High-Efficiency Luminescent Solar Concentrators for Photovoltaic Applications

Citation

Needell, David Robert (2022) High-Efficiency Luminescent Solar Concentrators for Photovoltaic Applications. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/5r7z-zd88. https://resolver.caltech.edu/CaltechTHESIS:10072021-154010065

Abstract

Despite an overwhelming abundance of crude solar energy, current photovoltaic systems worldwide harness less than 1% of this available power. As such, emerging solar generation technology must be developed to further spur global adoption -- whereby increased sunlight to power conversion efficiency alongside decreased system costs constitute the primary methods to accomplish this goal. The luminescent solar concentrator (LSC) offers a unique approach to collecting and redirecting large areas of incident light onto small-area solar cells. Relying upon photoluminescent materials (i.e., luminophores) suspended within a dielectric waveguide, the LSC absorbs high energy irradiance and re-emits photons at down-shifted energies into optical waveguide modes.

This thesis presents analytical, computational, and experimental work to illustrate the technical power conversion efficiency limits for LSC-based photovoltaic devices. We begin with a technical description of two LSC numerical models -- a stochastic Monte Carlo ray-trace and a deterministic closed-form approach. We apply these models to quantify the effects of system and component parameters on power conversion efficiency for a number of end-use applications. To validate our modeling and unveil current practical material limits, we fabricate CdSe/CdS and CuInS₂/ZnS core/shell quantum dot waveguides hosting embedded InGaP and GaAs photovoltaic cells, respectively. From these measurements, we observe close model-to-experiment matching and report a world-record LSC power conversion efficiency reaching approximately 10% under 1-sun illumination at modest incident to outgoing radiance areas.

Herein we consider four distinct applications for the LSC: (i) single junction LSC devices for terrestrial-based energy generation, (ii) building-integrated LSC form factors for on-site electricity, (iii) multijunction LSC modules for utility-scale installations at high power conversion efficiency, and (iv) ultra-light structures for on-board power in aerospace settings. We organize each chapter according to its end-use application.

Thesis Files