We report the performance of solution-processed $n$ -type organic thin-film transistors (OTFTs) based on ${\mathrm{C}}_{60}$ derivatives. Long-chain alkyl-substituted ${\mathrm{C}}_{60}$ , C60-fused $N$ -methylpyrrolidine-meta-C12 phenyl (C60MC12), was used as a semiconducting layer. The C60MC12-thin-film transistor shows high electron mobility of $0.067{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ in saturation regime. From the result of x-ray diffraction analysis, the C60MC12 active layer forms highly ordered crystalline film. We found that self-assemble ability of long alkyl chains plays an important role for fabrication of highly ordered crystalline film, leading to achievement of high electron mobility in solution-processed $n$ -type OTFTs.

The time-of-flight technique has been used to study transports of photocarriers in regioregular and regiorandom poly(3-hexylthiophene) (P3HT) films by fabricating indium-tin-oxide/P3HT/Al sandwich cell. It has been found that regularity in the coupling of monomers, head-to-tail (HT) has a marked effect on electrical properties and photocarrier transport in P3HT. Both regular and random P3HT films exhibit a dispersive photocurrent response with the positive sign of photocarrier (hole). The room temperature hole mobility of regioregular P3HT is estimated to be 1.21 ×10^-3 cm²/V·s and is one order of magnitude larger than that of the random one. The mobility in regioregular P3HT is almost independent of the applied field while that of random P3HT shows a positive field dependence at the field larger than 1.0 ×10⁵ V/cm.

Polarized polymer light-emitting diodes (PLEDs) have been constructed utilizing friction-transferred poly(9,9-dioctylfluorene) (PFO) thin films. The friction transfer technique allows oriented PFO to be deposited directly onto an indium tin oxide anode without an alignment layer such as polyimide. Polarized absorption and photoluminescence spectra revealed that the polymer backbones are highly aligned in the friction direction. We fabricated PLEDs consisting of friction-transferred PFO as an emissive layer, vacuum-deposited bathocuproine as an electron transport and hole-blocking layer, and a vacuum-deposited LiF∕Al cathode. Highly polarized blue emission with an integrated polarization ratio of 31 and a luminance of up to 300cd∕m2 was observed from the PLEDs.