In this paper, we investigate an electronic structure and hole-injection properties of organic light-emitting devices (OLEDs) based on molybdeum-doped zinc oxide (MZO) anode. Our studies reveal that operation voltage and current efficiency of the device are associated with work function and surface roughness of anode, respectively. From the experimental results, we found that the formation of S-metal bonds and the removal of dangling bonds in the thermal-annealed MZO film could lead to an increase in the surface energy and the work function, meaning that thermal-annealing might be more helpful in improving the efficiency of MZO based organic devices. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.030206esl] All rights reserved.