Nucleation‐Crystallization Synergistic Strategy Enables Efficient and Stable Wide‐Bandgap Perovskite Mini‐Modules

ABSTRACT Wide‐bandgap perovskite solar cells (WBG‐PSCs) are indispensable top‐cell candidates for perovskite/silicon tandems that can overcome the theoretical limit of single‐junction silicon solar cells. Their efficiencies, however, are hindered by the intrinsically rapid and non‐uniform crystallization of mixed‐cation, mixed‐halide absorbers when upscaling on large‐area substrates. This results in an increase in interfacial defects and bulk traps that compromise both efficiency and stability. Herein, we introduce 4‐(trifluoromethyl)aniline hydrochloride (4‐TFPA) into perovskite precursors to regulate rapid nucleation and slow crystallization of perovskite absorbers when transforming from a precursor solution to a solid film. This is enabled by the dual interaction of 4‐TFPA with both lead (Pb 2+ ) and formamidinium (FA + ) ions—weak coordination with Pb 2+ and strong hydrogen bonding with FA + . The modified nucleation and crystallization processes are responsible for the reduction of defects in mixed‐cation, mixed‐halide perovskite absorbers. Moreover, the residual 4‐TFPA in the final absorber further passivates defects and optimizes band alignment at the perovskite/electron‐transport interface. The resulting perovskite mini‐modules deliver a power‐conversion efficiency of 21.90% (≈1.68 eV) and 22.50% (≈1.53 eV) on an aperture area of 22.96 cm 2 under sunlight illumination. Encapsulated mini‐modules retain over 80% of their initial efficiencies for >700 h under both ISOS‐D‐1 and ISOS‐L‐1 protocols.