Electronic, optical, and thermoelectric properties of perovskite variants A 2 BX 6 : Insight and design via first‐principles calculations

Summary Lead halide perovskites are considered as a material of choice for solar cell applications. However, there are challenges: organic cations in halide perovskites are unstable, and lead is toxic. To address these issues, we propose and investigate some potential alternatives to lead in the form of A 2 BX 6 perovskites using the first‐principles calculations. Besides simple approximation potentials, we use a highly successful hybrid functional HSE06, to calculate the electronic, optical, and thermoelectric properties of A 2 PdI 6 (A = K, Rb, and Cs). Our calculations show that K 2 PdI 6 , Rb 2 PdI 6 , and Cs 2 PdI 6 , are narrow bandgap semiconductors with bandgap of 0.8, 0.92, and 0.9 eV, respectively. The valence band maximum (VBM) of A 2 PdI 6 is mainly composed of I‐5 p orbitals while the conduction band minimum (CBM) is formed of Pd‐4 d and I‐5 p orbitals . Due to the ideal bandgap and excellent light absorption, Rb 2 PdI 6 stands out as a potential candidate for usability in tandem solar cells. In addition, p‐type doping at a carrier concentration of 1 × 10 18 cm −3 makes these perovskites a material of choice for thermoelectric energy applications.