Article

High-Efficiency Organic Solar Concentrators for Photovoltaics

Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science (Impact Factor: 33.61). 08/2008; 321(5886):226-8. DOI: 10.1126/science.1158342
Source: PubMed

ABSTRACT

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 interest in LSCs has increased in the last few years, due to improved stability of luminescent dyes [4], the introduction of quantum dots and nanorods [5] and the overall reported increase in module efficiency [6] [7] [8]. In recent papers [9] [10] the most recent results in LCS development and characterization were described. "
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    ABSTRACT: Luminescent solar concentrators (LSCs) have been proposed in the 1970s as cheap planar concentrators for residential applications and nowadays represent a novel idea with excellent perspectives for building integration photovoltaics. The interest in LSCs has increased in the last years, due to improved stability of luminescent dyes, the introduction of quantum dots and nanorods and the overall reported increase in module efficiency. Computational methods have been suddenly applied as an important tool for the description of light dynamics in LSCs. With "ray-tracing methods" light is described as particle-like (photons) and each particle is tracked. It is precious tool for the description of absorption/re-emission events, refraction and internal reflection in LSCs. It is also a very useful approach for the description of LSC edge effects, which may be well described by means of basic geometrical optics and are the subject of this work. The impact of scattering layers on the backside of LSCs is analysed in detail both experimentally and computationally. Results give evidence of the non-wavelength dependent impact of backside diffusers to the external quantum efficiency of LSCs and thus to their overall performance. A possible design of LSC as smart windows in photovoltaic façades is also suggested, where the benefits of the edge effects described are taken into account.
    Full-text · Article · Jan 2016
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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 [3] [4] [5] [6] [7]. 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 [8] [9] [10] [11] [12] [13]. 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 [14]. "
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    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.
    Full-text · Article · Jan 2016 · Solar Energy Materials and Solar Cells
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    • "Besides this potential to boost the output performance of solar cells, LSCs can promote the integration of PV components into buildings [11] [12], for example as photovoltaic windows that would transform energy-passive building façades into large-area energy generation units [6] [13], solar harvesting urban furniture, allowing electronic devices charging [14] or, even, as wearable solar harvesting fabrics, such as backpacks, for mobile energy [15]. Different optically active centers have been tested in LSCs, including organic dyes [9] [16] [17], quantum dots (QDs) [18] [19] [20] and trivalent lanthanide (Ln 3 þ ) ions [21] [22] [23] [24] [25] [26]. 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 [27]) and negligible self-absorption (quantified by the self-absorption efficiency, η SA $ 1). "
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    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.
    Full-text · Article · Jul 2015 · Solar Energy Materials and Solar Cells
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