First-Principles Predictions of Structural, Mechanical, and Optoelectronic Properties of Se-Based Double Perovskites A<sub>2</sub>SeX<sub>6</sub> (A = Rb, K; X = Cl, Br, I)
Jiahao Li, Liping Sun, Xiuhong Cao, Jing Chang
Abstract
The toxicity of lead and the instability of lead-based perovskite materials in the air are two key challenges in emerging Pb-based inorganic perovskite solar cells. Thus, the development of lead-free and stabilized inorganic perovskite materials is of great interest. In this work, the structural, ductility, and optoelectronic properties of Se-based double perovskites A 2 SeX 6 (A = Rb, K; X = Cl, Br, I) have been studied for the first time by first-principles calculations to determine their potential use in optoelectronic sectors. Results reveal that these new series of A 2 SeX 6 (A = Rb, K; X = Cl, Br, I) double perovskites are structural and mechanical stability. Their ductility increases as the halogen atom goes from Cl to I. Especially, the K 2 SeI 6 possesses better ductility than other double perovskites. Electronic structure calculations exhibit that these new perovskite compounds are indirect band gap semiconductors. The Rb 2 SeI 6 and K 2 SeI 6 have more suitable bandgaps (1.24 and 1.16 eV) and smaller carrier masses, which are suitable for absorber layers of solar cells, while A 2 SeCl 6 and A 2 SeBr 6 are suitable for fabricating the optoelectronic devices in the ultraviolet region due to the wide gap. Furthermore, all these A 2 SeX 6 compounds exhibit excellent optical properties with light absorption coefficients over 10 5 cm –1 . Especially, the Rb 2 SeI 6 and K 2 SeI 6 have more excellent absorption spectra throughout the whole visible region. These results show that both Rb 2 SeI 6 and K 2 SeI 6 are potential candidates for absorption layer materials of solar cells, and A 2 SeCl 6 and A 2 SeBr 6 are suitable for other optoelectronic devices, such as photodetectors, light-emitting diodes, and so on.