Co-reporter:Wenhan He, Maksim Y. Livshits, Diane A. Dickie, Zhen Zhang, Luis E. Mejiaortega, Jeffrey J. Rack, Qin Wu, and Yang Qin
Journal of the American Chemical Society October 11, 2017 Volume 139(Issue 40) pp:14109-14109
Publication Date(Web):July 21, 2017
DOI:10.1021/jacs.7b05801
We report the synthesis, characterization, and detailed comparison of a series of novel Pt-bisacetylide containing conjugated small molecules possessing an unconventional “roller-wheel” shaped structure that is distinctly different from the “dumbbell” designs in traditional Pt-bisacetylide containing conjugated polymers and small molecules. The relationships between the chemical nature and length of the “rollers” and the electronic and physical properties of the materials are carefully studied by steady-state spectroscopy, cyclic voltammetry, differential scanning calorimetry, single-crystal X-ray diffraction, transient absorption spectroscopy, theoretical calculation, and device application. It was revealed that if the roller are long enough, these molecules can “slip-stack” in the solid state, leading to high crystallinity and charge mobility. Organic solar cells were fabricated and showed power conversion efficiencies up to 5.9%, out-performing all existing Pt-containing materials. The device performance was also found to be sensitive to optimization conditions and blend morphologies, which are a result of the intricate interplay among materials crystallinity, phase separation, and the relative positions of the lowest singlet and triplet excited states.
Co-reporter:Keda Hu, Zhen Zhang, James Burke, and Yang Qin
Journal of the American Chemical Society August 16, 2017 Volume 139(Issue 32) pp:11004-11004
Publication Date(Web):July 26, 2017
DOI:10.1021/jacs.7b05682
We report the synthesis and characterization of a novel series of main-chain boron-containing conjugated polymers (CPs), boron “doped” polyacetylenes (BPAs), which represent the first examples of main-chain boron-containing CPs without aromatic moieties within the polymer backbone, potentially enhancing electronic delocalization along the main-chain. These polymers are characterized by NMR, absorption and emission spectroscopy, cyclic voltammetry, theoretical calculation, and fluoride titration experiments, providing detailed understanding of the effects from different cross-conjugated side-chains on the physical and electronic properties of this new class of boron-containing polymers.
Co-reporter:Wenhan He, Maksim Y. Livshits, Diane A. Dickie, Jianzhong Yang, Rachel Quinnett, Jeffrey J. Rack, Qin Wu and Yang Qin
Chemical Science 2016 vol. 7(Issue 9) pp:5798-5804
Publication Date(Web):23 May 2016
DOI:10.1039/C6SC00513F
A novel Pt-bisacetylide small molecule (Pt-SM) featuring “roller-wheel” geometry was synthesized and characterized. When compared with conventional Pt-containing polymers and small molecules having “dumbbell” shaped structures, Pt-SM displays enhanced crystallinity and intermolecular π–π interactions, as well as favorable panchromatic absorption behaviors. Organic solar cells (OSCs) employing Pt-SM achieve power conversion efficiencies (PCEs) up to 5.9%, the highest reported so far for Pt-containing polymers and small molecules.
Co-reporter:Jianzhong Yang, Zhen Zhang, and Yang Qin
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 34) pp:22392
Publication Date(Web):August 12, 2016
DOI:10.1021/acsami.6b06365
The synthesis and characterization of a molecular tetrapod, SFBTD, featuring a tetraphenylsilane center and four identical conjugated arms, which structurally resembles breakwaters in common wave-reducing shore constructions, are reported. Cyclic voltammetry reveals that SFBTD has a medium band gap of ca. 2.0 eV and a low-lying HOMO energy level at ca. −5.2 eV. Absorption spectroscopy, X-ray diffraction, and differential scanning calorimetry experiments reveal a low degree of crystallinity in this compound and slow crystallization kinetics. Bulk heterojunction organic photovoltaics (OPVs) employing SFBTD and fullerene derivatives exhibit power conversion efficiencies (PCEs) up to 1.05% and open-circuit voltage (VOC) values as high as 1.02 V. To the best of our knowledge, this is the highest PCE obtained for OPVs employing molecular tetrapods as donor materials. These devices are relatively thermally stable due to the known ability of breakwater tetrapods to interlock, preventing dislodging and sliding. The lack of favorable phase separations and low hole mobilities of the blend films are the major factors limiting the device performance. Ternary blend devices by the addition of three low band gap poly(thienylene vinylene) (PTV) derivatives were fabricated and tested. We found that the added PTVs acted to be either the major hole conductor or a competing hole conduction channel depending on the HOMO level positions relative to that of SFBTD. Some of the ternary OPV devices out-performed the corresponding binary counterparts employing SFBTD or PTVs alone, suggesting cooperative effects in the ternary systems.Keywords: morphology; organic photovoltaic; small molecule; ternary blend; tetrapod
Co-reporter:Keda Hu
Journal of Polymer Science Part A: Polymer Chemistry 2016 Volume 54( Issue 10) pp:1391-1395
Publication Date(Web):
DOI:10.1002/pola.27989
ABSTRACT
We report the synthesis and characterization of a unique class of conjugated polymers, polytriacetyelenes (PTAs), from a set of trans-enediyne (EDY) monomers bearing alkyl and aromatic substituents. Two different methods, i.e., Glaser-Hay coupling and Pd-catalyzed oxidative coupling, were employed depending on the nature of the side-chains. Our methodology is highly versatile in that it allows direct attachment of aromatic substituents to the PTA main-chains, allowing enhanced tunability in polymer electronic properties, which has not been achievable through previously reported methods. The newly synthesized PTAs displayed strong ability of quenching the fluorescence of poly(3-hexylthiophene) (P3HT), a prototypical conjugated polymer in organic solar cells, indicating possible applications of these PTAs in optoelectronic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1391-1395
Co-reporter:Zhen Zhang and Yang Qin
Macromolecules 2016 Volume 49(Issue 9) pp:3318-3327
Publication Date(Web):April 29, 2016
DOI:10.1021/acs.macromol.6b00502
Poly(thienylene vinylene)s (PTVs) are a unique class of low bandgap conjugated polymers that have received relatively little attention in organic electronic applications due to the limitations in conventional synthetic methodologies that are not capable to produce PTV structures beyond the rudimentary forms. We report here facile synthetic methods, combining acyclic diene metathesis (ADMET) and postpolymerization modification reactions, toward a series of structurally diverse PTVs. Specifically, halogen substituents including F, Cl, Br, and I, and conjugated thienyl groups bearing different substituents, have been installed onto every thiophene unit along the PTV backbones. While halogen substitution lowers both the HOMO and LUMO energy levels of the polymers, the overall optical properties are similar to the conventional unsubstituted PTVs. On the other hand, with increasing sizes of halogen atoms, the polymer crystallinity decreases caused by steric hindrance induced main-chain nonplanarity as suggested by density functional theory (DFT) calculations and confirmed by X-ray diffraction (XRD) and absorption measurements. With the cross-conjugated thienyl side-chains, the PTV polymers are all amorphous due to the large dihedral angles between the main-chain and side-chain thienyl rings. However, with strongly electron-withdrawing groups attached on the side-chain thiophene rings, new electronic transitions located at lower energies are observed, which have never been observed in PTVs and are assigned to main-chain to side-chain intramolecular charge transfer (ICTs) transitions. Such ICT transitions can potentially alter the PTV excited states ordering and dynamics, as evidenced by the appearance of fluorescence in one of the cross-conjugated PTVs bearing strong electron-withdrawing cyanoester vinylene groups. Applications of these new PTVs in bulk heterojunction (BHJ) organic solar cells (OSCs) have been attempted, and preliminary results showed much improved performances over devices using conventional PTVs, especially for those applying the cross-conjugated PTVs. Our methodologies are highly versatile in preparing PTVs with systematically varied structures that for the first time provide means to study and gain better understandings on the structure–property relationships of this unique class of materials and to potentially generate novel polymers tailor-designed for specific electronic applications.
Co-reporter:Jianzhong Yang, Wenhan He, Kimberly Denman, Ying-Bing Jiang and Yang Qin
Journal of Materials Chemistry A 2015 vol. 3(Issue 5) pp:2108-2119
Publication Date(Web):03 Dec 2014
DOI:10.1039/C4TA05405A
We report the synthesis and characterization of a tetrapodal breakwater-like small molecule, SO, containing a tetraphenylsilane core and four cyanoester functionalized terthiophene arms. SO possesses a deep lying HOMO energy level of −5.2 eV and a narrow bandgap of 1.9 eV. Absorption, X-ray scattering and differential scanning calorimetry (DSC) measurements indicate crystalline nature of this compound but very slow crystallization kinetics. Solar cells employing SO and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated and evaluated. Relatively low performance was obtained mainly due to the lack of optimal phase separation under various processing conditions including thermal annealing, slow-cooling and solvent annealing. Addition of poly(thienylene vinylene) (PTV), poly(3-hexylthiophene) (P3HT) and a platinum-containing low bandgap conjugated polymer Pt–BODIPY, into the SO/PCBM blend was found to induce device favorable phase separation and the polymers were found to act as the primary hole conductor. Such ternary blend devices showed cooperatively improved performances over binary devices employing either SO or the individual conjugated polymer alone.
Co-reporter:Zhen Zhang and Yang Qin
ACS Macro Letters 2015 Volume 4(Issue 7) pp:679
Publication Date(Web):June 10, 2015
DOI:10.1021/acsmacrolett.5b00292
We report the synthesis and characterization of poly(3-decylselenylene vinylene) (P3DSV) homopolymers and poly(3-decylselenylene vinylene)-co-poly(3-decylthienylene vinylene) (P3DSV-co-P3DTV) copolymers through acyclic diene metathesis (ADMET) polymerization techniques. The obtained polymers were fully characterized. P3DSV was found to possess reduced crystallinity and a smaller bandgap of about 1.6 eV, compared with those of poly(3-decylthienylene vinylene) (P3DTV) analogs. P3DSV-co-P3DTV shows electronic properties between those of the corresponding homopolymers and distinctly different from those of simple blends of the two homopolymers. Our methodology provides a new way to control the physical and electronic properties of low bandgap poly(arylene vinylene)s (PAVs).
Co-reporter:Fei Li, Kevin G. Yager, Noel M. Dawson, Ying-Bing Jiang, Kevin J. Malloy and Yang Qin
Polymer Chemistry 2015 vol. 6(Issue 5) pp:721-731
Publication Date(Web):10 Oct 2014
DOI:10.1039/C4PY00934G
We describe a facile strategy of precisely nano-structuring conjugated polymer (CP)/fullerene composites for organic photovoltaics (OPVs). By building in strong complementary hydrogen bonding interactions between CP nanofibers (NFs) and fullerene derivatives, well-defined and stable supramolecular polymer/fullerene composite NFs are obtained. Specifically, a conjugated block copolymer having poly(3-hexylthiophene) (P3HT) backbone selectively functionalized with polar isoorotic acid moieties, P3HT-b-P3IOAT, and a diaminopyridine tethered fullerene derivative, PCBP, are used as the building blocks. Self-assembly of P3HT-b-P3IOAT in mixed solvents leads to core–shell micelle-like NFs having IOA groups preferentially located on the periphery of the P3HT NF core, onto which PCBP molecules are subsequently attached non-covalently. Formation of such complex structures are studied in detail and confirmed by NMR spectroscopy, absorption spectroscopy, transmission electron microscopy, atomic force microscopy, and X-ray scattering measurements. Application of these composite NFs in OPV devices is investigated and evaluated, which shows close correlations between device performance and morphology controllability.
Co-reporter:Fei Li, Noel M. Dawson, Ying-Bing Jiang, Kevin J. Malloy, Yang Qin
Polymer 2015 Volume 76() pp:220-229
Publication Date(Web):12 October 2015
DOI:10.1016/j.polymer.2015.09.005
•Conjugated block copolymers with selective functionalization.•Orthogonal non-covalent interactions in cooperation.•Hierarchical nanostructures resulted from self-assembly processes.We have previously reported the formation of polymer/fullerene core–shell composite nanofibers (NFs) through self-assembly of functionalized conjugated block copolymers and fullerene derivatives, by cooperation of orthogonal non-covalent interactions including block copolymer phase separation, fullerene aggregation, poly(3-hexylthiophene) (P3HT) crystallization and complementary hydrogen bonding. These NFs displayed improved solar cell performances and the core–shell type structures are generally insensitive to polymer/fullerene weight ratios. In order to better understand the self-assembly mechanisms of such complex systems, we have prepared a new block copolymer (P3) having a different block length ratio and studied its solution and thin film morphologies in the presence of fullerene derivatives at different weight ratios. Worm-like micelles are observed for P3 in mixed-solvent solutions, distinctly different from the well-defined NFs observed previously. Upon fullerene additions, the solution morphologies gradually change into hierarchically complex nanostructures with varying fullerene contents. Thin film morphologies are studied by atomic force microscopy (AFM) and the blends are applied in organic solar cell (OSC) devices. Our present studies provide detailed information on the self-assembly behaviors of conjugated block copolymers and fullerenes under cooperative orthogonal non-covalent interactions.
Co-reporter:Fei Li, Kevin G. Yager, Noel M. Dawson, Ying-Bing Jiang, Kevin J. Malloy, and Yang Qin
Chemistry of Materials 2014 Volume 26(Issue 12) pp:3747
Publication Date(Web):May 31, 2014
DOI:10.1021/cm501251n
A novel methodology of precisely constructing stable and controllable conjugated polymer (CP)/fullerene nanostructures is presented. By building in noncovalent interactions between CP nanofibers (NFs) and fullerene derivatives, supramolecular polymer/fullerene composite NFs are obtained in solution for the first time. Specifically, a conjugated block copolymer having poly(3-hexylthiophene) (P3HT) backbone selectively functionalized with polar isoorotic acid (IOA) moieties, P1, is used as the building block. Self-assembly of P1 in mixed solvents leads to well-defined NFs decorated with IOA groups on the periphery, onto which phenyl-C61-butyric acid methyl ester (PCBM) molecules are subsequently attached noncovalently. Formation of such complex structures are studied in detail and confirmed by UV–vis absorption spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray scattering measurements. Application of these composite NFs in organic photovoltaic (OPV) devices not only leads to superior performance but also much improved thermal stability and better defined and controllable morphology, when compared with conventional bulk heterojunction (BHJ) devices.
Co-reporter:Wenhan He, Yingbing Jiang and Yang Qin
Polymer Chemistry 2014 vol. 5(Issue 4) pp:1298-1304
Publication Date(Web):22 Oct 2013
DOI:10.1039/C3PY01396K
A conjugated boron-dipyrromethene (BODIPY)–platinum polymer possessing a low bandgap of 1.7 eV has been synthesized and characterized. Bulk heterojunction solar cells employing this polymer gave high open circuit voltages up to 0.92 V and power conversion efficiencies close to 1%.
Co-reporter:Guoshun Yang;Keda Hu
Journal of Polymer Science Part A: Polymer Chemistry 2014 Volume 52( Issue 5) pp:591-595
Publication Date(Web):
DOI:10.1002/pola.27042
Co-reporter:Keda Hu;Elena Pres
Journal of Polymer Science Part A: Polymer Chemistry 2014 Volume 52( Issue 18) pp:2662-2668
Publication Date(Web):
DOI:10.1002/pola.27286
ABSTRACT
We report the synthesis and characterization of a novel series of platinum-segmented polydiacetylenes (Pt-PDAs). These polymers can be considered PDAs having every other double bond replaced with a Pt center and fully conjugated side groups attached to the remaining double bonds. Physical, optical and electronic properties of these polymers can be systematically tuned by changing the side groups from alkyl to phenyl and to thienyl moieties. Application of these polymers in solution-processed organic photovoltaic devices is attempted and evaluated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2662-2668
Co-reporter:Keda Hu, Haishen Yang, Wei Zhang and Yang Qin
Chemical Science 2013 vol. 4(Issue 9) pp:3649-3653
Publication Date(Web):09 Jul 2013
DOI:10.1039/C3SC51264A
Novel polydiacetylenes (PDAs) bearing alkyl and phenyl substituents have been synthesized, for the first time, by solution polymerization using acyclic enediyne metathesis. The resulting polymers are soluble in common organic solvents and show distinct physical and photophysical properties both in solution and as thin films, caused by different steric and electronic effects from the side-groups. Bulk heterojunction solar cells employing these PDAs have been fabricated and evaluated.
Co-reporter:Fei Li, Kevin G. Yager, Noel M. Dawson, Jianzhong Yang, Kevin J. Malloy, and Yang Qin
Macromolecules 2013 Volume 46(Issue 22) pp:9021-9031
Publication Date(Web):November 6, 2013
DOI:10.1021/ma4016399
We report the synthesis and characterization of a polythiophene diblock copolymer selectively functionalized with 1-n-hexylisoorotic acid moieties (P4) and a 2,6-diaminopyridine tethered fullerene derivative (PCBP). Self-assembly between P4 and PCBP through “three-point” complementary hydrogen bonding interactions is utilized to control and stabilize blend morphologies. These interactions have been studied both in solution and in solid state by 1H NMR and UV–vis spectroscopies as well as optical and atomic force microscopies (AFM). Solar cells employing P4 blended with different weight ratios of PCBP and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated and tested. The best power conversion efficiencies (PCEs) were observed in devices made from P4/PCBP blends (10/8 by wt) and ternary blends of P4/PCBP/PCBM (10/4/4 by wt) as active layers. Thermal stabilities of these solar cells were studied in detail by aging tests, and corresponding morphological changes were closely monitored by absorption spectroscopy, optical microscopy, AFM, and X-ray analyses. The “three-point” complementary hydrogen bonding interactions between P4 and PCBP, in cooperation with block polymer self-assembly, were found to not only improve the thermal stability of solar cells significantly but also lead to tunable active layer morphologies. Nanostructures with long-range order were identified in blend films employing P4, which has never been observed before in conventional polymer/fullerene bulk heterojunction (BHJ) films.
Co-reporter:Fei Li;Jianzhong Yang
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 16) pp:3339-3350
Publication Date(Web):
DOI:10.1002/pola.26731
ABSTRACT
We report the synthesis and characterization of a polythiophene block copolymer (P4) selectively functionalized with diaminopyrimidine moieties and a thymine tethered fullerene derivative (F1). Self-assembly between P4 and F1 through “three-point” complementary hydrogen bonding is studied by 1H NMR spectroscopy and differential scanning calorimetry. A large Stern-Volmer constant (KSV) of 1.2 × 105 M−1 is observed from fluorescence quenching experiments, revealing strong complexation between these two components. Solar cells employing P4 and F1 at different weight ratios as active layers are fabricated and tested; corresponding thin film morphologies are studied in detail by optical imaging and atomic force microscopy. Correlations between polymer complex structures, film morphologies, and device performance are discussed. Thermal stability of benchmark poly(3-hexylthiophene) bulk heterojunction solar cells is found to be improved by the addition of a few weight percent of P4/F1 complexes as compatibilizers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3339–3350
Co-reporter:Jianzhong Yang, Wenhan He, Kimberly Denman, Ying-Bing Jiang and Yang Qin
Journal of Materials Chemistry A 2015 - vol. 3(Issue 5) pp:NaN2119-2119
Publication Date(Web):2014/12/03
DOI:10.1039/C4TA05405A
We report the synthesis and characterization of a tetrapodal breakwater-like small molecule, SO, containing a tetraphenylsilane core and four cyanoester functionalized terthiophene arms. SO possesses a deep lying HOMO energy level of −5.2 eV and a narrow bandgap of 1.9 eV. Absorption, X-ray scattering and differential scanning calorimetry (DSC) measurements indicate crystalline nature of this compound but very slow crystallization kinetics. Solar cells employing SO and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated and evaluated. Relatively low performance was obtained mainly due to the lack of optimal phase separation under various processing conditions including thermal annealing, slow-cooling and solvent annealing. Addition of poly(thienylene vinylene) (PTV), poly(3-hexylthiophene) (P3HT) and a platinum-containing low bandgap conjugated polymer Pt–BODIPY, into the SO/PCBM blend was found to induce device favorable phase separation and the polymers were found to act as the primary hole conductor. Such ternary blend devices showed cooperatively improved performances over binary devices employing either SO or the individual conjugated polymer alone.
Co-reporter:Wenhan He, Maksim Y. Livshits, Diane A. Dickie, Jianzhong Yang, Rachel Quinnett, Jeffrey J. Rack, Qin Wu and Yang Qin
Chemical Science (2010-Present) 2016 - vol. 7(Issue 9) pp:NaN5804-5804
Publication Date(Web):2016/05/23
DOI:10.1039/C6SC00513F
A novel Pt-bisacetylide small molecule (Pt-SM) featuring “roller-wheel” geometry was synthesized and characterized. When compared with conventional Pt-containing polymers and small molecules having “dumbbell” shaped structures, Pt-SM displays enhanced crystallinity and intermolecular π–π interactions, as well as favorable panchromatic absorption behaviors. Organic solar cells (OSCs) employing Pt-SM achieve power conversion efficiencies (PCEs) up to 5.9%, the highest reported so far for Pt-containing polymers and small molecules.
Co-reporter:Keda Hu, Haishen Yang, Wei Zhang and Yang Qin
Chemical Science (2010-Present) 2013 - vol. 4(Issue 9) pp:NaN3653-3653
Publication Date(Web):2013/07/09
DOI:10.1039/C3SC51264A
Novel polydiacetylenes (PDAs) bearing alkyl and phenyl substituents have been synthesized, for the first time, by solution polymerization using acyclic enediyne metathesis. The resulting polymers are soluble in common organic solvents and show distinct physical and photophysical properties both in solution and as thin films, caused by different steric and electronic effects from the side-groups. Bulk heterojunction solar cells employing these PDAs have been fabricated and evaluated.
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