Augmenting CIGS Solar Cell Efficiency Through Multiple Grading Profile Analysis

Thin film solar cells are leading the charge toward a greener future, offering a renewable energy source that can be scaled up to meet the rising demand for clean energy. Copper-indium-gallium-selenium (CIGS) is a promising material for solar cells due to its excellent absorption coefficient, affordability, and non-toxic nature. As per the literature, CdS is the most commonly used buffer layer for CIGS solar cells, which is toxic. Therefore, in this article, a CIGS-based solar cell is proposed using In 2 S 3 as a buffer layer. The efficiency achieved by this In 2 S 3 -based CIGS solar cell is 17.7%. To further enhance the efficiency, this work utilizes the most exciting property of CIGS—their tuneable bandgap. A bandgap that can be adjusted is known as a tuneable bandgap, which can be achieved by altering the composition of the CIGS material. In this context, the bandgap of CIGS is modified by gradually changing the semiconductor’s composition throughout its thickness. Thus, in this work, linear grading, parabolic grading and beta-grading profiles are used to obtain the optimum composition for the CIGS layer. Grading of CIGS helps to reduce transmission and thermalization losses by optimizing the cell’s ability to absorb a wide range of wavelengths of light and by tailoring the energy bandgap of the material. Another critical factor for obtaining the highest efficiency is the thickness of the absorber layer. Therefore, the thickness of the CIGS layer was also varied along with the grading profiles. The results show that maximum efficiency of 25.2% can be achieved using beta grading. Additionally, the results show that the optimum CIGS layer thickness is 1 µm for CIGS-based solar cells.