Exceeding\n15% Performance with Energy Level Tuning\nin Tin-Based Perovskite Solar Cells

Less-toxic tin-based perovskite materials have received\nmore attention\nbecause they are a potential alternative to toxic Pb-based perovskite\nmaterials. However, the device performance of Sn-based perovskite\nsolar cells is still far behind that of their Pb-based counterparts.\nIn addition to easy oxidation of Sn<sup>2+</sup> and fast crystallization,\nenergy level mismatch is the other important factor inhibiting the\nimprovement of device performance. In the study, we synthesized a\nnew material, 5-mercapto-1-methyltetrazole tin salt, SnT<sub>2</sub>, as a regulator of the energy level of Sn-based perovskites. The\nresults show that deeper valence bands and conduction bands were detected\nafter SnT<sub>2</sub> addition, which can give a better energy level\nalignment. Furthermore, the introduction of SnT<sub>2</sub> also achieved\nthe reduction of trap densities and enlargement of the grain size\nof perovskite films. Consequently, a 15.33% device performance was\nrealized with an open-circuit voltage of 842.6 mV, short-circuit current\ndensity of 24.72 mA cm<sup>–2</sup>, and fill factor of 0.736.