Seeking for Cost-Effective Tin Iodide Source toward Efficient Lead-Free Tin Triiodide Perovskite Solar Cells: Advances and Prospects

Tin triiodide perovskite (TTPs), as alternatives to their Pb counterparts, have shown great promise in photovoltaic application, and the power conversion efficiency (PCE) of Pb-free TTPs-based perovskite solar cells (PSCs) has recently been observed approaching 15%. Nevertheless, to realize the future commercialization of TTPs-based PSCs, it is still challenging to further improve the device performance, while the high cost of tin iodide (SnI2) source also remains a big concern. Therefore, seeking for a cost-effective SnI2 source has been one of the most important topics during the development course of TTPs-based PSCs. In this topical Review, we summarize the advanced studies focusing on developing cost-effective SnI2 sources for TTPs-based PSCs. Various SnI2 materials currently used for fabricating efficient TTPs-based PSCs are introduced, including commercial SnI2, purified commercial SnI2, and chemically synthesized SnI2. Also, the impact of different SnI2 sources on the crystallization process and properties of the TTPs films is discussed. At last, the current challenges and future prospects regarding the SnI2 source engineering of TTPs-based PSCs are provided. This Review could guide the further development of TTPs-based perovskite in the application of low-cost, efficient, and stable optoelectronic devices.