Self-assembled Preparation Of Multilayer Film In CZTS Solar Cells

Copper indium gallium selenide (CIGS) thin-film solar cells has been the most popular fieldof solar cells in recent years with a great breakthrough,and the highest conversion efficiencies hasexceeded20%. However, the further development of CIGS thin-film solar cells is restricted as Gaand In are rare element and Se is toxic.Cu2ZnSnS4,element of which is abundant and non-toxic,hasa similar structure with CIGS.It is considered as one of the most promising alternative to take theplace of CIGS material.This work used the hot-injection method to fabricate Cu2ZnSnS4,and then prepare thenanoparticles thin films via drop casting.X-ray Diffraction, Raman Scattering Spectra and theEnergy Dispersive X-ray Spectroscopy were used to test the element composition and the crystalstructure.The surface morphology and optical properties of the samples were characterized by theScanning Electron Microscope and the UV-VIS Spectrophotometer.The experimental parameters’influence on the structure optical absorption coefficient,the surface morphology and the elementcomposition were studied. Then ZnS were prepared via the hot-injection method as well,andsimple CZTS solar cells were assembled. Results show that:1.The samples synthesized under260°C are the purest cubic CZTS nanocrystals. By theinduction to the process of nucleation and aging of the CZTS nanopartitles via the seed solutionmethod,the uniformity of CZTS nanoparticles and the smoothness of the film surface are improvedeffectively.2. Comparing to isopropanol and cyclohexane that are less toxic,toluene has better dispersioneffect as CZTS dispersing agent.Though the dispersion can be promoted by ultrasonic concussion,but the dispersion effect or thin film surface smoothness will not increase with the increase ofshock time all the time.3. Vacuum drying and heat treatment can enhance the orderliness of CZTS nanoparticles,surface smoothness and compactness of the film, and the optical properties of thin films as well.4. There is some loss of Zn and S during the experiment,so we add excess Zn and S to studythe the effect of different properties of the reaction ratio on the obtained film material consideringthe loss ratio in advance. The results showed that a slight excess of Zn and S will help improve theoptical properties of the film. 5. ZnS was prepared with hot-injection method, and a simple CZTS thin-film solar cells wasassembled.However, due to the contact between different layers which was not close enough andthe remaining of the dispersan, the conversion efficiency of the resultant solar cell is as low asonly0.1%.At the end of the thesis,the study work is is summarized, and some shortcomings and furtherimprovements are pointed out.