at −0.7 V to highly transmissive and color neutral at +0.2 V indicating possible ionochromic behavior upon optimization of the electrochemical detection load.
Co-reporter:I. Schwendeman;J. Hwang;D. M. Welsh;D. B. Tanner;J. R. Reynolds
Advanced Materials 2001 Volume 13(Issue 9) pp:
Publication Date(Web):2 MAY 2001
DOI:10.1002/1521-4095(200105)13:9<634::AID-ADMA634>3.0.CO;2-3
Co-reporter:Gürsel Sönmez, Philippe Schottland, Kyukwan Zong and John R. Reynolds
Journal of Materials Chemistry A 2001 vol. 11(Issue 2) pp:289-294
Publication Date(Web):01 Dec 2000
DOI:10.1039/B007976F
Poly[(3,4-ethylenedioxy)pyrrole-2,5-diyl]
(PEDOP) and poly[(3,4-propylenedioxy)pyrrole-2,5-diyl]
(PProDOP) were synthesized by in situ chemical polymerization yielding highly transmissive, conductive and electroactive thin films. PProDOP coatings exhibit a surface resistivity of 16 kΩ □−1 at 60% and 58 kΩ □−1 at 99.9% relative luminance (measured by colorimetry). Many factors were found to impact the formation of the films, including pH, temperature, nature of the dopant ion, and nature of the oxidizing agent. The best combination of dopant ion–oxidant was obtained for anthraquinone-2-sulfonic acid (AQSA)–copper chloride which yielded the most conductive films (σ = 10 S cm−1). A doping level of about 25–30% was determined by X-ray photoelectron spectroscopy (XPS) for PEDOP and PProDOP films. Scanning electron microscopy (SEM) and profilometry indicate homogenous film deposition with total surface coverage attained in films as thin as 40–70 nm with a compact and smooth morphology. Spectroelectrochemistry of chemically prepared (oxidized) and subsequently electrochemically reduced PProDOP films showed the disappearance of the π–π* transition, evident as two maxima at 485 nm and 518 nm upon electrochemical doping. The band gap, measured as the onset of the π–π* transition was 2.2 eV. Since the oxidation potential of EDOP is relatively low (+0.6 V vs. Ag/Ag+), it was possible to obtain conducting films of PEDOP using air as the oxidizing agent for the polymerization. This result is of particular importance since very few conducting polymers can be obtained by such an environmentally friendly process.
Co-reporter:Fernando Larmat, Jadwiga Soloducho, Alan R Katritzky, John R Reynolds
Synthetic Metals 2001 Volume 124(2–3) pp:329-336
Publication Date(Web):22 October 2001
DOI:10.1016/S0379-6779(01)00380-0
The electrochemical and electronic properties, as well as the redox induced ion and charge transport mechanism in poly[1,4-bis(pyrrol-2-yl)phenylene] (PBPyP), have been studied by electrochemical, optical and electron spin resonance (ESR) spectroscopies, along with electrogravimetric techniques. PBPyP films are obtained by electropolymerization in several solvent/electrolyte systems. Due to the electron-rich and three-ring nature of 1,4-bis(pyrrol-2-yl)benzene (BPyB), polymerization occurs at low potentials (ca. 0.3 V versus Ag/Ag+), and the resulting polymers are stable to multiple redox switching. The ESR and optical spectra of the polymer are consistent with the sequential formation of cation-radical and diamagnetic charge-carriers during the doping process. These results fit the classical polaron/bipolaron model, though the presence of π-dimers cannot be ruled out. The evolution of the ESR signal during gradual oxidation of the polymer indicates that radical-cations (polarons) are intermediates in the redox mechanism even though the individual redox processes from neutral to polaron and from polaron to bipolaron cannot be observed in the cyclic voltammograms of the polymer. Electrogravimetric studies using the electrochemical quartz microbalance (ECQM) combined with conductance spectra indicates that the electrolyte anions are the dominant mobile species during the redox switching of the polymer.
Co-reporter:Jennifer A. Irvin;Irina Schwendeman;Youngkwan Lee;Khalil A. Abboud
Journal of Polymer Science Part A: Polymer Chemistry 2001 Volume 39(Issue 13) pp:2164-2178
Publication Date(Web):9 MAY 2001
DOI:10.1002/pola.1193
Monomers derived from 3,4-ethylenedioxythiophene and phenylenes with branched or oligomeric ether dialkoxy substituents were prepared with the Negishi coupling technique. Electrooxidative polymerization led to the corresponding dialkoxy-substituted 3,4-ethylenedioxythiophene–phenylene polymers, with extremely low oxidation potentials (E1/2,p = −0.16 to −0.50 V vs Ag/Ag+) due to the highly electron-rich nature of these materials. The polymers were electrochromic, reversibly switching from red to blue upon oxidation, with bandgaps at about 2 eV. The electrochemical behavior of the oligomeric ether-substituted polymer was investigated in the presence of different metal ions. Films of the polymer exhibited electrochemical recognition for several alkali and alkaline-earth cations with selectivity in the order Li+ > Ba2+ > Na+ > Mg2+. Cyclic voltammetry showed a decrease in the oxidation potential and an improvement in the definition of the voltammetric response, as well as an increase in the overall electroactivity of the polymer films when the concentration of the cations in the medium was increased. These results are discussed in terms of the electrostatic interactions between the complexed cation and the redox center, as well as the diffusion of the ionic species into the polymer matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2164–2178, 2001
Co-reporter:J. R. Reynolds;A. J. Epstein
Advanced Materials 2000 Volume 12(Issue 21) pp:
Publication Date(Web):3 NOV 2000
DOI:10.1002/1521-4095(200011)12:21<1565::AID-ADMA1565>3.0.CO;2-7
Co-reporter:Dinesh G. (Dan) Patel, Kenneth R. Graham and John R. Reynolds
Journal of Materials Chemistry A 2012 - vol. 22(Issue 7) pp:NaN3014-3014
Publication Date(Web):2012/01/03
DOI:10.1039/C2JM14591J
We report on the synthesis of a polyfluorene derivative, PFO(X), with furan pendant groups capable of Diels–Alder crosslinking with a maleimide containing small molecule passive crosslinker (PC) and a maleimide containing red emitting donor–acceptor–donor dopant molecule, bE-BTD(X). It was initially intended that a blend of these three components would afford a system where the dopant concentration could be increased to the point where complete energy transfer from the host polymer to the emissive dopant would be achieved. Because such systems often suffer from quenching and shifts in emission maxima indicative of emitter aggregation, it was hypothesized that crosslinking the emissive dopant with the host polymer would lead to de-aggregation of the dopant emitter. In thin films of PFO(X) and bE-BTD(X), a 16 nm bathochromic shift is observed in the emission maximum when the dopant concentration is increased from 1% to 8%, suggesting that the dopant is aggregating. In similar films where PC is included and the film is heated to affect crosslinking, a comparable 16 nm shift in the emission maximum is observed indicating that aggregation is still occurring and not affected by the heating step. Similar decreases in luminance are observed independent of whether the heating step is included. Not unexpectedly, however, crosslinking does afford an insoluble network that allows for the subsequent solution deposition of additional layers. When an electron transport layer (ETL) is used in PFO(X)/PC devices, increases of 190% and 490% are observed in luminance and luminous efficiency, respectively, relative to devices without an ETL indicating that this Diels–Alder crosslinkable system is amenable to multilayer deposition by solution methods. When bE-BTD(X) is included as the dopant emitter, similar increases in luminance and luminous efficiency are observed with the ETL included compared to devices where this layer is omitted.
Co-reporter:Xuan Zhang, Timothy T. Steckler, Raghunath R. Dasari, Shino Ohira, William J. Potscavage, Shree Prakash Tiwari, Séverine Coppée, Stefan Ellinger, Stephen Barlow, Jean-Luc Brédas, Bernard Kippelen, John R. Reynolds and Seth R. Marder
Journal of Materials Chemistry A 2010 - vol. 20(Issue 1) pp:NaN134-134
Publication Date(Web):2009/11/16
DOI:10.1039/B915940A
A series of highly soluble donor–acceptor (D–A) copolymers containing N-(3,4,5-tri-n-decyloxyphenyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP) or N-(2-decyltetradecyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP′) as donor and three different acceptors, 4,7-dithien-2-yl-[2,1,3]-benzothiadiazole, 4,9-dithien-2-yl-6,7-di-n-hexyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline and 4,8-dithien-2-yl-2λ4δ2-benzo[1,2-c;4,5-c′]bis[1,2,5]thiadiazole (BThX, X = BTD, TQHx2, BBT, respectively) were synthesized by Stille coupling polymerizations. The optical and electrochemical properties of these copolymers were investigated, along with their use in field-effect transistors and photovoltaic devices. The band gaps (eV) estimated from UV-vis-NIR spectra and electrochemical measurements of the copolymers varied from ca. 1.5–0.5 eV, and were consistent with quantum-chemical estimates extrapolated using density functional theory. Oxidative and reductive spectroelectrochemistry of the copolymers indicated they can be both p-doped and n-doped, and three to four differently colored redox states of the polymers can be accessed through electrochemical oxidation or reduction. The DTP-BThBTD and DTP-BThTQHx2 copolymers exhibited average field-effect hole mobilities of 1.2 × 10−4 and 2.2 × 10−3 cm2/(Vs), respectively. DTP-BThBBT exhibited ambipolar field-effect characteristics and showed hole and electron mobilities of 1.2 × 10−3 and 5.8 × 10−4 cm2/(Vs), respectively. Bulk heterojunction photovoltaic devices made from blends of the copolymers with 3′-phenyl-3′H-cyclopropa[1,9](C60-Ih)[5,6]fullerene-3′-butanoic acid methyl ester (PCBM) (1:3 weight ratio) exhibited average power conversion efficiencies as high as 1.3% under simulated irradiance of 75 mW/cm2.
Co-reporter:Robert N. Brookins, Erik Berda and John R. Reynolds
Journal of Materials Chemistry A 2009 - vol. 19(Issue 24) pp:NaN4204-4204
Publication Date(Web):2009/05/11
DOI:10.1039/B820002E
Two poly(benzo[1,2-b:4,3-b′]dithiophene)s [PBDTs] with linear and branched substituents have been synthesized as freely soluble polymers using Colon/Kelsey and Suzuki polymerizations (Mn = 6.6–12.7 kDa, DP: 15–29). Polymers with linear substituents show effects due to increased polymer aggregation as evidenced bathochromic spectral bands. The electrochemical results also show the influence of interchain interactions where the aggregate of the linear derivative has oxidative processes at 0.5 V lower potentials than the branched derivative.
Co-reporter:Unsal Koldemir, Kenneth R. Graham, Danielle H. Salazar, Tracy D. McCarley and John R. Reynolds
Journal of Materials Chemistry A 2011 - vol. 21(Issue 18) pp:NaN6482-6482
Publication Date(Web):2011/03/29
DOI:10.1039/C1JM10345H
We demonstrate the ability of a new alternating polyfluorene (APFO) type polymer employing dialkoxythiophene moieties to operate efficiently as both an electrochromic (EC) and electroluminescent (EL) material, thereby providing for incorporation into a dual EC/EL device. In addition, the new APFO type polymer was blended with PC[70]BM in a bulk heterojunction photovoltaic cell resulting in a power conversion efficiency of 1.66% with a high open circuit voltage of 0.87 volts.
Co-reporter:Timothy T. Steckler, Khalil A. Abboud, Matt Craps, Andrew G. Rinzler and John R. Reynolds
Chemical Communications 2007(Issue 46) pp:NaN4906-4906
Publication Date(Web):2007/10/05
DOI:10.1039/B709672K
An electron donor/acceptor π-conjugated polymer composed of a bi-EDOT and benzobis(thiadiazole) repeat unit exhibits two reductions with a band gap ranging from ∼0.5 to 0.8 eV depending on the method of band gap determination.
![2H-Indol-2-one, 6-bromo-3-[6-bromo-1-(2-ethylhexyl)-1,2-dihydro-2-oxo-3H-indol-3-ylidene]-1-(2-ethylhexyl)-1,3-dihydro-, (3E)-](/data/chemimg/101200/1429306-67-1.png)
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![PHOSPHONIC ACID, [5-(TRIMETHYLSTANNYL)-2-THIENYL]-, DIETHYL ESTER](http://img.cochemist.com/ccimg/671200/671190-59-3.png)
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rene-2,7-diyl)-1,4-phenylene]](/data/chemimg/3109700/220797-16-0.png)
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rene-2,7-diyl)-1,4-phenylene]](/data/chemimg/3109700/220797-16-0_b.png)
