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 (SnI 2 ) source also remains a big concern. Therefore, seeking for a cost-effective SnI 2 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 SnI 2 sources for TTPs-based PSCs. Various SnI 2 materials currently used for fabricating efficient TTPs-based PSCs are introduced, including commercial SnI 2, purified commercial SnI 2, and chemically synthesized SnI 2 . Also, the impact of different SnI 2 sources on the crystallization process and properties of the TTPs films is discussed. At last, the current challenges and future prospects regarding the SnI 2 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.