Moderate-Temperature Near-Field Thermophotovoltaic Systems with Thin-Film InSb Cells

Near-field thermophotovoltaic systems functioning at 400-900 K based on graphene-hexagonal-boron-nitride heterostructures and thin-film InSb p-n junctions are investigated theoretically. The performances of two near-field systems with different emitters are examined carefully. One near-field system consists of a graphene-hexagonal-boron-nitride-graphene sandwiched structure as the emitter, while the other system has an emitter made of the double graphene-hexagonal-boron-nitride heterostructure. It is shown that both systems exhibit higher output power density and energy efficiency than the near-field system based on mono graphene-hexagonal-boron-nitride heterostructure. The optimal output power density of the former device can reach 1.3 x 10(5) W/m(2), while the optimal energy efficiency can be as large as 42% of the Carnot efficiency. We analyze the underlying physical mechanisms that lead to the excellent performances of the proposed near-field thermophotovoltaic systems. Our results are valuable toward high-performance moderate temperature thermophotovoltaic systems as appealing thermal-to-electric energy conversion (waste heat harvesting) devices.