The effect of anion exchange on the electronic and optical properties of vacancy ordered double perovskites K₂PdX₆ (X = Cl, Br, I) using first principle calculations

Recent studies are confirmed that lead-free perovskite is a possible alternative solution for conventional hybrid lead-based perovskites to achieve better photovoltaic efficiency. This work investigates the structural, mechanical, electronic, and optical properties of vacancy ordered double perovskite of K₂PdX₆ (X = Cl, Br, I) for photovoltaic applications through the density functional theory at the HSE06 level of theory. The bond length of Pd-X is linearly increased while exchanging the anions from Cl to I. The mechanical study reveals that the vacancy-ordered double perovskites K₂PdCl₆, K₂PdBr₆, and K₂PdI₆ are elastically classified as ductile materials. The K₂PdBr₆ hold a favourable bandgap of 1.62 eV for single junctions solar cell applications. The studied perovskite bandgaps depend on the Pd-4d, s and p orbitals of anions. The optical study uncover that the studied perovskites are higher optical absorption in the visible regions. Based on calculated results, we conclude that these K₂PdBr₆ vacancy ordered double perovskites might be suitable material for photovoltaic applications.