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

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 center dot PbI2 precursor film, which can be easily thermally decomposed back into PbI2. This novel intermediate planar HCl center dot PbI2 precursor film can be completely converted into a compact planar MAPbI(3) 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 MAPbI(3) 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.