Cu_2ZnSnS_4(CZTS)/ZnS heteroj unctions have been prepared by a successive deposition of ZnS and CZTS thin films by ultrasonic spray pyrolysis technique on glass substrates.The cupric chloride concentration has been varied in the starting solution in order to investigate its influence on device properties.CZTS/ZnS heterojunctions were characterized by recording their current-voltage characteristics at different temperatures.The obtained results exhibit a good rectifying behavior of the realized heterojunction.Analysis of these results yields saturation current,series resistance and ideality factor determination.From the activation energy of saturation current we inferred that the thermal emission through the barrier height is the dominant mechanism of the reverse current rather than the defects contribution. Cu2ZnSnS_4 (CZTS) / ZnS heteroj unctions have been prepared by a successive deposition of ZnS and CZTS thin films by ultrasonic spray pyrolysis technique on glass substrates. The cupric chloride concentration has been varied in the starting solution in order to investigate its influence on device properties .CZTS / ZnS heterojunctions were characterized by recording their current-voltage characteristics at different temperatures. The resulting results exhibit a good rectifying behavior of the realized heterojunction. Analysis of these results yields saturation current, series resistance and ideality factor determination. Flash the activation energy of saturation current we inferred that the thermal emission through the barrier height is the dominant mechanism of the reverse current rather than the defects contribution.