The CsPbI2Br Perovskite Solar Cell with High Open‐Circuit Voltage by Crystallization Optimization

All‐inorganic CsPbI 2 Br perovskite acquires affirmation in recent years by reason of the excellent balance between stability and power conversion efficiency (PCE), but its PCE is still inferior to the commercial application standard, of which inferiority roots from the uncontrolled crystallization and a mass of the imperfections. Herein, the crystallization is regulated by introducing a certain amount of lead acetate into the precursor, and the complex Pb(Ac) 2 × DMSO × PbI 2 forms in precursor. The Oswald crystal pattern changes into the 2D layered structure —3D cubic structure crystal pattern, and this transition process is delayed, and the complex in precursor is regarded as the 2D crystal growth template. And the iodine vacancy defects are passivated by the Ac − , and the PbO passivates the grain boundary defects, as proved by the photoluminescence spectrum and X‐ray photoelectron spectroscopy. The two effects work together improve the performance of the CsPbI 2 Br perovskite solar cells. The PCE increases from 9.78% to 13.73%, and the open‐circuit voltage increases from 1.23 to 1.32 V, which is one of the superior performances reported for the carbon‐based pure CsPbI 2 Br perovskite solar cells to date.