Interface engineering in preparation of organic surface-emitting diodes

Surface-emitting organic light emitting diode (OLED) was prepared by sputte r deposition of indium-tin-oxide on a buffered organic layer structure. Con firming 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, t he CuPc layer forms an electron-injection barrier with the Alq layer, resul ting in increased electron-hole recombination in the nonemissive CuPc layer , and thus a substantial reduction in electroluminescence efficiency. Incor poration of Li at the CuPc/Alq interface was found to reduce the injection barrier at the interface and recover the overall device efficiency with goo d surface emission characteristics. (C) 1999 American Institute of Physics. [S0003-6951(99)00421-0].