Large-area perovskite solar cells with CsxFA1−xPbI3−yBry thin films deposited by a vapor–solid reaction method

Abstract

Large-area, highly uniform Cs_xFA_1−xPbI_3−yBr_y mixed cation perovskite films were prepared by a facile vapor–solid reaction method. In this method, CsBr and PbI₂ were first deposited via thermal evaporation, and then exposed to FAI/FACl vapor to form the Cs_xFA_1−xPbI_3−yBr_y perovskite. With the incorporation of CsBr, the crystallinity of the FAPbI₃ perovskite could be significantly improved. Meanwhile, the FACl vapor could accelerate the growth rate of the Cs_xFA_1−xPbI_3−yBr_y perovskite in the vapor–solid reaction process. By optimizing the content of Cs and the ratio of FACl/FAI, we obtained high quality, pin-hole free Cs_0.24FA_0.76PbI_3−yBr_y films. Based on these films, the small sized perovskite solar cells (PSCs) reached a champion power conversion efficiency (PCE) of 17.29%. Without encapsulation, the device with the Cs_0.24FA_0.76PbI_3−yBr_y perovskite showed much better moisture and thermal stability in comparison to that with the pristine FAPbI₃ perovskite. Furthermore, we also fabricated PSC modules with a size of 8 × 8 cm² and achieved a PCE of 12.24%, indicating that such a vapor–solid reaction method has a certain superiority in the manufacture of large-scale PSCs.