Abstract
Thermophotovoltaic (TPV) systems, which convert heat into electricity by irradiating PV cells with thermal
emission from heated objects, feature their high output power density and potentially high conversion
efficiency. To increase the output power density and conversion efficiency of TPV systems, it is important
to enhance the thermal emission above the bandgap energy of the PV cell while suppressing the
emission below it. Here, we show our recent experimental demonstrations of far-field and near-field
TPV systems based on photonic nanostructures. In the far-field experiment, we develop silicon rod-type
photonic-crystal thermal emitters which exhibit near-infrared frequency-selective thermal emission with
suppressed background emission, and demonstrate a heat-to-electrical conversion efficiency of 11.2% at
1338 K. In the near-field experiment, we develop a one-chip near-field TPV device integrating a thinfilm
Si emitter and InGaAs PV cell with a deep sub-wavelength gap (＜150 nm), achieving photocurrent
generation overcoming the far-field blackbody limit at 1192 K.
