(C₆H₅NH₃)BiI₄: A lead-free perovskite with >330 days humidity stability for optoelectronic applications

A key challenge in the eco-friendly optoelectronic materials field is to find highly stable and nontoxic perovskite materials. Here, we report the optoelectronic properties and stability of the (C₆H₅NH₃)BiI₄ perovskite material. Using an eco-friendly gas pump treatment technique, a dense and pinhole-free (C₆H₅NH₃)BiI₄ film was fabricated. Remarkably, a large-area (>20 cm²) Bi-based perovskite film was obtained, which is the largest Bi-based perovskite film ever reported. Besides, the (C₆H₅NH₃)BiI₄ perovskite exhibits good solubility in ethanol, which is a safe and eco-friendly solvent. Thermogravimetric analysis results show the beginning of weight loss at ∼184 °C, suggesting excellent heat stability of this material. Most importantly, the (C₆H₅NH₃)BiI₄ material can tolerate continuous moisture exposure for 334 days in ambient air owing to the presence of a hydrophobic organic chain. To the best of our knowledge, this is the longest moisture stability reported for lead-free perovskite materials so far. This work paves the way for realizing highly stable and nontoxic perovskite materials for potential optoelectronic applications.