The Preparation Of CdS And Cd_xZn_1-xS Buffer Layer For Thin Film Solar Cells

The thin film solar cells as a new kind of energy have got a rapid development. The series of CIS (CuInSe2, CuInS2 and so on) thin film solar cells have attracted more and more attention for their high transmission efficiency, relative low cost. The CdS thin films in CIS solar cells, the quality of thin films deposited will limit the efficiency of solar cells. This paper aims to prepare CdS and CdxZn1-xS buffer layer thin films by chemical bath deposition on common glass substrate, and we studied parameters to the impact of law on the film.CdS thin film was prepared by CBD using CdSO4 as source of Cd and SC(NH2)2 as source of S. Attempts are made to use ammonia as complexing agent and (NH4)2SO4 as buffering agent. Attempt is also made to form the thin film in alkaline solution. This part makes a discuss about the effects of solution deposition time and deposition temperature and reactant concentration (SC(NH2)2 concentration) on the macro-morphology, thickness, transmission, morphology and component of the thin film. Smooth CdS thin films have been successfully prepared under strictly controlled conditions in which the total volume of solution is 100ml, the reaction temperature is 80℃, the deposition time is 20 minutes, the molar ratio of CdSO4,SC(NH2)2and (NH4)2SO4 in the solution is kept as 1:2.5:2.5 and pH is 11～12. Then the thin film is annealed at 400℃in airtight silica tube with N2. The smoothness and compactness of the thin films are fine. The thin films are continuous and homogeneous, and its Cd/S atomic ratio is close to stoichiometric proportion 1:1. CdS thin films annealed have pure cubic structure and the band gap of CdS is as high as 2.367eV.CdxZn1-xS thin film was prepared by CBD using CdSO4 as source of Cd, ZnSO4 as source of Zn and SC(NH2)2 as source of S. Attempts are made to use ammonia and C6H5Na3O7·2H2O as complexing agent. Attempt is also made to form the thin film in alkaline solution. It was prepared for CdxZn1-xS films by chemical bath deposition. This part makes a discuss about the effect of different Concentration ratio of reactants (Concentration ratio of CdSO4 and ZnSO4) on the macro-morphology, transmission, and component of the thin film. Smooth CdxZn1-xS thin films have been successfully prepared under strictly controlled conditions in which the total volume of solution is 100ml, the reaction temperature is 80℃, the deposition time is 90 minutes, and then the thin film is annealed at 400℃in airtight silica tube with N2. Eventually, the smoothness, compactness and good transmittance of CdxZn1-xS thin films were obtained.