Indium-tin-oxide-free organic light-emitting device

Sapphire substrates coated with a gold (Au) layer in place of indium-tin-oxide (ITO) on glass substrates are used as hole-injecting anodes in organic light-emitting devices (OLEDs). Due to the unique quality of the sapphire/Au interface and the match of the Au work function with the highest occupied molecular orbital level of the adjacent hole transport layer (HTL) and the smoothness of the interface, the ITO-free OLED, with the structure sapphire/Au/HTL/poly(p-phenylenevinylene)/Ca/Ag, achieved an increase in current efficiency by more than a factor of three. In addition, the flawless sapphire substrate and anode/polymer interface make dark nonemissive areas decrease in number and area. The diodes show substantially slower degradation, and the lifetime in air increases by a factor of two or more.