Bandgap engineering and optoelectronic properties of all-inorganic lead-free Pd-based double perovskites

Abstract

The various physical properties of lead-free double perovskites A2PdX6 (A = K, Rb, Cs; X = Cl, Br, I) are revealed for the first time. The calculated structural parameters of these Pd-based compounds are consistent with the experimental data. It is likely to possess a tetragonal structure for K2PdI6 at room temperature. Cs2PdBr6 is dynamically stable when the pressure is in the range of 0–6.95 GPa. The mechanical properties are analysed and all the compounds are mechanically stable. The band gap trend of the A2PdX6 compound is identified when the A-site cation and halide anion are varied. Three A2PdBr6 compounds exhibit suitable band gaps for photovoltaic applications. An optimum band gap can be achieved for Cs2PdBr6 when the moderate pressure is applied. In addition, the electron shows better mobility than that of the hole for three A2PdBr6 compounds. The optical absorption coefficient of the A2PdBr6 compound is improved when the A-site cation changes from Cs to Rb to K. Applying pressure is beneficial to enhance light absorption capacity of Cs2PdBr6. The findings of this work can provide guidance for the design of potential A2PdBr6 compounds for photovoltaic applications.

Keywords

• Pd-based double perovskite
• Mechanical properties
• Suitable band gap
• Optical coefficient