Graphene-enhanced near-field thermophotonic system for efficient heat-to-electricity conversion

Near-field thermophotonics can enhance the power density and efficiency of converting heat into electricity by leveraging the amplification of near-field thermal radiation within a nanoscale vacuum gap. Here, we propose a graphene-enhanced near-field thermophotonic converter (NF-TPC), which features a light-emitting diode (LED) emitter made from GaAs and a narrow bandgap photovoltaic (PV) cell composed of InAs, integrated with various configurations of graphene coating. Numerical calculations show that the graphene-assisted NF-TPC can achieve a heat-to-electricity conversion efficiency of nearly 32% (reaching 45% of the Carnot efficiency) and a power density of 7 W/cm2 at an LED temperature of 1000 K and a 10 nm gap distance. In addition, applying graphene coating on the LED, regardless of the PV cell’s graphene coating, can significantly boost the output power density (by 17%) and conversion efficiency (by 62%) within a certain gap range by suppressing and enhancing the sub- and above-bandgap photon flux, respectively. We also discuss how the chemical potential of graphene affects the NF-TPC performance. By altering the chemical potential of graphene, the configuration with graphene coating on both the LED and PV sides yields a maximum efficiency of 32.8%. Therefore, our work reveals promising avenues for enhancing and manipulating the optimal performance of the NF-TPC device at the nanoscale and microscale.