Homogenizing\nNucleation and Growth of Tin Perovskite\nby Polarity-Free Trithiane Coordination Molecule for Efficient and\nStable Photovoltaics

Tin\n(Sn)-based perovskite solar cells (TPSCs) have garnered\nsignificant\nattention recently, with power conversion efficiencies (PCEs) approaching\n16%. Nevertheless, for Sn-based perovskites, their rapid crystallization\nand easy Sn<sup>2+</sup> oxidation are always annoying for fabricating\nefficient and stable TPSCs. Coordination engineering has been developed\nfor retarding the crystallization rate and Sn<sup>2+</sup> passivation,\nbut the homogeneous crystallization of Sn-based perovskites is still\nchallenging due to the asymmetric and polar nature of currently used\nligands. Here, a polarity-free S-containing symmetric molecule, 1,3,5-trithiane\n(TT), is developed to regulate the crystallization of FASnI<sub>3</sub>. Nonpolar TT with three symmetric S atoms shows equally strong coordination\nwith Sn<sup>2+</sup>, which enhances the environment stability of\nthe precursor and promotes the homogeneous nucleation and retarded\ngrowth of FASnI<sub>3</sub> crystals. Consequently, TT-based TPSCs\nexhibit an improved PCE from 9.02% to 12.87% with robust stability.\nThis study highlights the critical role of ligand polarity in controlling\nthe crystallization behavior of efficient TPSCs.