Improved quantum efficiency of solar cells with Ge dots stacked in multilayer structure

We report on the improved external quantum efficiency of solar cells in the infrared region with self-assembled Ge dots stacked in multilayer structure embedded within the intrinsic region of a p-i-n diode. This quantum efficiency was found to increase with increasing number of stacking. This indicates that additional photocarriers are generated in the Ge dots and have a high probability of escaping from the dots and/or at Ge/Si interfaces without significant recombination under the influence of the internal electric field.