Structural, Electronic, Optical, and Mechanical Properties of Cu(I)Au(III)‐Based Double Perovskites: A First‐Principles Study

Abstract

Herein, the structural, electronic, optical, and mechanical properties of Cu(I)Au(III)‐based double perovskites using first‐principles calculations are investigated. Phonon calculation results confirm that pure halide Cs2CuAuX6 (X = Cl, Br), mixed‐halide Cs2CuAuBr4Cl2 and Cs2CuAuI4Br2, and strained Cs2CuAuI6 (by 3% strain) are dynamically stable. Subsequently, the optoelectronic and mechanical properties of these compounds are calculated. The calculations reveal that Cs2CuAuX6 exhibits slightly indirect‐bandgap semiconducting behavior, with the bandgaps of 1.169, 1.191, and 1.355 eV from the HSE06 hybrid functional for X = Cl, Br, and I, respectively. Meanwhile, the bandgap of Cs2CuAuI6 decreases with the increase of strain from 1% to 3% (1.271, 1.148, and 1.037 eV, respectively). In addition, the results show that Cs2CuAuI4Br2 (EgHSE06 = 1.278 eV) has a suitable bandgap, which is close to the ideal direct bandgap. Moreover, Cs2CuAuI4Br2 exhibits strong anisotropic visible light absorption with absorption coefficients exceeding 105 cm−1 and has a relatively large dielectric constant (εxxst = εyyst = 36.27) along the ab plane. Furthermore, its Pugh's ratio (Poisson's ratio) value of 2.94(0.35) exceeds the critical value of 1.75(0.26), indicating its ductility and potential for use in flexible electronic devices.