Thermophotovoltaics

Analogous to solar energy generation, in thermophotovoltaics (TPV), radiant energy is converted into electricity using photovoltaic cells. In contrast to the energy source used in solar cells, however, the radiant energy does not come from the sun, but is emitted in the form of thermal radiation (long-wave photons) by a hot emitter. Special thermophotovoltaic cells made of absorber materials with band gaps in the infrared range can efficiently convert this thermal radiation into electrical power. 

Interesting applications can be found in waste heat recovery or thermal batteries, which store excess energy from renewable energy sources as high-temperature heat and convert it back into electricity on demand using thermophotovoltaics.

Especially for the latter, the conversion efficiency of the TPV cells is decisive. Here, intelligent photon management structures and back mirrors that reflects useless low energy photons back to the heat source enables very high performances

At Fraunhofer ISE, we develop customized low-bandgap III-V absorber materials based on GaAs, InP, GaSb, and Ge, as well as highly transparent tunnel diodes. In addition, we use metamorphic buffer layers to create so-called "engineered substrates" based on GaAs to replace comparatively expensive InP substrates. We also develop thin-film processes and highly reflective, electrically conductive mirror layers for efficient photon management. Finally, we provide our expertise to our customers in the development of dense array receivers and the necessary packaging technology.