Thermoelectric Power Conversion using Generation of Electron-Hole Pairs in Large Area p-n Junctions

A new method for thermoelectric power generation using large area pn-junctions is presented [Span, et al., 2005]. Normally, thermal generation of electron-hole pairs is avoided because of the deteriorating effects of the minority carriers on the efficiency in classical thermocouples. A temperature gradient applied along the pn-junction causes a flux of carriers from hot to cold due to the Seebeck effect, which introduces a reverse bias and thus thermal generation in the hot part of the pn-structure. The generation of electron-hole pairs leads to a multitude of new properties that can be used to enhance the efficiency of the energy conversion. The generation rate of electron-hole pairs is a highly adjustable parameter, which makes it possible to tailor thermoelectric elements and modules to given boundary conditions. This is achieved by changing the amount and distribution of generation centers and the shape of the temperature gradient as well as the choice of the material system. Due to the generation of electrons and holes, no contact on the hot side of the thermoelectric element is necessary. Limitations of the hot side temperature caused by mechanical stress due to different thermal expansion of different materials or by the solder or joining material are therefore non-existing. To describe these structures, an effective figure of merit Z_eff is calculated using the device simulator Minimos-NT [2004]