Abstract
The design, fabrication, and characterization of an upconversion-luminescence enhancer based on a two-dimensional plasmonic crystal are described. Full-wave finite-differ- ence time domain analysis was used for optimizing the geometrical parameters of the plasmonic crystal for maximum plasmon activity, as signified by minimum light reflection. The optimum design produced >20× enhancement in the average electromagnetic field intensity within a one- micron-thick dielectric film over the plasmonic crystal. The optimized plasmonic upconverter was fabricated and used to enhance the upconversion efficiency of sodium yttrium fluoride: 3% erbium, 17% ytterbium nanocrystals dispersed in a poly(methylmethcrylate) matrix. A thin film of the upconversion layer, 105 nm in thickness, was spin-coated on the surface of the plasmonic crystal, as well as on the surfaces of planar gold and bare glass, which were used as reference samples. Compared to the sample with a planar gold back reflector, the plasmonic crystal showed an enhancement of 3.3× for upconversion of 980-nm photons to 655-nm photons. The upconversion enhancement was 25.9× compared to the same coating on bare glass. An absorption model was developed to assess the viability of plasmonically enhanced upconversion for photovoltaic applications. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10
Highlights
Silicon (c-Si) is the most common material used in solar cells.[1,2] the energy produced from c-Si solar cells is expensive due to the high cost of ultrapure crystalline silicon and its medium power conversion efficiency
Thin-film inorganic solar cells based on amorphous Si,[3] cadmium telluride,[4,5] and copper indium gallium selenide,[6] and organic solar cells based on small-molecule organic dyes[7,8] and polymers[9] all exhibit a large absorption loss in the infrared spectrum as the absorption coefficient of the absorber layer vanishes beyond 800 to 900 nm
We recently demonstrated the feasibility of using engineered plasmonic surfaces to enhance NIR-to-visible upconversion luminescence from nanocrystalline systems.[35]
Summary
Silicon (c-Si) is the most common material used in solar cells.[1,2] the energy produced from c-Si solar cells is expensive due to the high cost of ultrapure crystalline silicon and its medium power conversion efficiency. Sodium yttrium fluoride (NaYF4) nanoparticles doped with erbium (Er) as the emitter and ytterbium (Yb) as the sensitizer is one of the most efficient upconversion materials reported to date.[11] Yb3þ ions absorb near-infrared (NIR) light at 980 nm and sequential energy-transfer events from Yb to Er excites visible Er emission at 665 and 540 nm. We recently demonstrated the feasibility of using engineered plasmonic surfaces to enhance NIR-to-visible upconversion luminescence from nanocrystalline systems.[35] The major focus of that paper was the synthesis of nanoparticles and characterization of two-photon upconversion enhancement due to an engineered plasmonic surface This approach is attractive because the use of engineered surfaces offers the possibility of much greater control over the location and distribution of local-field enhancement zones relative to plasmonic materials based on colloidal metal nanostructures. The methodology developed in this article to enhance upconversion efficiency through plasmonics can be expanded to wideband upconversion once new materials with efficient wideband upconversion properties are developed
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