Anti-Solvent-Free Preparation for Efficient and Photostable Pure-Iodide Wide-Bandgap Perovskite Solar Cells.

The perovskite/silicon tandem solar cell (TSC) has attracted tremendous attention due to its potential to breakthrough the theoretical efficiency set for single-junction solar cells. However, the perovskite solar cell (PSC) designed as its top component cell suffers from severe photo-induced halide segregation owing to its mixed-halide strategy for achieving desirable wide-bandgap (1.68 eV). Developing pure-iodide wide-bandgap perovskites is a promising route to fabricate photostable perovskite/silicon TSCs. Here, we report efficient and photostable pure-iodide wide-bandgap PSCs made from an anti-solvent-free (ASF) technique. The ASF process is achieved by mixing two precursor solutions, both of which are capable of depositing corresponding perovskite films without involving anti-solvent. The mixed solution finally forms CsDMAMAPbI perovskite film with a bandgap of 1.68 eV. Furthermore, methylammonium chloride additive is applied to enhance the crystallinity and reduce the trap density of perovskite films. As a result, the pure-iodide wide-bandgap PSC delivers efficiency as high as 21.30 % with excellent photostability, the highest for this type of solar cells. The ASF method significantly improves the device reproducibility as compared with devices made from other anti-solvent methods. Our findings provide a novel recipe to prepare efficient and photostable wide-bandgap PSCs.