Hopping and band mobilities of holes in organic semiconductors at room temperature were estimated from first principle calculations. Relaxation times of charge carriers were evaluated using the acoustic deformation potential model. It is found that van der Waals interactions play an important role in determining accurate relaxation times. The hopping mobilities of pentacene, rubrene, and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) in bulk single crystalline structures were found to be smaller than 4 cm(2)∕Vs, whereas the band mobilities were estimated between 36 and 58 cm(2)∕Vs, which are close to the maximum reported experimental values. This strongly suggests that band conductivity is dominant in these materials even at room temperature.

We have synthesized and characterized stable organic semiconductors, 3,9-diphenyl-peri-xanthenoxanthene (Ph-PXX) and its soluble derivative for organic thin-film transistors (OTFTs). A π-system is stabilized against oxidation by introduction of heteroatoms into the reactive sites in the π-system. This strategy for stabilization does not suffer from the conventional tradeoff between environmental stability and efficient carrier injection, which appears when OSCs with deeper highest occupied molecular orbitals (HOMOs) are applied. UV-vis spectra of an air-saturated solution of Ph-PXX were unchanged over 120 h, indicating that it has an environmental stability. A HOMO level of Ph-PXX molecule was estimated to be only 5.1 eV below vacuum level, achieving efficient carrier injection. In fact, OTFTs with Ph-PXX showed high apparent mobility over 0.4 cm 2 /(V s) without demonstrating nonlinear behavior of sourcedrain ohmic contacts and have been shown to be stable for 5 months under ambient conditions. In addition, the OTFTs showed great thermal stability at temperatures up to 150 °C in air. These characteristics have been also achieved with a solution-processed OTFT with a soluble 3,9-bis(p-propylphenyl)-perixanthenoxanthene (PrPh-PXX). These results show that molecular design with passivation of the reactive cites is useful to make stable molecules with efficient carrier injection.

Abstract— An 80‐μm‐thick rollable AMOLED display driven by an OTFT is reported. The display was developed so as to be rollable in one direction with an integrated OTFT gate driver circuit. It was successfully operated by an originally developed organic semiconductor, a peri‐xanthenoxanthene derivative. The display retained its initial electrical properties and picture quality even after being subjected to 1000 cycles of a roll‐up‐and‐release test with a radius of 4 mm.

We demonstrate the lateral optical confinement of GaN-based vertical-cavity surface-emitting lasers (GaN-VCSELs) with a cavity containing a curved mirror that is formed monolithically on a GaN wafer. The output wavelength of the devices is 441–455 nm. The threshold current is 40 mA (Jth = 141 kA/cm2) under pulsed current injection (Wp = 100 ns; duty = 0.2%) at room temperature. We confirm the lateral optical confinement by recording near-field images and investigating the dependence of threshold current on aperture size. The beam profile can be fitted with a Gaussian having a theoretical standard deviation of σ = 0.723 µm, which is significantly smaller than previously reported values for GaN-VCSELs with plane mirrors. Lateral optical confinement with this structure theoretically allows aperture miniaturization to the diffraction limit, resulting in threshold currents far lower than sub-milliamperes. The proposed structure enabled GaN-based VCSELs to be constructed with cavities as long as 28.3 µm, which greatly simplifies the fabrication process owing to longitudinal mode spacings of less than a few nanometers and should help the implementation of these devices in practice.

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