Preannealing Process Improves the Efficiency of CsPbIBr2 Perovskite Solar Cells

CsPbIBr2 has shown great potential in the optoelectronics field due to its well-balanced relationship between bandgap and durability among all-inorganic perovskites materials. However, the CsPbIBr2 thin films prepared by the traditional one-step spin coating method suffer from unsatisfactory morphology, poor crystallinity, and high defect density, which lead to the degradation of device performance. Herein, a simple preannealing method is used to form unstable transition films which are then annealed at high temperature to obtain CsPbIBr2 perovskite films with uniform morphology, free pinholes, and strong crystallinity. The performance of the device can be effectively improved due to the reduction of defects and the optimization of the contact between functional layers. Therefore, the power conversion efficiency of 9.6% is obtained, which is nearly 100% improvement compared with that of the control device.