Tailoring the Interface in High Performance Planar Perovskite Solar Cell by ZnOS Thin Film

Charge-carrier recombination within the photoactive and charge extraction layers is one of the major obstacles to achieve high performance perovskite solar cells. Here, we demonstrate an ultrathin layer of ZnOS in between SnO2 and halide perovskite film that can effectively passivate the defects, suppressing the nonradiative recombination loss. It also helps to moderate the perovskite layer with increasing surface potential, which facilitates transferring the carriers from the perovskite to the hole transport layer, consequently providing an understanding of the bottom-up interfacial passivation of perovskite films. An enhancement of V-OC similar to 100 mV mainly causes the efficiency improvement from 17.22 to 19.4% in the combined SnO2-ZnOS based solar cell. In addition, we have performed a device modeling and theoretical analysis of these perovskite solar cells with and without the passivation layer. Theoretical results for the electronic band structure indicate that ZnOS contains an intermediate band structure between SnO2 and perovskite resulting in a much better band bending for the SnO2-ZnOS based solar cells. It is observed that the numerical results are in good agreement with the experimental outcomes. The combined electron transport layer strategy provides a way for defect passivation for further efficiency enhancement of the perovskite solar cells through interface engineering.