Enhancing the performance of perovskite solar cells through simple bilateral active site molecule assisted surface defect passivation

Surface defects of perovskite film seriously restrict the photovoltaic performance of perovskite solar cells (PSCs). Therefore, it's extremely important to develop effective surface defect passivation methods to further enhance the performance of PSCs. In this work, we design and synthesize a small molecular material (4-cyanophenyl) methanamine iodide (CMAI) by incorporating bilateral functional sites of nitrile (-CN) and ammonium (-NH3+) groups. The research manifests that CMAI can not only passivate the lead defects, but also fill the iodide ion vacancy, resulting in the significant reduction of trap state density, the effective suppression of nonradiative recombination, as well as the preferable carrier transport from the perovskite to the hole transport layer. By optimizing the treatment conditions, the CMAI-treated device exhibits an impressive efficiency of 21.59% together with excellent humidity stability, thoroughly over-performing the control device. This work provides a simple and efficient passivation strategy for fabrication of highly stable and efficient PSCs.