We demonstrate bilayer source-drain ͑S-D͒ electrodes for organic thin film transistors ͑OTFT͒. The bilayer consists of a transition metal oxide ͑MoO 3 ,WO 3 , or V 2 O 5 ͒ layer and a metal layer. The metal oxide layer, directly contacting the organic semiconducting layer, serves as the charge-injection layer. The overcoated metal layer is responsible for the conduction of charge carriers. We found that the metal oxide layer coupled between pentacene and metal layers played an important role in improving the field-effect transistor characteristics of OTFTs. Devices with the bilayer S-D electrodes showed enhanced hole-injection compared to those with only metal electrode. High field-effect mobility of 0.4 cm 2 / V s and on/off current ratios of 10 4 were obtained in the pentacene based TFTs using the bilayer S-D electrodes at a gate bias of −40 V. The improvement is attributed to the reduction in the contact barrier and the prevention of metal diffusion into the organic layer and/or unfavorable chemical reaction between the organic layer and the metal electrode.

Exploiting the reactivity of the P-atom of phosphole-based oligomers, we have achieved access to the first organophosphorus-containing organic light-emitting diode (OLED) materials. The versatility of these P-materials is demonstrated with the synthesis of a corresponding gold complex that has also been used as an OLED material. Optimization of the OLED devices by doping the phosphole layer with a red fluorescent dye is described.