Lead-free layered Aurivillius-type Sn-based halide perovskite BaX[CsSnX] (X = I/Br/Cl) with an optimal band gap of ∼1.26 eV and theoretical efficiency beyond 27% for photovoltaics

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2022-05, Vol.1 (19), p.1682-1691
• Main Authors: Liu, Shi-ming, Zhong, Hong-xia, Liang, Jun-jie, Zhang, Min, Zhu, Yao-hui, Du, Juan, Guo, Wen-hui, He, Yong, Wang, Xinqiang, Shi, Jun-jie
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d1ta10822k

Sn-based perovskite solar cells (PSCs) have shown great advantages as capable alternatives to poisonous Pb-based PSCs, with impressive certified power conversion efficiencies (PCE) beyond 14%. However, their poor stability induced by oxidation has hindered the further development of Sn-based PSCs. Herein, through first-principles calculations, inorganic layered Aurivillius-type Sn-based halide perovskites Ba 2 X 2 [Cs n −1 Sn n X 3 n +1 ] (X = I/Br/Cl) have been designed, in which the [Ba 2 X 2 ] layer blocks the oxygen in air, enhancing the inoxidizability of the crystals. Ba 2 X 2 [Cs n −1 Sn n X 3 n +1 ] exhibit direct band gaps (0.84-2.20 eV), satisfying the requirements for single- and multi-junction PSCs. As the best candidate, Ba 2 Br 2 [Cs 2 Sn 3 Br 10 ] has an optimal band gap (1.26 eV), high carrier mobility (135-173 cm 2 V −1 s −1 ) and desirable absorption coefficient (∼10 5 cm −1 ). Consequently, the optimized single-junction SnO 2 /Ba 2 Br 2 [Cs 2 Sn 3 Br 10 ]/CuSbS 2 shows a record PCE of 27.7% among Sn-based PSCs, beyond the champion PCE of Pb-based PSCs (25.5%). These energetic results provide a new perspective to improve the performance of Sn-based single-junction PSCs and give a potential alternative to bottom/top PSCs in tandem devices. The layered Sn-based perovskite Ba 2 Br 2 [Cs 2 Sn 3 Br 10 ] with excellent photovoltaic properties is found. It has a bandgap of 1.26 eV and a large optical absorption and carrier mobility. The Ba 2 Br 2 [Cs 2 Sn 3 Br 10 ]-based solar cell has a high theoretical PCE of 27.7%.