Exceeding 15% Performance with Energy Level Tuning in Tin-Based Perovskite Solar Cells

Less-toxic tin-based perovskite materials have received more attention because they are a potential alternative to toxic Pb-based perovskite materials. However, the device performance of Sn-based perovskite solar cells is still far behind that of their Pb-based counterparts. In addition to easy oxidation of Sn2+ and fast crystallization, energy level mismatch is the other important factor inhibiting the improvement of device performance. In the study, we synthesized a new material, 5-mercapto-1-methyltetrazole tin salt, SnT2, as a regulator of the energy level of Sn-based perovskites. The results show that deeper valence bands and conduction bands were detected after SnT2 addition, which can give a better energy level alignment. Furthermore, the introduction of SnT2 also achieved the reduction of trap densities and enlargement of the grain size of perovskite films. Consequently, a 15.33% device performance was realized with an open-circuit voltage of 842.6 mV, short-circuit current density of 24.72 mA cm–2, and fill factor of 0.736.