Preparation of CsPbBr3 Films with Tens of Micrometer-Scale Grains and Preferential Orientation for Perovskite Solar Cells

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High quality perovskite films with large grains, a preferential orientation, and a low defect density are desired for efficient perovskite solar cells. Here, we fabricate all-inorganic CsPbBr 3 perovskite films from thermal vapor deposition followed by upside-down high temperature annealing. After high temperature annealing, the perovskite films with randomly oriented nanocrystals convert to continuous films with large columnar grains, (001) preferential crystal orientation, and no evident change in thickness. The average grain size reaches ∼7 μm after annealing at 375 °C for 30 min, which is almost 50 times larger than that of the primitive sample. Some large columnar grains in tens of micrometers are frequently observed under an optical microscope. The photoluminescence intensity is about 2 orders of magnitude stronger than that before annealing, showing a high-quality film with a low defect density and low nonradiative recombination. The perovskite solar cells based on the large grain films exhibit a high power conversion efficiency of 7.96%.