Abstract
Developing means to reduce the cost of solar energy is vital to curb our carbon footprint over the upcoming decades. A luminescent solar concentrator (LSC) is a potential solution as it provides light concentration without any tracking device and can be readily integrated into the built environment. In this study we report on an advanced LSC design that employs quantum dots as absorption fluorophores and organic dye molecules as emission fluorophores. By linking the two types of fluorophores to each other, energy is transferred efficiently via Förster resonance energy transfer (FRET) from the quantum dot to the dye molecule. This novel method makes use of the quantum dot's spectrally wide absorption profile and the higher quantum yield of the dye. We show that our design can overcome the losses normally incurred due to a low quantum yield emitter by transferring the absorbed energy to a linked fluorophore with a higher quantum yield. Our experimental measurements show FRET can enhance the optical efficiency of a LSC by at least 24.7%. The maximum theoretical efficiency has been investigated by ray-tracing and has been found to be 75.1%; this represents a relative improvement of even 215.5% compared to a LSC doped with quantum dots only (23.8%), showing the great potential of our concept. Our design will initiate interest in fluorophores which have not been considered for LSC applications thus far because of their low quantum yield or small Stokes shift.
Highlights
Luminescent solar concentrators (LSCs) were invented in the late 70s to reduce the cost of solar energy by concentrating the incident sunlight, [1,2,3]
LSCs have struggled to make a strong impact on solar energy due to the following shortcomings: (1) fluorophores will lose some of the absorbed energy to heat due to a non-unity quantum yield, (2) depending on the direction of emission, the photons could be lost via the escape cone, (3) commonly used fluorophores have a spectrally narrow absorption band, and (4) overlapping absorption and emission spectra cause emitted photons to be re-absorbed exacerbating shortcomings (1) and (2)
This work is only a proof-of-concept though; we have shown using ray-tracing simulations that internal optical efficiencies of up to 75.1% can be reached with our advanced design which results in an improvement of 215.5% compared to a LSC doped with quantum dots only
Summary
Luminescent solar concentrators (LSCs) were invented in the late 70s to reduce the cost of solar energy by concentrating the incident sunlight, [1,2,3]. Photons are trapped within the host to reach the thin side surfaces which have solar cells adhered to This reduces the need for costly solar cell material and makes expensive tracking systems redundant as direct and diffuse light is absorbed by LSCs. This reduces the need for costly solar cell material and makes expensive tracking systems redundant as direct and diffuse light is absorbed by LSCs Despite their great potential, LSCs have struggled to make a strong impact on solar energy due to the following shortcomings (see Fig. 1a): (1) fluorophores will lose some of the absorbed energy to heat due to a non-unity quantum yield, (2) depending on the direction of emission, the photons could be lost via the escape cone, (3) commonly used fluorophores have a spectrally narrow absorption band, and (4) overlapping absorption and emission spectra cause emitted photons to be re-absorbed exacerbating shortcomings (1) and (2). An additional concern for LSC researchers is the photostability of the fluorophores to make them suitable for long-term outdoor applications, [4,5,6,7]
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