Synthesis Of Cds Nanocrystal By Thermal Solvent Method And Thin Film Preparation

Solar cell, as one of the new energy resources, has been developed for a long time. Thin film solar cell become a focus point because of its advantages, such as low cost, simple process and cheap raw material and so on. At present, CdTe and CuInSe2 thin film solar cells have been produced in market and applied well. CdTe/CdS thin film solar cell has a good prospect in thin film solar cells.CdS as an important kind ofⅡ-Ⅵsemiconductor materials has been studied by many people, and CdS material has been applied in optical, electrical and magnetic fileds through the research on preparation methods, morphology and performance of CdS. In this paper, CdS crystals were prepared by thermal solvent method at atmospheric pressure, and XRD,SEM, EDS, HRTEM, FT-IR and UV-Vis were used to characterize the properties of CdS nanocrystals.Influence of sulfur sources, solvents, injection order and temperatures as well as whether or not use complexing agent on crystal structures, morphology, composition and dispersion of CdS nanocrystals were observed. Surfactants were used to improve properties of CdS nanocrystals. The results showed that injection order of sulfur source and temperature have impact on crystal type of CdS nanocrystals, and the different sulfur sources have impact on crystallization of the products. When using cadmium nitrate and TAA as precursors and cadmium nitrate was injected to TAA based EG (ethylene glycol) solution at the temperatures from 120℃to 190℃, Zinc Blende CdS was abtained.When sulfur sources injected to cadmium nitrate at 210℃based EG-glycerol, mixed phase CdS was abtained when sulfur source was TAA, wurtzite CdS was abtained when sulfur source was thiourea. When using cadmium nitrate and thiourea as precursors and thiourea was injected to cadmium nitrate based EG solution at 190℃for 0.5 h, wurtzite CdS nanocrystals with Cd/S ratio about 1:1 was obtained, and the CdS particle size from solution with TEA complex was smaller than that one from solution without TEA complex. Both could be dispersed well in ethanol and formed stable colloid solution when using PVP as dispersant. After films were annealed at 450℃, the particle size of thin films increased a little. UV-Vis spectra showed that the films have strong absorption in the range from 350 nm to 530 nm, and considerable transmission in the range from 530 nm to 800 nm, which is suitable for the window layer of solar cells. By calculated from UV-Vis spectra, the optical band gap of the film with complex was 2.31 eV and 2.34 eV for 15 times and 50 times of dip-drawing, respectively. And optical band gap of the film without complex was 2.35 eV for 40 times of dip-drawing.