Using UV/VIS/NIR absorption spectra establish CdS thin film process real-time automatic monitoring and control system of CIGS thin-film solar cell

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Thickness of the cadmium sulfide (CdS) thin films is relation with the photoelectric conversion efficiency of CIGS thin-film solar cell. The reactant’s concentration, reaction solution’s temperature and the pH value is influence CdS thin films grown, resulting in process stability is not high and product yield is major changes. In this study, according to UV/VIS/NIR absorption spectra of theory, analyze the concentration of each substance use by every five minutes and three hours of continuous scanning spectral information, due to the absorption peak of thiourea, ammonia and cadmium acetate will overlap each other, resulting in the absorption will be increase in absorbance wavelength, concentration of various substances, who can’t directly to analysis by the coefficient. Therefore, in this study to establish program solver concentration of each substance estimation model through the absorption wavelength, include to the main absorption wavelength, three wavelengths who is in front of the main absorption wavelength and three wavelengths who is after the main absorption wavelength at the substance overlapping bands by using program solver method. But in the process of CdS formation reaction, ammonia have the characteristics of volatile, in the course of the reaction, the concentration of ammonia is changes by the characteristics of volatile and the consumed of reaction, therefore, estimate the ammonia concentration by using program solver have to deducted consumption of volatilization, and cadmium sulfide generation will cause the absorption be increase in each material’s absorbance wavelength, therefore, bring in CdS to program solver variables. However, the total generate cadmium sulfide of the model’s estimation still have the error with the actual amount of cadmium sulfide, but compared to the real plant processes use to the massive of the solution, the estimation model use to the real plant certain feasibility, in the manufacturing process of the real plant, the cadmium sulfide who on the glass wall of the beaker is regard to the amount of cadmium sulfide as real process plant on a substrate, then the fixed board size that can be learned on the thickness of CdS films adsorbed on the substrate and improve efficiency of the process products. Filtering the resulting amount of cadmium sulfide is regard to residual amount after the end of the reaction, it can determine whether to continue the process or be added to the reaction so that the reactants CdS formation reaction continues to improve the efficiency of the use of process reduce the loss of raw materials.