A system for fabricating a perovskite film, wherein source materials include: an organic halide compound AX having A combined with X; and a metal halide compound BX 2 having B combined with X 2, wherein the A represents an organic element selected from a group consisting of methylammonium and formamidinium, the B represents a metal element selected from a group consisting of Pb and Sn, and the X represents a halogen element selected from a group consisting of Cl, I and Br, wherein halogen X in the AX and halogen X in the BX 2 are the same or different, the system comprising: a housing for use as a furnace, the housing having a closed hollow structure elongated longitudinally, the housing comprising: an inlet portion and an outlet portion for inputting and outputting gases, respectively, the inlet portion configured to be adjusted for inputting an inert gas into the housing; a first section for use for loading an evaporation unit containing the AX for generating an AX gas, the first section corresponding substantially to an upstream section of the inert gas; and a second section for use for loading one or more substrates, each of which is pre-deposited with the BX 2, the second section corresponding substantially to a downstream section of the inert gas; a first temperature control unit coupled to the first section of the housing for controlling a first temperature for the AX; and a second temperature control unit coupled to the second section of the housing for controlling a second temperature for the one or more substrates pre-deposited with the BX 2, wherein the first temperature control unit is configured to: heat the AX for evaporating the AX to generate the AX gas for a predetermined duration of time, and turn off the heating to allow desorption of the AX from the perovskite film oversaturated with the AX, thereby promoting a reversing process of turning the perovskite film over-saturated with the AX to the perovskite film saturated with a right amount of AX. a housing for use as a furnace, the housing having a closed hollow structure elongated longitudinally, the housing comprising: an inlet portion and an outlet portion for inputting and outputting gases, respectively, the inlet portion configured to be adjusted for inputting an inert gas into the housing; a first section for use for loading an evaporation unit containing the AX for generating an AX gas, the first section corresponding substantially to an upstream section of the inert gas; and a second section for use for loading one or more substrates, each of which is pre-deposited with the BX 2, the second section corresponding substantially to a downstream section of the inert gas; an inlet portion and an outlet portion for inputting and outputting gases, respectively, the inlet portion configured to be adjusted for inputting an inert gas into the housing; a first section for use for loading an evaporation unit containing the AX for generating an AX gas, the first section corresponding substantially to an upstream section of the inert gas; and a second section for use for loading one or more substrates, each of which is pre-deposited with the BX 2, the second section corresponding substantially to a downstream section of the inert gas; a first temperature control unit coupled to the first section of the housing for controlling a first temperature for the AX; and a second temperature control unit coupled to the second section of the housing for controlling a second temperature for the one or more substrates pre-deposited with the BX 2, wherein the first temperature control unit is configured to: heat the AX for evaporating the AX to generate the AX gas for a predetermined duration of time, and turn off the heating to allow desorption of the AX from the perovskite film oversaturated with the AX, thereby promoting a reversing process of turning the perovskite film over-saturated with the AX to the perovskite film saturated with a right amount of AX. heat the AX for evaporating the AX to generate the AX gas for a predetermined duration of time, and turn off the heating to allow desorption of the AX from the perovskite film oversaturated with the AX, thereby promoting a reversing process of turning the perovskite film over-saturated with the AX to the perovskite film saturated with a right amount of AX.