Exciton thermal radiation from structure-sorted carbon nanotube membranes

TL;DR

This study demonstrates that structure-sorted carbon nanotube membranes can emit stable exciton thermal radiation at high temperatures, offering potential for selective thermal emission and energy harvesting applications.

Contribution

It provides the first evidence of macroscale SWCNT assemblies emitting exciton thermal radiation under conduction heating, highlighting their unique properties compared to bulk semiconductors.

Findings

Peaked exciton thermal radiation observed at 850 K.

Exciton resonance remains robust at high temperatures.

Membranes maintain transparency below the optical gap at elevated temperatures.

Abstract

Owing to their small binding energies, excitons in bulk semiconductors typically exhibit a sharp optical peak at low temperatures only. This limitation can be overcome by single-walled carbon nanotubes (SWCNTs) and other low-dimensional semiconductors with highly enhanced exciton binding energies. Exciton thermal radiation, which can potentially be exploited for selective thermal emission and energy harvesting, has been recently observed in individual SWCNTs heated under photoirradiation. However, whether macroscale-SWCNT assemblies can emit exciton thermal radiation under conduction heating remains unclear and constitutes an important challenge for practical applications. Herein, we observed peaked exciton thermal radiation from structure-sorted SWCNT membranes. Transmission spectroscopy showed robust exciton resonance at high temperatures, resulting in clear exciton resonance in the thermal radiation band. The absolute emissivity spectra of the membranes were determined at 850 K. Exciton dominance suppresses the contribution of thermal free carriers to the infrared absorption/emission spectra, maintaining the transparency below the optical gap even at elevated temperatures. These phenomena are not observed in bulk semiconductors, highlighting the structure-sorted SWCNT membranes as unique semiconductors leveraging stable exciton resonances at elevated temperatures.