| Power generation through photovoltaic(PV) has been growing at an average rate of 40% per year over the last decade.Cu2 Zn Sn S4;commonly abbreviated as CZTS is a promising material for low cost thin film solar cells. The phase stability area of CZTS thin film is narrow, and it is occur a large number of internal defects at non-stoichiometric ratio. The appropriate atomic ratio and internal defects of CZTS thin film can be used to achieve the highest photoelectric conversion efficiency. The pulsed laser deposition(PLD) is a versatile deposition method. It is a simple, but multipurpose, experimental method that finds use as a means of modeling a very diverse range of materials, and in extensive areas of thin film deposition and multi-layer research. This technique is suitable for depositing high quality films. Therefore, the thesis structure is divided into three main parts, as follows:The first part compared the ordinary ratio of target and the rich-sulfur target. The study found: 1) use the rich-sulfur target cannot inhibit the loss of the ingredients in the process of pulsed laser deposition process. The small grain in the as-deposited sample had been formation and growth because of the higher energy of plasma and the sulfur-rich environment. When annealing at the vacuum, the growth of the small grain from sulfur-rich targets had been promoted, it is bigger than that from the ordinary proportion target. However, the preparation CZTS film of sulfur-rich and copper-rich targets cannot become the absorber layer of the efficient CZTS thin film solar cell because of poor sulfur ratio. 2)The near-infrared transmittance of the as-deposited sample is lowest. Because it had been absorbed by the impurity level. The sample of annealing temperature at 300℃ is insufficient to support the reorganization of the lattice stability, the migration of impurities is resulting some lattice crushing. The proportion of impurities is less than the as-deposited samples. At the higher annealing temperature, the lattice reorganization become easier. The crystalline quality of the sample annealed at 400 ℃ is best. With increasing in the annealing temperature, the composition of CZTS film is restructuring and separation again. The CZTS film by pulsed laser deposition using sulfur-rich target supplemented situ vacuum and annealing temperature of 400 ℃ is better.The second part compared the influence on the structure and properties of the CZTS thin films which annealing in the atmosphere of nitrogen and hydrogen sulfide. The study found that annealing in the nitrogen atmosphere cannot achieve the sulfur-rich sulfur ratio, but it is contribute to the suppression components loss, it is good for curing sulfur element. The preparation method of CZTS film is failure, which used the CZT alloy prefabricated layer annealing in the hydrogen sulfide. But this proved that the thin film annealing in the hydrogen sulfide atmosphere can provide a stable source of sulfur. The CZTS film had got in the sample annealing in the hydrogen sulfide, which crystalline quality is better. Its composition ratio, crystalline quality, optical band gap and the film thickness had reached the requirements of the CZTS thin film solar cells which is efficient.The last part is the preparation for the CZTS thin film solar cells. A layer of Mo as a metal to be a collector electrode is produced by pulsed laser deposition. Cd S thin film by chemical bath deposition method is a buffer layer. Zn O and Al: Zn O films made by RF and DC sputtering. The study found that there are a small amount of Mo2S3 and Cu2 S impurities in the CZTS film solar cells. The absorbing layer fully which fully populated by sulfur and high crystalline quality is polycrystalline morphology. The Mo film and the Al: Zn O film are columnar grain. The sample annealing at 450 ℃ found the current density(JSC) = 10.41 m A/cm2,a fill factor of 0.747,and open circuit voltage(VOC) = 597 m V,,with a power conversion efficiency of 4.65%. |
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