Prepare CuIn1-xGaxSe2 thin films by sputtering and electroplating

• Main Authors: Hsiu-Min, Lin, 林修民
• Other Authors: Yih-Ming, Liu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/62287040998242024906

碩士 === 國防大學理工學院 === 材料科學碩士班 === 97 === Two different methods, sputtering and electroplating, were used to prepare CuIn1-xGaxSe2 thin films, which act as the main absorber layer of copper-indium-gallium-diselenide (CIGS) thin film solar cells, in this thesis. The surface morphology, constituents composition, crystallinity, and electrical properties of these CIGS thin films were analyzed. For the sputtering process, we focus on the preparation of sputtering targets made of the ternary compound alloy, copper-indium-gallium (Cu-In-Ga, CIG). The manufacturing process used vacuum arc melting (VAM) to make the alloy targets with different constituents compositions. The compositions of the targets were analyzed in order to study the relation between the initial ingredients and the final alloy compositions. In addition, these targets were used for sputtering CIG thin films. And by selenizing these CIG precursors, CIGS thin films were fabricated. Finally the composition, microstructure, and electrical properties of CIGS thin films were analyzed. The results revealed that, VAM process could prepare ternary compound alloy target, but the composition is different from original proportion of individual elements. By varying the VAM parameters, one could make alloys with controlled composition and quality. Using these alloys as sputtering targets, CIG precursors were deposited, and after a selenization heat treatment, CIGS thin films containing CuIn0.7Ga0.3Se2 chalcopyrite phase were successfully fabricated. For the electrodeposition process, the research used an equipment for alloy electrodeposition to directly deposit the CIGS thin films on carbon steel and indium-tin-oxide (ITO) glass substrates. We tried to find out the appropriate operating parameters and recipe for plating solution. The results revealed that, with carbon steel, by properly adjusting the electroplating solution, the composition of deposited CIGS thin films was already close to ideal proportion (Cu：In：Ga：Se = 25：17.5：7.5：50). The electrodeposition parameters and constituent compositions of CIGS thin film may change when ITO glass substrates were used instead of carbon steel. The results showed that, for the pH values between 1.5 and 1.7, one could more easily control the composition of deposited films. Also, by varying the composition of electroplating solution, the CIGS thin films already approached ideal composition (Cu：In：Ga：Se = 25：17.5：7.5：50). Finally, a heat treatment in Se vapor could greatly improve the crystalline phase of CIGS thin films.