The thermal stability of the perovskite CH_3NH_3PbI_3 films fabricated by using the one-step spin-coating method was intensively studied by XRD and SEM analysis. The mechanism for the formation of the CH_3NH_3PbI_3 film in the one-step spin-coating processing was also proposed based on the obtained experimental results. The appropriate pre-annealing temperature for the fabrication of CH_3NH_3PbI_3 film and the critical thermal decomposition temperature of the CH_3NH_3PbI_3 film remained 100 ℃ and 140 ℃.The ...