Device applications of transparent oxide semiconductors: Excitonic blue LED and transparent flexible TFT

Recent progress in oxide-based transparent optoelectronic devices is reviewed. It is important to understand electronic structures inherent to oxides in order to develop new materials and to find suitable device applications that oxide materials can have distinct advantages over conventional semiconductors. Two new transparent oxide semiconductors, (i) p-type layered oxychalcogenides LaCuOCh (Ch = chalcogen), and (ii) large-mobility amorphous oxide semiconductors (AOSs), are taken as examples. Their peculiar properties are discussed in comparison with conventional semiconductors based on consideration of electronic structures. Two associated devices, an excitonic light-emitting diode using LaCuOCh and transparent flexible thin film transistors using AOSs, are also shown.