Enhanced Performance of Sn-Based Perovskite Solar Cells by Two-Dimensional Perovskite Doping

The poor performance of tin (Sn)-based perovskite solar cells (PSCs) is mainly due to the easy oxidation of Sn2+ to Sn4+, the low formation energy of Sn vacancies, and the unbalanced rates between nucleation and crystal growth in Sn-based perovskite films. In this study, a small amount of two-dimensional tetra-n-butylammonium (TBA) cation is doped in Sn-based perovskite for the first time, which effectively passivates film defects. TBA cation doping leads to improved surface coverage, suppressed Sn2+/Sn4+ oxidation, and reduced background charge carrier density in mixed perovskite films. Consequently, the efficiency of TBA-doped formamidinium tin triiodide (FASnI3) and cesium tin triiodide (CsSnI3) cells is greatly improved from 4.0 to 7.0% and from 1.3 to 2.8%, respectively.