Multifunctional Sulfalene additive regulates crystallization dynamics toward inverted perovskite solar cells with enhanced efficiency and stability.

The uncontrolled rapid crystallization inherent in one-step solution process for perovskite films preparation often results in poor crystalline quality and compromised stability, presenting a major obstacle to achieving high-performance perovskite solar cells (PSCs). To overcome this challenge, we propose a multifunctional additive strategy employing Sulfalene (SL), a sulfonyl-based molecule with dual π-conjugated rings, to precisely regulate crystallization dynamics and produce a high-quality crystalline perovskite film. Experimental results show that the electron-rich oxygen atoms in SL form robust coordination bonds with undercoordinated Pb, effectively modulating crystallization dynamics and extending the crystallization process. This yields perovskite films with large grain sizes and reduced internal stress, thereby suppressing non-radiative carrier recombination. In addition, the π-conjugated architecture of SL significantly optimizes energy band alignment by elevating the Fermi level and enhancing surface contact potential. Consequently, inverted PSCs incorporating SL-treated perovskite light absorbers achieve a champion power conversion efficiency (PCE) of 24.91 % (vs. 23.85 % for control), and exhibit exceptional operational stability. This work not only elucidates the dual role of π-conjugated sulfonyl additives in crystallization modulation and energy-level engineering but also provides a paradigm for designing multifunctional molecules to advance perovskite optoelectronics.