Green Solution-Processed Tin-Based Perovskite Films for Lead-Free Planar Photovoltaic Devices.

The eco-friendly Sn-based perovskites have attracted more and more attention in lead-free perovskite photovoltaic field. However, the device performance and reproducibility are greatly challenged in preparing high-quality perovskite films. Here, we fabricated uniform and dense Sn-based perovskite films via a green gas pump treatment technology. Remarkably, we successfully fabricated a large-area (>20 cm2) Sn-based perovskite film with a mirror-like surface, which is the largest Sn-based perovskite film ever reported. Besides, we found that the phase separation phenomenon induced by excess SnF2 was eliminated when the pressure is 1500 Pa. Finally, we fabricated highly reproducible Sn-based solar cells and obtained an inspiring efficiency of 1.85%, which is the highest reported efficiency for Sn-based devices with a configuration of fluorine-doped tin oxide/compact TiO2/perovskite/hole transport material/electrode. Our results demonstrate the feasibility of using gas pump treatment technique to prepare high-quality Sn-based perovskite films, which paves a way for large-scale green manufacturing of Sn-based perovskite solar cells in the future.