Study of the solar perovskite CsMBr3 (M=Pb or Ge) photovoltaic materials: Band-gap engineering

In this paper, we study the organometal lead halides (OLH) based perovskite solar cells (PSC). In fact, we investigate and discuss the electronic properties of the novel solar perovskites CsMBr3 (M = Pb or Ge) materials, using the DFT method combined with the Quantum Espresso package. Moreover, the effect of the lattice parameter and the number of layers on the band gap value of the solar perovskites photovoltaic CsMBr3 (M = Pb or Ge) have been improved. Indeed, we inspect the structural properties of the studied materials and found that the optimized lattice parameter is equal to 6.0 Å for the solar perovskite material CsPbBr3. While, for the solar material CsGeBr3, the optimized lattice parameter value is 5.7 Å. In addition, it is found that the band gap value increases for increasing the lattice parameter values for the two materials. On the other hand, when increasing the number of layers of the solar perovskites CsMBr3 (M = Pb or Ge), the total energy decreases. Furthermore, the band gap crosses through a maximum before decreasing more and more for sufficiently large number of layers.