The cost of photovoltaic power can be reduced with organic solar concentrators. These are planar waveguides with a thin-film organic coating on the face and inorganic solar cells attached to the edges. Light is absorbed by the coating and reemitted into waveguide modes for collection by the solar cells. We report single- and tandem-waveguide organic solar concentrators with quantum efficiencies exceeding 50% and projected power conversion efficiencies as high as 6.8%. The exploitation of near-field energy transfer, solid-state solvation, and phosphorescence enables 10-fold increases in the power obtained from photovoltaic cells, without the need for solar tracking.
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"The side surface emission of a LSC can be collected via an aperture in an integrating sphere while the illuminated front surface remains outside the integrating sphere     . If the whole sample is placed within the integrating sphere, one can determine the optical efficiency by selectively blocking the side surface emission using a black tape or marker      . Side surface emissions can also be measured using a fiber with a cosine corrector as a probe that is held against the respective side surface . "
[Show abstract][Hide abstract] ABSTRACT: A novel experimental method is presented to determine the optical efficiency and the loss channels of a luminescent solar concentrator (LSC). Despite strong promise, LSCs have not yet reached their full potential due to various mechanisms affecting the device's optical efficiency. Among those loss channels, escape cone and non-unity quantum yield losses are generally the most dominant. To further advance the field of LSCs, it is vital to understand the impact of each independently. So far, researchers have only characterized the total loss in LSCs. Here, an experimental method is proposed to separate the contribution from each individual loss channel. The experimental apparatus is the same as used for quantum yield measurements of fluorophores in solid samples. Therefore, the setup is commonly available to research groups already involved in LSC research. The accuracy of this method is demonstrated by comparing the experimental results with Monte-Carlo ray tracing. Our experimental method can have a strong impact on LSC research as it offers a means to unveil the loss channels of LSCs in addition to the optical efficiency.
Solar Energy Materials and Solar Cells 01/2016; 144:40 - 47. DOI:10.1016/j.solmat.2015.08.008 · 5.34 Impact Factor
"Besides this potential to boost the output performance of solar cells, LSCs can promote the integration of PV components into buildings  , for example as photovoltaic windows that would transform energy-passive building façades into large-area energy generation units  , solar harvesting urban furniture, allowing electronic devices charging  or, even, as wearable solar harvesting fabrics, such as backpacks, for mobile energy . Different optically active centers have been tested in LSCs, including organic dyes   , quantum dots (QDs)    and trivalent lanthanide (Ln 3 þ ) ions      . In the past decade, Ln 3 þ based materials have been considered good candidates for application in LSCs due to an appropriate balance between relatively high emission quantum yield values (η yield 40.30 ) and negligible self-absorption (quantified by the self-absorption efficiency, η SA $ 1). "
[Show abstract][Hide abstract] ABSTRACT: Here we present a new concept on lightweight and mechanically flexible high-performance waveguiding photovoltaics through the fabrication of cylindrical luminescent solar concentrators (LSCs) of commercial poly(methyl methacrylate)-based plastic optical fibers coated with an Eu3+-doped organic–inorganic hybrid layer. Our optimized fiber LSC displays an effective optical conversion efficiency of 20.7±1.3% and a power conversion efficiency of 2.5±0.2% in the absorbing spectral region of the active layer (300–380 nm), values that are among the larger ones reported so far for UV-absorbing devices. Moreover, the measured optical conversion efficiency was used to calculate the self-absorption and transport efficiencies of the LSCs yielding values close to the unit. Conventional LSCs are usually made of rigid glass or plastics with limited flexibility, hampering its applicability. The approach proposed here might then open new opportunities for cost-effective sunlight collection and wearable solar-harvesting fabrics for mobile energy with negligible self-absorption and transport losses.
Solar Energy Materials and Solar Cells 07/2015; 138. DOI:10.1016/j.solmat.2015.02.032 · 5.34 Impact Factor
"These dyes also have significant overlap between their absorption and emission spectrum resulting in re-absorption losses2. Second-generation dyes based on quantum dots or semiconductor nanorods34, inorganic phosphors5, and chromophores in light-emitting diodes6 are promising materials for LSCs due to their large Stokes shifts which result in lower reabsorption but they generally exhibit reduced fluorescence quantum yields compared to first-generation dyes. These materials also suffer from concentration quenching effects, which limit the concentration of the dyes that can be used to achieve high film absorption. "
[Show abstract][Hide abstract] ABSTRACT: The photophysical properties of fluorescent dyes are key determinants in the performance of luminescent solar concentrators (LSCs). First-generation dyes - coumarin, perylenes, and rhodamines - used in LSCs suffer from both concentration quenching in the solid-state and small Stokes shifts which limit the current LSC efficiencies to below theoretical limits. Here we show that fluorophores that exhibit aggregation-induced emission (AIE) are promising materials for LSC applications. Experiments and Monte Carlo simulations show that the optical quantum efficiencies of LSCs with AIE fluorophores are at least comparable to those of LSCs with first-generation dyes as the active materials even without the use of any optical accessories to enhance the trapping efficiency of the LSCs. Our results demonstrate that AIE fluorophores can potentially solve some key limiting properties of first-generation LSC dyes.