Phase Diagrams and Stability of Lead-Free Halide Double Perovskites Cs2BB′X6: B = Sb and Bi, B′ = Cu, Ag, and Au, and X = Cl, Br, and I

• Published in: Journal of physical chemistry. C Vol. 122; no. 1; pp. 158 - 170
• Main Authors: Filip, Marina R, Liu, Xinlei, Miglio, Anna, Hautier, Geoffroy, Giustino, Feliciano
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.01.2018
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b10370

Lead-free pnictogen/noble metal halide double perovskites Cs2BiAgCl6, Cs2BiAgBr6, and Cs2SbAgCl6 are some of the most promising environmentally friendly alternatives to lead–halide perovskites. However, due to their relatively large band gaps (1.9–2.2 eV), they are not yet competitive candidates for use in photovoltaic devices. In this work, we perform a systematic study of the thermodynamic stability of the entire family of Cs2BB′X6 compounds (B = Bi and Sb, B′ = Cu, Ag, and Au, and X = Cl, Br, and I), and we explore the possibility of chemical mixing as a route to stabilize pnictogen/noble metal halide perovskites with low band gaps. Our calculations indicate that Cs2BiAg1–x Cu x Cl6 mixes should be amenable to synthesis and could reduce the band gap down to 1.6–1.9 eV.