Methylammonium Chloride as a Double-Edged Sword for Efficient and Stable Perovskite Solar Cells

The additive engineering strategy promotes the efficiency of solution-processed perovskite solar cells (PSCs) over 25%. However, compositional heterogeneity and structural disorders occur in perovskite films with the addition of specific additives, making it imperative to understand the detrimental impact of additives on film quality and device performance. In this work, the double-edged sword effects of the methylammonium chloride (MACl) additive on the properties of methylammonium lead mixed-halide perovskite (MAPbI(3-x)Cl(x) ) films and PSCs are demonstrated. MAPbI(3-x)Cl(x) films suffer from undesirable morphology transition during annealing, and its impacts on the film quality including morphology, optical properties, structure, and defect evolution are systematically investigated, as well as the power conversion efficiency (PCE) evolution for related PSCs. The FAX (FA = formamidinium, X = I, Br, and Ac) post-treatment strategy is developed to inhibit the morphology transition and suppress defects by compensating for the loss of the organic components, a champion PCE of 21.49% with an impressive open-circuit voltage of 1.17 V is obtained, and remains over 95% of the initial efficiency after storing over 1200 hours. This study elucidates that understanding the additive-induced detrimental effects in halide perovskites is critical to achieve the efficient and stable PSCs.

Automated summary

This study demonstrates the double-edged sword effects of the methylammonium chloride (MACl) additive on the properties of methylammonium lead mixed-halide perovskite (MAPbI(3-x)Cl(x)) films and perovskite solar cells (PSCs). Undesirable morphology transition occurs in MAPbI(3-x)Cl(x) films during annealing, affecting the film quality, optical properties, structure, defect evolution, and power conversion efficiency (PCE) of related PSCs. A post-treatment strategy called FAX (FA = formamidinium, X = I, Br, and Ac) is developed to inhibit morphology transition and suppress defects, resulting in a champion PCE of 21.49% and impressive stability.