First-principles study on optoelectronic properties of lead-free inorganic iodide double perovskite Cs2AgSb1-xGaxI6

Lead-based organic-inorganic hybrid halide perovskites have achieved great success in the field of optoelectronics over the past few years, however the toxicity and instability hinder its rapid development. In order to overcome the shortcomings, we proposed newfangled mixed metal double perovskites Cs2AgSb1-xGaxI6 (x = 0, 0.25, 0.5, 0.75, 1) to investigate their geometrical, electronic structures and optical properties to figure out their application in the optoelectronic field. The band gaps, carrier effective masses and optical absorption were calculated and discussed with the increase of the content of Ga on the basis of the first-principles methods. The results reveal the semiconductor Cs2AgSb0.5Ga0.5I6 demonstrates the lowest band gap and hole effective masses while the Cs2AgGaI6 exhibits metal behavior. We speculate the content of Ga and positions of Ga atoms play important roles to influence the optoelectronic properties. The above design strategy will provide new perspectives for searching environmental-friendly lead-free perovskite materials with tunable photoelectric properties.