Defining the topological influencers and predictive principles to engineer the band structure of halide perovskites
【Abstract】
Complex quantum coupling phenomena of halide perovskites are examined through ab initio calculations and exact diagonalization of model Hamiltonians to formulate a set of fundamental guiding rules to engineer the band gap through strain. The band-gap tuning in halides is crucial for photovoltaic applications and for establishing nontrivial electronic states. Using CsSnI3 as the prototype material, we show that in the cubic phase, the band gap reduces irrespective of the nature of strain. However, for the tetragonal phase, it reduces with tensile strain and increases with compressive strain, while the reverse is the case for the orthorhombic phase. The reduction can give rise to negative band gap in the cubic and tetragonal phases leading to normal to topological insulator phase transition. Also, these halides tend to form a stability plateau in a space spanned by strain and octahedral rotation. In this plateau, with negligible cost to the total energy, the band gap can be varied in a range of 1 eV. Furthermore, we present a descriptor model for the perovskite to simulate their band gap with strain and rotation. Analysis of band topology through model Hamiltonians led to the conceptualization of topological influencers that provide a quantitative measure of the contribution of each chemical bonding towards establishing a normal or topological insulator phase. On the technical aspect, we show that a four orbital based basis set (Sn−{s,p} for CsSnI3) is sufficient to construct the model Hamiltonian which can explain the electronic structure of each polymorph of halide perovskites.
【Author】
Ravi Kashikar, Mayank Gupta, B. R. K. Nanda
【Journal】
Physical Review B(IF：3.7) Time：2020-04-04
