Fig. 4

A PbI₂ solution is first spin-coated onto the mesoporous TiO₂ film. The PbI₂-coated film is dried at 40 °C for 3 min and 100 °C for 5 min. A MAI solution in 2-propanol is then loaded onto the dried PbI₂ film for 20 s and spun. Finally, the film is heated at 100 °C for 5 min. Reprinted with permission from Ref. [34]