Addition of Monovalent Silver Cations to CH3NH3PbBr3 Produces Crystallographically Oriented Perovskite Thin Films

The incorporation of monovalent silver (Ag+) cations into methylammonium lead bromide (CH3NH3PbBr3) perovskite films leads to a strongly preferred (001) crystallographic orientation on a wide variety of substrates, ranging from glass to mesoporous TiO2. CH3NH3PbBr3 films deposited without Ag+ exhibit only a weakly preferred (011) orientation. Compositional maps and depth profiles from time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveal Ag+ segregated to grain boundaries and interfaces. In photovoltaic devices (PVs), addition of Ag+ to MAPBr films resulted in poorer device performance, most likely because of the observed Ag+ segregation in the films.