Thermal annealing plays multiple roles in fabricating high quality perovskite films. Generally, it might result in large perovskite grains by elevating annealing temperature, but might also lead to decomposition of perovskite. Here, we study the effects of annealing temperature on the coarsening of perovskite grains in a temperature range from 100 to 250 degrees C, and find that the coarsening rate of the perovskite grain increase significantly with the annealing temperature. Compared with the perovskite films annealed at 100 degrees C, high quality perovskite films with large columnar grains are obtained by annealing perovskite precursor films at 250 degrees C for only 10 s. As a result, the power conversion efficiency of best solar cell increased from 12.35% to 16.35% due to its low recombination rate and high efficient charge transportation in solar cells. (C) 2018 Elsevier Inc. All rights reserved.