Acetone-assisted precursor engineering enables low-temperature fabrication of CsPbI₂Br perovskite for efficient solar cells

Low-temperature fabrication is of vital importance for solar cells in reducing energy consumption and developing diversified device structures. Here, we present an efficient low-temperature fabrication of α-phase CsPbI₂Br via introducing a low toxicity and high volatility solvent, acetone, into the precursor to assist the nucleation and growth of perovskite. The addition of acetone significantly improves the wettability of perovskite precursor on compact TiO₂ substrate and induces strong interaction between lead iodide and dimethyl sulfoxide solvent. This in turn decreases the crystallization active energy of perovskite, resulting in a fast formation of α-phase CsPbI₂Br perovskite at 40 °C. As a result, the acetone-assisted CsPbI₂Br device gives a superior power conversion efficiency of 16.03% along with good long-term and operational stability, approaching the highest reported efficiency for CsPbI₂Br solar cells. The present study demonstrates that the rational precursor engineering is an effective strategy for low-temperature fabrication of CsPbI₂Br solar cells.