CIGS Films Prepared By One-step Pulsed DC Magnetron Sputtering

Cu(In,Ga)Se2(CIGS) thin-film solar cells attracts growing attention. with high efficiency, low cost, anti-radiation and other excellent features. Magnetron sputtering is a widely used method for the preparation of CIGS thin film. Therefore, we use a single target DC pulse magnetron sputtering to prepare CIGS thin film, and investigate of the deposition process parameters on the performance of CIGS thin-film systematically. During the preparation of CIGS thin film, We studied the effect of the power supply parameters, such as sputtering power, frequency, and substrate temperature on the phase structure of the film, preferred orientation status, composition, electrical properties and so on.In addition, the deposition rate(corresponding to sputtering current) is the key factor of affecting the preferred orientation of the films in the present work, i.e., the preferred orientation changed from(112) to(220)/(204) with increasing deposition rate, where the critical deposition rate is about 22.5 nm/min. Even without heating the substrate, the contents of elements in all the deposited CIGS film remarkably deviated from that in the employed CIGS target, and the crystal structure of all the deposited films belongs to chalcopyrite structure. With increasing the sputtering current, the contents of Se and Ga elements were almost constant, the content of In element increased, but the content of Cu element decreased; With decreasing sputtering voltage, the contents of Se and Ga elements increase, but the content of In element decreases.Subsequently, the sputtering yields of the elements simulated by a semiempirical formula indicate the intrinsic properties(such as surface binding energy, atomic number, and atomic mass) of the elements are important parameters directly influencing the composition of the deposited films. The research on the electrical properties shows that the Cu-poor CIGS generally has lower carrier concentration and accordingly has higher resistivity.In the process of magnetron sputtering CIGS thin film, CIGS crystallization state is also important. In this paper we design a novel method of heating substrate, and study the effects of different substrate temperature on the performance of CIGS films. According to the results, the phase structure of the sample is single chalcopyrite structure when the substrate temperature does not exceed 400 oC. Especially when the substrate temperature is at 400 oC, we obtained a more dense CIGS thin film with larger grains. When the temperature reaches 450 oC, the film has a loose morphology. The study also shows that the film does not change the basic composition when the substrate temperature is in the range from RT to 400 oC. In addition, the preferred orientation of the film is(220)/(204) when the substrate temperature is RT; When the temperature exceed 100 oC, the preferred orientation turns into(112).