Trifluorotoluene Changes the Morphology of PbI2 to Induce the Crystallization of Perovskites

Perovskite solar cells (PSCs) have achieved remarkable progress in power conversion efficiency (PCE), yet precise control over perovskite film crystallinity and morphology remains challenging. Conventional fabrication methods often yield films with small grains, excessive grain boundaries, and defect-related performance losses. Here, we demonstrate that dynamic spin coating of trifluorotoluene (TFT) during the two-step deposition process induces vertical stacking of PbI 2 crystals, generating nanochannels that facilitate organic salt infiltration. This mechanism promotes the growth of high-quality crystalline, low-defect-density perovskite films with uniform morphology and suppressed pinhole formation. The optimized films enable the production of PSCs (FTO/SnO 2 /perovskite/Spiro-OMeTAD/Ag) with optimized PCE of 25.32%, accompanied by exceptional operational stability under continuous illumination. Crucially, this TFT-assisted strategy is compatible with diverse solution-based fabrication techniques, offering a universal pathway to enhance the reproducibility and performance of perovskite photovoltaics.