Effects of germanium layer on silicon/germanium superlattice solar cells

Silicon germanium solar cells have widely been explored in recent years due to the property of germanium material that is capable to absorb light in low energy (IR range). However, the lattice mismatch between the silicon and germanium materials may lead to misfit dislocation defect on the solar cell. The defect can be reduced by arranging the silicon and germanium materials in superlattice (multilayer) structures whereby more lights can be absorbed by the solar cell which will increase its efficiency. In this paper, PC1D solar cell modeling software has been used to simulate and analyze the effects of the germanium thickness on the silicon/germanium superlattice (multilayer) solar cell. The total thickness is limited to 1μm. The simulation result shows that an efficiency of 10.16% (V_OC = 0.4521V, I_SC = 3.337A, FF =0.6734) is achieved with 0.2μm-Ge and 0.2μm-Si window layer, and 0.6μm-Si absorber layer.