Effects of multilayered graphene on the performance of near-field thermophotovoltaic system at longer vacuum gap distances

Abstract

The present work aims to enhance the performance of near-field thermophotovoltaic (TPV) system operated at low temperature by introducing multilayered graphene on top of the TPV cell. The multilayered graphene shifts the surface plasmon polariton to the condition where heat flux occurs efficiently at vacuum gap longer than 50nm. It is found that three-layer graphene can increase the power output by 5.8 times at 50-nm vacuum gap, whereas a monolayer of graphene has a negligible effect at such distance. The fundamental mechanism for the enhancement by the multilayered graphene is explored by analyzing the heat transfer and corresponding photocurrent generation through three modes: propagating, frustrated, and surface modes. Through the detailed analysis, the optimal number of the graphene layers depending on the vacuum gap distance can be predicted. Considering a penetration depth inside the TPV cell, the effect of the width of p-region of the cell on the power output is discussed. It is shown that the change of the width of p-region can either improve or suppress the effect of graphene. The results obtained in this study can facilitate future development of practical TPV system with high performance.