Synergistic Control of Annealing for High-Performance FAPbBr3-Based Semitransparent Perovskite Solar Cells

Perovskite solar cells (PSCs) are considered highly promising for next-generation building-integrated photovoltaic (BIPV) applications due to their abundant raw materials, tunable transparency, and cost-efficient fabrication through printable processes. Herein, a dual-architecture strategy for formamidinium lead bromide (FAPbBr 3 ) perovskite solar cells is established. We achieved a record 8.77% power conversion efficiency (PCE) with 1.39 V open-circuit voltage ( V OC ) in carbon-based electrode devices and 3.25% PCE with 35.03% average visible transmittance (AVT) in semitransparent configurations. Through systematic optimization of annealing temperature (60–100°C) and duration (10–40 min), we identify 80°C/20 min as the ideal condition, yielding large grains with complete surface coverage, enhanced photoluminescence intensity indicating suppressed nonradiative recombination and optimal phase purity. The carbon-based electrode device (ITO/SnO 2 /FAPbBr 3 /C) achieves exceptional performance ( J sc = 9.35 mAcm −2 , FF = 67.4%), while the identical perovskite layer transferred to a Spiro-OMeTAD/MoO 3 /Ag/MoO 3 stack attains functional semitransparency (CIE (0.49,0.44)). These findings pave the way for the development of esthetically integrated and energy-efficient building-integrated solar solutions, with a clear path toward further optimization and commercialization of perovskite-based BIPV systems.