Comparative study of the role of Ga in CIGS solar cells with different thickness

Publication date: 1 January 2016
Source:Thin Solid Films, Volume 598
Author(s): Anjun Han, Yun Sun, Yi Zhang, Xiaohui Liu, Fanying Meng, Zhengxin Liu
Cu(In, Ga)Se2 (CIGS) thin films with thickness of 1μm and 2μm are prepared by co-evaporation process, and the different Ga/(Ga+In) are achieved by varying the temperature of Ga source. The morphology, structure, minimum band gap, and performance of solar cells are comparatively studied. As Ga/(Ga+In) increases, little changes can be observed in the crystal quality of 1μm CIGS films, while the grain size of 2μm films decreases significantly. (112) diffraction peak intensities of the 1μm and 2μm films decrease and increase, respectively. In the case of the same Ga/(Ga+In), the minimum band gap values of 1μm films are larger than that of 2μm films, and the difference becomes large with Ga/(Ga+In) increasing. The minimum band gap values of 1μm films are more sensitive to variation of the Ga/(Ga+In). As Ga/(Ga+In) increases, a more improvement of the efficiency of solar cells with thickness of 1μm is obtained due to the large enhancement of the open-circuit voltage, and the efficiency reaches the maximum value when Ga/(Ga+In) is about 0.37.