The comparison of different chemical reaction routes for CBD-ZnS applied on Cu(In, Ga)Se2 solar cells

The most high efficiency cadmium-free CIGS solar cell is zinc sulfide fabricated by chemical bath deposition. However, on account of the presence of Zn(OH)₂ phase during chemical reaction, it leads to poor cell performance attributed in low fill factor and shows distorted I-V curve. The cell performance can be enhanced by continuous illumination, which has been found by many groups called light-soaking effect. In this paper, we compared two different chemical processes with and without ammonia hydroxide etching. The well-known ammonia etching effect for removing Zn(OH)₂ phase has also been observed in this work. By comparing the different chemical processes with ammonia etching, we noticed the difference of compositions due to chemical reaction routes. Based on the research for chemical routes, we further to optimize CBD-ZnS process deposited on CIGS substrates. Owing to the decrease of Zn(OH)₂ concentration by optimized CBD-ZnS, the cell efficiency can be improved in Voc and FF. Moreover, the time for lightsoaking treatment can be shortened to less than 20 minutes.