Performance Analysis and Simulation of c-Si/SiGe Based Solar Cell

Silicon Germanium (SiGe) solar cells with different bandgaps are used in the fabrication of the crystalline-Si/SiGe (c-Si/SiGe) double-junction cell in order to enhance the performance of the c-Si single devices. The new device is simulated with SCAPS-1D by placing the c-Si junction on the top of the SiGe solar cell. Through this simulation, one can assess the performance of the c-Si/SiGe double-junction device. The upper c-Si cell achieved an efficiency of 16.66% with 40.5 μm total thickness, while the lower cell SiGe achieved ~ 19% efficiency. By analyzing the current matching between both cells at different bandgaps for SiGe cell (1.097 eV, 1.016 eV, and 0.928 eV), a mismatch is found. But, when applying 0.882 eV bandgap for the lower cell with absorber thicknesses of 110, 100, 90, and 6.2 μm, a matching is obtained between the two junctions. The efficiency of the designed cell is found ~ 24.7%, with a maximum current density of 30.25 mA/cm2, achieved at an open circuit voltage of 1.01 V and a total thickness of 57.2 μm. These results indicate that the double-junction device significantly exceeds the device performance by 7.6% with equal thickness of the optimized single-junction c-Si solar cell.