The tunable electronic structure and optical properties of vacancy-ordered double perovskites Tl2PdBrxCl6-x (x = 0, 2, 4, 6)

Abstract

Double perovskites show excellent stability and suitable band gaps, which are superior materials for solar cell applications. In this work, the structure, electronic, and optical properties of vacancy-ordered double perovskites Tl2PdBrxCl6-x (x = 0, 2, 4, 6) are explored by first-principles calculations. The tunable band gaps of the studied compounds are in the range of 1.3–2.2 eV. The band gap is narrowed from Tl2PdCl6 to Tl2PdBr6. Moreover, the band gap of Tl2PdCl6 can be adjusted to the appropriate band gap value through minor Br doping. High concentration of Br doping results in a small band gap variation. The visible light absorption capacity is significantly enhanced from Tl2PdCl6 to Tl2PdBr6. The results show that three compounds including Tl2PdBr2Cl4, Tl2PdBr4Cl2, and Tl2PdBr6 are promising materials for potential optoelectronic applications.