Oxide semiconductors to boost organic OLED displays

February 21, 2017 // By Julien Happich
Researchers at the Tokyo Institute of Technology have developed novel transparent oxide-based semiconductor materials that could boost electron mobility when designed in the electron injection layer and transport layer of OLED displays.

The research led by Professor Hideo Hosono at the Institute of Innovative Research, Tokyo Institute of Technology, was part of the Strategic Basic Research Programs of the Japan Science and Technology Agency (JST). The researchers focused on how the thin-film transistors (IGZO-TFT) are now being applied to OLED displays, and then succeeded in using transparent amorphous oxides to develop new materials for use in the electron injection layer and electron transport layer.

The newly-developed transparent oxide semiconductors, a-calcium aluminate electride (a-C12A7:e) and a-zinc silicate (a-ZSO), are said to increase the stability when applying IGZO-TFT to OLED displays, while lowering manufacturing costs.

Publishing their results in the online bulletin edition of the "Proceedings of the National Academy of the USA" in a paper titled "Transparent amorphous oxide semiconductors for organic electronics: Application to inverted OLEDs", the a-C12A7:e is described as having an exceptionally low work function of 3.0 eV (equivalent to lithium metal) and was used to enhance the electron injection property from a-ZSO to an emission layer.

A-ZSO is reported to exhibit a low work function of 3.5 eV and high electron mobility of 1 cm2/(V · s) exceeding that of conventional organic materials by more two orders of magnitude. The a-zinc silicate can also form an ohmic contact with both conventional cathode and anode materials, making it a very versatile transport layer.