Atomic Layer Deposition of Electron Selective SnOx and ZnO Films on Mixed Halide Perovskite: Compatibility and Performance

The compatibility of atomic layer deposition directly onto the mixed halide perovskite formamidinium lead iodide:methylammonium lead bromide (CH(NH2)2, CH3NH3)Pb(I,Br)3 (FAPbI3:MAPbBr3) perovskite films is investigated by exposing the perovskite films to the full or partial atomic layer deposition processes for the electron selective layer candidates ZnO and SnOx. Exposing the samples to the heat, the vacuum, and even the counter reactant of H2O of the atomic layer deposition processes does not appear to alter the perovskite films in terms of crystallinity, but the choice of metal precursor is found to be critical. The Zn precursor Zn(C2H5)2 either by itself or in combination with H2O during the ZnO atomic layer deposition (ALD) process is found to enhance the decomposition of the bulk of the perovskite film into PbI2 without even forming ZnO. In contrast, the Sn precursor Sn(N(CH3)2)4 does not seem to degrade the bulk of the perovskite film, and conformal SnOx films can successfully be grown on top of it...