Solvent Engineering for High-Performance Two-Dimensional Ruddlesden–Popper CsPbI₃ Solar Cells

Two-dimensional (2D) Ruddlesden–Popper (RP) CsPbI3 exhibits enhanced phase stability compared with 3D CsPbI3. However, the issue of uncontrollable crystallization process limits its photovoltaic performance. Here, influence a binary mixed solvent on film quality and properties (PEA)2Cs4Pb5I16 (n = 5) is studied in detail. It demonstrated that rate crystal growth can be controlled by adjusting amount dimethyl sulfoxide (DMSO). Optimizing composition adding 10% DMSO pure formamide (DMF) leads to perfect coverage, larger flaky 2D grains, reduced grain boundaries, better vertical orientation substrate due formation more stable intermediate phase. This form good interface contact, which beneficial charge transport/extraction between TiO2 (electron transport layer, ETL) perovskite, finally resulting improved device The enhancement power conversion efficiency optimized based DMF/DMSO (9:1) 3.57% reference DMF. work illustrates role kinetics RP offers simple effective method for high-performance solar cells.