Fig. 2

Defect formation energies for tetragonal MAPbI₃a under halide rich and b under halide poor conditions. Reproduced with permission [30]. Copyright 2015, American Chemical Society. c Schematic diagram of energy levels and electron transfer processes in a spiro-MeOTAD/perovskite/TiO₂ cell. Reproduced with permission [38]. Copyright 2014, Springer Nature. d Schematic diagram of the hot-hole cooling, charge recombination in MAPbI₃, and charge separation at interfaces. Reproduced with permission [37]. Copyright 2013, American Association for the Advancement of Science