Performance predictions for monolithic, thin-film CdTe/Ge tandem solar cells

Cadmium telluride thin-film solar cells are now commercially available and are being widely deployed in terrestrial, photovoltaic, power plants. However, the price of electricity from such sources would be more competitive with conventionally generated electricity if the cell efficiency could be improved without compromising the generally low-cost nature of the fabrication process. Recognizing that laboratory cells appear to have reached an efficiency limit of about 16.5%, we propose to improve on this by adding a thin-film germanium cell in a monolithic, tandem arrangement. Here we report on simulations of the photovoltaic performance of this structure, and we indicate that an efficiency improvement in excess of 20% may be attainable.