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A new alkoxy substituted phenyl-containing hyperbranched conjugated poly(phenylene vinylene) (Hyper-PMEH-PPV) has been synthesized through the well-known Wittig polycondensation reaction. The synthesized Hyper-PMEH-PPV was completely soluble in common organic solvents and exhibited good thermal stability up to 383 °C. The photophysical properties of Hyper-PMEH-PPV are investigated and compared with a linear conjugated poly(para-phenylene vinylene) (Linear-PMEH-PPV) and well-known MEH-PPV. An absorption maximum of Hyper-PMEH-PPV film was determined at 395 nm which was far blue-shifted than that of Linear-PMEH-PPV (428 nm). Hyper-PMEH-PPV film showed green photoluminescence (PL) peak at 513 nm. In addition, Hyper-PMEH-PPV film exhibited almost no excimer or aggregate emission peaks even when the polymer film was annealed at 80 °C for 30 min in air condition. No undesirable emissions from Hyper-PMEH-PPV film are due to the inhibition of intermolecular interaction by the introduction of the hyperbranched network into the poly(phenylene vinylene) backbone. [ABSTRACT FROM AUTHOR]

A new wide bandgap (WBG) conjugated polymer diO-PBDB-T containing alkoxy substituted thiophene spacer was designed and synthesized for application as a donor in nonfullerene acceptor (NFA) based polymer solar cells (PSCs), to investigate the effect of alkoxy substitution on the photovoltaic performance. The suggested polymer diO-PBDB-T showed good complementary absorption spectra with a bandgap of 1.96 eV, a highest occupied molecular orbital (HOMO) energy level of −5.4 eV. The diO-PBDB-T:Y6-based PSCs exhibit a much higher power conversion efficiency (PCE) of 4.26%. These results suggest that alkoxy substitution is an effective strategy to improve the optoelectronic properties of WBG polymers in NFA-PSCs. [ABSTRACT FROM AUTHOR]

A new carbazole-containing hyperbranched conjugated poly(phenylene vinylene) (Hyper-PCPPV) was synthesized through the Wittig polycondensation polymerization. Hyper-PCPPV has good solubility in common organic solvents and showed excellent thermal stability up to 425 °C with less than 5% weight loss. The photophysical properties of Hyper-PCPPV were investigated and compared with a carbazole-containing linear conjugated poly(para-phenylene vinylene) (Linear-PCPPV). An absorption maximum of Hyper-PCPPV film was determined at 353 nm which was far blue shifted than that of Linear-PCPPV (403 nm). Hyper-PCPPV showed blue photoluminescence (PL) peak at 448 nm. In addition, Hyper-PCPPV exhibited almost no excimer or aggregate emission peaks even when the polymer film was annealed at 80 °C for 30 min in air condition. [ABSTRACT FROM AUTHOR]

A fully soluble and photo-crosslinkable gate dielectric (6 F-SPI-Cinnamoyl: 6 F-SPI-CM) was synthesized. First, hydroxyl group substituted polyimide (6 F-SPI-Hydroxyl: 6 F-SPI-OH) polymer was prepared using monomers, 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and 4,4'-(perfluoropropane-2,2-diyl)dianiline (6FHAB) through polycondensation reaction. And, then 6 F-SPI-OH was further reacted with cinnamoyl chloride to prepare a photo-crosslinkable 6 F-SPI-CM. The thin film of photo-crosslinked 6 F-SPI-CM (C-6F-SPI-CM) showed the extremely low leakage current density of <1.0 x10−11 A/cm2. In addition, 6 F-SPI-CM was easily patterned by selective UV-light exposure. A flexible pentacene thin-film transistor (TFT) on polyethersulfone (PES) substrate with photo-crosslinked 6 F-SPI-CM as a gate dielectric showed a field effect mobility of 0.11 cm2/Vs with no hysteresis behavior. [ABSTRACT FROM AUTHOR]

In this study, we applied a strategy which is systematically varying the central' core in non-fused NFA structure to modulate the optical-electrochemical properties and photovoltaic performance. The optical and structural calculation was analyzed via UV–Vis spectroscopy and DFT calculation. The results exhibit that strong NIR absorption and good planar backbone structure on those non-fused NFAs. Consequently, photovoltaic device based on TT linked acceptor delivered a promising photovoltaic efficiency of 8.37% for as-cast device. These results suggest that the change of central unit is an effective strategy to improve the optoelectronic properties of non-fused NFAs in organic solar cells. [ABSTRACT FROM AUTHOR]

Fluorination has been established as an effective structural modification strategy to influence properties and has attracted attention in organic solar cells. Here, we design and synthesize three fused‐ring electron acceptors based on ladder‐type pentacyclic heteroacenes as the electron‐rich unit and 1,1‐dicyanomethylene‐3‐indanones with 0–2 fluorine substituents as the electron‐deficient units. Among these three molecules, two fluorine substituents nonfullerene acceptor, DTP‐2F exhibit strong absorption with high extinction coefficients and deep HOMO and LUMO level as compared with DTP‐0F and DTP‐1F. Device studies show that fluorinated nonfullerene acceptors (NFAs) lead to reduced VOC but increased JSC and FF, and therefore, the ultimate influence to efficiency depends on the compensation of VOC loss and gains of JSC and FF. Furthermore, fluorination affect to film morphology and miscibility between donor and acceptor. The fluorination of NFAs is one of the best design method of the donor and acceptor materials for efficient high‐performance organic solar cell. [ABSTRACT FROM AUTHOR]

Abstract: This paper demonstrates effects of a surface modification of polymeric gate insulators on a performance of organic thin-film transistor (OTFT). Pentacene OTFTs were fabricated with three types of polymer gate insulators—poly(4-vinylphenol) (PVP, G1) with comparably high dielectric constant, polyimide (PI, G2) with n-octadecyl (C18) side chain, which resulted in hydrophobicity and low dielectric constant, and surface modified PVP(G3). The G3 was prepared by a spin-coating the solution of G2 onto the G1 film. We found that the n-octadecyl group of the G3 protruded from the surface and made the PVP surface more hydrophobic. The less polar surface strongly improved the device performance. Subthreshold slope (s.s.) of the OTFT with G3 as the gate insulator decreased significantly to 2.7V/dec, which was much smaller than that of OTFTs fabricated with G1 (4.0V/dec). That is, thin layer with fewer C18 group in contact with pentacene induced a good electrical property like lower s.s. Further the higher dielectric constant of the underlying layer resulted in higher mobility of the device. The mobility (0.50cm2 V−1 s−1) of the OTFT with G3 as the gate insulator showed a higher value compared to that (0.25cm2 V−1 s−1) of the OTFT with G2. [Copyright &y& Elsevier]

Abstract: We report the results of a systematic investigation of the electrical and physical modifications to pentacene organic thin-film transistors (OTFT) that result from postfabrication thermal annealing. The thermally induced electrical modifications of the performance of the pentacene OTFTs were explored, and the morphology and structure of the pentacene films were investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. We found that postfabrication thermal annealing at 50°C significantly improved the mobility, from 0.19 to 0.36cm2/Vs, and increased the on/off ratio to almost twice that of the non-annealed device. We also found that annealing increased the pentacene grain size and enhanced the 001 peak intensity in the XRD pattern, indicating greater molecular ordering. At postfabrication thermal annealing temperatures of 70°C and above, the pentacene films lose their crystallinity and the OTFT performance is decreased. [Copyright &y& Elsevier]

Abstract: This paper demonstrates the effects of the imidization ratio of polyimide gate insulators on the performance of organic thin-film transistors (OTFTs). We report the synthetic results of polyimide films imidized at a temperature of 200°C along with an easily removed organic base catalyst (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU), and their application in gate insulators of organic thin-film transistors. The degree of imidization increased to almost 100% after a thermal treatment at 200°C for 40min in the presence of DBU. The performance of the pentacene OTFT dramatically improved by using low temperature cured polyimide film as the gate insulator. [Copyright &y& Elsevier]

Abstract: We prepared a novel organic passivation material to protect organic thin-film transistors (OTFTs) from H2O and O2 using a polyvinyl alcohol (PVA)/hydrophilic layered silicate (HLS) nanocomposite system. Using up to a 3wt% layered silicate to PVA weight concentration, a highly homogeneous nanocomposite solution was prepared. In addition, a PVA/HLS nanocomposite solution formed a smooth film layer by the spin-coating method with RMS surface roughness of about 1nm. An OTFT device with PVA passivation showed a decrease of 23% in field effect mobility after passivation. However, a pentacene TFT device with PVA/HLS nanocomposite passivation showed no significant initial performance drop after passivation, and mobility was even slightly improved. Pentacene TFT-passivated PVA/HLS showed 2860h of TFT lifetime (the time required to reduce the mobility by one-half of the initial mobility after passivation), which is almost twice the lifetime of pentacene TFT with PVA passivation (1320h). We propose that a layered silicate containing PVA nanocomposite film can be used as an effective organic passivation layer in an OTFT. [Copyright &y& Elsevier]

Abstract: Surface modification of the gate insulators is a key factor in improving the performance of organic thin-film transistors (OTFTs). We have developed a novel method for modifying the surface of a gate-insulating polymer containing an unsaturated double bond. A polyimide (PI) gate insulator containing an unsaturated double bond as a side chain was synthesized using the monomers pyromellitic dianhydride (PMDA), 4,4′-methylenedibenzenamine (MDA), and (E)-3,5-diaminobenzyl-3-(biphenyl-4-yl)acrylate (BIP). Octadecanethiol (ODT) was successfully reacted with the unsaturated double bond of this PI gate insulator under solvent-free conditions, thus modifying its surface and making it more hydrophobic. The modified hydrophobic surface strongly affected the initial growth mechanism of pentacene and, subsequently, the performance of the corresponding OTFTs. The devices fabricated with the modified PI gate insulators showed superior performance compared to those prepared with nonmodified insulators and exhibited a carrier mobility of 0.41cm2/(Vs), an on/off current ratio of about 8.6×105, and a subthreshold slope of 2.31V/dec. [Copyright &y& Elsevier]

Abstract: We have synthesized a novel fully soluble and low-temperature processable polyimide gate insulator (KSPI) through the one-step condensation polymerization of the monomers 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride and 4,4-diaminodiphenylmethane. Fully imidized KSPI was found to be completely soluble in organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), γ-butyrolactone, dimethylsulfoxide (DMSO), and 2-butoxyethanol. Thin films of KSPI can be fabricated at only 150°C and a pentacene OTFT with KSPI as a gate dielectric was found to exhibit a field effect mobility of 0.22cm2/Vs. To obtain a high performance organic thin-film transistor (OTFT), the KSPI surface was modified in our new technique by hybridization with a non-polar side chain containing a polyimide insulator (PI). The carrier mobility of a pentacene OTFT with a hybridized polyimide gate insulator (BPI-3) was found to be 0.92cm2/Vs. Our new low-temperature processable polyimides show promise as gate dielectrics for OTFTs. [Copyright &y& Elsevier]

We newly synthesized a series of naphthalene and fluorene containing alternating copolymers, poly[9,9-n-dihexyl-2,7-fluorenediylvinylene-alt-1,4-naphthalenevinylene] (1,4-PNFPV), poly[9,9-n-dihexyl-2,7-fluorenediylvinylene-alt-2,6-naphthalenevinylene] (2,6-PNFPV), and poly[9,9-n-dihexyl-2,7-fluorenediylvinylene-alt-2,3-naphthalene-vinylene] (2,3-PNFPV) through the well known Wittig polycondensation reaction. The conjugation lengths of the polymers were controlled by differently linked naphthalenes in the polymer main chain. The resulting polymers were completely soluble in common organic solvents and exhibited good thermal stability up to 400 °C. The synthesized polymers showed UV–visible absorbance and photoluminescence (PL) in the ranges 352–379 and 465–512 nm, respectively. The maximum emission peak of 1,4-PNFPV was found at 512 nm with green light. But, 2,6- and 2,3-PNFPV showed more blueshifted blue PL emission than that of 1,4-PNFPV at 477 and 465 nm, respectively. This result showed that 2,3- and 2,6-naphthalene linkage of the 2,3- and 2,6-PNFPV reduced π-conjugation length compared to 1,4-naphthalene linkage of the 1,4-PNFPV. The single-layer light-emitting device was fabricated which has a simple ITO (indium–tin oxide)/polymer/Al configuration. Electroluminescence (EL) maxima of 1,4-PNFPV and 2,6-PNFPV were shown at 523 and 484 nm, respectively. The measurement of current vs. electric field showed the threshold voltages of 1,4-PNFPV and 2,6-PNFPV to be about 1.7×108 and 2.1×108 V/m. The EL powers of 1,4-PNFPV and 2,6-PNFPV were reached 36 and 24 cd/m2 at 2.3×108 V/m (206 mA/cm2) and 2.8×108 V/m (190 mA/cm2), respectively. [Copyright &y& Elsevier]

Two new fully conjugated alternating copolymers containing both carbazole and naphthalene units were prepared through the Wittig condensation polymerization (carbazole units were linked with napthalene units by 1,4- and 2,6-linkages). The maximum photoluminescence wavelengths of 2,6-PNCPV and 1,4-PNCPV were found at 498 and 545 nm, which correspond to the greenish–blue and the yellow emission region, respectively, depending on the napthalene linkage. The turn-on voltages of 2,6-PNCPV and 1,4-PNCPV were 10.4 and 9.6 V, respectively, when the single-layer light-emitting diodes of Al/2,6-PNCPV or 1,4-PNCPV/ITO glass were fabricated. The electroluminescence spectrum of 1,4-PNCPV exhibited EL emissive band at 553 nm (yellow emission). Interestingly, the EL spectrum of 2,6-PNCPV was tailed to the longer wavelength region from the EL maximum point of 496 nm, which may be caused by formation of the intermolecular excimers. The emission color of 2,6-PNCPV was almost white to the naked eyes due to the tailing of 2,6-PNCPV emission and the weak interchain excimer peak at 750 nm. [Copyright &y& Elsevier]

Two 1,3-bis(thiophen-2-yl)−5,7-bis(2-ehtylhexyl)benzo-[1,2-c:4,5-c]-dithiophene-4,8-dione (BDD) based small molecules, SM1 and SM2 are designed and synthesized by incorporating benzodithiophene (BDT) central core, BDD dual accepting units and 3-ethyl rhodamine as endcap group with various number of BDT units. We systematically investigated the synthesis, optical and electrochemical properties, and photovoltaic characteristics of these donor materials. The number of BDT units have a significant influence on Jsc due to interconnected structure and results in a broader absorption on thin film. The inverted devices employed for both small molecules exhibited power conversion efficiencies of 0.41% for SM1 and 0.82% for SM2. [ABSTRACT FROM AUTHOR]

We have prepared a photo-crosslinkable, low-temperature processable, and soluble polyimide (SPI-Cinnamoyl: SPI-CM) gate insulator. Firstly, the soluble polyimide with hydroxyl group (SPI-Hydroxyl: SPI-OH) was synthesized through one-step condensation polymerization of monomers, 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and 3,3'-dihydroxy-4,4'-diaminobiphenyl (HAB). And, then SPI-OH was further reacted with cinnamoyl chloride to make a photo-crosslinkable polyimide (SPI-CM). The thin film of photo-crosslinked SPI-CM (C-SPI-CM) exhibited a dielectric constant as 3.7 at 10 kHz, and leakage current density of <9.7 × 10−11 A/cm2. In addition, SPI-CM could be easily patterned by selective UV-light exposure. A pentacene thin-film transistor (TFT) with the photo-crosslinked SPI-CM as a gate dielectric showed a field effect mobility of 0.16 cm2/Vs. [ABSTRACT FROM AUTHOR]

A novel fluorene containing hyperbranched conjugated poly(phenylene vinylene) (Hyper-PFPPV) was obtained through the Wittig polycondensation polymerization. Hyper-PFPPV has good solubility in common organic solvents and showed good thermal stability up to 369°C with less than 5wt% weight loss. The photophysical properties of Hyper-PFPPV in solution and net solid film are inspected and compared with fluorene containing linear poly(1,4-phenylene vinylene) (PFPPV). An absorption maximum of Hyper-PFPPV film was determined at 385 nm which was far blue shifted than that of linear PFPPV film (425 nm). Hyper-PFPPV showed blue photoluminescence (PL) peak at 461 nm. In addition, Hyper-PFPPV film exhibited almost no long wavelength emission peaks even the film was annealed at 80°C for 1 hr in air condition. High PL efficiencies (Φsol= 0.78 and Φfilm= 0.75) and no aggregate or excimer emission of Hyper-PFPPV are due to the inhibition of intramolecular or intermolecular interaction by the introduction of the hyperbranched network into the fluorene containing poly(phenylene vinylene) backbone. [ABSTRACT FROM AUTHOR]

We report a new polyvinyl alcohol (PVA)-tetraethoxysilane (TEOS) hybrid layer to protect an organic thin-film transistor (OTFT). PVA/TEOS hybrid thin film was successfully fabricated through hydrolysis and condensation mechanism. The surface roughness of PVA/TEOS film was measured by atomic force miscroscophy (AFM) and it showed a good surface roughness with a root-mean-squae value of about 0.23 nm. Thermally crosslinked PVA with TEOS was successfully adaped as a solution processable passivation layer for pentacene TFT. In case of well known photo-crosslinked PVA/ammonium dichromater (ADC) passivation, extremely large initial performance drop (almost 52% mobility drop) was observed after passivation. PVA/TEOS hybrid passiavtion, however, no significant initial performance drop was found after passivation process. In addition, pentacene TFT with PVA/TEOS passivation layer exhibited very stable TFT operation with almost no field mobility drop or threshold voltage shift up to 980 h. [ABSTRACT FROM AUTHOR]

Two novel thieno[3,4-b]pyrazine-based copolymers of the donor-acceptor type, poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b’]dithiophene-alt-5,7-(2,3-bis-(4-octyl-oxy-phenyl)-thieno[3,4-b]pyrazine)] (P1) and poly[4,8-bis(5-((2-ethylhexylthiophene)-2-yl))benzo[1,2-b:4,5-b’]dithiophene-alt-5,7-(2,3-bis-(4-octyloxy-phenyl)-thieno[3,4-b]pyrazine)] (P2), designed and synthesized by Stille polymerization for use in polymer solar cells. The synthesis, thermal stability, as well as the optical and photovoltaic properties of these polymers are systematically investigated. The polymers were thermally stable up to 290°C, and readily soluble in common organic solvent. Conventional polymer solar cells (PSCs) with the configuration ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al are fabricated. Under optimized conditions, the polymers display power conversion efficiencies (PCEs) for the PSCs in the range 0.28–1.46% under AM 1.5 illumination. Among the studied thienopyrazine-based copolymers, P2 displays a PCE of 1.46% with a short circuit current of 7.61 mA/cm2, an open circuit voltage of 0.43 V, and a fill factor of 0.45 under AM 1.5 illumination. [ABSTRACT FROM AUTHOR]

We have synthesized a series of surface energy controlled soluble polyimide (PI) gate insulators (KSPI-C1, KSPI-C3, and KSPI-C5) by one-step copolymerization method of the monomers 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 4,4-diaminodiphenylmethane, and 1-(3,5-diaminophenyl)-3-octadecylpyrrolidine-2,5-dione (DA-18-IM). The long alkyl chain containing DA-18-IM monomer was used to control the surface energy of PI polymers. Fully imidized PI polymers were found to be completely soluble in organic solvents such as N-methyl-2-pyrrolidone, dimethylacetamide, etc. Thermal gravimetric analysis exhibited that all polymers are stable up to more than 432°C with only 5wt.% weight loss. The glass transition temperatures of polymers are found to be between 208°C and 242°C by differential scanning calorimetry measurement. Thin films of all polymers could be fabricated at only 150°C and a pentacene thin-film transistor (TFT) with KSPI-C3 as a gate dielectric was found to exhibit the highest field effect mobility of 0.53cm2/Vs. Surface energy controlled PI polymers are promising candidates for gate dielectrics for organic TFTs. [ABSTRACT FROM AUTHOR]

We report a new crosslinked polyvinyl alcohol (PVA) layer to protect organic thin-film transistors (OTFTs) using the glutaraldehyde (GA) as a crosslinking agent. After thermal crosslinking reaction of PVA with GA, the water contact angle was increased from 9.8° to 55.1° as more hydrophobic state. This clearly means that hydroxyl group of PVA surface was disappeared by the crosslinking reaction. Thermally crosslinked PVA/GA was successfully adapted as solution processable passivation layer for pentacene TFT. In case of well known photo-crosslinked PVA/ammonium dichromate (ADC) passivation, extremely large initial performance drop (almost 52% mobility drop) was observed after passivation. PVA/GA passivation, however, only 3.8% initial mobility drop was found after passivation process. In addition, pentacene TFT with PVA/GA passivation layer exhibited very stable TFT operation with almost no field effect mobility drop or threshold voltage shift up to 1100 h. [ABSTRACT FROM PUBLISHER]

A novel hyperbranched conjugated poly(fluorene) (Hyper-PDHF) was obtained through the Suzuki coupling polymerization. Hyper-PDHF has good solubility in common organic solvents and showed good thermal stability up to 428°C with less than 5 wt% weight loss. The photophysical properties of Hyper-PDHF in solution and net solid film are inspected and compared with poly(di-n-hexylfluorene) (PDHF) having linear structure. An absorption maximum of Hyper-PDHF film was determined at 334 nm which was far blue shifted than that of linear PDHF film (381 nm). Hyper-PDHF showed absolute blue photoluminescence (PL) peak at 418 nm with 394 and 444 nm as shoulder peaks. Hyper-PDHF showed also high fluorescence quantum yield as about Φsol = 0.81. In addition, Hyper-PDHF film exhibited almost no longer wavelength emission peaks even the film was annealed at 80°C for 1 hr with illuminating UV (365 nm) in air condition. The high PL efficiency and no aggregate or excimer emission of Hyper-PDHF results from the inhibition of intramolecular or intermolecular interaction by the introduction of the hyperbranched network into the poly(fluorene) backbone. [ABSTRACT FROM PUBLISHER]

Abstract: High-k Gd2O3 used for thin film transistor (TFT) gate insulators has been synthesized via a simple solution process. Phase analysis and capacitive performance reveal that a high dielectric constant of ~20 and a low leakage current level of <10−8 A/cm2 at 1MV/cm with a good transparency under the visible wavelength region are readily produced by the sol–gel method. Eu3+ doping leads to an increased dielectric constant induced by the additional electric dipole transition, which is evidently visualized by the photoluminescence behavior and/or by the defect-controlled thin film microstructures. Thus, the solution-processed (Gd,Eu)2O3 film is a viable gate insulator to be considered for the proposed “color emissive” switching devices as well as for the low power-driven TFT devices. [Copyright &y& Elsevier]

Abstract: We have synthesized a fully soluble and low-temperature processable polyimide-based gate insulator (PI–H1) through one-step polymerization of the monomers 4,4''-(hexafluoroisopropylidene)diphthalic anhydride and 1,5-naphthalenediamine. Fully imidized PI–H1 was found to be completely soluble in common organic solvents such as cyclohexanone. Thermal gravimetric analysis (TGA) exhibited that PI–H1 is stable up to 523°C with only 5% weight loss. Thin films of PI–H1 could be fabricated at only 130°C and a pentacene thin-film transistor (TFT) with PI–H1 as a gate dielectric was found to exhibit a field effect mobility of 0.13cm2/Vs. When even thin films of PI–H1 gate dielectric were thermally stressed up to 400°C, almost no TFT performance drop was observed. Our new low-temperature processable and excellent heat resistance PI–H1 shows promise as a gate dielectric for TFT. [Copyright &y& Elsevier]

We have synthesized a thermally curable polymeric gate insulator (TFVOB-SPI) through the modification of soluble polyimide (SPI) using a 4-(1,2,2-trifluorovinyloxy)benzoyl (TFVOB) chloride. The thermal cross-linking of TFVOB-SPI was done and prepared the cross-linked TFVOB-SPI thin film having the perfluorocyclobutane (PFCB) structure. The PFCB structure was formed by the radical mediated thermal cycloaddition of trifluorovinyl ether of TFVOB. The cross-linked TFVOB-SPI showed excellent thermal stability up to 495 °C with only 5% weight loss and excellent chemical resistance to common organic solvents. The pentacene thin-film transistor (TFT) with the cross-linked TFVOB-SPI as a gate dielectric exhibited a field effect mobility of 0.28 cm2/Vs with almost no hysteresis during the TFT operation. [ABSTRACT FROM AUTHOR]

We have synthesized a thermally curable polymeric gate insulator (TFVOB-PVP) through the modification of the well-known poly(4-vinylphenol) (PVP) polymer using a 4-(1,2,2-trifluorovinyloxy) benzoyl (TFVOB) chloride. The thermal cross-linking of TFVOB-PVP was conducted and produced the cross-linked TFVOB-PVP with the perfluorocyclobutane (PFCB) structure. The PFCB structure was formed by the radical mediated thermal cycloaddition of trifluorovinyl ether group of TFVOB. The cross-linked TFVOB-PVP showed good thermal stability up to 423°C with only 5% weight loss and excellent chemical resistance to common organic solvents. The pentacene thin-film transistor (TFT) with the cross-linked TFVOB-PVP as a gate dielectric exhibited a field effect mobility of 0.14 cm2/Vs with almost no hysteresis during the TFT operation. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed photo-sensitive polyimide gate insulator with fluorine groups. [•] OTFTs with the polyimide gate insulators showed excellent performance. [•] The excellent performance is related to the surface properties of the gate insulators. [ABSTRACT FROM AUTHOR]

Abstract: A series of quinoxaline (Qx)-based copolymers, poly[2,7-(9,9-bis(2-ethylhexyl)dibenzosilole)-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P1), poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P2), and poly[4,4′-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]silole-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P3), were synthesized and characterized for use in polymer solar cells (PSCs). We describe the effects of the various donor segments on the optical, electrochemical, field-effect carrier mobilities, and photovoltaic characteristics of the resulting Qx-based copolymers. The results indicated that the donor units in the copolymers significantly influenced the band gap, electronic energy levels, carrier mobilities, and photovoltaic properties of the copolymers. The band gaps of the copolymers were 1.71–2.03eV. Under optimized conditions, the Qx-based polymers showed power conversion efficiencies for the PSCs of 0.87–2.15% under AM 1.5 illumination (100mW/cm2). Among the studied Qx-based copolymers, P2, which contained a benzo[1,2-b:4,5-b′]dithiophene unit, showed a power conversion efficiency of 2.15% with a short circuit current of 7.06mA/cm2, an open-circuit voltage of 0.67V, and a fill factor of 0.46, under AM 1.5 illumination (100mW/cm2). [Copyright &y& Elsevier]

A set of novel conjugated polyfluorene co- polymers, poly[(9,9′-didecylfluorene-2,7-diyl)- co-(4,7′-di-2-thienyl- 2′,1′,3′-benzothiadiazole-5,5-diyl)- co-(pyrene-1,6-diyl)], are synthesized via Pd(II)-mediated polymerization from 2,7-bis(4′,4′,5′, 5′-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9′-di- n-decylfluorene, 4, 7-di(2-bromothien-5-yl)-2,1,3-benzothiadiazole, and 1,6-dibromopyrene with a variety of monomer molar ratios. The field-effect carrier mobilities and optical, electrochemical, and photovoltaic properties of the copolymers are systematically investigated. The hole mobilities of the copolymers are found to be in the range 7.0 × 10−5 − 8.0 × 10−4 cm2 V−1 s−1 and the on/off ratios were 8 × 103 − 7 × 104. Conventional polymer solar cells (PSCs) with the configuration ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al are fabricated. Under optimized conditions, the polymers display power conversion efficiencies (PCEs) for the PSCs in the range 1.99-3.37% under AM 1.5 illumination (100 mW cm−2). Among the four copolymers, P2, containing a 2.5 mol % pyrene component incorporated into poly[9,9′-didecylfluorene-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PFDTBT) displays a PCE of 3.37% with a short circuit current of 9.15 mA cm−2, an open circuit voltage of 0.86 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW cm−2). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

Abstract: We have developed photo-sensitive, low-temperature processable, soluble polyimide (PSPI) gate insulator with excellent resistance to the photo-patterning process. The PSPI was synthesized through one-step condensation polymerization of monomers 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and 3,5-diaminobenzyl cinnamate (DABC). PSPI thin film, fabricated at 160°C, has a dielectric constant of 3.3 at 10kHz, and leakage current density of <1.7×10−10 A/cm2, while biased from 0 to 100V. PSPI could be easily patterned by selective UV-light exposure and dipping into γ-butyrolactone. To investigate the potential of the polyimide as the photo-patternable gate insulator, we fabricated pentacene OTFTs and confirmed the PSPI’s resistance to the photo-patterning process. The photo-patternable polyimide shows promise as gate dielectrics for OTFTs. [Copyright &y& Elsevier]

We have synthesised a series of new reactive mesogens with photopolymerisable di-acrylates and their corresponding non-reactive analogues based on the π-conjugated aromatic core, fluorene (F)-di-[thiophene (T)-benzene (B)], using the Stille and Suzuki coupling reaction. The effect of lateral alkyl chains on the 9-position of the central fluorene moiety as well as α, ω- side alkyl chains attached to the π-conjugated aromatic core on the mesomorphism was investigated by utilising differential scanning calorimetry (DSC) and polarising optical microscopy (POM). A wide angle X-ray scattering (WAXS) study at the various temperatures was also carried out to reveal phase structures. Photopolymerisable di-acrylates connected directly to the rigid aromatic core showed higher phase transition temperatures, probably due to the induced dipole moment in comparison with those of a non-reactive methyl-ether counterpart. [ABSTRACT FROM AUTHOR]

The effect of ion concentration, neutralization level and counterions in ionomers was systematically studied to obtain the optimal electroluminescent (EL) characteristics in polymer light-emitting diodes using poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) for the emissive layer and sulfonated polystyrene (SPS) ionomers for the electron-injecting layer. The optimum ion concentration of NaSPS was determined to be at 6.7 mol %. Ionomers with a higher neutralization level make the EL device more efficient, with the highest efficiency being at 200% overneutralization. The ionomer with a smaller metal counter ion greatly enhances the efficiency of EL devices with the indium–tin–oxide/MEH-PPV/LiSPS/Al device having the highest EL quantum efficiency, 1.18% photons/electron. The dominant factor in enhancing the luminance is the number of ionic dipoles near the cathode irrespective of the type of metal counterions, while the hole blocking mostly depends on the restriction of chain segmental motion in ionomers. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]