Solvent Gaming Chemistry to Control the Quality of Halide Perovskite Thin Films for Photovoltaics

[Image: see text] Research on solvent chemistry, particularly for halide perovskite intermediates, has been advancing the development of perovskite solar cells (PSCs) toward commercial applications. A predictive understanding of solvent effects on the perovskite formation is thus essential. This work systematically discloses the relationship among the basicity of solvents, solvent-contained intermediate structures, and intermediate-to-perovskite α-FAPbI(3) evolutions. Depending on their basicity, solvents exhibit their own favorite bonding selection with FA(+) or Pb(2+) cations by forming either hydrogen bonds or coordination bonds, resulting in two different kinds of intermediate structures. While both intermediates can be evolved into α-FAPbI(3) below the δ-to-α thermodynamic temperature, the hydrogen-bond-favorable kind could form defect-less α-FAPbI(3) via sidestepping the break of strong coordination bonds. The disclosed solvent gaming mechanism guides the solvent selection for fabricating high-quality perovskite films and thus high-performance PSCs and modules.