Polymer additive-promoted porous PbBr2 layer for fabricating high-performance carbon-based CsPbIBr2 perovskite solar cells through a two-step sequential deposition process

Abstract

High-quality inorganic perovskite films are the most vital factor to assemble efficient and stable inorganic perovskite solar cells. Herein, a polyethylene glycol (PEG)-assisted two-step sequential deposition process is proposed to fabricate high-quality CsPbIBr₂ perovskite films, wherein PEG is incorporated into a PbBr₂ solution to modulate the PbBr₂ colloidal properties due to the strong interaction between PEG molecules and PbBr₂. The modulation of PbBr₂ colloidal properties through adding PEG tunes the crystallization of PbBr₂ and leads to the formation of porous PbBr₂ films during the first-step deposition process. Such porous PbBr₂ films favor CsI penetration during the second-step CsI deposition process and provides sufficient space for perovskite crystal growth and volume enlargement during the subsequent annealing process. As a result, a full-coverage and high-quality CsPbIBr₂ perovskite film with reduced defects and enlarged grains is obtained after optimizing the amount of PEG. The assembled carbon-based CsPbIBr₂ perovskite solar cell delivers a high power conversion efficiency of 10.26%. Moreover, the unencapsulated CsPbIBr₂ cell preserves ∼93% of its initial efficiency after 900 h of storage under ambient conditions.