The Effect of an Organic Selectively-Reflecting Mirror on the Performance of a Luminescent Solar Concentrator

Abstract

To reduce the surface losses in the luminescent solar concentrator (LSC) we have applied an organic wavelength-selective mirror, a chiral nematic (cholesteric) liquid crystal, onto a fluorescent waveguide with a small air gap in between. We compare the light outputs of the waveguide with absorbing, scattering, and mirrored bottoms. The highest light output is achieved using a scattering background and a cholesteric mirror with a reflection band significantly red-shifted with respect to the emission spectrum of the fluorescent dye. The use of an air gap results in refraction and light bending away from the normal and, consequently, a red shift of the cholesteric mirrors is required which also negatively affects its performance. A 15% increase in edge power output is demonstrated at low dye concentrations, suggesting light that is emitted to the surface of the waveguide is re-directed by the mirrors to the edge with an efficiency of about 35%. At high fluorescent dye concentrations, the chiral-nematic mirrors have reduced impact on dye emission.