Dynamic Frequency Study Under Monochromatic Illumination of the Photocurrent Density - Photovoltage Characteristic and the Series and Shunt Resistances of a Solar Cell Based on CIGS: Effects of the Angle of Incidence and the Doping Level of Gallium

This article focuses on the analysis of a CIGS (copper, indium, gallium, selenide) solar cell using a dynamic frequency approach under monochromatic illumination. The main objective is to understand the behavior of the cell and identify the factors that influence its performance, particularly the angle of incidence of light and the gallium doping rate. The work begins with solving the differential equation that governs the dynamics of minority charge carriers within the cell. This solution provides an analytical expression for the density of these carriers, which is a crucial step in modeling the electrical behavior of the cell. From this carrier density, expressions for the photocurrent density and photovoltage are then derived. The study of the photocurrent-photovoltage characteristic, often referred to as the I-V (current-voltage) curve, is central to the analysis. This curve reveals two key operating points for the solar cell. The first is short-circuit operation, where the photocurrent reaches its maximum value and remains relatively constant. The second is open-circuit operation, characterized by very low photocurrent values, where the voltage is at its maximum. The results of the study show a correlation between the angle of incidence of light and the performance of the cell. An increase in the angle of incidence leads to a significant decrease in the photocurrent module. This is logical, as a more oblique incidence reduces the amount of light absorbed by the cell. The study also reveals that the open-circuit operating point decreases slightly as the angle of incidence increases. In contrast, the gallium doping level has a more pronounced impact on the open-circuit operating point, suggesting a deeper influence on the internal properties of the material. Finally, the article uses electrical models to deduce the values of the cell's series and shunt resistances, based on the observed operating points. This analysis shows that both the angle of incidence and the gallium doping rate tend to increase these resistances. These increases can degrade cell performance by introducing energy losses, highlighting the importance of these two parameters in the design and optimization of CIGS solar cells.