Ultra-thin aluminum oxide as an interface passivation layer for ZnO/p-Si heterojunction solar cells

In this paper, aluminum oxide (Al2O3) grown by a self-limiting atomic layer deposition (ALD) method is suggested as an interface passivation layer (IPL) to decrease the electrical recombination loss at the ZnO/p-Si interface. The reverse leakage current (IR) of ZnO/p-Si heterojunction diodes is reduced after inserting optimized Al2O3 films between ZnO/p-Si. From lifetime measurements, the effective recombination velocity trends consistently with the reverse saturation current (IS) of the devices tested. Also, from temperature-dependent current–voltage (I–V) and diverse physical measurements, the IR is shown to be closely related to free carrier trapping sites (Zni and Vo) near the half value of the difference in the work functions of Si and ZnO. Therefore, the experimental results show that the electrical recombination loss at the ZnO/p-Si interface can be effectively reduced by inserting an optimized Al2O3 IPL between the ZnO and p-Si.