Electron and hole transport in polymethylphenylsilane (PMPS) containing anthracene units in the polymer backbone (PMPS-AN) has been studied by time-of-flight and electrophotographic measurements. It is found that the hole transport of PMPS-AN is non-dispersive and exhibits thermally activated behavior. The anthracene incorporation to the polymer backbone of PMPS slightly decreases the hole drift mobility of PMPS-AN because of the increase in energetic disorder. In PMPS-AN, the electron transport, which has not been observed in organic polysilanes, is clearly seen. In contrast to the hole transport, the electron transport exhibits anomalous dispersion of the transit times and the electron drift mobility is independent of temperature. It is suggested that the electron transport is due to geometrical disorder of electron hopping sites (anthracene units). From the electrophotographic measurements, we discuss the applicability of PMPS-AN to photoreceptors and estimate the Schubweg of electrons in PMPS-AN.

Charge carrier generation, transport, and exciton diffusion in f ac tris(2-phenylpyridine)iridium(III) Ir(ppy)3 doped in 4,4'-N,N'-dicarbazole-biphenel (CBP) thin films, an emissive layer of green electrophosphorescent devices, have been studied in terms of time-of-flight (TOF) transient photocurrent, steady-state photocurrent and time-resolved photoluminescence (PL) spectroscopies. It is found that the excitation energy rapidly transfer from CBP to Ir(ppy)3, and that the charge carriers are generated on Ir(ppy)3 sites. With increasing Ir(ppy)3 concentration, the electron drift mobility is slightly decreased, while the hole transit signals become unobservable. The electron and hole transport properties of Ir(ppy)3 doped CBP thin films result from the energy levels of the lowest unoccupied molecular orbital and the highest occupied molecular orbital of Ir(ppy)3 with respect to those of CBP. From steady-state photocurrent measurement, the diffusion lengths of 3.5% and 7.0% Ir(ppy)3 doped CBP thin films are determined to be 21 nm and 50 nm, respectively.

Solution-based organic field-effect transistors (OFETs) with low parasitic capacitance have been fabricated using a self-aligned method. The self-aligned processes using a cross-linking polymer gate insulator allow fabricating electrically stable polymer OFETs with small overlap area between the source-drain electrodes and the gate electrode, whose frequency characteristics have been investigated by impedance spectroscopy (IS). The IS of polymer OFETs with self-aligned electrodes reveals frequency-dependent channel formation process and the frequency response in FET structure.