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

Al-doped ZnO (AZO) films with a thickness of ∼400 nm were prepared by sputtering on glass substrates for use as transparent anodes of organic light-emitting diodes (OLED) devices. The operation voltages (at 100 cd/m2) of OLED devices with AZO and ITO anode materials were 10.5 and 5.5 V, respectively. The maximum luminance output of the AZO device was 6450 cd/m2 (achieved at 12.5 V) and that of the ITO device was 9830 cd/m2 (achieved at 10.5 V). We demonstrate that a hole-only device method can be used to estimate the suitability of AZO and ITO anodes in the OLED devices and to verify experimental results. The AZO thin films with low price and non-toxicity may be suitable as alternative anodes in OLED devices under high voltage.