Analysis and improvement of CIGS solar cell efficiency using multiple absorber substances simultaneously

In this paper, the efficiency of a CIGS solar cell was increased in several stages. The common structure and configuration of the CIGS solar cell are the ZnO:Al/ZnO/CdS/CIGS/MO combination whose efficiency is optimized approximately 20% for CIGS with thickness of 2 µm and 17% for CIGS with thickness of 1 µm. In this article, thickness of CIGS is 1 µm and the efficiency of this type of solar cell was calculated using Atlas software of Silvaco. In the first step, by applying Zn_1−xMg_xO material with x = 0.17 instead of ZnO material, the cell efficiency was 20.7% and then by adding GaAs as the electron reflector layer, we were able to achieve 27.1% efficiency and at the end, to increase the efficiency, one absorber layer is added under the CIGS absorber. This absorber layer is CIS (CIS is CuInSe₂) that made the efficiency to become 27.9%. Indeed, CIGS absorber layer is not able to absorb all photons of the sun. So, this added absorber layer is able to absorb a part of low-energy photons, which lead to increasing the efficiency of the solar cell. It should be noted that in the whole process of this article, CIGS and CIS absorber layers are p-type.