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

Abstract

Highly\nefficient CsPbI₂Br planar heterojunction (PHJ) perovskite\nsolar cells (PSCs) with a structure of ITO/SnO₂/CsPbI₂Br/Spiro-OMeTAD/Ag are fabricated via a low-temperature solution\nprocess. A flash annealing technique is used to produce high-quality\nCsPbI₂Br perovskite films with high density and uniformity,\nas well as highly crystallized CsPbI₂Br films. These CsPbI₂Br films are used as the light-harvesting layer in PHJ PSC\ndevices using SnO₂ as the electron transport layer and\nSpiro-OMeTAD as the hole transport layer. Based on the measurement\nof the energy levels via ultraviolet photoelectron spectroscopy, it\nindicates that there is a very good interfacial band alignment between\nSnO₂ and CsPbI₂Br, supporting the efficient\nelectron extraction from CsPbI₂Br to SnO₂. Thus,\nsimple structural CsPbI₂Br PHJ PSCs with power conversion\nefficiencies (PCEs) up to 13.09% are achieved, which is comparable\nto the highest reported PCEs for all-inorganic PHJ PSCs. The findings\nshow that the PHJ device architecture, instead of a mesoporous structure,\ncan be used to fabricate highly efficient inorganic PSCs with a simple\nstructure, offering the advantages of matching well the low-cost,\nhigh-throughout roll-to-roll printing process.