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

Abstract

Highly efficient CsPbI2Br planar heterojunction (PHJ) perovskite solar cells (PSCs) with a structure of ITO/SnO2/CsPbI2Br/Spiro-OMeTAD/Ag are fabricated via a low-temperature solution process. A flash annealing technique is used to produce high-quality CsPbI2Br perovskite films with high density and uniformity, as well as highly crystallized CsPbI2Br films. These CsPbI2Br films are used as the light-harvesting layer in PHJ PSC devices using SnO2 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 SnO2 and CsPbI2Br, supporting the efficient electron extraction from CsPbI2Br to SnO2. Thus, simple structural CsPbI2Br 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.