A new class of multi‐bandgap high‐efficiency photovoltaics enabled by broadband diffractive optics. (9th June 2014)

• Record Type: Journal Article
• Authors: Wang, Peng; Dominguez‐Caballero, Jose A.; Friedman, Daniel J.; Menon, Rajesh
• Is Part Of: Progress in photovoltaics. Volume 23:Number 9(2015)
• Page Start: 1073
• Page End: 1079
• Publication Date: 2014-06-09
• Subjects: multi‐bandgap photovoltaics -- solar concentrator -- spectrum‐splitting -- diffractive optics -- microstructures; Solar cells -- Periodicals; Photovoltaic cells -- Periodicals; Solar power plants -- Periodicals; 621.31245
• DOI: 10.1002/pip.2516
• Languages: English
• ISSNs: 1062-7995

Abstract

Abstract: A semiconductor absorber with a single bandgap is unable to convert broadband sunlight into electricity efficiently. Photons with energy lower than the bandgap are not absorbed, whereas those with energy far higher than the bandgap lose energy via thermalization. In this Article, we demonstrate an approach to mitigate these losses via a thin, efficient broadband diffractive micro‐structured optic that not only spectrally separates incident light but also concentrates it onto multiple laterally separated single‐junction semiconductor absorbers. A fully integrated optoelectronic device model was applied in conjunction with a nonlinear optimization algorithm to design the optic. An experimental demonstration is presented for a dual‐bandgap design using GaInP and GaAs solar cells, where a 20% increase in the total electric power is measured compared with the same cells without the diffractive optic. Finally, we demonstrate that this framework of broadband diffractive optics allows us to independently design for the number of spectral bands and geometric concentration, thereby enabling a new class of multi‐bandgap photovoltaic devices with ultra‐high energy conversion efficiencies. Copyright © 2014 John Wiley & Sons, Ltd. Abstract : We designed, fabricated, and applied a micro‐optical element (polychromat) that spectrally separates and concentrates sunlight onto appropriate solar cells in order to enhance the overall photovoltaic efficiency. The polychromat operates with very high efficiency over the solar spectrum and can be manufactured inexpensively. Furthermore, our architecture offers enormous design freedom in the choice and sizes of the solar cells enabling entirely new applications of solar energy.