Preparation By Single-target Sputtering And Studies Of The Heat Treatment Process Of CIGS Thin-film

Cu(In1-xGax)Se2(CIGS) is a direct band gap p-type semiconductor with chalcopyritestructure.Band gap of CIGS can be adjusted by doping Ga varying betweenl.04 ～1.67 eV to match the solar light spectrum. The light absorption coefficient reaches as high as 105 cm-1, makes it suitable for fabricating thin film solar cells. This paper focused on the follow aspects as preparation and study of CIGS photovoltaic target, single target sputtering and selenization of CIGS film, and investigated their relative merits.We have prepared CIGS target by hot pressing process and deposited CIGS film by magnetron sputtering. The influence of Sintering temperature on the relative density of target, the sputtering temperature and solid Se source annealing process on the electrical and optical properties of CIGS film has been studied.(1)A kind of target which can meet the requirement of sputtering is made with over 92% relative density by exploring the sintering process of CIGS target.And the relative density can reach up to 98.85% at 630 ℃.What can be obtained is that optimum sintering temperature ranges from 620℃ to 650℃ with work pressure—45 Mp, particle size—75 um, sintering time —3 h.(2) CIGS thin film is deposited by sputtering CIGS targets with different deposition temperatures. It is found that the CIGS thin film nearly has the same components with the sputtering target at the same sintering temperature. CIGS thin film has the stronger (220) preferred orientation at lower temperature with the increasing sintering temperature which shows that sintering temperature has little influence on the component of films. Morphology of CIGS thin film is related to sintering temperature closely, probably due to the change of growth behavior of grain.(3)After annealing in the solid Se source at 530℃, sheet resistance of the CIGS thin film becomes larger. The crystallinity and morphology is improved and the percentage of Se atomic in the CIGS thin film increases, improving Defects and recombination centers of films before annealing. In the process of annealing, Se atoms firstly react with the surface of thin film and spread to the inner part of thin film to react with inner part while Ga atoms are spreading from the surface of thin film to the inner part.The photoelectric properties of the CIGS film improves obviously when compared with that before annealing, and I-T curve of sickle-shaped wave changes into a square wave sickle-shaped wave approximately...