Analytical investigation of five-junction solar cell behavior based on Ge layers and InAlGaAs and InAlGaP alloys

In recent years, we have witnessed significant advancements in the production of solar cells with a reduction in cost and an increase in their efficiency. One of the stages in creating advancements in new cells is evaluating their performance under different conditions using simulations before their fabrication. In this article, the structure of a multi-junction solar cell composed of Ge layers, InAlGaAs alloys, and InAlGaP alloys will be comprehensively examined. To achieve the highest efficiency, the lowest absorbing layer of the solar cell (Ge solar cell) will initially be optically simulated and then electrically simulated. After optimizing the Ge solar cell, the intermediate layers between the cells (tunnel junctions) and then the upper absorbing layers will be optimized in sequence. Optimization of solar cells in each absorbing layer refers to selecting the appropriate thickness, impurity density, and molar percentage of the layers to achieve the highest efficiency. According to simulation results, an efficiency of over 49\% has been achieved for the 5-junction cell.