Air-stable hybrid perovskite solar cell by sequential vapor deposition in a single reactor

Here we demonstrate a facile two-step low-pressure vapor deposition of methyl-ammonium lead iodide (MAPbI3) perovskite films in a single reactor. Continuous, poly-crystalline lead iodide (PbI2) films were deposited in the first step and successfully converted to high quality perovskite films in the second step during exposure of PbI2 films to methyl-ammonium iodide (MAI) vapor. A complete conversion was realized after 90 minutes of exposure with an average grain size of 3.70 ± 1.80 µm. The perovskite conversion starts at the PbI2 surface through the intercalation reaction of PbI2 and MAI vapor molecules and progresses towards the PbI2/substrate interface. The coverage and quality of the perovskite thin film is controlled by that of the pre-deposited PbI2 film. The absorbance measurements confirmed air stability of the fully converted perovskite for 21 days, ascribed to its superior morphology and grain size. Finally, a planar single-junction perovskite solar cell with no additives or additional interfacia...