Integrating Photonics with Luminescent Solar Concentrators: Optical Transport in the Presence of Photonic Mirrors

Abstract

Luminescent solar concentrators downshift and concentrate the incident solar spectrum onto adjacent solar cells. In this paper we study the combination of highly performing luminescent nanocrystals with photonic structures to guide light to the edge of the concentrator. While one approach is to use a wavelength-selective Bragg mirror to reduce escape cone losses, we find that this also requires nearly perfect mirrors and luminophore quantum yield. The key issue is that light is trapped inside the concentrator in modes that inefficiently propagate toward the edge, leading to luminophore reabsorption and losses to imperfect mirrors. To overcome this difficulty, we use modeling to study the use of meta-mirrors that shift propagating photons to larger angles, minimizing interactions with the reabsorbing luminophores and mirrors. We find that this design favors mirrors with small changes in angle, separated from the luminophore–polymer layer by an air gap. This research indicates that a combination of photonic structures can be used with imperfect luminescent materials and mirrors to enable high optical efficiency from luminescent concentrators.

Biomimetic light-harvesting funnels for re-directioning of diffuse light

“…Capturing light re-emitted under these unfavorable angles requires expensive dichroic coatings 22 – 29 and causes multiple reflections and reabsorption losses as well as inefficient incident angles at the photovoltaic devices 30 , 31 . To prevent inefficient angles, LSCs have also been proposed that are based on pigments with purposely oriented transition dipole moments enabling direction of the light into much more favorable angle ranges.…”

The Renaissance of Luminescent Solar Concentrators: The Role of Inorganic Nanomaterials

“…This can be (i) a simple back-reflector, whose function is to increase the optical path of the incident photon within the doped polymer, acting on the η abs and consisting in a diffuse or specular mirror, (ii) a semireflective mirror, reducing the number of emitted photons lost by selectively trapping them within the polymer waveguide, [33] acting therefore on η trap , and consisting of a photonic aperiodic mirror, [34] or a distributed Bragg reflector, [35] or (iii) a resonant shifting bilayer cavity [36] where the emission from a nanostructured layer containing the luminescent material is trapped in a low refractive index layer, achieving a large drop of reabsorption events probability. This can be (i) a simple back-reflector, whose function is to increase the optical path of the incident photon within the doped polymer, acting on the η abs and consisting in a diffuse or specular mirror, (ii) a semireflective mirror, reducing the number of emitted photons lost by selectively trapping them within the polymer waveguide, [33] acting therefore on η trap , and consisting of a photonic aperiodic mirror, [34] or a distributed Bragg reflector, [35] or (iii) a resonant shifting bilayer cavity [36] where the emission from a nanostructured layer containing the luminescent material is trapped in a low refractive index layer, achieving a large drop of reabsorption events probability.…”

“…The first of them consists in the addition of a reflective layer on the surface of the polymer/glass waveguide. This can be (i) a simple back‐reflector, whose function is to increase the optical path of the incident photon within the doped polymer, acting on the η abs and consisting in a diffuse or specular mirror, (ii) a semireflective mirror, reducing the number of emitted photons lost by selectively trapping them within the polymer waveguide, acting therefore on η trap , and consisting of a photonic aperiodic mirror, or a distributed Bragg reflector, or (iii) a resonant shifting bilayer cavity where the emission from a nanostructured layer containing the luminescent material is trapped in a low refractive index layer, achieving a large drop of reabsorption events probability.…”

Recent Developments in Solar Energy-Harvesting Technologies for Building Integration and Distributed Energy Generation

“…The benefits of adding photonic mirrors to LSC structure and their effects on the optical transport phenomena within concentrators are reported in [99]. Other groups also concentrate on the development of various types of backreflector coatings, including Lambertian backreflectors [100], to improve the device PCE through enhanced partial trapping of light.…”