A “generalized brightness theorem” is derived that describes the thermodynamic limitations of the fluorescent planar concentrator. The maximum brightness concentration ratio allowed by thermodynamics is exp (hΔv/kT) where Δv is the Stokes shift in fluorescence.
© 1980 Optical Society of America
Eli Yablonovitch, "Thermodynamics of the fluorescent planar concentrator," J. Opt. Soc. Am. 70, 1362-1363 (1980)