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-hexagonalboron-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 × 105 W/m2,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.

Energy cooperation in quantum thermoelectric systems with multiple electric currents

The energy efficiency and output power of a quantum thermoelectric system with multiple electric currents and only one heat current are studied.The system is connected to the hot heat bath(cold bath)through one terminal(multiple terminals).In such configurations,there are multiple thermoelectric effects coexisting in the system.Using the Landauer–Buttiker formalism,we show that the cooperation between the two thermoelectric effects in the three-terminal thermoelectric systems can lead to markedly improved performance of the heat engine.Such improvement also occurs in four-terminal thermoelectric heat engines with three output electric currents.Cooperative effects in these multi-terminal thermoelectric systems can considerably enlarge the physical parameter region that realizes high energy efficiency and output power.For refrigeration,we find that the energy efficiency can also be substantially improved by exploiting the cooperative effects in multi-terminal thermoelectric systems.All these results reveal a useful approach toward high-performance thermoelectric energy conversion in multi-terminal mesoscopic systems.

Coulomb Thermoelectric Drag in Four-Terminal Mesoscopic Quantum Transport

We show that the Coulomb interaction between two circuits separated by an insulating layer leads to unconventional thermoelectric effects,such as the cooling by thermal current effect,the transverse thermoelectric effect and Maxwell’s demon effect.The first refers to cooling in one circuit induced by the thermal current in the other circuit.The middle represents electric power generation in one circuit by the temperature gradient in the other circuit.The physical picture of Coulomb drag between the two circuits is first demonstrated for the case with one quantum dot in each circuit and it is then elaborated for the case with two quantum dots in each circuit.In the latter case,the heat exchange between the two circuits can vanish.Finally,we also show that the Maxwell’s demon effect can be realized in the four-terminal quantum dot thermoelectric system,in which the quantum system absorbs the heat from the high-temperature heat bath and releases the same heat to the low-temperature heat bath without any energy exchange with the two heat baths.Our study reveals the role of Coulomb interaction in non-local four-terminal thermoelectric transport.