The preparation of uniform, high-crystallinity planar perovskite films with high-aspect-ratio grains over a square-inch area is demonstrated. The best power conversion efficiency (PCE) of 16.3% (stabilized output of approximate to 15.6%) is obtained for a planar perovskite solar cell (PSC) with 1.2 cm(2) active area, and the PCE jumps to 18.3% ( stabilized output of approximate to 17.5%) for a PSC with a 0.12 cm(2) active area.