Impact of Ternary Solvent on the Grain Size and Defects of Perovskite Layer to Realize a Stable Morphology for Efficient Inverted Solar Cells

Recent reports reveal that a smooth and uniform surface morphology can endow perovskite solar cells with excellent stability and remarkable power conversion efficiency (PCE). Herein, a ternary solvent strategy is employed using dimethylformamide (DMF), dimethyl‐sulfoxide (DMSO), and γ‐butyrolactone (GBL) to improve contact between the charge transporting layers and the perovskite layer. This approach yields enhanced surface morphology, charge extraction, and passivation. The thermally stable intermediates generated through the ternary solvent promote uniform MAPbI 3 films with a smooth surface. These intermediates reduce surface roughness, increase grain size, and fill voids or defects in MAPbI 3 due to a strong interaction of ternary solvent. The PCE with the ternary solvent (DMF:GBL:DMSO) increases to 20.23% compared to binary solvents of GBL:DMSO and DMF:DMSO. Additionally, ternary solvent engineering is beneficial from an industrial perspective for achieving a stable and uniform morphology of perovskite in large‐area device fabrication.