TiO2–ZnS Cascade Electron Transport Layer for Efficient Formamidinium Tin Iodide Perovskite Solar Cells
Achieving high open-circuit voltage ( V oc ) for tin-based perovskite solar cells is challenging. Here, we demonstrate that a ZnS interfacial layer can improve the V oc and photovoltaic performance of formamidinium tin iodide (FASnI 3 ) perovskite solar cells. The TiO 2 –ZnS electron transporting layer (ETL) with cascade conduction band structure can effectively reduce the interfacial charge recombination and facilitate electron transfer. Our best-performing FASnI 3 perovskite solar cell using the cascaded TiO 2 –ZnS ETL has achieved a power conversion efficiency of 5.27%, with a higher V oc of 0.380 V, a short-circuit current density of 23.09 mA cm –2, and a fill factor of 60.01%. The cascade structure is further validated with a TiO 2 –CdS ETL. Our results suggest a new approach for further improving the performance of tin-based perovskite solar cells with a higher V oc .