Issue 37, 2022

Effects of Stokes shift and Purcell enhancement on fluorescence-assisted radiative cooling

Abstract

Passive daytime radiative cooling has been widely investigated ascribed to the great potential in combatting energy crisis and global warming. Polymeric coatings comprising functional fillers with solar reflectance and infrared emissivity both over 0.9 have proven to be particularly effective for sub-ambient daytime radiative cooling. However, the intrinsic absorption of many functional fillers with optical bandgaps within the solar spectrum reduces the cooling potential and consequently limits material choices. It has recently been demonstrated that introducing fluorescent materials into polymeric coatings can convert the absorbed sunlight to fluorescent emissions and hence increase the effective solar reflectance and cooling performance. In this work, we carry out a systematic experimental investigation on the influence of Stokes shift and Purcell enhancement in such fluorescence-mediated radiative cooling. We find that using phosphors with smaller Stokes shifts and nanoparticle fillers of appropriate sizes can significantly enhance the effective solar reflectance. We show that matching the emission wavelengths of two phosphors with the Mie scattering resonance wavelengths of the TiO2 nanoparticle fillers shortens their fluorescence lifetimes by 61% and 23%, respectively, indicating Purcell enhancement factors of 2.6 and 1.3 and ultimately increasing the effective solar reflectance of the fluorescent coatings by up to ∼4% in field tests. The fluorescence enhancement approach demonstrated here provides an effective strategy for making radiative cooling coatings compatible with commercially available inexpensive engineering materials and potential for realizing colored coatings.

Graphical abstract: Effects of Stokes shift and Purcell enhancement on fluorescence-assisted radiative cooling

Supplementary files

Article information

Article type
Communication
Submitted
21 Mär 2022
Accepted
23 Mai 2022
First published
24 Mai 2022

J. Mater. Chem. A, 2022,10, 19635-19640

Effects of Stokes shift and Purcell enhancement on fluorescence-assisted radiative cooling

X. Ma, Y. Fu, A. Portniagin, N. Yang, D. Liu, A. L. Rogach, J. Dai and D. Lei, J. Mater. Chem. A, 2022, 10, 19635 DOI: 10.1039/D2TA02259A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements