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Title:High efficiency luminescent solar concentrator with interconnected gallium indium phosphide micro solar cells
Author(s):Su, Hanxiao
Director of Research:Nuzzo, Ralph G
Doctoral Committee Chair(s):Nuzzo, Ralph G
Doctoral Committee Member(s):Abelson, John R; Braun, Paul V; Gewirth, Andrew A; Schleife, André
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Monte-Carlo ray tracing
luminescent solar concentrator
concentrator photovoltaics
Abstract:Photovoltaics (PV) technology is one of the most important sources of renewable energy due to its abundant availability, low cost, and compatibility with multiple production scales from residential to utility. As the efficiency of the traditional silicon photovoltaics approaches its theoretical limit, multi-junction (MJ) and concentrator photovoltaics (CPV) technology may open up new possibilities for further improvements. MJ technology improves efficiency by decreasing losses due to the mismatch between the energy of incident photons and the bandgap of semiconductors. GaInP is close to ideal in terms of bandgap in tandem with silicon. Due to its high cost of fabrication, the area of GaInP must be much smaller than Si in an economically viable GaInP//Si double-junction solar cell. A process of fabricating GaInP micro solar cells and integrating them into a sparsely populated 4×4 array is presented in this work. Using wet chemistry for metallization and III-V etching, the process has to potential to be scalable and low-cost. For light concentration, luminescent solar concentrator (LSC) is an attractive system due to its unique ability to harvest diffuse as well as direct sunlight, and to perform without a solar tracker. As a proof of concept, the outdoor performance of GaInP//Si tandem cell coupled with a quantum dot (QD)-polymer LSC was tested. Losses due to reflection off the short-pass filter was observed to outweigh efficiency gained from the GaInP array in the experiment. Loss mechanisms of the module were identified to be QD degradation, inefficient light trapping, unoptimized sizes, among other factors. A pathway to achieve 27.2% power conversion efficiency was proposed. Managing photon losses in LSCs is a considerable challenge as is evident from our outdoor test. The highest concentration factor achieved so far is several orders of magnitude lower than the thermodynamic limit, despite extensive research on improving individual components of an LSC including luminophore, short-pass filters, and metallic mirrors. In this work, Monte-Carlo ray tracing (MCRT) simulation is used to discover alternative designs that enhance waveguide ergodicity by geometry and scattering are proposed to improve LSC efficiency beyond what has been achieved. A model for identifying performance bottlenecks is also discussed. As MCRT results predict an optimal QD concentration that is not yet achievable with QD-polymer waveguides, a liquid waveguide for LSC applications is proposed and fabricated. The validity of MCRT-predicted ergodicity enhancement of LSC efficiency is verified with the liquid waveguide LSC.
Issue Date:2021-07-14
Rights Information:Copyright 2021 Hanxiao Su
Date Available in IDEALS:2022-01-12
Date Deposited:2021-08

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