Fabrication And Optimization Of CuIn?S,Se?₂ Thin Film Solar Cells Based On DMF Precursor Solution

Copper indium gallium selenide?Cu?In,Ga?Se₂,CIGS?as thin film solar cell absorber materials have many advantages,such as high absorption coefficient,good stability and tunable band gap.However,the CIGS absorber materials of the commercialized CIGS solar cell are all fabricated by vacuum based methods which require expensive equipment and complicated manufacturing process.Precursor solution method is one of the most promising approaches to fabricate CIGS absorber materials because of its simple processing,high utilization rate of materials and adaptable to large area substrate.The key to fabricate CIGS thin film solar cell from solution is the selection of solvent.The best solution processed CIGS solar cell with a power conversion of 17.3%is fabricated from hydrazine based ink.However,it is almost impossible to manufacture CIGS solar cell from hydrazine because of its explosive,high toxic and carcinogenic.Although many other solvents have been used to prepare CIGS precursor solutions,the results are not as good as hydrazine.For example,the solvent can't completely dissolve all precursor compounds and solution is not stable for a long time storage.Two environmentally benign solvents,N,N-dimethylformamide?DMF?or 1-methyl-2-pyrrolidone?NMP?have been successfully used as solvent,metal halides and thiourea as the precursor compounds,to prepare CIS/CIGS precursor solutions and fabricate CIS/CIGS absorber thin film materials.The effect from mole ratios of precursor copper/indium and thiourea/metal on the composition on CIS thin film,especially indium loss,has been systematically studied and the ratio of the feeding precursors has been optimized.The CIS solar cell device with an efficiency of 7.88%has been achieved.The influence of the selenization argon pressure on the CIS material property has been studied and the mechanism of CuInSe₂ grain growth has been suggested,based on which selenization condition is further optimized by using controlled pressure selenization.In this thesis,for the first time,DMF or NMP have been respectively used as solvent to prepare CIS/CIGS precursor solutions,and 7.88%CIS solar cell has been fabricated from the DMF precursor solution.The work of this thesis not only expands the solvent pool for CIS/CIGS precursor solution,also provides a new strategy for further improve CIS/CIGS absorber materials properties.