Al-doped ZnO (AZO) films of various thicknesses were prepared by sputtering on glass substrates for use as transparent anodes of OLED devices. The effect of AZO film thickness on the structure, conductivity, and transparency of AZO films was investigated. The performance of OLEDs based on AZO anodes with various thicknesses is also discussed. The surface roughness of AZO is a crucial factor for the performance of OLEDs. The AZO thin film may be a potential alternative to an ITO anode due to its low price, and non-toxicity. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3615847] All rights reserved.