Transparent Al-doped ZnO anodes in organic light-emitting diodes investigated using a hole-only device

► OLED devices with AZO films and commercial ITO. ► Hole-only devices with AZO film and commercial ITO anodes were used to examine the efficiency of hole injection. ► AZO films are suitable as anodes of OLED devices under a high applied voltage. ► The indium diffuses into the organic layer.