First-principles study on the electronic properties of perovskites MASnaPb(1 - a)XbY(3 - b) (X, Y= Cl, Br, I)

According to the first principles, the Cambridge Sequential Total Energy Package (CASTEP) program and Density Functional Theory (DFT) calculation method are used to study the energy band structures and density of states (DOS) through atomic replacement in MASn(a)Pb((1-a))X(b)Y((3-b)) (X, Y= Cl, Br, I) perovskites. The factors affecting bandgaps of MASn(a)Pb((1-a))X(b)Y((3-b)) perovskites has been analyzed from the DOS and the atomic point of view, to explore the energy band regulation method of MASn(a)Pb((1-a))X(b)Y((3-b)) perovskites. We found that the band gap decreases as the halogenic weighted mean radius increases. When we study the substitutions for Sn and Pb, we found that the bandgaps of MASn(a)Pb((1-a))X(b)Y((3-b)) perovskites varies with substitution ratios, and the results showing that they may have a significant impact on expanding the absorption edge of single-junction solar cells and better lattice compatibility for tandem solar cells. These variations show that the band gap of perovskites is not only related to the p orbital electron motion of B and X atoms as formula of ABX(3), but also changes with their electronic motion ability. We simulated 21 types of MASn(a)Pb((1-a))X(b)Y((3-b)) perovskites to find out their changing rules and application prospects which may enlighten other researchers for band structure regulation and crystal structure selective in their experiment.