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Title: Fluorescent cooling of objects exposed to sunlight – The ruby example

Abstract

Various pigments are used to formulate desirable non-white colors that stay cooler in the sun than alternatives, which is particularly useful for hot climate areas. These cool pigments provide a high near-infrared (NIR) reflectance in the solar infrared range of 700-2500 nm, and also a color specified by a reflectance spectrum in the 400-700 nm visible range. Still cooler materials can be formulated by also utilizing the phenomenon of fluorescence (photoluminescence). Ruby, Al 2O 3 :Cr, is a prime example, with efficient emission in the deep red (~694 nm) and near infrared (700-800 nm). A layer of synthetic ruby crystals on a white surface having an attractive red color can remain cooler in the sun than conventional red materials. Ruby particles can also be used as a red/pink pigment. Increasing the Cr:Al ratio produces a stronger (darker) pigment but doping above ~3 wt% Cr 2O 3 causes concentration quenching of the fluorescence. The system quantum efficiency for lightly doped ruby-pigmented coatings over white is high, 0.83 ± 0.10.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B)
OSTI Identifier:
1398444
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Solar Energy Materials and Solar Cells; Journal Volume: 157; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 14 SOLAR ENERGY

Citation Formats

Berdahl, Paul, Chen, Sharon S., Destaillats, Hugo, Kirchstetter, Thomas W., Levinson, Ronnen M., and Zalich, Michael A. Fluorescent cooling of objects exposed to sunlight – The ruby example. United States: N. p., 2016. Web. doi:10.1016/j.solmat.2016.05.058.
Berdahl, Paul, Chen, Sharon S., Destaillats, Hugo, Kirchstetter, Thomas W., Levinson, Ronnen M., & Zalich, Michael A. Fluorescent cooling of objects exposed to sunlight – The ruby example. United States. doi:10.1016/j.solmat.2016.05.058.
Berdahl, Paul, Chen, Sharon S., Destaillats, Hugo, Kirchstetter, Thomas W., Levinson, Ronnen M., and Zalich, Michael A. Sat . "Fluorescent cooling of objects exposed to sunlight – The ruby example". United States. doi:10.1016/j.solmat.2016.05.058.
@article{osti_1398444,
title = {Fluorescent cooling of objects exposed to sunlight – The ruby example},
author = {Berdahl, Paul and Chen, Sharon S. and Destaillats, Hugo and Kirchstetter, Thomas W. and Levinson, Ronnen M. and Zalich, Michael A.},
abstractNote = {Various pigments are used to formulate desirable non-white colors that stay cooler in the sun than alternatives, which is particularly useful for hot climate areas. These cool pigments provide a high near-infrared (NIR) reflectance in the solar infrared range of 700-2500 nm, and also a color specified by a reflectance spectrum in the 400-700 nm visible range. Still cooler materials can be formulated by also utilizing the phenomenon of fluorescence (photoluminescence). Ruby, Al2O3 :Cr, is a prime example, with efficient emission in the deep red (~694 nm) and near infrared (700-800 nm). A layer of synthetic ruby crystals on a white surface having an attractive red color can remain cooler in the sun than conventional red materials. Ruby particles can also be used as a red/pink pigment. Increasing the Cr:Al ratio produces a stronger (darker) pigment but doping above ~3 wt% Cr2O3 causes concentration quenching of the fluorescence. The system quantum efficiency for lightly doped ruby-pigmented coatings over white is high, 0.83 ± 0.10.},
doi = {10.1016/j.solmat.2016.05.058},
journal = {Solar Energy Materials and Solar Cells},
number = C,
volume = 157,
place = {United States},
year = {Sat Jun 04 00:00:00 EDT 2016},
month = {Sat Jun 04 00:00:00 EDT 2016}
}