Towards photonic luminescent solar concentrators

Luminescent solar concentrators (LSC) concentrate both diffuse and direct radiation with no need for tracking. They consist of transparent plates doped with luminescent materials that absorb incident light. Most of the emitted light is trapped inside the plate by total internal reflection, where it is guided to solar cells at the plate's edge faces. We investigate the concept of a photonic LSC (PLSC) that mitigates the major LSC loss mechanisms, namely the escape cone and reabsorption of emitted light. Embedding the luminescent material in a photonic crystal allows highly efficient light guiding and can reduce reabsorption through inhibited emission at unwanted wavelengths. We present FDTD simulations that show how the emission characteristic is influenced by the surrounding structure due to an altered photon density of states. Further, enhanced light guiding in a broad spectral range was obtained with efficiencies of up to 99.7%. We also report on our progress in fabrication of PLSC devices for experimental investigation of the concept: polymer thin films with and without luminescent doping were spin coated and characterized to estimate the number of dye layers needed in PLSCs to achieve sufficiently high absorption.