Patterned dye structures limit reabsorption in luminescent solar concentrators

Tsoi, Shufen; Broer, Dirk J.; Bastiaansen, Cees W. M.; Debije, Michael G.

doi:10.1364/oe.18.00a536

Cited by 42 publications

(29 citation statements)

References 17 publications

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“…A freestanding film that did not contain SPA did not show any change in volume after exposure to light. Furthermore, a film that contained a non-photochromic commercial dye instead of SPA showed a similar absorption spectrum (K160, l max = 450 nm) [23] and did not shrink upon light illumination. This behaviour indicates that the shrinkage of the SPA hydrogels is not a result of absorbed light, which is transferred into heat, but rather is related to the photoresponsive change in the hydrophobicity of the spiropyran dye.…”

Section: Resultsmentioning

confidence: 98%

Photoswitchable Hydrogel Surface Topographies by Polymerisation‐Induced Diffusion

Stumpel

Liu

Broer

et al. 2013

Chemistry A European J

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Herein, we describe the preparation of patterned photoresponsive hydrogels by using a facile method. This polymer-network hydrogel coating consists of N-isopropylacrylamide (NIPAAM), cross-linking agent tripropylene glycol diacrylate (TPGDA), and a new photochromic spiropyran monoacrylate. In a pre-study, a linear NIPAAM copolymer (without TPGDA) that contained the spiropyran dye was synthesised, which showed relatively fast photoswitching behaviour. Subsequently, the photopolymerisation of a similar monomer mixture that included TPGDA afforded freestanding hydrogel polymer networks. The light-induced isomerisation of protonated merocyanine into neutral spiropyran under slightly acidic conditions resulted in macroscopic changes in the hydrophilicity of the entire polymer film, that is, shrinkage of the hydrogel. The degree of shrinkage could be controlled by changing the chemical composition of the acrylate mixture. After these pre-studies, a hydrogel film with spatially modulated cross-link density was fabricated through polymerisation-induced diffusion, by using a patterned photomask. The resulting smooth patterned hydrogel coating swelled in slightly acidic media and the swelling was higher in the regions with lower cross-linking densities, thus yielding a corrugated surface. Upon exposure to visible light, the surface topography flattened again, thus showing that a hydrogel coating could be created, the topography of which could be controlled by light irradiation.

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Section: Resultsmentioning

confidence: 98%

Photoswitchable Hydrogel Surface Topographies by Polymerisation‐Induced Diffusion

Stumpel

Liu

Broer

et al. 2013

Chemistry A European J

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“…Tsoi et al [22,23] demonstrated that patterning the luminophore on a clear waveguide can reduce the amount of re-absorption events. To investigate the influence of re-absorptions on our previous measurements, we determined the impact of adding cholesteric reflectors to patterned LSCs.…”

Section: Resultsmentioning

confidence: 99%

Increased efficiency of luminescent solar concentrators after application of organic wavelength selective mirrors

Verbunt¹,

Tsoi²,

Debije³

et al. 2012

Opt. Express

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Organic wavelength-selective mirrors are used to reduce the loss of emitted photons through the surface of a luminescent solar concentrator (LSC). A theoretical calculation suggests that application of a 400 nm broad reflector on top of an LSC containing BASF Lumogen Red 305 as a luminophore can reflect 91% of all surface emitted photons back into the device. Used in this way, such broad reflectors could increase the edgeemission efficiency of the LSC by up to 66%. Similarly, 175 nm broad reflectors could increase efficiency up to 45%. Measurements demonstrate more limited effectiveness and dependency on the peak absorbance of the LSC. At higher absorbance, the increased number of internal re-absorption events reduces the effectiveness of the reflectors, leading to a maximum increase in LSC efficiency of ~5% for an LSC with a peak absorbance of 1. Reducing re-absorption by reducing dye concentration or the coverage of the luminophore coating results in an increase in LSC efficiency of up to 30% and 27%, respectively.

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“…Inspired by the approach reported for an LSC, 35 we propose to pattern the phosphor layer and place a remote After the forward flux is reflected by the remote reflector, the probability of the reflected flux crossing the phosphor layer can be made close to zero. Hence, the factor T ex α(λ,θ) approaches unity.…”

Section: B Numerical Examplementioning

confidence: 99%

“…The idea of patterning a phosphor layer has been studied for reducing self-absorption. 35 Waveguiding is also important in a different context: an LSC utilizes the PL photons trapped inside. Probability of trapping light has been modeled for both isotropic emission and electric dipole emission.…”

Section: Introductionmentioning

confidence: 99%

Angle-resolved photoluminescence spectrum of a uniform phosphor layer

Fujieda

Ohta

2017

AIP Advances

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A photoluminescence spectrum depends on an emission angle due to self-absorption in a phosphor material. Assuming isotropic initial emission and Lambert-Beer’s law, we have derived simple expressions for the angle-resolved spectra emerging from the top and bottom surfaces of a uniform phosphor layer. The transmittance of an excitation light through the phosphor layer can be regarded as a design parameter. For a strongly-absorbing phosphor layer, the forward flux is less intense and more red-shifted than the backward flux. The red-shift is enhanced as the emission direction deviates away from the plane normal. When we increase the transmittance, the backward flux decreases monotonically. The forward flux peaks at a certain transmittance value. The two fluxes become similar to each other for a weakly-absorbing phosphor layer. We have observed these behaviors in experiment. In a practical application, self-absorption decreases the efficiency of conversion and results in angle-dependent variations in chromaticity coordinates. A patterned phosphor layer with a secondary optical element such as a remote reflector alleviates these problems.

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Patterned dye structures limit reabsorption in luminescent solar concentrators

Cited by 42 publications

References 17 publications

Photoswitchable Hydrogel Surface Topographies by Polymerisation‐Induced Diffusion

Photoswitchable Hydrogel Surface Topographies by Polymerisation‐Induced Diffusion

Increased efficiency of luminescent solar concentrators after application of organic wavelength selective mirrors

Angle-resolved photoluminescence spectrum of a uniform phosphor layer

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