Low-Dimensional Templates and Delayed Crystallization for High-Quality Tin-Based Perovskite Films

The quasi-2D tin-based perovskite is a prominent candidate for p-type perovskite semiconductor materials because of their remarkable thermodynamic stability and diminished ion migration tendencies. However, the competitive growth of low-dimensional and high-dimensional phases in quasi-2D perovskites leads to structural disorder and poor crystal orientation, thereby forming defective films and further impacting charge carrier transport. Here, we introduce a strategy to selectively promote the formation of high-quality PEA ₂ FA _n − 1 Sn _n I _3n−1 SCN ₂ (n = 2) templates by incorporating PEASCN into the perovskite precursor solution. By substituting formamdinium iodide (FAI) with formamidinium formate (FAHCOO) and ammonium iodide (NH ₄ I), we effectively inhibit the growth of 3D FASnI ₃ , thus achieving control over crystallization kinetics. This approach facilitates the growth of low-dimensional templates that guide the formation of high-dimensional phases during the annealing process. The resulting optimized perovskite films exhibit a well-defined vertical crystallographic orientation and reduced defect density, which significantly enhance charge carrier transport. The fabricated field-effect transistors demonstrate a maximum mobility of 43 cm ² V ^− 1 s ^− 1 and an on/off ratio exceeding 10 ⁸ . Furthermore, the unencapsulated devices show outstanding operational and environmental stability, maintaining performance for over 30 days. These results offer new insights into the material engineering of tin-based perovskite films and highlight the potential for high-performance and stable devices.