Exceeding 15% Performance with Energy Level Tuning in Tin-Based Perovskite Solar Cells
Liang Wang, Hua̅n Bì, Jiaqi Liu, Yuyao Wei, Zheng Zhang, Mengmeng Chen, Ajay Kumar Baranwal, Gaurav Kapil, Takeshi Kitamura, Shuzhang Yang, Qingqing Miao, Qing Shen, Tingli Ma, Shuzi Hayase
Abstract
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 Sn 2+ 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, SnT 2, as a regulator of the energy level of Sn-based perovskites. The results show that deeper valence bands and conduction bands were detected after SnT 2 addition, which can give a better energy level alignment. Furthermore, the introduction of SnT 2 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.