Method for preparing three-band-gap tin-doped copper-gallium-sulfur solar cell thin film material through sulfuration annealing after double-potential deposition

The invention discloses a method for preparing a three-band-gap tin-doped copper-gallium-sulfur solar cell thin film material through sulfuration annealing after double-potential deposition. The method comprises the following steps that 1, copper chloride, gallium chloride and stannic chloride are dissolved in deionized water in sequence and are subjected to electro-deposition through a three-electrode system, and a precursor thin film is obtained in the deposition process through double-potential deposition; and 2, a CuSn thin film is deposited through a high potential at first to effectively avoid hydrogen evolution and then is deposited through a low potential, for an induced deposition mechanism of Ga, the deposition efficiency of the Ga is beneficially improved through an overpotential formed by electrode potential abrupt change and the CuSn thin film deposited under a high pulse, and then the precursor thin film is subjected to sulfuration annealing after being cleaned and dried, so that a tin-doped cop