Fig. 3: Two-step solution method fabrication and optimization.
From: Recent progress in the development of high-efficiency inverted perovskite solar cells

a Schematic illustration of the interdiffusion in the spin-stacking of double layers of PbI2 and MAI and solvent annealing process. Reproduced with permission from Ref. 65. Copyright 2014, Wiley-VCH. b SEM images of PbI2 films fabricated from PbI2/DMF solutions with different H2O contents. Reproduced with permission from Ref. 67. Copyright 2015, Royal Society of Chemistry.