-Phase Management of FAPbBr₃ for Semitransparent Solar Cells

Formamidinium lead bromide (FAPbBr(3)) perovskite owing to suitable wide band gap has promising application in the fields of semitransparent and tandem solar cells. However, the effect of photoinactive delta phase (delta-FAPbBr(3)) on the film and device properties is still unclear and rarely investigated. In this work, the authors find that the growth of delta-FAPbBr(3) has a strong relationship with the property of the underlayer. On the hydrophilic underlayer, crystalline delta-FAPbBr(3) is uniformly distributed in the bulk of the alpha-FAPbBr(3) film, which has a lower defect density and better carrier transport. A power conversion efficiency of 9.12% is achieved by the management of delta-FAPbBr(3) and using a phosphonate/phosphine oxide dyad additive, which is the highest value among the inverted FAPbBr(3)-based perovskite solar cells (PSCs). Moreover, the light utilization efficiency of a semitransparent device reaches 3.15%. This work provides new insights and methods for the realization of high-performance FAPbBr(3)-based PSCs.