Photonic Crystal Waveguides for >90% Light Trapping Efficiency in Luminescent Solar Concentrators

Abstract

Luminescent solar concentrators are currently limited in their potential concentration factor and solar conversion efficiency by the inherent escape cone losses present in conventional planar dielectric waveguides. We demonstrate that photonic crystal slab waveguides tailored for luminescent solar concentrator applications can exhibit >90% light trapping efficiency. This is achieved by use of quantum dot luminophores embedded within the waveguide that absorb light at photon energies corresponding to photonic crystal leaky modes that couple to incoming sunlight. The luminophores then emit at lower photon energies into photonic crystal bound modes that enable highly efficient light trapping in slab waveguides of wavelength-scale thickness. Photonic crystal waveguides thus nearly eliminate escape cone losses, and overcome the performance limitations of previously proposed wavelength-selective dielectric multilayer filters. We describe designs for hole-array and rod-array photonic crystals comprised of hydrogenated amorphous silicon carbide using CdSe/CdS quantum dots. Our analysis suggests that photonic crystal waveguide luminescent solar concentrators using these materials these can achieve light trapping efficiency above 92% and a concentration factor as high as 100.

Heat Generated Using Luminescent Solar Concentrators for Building Energy Applications

“…Emission losses can also be reduced by using dielectric mirrors at the surface of the LSC modules [28]. Moreover, diffractive structures such as gratings and photonic crystals located at the surface of LSC modules can enhance the propagation of incident solar photons to the LSC sidewalls [29][30][31][32]. The shape and size of the LSC also affect its efficiency [33]; generally, the efficiency of LSCs increases with decreasing size, however, the edge-length of the LSCs also increases with decreasing size which may make it more difficult to collect thermal energy generated at the LSC sidewalls.…”

Optical Resonator Enhanced Photovoltaics and Photocatalysis: Fundamental and Recent Progress

“…Moving on from 1D to 2D, Bauser et al demonstrated a luminescent solar converter with more than 90% light-trapping efficiency by using 2D PC slab consisting of a high index dielectric rod and holes (Figure 6b). [145] The PL quantum yield of the QDs was enhanced owing to the large local density of states (LDOS) induced by Purcell effect. Another example in Figure 6c presents a high efficiency perovskite solar cells by using a 2D-PC nanodisk array, which was fabricated by nanosphere lithography.…”

“…Reproduced with permission. [145] Copyright 2020, American Chemical Society. c) Left: Device architecture of 2D nanodisk perovskite solar cells.…”

“…Right: Enhancement of QD PL quantum yield as a function of Purcell factor. Reproduced with permission [145]. Copyright 2020, American Chemical Society.…”

Should Anisotropic Emission or Reabsorption of Nanoparticle Luminophores Be Optimized for Increasing Luminescent Solar Concentrator Efficiency?

“…[ 10 ] The main strategies that have been developed so far to tackle the escape cone losses are 1) the use of aligned dichroic dyes in liquid crystals, [ 11,12 ] 2) the application of wavelength‐selective mirrors that allow incoming light to enter the lightguide and be absorbed, but are reflective for wavelengths emitted by the luminophore, [ 9,10,13–15 ] and 3) the use of photonic crystal waveguides in which the luminophores are embedded. [ 16 ] More recently, alignment of a pair of luminophores, i.e., a sphere‐shaped energy donor and a rod‐shaped emitter, both organic, has been reported to decrease escape cone losses by 10% relative. [ 17 ]…”