Lixiang Wang

Porous hyperbranched conjugated polymer nanoparticles with an average particle size of 20–60 nm and a specific surface area of 225 m2 g−1 have been prepared through Suzuki polymerization in a miniemulsion, which could be stably dispersed in common organic solvents after complete removal of surfactants. Furthermore, a simple spin-coating method for the preparation of homogeneous transparent thin films of the nanoparticle has been developed. Bright blue emission of the porous nanoparticle films could be reversibly quenched by nitroaromatics with enhanced sensitivity compared to dense films of the linear conjugated polymer analogue.

A chlorinated phenazine-based donor–acceptor copolymer with enhanced photovoltaic performance

Co-reporter:Ying Li, Bin Meng, Hui Tong, Zhiyuan Xie and Lixiang Wang

Polymer Chemistry 2014 vol. 5(Issue 6) pp:1848-1851

Publication Date(Web):16 Dec 2013

DOI:10.1039/C3PY01436C

Chlorinated phenazine-based donor–acceptor conjugated copolymer PCTClP was designed and synthesized through Suzuki coupling polymerization. Compared to the unsubstituted copolymer PCTP, PCTClP exhibited a narrower band gap and a lower HOMO energy level. PCTClP/PC71BM based polymer solar cells show improved photovoltaic performance with power conversion efficiencies up to 4.06%.

Small molecules based on 2,7-carbazole for efficient solution-processed organic solar cells

Co-reporter:Pengcheng Li, Hui Tong, Junqiao Ding, Zhiyuan Xie and Lixiang Wang

Journal of Materials Chemistry A 2013 vol. 1(Issue 31) pp:8805-8812

Publication Date(Web):24 May 2013

DOI:10.1039/C3TA11168G

A series of small molecules (DTCz-TBT, DTCz-2TBT and DTCz-3TBT) with 2,7-carbazole as a center core donor, benzothiadiazole as acceptor units and oligothiophenes as end-capping units were synthesized and characterized. Their thermal, optical, electrochemical and photovoltaic properties were examined. With increasing the number of the terminal thiophene units and conjugation length, these molecules exhibit red-shifted absorption (529–594 nm), up-shifted HOMO levels (−5.27 to −5.08 eV), and reduced optical band gaps (2.04 to 1.80 eV). Solution processed organic solar cells (OSCs) based on DTCz-TBT/PC71BM exhibit a power conversion efficiency of 2.26% with a high open-circuit voltage up to 1.02 V, while the OSCs based on DTCz-2TBT/PC71BM and DTCz-3TBT/PC71BM exhibit power conversion efficiencies of 3.44% and 3.90% without any post-treatment.

Synthesis and photovoltaic performance of donor–acceptor copolymers based on thieno[3,2-b]quinoxaline

Co-reporter:Ying Li, Hui Tong, Zhiyuan Xie and Lixiang Wang

Polymer Chemistry 2013 vol. 4(Issue 9) pp:2884-2890

Publication Date(Web):28 Feb 2013

DOI:10.1039/C3PY00148B

Two new donor–acceptor copolymers containing carbazole and thieno[3,2-b]quinoxaline units with meta- and para-positioned alkoxy groups on the peripheral phenyl rings, PCTTQx-m and PCTTQx-p, were designed and synthesized. Their thermal stability, UV-Vis absorptions, energy levels and photovoltaic properties were investigated. Compared with their quinoxaline analogues using carbazole and quinoxaline derivatives as donor and acceptor units, by simply fusing a thiophene ring to the quinoxaline unit, PCTTQx-m and PCTTQx-p not only exhibit lower bandgaps (∼1.8 eV) but also maintain deep HOMO energy levels (∼−5.3 eV). A polymer solar cell based on PCTTQx-m with the structure ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al showed a promising PCE of 4.40% with a rather high open circuit voltage of 0.89 V, a short circuit current of 9.03 mA cm−2 and a fill factor of 0.54, which was higher than that of PCTTQx-p (3.45%). After solvent vapor annealing treatment, the PCE of the polymer solar cell based on a PCTTQx-m/PC71BM blend film could be further improved to 5.31%.

Porous films based on a conjugated polymer gelator for fluorescent detection of explosive vapors

Co-reporter:Bowei Xu, Yuxiang Xu, Xuchao Wang, Haibo Li, Xiaofu Wu, Hui Tong and Lixiang Wang

Polymer Chemistry 2013 vol. 4(Issue 19) pp:5056-5059

Publication Date(Web):16 Jul 2013

DOI:10.1039/C3PY00806A

A conjugated polymer gelator is synthesized for fluorescence detection of trinitrotoluene (TNT) and dinitrotoluene (DNT) vapors. Its film morphology can be tuned by selection of suitable solvents, and high sensitivity is observed for its porous films even with 90 nm thickness.

Solution-processible hyperbranched conjugated polymer nanoparticles with tunable particle sizes by Suzuki polymerization in miniemulsion

Co-reporter:Haibo Li, Xiaofu Wu, Bowei Xu, Hui Tong and Lixiang Wang

RSC Advances 2013 vol. 3(Issue 23) pp:8645-8648

Publication Date(Web):23 Apr 2013

DOI:10.1039/C3RA40901E

Stable blue emissive hyperbranched conjugated polymer nanoparticles with tunable particle sizes were synthesized by Suzuki polymerization in miniemulsion, which could be facile soluble in common organic solvents after complete removal of surfactants. As highly sensitive fluorescent probes for picric acid, they exhibit 25 times higher fluorescence quenching ability and 100 times wider linear detection region (from 1.0 nM to 4.0 μM) compared to their linear conjugated polymer nanoparticle analogue.

Effect of side-chain positions on morphology and photovoltaic properties of phenazine-based donoracceptor copolymers

Co-reporter:Ying Li;Yingying Fu;Hui Tong;Zhiyuan Xie

Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 13) pp:2910-2918

Publication Date(Web):

DOI:10.1002/pola.26684

ABSTRACT

Two phenazine donor–acceptor-conjugated copolymers (P1 and P2) with the same polymer backbone but different anchoring positions of alkoxy chain on the phenazine unit were investigated to identify the effect of changing the position of alkoxy chains on their optical, electrochemical, blend film morphology, and photovoltaic properties. Although the optical absorption and frontier orbital energy levels were insensitive to the position of alkoxy chains, the film morphologies and photovoltaic performances changed significantly. P1/PC₇₁BM blend film showed the formation of phase separation with large coarse aggregates, whereas P2/PC₇₁BM blend film was homogeneous and smooth. Accordingly, power conversion efficiency (PCE) of photovoltaic devices increased from 1.50% for P1 to 2.54% for P2. In addition, the PCE of the polymer solar cell based on P2/PC₇₁BM blend film could be further improved to 3.49% by using solvent vapor annealing treatment. These results clearly revealed that tuning the side-chain position could be an effective way to adjust the morphology of the active layer and the efficiency of the photovoltaic device. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2910–2918

Synthesis, characterization and solar cell application of a D-A copolymer with cyclopentadithiophene and fluorene as donor units

Co-reporter:Hai-yang Song;Hui Tong 童辉;Zhi-yuan Xie

Chinese Journal of Polymer Science 2013 Volume 31( Issue 8) pp:1117-1126

Publication Date(Web):2013 August

DOI:10.1007/s10118-013-1302-z

In this paper, a new D-A copolymer, PFDBCPDT, which consists of benzo-2,1,3-thiadiazole as acceptor units and cyclopentadithiophene and fluorene as donor units, was synthesized. The thermal, electrochemical, photophysical and photovoltaic properties of PFDBCPDT were studied. PFDBCPDT showed a low optical band gap of 1.84 eV, and relatively low HOMO level of −5.69 eV. The best device performance was obtained by PFDBCPDT/PC61BM (1:3) with 0.5 vol% DIO. The device exhibited a power conversion efficiency of 3.06%, with a relatively high open circuit voltage of 0.87 eV.

Synthesis and characterization of blue light-emitting poly(aryl ether)s containing pyrimidine-incorporated oligofluorene pendants with bipolar feature

Co-reporter:Guo-xin Jiang;Chun-lei Bian;Jun-qiao Ding 丁军侨

Chinese Journal of Polymer Science 2013 Volume 31( Issue 5) pp:787-797

Publication Date(Web):2013 May

DOI:10.1007/s10118-013-1279-7

Novel blue light-emitting poly(aryl ether)s comprising of bipolar oligofluorene pendants as chromophores have been designed and synthesized, in which pyrimidine and arylamine moieties are utilized as the electron acceptor and electron donor, respectively. Through varying π bridge length from monofluorene to bifluorene and end-cappers from hydrogen to carbazole and diphenylamine, the emission color of the resulting polymers covers from deep blue to greenish blue, and their HOMO and LUMO levels can be modulated to facilitate charge injection to improve the device performance. Polymer lightemitting diodes (PLEDs) are fabricated with the device structure of ITO/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) (50 nm)/polymer (80 nm)/Ca (10 nm)/Al (200 nm). Among these polymers, P2Cz5F-Py with bifluorene bridge and carbazole end-capper shows excellent trade-off between the efficiency and emission wavelength, having a peak luminous efficiency as high as 1.26 cd/A and Commission Internationale de L’Eclairage (CIE) coordinates of (0.17, 0.17).

White Electroluminescence from All-Phosphorescent Single Polymers on a Fluorinated Poly(arylene ether phosphine oxide) Backbone Simultaneously Grafted with Blue and Yellow Phosphors

Co-reporter:Shiyang Shao ; Junqiao Ding ; Lixiang Wang ; Xiabin Jing ;Fosong Wang

Journal of the American Chemical Society 2012 Volume 134(Issue 50) pp:20290-20293

Publication Date(Web):December 6, 2012

DOI:10.1021/ja310158j

On the basis of a fluorinated poly(arylene ether phosphine oxide) backbone with both high triplet energy and appropriate HOMO/LUMO levels, highly efficient all-phosphorescent single white-emitting polymers were designed and successfully synthesized via a “two-step addition” strategy. Simultaneous blue and yellow triplet emissions were achieved to generate white electroluminescence with a promising luminous efficiency as high as 18.4 cd/A (8.5 lm/W, 7.1%) and CIE coordinates of (0.31, 0.43).

Highly Efficient Blue Electrophosphorescent Polymers with Fluorinated Poly(arylene ether phosphine oxide) as Backbone

Co-reporter:Shiyang Shao ; Junqiao Ding ; Lixiang Wang ; Xiabin Jing ;Fosong Wang

Journal of the American Chemical Society 2012 Volume 134(Issue 37) pp:15189-15192

Publication Date(Web):September 6, 2012

DOI:10.1021/ja305634j

In view of the tolerance of F atoms in FIrpic to the nucleophilic aromatic substitution polymerization, an activated fluorinated poly(arylene ether phosphine oxide) backbone is used to construct novel blue electrophosphorescent polymers containing FIrpic as the blue emitter, because they can be synthesized under a milder temperature of 120 °C. Compared with the counterparts prepared at high temperature (165 °C), unexpected bathochromic shift is successfully avoided, and a state-of-art luminous efficiency as high as 19.4 cd A–1 is achieved. The efficiency is comparable to the corresponding physical blend system, which indicates that the fluorinated poly(arylene ether phosphine oxide) has the potential to be used as the platform for the development of high-performance all-phosphorescent white polymer based on single polymer system.

Phosphonate substituted 4,4′-bis(N-carbazolyl)biphenyl with dominant electron injection/transport ability for tuning the single-layer device performance of self-host phosphorescent dendrimer

Co-reporter:Bo Chen, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2012 vol. 22(Issue 44) pp:23680-23686

Publication Date(Web):21 Sep 2012

DOI:10.1039/C2JM35526D

A novel phosphonate substituted 4,4′-bis(N-carbazolyl)biphenyl (CBP), namely PCBP, has been designed and successfully synthesized by an indirect palladium catalyzed Suzuki–Miyaura reaction. X-Ray crystallography analysis from a PCBP single crystal demonstrates that there is a hydrogen bond interaction between the two adjacent molecules due to the presence of phosphonate, which promotes their one-dimensional line arrangement along the c-axis. Compared with the prototype CBP (−5.55 eV), in addition, the highest occupied molecular orbital (HOMO) level of PCBP is reduced to −6.00 eV, leading to a large hole injection barrier. On the other hand, the introduction of phosphonate substitutes can endow PCBP with excellent electron injection/transport ability. As a result, PCBP shows an electron-dominated behaviour observed in single carrier devices, which is different from the hole-dominated one for CBP. Such a transition is then used to tune the single-layer device performance of a self-host phosphorescent dendrimer, and the peak luminous efficiency significantly increases from 1.7 cd A−1 of CBP to 31.4 cd A−1 of PCBP.

Synthesis and characterization of yellow-emitting electrophosphorescent polymers based on a fluorinated poly(arylene ether phosphine oxide) scaffold

Co-reporter:Shiyang Shao, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2012 vol. 22(Issue 47) pp:24848-24855

Publication Date(Web):01 Oct 2012

DOI:10.1039/C2JM34421A

A series of novel yellow-emitting electrophosphorescent polymers (PhPs) have been designed and synthesized by grafting a 2-(fluoren-2-yl)-1H-benzoimidazole ligand based iridium complex, (fbi)2Ir(acac), with a fluorinated poly(arylene ether phosphine oxide) backbone (FPCzPO). Due to the efficient intermolecular Förster energy transfer from FPCzPO to (fbi)2Ir(acac) and charge trapping on (fbi)2Ir(acac), the electroluminescence from FPCzPO is almost completely quenched, even if the Ir complex content incorporated into the polymer is as low as 2 mol%. It is found that the polymer exhibits the best device performance when the Ir loading is optimized to 3 mol%. A peak luminous efficiency of 10.4 cd A−1 with Commission Internationale de L'Eclairage coordinates of (0.53, 0.46) is achieved, which is superior to that of the previously reported yellow PhPs with polyfluorene as the main chain. The result indicates that the fluorinated poly(arylene ether phosphine oxide) is a promising scaffold for the construction of efficient yellow PhPs.

A solution-processable phosphonate functionalized deep-blue fluorescent emitter for efficient single-layer small molecule organic light-emitting diodes

Co-reporter:Bo Chen, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Chemical Communications 2012 vol. 48(Issue 71) pp:8970-8972

Publication Date(Web):19 Jul 2012

DOI:10.1039/C2CC34712A

Based on a p-type scaffold, a novel solution-processable phosphonate functionalized deep-blue fluorescent emitter has been designed and synthesized. The corresponding non-doped single-layer SMOLED shows a peak current efficiency of 0.76 cd A−1 with CIE coordinates of (0.15, 0.09), which is about three orders of magnitude higher than that of the prototype with tert-butyl substituents.

Effect of dendron generation on properties of self-host heteroleptic green light-emitting iridium dendrimers

Co-reporter:Lingcheng Chen, Zhihua Ma, Junqiao Ding, Lixiang Wang, Xiabin Jing, Fosong Wang

Organic Electronics 2012 Volume 13(Issue 10) pp:2160-2166

Publication Date(Web):October 2012

DOI:10.1016/j.orgel.2012.06.021

Fluorescent detection of heparin by a cationic conjugated polyfluorene probe containing aggregation-induced emission units

Co-reporter:Bowei Xu, Xiaofu Wu, Haibo Li, Hui Tong, Lixiang Wang

Polymer 2012 Volume 53(Issue 2) pp:490-494

Publication Date(Web):24 January 2012

DOI:10.1016/j.polymer.2011.11.058

A novel conjugated cationic polyfluorene containing aminated tetraphenylethene (ATPE) unit is developed as a sensitive and selective fluorescence probe for heparin detection based on the combination of aggregation-induced emissive property of the ATPE units and the FRET process from the blue-emissive polyfluorene segments to the yellow-emissive ATPE units. The addition of anionic heparin will lead to the formation of heparin/polymer complexes, and turn on the aggregation-induced yellow emission of the ATPE units. A good linear relationship is found between the yellow emission intensity of the ATPE units and the heparin concentrations with a limit of detection of 30 nM in aqueous buffer.

Synthesis and photovoltaic properties of a donor-acceptor polymer containing both dithieno[3,2-b:2′,3′-d]pyrrole and fluorene as donor units

Co-reporter:Haiyang Song, Hui Tong, Zhiyuan Xie, Lixiang Wang, Fosong Wang

Polymer 2012 Volume 53(Issue 22) pp:5103-5108

Publication Date(Web):12 October 2012

DOI:10.1016/j.polymer.2012.09.013

A new donor-acceptor polymer (PDTPDBF), containing both dithieno[3,2-b:2′,3′-d]pyrrole (DTP) and fluorene as electron-donating units and benzo-2,1,3-thiadiazole (BT) as electron-accepting unit, was synthesized by Suzuki coupling reaction. Its optical, thermal, electrochemical and photovoltaic properties have been investigated. Compared with typical DTP-based donor-acceptor polymers, PDTPDBF showed a distinct low HOMO level (−5.47 eV). Theoretical calculation attributed this low-lying HOMO level to both the weaker electron-donating ability of the fluorene unit and the moderately twisted conformation between the fluorene unit and the BT unit. Polymer solar cells (PSCs) based on PDTPDBF and PC71BM (1:2, w/w) exhibited an open circuit voltage of 0.84 V and a power conversion efficiency (PCE) of 4.2%, both of which are relatively high values for DTP-based photovoltaic polymers.Graphical abstract

Meta-linked and para-linked water-soluble poly(arylene ethynylene)s with amino acid side chains: Effects of different linkage on Hg2+ ion sensing properties in aqueous media

Co-reporter:Xiaofu Wu;Bowei Xu;Hui Tong

Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 8) pp:1521-1529

Publication Date(Web):

DOI:10.1002/pola.25914

Abstract

Water-soluble, meta- and para-linked poly(arylene ethynylene)s containing L-aspartic acid-functionalized fluorene units (P1 and P2) and their model compounds (M1 and M2) have been synthesized, and their photophysical properties and fluorescent sensing properties were investigated in aqueous solution. P1 and M1 with the meta-linkage show blue-shifted absorption and emission spectra, and decreased photoluminescence quantum yields compared with those of P2 and M2 with para-linkage. Their absorption and fluorescence spectra are pH dependent perhaps due to the aggregation of the polymer chains at low pH values. In buffer solutions, both polymers and their model compounds exhibit the excellent selectivity and sensitivity to Hg²⁺ over other common metal ions. Furthermore, the quenching constant and detection limit of P1 are determined to be 1.04 × 10⁷ M⁻¹ and 10 nM, and show the higher sensitivity compared to P2. Further comparison of their model compounds reveal that the sensitivity and quenching efficiency of M1 is also higher than that of M2, indicating that the meta-linkage pattern plays a key role in improving their Hg²⁺ ion sensing properties. In addition, both meta- and para-linked polymers exhibit the higher quenching efficiency than their model compounds due to the amplified fluorescence response of conjugated polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Color tuning of Novel 2,1,3-Naphthothiadiazole and 2,1,3-Benzoselenadiazole based D-A-D′ Type dopants to realize highly efficient saturated red emission in non-polar solvents

Co-reporter:Lei Chen, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2011 vol. 21(Issue 28) pp:10265-10267

Publication Date(Web):03 Jun 2011

DOI:10.1039/C1JM11204J

By introduction of 2,1,3-naphthothiadiazole (NT) and 2,1,3-benzoselenadiazole (BS) electron withdrawing units, a series of D-A-D′ type red dopants were synthesized. All of them realized saturated red emission with high fluorescent quantum yields (Φf) in non-polar toluene solutions, especially for MC6, which shows a deep red emission at 643 nm with a Φf of 0.51.

Self-host heteroleptic green iridium dendrimers: achieving efficient non-doped device performance based on a simple molecular structure

Co-reporter:Lingcheng Chen, Zhihua Ma, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Chemical Communications 2011 vol. 47(Issue 33) pp:9519-9521

Publication Date(Web):20 Jul 2011

DOI:10.1039/C1CC13276H

Self-host heteroleptic green iridium(III) dendrimers have been designed and easily synthesized. Through tuning the carbazole dendron density, high efficiency is achieved using these dendrimers with a simple molecular structure as the emitting layer for the non-doped organic light-emitting diodes.

Hexaazatriphenylene Derivatives with Tunable Lowest Unoccupied Molecular Orbital Levels

Co-reporter:Ming Wang, Ying Li, Hui Tong, Yanxiang Cheng, Lixiang Wang, Xiabin Jing, and Fosong Wang

Organic Letters 2011 Volume 13(Issue 16) pp:4378-4381

Publication Date(Web):July 27, 2011

DOI:10.1021/ol201717d

A series of n-type hexaazatriphenylene derivatives were synthesized by condensation coupling of 1,2-diamines and 1,2-diketones. The study of their photophysical and electrochemical properties showed that their lowest unoccupied molecular orbital (LUMO) energy levels could be effectively tuned from −3.54 to −4.02 eV simply by increasing the number of pyrazine units in their molecular structures.

Neutral copper(I) phosphorescent complexes from their ionic counterparts with 2-(2′-quinolyl)benzimidazole and phosphine mixed ligands

Co-reporter:Junhui Min, Qisheng Zhang, Wei Sun, Yanxiang Cheng and Lixiang Wang

Dalton Transactions 2011 vol. 40(Issue 3) pp:686-693

Publication Date(Web):02 Dec 2010

DOI:10.1039/C0DT01031F

Neutral mononuclear CuI complexes and their counterparts with counterion, i.e.Cu(qbm)(PPh3)2, Cu(qbm)(DPEphos), [Cu(Hqbm)(PPh3)2](BF4) and [Cu(Hqbm)(DPEphos)](BF4), where Hqbm = 2-(2′-quinolyl)benzimidazole, DPEphos = bis[2-(diphenylphosphino)phenyl]ether, have been synthesized and characterized by X-ray structure analyses. All of the four complexes in solid state exhibit a strong phosphorescence band in the orange spectral region at room temperature. The photophysical properties of these complexes in both methylene chloride solution and poly(methyl methacrylate) film have been studied. Compared to the related cationic complexes, the neutral ones show blue-shifted emissions and longer lifetimes that can be attributed to the additional ligand-centered π–π* transition beside traditional metal-to-ligand charge-transfer (MLCT). By doping these complexes in N-(4-(carbazol-9-yl)phenyl)-3,6-bis(carbazol-9-yl) carbazole (TCCz), multilayer organic light-emitting diodes (OLEDs) were fabricated with the device structure of ITO/PEDOT/TCCz: CuI (10 wt%)/BCP/Alq3/LiF/Al. The neutral complex Cu(qbm)(DPEphos) exhibits a higher current efficiency, up to 8.87 cd A−1, than that (5.58 cd A−1) of its counterpart [Cu(Hqbm)(DPEphos)](BF4).

Polyfluorenes containing pyrazine units: Synthesis, photophysics and electroluminescence

Co-reporter:Ming Wang;Ying Li;ZhiYuan Xie

Science China Chemistry 2011 Volume 54( Issue 4) pp:656-665

Publication Date(Web):2011 April

DOI:10.1007/s11426-011-4238-6

A series of conjugated copolymers of 9,9-dioctylfluorene and symmetrical pyrazine unit (BY) were synthesized by Suzuki copolymerization and were used as novel light-emitting materials in PLEDs. Efficient energy transfer was observed in both thin film and solution. Compared with the lowest occupied molecular orbital (LUMO) energy level of the polyfluorenes homopolymer (PFO), the lower LUMO energy levels of copolymers indicated that the introduction of the BY unit would be benefit to electron injection. The turn-on voltages of their single-layer electroluminescent (EL) devices (ITO/PEDOT/polymer/LiF/Al) were at 6.1–4.0 V, which were much lower than that of PFO (7.0 V). The maximum brightness, current efficiency, and external quantum efficiency of all PFBY copolymers were higher than those of the PFO homopolymer. The single-layer device of PFBY5 was the best one in the copolymers, with a maximum brightness of 485 cd/m2, a current efficiency of 0.29 cd/A, and an external quantum efficiency of 0.10%. The introduction of PVK and TPBI for the multilayer device of PFBY5 increased the device efficiencies, which showed a maximum brightness of 3012 cd/m2, a maximum current efficiency of 1.81 cd/A, and an external quantum efficiency of 0.66%.

Selective Detection of TNT and Picric Acid by Conjugated Polymer Film Sensors with Donor–Acceptor Architecture

Co-reporter:Bowei Xu, Xiaofu Wu, Haibo Li, Hui Tong, and Lixiang Wang

Macromolecules 2011 Volume 44(Issue 13) pp:5089-5092

Publication Date(Web):June 9, 2011

DOI:10.1021/ma201003f

Synthesis and characterization of red light-emitting electrophosphorescent polymers with different triplet energy main chain

Co-reporter:Zhihua Ma, Junqiao Ding, Yanxiang Cheng, Zhiyuan Xie, Lixiang Wang, Xiabin Jing, Fosong Wang

Polymer 2011 Volume 52(Issue 10) pp:2189-2197

Publication Date(Web):4 May 2011

DOI:10.1016/j.polymer.2011.03.023

Red light-emitting electrophosphorescent polymers with poly(fluorene-alt-carbazole) (PFCz) and poly(3,6-carbazole) (PCz) as the main chain, and the quinoline-based iridium (Ir) complex as the side chain have been synthesized by Suzuki and modified Yamamoto polymerization, respectively. The triplet energy of the polymeric backbone is tuned from 2.1 eV of polyfluorene (PF) to 2.3 eV of PFCz and 2.6 eV of PCz. We find that, with the increasing triplet energy, the lifetime of the triplet excitons gradually increases, but the device efficiency becomes worse. The reason is that the alteration of the main chain structure leads to the increase of the highest occupied molecular orbital (HOMO) level of the polymeric host, which can facilitate the efficient hole injection and transportation. As a consequence of this enhancement of the hole current, charge balance in the emitting layer is destroyed, and correspondingly, the poorer device performance is achieved. Our results, we believe, indicate that besides the triplet energy, charge balance is a crucial determinant to develop high efficiency red light-emitting electrophosphorescent polymers.

A Water-Soluble Organometallic Conjugated Polyelectrolyte for the Direct Colorimetric Detection of Silver Ion in Aqueous Media with High Selectivity and Sensitivity

Co-reporter:Chuanjiang Qin, Wai-Yeung Wong, and Lixiang Wang

Macromolecules 2011 Volume 44(Issue 3) pp:483-489

Publication Date(Web):December 31, 2010

DOI:10.1021/ma102373y

A water-soluble organometallic conjugated polyelectrolyte P1 and its corresponding model complex M1 based on an aspartic acid-substituted fluorene spacer are reported, which possess good water solubility as well as intriguing fluorescent and phosphorescent dual-emissive properties in a completely organic-free aqueous medium at room temperature. A new colorimetric silver ion sensor based on P1 is developed, which shows high selectivity and sensitivity for Ag+ ions in buffered water solution because of the Ag+-induced intersystem crossing from the singlet to triplet states. The obvious color change from colorless to yellow upon exposure to Ag+ ion is visible to the naked eyes and can be quantified colorimetrically by the visible absorption spectroscopic method. On the basis of the fluorescence intensity of P1 obtained in the fluorescence titration curves, a linear relationship is observed in the Stern−Volmer plot at low concentrations (1−5 μM), and the corresponding Stern−Volmer quenching constant (KSV) of 1.9 × 105 M−1 for P1 is comparable to that obtained from the fluorescence titration studies. As determined by the Benesi−Hildebrand plot obtained from the absorption spectra, a 1:1 complex formation is anticipated between the Pt compound and Ag+ ion. The limit of detection is low at 0.5 μM, i.e., at concentrations in the ppb range. The present study represents an original approach using a water-soluble organometallic conjugated polyelectrolyte for the accurate and rapid detection of trace amounts of Ag+ ion in pure water. It also establishes a new system featuring dual-emissive properties of platinum(II) acetylide-based conjugated polymers for chemosensing application.

Pure and Saturated Red Electroluminescent Polyfluorenes with Dopant/Host System and PLED Efficiency/Color Purity Trade-Offs

Co-reporter:Lei Chen;Baohua Zhang;Yanxiang Cheng;Zhiyuan Xie;Xiabin Jing;Fosong Wang

Advanced Functional Materials 2010 Volume 20( Issue 18) pp:3143-3153

Publication Date(Web):

DOI:10.1002/adfm.201000840

Abstract

Three kinds of red electroluminescent (EL) polymers based on polyfluorene as blue host and 2,1,3-benzothiadiazole derivatives with different emission wavelengths as red dopant units on the side chain are designed and synthesized. The influence of the photoluminescence (PL) efficiencies and emission wavelengths of red dopants on the EL efficiencies and color purities of the resulting polyfluorene copolymers of dopant/host system is investigated by adjusting the electron donating ability of the donor units in D-π-A-D typed 2,1,3-benzothiadiazole derivatives. The devices of these red-emitting polymers realize remarkable EL efficiency/color purity trade-offs. The single-layer devices with the configuration of ITO/PEDOT:PSS/Polymer/Ca/Al show pure red emission at 624 nm with a luminous efficiency of 3.83 cd A⁻¹ and CIE of (0.63, 0.35) for PFR1, saturated red emission at 636 nm with a luminous efficiency of 2.29 cd A⁻¹ and CIE of (0.64, 0.33) for PFR2, respectively. By introduction of an additional electron injection layer PF-EP(Ethanol soluble phosphonate-functionalized polyfluorene), high performance pure and saturated red emission two-layer devices (ITO/PEDOT:PSS/Polymer/PF-EP/LiF/Al) were achieved with maximum luminous efficiencies of 5.50 cd A⁻¹ and CIE of (0.62, 0.35) for PFR1, 3.10 cd A⁻¹ and CIE of (0.63, 0.33) for PFR2, respectively, which are the best results for pure and saturated fluorescent red EL polymers reported so far.

Red-Emitting Polyfluorenes Grafted with Quinoline-Based Iridium Complex: Simple Polymeric Chain, Unexpected High Efficiency

Co-reporter:Zhihua Ma;Junqiao Ding;Baohua Zhang;Chongyu Mei;Yanxiang Cheng;Zhiyuan Xie;Xiabin Jing;Fosong Wang

Advanced Functional Materials 2010 Volume 20( Issue 1) pp:138-146

Publication Date(Web):

DOI:10.1002/adfm.200901595

Abstract

A series of red-light emitting electrophosphorescent polyfluorenes (PFs) with varying content of a quinoline-based iridium complex, (PPQ)₂Ir(acac) (bis(2,4-diphenylquinolyl-N,C^2′) iridium(acetylacetonate)), in the side chain are synthesized by Suzuki polycondensation. Because of the efficient Förster energy transfer from the PF main chain to (PPQ)₂Ir(acac) and direct charge trapping on the complex, the electroluminescent emission from PF is nearly completely quenched, even though the amount of iridium complex incorporated into the polymers is as low as 1 mol %. Based on a single-layer device configuration, a luminous efficiency of up to 5.0 cd A⁻¹ with a luminance of 2000 cd m⁻² and Commission Internationale de L'Eclairage coordinates of (0.63, 0.35) (x, y) is realized, which is far superior to that of previously reported red-light emitting PFs containing benzothiazole- and isoquinoline-based iridium complexes. This result is beyond expectations, especially when considering that the simple polymeric chain involved has no additional charge-transporting moieties. Noticeably, the device efficiency remains as high as 4.2 cd A⁻¹ with a luminance of 4000 cd m⁻² even at current densities of 100 mA cm⁻². Further optimization of the device configuration by incorporating an additional electron-injection layer leads to improved efficiencies of 8.3 and 7.5 cd A⁻¹ at luminances of 100 and 1000 cd m⁻², respectively. This state-of-the-art performance indicates that covalently attaching quinoline-based iridium complexes to a PF backbone is a simple and effective strategy to develop high-efficiency red-light emitting electrophosphorescent polymers.

Design of star-shaped molecular architectures based on carbazole and phosphine oxide moieties: towards amorphous bipolar hosts with high triplet energy for efficient blue electrophosphorescent devices

Co-reporter:Junqiao Ding, Qi Wang, Lei Zhao, Dongge Ma, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2010 vol. 20(Issue 37) pp:8126-8133

Publication Date(Web):19 Aug 2010

DOI:10.1039/C0JM00846J

With a carbazole moiety as the electron donor and a phosphine-oxide moiety as the electron acceptor, two novel star-shaped bipolar hosts, 4,4′,4″-tri(N-carbazolyl)triphenylphosphine oxide (TCTP) and 3,6-bis(diphenylphosphoryl)-9-(4′-(diphenylphosphoryl)phenyl)carbazole (TPCz), have been designed and synthesized. Their topology structure differences are that the phosphine-oxide moiety is located in the molecular centre and the periphery for TCTP and TPCz, respectively. The star-shaped architecture imparts them with high decomposition temperatures (Td: 497 °C for TCTP and 506 °C for TPCz) and results in the formation of a stable amorphous glassy state (Tg: 163 °C for TCTP and 143 °C for TPCz), while the phosphine oxide linkage ensures the disrupted conjugation and the high triplet energy (>3.0 eV). In addition, both TCTP and TPCz possess a bipolar transporting capability. However, TCTP mostly transports holes and TPCz primarily conducts electrons. On the basis of appropriate device configurations, high performance blue electrophosphorescent devices with comparable efficiency (35.0–36.4 cd A−1, 15.9–16.7%) have been realized using TCTP and TPCz as the host for the blue phosphor, respectively. Compared with the unipolar host, 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA, 15.9 cd A−1, 7.8%), the efficiency is improved by more than two-fold. As far as the obtained state-of-the-art performance is concerned, we think that these novel materials should provide an avenue for the design of amorphous bipolar hosts with high triplet energy used for blue PhOLEDs on a star-shaped scaffold.

High solubility and photoluminescence quantum yield water-soluble polyfluorenes with dendronized amino acid side chains: synthesis, photophysical, and metal ion sensing properties

Co-reporter:Chuanjiang Qin, Xiaofu Wu, Hui Tong and Lixiang Wang

Journal of Materials Chemistry A 2010 vol. 20(Issue 37) pp:7957-7964

Publication Date(Web):20 Aug 2010

DOI:10.1039/C0JM01094D

A series of anionic water-soluble dendronized conjugated polymers PG0, PG1 and PG2 are synthesized by copolymerization of dendritic macromonomers and phenyldiboronic ester via direct Suzuki polycondensation reaction in THF–water solution. Water solubility and solution photoluminescence quantum yield increase with increasing the generation of the dendrons. PG2 exhibits an extremely high solubility which achieves 200 mg mL−1 in aqueous solution and the corresponding quantum yield was measured to be 95%. The absorption and fluorescence spectra of the dendronized polymers are pH-dependent due to the aggregation of the polymer chains. PL spectrum of PG2 also exhibits better stability among large window of pH and high salt concentration than the other two polymers. Three polymers demonstrate different sensory behavior to metal ions. Among them, most metal ions can moderately quench the fluorescence of PG0, on the other hand, PG1 and PG2 have good selectivity and sensitivity to Hg2+ and Cu2+, respectively. Thin-films based on PG0, PG1, and PG2 are fabricated by spin-coating, layer-by-layer (LbL) deposition, and self-assembly on amine-functionalized quartz followed by thermal-annealing. Among them, the annealed films have good spectral stability in aqueous solution, which makes them promising materials for the application in the field of chemo- and biosensors and light-emitting devices.

Smectic liquid crystals based on hexaazatriphenylene: potential organic n-type semiconductor

Co-reporter:Baoxiang Gao, Licui Zhang, Qianqian Bai, Ying Li, Junwei Yang and Lixiang Wang

New Journal of Chemistry 2010 vol. 34(Issue 12) pp:2735-2738

Publication Date(Web):05 Oct 2010

DOI:10.1039/C0NJ00586J

We report the synthesis of dibenzohexaazatriphenylene derivative DBHAT. The addition of electron-withdrawing groups on the dibenzohexaazatriphenylene core leads to a high electron-accepting capability. DBHAT exhibits reversible four-step reduction waves at half-wave potentials (E1/2) of −0.42, −0.94, −1.35 and −1.80 V vs. Ag/AgCl. Furthermore, DBHAT is able to form a smectic liquid crystalline assembly over a wide temperature range. With strong dipole–dipole interactions, the smectic liquid crystals show extremely highly stabilized mesophases.

Twofold terminal post-functionalization of acetylacetone with hole- and electron-transporting fragments

Co-reporter:Lingcheng Chen, Junqiao Ding, Yanxiang Cheng, Lixiang Wang, Xiabin Jing, Fosong Wang

Tetrahedron Letters 2010 Volume 51(Issue 35) pp:4612-4616

Publication Date(Web):1 September 2010

DOI:10.1016/j.tetlet.2010.06.090

A modular synthetic methodology has been developed to prepare β-diketones functionalized with hole- and electron-transporting fragments at their two termini. The optical and electrochemical properties of these new β-diketones are also described in detail.A modular synthetic methodology has been developed to prepare β-diketones functionalized with hole- and electron-transporting fragments at their two termini. The optical and electrochemical properties of these new β-diketones are also described in detail.

Band gap tunable for near-infrared absorbing chromophores with multi-triphenylamine and tris (thieno)hexaazatriphenylenes acceptors

Co-reporter:Baoxiang Gao, Defang Xia, Yanhou Geng, Yanxiang Cheng, Lixiang Wang

Tetrahedron Letters 2010 Volume 51(Issue 14) pp:1919-1921

Publication Date(Web):7 April 2010

DOI:10.1016/j.tetlet.2010.02.039

Two disk-like D–A type chromophores with multi-triphenylamine donors and hexaazatriphenylenes acceptors were synthesized and fully characterized by 1H and 13C NMR, elemental analysis and mass spectrometry. The effects of the hexaazatriphenylene on the optical and electrochemical properties and band gap of the chromophores were investigated. As the hexaazatriphenylene core fused with three thiophene rings, the band gaps of the compounds could be tuned from 1.65 eV to 1.15 eV. The π–π* absorption peak and charge-transfer absorption peak of the hexaazatriphenylene compounds were red shifted from visible spectrum region (393 and 530 nm) to near-infrared spectrum region (542 and 756 nm). In addition, due to an increase in the π electronic coupling between electron donor and electron acceptor, the extinction coefficient (charge-transfer absorption) of the hexaazatriphenylene compound decreases 85% from 3.4 × 104 mol−1 dm−3 cm−1 to 0.5 × 104 mol−1 dm−3 cm−1.

Synthesis and characterization of polyfluorenes containing bisphenazine units

Co-reporter:Ming Wang;Hui Tong;Yanxiang Cheng;Zhiyuan Xie;Xiabin Jing;Fosong Wang

Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 9) pp:1990-1999

Publication Date(Web):

DOI:10.1002/pola.23966

Abstract

Novel conjugated copolymers based on 9,9-dioctylfluorene and bisphenazine (BP) were synthesized by Suzuki polymerization. Energy transfer from the conjugated main chain to the BP moieties was observed. Full energy transfer was achieved when the molar content of the bisphenazine was 20% (20BPPF) in toluene solution. The similar phenomena were observed even for 1% bisphenazine content copolymer (1BPPF) in film. The lowest occupied molecular orbital (LUMO) energy levels (−3.06 eV) of the copolymers were lower than that of the polyfluorene homopolymer (PFO; −2.65 eV), indicating that the introduction of the BP unit was benefit to electron injection. Single-layer electroluminescent devices (ITO/PEDOT:PSS/polymer/LiF/Al) were fabricated to investigate their electroluminescence (EL) performances. The maximum brightness and current efficiency of all BPPF copolymers surpassed the PFO homopolymer. The best single-layer device was based on 5BPPF, with a maximum brightness of 1532 cd/m² and current efficiency of 1.09 cd/A. Much higher efficiency could be achieved for multilayer EL devices of 5BPPF (ITO/PEDOT:PSS/PVK/polymer/TPBI/LiF/Al), which showed a maximum current efficiency of 10.01 cd/A. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1990–1999, 2010

Solution-Processable Carbazole-Based Conjugated Dendritic Hosts for Power-Efficient Blue-Electrophosphorescent Devices

Co-reporter:Junqiao Ding;Baohua Zhang;Jianhong Lü;Zhiyuan Xie;Xiabin Jing;Fosong Wang

Advanced Materials 2009 Volume 21( Issue 48) pp:4983-4986

Publication Date(Web):

DOI:10.1002/adma.200902328

White Electroluminescence from a Phosphonate-Functionalized Single-Polymer System with Electron-Trapping Effect

Co-reporter:Xin Guo;Chuanjiang Qin;Yanxiang Cheng;Zhiyuan Xie;Yanhou Geng;Xiabin Jing;Fosong Wang

Advanced Materials 2009 Volume 21( Issue 36) pp:3682-3688

Publication Date(Web):

DOI:10.1002/adma.200803734

Flourescent Switch Constructed Based on Hemin-Sensitive Anionic Conjugated Polymer and Its Applications in DNA-Related Sensors

Co-reporter:Bingling Li, Chuanjiang Qin, Tao Li, Lixiang Wang and Shaojun Dong

Analytical Chemistry 2009 Volume 81(Issue 9) pp:3544

Publication Date(Web):April 3, 2009

DOI:10.1021/ac900110a

Here, a fluorescent switch is constructed combining hemin, hemin aptamer, and a newly synthesized anionic conjugated polymer (ACP), poly(9,9-bis(6′-phosphatehexyl) fluorenealt-1,4-phenylene) sodium salt (PFHPNa/PFP). In the “off-state”, the fluorescence of PFP is sensitively quenched by hemin, with a high Ksv value of ∼107. While in the “on-state”, the formation of the aptamer/hemin complex recovers the fluorescence intensity. The fluorescent switch is sensitive and selective to hemin. To testify the universality and practicality of the fluorescent switch, a series of label-free DNA-related sensing platforms are developed, containing three DNA sensing strategies and one ATP recognition strategy. The fluorescent switch developed is simple, sensitive, and universal, which extends applications of the anionic conjugated polymers.

Fluorene-Based Copolymers Containing Dinaphtho-s-indacene as New Building Blocks for High-Efficiency and Color-Stable Blue LEDs

Co-reporter:Xin Guo;Yanxiang Cheng;Zhiyuan Xie;Yanhou Geng;Xiabin Jing;Fosong Wang

Macromolecular Rapid Communications 2009 Volume 30( Issue 9-10) pp:816-825

Publication Date(Web):

DOI:10.1002/marc.200800765

Oligoaniline-Functionalized terpyridine ligands and their ruthenium(II) complexes: synthesis, spectroscopic property and redox behavior

Co-reporter:Dongfang Qiu, Yanxiang Cheng and Lixiang Wang

Dalton Transactions 2009 (Issue 17) pp:3247-3261

Publication Date(Web):13 Mar 2009

DOI:10.1039/B820392J

A series of oligoaniline-functionalized mono- and bis-topic terpyridine ligands, i.e. C6H5[N(R)C6H4]nTPY (R = H, butyl, tert-butyloxycarbonyl; n = 1–4; TPY = 2,2′:6′,2″-terpyridyl) and TPYC6H4[N(R)C6H4]mTPY (R = H, tert-butyloxycarbonyl; m = 2, 4), and the corresponding mono- and bis-nuclear ruthenium(II) complexes have been synthesized and verified. The spectroscopic results indicate that two kinds of π–π* transitions from TPY and oligoaniline fragments of ligands strongly shift to lower energy, and the metal-to-ligand charge-transfer transition (1MLCT) bands of all obtained complexes are considerably red-shifted (Δλmax = 22–64 nm) and their intensities become much more intense (approximately 4–6 times), compared with those of the reported complex [Ru(TPY)2]2+. Moreover, the spectroscopic properties of the ligands and complexes with longer oligoaniline units (n = 3, 4) are markedly influenced by the external stimulus, such as the oxidation and proton acid doping. The characteristic absorption bands in the visual and near infrared (NIR) scales demonstrate the presence of various oxidized and doped states of the oligoaniline unit. All complexes show multiplicate redox processes based on metal center, oligoaniline and terpyridine units. The potential shifts suggest the donor and acceptor (D–A) interaction between the oligoaniline unit and the bis(terpyridine)–Ru2+ center.

Hierarchical Self-Assembled Nanostructures from the Organic n-Type Semiconductor Hexaazatrinaphthylene

Co-reporter:Baoxiang Gao ;Jingjing Li;Meiye Li;Yanxiang Cheng

ChemPhysChem 2009 Volume 10( Issue 18) pp:3197-3200

Publication Date(Web):

DOI:10.1002/cphc.200900562

Bifunctional Green Iridium Dendrimers with a Self-Host Feature for Highly Efficient Nondoped Electrophosphorescent Devices

Co-reporter:Junqiao Ding Dr.;Bin Wang;Zhengyu Yue ;Bing Yao;Zhiyuan Xie ;Yanxiang Cheng ;Xiabin Jing ;Fosong Wang

Angewandte Chemie 2009 Volume 121( Issue 36) pp:6792-6794

Publication Date(Web):

DOI:10.1002/ange.200902954

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Co-reporter:Dongfang Qiu, Jiang Wu, Zhiyuan Xie, Yanxiang Cheng, Lixiang Wang

Journal of Organometallic Chemistry 2009 694(5) pp: 737-746

Publication Date(Web):

DOI:10.1016/j.jorganchem.2008.12.007

Effect of ancillary ligands on the properties of heteroleptic green iridium dendrimers functionalized with carbazole dendrons

Co-reporter:Junqiao Ding, Jianhong Lü, Yanxiang Cheng, Zhiyuan Xie, Lixiang Wang, Xiabin Jing, Fosong Wang

Journal of Organometallic Chemistry 2009 694(17) pp: 2700-2704

Publication Date(Web):

DOI:10.1016/j.jorganchem.2009.03.040

Bifunctional Green Iridium Dendrimers with a Self-Host Feature for Highly Efficient Nondoped Electrophosphorescent Devices

Co-reporter:Junqiao Ding Dr.;Bin Wang;Zhengyu Yue ;Bing Yao;Zhiyuan Xie ;Yanxiang Cheng ;Xiabin Jing ;Fosong Wang

Angewandte Chemie International Edition 2009 Volume 48( Issue 36) pp:6664-6666

Publication Date(Web):

DOI:10.1002/anie.200902954

White Electroluminescence from a Star-like Polymer with an Orange Emissive Core and Four Blue Emissive Arms

Co-reporter:Jun Liu;Yanxiang Cheng;Zhiyuan Xie;Yanhou Geng;Xiabin Jing;Fosong Wang

Advanced Materials 2008 Volume 20( Issue 7) pp:1357-1362

Publication Date(Web):

DOI:10.1002/adma.200701705

Solution-Processible Red Iridium Dendrimers based on Oligocarbazole Host Dendrons: Synthesis, Properties, and their Applications in Organic Light-Emitting Diodes

Co-reporter:Junqiao Ding;Jianhong Lü;Yanxiang Cheng;Zhiyuan Xie;Xiabin Jing ;Fosong Wang

Advanced Functional Materials 2008 Volume 18( Issue 18) pp:2754-2762

Publication Date(Web):

DOI:10.1002/adfm.200800259

Abstract

A series of novel red-emitting iridium dendrimers functionalized with oligocarbazole host dendrons up to the third generation (red-G3) have been synthesized by a convergent method, and their photophysical, electrochemical, and electroluminescent properties have been investigated. In addition to controlling the intermolecular interactions, oligocarbazole-based dendrons could also participate in the electrochemical and charge-transporting process. As a result, highly efficient electrophosphorescent devices can be fabricated by spin-coating from chlorobenzene solution in different device configurations. The maximum external quantum efficiency (EQE) based on the non-doped device configuration increases monotonically with increasing dendron generation. An EQE as high as 6.3% was obtained as for the third generation dendrimer red-G3, which is about 30 times higher than that of the prototype red-G0. Further optimization of the device configuration gave an EQE of 11.8% (13.0 cd A⁻¹, 7.2 lm W⁻¹) at 100 cd m⁻² with CIE coordinates of (0.65, 0.35). The state-of-the-art performance indicated the potential of these oligocarbazole-based red iridium dendrimers as solution processible emissive materials for organic light-emitting diode applications.

Highly efficient red electroluminescent polymers with dopant/host system and molecular dispersion feature: polyfluorene as the host and 2,1,3-benzothiadiazole derivatives as the red dopant

Co-reporter:Jun Liu, Lei Chen, Shiyang Shao, Zhiyuan Xie, Yanxiang Cheng, Yanhou Geng, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2008 vol. 18(Issue 3) pp:319-327

Publication Date(Web):23 Nov 2007

DOI:10.1039/B712562C

By selecting polyfluorene as the polymer host, choosing 2,1,3-benzothiadiazole derivative moieties as the red dopant units and covalently attaching 0.3 mol% of the dopant units to the side chain of the polymer host, we developed a novel series of red electroluminescent polymers of dopant/host system with molecular dispersion feature. Their EL spectra exhibited predominant red emission from the dopant units because of the energy transfer and charge trapping from the polymer backbone to the dopant units. The emission wavelength of the polymers could be tuned by modifying the chemical structures of the dopant units. Single-layer devices (device configuration: ITO/PEDOT : PSS/polymer/Ca/Al) of these polymers emitted red light with a peak at 615 nm, a luminous efficiency of 5.04 cd A−1 and an external quantum efficiency of 3.47%, or emitted deep-red light with a peak at 650 nm, a luminous efficiency of 1.70 cd A−1 and an external quantum efficiency of 2.75%. Their high EL efficiencies were due to the energy transfer and charge trapping from the host to the dopant units as well as the molecular dispersion of the dopant units in the host. Increase of the dopant unit content led to increased turn-on voltages and decreased EL efficiencies of the resulting devices.

Blue electroluminescent polymers with dopant–host systems and molecular dispersion features: polyfluorene as the deep blue host and 1,8-naphthalimide derivative units as the light blue dopants

Co-reporter:Jun Liu, Jianxin Cao, Shiyang Shao, Zhiyuan Xie, Yanxiang Cheng, Yanhou Geng, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2008 vol. 18(Issue 14) pp:1659-1666

Publication Date(Web):21 Feb 2008

DOI:10.1039/B716234K

We developed a series of highly efficient blue electroluminescent polymers with dopant–host systems and molecular dispersion features by selecting 1,8-naphthalimide derivatives as the light blue emissive dopant units, choosing polyfluorene as the deep blue emissive polymer host and covalently attaching the dopant units to the side chain of the polymer host. The polymers' EL spectra exhibited both deep blue emission from the polymer host and light blue emission from the dopant units because of the energy transfer and charge trapping from the polymer host to the dopant units. By modifying the chemical structures of the dopant units, we controlled the energy transfer and charge trapping from the polymer host to the dopant units and consequently tuned the emission colors of the resulting polymers. Thermally annealed single-layer devices (ITO/PEDOT/polymer/Ca/Al) based on these polymers emitted deep blue light with a luminous efficiency of 2.89 cd A−1, a power efficiency of 2.01 lm W−1 and CIE coordinates (0.16, 0.17), or emitted sky-blue light with a luminous efficiency of 6.84 cd A−1, a power efficiency of 4.28 lm W−1 and CIE coordinates (0.15, 0.22). Their excellent EL performances were due to the energy transfer and charge trapping from the polymer host to the highly fluorescent dopant units.

Phosphonate-Functionalized Polyfluorene as a Highly Water-Soluble Iron(III) Chemosensor

Co-reporter:Chuanjiang Qin, Yanxiang Cheng, Lixiang Wang, Xiabin Jing and Fosong Wang

Macromolecules 2008 Volume 41(Issue 21) pp:7798-7804

Publication Date(Web):October 10, 2008

DOI:10.1021/ma801282m

An anionic, phosphonate-functionalized polyfluorene, i.e., poly(9,9-bis(3′-phosphatepropyl)fluorene-alt-1,4-phenylene) sodium salt (PFPNa), has been synthesized by copolymerization of phosphonic acid-substituted 2,7-dibromofluorene and phenyldiboronic ester via direct Suzuki polycondensation reaction in DMF/water. Polymer PFPNa is highly soluble and emissive in water with a solubility of 60 mg/mL and a photoluminescence quantum yield of 75%. The absorption and fluorescence spectra of PFPNa are strongly dependent on pH value owing to the partial protonation of phosphate groups and the aggregation of the polymer chains. In aqueous media polymer PFPNa shows high sensitivity and selectivity for Fe3+. A 400-fold fluorescence quenching was achieved upon adding Fe3+ into its aqueous solution. Most importantly, ultrathin multilayer films constructed by alternatively depositing polyanionic PFPNa and polycationic poly(diallyldimethylamine) via the layer-by-layer (LbL) self-assembling method are stable and highly sensitive to Fe3+ with a sensitivity up to 10−7 M.

Synthesis, characterization, and electroluminescence of PPV copolymers containing electron and hole-transporting units

Co-reporter:Shidi Xun;Quanguo Zhou;Hongchao Li;Dongge Ma;Xiabin Jing ;Fosong Wang

Journal of Polymer Science Part A: Polymer Chemistry 2008 Volume 46( Issue 5) pp:1566-1576

Publication Date(Web):

DOI:10.1002/pola.22489

Abstract

Three series of poly(phenylene vinylene) (PPV) derivatives containing hole-transporting triphenylamine derivatives [N-(4-octoxylphenyl)diphenylamine, N,N′-di(4-octyloxylphenyl)-N,N′-diphenyl-1,4-phenylenediamine, and N,N′-di(4-octoxylphenyl)-N,N′-diphenylbenzidine] (donor) and electron-transporting oxadiazole unit (2,5-diphenyl-1,3,4-oxadiazole) (acceptor) in the main chain were synthesized by improved Wittig copolymerization. The resulting donor–acceptor (D-A) polymers are readily soluble in common organic solvents, such as chloroform, dichloroethane, THF, and toluene. The polymers containing oxadiazole group exhibit good thermal stability with 5% weight loss above 400 °C. The intramolecular charge-transfer was observed in these D-A polymers. In comparison with corresponding polymers without oxadiazole unit, the single-layer devices based on the D-A polymers showed much improved electroluminescent properties, because of the balanced charge injection and transport. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1566–1576, 2008

White Electroluminescence from a Single Polymer System: Improved Performance by Means of Enhanced Efficiency and Red-Shifted Luminescence of the Blue-Light-Emitting Species

Co-reporter:J. Liu;S. Y. Shao;L. Chen;Z. Y. Xie;Y. X. Cheng;Y. H. Geng;L. X. Wang;X. B. Jing;F. S. Wang

Advanced Materials 2007 Volume 19(Issue 14) pp:1859-1863

Publication Date(Web):18 JUN 2007

DOI:10.1002/adma.200602942

High-efficiency white electroluminescence from a single polymer is achieved by enhancing the electroluminescence efficiency and effecting a red-shift in the emission spectrum of the blue emissive species. A single-layer device of the resultant polymer exhibits a higher luminous efficiency than the nonmodified species (12.8 cd A^–1, see figure) and an external quantum efficiency of 5.4 % with CIE coordinates of (0.31,0.36), exemplifying the success of the reported methodology.

Molecular Design on Highly Efficient White Electroluminescence from a Single-Polymer System with Simultaneous Blue, Green, and Red Emission

Co-reporter:Y. X. Cheng;Z. Y. Xie;J. Liu;L. X. Wang;Y. H. Geng;F. S. Wang;X. B. Jing

Advanced Materials 2007 Volume 19(Issue 4) pp:531-535

Publication Date(Web):24 JAN 2007

DOI:10.1002/adma.200601580

A highly efficient white electroluminescent polymer with simultaneous blue, green, and red emission is reported, developed using a dopant/host strategy by covalently attaching both a green- and a red-light-emitting dopant to the side chain of a blue-light-emitting polymer host (see figure). In a single-layer device a maximum luminance efficiency of 7.3 cd A^–1 with CIE coordinates of (0.31,0.32) is achieved.

Novel Heteroleptic CuI Complexes with Tunable Emission Color for Efficient Phosphorescent Light-Emitting Diodes

Co-reporter:Q. Zhang;J. Ding;Y. Cheng;L. Wang;Z. Xie;X. Jing;F. Wang

Advanced Functional Materials 2007 Volume 17(Issue 15) pp:

Publication Date(Web):31 AUG 2007

DOI:10.1002/adfm.200601053

A series of orange-red to red phosphorescent heteroleptic Cu^I complexes (the first ligand: 2,2′-biquinoline (bq), 4,4′-diphenyl-2,2′-biquinoline (dpbq) or 3,3′-methylen-4,4′-diphenyl-2,2′-biquinoline (mdpbq); the second ligand: triphenylphosphine or bis[2-(diphenylphosphino)phenyl]ether (DPEphos)) have been synthesized and fully characterized. With highly rigid bulky biquinoline-type ligands, complexes [Cu(mdpbq)(PPh₃)₂](BF₄) and [Cu(mdpbq)(DPEphos)](BF₄) emit efficiently in 20 wt % PMMA films with photoluminescence quantum yield of 0.56 and 0.43 and emission maximum of 606 nm and 617 nm, respectively. By doping these complexes in poly(vinyl carbazole) (PVK) or N-(4-(carbazol-9-yl)phenyl)-3,6-bis(carbazol-9-yl) carbazole (TCCz), phosphorescent organic light-emitting diodes (OLEDs) were fabricated with various device structures. The complex [Cu(mdpbq)(DPEphos)](BF₄) exhibits the best device performance. With the device structure of ITO/PEDOT/TCCz:[Cu(mdpbq)(DPEphos)](BF₄) (15 wt %)/TPBI/LiF/Al (III), a current efficiency up to 6.4 cd A^–1 with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.61, 0.39) has been realized. To our best knowledge, this is the first report of efficient mononuclear Cu^I complexes with red emission.

Green light-emitting polyfluorenes with improved color purity incorporated with 4,7-diphenyl-2,1,3-benzothiadiazole moieties

Co-reporter:Jun Liu, Laju Bu, Jinpeng Dong, Quanguo Zhou, Yanhou Geng, Dongge Ma, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2007 vol. 17(Issue 27) pp:2832-2838

Publication Date(Web):30 Apr 2007

DOI:10.1039/B700004A

By incorporating 4,7-diphenyl-2,1,3-benzothiadiazole instead of 2,1,3-benzothiadiazole into the backbone of polyfluorene, we developed a novel series of green light-emitting polymers with much improved color purity. Compared with the state-of-the-art green light-emitting polymer, poly(fluorene-co-benzothiadiazole) (λmax = 537 nm), the resulting polymers (λmax = 521 nm) showed 10–20 nm blueshifted electroluminescence (EL) spectra and greatly improved color purity because the insertion of two phenylene units between the 2,1,3-benzothiadiazole unit and the fluorene unit reduced the effective conjugation length in the vicinity of the 2,1,3-benzothiadiazole unit. As a result, the resulting polymers emitted pure green light with CIE coordinates of (0.29, 0.63), which are very close to (0.26, 0.65) of standard green emission demanded by the National Television System Committee (NTSC). Moreover, the insertion of the phenylene unit did not affect the photoluminescence (PL) and EL efficiencies of the resulting polymers. PL quantum efficiency in solid films up to 0.82 was demonstrated. Single-layer devices (ITO/PEDOT/polymer/Ca/Al) of these polymers exhibited a turn-on voltage of 4.2 V, luminous efficiency of 5.96 cd A−1 and power efficiency of 2.21 lm W−1. High EL efficiencies and good color purities made these polymers very promising for display applications.

Synthesis and characterization of white-light-emitting polyfluorenes containing orange phosphorescent moieties in the side chain

Co-reporter:Chongyu Mei;Junqiao Ding;Bing Yao;Yanxiang Cheng;Yanhou Geng;Zhiyuan Xie

Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 9) pp:1746-1757

Publication Date(Web):20 MAR 2007

DOI:10.1002/pola.21942

Two orange phosphorescent iridium complex monomers, 9-hexyl-9-(iridium (III)bis(2-(4′-fluorophenyl)-4-phenylquinoline-N,C^2′)(tetradecanedionate-11,13))-2,7-dibromofluorene (Br-PIr) and 9-hexyl-9-(iridium(III)bis(2-(4′-fluorophenyl)-4-methylquinoline-N,C^2′)(tetradecanedionate-11,13))-2,7-dibromofluorene (Br-MIr), were successfully synthesized. The Suzuki polycondensation of 2,7-bis(trimethylene boronate)-9,9-dioctylfluorene with 2,7-dibromo-9,9-dioctylfluorene and Br-PIr or Br-MIr afforded two series of copolymers, PIrPFs and MIrPFs, in good yields, in which the concentrations of the phosphorescent moieties were kept small (0.5–3 mol % feed ratio) to realize incomplete energy transfer. The photoluminescence (PL) of the copolymers showed blue- and orange-emission peaks. A white-light-emitting diode with a configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/PIr05PF (0.5 mol % feed ratio of Br-PIr)/Ca/Al exhibited a luminous efficiency of 4.49 cd/A and a power efficiency of 2.35 lm/W at 6.0 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.46, 0.33). The CIE coordinates were improved to (0.34, 0.33) when copolymer MIr10PF (1.0 mol % feed ratio of Br-MIr) was employed as the white-emissive layer. The strong orange emission in the electroluminescence spectra in comparison with PL for these kinds of polymers was attributed to the additional contribution of charge trapping in the phosphorescent dopants. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 45: 1746–1757, 2007

Cover Picture: White Electroluminescence from a Single-Polymer System with Simultaneous Two-Color Emission: Polyfluorene as the Blue Host and a 2,1,3-Benzothiadiazole Derivative as the Orange Dopant (Adv. Funct. Mater. 7/2006)

Co-reporter:J. Liu;Q. G. Zhou;Y. X. Cheng;Y. H. Geng;L. X. Wang;D. G. Ma;X. B. Jing;F. S. Wang

Advanced Functional Materials 2006 Volume 16(Issue 7) pp:

Publication Date(Web):21 APR 2006

DOI:10.1002/adfm.200690024

New single-polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3-benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λ_max = 421 nm/445 nm) and orange emission (λ_max = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light-emitting diodes (PLEDs) based on the single-polymer systems has been investigated. The introduction of the highly efficient 4,7-bis(4-(N-phenyl-N-(4-methylphenyl)amino)phenyl)-2,1,3-benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single-layer device fabricated in air (indium tin oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure-white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m^–2, luminance efficiency of 7.30 cd A^–1, and power efficiency of 3.34 lm W^–1 can be obtained. This device is approximately two times more efficient than that utilizing a single polyfluorene containing 1,8-naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single-layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn-on voltage of 3.5 V, luminance efficiency of 8.99 cd A^–1, power efficiency of 5.75 lm W^–1, external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m^–2. This performance is roughly comparable to that of white organic light-emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.

White Electroluminescence from a Single-Polymer System with Simultaneous Two-Color Emission: Polyfluorene as the Blue Host and a 2,1,3-Benzothiadiazole Derivative as the Orange Dopant

Co-reporter:J. Liu;Q. G. Zhou;Y. X. Cheng;Y. H. Geng;L. X. Wang;D. G. Ma;X. B. Jing;F. S. Wang

Advanced Functional Materials 2006 Volume 16(Issue 7) pp:

Publication Date(Web):24 MAR 2006

DOI:10.1002/adfm.200500761

Highly Efficient Electroluminescence from Green-Light-Emitting Electrochemical Cells Based on CuI Complexes

Co-reporter:Q. Zhang;Q. Zhou;Y. Cheng;L. Wang;D. Ma;X. Jing;F. Wang

Advanced Functional Materials 2006 Volume 16(Issue 9) pp:

Publication Date(Web):4 MAY 2006

DOI:10.1002/adfm.200500691

The complexes [Cu(dnbp)(DPEphos)]⁺(X^–) (dnbp and DPEphos are 2,9-di-n-butyl-1,10-phenanthroline and bis[2-(diphenylphosphino)phenyl]ether, respectively, and X^– is BF₄^–, ClO₄^–, or PF₆^–) can form high-quality films with photoluminescence quantum yields of up to 71 ± 7 %. Their electroluminescent properties are studied using the device structure indium tin oxide (ITO)/complex/metal cathode. The devices emit green light efficiently, with an emission maximum of 523 nm, and work in the mode of light-emitting electrochemical cells. The response time of the devices greatly depends on the driving voltage, the counterions, and the thickness of the complex film. After pre-biasing at 25 V for 40 s, the devices turn on instantly, with a turn-on voltage of ca. 2.9 V. A current efficiency of 56 cd A^–1 and an external quantum efficiency of 16 % are realized with Al as the cathode. Using a low-work-function metal as the cathode can significantly enhance the brightness of the device almost without affecting the turn-on voltage and current efficiency. With a Ca cathode, a brightness of 150 cd m^–2 at 6 V and 4100 cd m^–2 at 25 V is demonstrated. The electroluminescent performance of these types of complexes is among the best so far for transition metal complexes with counterions.

Highly Efficient Pure-White-Light-Emitting Diodes from a Single Polymer: Polyfluorene with Naphthalimide Moieties

Co-reporter:G. L. Tu;C. Y. Mei;Q. G. Zhou;Y. X. Cheng;Y. H. Geng;L. X. Wang;D. G. Ma;X. B. Jing;F. S. Wang

Advanced Functional Materials 2006 Volume 16(Issue 1) pp:

Publication Date(Web):5 DEC 2005

DOI:10.1002/adfm.200500028

Light-emitting diodes exhibiting efficient pure-white-light electroluminescence have been successfully developed by using a single polymer: polyfluorene derivatives with 1,8-naphthalimide chromophores chemically doped onto the polyfluorene backbones. By adjusting the emission wavelength of the 1,8-naphthalimide components and optimizing the relative content of 1,8-naphthalimide derivatives in the resulting polymers, white-light electroluminescence from a single polymer, as opposed to a polymer blend, has been obtained in a device with a configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene)(50 nm)/polymer(80 nm)/Ca(10 nm)/Al(100 nm). The device exhibits Commission Internationale de l'Eclairage coordinates of (0.32,0.36), a maximum brightness of 11 900 cd m^–2, a current efficiency of 3.8 cd A^–1, a power efficiency of 2.0 lm W^–1, an external quantum efficiency of 1.50 %, and quite stable color coordinates at different driving voltages, even at high luminances of over 5000 cd m^–2.

Highly efficient green light emitting polyfluorene incorporated with 4-diphenylamino-1,8-naphthalimide as green dopant

Co-reporter:Jun Liu, Guoli Tu, Quanguo Zhou, Yanxiang Cheng, Yanhou Geng, Lixiang Wang, Dongge Ma, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2006 vol. 16(Issue 15) pp:1431-1438

Publication Date(Web):25 Jan 2006

DOI:10.1039/B514359D

The dopant/host methodology, which enables efficient tuning of emission color and enhancement of the electroluminescence (EL) efficiency of organic light emitting diodes (OLEDs) based on small molecules, is applied to the design and synthesis of highly efficient green light emitting polymers. Highly efficient green light emitting polymers were obtained by covalently attaching just 0.3–1.0 mol% of a green dopant, 4-(N,N-diphenyl) amino-1,8-naphthalimide (DPAN), to the pendant chain of polyfluorene (the host). The polymers emit green light and exhibit a high photoluminescence (PL) quantum yield of up to 0.96 in solid films, which is attributed to the energy transfer from the polyfluorene host to the DPAN dopant unit. Single layer devices (device configuration: ITO/PEDOT/Polymer/Ca/Al) of the polymers exhibit a turn on voltage of 4.8 V, luminance efficiency of 7.43 cd A−1, power efficiency of 2.96 lm W−1 and CIE coordinates at (0.26, 0.58). The good device performance can be attributed to the energy transfer and charge trapping from the polyfluorene host to the DPAN dopant unit as well as the molecular dispersion of the dopant in the host. The device performance is fairly comparable to that of state-of-the-art green light emitting poly(fluorene-co-benzothiadiazole), indicating that the covalently attached dopant/host polymer system is very promising for the development of highly efficient electroluminescent polymers of tunable emission color.

New fluorescent dipolar pyrazine derivatives for non-doped red organic light-emitting diodes

Co-reporter:Baoxiang Gao, Quanguo Zhou, Yanhou Geng, Yanxiang Cheng, Dongge Ma, Zhiyuan Xie, Lixiang Wang, Fosong Wang

Materials Chemistry and Physics 2006 Volume 99(2–3) pp:247-252

Publication Date(Web):10 October 2006

DOI:10.1016/j.matchemphys.2005.10.020

Dipolar fluorescent compounds containing electron-accepting pyrazine-2,3-dicarbonitrile and electron-donating arylamine moiety have been designed and synthesized. The optical and electrochemical properties of these compounds can be adjusted by changing π-bridge length and the donor (D) strength. Organic light-emitting devices based on these compounds are fabricated. Saturated red emission of (0.67, 0.33) and the external quantum efficiency as high as 1.41% have been demonstrated for one of these compounds.

The First Single Polymer with Simultaneous Blue, Green, and Red Emission for White Electroluminescence

Co-reporter:J. Liu;Q. G. Zhou;Y. X. Cheng;Y. H. Geng;L. X. Wang;D. G. Ma;X. B. Jing;F. S. Wang

Advanced Materials 2005 Volume 17(Issue 24) pp:

Publication Date(Web):3 NOV 2005

DOI:10.1002/adma.200501850

A light-emitting polymer with simultaneous blue (λ_max = 445 nm), green (λ_max = 515 nm), and red light (λ_max = 624 nm) emission for bias-independent white electroluminescence is reported (see Figure). The polymer is synthesized by covalently attaching a green-light-emissive and a red-light-emissive chromophore to a macromolecule with blue-light emission. White-light color coordinates of (0.31, 0.34) and a luminance efficiency of 1.59 cd A^–1 are obtained.

Highly efficient phosphorescent bis-cyclometalated iridium complexes based on quinoline ligands

Co-reporter:Junqiao Ding, Jia Gao, Qi Fu, Yanxiang Cheng, Dongge Ma, Lixiang Wang

Synthetic Metals 2005 Volume 155(Issue 3) pp:539-548

Publication Date(Web):15 December 2005

DOI:10.1016/j.synthmet.2005.08.034

The synthesis and electrochemical and photophysical study of a series of bis-cyclometalated iridium(III) complexes based on quinoline ligands have been carried out. These complexes are found to emit red-orange to deep red phosphorescence with high quantum yield and short lifetime. The red organic light-emitting diodes (OLEDs) with the external quantum efficiency up to 11.3% were demonstrated. Slow decay of efficiency with increasing current density was observed. These indicate that quinoline-based iridium complexes are promising candidates for efficient red emitters.

Novel hole-transporting materials based on 1,4-bis(carbazolyl)benzene for organic light-emitting devices

Co-reporter:Qian Zhang, Jiangshan Chen, Yanxiang Cheng, Lixiang Wang, Dongge Ma, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2004 vol. 14(Issue 5) pp:895-900

Publication Date(Web):20 Jan 2004

DOI:10.1039/B309630K

Novel hole-transporting molecules containing 1,4-bis(carbazolyl)benzene as a central unit and different numbers of diphenylamine moieties as the peripheral groups have been synthesized and characterized. These compounds are thermally stable with high glass transition temperatures of 141–157 °C and exhibit chemically reversible redox processes. Their amorphous state stability and hole transport properties can be significantly improved by increasing the number of diphenylamine moieties in the outer part and by controlling the symmetry of the carbazole-based molecules. These compounds can be used as good hole-transporting materials for organic electroluminescent (EL) devices. The device performance based on tri- and tetra-substituted carbazole derivatives is comparable to that of a typical 4,4′-bis[N-(1-naphthyl)-N-phenylamino] biphenyl (NPB)-based device.

Crosslinkable poly(p-phenylenevinylene) derivative

Co-reporter:Honghao Sun;Yufeng Hu;Dongge Ma;Xiabing Jing;Fosong Wang;Ze Liu

Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 9) pp:2124-2129

Publication Date(Web):19 MAR 2004

DOI:10.1002/pola.20068

To simplify the fabrication of multilayer light-emitting diodes, we prepared a p-phenylenevinylene-based polymer capped with crosslinkable styrene through a Wittig reaction. Insoluble poly(p-phenylenevinylene) derivative (PPVD) films were prepared by a thermal treatment. The photoluminescence and ultraviolet–visible (UV–vis) absorbance of crosslinked films and noncrosslinked films were studied. We also studied the solvent resistance of crosslinked PPV films with UV–vis absorption spectra and atomic force microscopy. Double-layer devices using crosslinked PPVD as an emitting layer, 2-(4-tert-butylphenyl)-5-phenyl-1,3,4-oxadiazole (PBD) in poly(methyl methacrylate) as an electron-transporting layer, and calcium as a cathode were fabricated. A maximum luminance efficiency of 0.70 cd/A and a maximum brightness of 740 cd/m² at 16 V were demonstrated. A 12-fold improvement in the luminance efficiency with respect to that of single-layer devices was realized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2124–2129, 2004

Soluble, saturated-red-light-emitting poly(p-phenylenevinylene) containing triphenylamine units and cyano groups

Co-reporter:Hongchao Li;Yufeng Hu;Yanguang Zhang;Dongge Ma;Xiabin Jing;Fosong Wang

Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 16) pp:3947-3953

Publication Date(Web):12 JUL 2004

DOI:10.1002/pola.20278

A conjugated poly(p-CN-phenylenevinylene) (PCNPV) containing both electron-donating triphenylamine units and electron-withdrawing cyano groups was prepared via Knoevenagel condensation in a good yield. Gel permeation chromatography suggested that the soluble polymer had a very high weight-average molecular weight of 309,000. A bright and saturated red emission was observed under UV excitation in solution and film. Cyclic voltammetry showed that the polymer presented quasi-reversible oxidation with a relatively low potential because of the triphenylamine unit. A single-layer indium tin oxide/PCNPV/Mg–Ag device emitted a bright red light (633 nm). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3947–3953, 2004

A hydroxyphenyloxadiazole lithium complex as a highly efficient blue emitter and interface material in organic light-emitting diodes

Co-reporter:Fushun Liang, Jiangshan Chen, Lixiang Wang, Dongge Ma, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2003 vol. 13(Issue 12) pp:2922-2926

Publication Date(Web):19 Sep 2003

DOI:10.1039/B307209F

We synthesized a hydroxyphenyloxadiazole lithium complex (LiOXD) as a blue light-emitting and electron injection/transport material to be used in double-layer organic electroluminescent devices. Devices with the concise configuration of ITO/TPD/LiOXD/Al showed bright blue EL emission centered at 468 nm with a maximum luminance of 2900 cd m−2. A current efficiency of 3.9 cd A−1 and power efficiency of 1.1 lm W−1 were obtained. LiOXD was also examined as an interface material. The efficiency of an ITO/NPB/Alq3/Al device increased considerably when LiOXD was inserted between Alq3 and aluminium. The improvement of the device characteristics with LiOXD approached that observed with the dielectric LiF salt.

Synthesis, characterization, photoluminescent and electroluminescent properties of new conjugated 2,2′-(arylenedivinylene)bis-8-substituted quinolines

Co-reporter:Fushun Liang, Jiangshan Chen, Yanxiang Cheng, Lixiang Wang, Dongge Ma, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2003 vol. 13(Issue 6) pp:1392-1399

Publication Date(Web):08 Apr 2003

DOI:10.1039/B210408C

A series of new PPV oligomers containing 8-substituted quinoline, 2,2′-(arylenedivinylene)bis-8-quinoline derivatives, were designed and synthesized via a Knoevenagel condensation reaction of quinaldine, 8-hydroxy- or 8-methoxy-quinaldine with aromatic dialdehydes. These PPV oligomers were characterized by 1H and 13C-NMR, X-ray diffraction, elemental analysis, UV-visible and fluorescence spectroscopies. The X-ray diffraction investigation showed that there are intermolecular π⋯π interactions in the solid state in 1 and 3. The optical and photoluminescent properties study demonstrated that the emission color of the resulting materials varies from blue to yellow and is dependent on the substituents (π-donor and π-acceptor groups) on both sides of the conjugated molecules and the aromatic core in the middle of the conjugated backbones. The electroluminescent devices using compounds 1–4 as the emitters and electron-transporting layers were fabricated with the structure ITO/NPB/emitter/LiF/Al. The best device performance with the maximum brightness of 5530 cd m−2 and the luminous efficiency of 2.4 cd A−1 is achieved by using compound 4, with intramolecular charge transfer character, as the emitter; these values represent a more than 5-fold improvement in brightness and efficiency compared to compound 3 without methoxy groups on the phenyl rings.

Novel bis(8-hydroxyquinoline)phenolato–aluminum complexes for organic light-emitting diodes

Co-reporter:Guang Wang, Fushun Liang, Zhiyuan Xie, Guangping Su, Lixiang Wang, Xiabin Jing, Fosong Wang

Synthetic Metals 2002 Volume 131(1–3) pp:1-5

Publication Date(Web):20 November 2002

DOI:10.1016/S0379-6779(02)00218-7

A novel series of emitting aluminum complexes containing two 8-hydroxyquinoline ligands (q) and a phenolato ligand (p) were synthesized and characterized. Double layer organic light-emitting diodes (OLEDs) were fabricated using these complexes as luminescent layers, and strong electroluminescence (EL) was observed. It was found that their emitting wavelengths were mainly determined by the first ligands (q). Cyclic voltammograms revealed a partially irreversible n-doping process and indicated that these complexes show excellent electron-transporting ability.

Novel bipolar light-emitting copolymer containing triazole and triphenylamine moieties

Co-reporter:Ze Liu;Yanguang Zhang;Yufeng Hu;Guangping Su;Dongge Ma;Xiabin Jing;Fosong Wang

Journal of Polymer Science Part A: Polymer Chemistry 2002 Volume 40(Issue 8) pp:1122-1126

Publication Date(Web):28 FEB 2002

DOI:10.1002/pola.10176

A novel triazole- and triphenylamine-containing, poly(p-phenylenevinylene)-based bipolar light-emitting copolymer, poly[4-phenyl-3,5-bi(p-vinylenephenyl)-1,2,4-triazole-alt-4,4-bi(p-vinylenephenyl)-p-2′-ethylhexyloxylphenylamine] (TAZ–TPA–PPV), has been synthesized by a Wittig reaction. The polymer yields a bright green-yellow emission and has good solubility, excellent film-forming ability, and high thermal stability, properties which make it a good candidate for polymeric light-emitting diodes.

High solubility and photoluminescence quantum yield water-soluble polyfluorenes with dendronized amino acid side chains: synthesis, photophysical, and metal ion sensing properties

Co-reporter:Chuanjiang Qin, Xiaofu Wu, Hui Tong and Lixiang Wang

Journal of Materials Chemistry A 2010 - vol. 20(Issue 37) pp:NaN7964-7964

Publication Date(Web):2010/08/20

DOI:10.1039/C0JM01094D

Color tuning of Novel 2,1,3-Naphthothiadiazole and 2,1,3-Benzoselenadiazole based D-A-D′ Type dopants to realize highly efficient saturated red emission in non-polar solvents

Co-reporter:Lei Chen, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2011 - vol. 21(Issue 28) pp:NaN10267-10267

Publication Date(Web):2011/06/03

DOI:10.1039/C1JM11204J

Synthesis and characterization of yellow-emitting electrophosphorescent polymers based on a fluorinated poly(arylene ether phosphine oxide) scaffold

Co-reporter:Shiyang Shao, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2012 - vol. 22(Issue 47) pp:NaN24855-24855

Publication Date(Web):2012/10/01

DOI:10.1039/C2JM34421A

A solution-processable phosphonate functionalized deep-blue fluorescent emitter for efficient single-layer small molecule organic light-emitting diodes

Co-reporter:Bo Chen, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Chemical Communications 2012 - vol. 48(Issue 71) pp:NaN8972-8972

Publication Date(Web):2012/07/19

DOI:10.1039/C2CC34712A

Self-host heteroleptic green iridium dendrimers: achieving efficient non-doped device performance based on a simple molecular structure

Co-reporter:Lingcheng Chen, Zhihua Ma, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Chemical Communications 2011 - vol. 47(Issue 33) pp:NaN9521-9521

Publication Date(Web):2011/07/20

DOI:10.1039/C1CC13276H

Neutral copper(I) phosphorescent complexes from their ionic counterparts with 2-(2′-quinolyl)benzimidazole and phosphine mixed ligands

Co-reporter:Junhui Min, Qisheng Zhang, Wei Sun, Yanxiang Cheng and Lixiang Wang

Dalton Transactions 2011 - vol. 40(Issue 3) pp:NaN693-693

Publication Date(Web):2010/12/02

DOI:10.1039/C0DT01031F

Oligoaniline-Functionalized terpyridine ligands and their ruthenium(II) complexes: synthesis, spectroscopic property and redox behavior

Co-reporter:Dongfang Qiu, Yanxiang Cheng and Lixiang Wang

Dalton Transactions 2009(Issue 17) pp:NaN3261-3261

Publication Date(Web):2009/03/13

DOI:10.1039/B820392J

Small molecules based on 2,7-carbazole for efficient solution-processed organic solar cells

Co-reporter:Pengcheng Li, Hui Tong, Junqiao Ding, Zhiyuan Xie and Lixiang Wang

Journal of Materials Chemistry A 2013 - vol. 1(Issue 31) pp:NaN8812-8812

Publication Date(Web):2013/05/24

DOI:10.1039/C3TA11168G

Phosphonate substituted 4,4′-bis(N-carbazolyl)biphenyl with dominant electron injection/transport ability for tuning the single-layer device performance of self-host phosphorescent dendrimer

Co-reporter:Bo Chen, Junqiao Ding, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2012 - vol. 22(Issue 44) pp:NaN23686-23686

Publication Date(Web):2012/09/21

DOI:10.1039/C2JM35526D

Co-reporter:Junqiao Ding, Qi Wang, Lei Zhao, Dongge Ma, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2010 - vol. 20(Issue 37) pp:NaN8133-8133

Publication Date(Web):2010/08/19

DOI:10.1039/C0JM00846J

Highly efficient red electroluminescent polymers with dopant/host system and molecular dispersion feature: polyfluorene as the host and 2,1,3-benzothiadiazole derivatives as the red dopant

Co-reporter:Jun Liu, Lei Chen, Shiyang Shao, Zhiyuan Xie, Yanxiang Cheng, Yanhou Geng, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2008 - vol. 18(Issue 3) pp:NaN327-327

Publication Date(Web):2007/11/23

DOI:10.1039/B712562C

Blue electroluminescent polymers with dopant–host systems and molecular dispersion features: polyfluorene as the deep blue host and 1,8-naphthalimide derivative units as the light blue dopants

Co-reporter:Jun Liu, Jianxin Cao, Shiyang Shao, Zhiyuan Xie, Yanxiang Cheng, Yanhou Geng, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2008 - vol. 18(Issue 14) pp:NaN1666-1666

Publication Date(Web):2008/02/21

DOI:10.1039/B716234K

Green light-emitting polyfluorenes with improved color purity incorporated with 4,7-diphenyl-2,1,3-benzothiadiazole moieties

Co-reporter:Jun Liu, Laju Bu, Jinpeng Dong, Quanguo Zhou, Yanhou Geng, Dongge Ma, Lixiang Wang, Xiabin Jing and Fosong Wang

Journal of Materials Chemistry A 2007 - vol. 17(Issue 27) pp:NaN2838-2838

Publication Date(Web):2007/04/30

DOI:10.1039/B700004A

(3,3'-Difluoro-[2,2'-bithiophene]-5,5'-diyl)bis(trimethylstannane)

CAS:1619967-09-7

(3,3'-Difluoro-[2,2'-bithiophene]-5,5'-diyl)bis(trimethylstannane)

CAS:1332616-80-4

4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione, 1,3-dibromo-5-(2-butyloctyl)-

CAS:1262241-50-8

4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione, 1,3-dibromo-5-(2-butyloctyl)-

Thieno[3,4-b]thiophene-2-carboxylic acid, 4,6-dibromo-3-fluoro-, 2-ethylhexyl ester

CAS:1237479-38-7

Thieno[3,4-b]thiophene-2-carboxylic acid, 4,6-dibromo-3-fluoro-, 2-ethylhexyl ester

1-Propanol, 3-(2-methoxyethoxy)-2-[(2-methoxyethoxy)methyl]-

CAS:429686-10-2

1-Propanol, 3-(2-methoxyethoxy)-2-[(2-methoxyethoxy)methyl]-

2,2'-Bipyridine, 5,5'-dibromo-3,3'-dinitro-

CAS:321844-96-6

2,2'-Bipyridine, 5,5'-dibromo-3,3'-dinitro-

CAS:161196-26-5

[60]PCBA

2,5,9,12-Tetraoxatridecane, 7-methylene-

CAS:83260-71-3

2,5,9,12-Tetraoxatridecane, 7-methylene-

CAS:75449-26-2

[2,2'-Bipyridine]-3,3'-diamine

CAS:15754-53-7

Phosphine oxide, bis(4-bromophenyl)-