Fig. 4

Schematic illustration of perovskite (x = 2.5) crystallization on different substrates. a, b The as deposited perovskite precursor complexes on ZnO/PEIE (a) and on TiO_x/PEIE or SnO₂/PEIE (b) substrates. c–e The thermal annealed perovskite films on ZnO/PEIE (c), SnO₂/PEIE (d) and TiO_x/PEIE (e) substrates, respectively