Recently, fully covered and smooth perovskite films could be fabricated by optimized coating methods; however, it is still hard to prepare perovskite films with large grain sizes and high crystallinity. Given the fact that thermal energy can promote crystallization, we combine high-temperature crystallization with the application of a solvent featuring a high boiling point, in order to produce high quality perovskite films with micrometer-sized grains. We further investigated the temperature dependence of the thermally induced synthetic strategy, whereby the grains become larger as the temperature is elevated. After solar cell device fabrication, the efficiency of the best cell can attain a high value of 15.53 % with reduced hysteresis behavior.