Highly Efficient, Solution-Processed CsPbI2Br Planar Heterojunction Perovskite Solar Cells via Flash Annealing

Highly efficient CsPbI 2 Br planar heterojunction (PHJ) perovskite solar cells (PSCs) with a structure of ITO/SnO 2 /CsPbI 2 Br/Spiro-OMeTAD/Ag are fabricated via a low-temperature solution process. A flash annealing technique is used to produce high-quality CsPbI 2 Br perovskite films with high density and uniformity, as well as highly crystallized CsPbI 2 Br films. These CsPbI 2 Br films are used as the light-harvesting layer in PHJ PSC devices using SnO 2 as the electron transport layer and Spiro-OMeTAD as the hole transport layer. Based on the measurement of the energy levels via ultraviolet photoelectron spectroscopy, it indicates that there is a very good interfacial band alignment between SnO 2 and CsPbI 2 Br, supporting the efficient electron extraction from CsPbI 2 Br to SnO 2 . Thus, simple structural CsPbI 2 Br PHJ PSCs with power conversion efficiencies (PCEs) up to 13.09% are achieved, which is comparable to the highest reported PCEs for all-inorganic PHJ PSCs. The findings show that the PHJ device architecture, instead of a mesoporous structure, can be used to fabricate highly efficient inorganic PSCs with a simple structure, offering the advantages of matching well the low-cost, high-throughout roll-to-roll printing process.