Figure 3.
Top‐view SEM images of CH3NH3PbI3 thin films prepared from a) standard binary solution of CH3NH3I and PbI2, b) ternary mixture solution of PbI2, CH3NH3I, and NH4Cl without thermal annealing, and c) ternary mixture solution of PbI2, CH3NH3I, and CaCl2 without thermal annealing. Possible mechanisms in the formation of CH3NH3PbI3 film that is spin‐coated from d) ternary mixture solution of PbI2, CH3NH3I, and NH4Cl without thermal annealing and e) ternary mixture solution of PbI2, CH3NH3I, and CaCl2. a,b,d) adapted with permission.65 Copyright 2015, American Chemical Society. c,e) adapted with permission.66 Copyright 2015, Royal Society of Chemistry.