Improving performance of perovskite solar cells based on ZnO nanorods via rod-length control and sulfidation treatment

The structure and properties of electron transport layers play an important role in determining device performance of perovskite solar cells (PSCs). PSCs based on one-dimensional ZnO nanorods still suffer from serious efficiency losses. In this work, length of ZnO nanorods was firstly optimized by exploring steady photoluminescence quenching of perovskite films deposited on ZnO nanorods of various lengths and their photovoltaic performance. PSCs fabricated on ZnO nanorods of similar to 400 nm yield the best power conversion efficiency of similar to 10% due to their relatively balanced charge carrier transfer and transport properties. On this basis, sulfidation treatment was applied on these ZnO nanorods to further improve device performance. It is found that the sulfidation treatment of ZnO nanorods may play a role in at least three aspects: (I) passivating defects on the surface of ZnO nanorods; (II) facilitating charge carrier transfer and transport by forming ZnO/ZnS type II hetemjunctions; (III) alleviating perovskite dissociation to some extent. Due to these benefits, the power conversion efficiency of perovskite solar cells based on ZnO nanorods was improved to 11.72%, along with less hysteresis. This work not only demonstrates the importance of rod-length and sulfidation treatment on device performance of perovskite solar cells based on ZnO nanorods but also provides a feasible method to improve their power conversion efficiency.