PhaseStability and Electronic Structure of the Halide Perovskites ABX3

Perovskites are very interesting for applications such as optoelectronic devices emitting light and such as OLEDs, and lasers. On the other hand, one can consider using these perovskites in a very special architecture: the tandem cells to optimize the absorption of the solar spectrum and thus increase the efficiency of the cells: the perovskites could make it possible to increase the collection of the UV part of the solar spectrum. Many perovskite crystals (ABX3) have been discovered to present second order properties for NLO, they undergo phase transitions in which they transform into slightly disordered structures of the original crystals. In this book, we explore three Perovskite crystals CsSnBr3, RbSnBr3 and CsGeBr3, they undergo three successive different phase transitions. These phase transitions influence the structural properties and consequently the electronic and optical properties of this material. The calculation of the electronic properties shows the semi-conductor character of this material that plays a key role in evaluating the use and yield of the materials in solar cells.