Interface engineering in preparation of organic surface-emitting diodes

Abstract

Surface-emitting organic light emitting diode (OLED) was prepared by sputter deposition of indium-tin-oxide on a buffered organic layer structure. Confirming a previous report, a thin film of copper phthalocyanine (CuPc) was found to be a useful buffer layer in preventing sputter damage to the OLED layer structure, particularly the underlying Alq emissive layer. However, the CuPc layer forms an electron-injection barrier with the Alq layer, resulting in increased electron-hole recombination in the nonemissive CuPc layer, and thus a substantial reduction in electroluminescence efficiency. Incorporation of Li at the CuPc/Alq interface was found to reduce the injection barrier at the interface and recover the overall device efficiency with good surface emission characteristics.