Device Architectures for Germanium TPV Cells with Efficiencies over 30%

Germanium based TPV cells could be a promising cost-effective candidate for their integration in early pre-commercial thermal battery prototypes. In this work we aim to thoroughly explore the properties of lightly doped Germanium TPV converters. In order to do so, several TPV cells have been manufactured and an extensive experimental work has been carried out. A detailed analysis of the optical and electrical properties of the devices is presented. Data shows a significant improvement in the spectral management in the lightly doped devices, at the cost of an important decrease of the carrier management. As a result, TPV efficiencies of just 15.4% are obtained for our devices. Further simulations based on these data show that an increase from the current TPV efficiency values to a 25% efficiency could be at reach for Germanium converters introducing some optimizations in our design, while the objective performance of a 30% is at the limit achievable for the technology. Finally, a roadmap is proposed to improve the current design until these objectives are met.