ABSTRACT
Thermophotovoltaic (TPV) systems convert heat into electricity using thermal emission from heated objects at high temperatures and photovoltaic (PV) cells. TPV systems feature the versatile usage of thermal sources, their high output power density, and potentially high conversion efficiency. To increase the output power density and conversion efficiency, it is necessary to enhance the thermal emission intensity just above the bandgap energy of the photovoltaic (PV) cell while suppressing the emission intensity below it. In this chapter, recent experimental demonstrations of far-field and near-field TPV systems based on photonic nanostructures are discussed toward high-power high-efficiency power generation. In the far-field experiment, a heat-to-electrical conversion efficiency of 11.2% is demonstrated by using silicon rod-type photonic-crystal thermal emitters which exhibit near-infrared thermal emission with suppressed background emission. In the near-field experiment, a one-chip near-field TPV device integrating a thin-film Si thermal emitter and InGaAs PV cell with a deep sub-wavelength gap is developed, where photocurrent generation overcoming the far-field blackbody limit is realized.
