The ability to control the molecular organization of electronically active liquid-crystalline polymer semiconductors on surfaces provides opportunities to develop easy-to-process yet highly ordered supramolecular systems and, in particular, to optimize their electrical and environmental reliability in applications in the field of large-area printed electronics and photovoltaics. Understanding the relationship between liquid-crystalline nanostructure and electrical stability on appropriate molecular surfaces is the key to enhancing the performance of organic field-effect transistors (OFETs) to a degree comparable to that of amorphous silicon (a-Si). Here, we report a novel donor-acceptor type liquid-crystalline semiconducting copolymer, poly(didodecylquaterthiophene-alt-didodecylbithiazole), which contains both electron-donating quaterthiophene and electron-accepting 5,5'-bithiazole units. This copolymer exhibits excellent electrical characteristics such as field-effect mobilities as high as 0.33 cm(2)/V.s and good bias-stress stability comparable to that of amorphous silicon (a-Si). Liquid-crystalline thin films with structural anisotropy form spontaneously through self-organization of individual polymer chains as a result of intermolecular interactions in the liquid-crystalline mesophase. These thin films adopt preferential well-ordered intermolecular pi-pi stacking parallel to the substrate surface. This bottom-up assembly of the liquid-crystalline semiconducting copolymer enables facile fabrication of highly ordered channel layers with remarkable electrical stability.

Reduced graphene oxide (RGO) is an electrically conductive carbon-based nanomaterial that has recently attracted attention as a potential electrode for organic electronics. Here we evaluate several solution-based methods for fabricating RGO bottom-contact (BC) electrodes for organic thin-film transistors (OTFTs), demonstrate functional p- and n-channel devices with such electrodes, and compare their electrical performance with analogous devices containing gold electrodes. We show that the morphology of organic semiconductor films deposited on RGO electrodes is similar to that observed in the channel region of the devices and that devices fabricated with RGO electrodes have lower contact resistances compared to those fabricated with gold contacts. Although the conductivity of RGO is poor compared to that of gold, RGO is still an enticing electrode material for organic electronic devices possibly owing to the retention of desirable morphological features, lower contact resistance, lower cost, and solution processability.

We report the observation of band-like transport from printed polymer thin films at room temperature. This was achieved from donor-acceptor type thiophene-thiazole copolymer that was carefully designed to enhance the planarity of the backbone and the resulting transfer integral between the macromolecules. Due to the strong molecular interaction, the printed polymer film exhibited extremely low trap density comparable to that of molecular single crystals. Moreover, the energy barrier height for charge transport could be readily reduced with the aid of electric field, which led formation of extended electron states for band-like charge transport at room temperature.

Poly(5,8-dialkoxyanthraquinone-1,4-diyl) P(5,8-OR-1,4-AQ) (R ) n-C 6 H 13 through n-C 16 H 33 ), poly(5,8-dihydroxyanthraquinone-1,4-diyl) P(5,8-OH-1,4-AQ), poly(4,8-diaminoanthraquinone-1,5-diyl) P(4,8-NH 2 -1,5-AQ), poly(4,8-dihydroxyanthraquinone-1,5-diyl) P(4,8-OH-1,5-AQ), and poly(4,8-dinitroanthraquinone-1,5-diyl) P(4,8-NO 2 -1,5-AQ) were prepared by dehalogenative polycondensation of the corresponding dichloro monomers with a zerovalent nickel complex or copper. They were soluble in organic solvents, and showed number average molecular weights of 3100-8600 and [η] values of 0.10-0.70 dL g -1 . P(5,8-OR-1,4-AQ)s and P(4,8-NO 2 -1,5-AQ) afforded clear XRD peaks and their packing structures in the solid have been analyzed. P(5,8-OR-1,4-AQ) is considered to take an end-to-end packing mode and this polymer with long alkoxy side chains exhibits smectic and enanthiotropic liquid crystalline behavior and piezochromism. All the polymers were susceptible to electrochemical reduction and a linear correlation held between the reduction potentials of the polymers and electron affinity of the corresponding monomeric anthraquinones with a slope of 0.79. A photovoltaic cell using P(4,8-NO 2 -1,5-AQ) and polythiophene has been constructed.

Stable uniform performance inkjet-printed polymer transistor arrays, which allow demonstration of flexible full-color displays, were achieved by new ambient processable conjugated copolymer semiconductor, and OTFT devices incorporating this material showed high mobility values>1.0 cm2 V(-1) s(-1). Bias-stress stability of the devices was improved with a channel-passivation layer, which suppresses the density of trap states at the channel interface.

Molecularly hybridized materials composed of polymer semiconductors (PSCs) and single-walled carbon nanotubes (SWNTs) may provide a new way to exploit an advantageous combination of semiconductors, which yields electrical properties that are not available in a single-component system. We demonstrate for the first time high-performance inkjet-printed hybrid thin film transistors with an electrically engineered heterostructure by using specially designed PSCs and semiconducting SWNTs (sc-SWNTs) whose system achieved a high mobility of 0.23 cm(2) V(-1) s(-1), no V(on) shift, and a low off-current. PSCs were designed by calculation of the density of states of the backbone structure, which was related to charge transfer. The sc-SWNTs were prepared by a single cascade of the density-induced separation method. We also revealed that the binding energy between PSCs and sc-SWNTs was strongly affected by the side-chain length of PSCs, leading to the formation of a homogeneous nanohybrid film. The understanding of electrostatic interactions in the heterostructure and experimental results suggests criteria for the design of nanohybrid heterostructures.

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A High-performance top-emitting green phosphorescent OLED with a long operational lifetime, an LT of 200% longer and with a high current efficiency, 118% higher than the devices with state-of-the art Ir complexes at the luminance of 15,000 cd m −2 , was realized using a developed Pt complex and new hole transporting buffer and exciplex host materials. To the best of our knowledge, the current efficiency and lifetime of our achievements at this high luminance are more than 1.5 times higher and 100 times longer, respectively, than those of green phosphorescent OLEDs with Pt complexes from literatures and materials companies in the world. This high current efficiency was achieved with higher horizontal transition dipole ratio, 86%, and short decay time, 2.4 μs, of our own developed Pt complex.