In this paper, we report a detailed simulation study and analysis of interface effects on the performance of a ZnO/crystalline Si heterojunction solar cell by considering the ZnO carrier concentration and conduction band offset-dependent interface recombination. Partial deviation in results, observed by a group of researchers when they experimentally tested a theoretical solution proposed by another group for the reduction of interface recombination has been addressed in this report. The effect of ZnO layer thickness on the performance of the solar cell is also studied in this report. Results show that interface recombination can be reduced and hence efficiency can be enhanced by controlling the carrier concentration and thickness of the ZnO layer along with the band offsets between ZnO and Si. Thus, appropriate engineering for the reduction of conduction band offset and a suitable choice of ZnO layer thickness are important in obtaining the enhanced efficiency.