Intercalation crystallization of phase-pure alpha-HC-(NH2)(2)PbI3 upon microstructurally engineered PbI2 thin films for planar perovskite solar cells

The microstructure of the solid-PbI2 precursor thin film plays an important role in the intercalation crystallization of the formamidinium lead triiodide perovskite (alpha-HC(NH2)(2)PbI3). It is shown that microstructurally engineered PbI2 thin films with porosity and low crystallinity are the most favorable for conversion into uniform-coverage, phase-pure alpha-HC(NH2)(2)PbI3 perovskite thin films. Planar perovskite solar cells fabricated using these thin films deliver power conversion efficiency (PCE) up to 13.8%.