Using selectively-reflecting organic mirrors to improve light output from a luminescent solar concentrator

摘要

The luminescent solar concentrator (LSC) is an optically clear waveguide doped with luminescent dye molecule(s). Incident light is absorbed and re-emitted by the fluorescent dye, a portion of this light is trapped by total internal reflection and transported to one edge to a small photovoltaic (PV) cell. With improvements in light emission, a LSC with a high performance PV could become competitive with standard silicon PV arrays within 5 years as it is less expensive (cost reductions of a factor 2-3), works in diffuse light and requires no sun tracking. Normally, over half of the light emitted by the fluorescent dye molecules is lost through the waveguide surface. Placing two selectively-reflecting cholesteric liquid crystalline film layers (one right-handed and one left) on the waveguide recovers this light, increasing the output of the LSC by more than 60%. The reflection bandwidth for a typical cholesteric is about 75 nm, which only covers part of the emission spectra of the fluorescent dyes. To more completely contain the dye-emitted light, we broadened the reflection band to >200 nm. In this broadband system we recovered 140% more light than from the dye layer alone.