Analysis of Near-Field Thermophotovoltaic Devices Using Graphene-Germanium Schottky Cell

In this work, we investigate the performance of graphene-based Schottky junction thermophotovoltaic (TPV) devices in near-field conditions. Despite the low cost and excellent photoelectric properties of graphene, earlier studies have focused primarily on the contribution of the graphene layer to the photocurrent, assuming an internal quantum efficiency (IQE) of 100%. Our numerical model of a graphene/germanium Schottky junction TPV device reveals that the semiconductor layer predominates in the generation photocurrent, with an IQE of graphene less than 40%. We also evaluate the photocurrent densities generated by the semiconductor and graphene at an emitter temperature of 1000 K and a vacuum gap of 100 nm. Results show that using an indium tin oxide (ITO)-covered tungsten (W) emitter can increase photocurrents by a factor of around 10 and 11 for the semiconductor and graphene, respectively. Additionally, using a hyperbolic metamaterial (HMM) emitter can enhance photocurrents by around 4.7 and 5.2 times for the semiconductor and graphene, respectively. However, this comes at the cost of higher heat flux from the HMM emitter. Our findings will provide valuable insights for the design and optimization of TPV devices to improve their photocurrent and efficiency.