Mixed Chalcogenide‐Halides for Stable, Lead‐Free and Defect‐Tolerant Photovoltaics: Computational Screening and Experimental Validation of CuBiSCl2 with Ideal Band Gap

• Published in: Advanced functional materials Vol. 32; no. 27
• Main Authors: Ming, Chen, Chen, Zhizhong, Zhang, Fan, Gong, Shuiping, Wu, Xiaowei, Jiang, Jie, Ye, Tang, Xu, Qing, Yang, Ke, Wang, Liang, Cao, Xun, Yang, Songwang, Zhang, Shengbai, Zhang, Yong, Shi, Jian, Sun, Yi‐Yang
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.07.2022
• Subjects: Absorption; computational screening; defect tolerance; Electronic structure; Energy conversion efficiency; Energy gap; Halides; Halogens; Lead compounds; lead‐free perovskites; Materials science; Metal halides; Mixed anions; Open circuit voltage; optical absorption; Optoelectronics; Perovskite structure; Perovskites; Photovoltaic cells; photovoltaics; Relative humidity; Screening; Solar cells; Stability; Thermal decomposition; Toxicity
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202112682

Lead halide perovskites have emerged as promising photovoltaic (PV) materials owing to their superior optoelectronic properties. However, they suffer from poor stability and potential toxicity. Here, computational screening with experimental synthesis is combined to explore stable, lead‐free, and defect‐tolerant PV materials. Heavy cations with lone‐pair electrons and mixed anions of chalcogens and halogens as a descriptor for simultaneous realization of defect tolerance and high stability are adopted. Together with the criteria of possessing direct band gap and optimal gap value, the inorganic material database is screened and CuBiSCl2 in the post‐perovskite structure is identified with an ideal band gap of 1.37 eV. The electronic structure and defect calculations suggest its defect‐tolerant characteristics. By optical absorption measurement, its band gap is confirmed to be ≈1.44 eV, with strong absorption near the band edge. The material is stable against thermal decomposition up to 300 °C and can survive from 25 days of storage at ambient conditions with 60% relative humidity. Prototype solar cells are fabricated and demonstrate an open circuit voltage of 1.09 V and a power conversion efficiency of 1.00%. With the excellent properties above, CuBiSCl2 is proposed to be a promising candidate for PV application. Combined computational and experimental study identifies mixed‐anion compound CuBiSCl2 with the post‐perovskite structure as a promising defect‐tolerant photovoltaic material. Experiment verifies its strong optical absorption with an onset near 1.44 eV and enhanced stability over lead halide perovskites.