New absorber and emitter designs and high temperature materials for thermophotovoltaics

Thermophotovoltaic (TPV) solar cells, where broad-band solar radiation is absorbed by an intermediate, which then emits narrow-band thermal radiation towards a solar cell have been proposed for some time as a route for high efficiency solar energy harvesting. However, due to limitations in both design of the active components, as well as the high temperature stability of the materials making up these systems, the theoretical maximum efficiency of 85% for such devices has not been realized. We are currently exploiting emerging opportunities in the design and fabrication of metallic photonic crystals for TPV applications. We have now demonstrated tungsten based 3D photonic crystals which retain micron-scale structure even at temperatures of 1300 K, and are exploring other materials systems that may have even higher temperature stability. Through simulation and modeling, we have designed a number of absorber/emitter structures that match both the broad-band solar spectrum and the desired narrow band emission required for efficient single-junction solar cells. The self and directed assembly methods used to fabricate the TPV structures can produce complex large-area structures at low cost.