Fabrication And Properties Of Cu₂ZnSnS₄Solar Energy Materials And Solar Cells

The hunt for inexpensive thin films for solar cells is also a hot topic of current research in recent years. Solar cells based on Cu2ZnSnS4(CZTS) thin film offer such a celebrated alternative to Cu(In,Ga)Se2(CIGS) solar cells due to the abundance, environmental benignity and industrial compatibility of its constituent elements. As a result, CZTS materials have attracted increasing attention and remarkable progresses have been made over the past few years by lots of groups using different fabrication approaches. This work is focused on the fabrication and properties of CZTS and Cu2ZnSn(S,Se)4(CZTSSe) thin films and solar cells via a low-cost, non-toxic sol-gel technique. The innovative results are displayed as follows:1. Non-toxic organics ethylene glycol was selected as solvent. CZTS thin films were prepared from organic salts by a sol-gel technique without sulfurization. The CZTS thin films showed a smooth, compact and crack-free morphology. All the CZTS films were of S-deficient state. However, the percentage of metals and S content in CZTS films can be adjusted by the preparation of solution, the pre-annealing treatment and the post-annealing condition, respectively.Ethylene glycol and organic salts were used as solvent and raw materials to fabricate CZTS precursor solution. The CZTS precursor solution was spin-coated onto substrate and then annealed to prepare CZTS thin films. Sulfurization was not used on the annealing process. Effects of preparation conditions on CZTS thin films were researched and the optimum condition were confirmed.2. The CZTS thin film solar cells were successfully fabricated via a sol-gel method with sulfurization process and the best conversion efficiency was4.28%. The CZTS thin film solar cell was also prepared by a sol-gel technique without sulfurization process and the conversion efficiency was2.1%.The CZTS thin films were prepared by a sol-gel technique with sulfurization, and the fabrication conditions of the other layers were optimized. The synthesized condition for CZTS cells with best conversion efficiency was obtained thorugh the photovoltaic tests on them. The optimized preparation process of CdS was achieved by studying the influence of buffer layer CdS on the performance of CZTS cells.3. CZTSSe thin films with a compact and crack-free morphology and lager-grain were obtained via a green sol-gel process and post-selenization. A CZTSSe thin film solar cell was prepared and the conversion efficiency was2.92%.CZTSSe thin films with a compact and crack-free morphology and lager-grain were obtained via a green sol-gel process and post-selenization. The fabrication of CZTSSe films was simplified by avoiding using sulfurization. Optical band gap of the CZTSSe thin films decreased from1.51to1.14eV with increasing Se content. The preparation conditions of CZTSSe solar cells were severe. A CZTSSe thin film solar cell with the conversion efficiency of2.92%was fabricated.