Simulation study of Ge/Si heterostructure solar cells yielding improved open-circuit voltage and quantum efficiency

The performance of crystalline Si solar cells with type-II Ge/Si heterostructures is numerically investigated using a simple p-Si/Si 1− x Ge x /n-Si model with carrier recombination at the Si 1− x Ge x layer. From an analysis of the open-circuit voltage ( V oc ), we find that carrier recombination at the Si 1− x Ge x layer dominates the solar cell performance, and further suppression of this behavior is therefore the key to improving V oc . Furthermore, we discuss the device structure required to improve V oc and the quantum efficiency and find that the thin p-Si layer should be located on the front side to improve quantum efficiency in the visible region.