Modeling of GaAsxP1-x/CIGS tandem solar cells under stress conditions

In this paper, we design a four-terminal gallium arsenide phosphide (GaAsxP1-x)/copper indium gallium selenide (CIGS) tandem solar cell by the analytical model. We used the experimental data for GaAsxP1-x and CIGS cells to validate this model. In this work, we achieved a 30% efficiency for the optimum GaAsxP1-x/CIGS tandem solar cell. Our proposed model determines the optimized bandgap of GaAsxP1-x as the top cell is within the range from 1.79 eV to 1.95 eV (0.57 < x < 0.7). Next, we investigate the degradation in the performance parameters of our tandem solar cell, considering the aging time under stress conditions. In this condition, the defect density increases exponentially over time, and the depletion width decreases with time. The results show that for an optimal GaAs0.6P0.4/CIGS tandem structure, after 277 h (t = 106 s), efficiency decreases by 35.6% under stress conditions. Improving the stability of GaAs0.6P0.4/CIGS tandem solar cell makes this configuration a greater potential to be used in space applications.