Additionof Monovalent Silver Cations to CH 3 NH 3 PbBr 3 Produces Crystallographically Oriented Perovskite Thin Films

The incorporation of monovalent silver (Ag+) cations into methylammonium lead bromide (CH3NH3PbBr3) perovskite films leads to 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. Composition 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. The light-emitting properties of the films, however, are largely unaffected by Ag+ doping.