Preparation of High-Performance Inorganic Perovskite Solar Cells through In Situ Ion-Exchange-Controlled Crystallization

Enhancing film quality and passivating defects are effective strategies for improving the power conversion efficiency (PCE) and the open-circuit voltage (VOC) of inorganic perovskite solar cells (IPSCs). In this study, an in situ ion exchange (ISIE) approach was put forward to synthesize dimethylammonium acetate (DMAAc) and lead iodide (PbI2), which controls crystallization and passivates defects. The reaction between lead acetate (Pb(Ac)2) and dimethylammonium iodide (DMAI) occurs spontaneously, yielding PbI2 and DMAAc. Therefore, this additional reaction establishes a minor competitive relationship during the crystallization process, thereby enhancing crystal growth by slowing the rate of crystallization. Furthermore, both PbI2 and DMAAc serve to passivate defects and improve film quality, respectively. The nonradiative recombination is minimized, and the configuration of energy levels is optimized. As a result, the champion PCE of inverted IPSCs fabricated in air reaches 21.23%. This represents one of the highest PCE values currently recorded among IPSCs.