Thermophotovoltaic and photovoltaic conversion at high-flux densities

We first discuss the similarities between generation of electricity using thermophotovoltaic (TPV) and high-optical-concentration solar photovoltaic (PV) devices. Following this, we consider power losses due to above- and below-bandgap photons, and we estimate the ideal bandgap by minimizing the sum of these, for a 6000 K black-body spectrum. The ideal bandgap, based on this approach, is less than that previously predicted, which could have a significant influence on the performance of devices and systems. To reduce the losses, we show that the low-energy photons may be removed from both types of cells and consider the specific case of a back-surface reflector. This approach to the management of waste heat may offer a useful additional tool with which to facilitate the design of high-photon-flux solar cells. In the case of the high-energy photons and the associated problem of thermalization of hot electrons, however, the heat must be removed by other means, and we consider the applicability of microchannel cooling systems. These appear to have the potential to handle thermal loads at least several times those generated by 1000 times concentrators, or by black-body TPV radiators at a temperature of far greater than 1500 K. We go on to consider the management of the very high currents generated in both concentrator TPV and PV systems and discuss the concept of the monolithically integrated minimodule.