Electronic Structure and Optical Properties of Vacancy-Ordered Double Perovskites Cs<sub>2</sub>Pd Br<i><sub>x</sub></i>Cl<sub>6–<i>x</i></sub> by First-Principles Calculation
Ziyan Wang, Yi Chen, Chongyang Zhang, Dan Wang, Pei Liang, Hong Zhang, Rong‐Jun Xie, Le Wang
Abstract
Vacancy-ordered double perovskites, having a great application in optoelectronic and thermoelectric devices, are variants of metal-halide perovskites. The PBE and HSE06 functionals for the first-principles calculation were used to investigate the electronic structures, optical properties, possible intrinsic defects, and formation energies of the vacancy-ordered double perovskites Cs2PdBrxCl6–x (x = 1, 2, 3, ..., 6). All the compounds had a direct band gap, and the band gap increased from 1.566 eV for Cs2PdBr6 to 2.675 eV for Cs2PdCl6 when Br atoms are replaced with Cl atoms. The absorption of these compounds blue-shifted with increasing Cl:Br ratio, and higher absorption coefficients can thus be acquired in the ultraviolet region. The defect calculations showed that the formation energies of VCs, VPd, and CsPd were low, and the Fermi level was pinned near the valence band maximum. The results indicate that vacancy-ordered double perovskites are ideal candidates for lead-free solar cells with high conversion efficiencies.