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Three thiophene ring-terminated benzothieno[3,2-b]benzothiophene (BTBT) derivatives, C-C6-DBTTT, C-C12-DBTTT, and L-C12-DBTTT, were designed and synthesized, differing in the isomerization of alkyl...

A novel fused heterocycle-flanked diketopyrrolopyrrole (DPP) monomer, thieno[2,3-b]pyridine diketopyrrolopyrrole (TPDPP), was designed and synthesized. When copolymerized with 3,4-difluorothiophene using Stille coupling polymerization, the new polymer pTPDPP-TF possesses a highly planar conjugated polymer backbone due to the fused thieno[2,3-b]pyridine flanking unit that effectively alleviates the steric hindrance with both the central DPP core and the 3,4-difluorothiophene repeat unit. This new polymer exhibits a high electron affinity (EA) of −4.1 eV and was successfully utilized as an n-type polymer semiconductor for applications in organic field-effect transistors (OFETs) and all polymer solar cells. A promising n-type charge carrier mobility of 0.1 cm2 V–1 s–1 was obtained in bottom-contact, top-gate OFETs, and a power conversion efficiency (PCE) of 2.72% with a high open-circuit voltage (VOC) of 1.04 V was achieved for all polymer solar cells using PTB7-Th as the polymer donor.

Two donor–acceptor conjugated polymers with azaisoindigo as acceptor units and bithiophene and terthiophene as donor units have been synthesized by Stille polymerization. These two polymers have been successfully applied in field-effect transistors and polymer solar cells. By changing the donor component of the conjugated polymer backbone from bithiophene to terthiophene, the density of thiophene in the backbone is increased, manifesting as a decrease in both ionization potential and in electron affinity. Therefore, the charge transport in field-effect transistors switches from ambipolar to predominantly hole transport behavior. PAIIDTT exhibits hole mobility up to 0.40 cm2/Vs and electron mobility of 0.02 cm2/Vs, whereas PAIIDTTT exhibits hole mobility of 0.62 cm2/Vs. Polymer solar cells were fabricated based on these two polymers as donors with PC61BM and PC71BM as acceptor where PAIIDTT shows a modest efficiency of 2.57% with a very low energy loss of 0.55 eV, while PAIIDTTT shows a higher efficiency of 6.16% with a higher energy loss of 0.74 eV. Our results suggest that azaisoindgo is a useful building block for the development of efficient polymer solar cells with further improvement possibility by tuning the alternative units on the polymer backbone. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2691–2699.

Two new alternating copolymers, PAIIDBT and PAIIDSe have been prepared by incorporating a highly electron deficient azaisoindigo core. The molecular structure and packing of the monomer is determined from the single crystal X-ray diffraction. Both polymers exhibit high EAs and highly planar polymer backbones. When polymers are used as the semiconducting channel for solution-processed thin film transistor application, good properties are observed. A–A type PAIIDBT exhibits unipolar electron mobility as high as 1.0 cm2 V−1 s−1, D–A type PAIIDSe exhibits ambipolar charge transport behavior with predominately electron mobility up to 0.5 cm2 V−1 s−1 and hole mobility to 0.2 cm2 V−1 s−1. The robustness of the extracted mobility values are also commented on in detail. Molecular orientation, thin film morphology and energetic disorder of both polymers are systematically investigated.

A series of new 9,10-diphenylanthracene-based, 2,6-linked blue-light-emitting copolymers bearing hole- or electron-transporter as well as bulky substituent were successfully synthesized. Photophysical, thermal, electrochemical, and electroluminescence (EL) properties of these copolymers were studied and characterized. Bright and efficient blue fluorescence in the solid state was achieved by incorporating bulky substituent into the copolymer backbone. Both hole- and electron-transport-substituted copolymers apparently enhanced the electroluminescent performance of their polymeric light-emitting diodes (PLEDs). A diphenylvinyl-bearing copolymer (pDPV) PLED exhibited sky-blue EL (λmaxEL = 473 nm, CIEx,y = 0.16, 0.28) with peak luminous efficiency of 2.21 cd/A; a N-carbazole bearing copolymer (pCBZ) PLED displayed a blue EL (λmaxEL = 469 nm, CIEx,y = 0.15, 0.22) with peak luminous efficiency of 2.15 cd/A. OXD-7 (1,3-bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl)benzene) as an electron-transporting dopant wa...

All non-dopant white organic light-emitting diodes (WOLEDs) have been realized by using solid state highly fluorescent red bis(4-( N -(1-naphthyl)phenylamino)phenyl)fumaronitrile ( NPAFN ) and amorphous bipolar blue light-emitting 2-(4-diphenylamino)phenyl-5-(4-triphenylsilyl)phenyl-1,3,4-oxadiazole ( TPAOXD ), together with well known green fluorophore tris(8-hydroxyquinolinato)aluminum ( Alq 3 ). The fabrication of multilayer WOLEDs did not involve the hard-to-control doping process. Two WOLEDs, Device B and C, different in layer thickness of Alq 3 , 30 and 15 nm, respectively, emitted strong electroluminescence (EL) as intense as 25,000 cd/m 2 . For practical solid state lighting application, EL intensity exceeding 1000 cd/m 2 was achieved at current density of 18–19 mA/cm 2 or driving voltage of 6.5–8 V and the devices exhibited external quantum efficiency ( η ext ) of 2.6–2.9% corresponding to power efficiency ( η P ) of 2.1–2.3 lm/W at the required brightness. The thickness of Alq 3 layer is decisive in color quality of non-dopant WOLEDs. The Commission Internationale de l’Eclairage (CIE) coordinates of fairly white EL of Device B varied only little from (0.34, 0.39) to (0.34, 0.38) at driving voltage between 6 and 14 V. Device B exhibited relatively high color rendering indexes (CRIs) in the range of 74–81, which were essentially voltage-independent. The other WOLED, Device C, showed even better color purity of white EL (CIE x , y = 0.34, 0.31) along with higher CRI of 83 at 8 V, although higher voltage deteriorated the color quality of WOLED.

A newly synthesized benzo(1,2-b:4,5-b')dithiophene-based low band-gap copolymer pBCN is amenable to solvent annealing in the fabrication of organic photovoltaics, of which power conversion efficiency is greatly improved to 4.2% with PC(61)BM or 4.9% with PC(71)BM.

We report a novel solution-processable high molecule iridium complex, bis[5-methyl-7-trifluoro methyl-5H-enzo(c)(1,5)naphthyridin-6-one]iridium(picolinate) (CF3BNO), that exhibits a relatively short excited-state lifetime (0.30 μs) and extremely high quantum yield (95%). Current efficiency of 89.1 cd A−1 at 100 cd m−2 was obtained by using the CF3BNO complex to fabricate a blue-green light-emitting device.

We report a detailed comparison of absorption spectroscopy, electrochemistry, DFT calculations, field-effect charge mobility, as well as organic photovoltaic characteristics between thiophene- and selenophene-bridged donor–acceptor low-band-gap copolymers. In these copolymers, a significant reduction of the band-gap energy was observed for selenophene-bridged copolymers by UV-visible absorption spectroscopy and cyclic voltammetry. Field-effect charge mobility studies reveal that the enhanced hole mobility of the selenophene-bridged copolymers hinges on the solubilising alkyl side chain of the copolymers. Both cyclic voltammetry experiments and theoretical calculations showed that the decreased band-gap energy is mainly due to the lowering of the LUMO energy level, and the raising of the HOMO energy level is just a secondary cause. These results are reflected in a significant increase of the short circuit current density (JSC) but a slight decrease of the open circuit voltage (VOC) of their bulk-heterojunction organic photovoltaics (BHJ OPVs), of which the electron donor materials are a selenophene-bridged donor–acceptor copolymer: poly{9-dodecyl-9H-carbazole-alt-5,6-bis(dodecyloxy)-4,7-di(selenophen-2-yl) benzo[c][1,2,5]-thiadiazole} (pCzSe) or poly{4,8-bis(2-ethylhexyloxy)benzo[1,2-b;4,5-b′]dithiophene-alt-5,6-bis(dodecyloxy)-4,7-di(selenophen-2-yl)benzo[c][1,2,5]-thiadiazole} (pBDTSe), or a thiophene-bridged donor–acceptor copolymer: poly{9-dodecyl-9H-carbazole-alt-5,6-bis(dodecyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole} (pCzS) or poly{4,8-bis(2-ethylhexyloxy)benzo[1,2-b;4,5-b′]dithiophene-alt-5,6-bis(dodecyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole} (pBDTS); the electron acceptor material is [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Judging from our device data, the potential Se–Se interactions of the selenophene-bridged donor–acceptor copolymers, which is presumably beneficial for the fill factor (FF) of BHJ OPVs, is rather susceptible to the device fabrication conditions.