Synergistic regulation of crystallization and the buried interface in CsxFA1−xPbI3 perovskite photovoltaics using a multifunctional sulfonyl–ammonium additive

The fabrication of high-quality CsxFA1−xPbI3-based perovskite films is often limited by inhomogeneous crystallization and concomitant numerous defects. Here, we introduce 2-aminoethylmethylsulfone hydrochloride (AEMS) as a multifunctional ligand into the perovskite precursor solution to mitigate these issues. It is demonstrated that the O 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 SO and NH3+ groups in AEMS strongly interact with the perovskite components, broadening the processing window and promoting preferentially (100)-oriented crystal growth, which significantly enhances the crystallinity of the CsxFA1−xPbI3 films. Furthermore, AEMS spontaneously aggregates at the buried interface, where it selectively passivates interfacial defects, optimizes energy level alignment, and suppresses nonradiative recombination. As a result, Cs0.05FA0.95PbI3-based inverted perovskite solar cells achieve a power conversion efficiency (PCE) of 26.91% (certified 26.80%). This strategy also demonstrates excellent adaptability, yielding outstanding PCEs of 23.24% for mini-modules (an aperture area of 11.1 cm2) and 24.90% for flexible devices. Crucially, the encapsulated devices maintain 93% of their initial PCEs after 2,500 h of 1-sun operation at 65 °C in ambient air.