  Near-field thermal radiation transfer overcoming the far-field blackbody
limit has attracted significant attention in recent years owing to its
potential for drastically increasing the output power and conversion efficiency
of thermophotovoltaic (TPV) power generation systems. Here, we experimentally
demonstrate a one-chip near-field TPV device overcoming the far-field blackbody
limit, which integrates a 20-um-thick Si emitter and an InGaAs PV cell with a
sub-wavelength gap (<140 nm). The device exhibits a photocurrent density of
1.49 A/cm2 at 1192 K, which is 1.5 times larger than the far-field limit at the
same temperature. In addition, we obtain an output power of 1.92 mW and a
system efficiency of 0.7% for a 1-mm2 device, both of which are one to two
orders of magnitude greater than those of the previously reported near-field
systems. Detailed comparisons between the simulations and experiments reveal
the possibility of a system efficiency of >35% in the up-scaled device, thus
demonstrating the potential of our integrated near-field TPV device for
practical use in the future.

Applied Physics;Optics