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Highlights: [•] Indium tin oxide (ITO) and Ag are used as source/drain (S/D) electrodes. [•] Influence of S/D electrodes on external quantum efficiency (EQE). [•] Exciton quenching by Ag electrodes results in a low EQE. [•] A relatively high EQE of 1% regardless of the emission site for the device with ITO. [•] Lower exciton quenching at the interface of S/D electrodes for the device with ITO. [ABSTRACT FROM AUTHOR]

Abstract: In order to obtain phosphorescent emission from organic field-effect transistors, thermal diffusion of a phosphorescent dye at the interface between the active layer and gate insulator was controlled by utilizing the fact that liquid-crystalline semiconducting polymers self-organize due to reorientation of the molecules and increase in the size of the crystalline regions during thermal annealing. For top-gate type devices using poly(alkylfluorene) doped with a red emissive phosphorescent material, ambipolar characteristics and red emission from the phosphorescent material were clearly observed. We demonstrate the possibility of producing phosphorescent organic light-emitting transistors using a liquid-crystalline semiconducting polymer doped with phosphorescent emissive dopants by the thermal diffusion method. [Copyright &y& Elsevier]

Abstract: The characteristics of solution processed top-gate-type organic field-effect transistors (OFETs) with indium–tin oxide (ITO) drain/source electrodes using polyfluorene derivatives were investigated. An OFET with poly(9,9-dioctylfluorene) (F8) as an active layer, which contains only a fluorene backbone, exhibited ambipolar characteristics with hole and electron field-effect mobilities of approximately 10−3 cm2 V−1 s−1. All OFETs with fluorene derivatives exhibited ambipolar characteristics because the value of the work function of the ITO electrode is approximately in the middle between the highest occupied molecular orbital and lowest unoccupied molecular orbital levels of fluorene derivatives. Fluorene derivatives can conduct both holes and electrons. Ambipolar OFETs with F8 and a fluorene derivative doped in F8 can be applied to various color tunable light-emitting devices. [Copyright &y& Elsevier]