Electronic Structure Calculations of Alkali Lead Iodide APbI₃ (A=Li, Na, K, Rb or Cs) using Density Functional Theory (DFT) Method

The electronic structures of alkali lead iodide APbI₃ (where A = Li, Na, K, Rb or Cs), as one type of all-inorganic perovskites, have been investigated by the first-principles calculations based on Density Functional Theory (DFT) using Quantum Espresso package. The calculation results show that their electronic structures are slightly affected by the alkali atom A, leading to a slight variation in band gap and density of states (DOS) distribution. Prior to electronic structure calculations, the cell structures were optimized through the scheme of VC-relax calculation, including the optimization of kinetic energy cut-off and k-point. Their energy gaps were found to be in the range of 1.31 eV - 1.43 eV, despite their lattice parameters were significantly different ranging from 5.1 Å up to 6.3Å. In general, these calculation results show that these alkali lead iodide perovskites are semiconductor materials and applicable as a sunlight absorber in solar cells, as reported elsewhere. (paper)