High-Performance Polymer Light-Emitting Diodes Based on a Gallium-Doped Zinc Oxide/Polyimide Substrate

Conducting atomic force microscopy and scanning surface potential microscopy were used to study the surface electrical properties of gallium-doped zinc oxide (GZO) films on the nanoscale. GZO films on a polyimide (PI) substrate were prepared by pulsed laser deposition at various substrate temperatures. Our experimental results show a correlation between the local conductivity and work function (WF) and the gallium dopant concentration and the number of oxygen vacancies on the GZO surface. When the substrate temperature was approximately 150 ^°C, the root-mean-square roughness, the percent surface area of the conducting regions, and the mean WF on the GZO surface were 2.17 nm, 88.91%, and 4.74 eV, respectively. When the GZO/PI substrate was used as an anode material in a polymer light-emitting diode (PLED), the electroluminescence intensity was increased by nearly onefold compared with the standard PLED, which is based on a commercial-indium tin oxide/glass substrate.