Improvements in Efficiency and Stability of Perovskite Solar Cells Using a Cesium Chloride Additive

Perovskite films with few defects play a key role in preparing high-performance perovskite solar cells (PSCs). Here, cesium chloride (CsCl) was introduced as a modulator into a perovskite precursor for manipulating the crystallization of perovskite films. By introducing CsCl, dense homogeneous perovskite films with high crystallinity, preferential orientation, and a pure black perovskite phase were prepared. In addition, the carrier lifetime of perovskite films was significantly increased because of the suppressed nonradiative recombination. Correspondingly, the power conversion efficiency (PCE) of small-area devices using CsCl regulation was increased from 20.56 to 22.86%. The 1 cm² PSCs present a PCE of 21.53%, demonstrating their reliability for mass production. Furthermore, the device showed excellent stability maintaining 93.8% of its initial PCE after 500 h of continuous irradiation. Also, 95.3% of its PCE was kept after storage in ambient air for 2100 h. This study demonstrates that CsCl doping is a reliable way to prepare PSCs for practical applications.