TCO/n-Si hetero-junction solar cells at present have low conversion efficiency although they have been fabricated for decades. In order to better understand the operation mechanism of such kind of cells and find possible solutions, the effect of the work function of transparent conducting oxide (TCO) on the performance of the TCO/n-Si hetero-junction cells was simulated. The band diagram, carrier lifetime and donor concentration in silicon layer were calculated. It is demonstrated that conversion efficiency, open circuit voltage and fill factor increase with the TCO work function. Analyzing band diagram of the TCO/n-Si hetero-junction indicates that the high TCO work function enhances the built-in potential resulting in the increase of open circuit voltage. Enhancement of the minority carrier lifetime in the interface at a higher TCO work function improves conversion efficiency. High interfacial defect density reduces the performance of the cells. It is suggested that increasing the TCO work function difference is a prospective solution to improve the performance of TCO/n-Si hetero-junction solar cells. (C) 2014 Elsevier Ltd. All rights reserved.