A-Si:H/Si wafer heterojunction solar cells with different ZnO:Al sputtering conditions were fabricated and the effects of sputtering conditions on device performance were evaluated. Various sputter condition(substrate temperature RT~200’C, working pressure 0.5mTorr~15mTorr, thickness 60~100nm) were tested and optimized as 130’C, 0.5mTorr, 80nm by measuring reflectance and sheet resistance of ZnO:Al layer on corning glass. However, when optimal ZnO:Al condition was applied to solar cells, series resistance was high which led to device efficiency ~10%. Dark I-V curves of with and w/o ZnO layer showed large difference, which means there is a kind of barrier to current flow between ZnO:Al and a-Si:H layer. Modified condition with double layer scheme was applied and lower series resistance and device efficiency above 12% could be reached. The improvement may be due to either suppression of Si oxide formation or less defect formation by impinging atoms.