A 80 μL PbI2 solution was spincoated
on the mesoporous TiO2 films at 4000 rpm for 30 s, followed
by drying at 90 °C for 40 min on a hot plate. After that, the prepared
TiO2/PbI2 film was dipped in a solution CH3NH3I in 2-propanol
(10 mg/mL) for 60 s, rinsed with 2-propanol and followed by baking
at 100 °C for 40 min in air