Hydrochloric acid accelerated formation of planar CH3NH3PbI3 perovskite with high humidity tolerance

Abstract

We demonstrate high humidity tolerant one-step and sequential deposition methods to fabricate high quality planar CH₃NH₃PbI₃ perovskite films with the assistance of HCl. The addition of stoichiometric HCl into PbI₂ precursor solution from 33 wt% hydrochloric acid leads to the formation of a novel HCl·PbI₂ precursor film, which can be easily thermally decomposed back into PbI₂. This novel intermediate planar HCl·PbI₂ precursor film can be completely converted into a compact planar MAPbI₃ film within only 10 s at room temperature via sequential deposition. In another novel one step method the precursor solution of PbI₂ + MAI + HCl obtained by adding stoichiometric HCl into regular PbI₂ + MAI precursor solution was used to fabricate a very smooth planar MAPbI₃ film by just spin coating. Both the one step and sequential deposition methods can be used to fabricate high quality planar perovskite films in a hood under ambient conditions with up to 60% humidity level for high efficiency planar perovskite solar cells.