Modeling of Lead Halide Perovskites for Photovoltaic Applications
  We report first-principles calculations, using the full potential linear augmented plane wave method, on six lead halide semiconductors, namely, CH3NH3PbI3, CH3NH3PbBr3, CsPbX3 (X=Cl, Br, I), and RbPbI3. Exchange is modeled using the modified Becke-Johnson potential. With an appropriate choice of the parameter that defines this potential, an excellent agreement is obtained between calculated and experimental band gaps of the six compounds. We comment on the possibility that the cubic phase of CsPbI3, under hydrostatic pressure, could be a topological insulator. 
Radi A. Jishi, Oliver B. Ta, and Adel A. Sharif
cond-mat.mtrl-sci