High-Efficiency Semitransparent Perovskite Solar Cells Enabled by Controlling the Crystallization of Ultrathin Films

Semitransparent perovskite solar cells (ST-PSCs) have emerged as an exciting prospect due to their applications in future smart buildings. Semitransparency is typically realized through the use of wide bandgap perovskite materials with a reduced thickness. In this study, we demonstrate a methylammonium (MA)-free wide bandgap perovskite for the active layer of ST-PSCs. However, achieving defect-free highly crystalline films with lower film thickness has been challenging. We report a precursor engineering approach based on an organic ammonium salt tryptamine hydro bromide (TABr) with an anion and a cation group to passivate both halide and metal ion vacancies. TABr molecules regulate the crystallization kinetics and offer highly crystalline thinner perovskite films. The champion device exhibits a power conversion efficiency (PCE) of 14.21%, along with an average visible transparency (AVT) of ∼22%. This work provides an efficient method to enhance the performance of ST-PSCs with high AVT for application in building integrated photovoltaics (BIPVs).