Controlling the Intermediate Phase to Improve the Crystallinity and Orientation of Cs3Sb2ClxI9‐x Films for Efficient Solar Cells

Abstract Lead‐free 2D antimony‐based halide perovskites with excellent optoelectronic properties, low toxicity, and good intrinsic stability are promising for photovoltaic devices. However, the power conversion efficiency (PCE) of antimony‐based perovskite solar cells (PSCs) is still lower than 3% due to the poor crystallinity and random orientation. Herein, it is found that the Cs3Sb2ClxI9‐x films prepared by adding methylamine chloride as an additive to the precursor solution can form a mixed intermediate phase with 0D dimer phase and 2D layered phase after low pressure treatment. During the annealing process, the 0D dimer phase will completely transition to 2D layered phase due to the partial replacement of I by Cl. Compared to adding SbCl3 directly, this method considerably increases the crystallinity of Cs3Sb2IxCl9‐x films. The obtained films have a preferential orientation along the (201) direction, which is beneficial for charge carrier transportation. Consequently, the champion device shows a PCE of 3.2%, which is one of the highest efficiencies achieved for inorganic Sb‐based PSCs with the n‐i‐p architecture to date.