Observing of the super-Planckian near-field thermal radiation between graphene sheets

TL;DR

This study experimentally demonstrates super-Planckian near-field thermal radiation between graphene sheets, showing a 4.5-fold increase over blackbody radiation, confirming the role of graphene plasmons in thermal enhancement.

Contribution

First direct measurement of plasmon-mediated near-field thermal radiation between macroscopic graphene sheets, validating theoretical predictions and exploring applications in thermal management.

Findings

Observed super-Planckian radiation 4.5 times the blackbody limit at 430 nm gap

Confirmed the role of graphene plasmons in thermal radiation enhancement

Discussed potential for near-field thermophotovoltaic applications

Abstract

Thermal radiation can be substantially enhanced in the near-field scenario due to the tunneling of evanescent waves. The monolayer graphene could play a vital role in this process owning to its strong infrared plasmonic response, however, which still lacks an experimental verification due to the technical challenges. Here, we manage to make a direct measurement about plasmon-mediated thermal radiation between two macroscopic graphene sheets using a custom-made setup. Super-Planckian radiation with efficiency 4.5 times larger than the blackbody limit is observed at a 430-nm vacuum gap on insulating silicon hosting substrates. The positive role of graphene plasmons is further confirmed on conductive silicon substrates which have strong infrared loss and thermal emittance. Based on these, a thermophotovoltaic cell made of the graphene-silicon heterostructure is lastly discussed. The current work validates the classic thermodynamical theory in treating graphene and also paves a way to pursue the application of near-field thermal management.