Inorganic narrow bandgap CsPb0.4Sn0.6I2.4Br0.6 perovskite solar cells with exceptional efficiency

Abstract

The instability of organic/inorganic hybrid perovskite solar cells (PSCs) has motivated the development of the inorganic halide PSCs. However, the representative inorganic CsPbI 3 still suffers from phase instability in ambient air and an unfavorable wide bandgap (1.75 eV), thereby limiting its efficiency. In this study, a binary metal composition of Pb:Sn = 4:6 in CsPb 1-x Sn x I 3 is found to stabilize the cubic CsPbI 3 phase and reduce its bandgap. Based on the parental CsPb 0.4 Sn 0.6 I 3 , compositional engineering is further conducted for CsPb 0.4 Sn 0.6 I 3-y Br y perovskites. After introducing a suitable Br content (y = 0.6), there are remarkable improvements in the crystalline quality and a denser morphology in the perovskite films. Furthermore, in the novel inorganic CsPb 0.4 Sn 0.6 I 2.4 Br 0.6 perovskite, trap-assisted recombination is effectively suppressed, with a desirable narrow bandgap of 1.35 eV. As a result, the corresponding PSC delivered an unprecedented efficiency of 12.34%, which is the highest among the inorganic Sn-rich (Sn > 50%) PSCs reported to date. Additionally, the unencapsulated PSC demonstrates impressive long-term air stability, which exceeds the performance of 100% Pb-based inorganic CsPbI 3 and/or CsPbI 2 Br PSCs reported. This near-infrared absorbing (~930 nm) inorganic PSC with exceptional efficiency, durability and Pb-reduction generates a promising route for further progress of perovskite-based photovoltaics. • All-inorganic CsPbI 3 suffers from phase instability, wide bandgap, and toxic-Pb. • The partial Pb-replacement by Sn (x = 0.6) stabilizes the cubic CsPbI 3 and reduces bandgap. • The suitable Br addition suppresses trap-assisted recombination of CsPb 0.4 Sn 0.6 I 3 with a narrow bandgap of 1.35 eV. • A record efficiency of 12.34% for inorganic Sn-rich perovskite solar cell is demonstrated based on CsPb 0.4 Sn 0.6 I 2.4 Br 0.6 .