Organic Light-Emitting Transistors Based on Pentacene and 4,5-Di(9 H-carbazol-9-yl)phthalonitrile Doped onto 1,3-Bis(N-carbazolyl)benzene

In this study, multilayered, organic-based light-emitting transistors (OLETs) were produced and characterized. The neutral cluster beam deposition method was applied to successively deposit organic semiconducting layers of pentacene, 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN) doped onto 1,3-bis(N-carbazolyl)benzene (mCP), and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) as the hole-transport, emissive, and electron-transport layers, respectively. The effects of drain electrodes (Au or Li/Al) and TPBi on the device performance were examined under ambient conditions. The bilayered pentacene (bottom, 50 nm)/mCP:2CzPN (top, 50 nm) and trilayered pentacene (bottom, 50 nm)/mCP:2CzPN (middle, 50 nm)/TPBi (top, 10 nm) OLETs demonstrated both electrical switching functionality and control of electroluminescence (EL) in air. In particular, the EL intensity (I_EL) was significantly enhanced in the asymmetric bilayered devices adopting a low work function Li/Al drain electrode owing to the lower electron injection barrier. The operating light emission mechanisms responsible for the observed EL and recombination zone were discussed with the aid of photographic images provided by a charge-coupled device camera.