Synergistic Control of Annealing for High‐Performance FAPbBr ₃ ‐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.