WO2015077836A1 - Solar concentrator - Google Patents

Abstract

There are provided luminescent solar concentrators comprising photoluminescent chromophores which exhibit aggregation induced emission (AIE). The solar concentrators find use in the concentration of solar energy and may be coupled to a photovoltaic device to generate solar power.

Description

SOLAR CONCENTRATOR

FIELD

[001] Luminescent solar concentrators comprising photoluminescent chromophores are disclosed. The sola concentrators find advantageous application in the concentration of solar energy.

BACKGROUND

[002] Integrating photovoltaics into building infrastructures is the next key step towards wide-scale implementation of solar technologies. However, there remain issues with the broader use of soiar cells, particularly in urban areas where the amount of light incident on the cell can be restricted compared to open spaces due to cloud shading or light scattering by local flora. One of the strategies to circumvent this problem is to use light concentrating systems such as parabolic mirrors and solar trackers. These concentrators, albeit effective in concentrating light, are rather bulky for integration in an urban locale and expensive due to the associated electrical and mechanical components required for solar tracking. Furthermore, such concentrators can heat the solar ceils, which can accelerate performance degradation.

£003] Luminescent soiar concentrators (LSCs) rely on the absorption of solar light by highly luminescent materials embedded in glass or plastic substrates. Subsequent waveguiding of emission to the thin edges of the substrate concentrates the luminescence which can, in principle, be used to improve the output of photovoltaic devices. The simple device configuration of LSCs means photovoltaics can be integrated into urban environments, such as windows and walls, at low cost. Currently, factors limiting LSC efficiency include reduced fluorescence quantum yield in the solid state arising from dye aggregation and reabsorption of dye emission (i.e. due to a small Stokes shift). Commercial laser dyes such as rhodamines, coumarms, and perylenes have been used for LSCs. A common feature of such dyes is their highly planar conjugated structure, which is conducive to the formation of non-emissive aggregates particularly at the high concentration required for total light absorption. Consequently, the fluorescence quantum yield of these dyes in the solid state is much lower than that measured in solution. These dyes also have significant overlap between thei absorption and emission spectral bands resulting in reabsorption losses.

[004] Twisted aromatic structures have been proposed for use in a number of applications such as in light-emitting devices and as bioprobes. This class of aromatic compounds has interesting fluorescence properties - emission is greatly enhanced in the solid state compared to the compounds in solution. This fluorescence behavior is widely referred to as aggregation induced emission (AIE). However, enhancement of chromophore emission does not only occur in the solid state, but also when dispersed in a polymer matrix or in frozen solution. St has been proposed these conditions block the non-radiative decay pathway due to intramolecular rotation and channel the excitation energy towards fluorescence.

[005] Clearly, the energy separation between absorptio and emission is crucial to have an effective device. The energy difference between absorption and emission should be well separated to avoid reabsorption, which effectivel isolates the concentrated photons from the dyes on the waveguide. [006] Derivatives of perylene (perylene diimides, pery!enebisimidazoles (perinones), and (iso)violanthrones} are the most prominent dyes used in LSC due to their well-known strong fluorescence, good photostability, and broad absorption and emission. Particularly, a number of derivatives of perylene diimides have been synthesized to improve solubility. While monomeric species of perylene diimides are known to have significant overlap between absorption and emission spectra, excimeric species of perylene diimides have been shown to have significant energy separation between absorption and emission [H, Yoo, J. Yang, A. Yousef, M R. Wasielewski, D. Kim, J. Am. C em. Soc 2010, 132, 3939-3944]. This bathochromic shift allows well-separated absorption and emission bands, which is particularly useful for LSC. However, depending on the supramoiecuiar organization of the perylen dyes, solid-state fluorescenc may or may not be observed. Specifically, H-type aggregates of perylene diimides typically have very low fluorescence in the solid state compared to solution or even none at all [F. Wurtliner, T. E. Kaiser, C. R, Saha- oller, Angew. Chem, Int. Ed 2011 , 50, 3376-3410].

^'[007] Several approaches have been used to solve the reabsorption problem. Solid-state solvation using polar and highly mobile material as a dopant in the polymer matrices alters the electronic states of the fluorescent molecules, which increases the Stokes shift and reduces the absorption and emission overlap. Combined with energy tunneling via Forsfer resonance energy transfer (FRET) and usage of triplet energy states of phosphorescent active molecules, reabsorption can be reduced significantly [M. J. Currie, J. K. Mapel, T. D. Heidel, S. Goffri, . A. Baldo, Science 2008, 321, 226-228]. Cascade energy funneling in dendrimers have also been used to reduce reabsorpfion in LSC devices [0. Altan Bozdemir, S. Erbas-Gakmak, O. 0. Ekiz, A. Dana, E. U. Akkaya, Angew. C em Int. Ed, 2011 , 50, 10907-10912]. In all of these cases, while the absorption and emission maxima are wefi separated, there is still exists a significant overlap between the absorption and emission spectral bands, which can stiil lead to reabsorption.

008] Aggregation-induced emission (A IE) chromophores have been used in light- emitting diodes [Z. Chang, Y. Jiang, B. He, J. Chen, Z. Yang, P. Lu, H. S. Kwok, Z, Zhao, H. Qiu, B. Z. Tang, Chem. Commun. 2013, 49, 594-598] and bioprobes [D, Ding, K. Li, B, Liu, B. Z. Tang, Acc. Chem. Res. 2013. doi:10.1021/ar3003464],

J009J To date, AIE chromophores have not been used in luminescent solar concentrators or as spectral conversion materials.

£0010] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

SUMMARY

[0011] in one aspect there is provided a luminescent solar concentrator (LSC) comprising one or more photo luminescent chromophores wherein the one or more photoluminescent chromophores exhibit aggregation induced emission. By aggregation induced emission (AIE) it is meant that the one or more photolurninescent chromophores exhibits enhanced fluorescence in the solid state compared to in solution.

[0012] An advantage of the photolurninescent chromophores is that they exhibit high solid state fluorescence. In particular, the fluorescence quantum yield of the chromophores is enhanced in solid state compared to in solution. This property is advantageous in luminescent solar converters comprising chromophores as a single material or in high concentrations.

[0013] The one or more photolurninescent chromophores may exhibit an absorption maximum between 250 rim and 1300 nm and an emission maximum between 350 nm and 1300 nm.

[0014] Another advantageous feature of the aforementioned chromophores is that they may exhibit significant Stokes shift. This may result in significant separation between the absorption and fluorescence maxima, such that there is little or no overlap of the absorption and fluorescence spectral bands for these compounds. This minimizes the re-absorption losses when these materials are used in LSCs.

[0015] The one or more photolurninescent chromophores may exhibit less than 20% overlap between absorption and emission spectral bands, or less than 10% overlap, or less than 5% overlap, or less than 3% overlap, or less than 1 % overlap.

[0016] The LSCs may comprise a waveguide which is capable of directing light to a suitable energy collection device, for example a photovoltaic device.

[0017] The one or more photolurninescent chromophores may be embedded or doped in the structure of the waveguide. The waveguide may comprise a matrix, such as a polymer matrix, wherein the photoluminescent ehromophores may be doped therein.

[0018] The one or more photoluminescent ehromophores may be present as or within a coating on the waveguide. Exemplary coatings include, but are not limited to, polymer coatings.

[0019] A key advantage of ehromophores that exhibit aggregation induced emission is that very high concentrations may be employed without losing the efficiency of the ehromophores. Accordingly thinner LSCs may be envisaged. Such thinner LSCs may provide flexible solar concentrator devices.

[0020] As noted hereinbefore, the phenomenon of enhanced fluorescence in solid state compared to solution may be referred to as aggregation induced emission (AIE). Compounds that exhibit AIE behaviour can have a range of molecular structures including aryiethenes, aryiethynes, arylamines, biary!s, siloles, phospholes and organometallic complexes with aryi ligands [Y. Hong, J, W. Y, Lam, B. 2. Tang, Chem, Soc, Rev. 2011 , 40, 5361-5388]. Nearly all of these compounds have aryl components that can freely rotate in solution. This leads to reduction in f luorescence as excitation energy is lost to molecular motion, if the rotation of the aryl groups is restricted, fluorescence is enhanced as energy is not lost to the rotational motion. Methods to restrict the molecular motion include aggregation of molecules in solution, lowering temperature and using the material in solid state.

[0021] The one or more photoluminescent ehromophores may possess structural features that enable aggregation-induced emission behaviour (i.e. enhanced emission in solid state). This may also be referred to a rigidification induced emission (RIE). These chromophores may have substituents that are ab!e to freely rotate in solution and the rotation is restricted in the solid state.

[0022] In solution, free rotation uses energy leading to low fluorescence. In the solid state, rotation is restricted and the energy is 'channelled' to fluorescence decay.

[0023] The one or more photoluminescent chromophores may comprise one or more optionally substituted aryfethenes, optionally substituted arylethynes, optionally substituted arylamines, optionally substituted biaryis, optionall substituted heteroarenes, optionally substituted siloles, optionally substituted phospholes, optionally substituted acrylonitriles or the photoluminescent chromophores may comprise organometallic compounds comprising one or more optionally substituted aryl or optionally substituted heteroaryl iigands.

[0024] The one or more photoluminescent chromophores may comprise one or more benzothiadiazole, benzooxodiazole, benzoselenodiazo!e, benzobisthiadiazo!e, thiadiazoloquinoxaline, pyrazmoquinoxaline, thiophene, thiazole, oxazoSe, phenothiazine, phenoxazine or carbazole moieties an of which may be optionally substituted.

[002S] The optional substituents may impart solubility to the chromophores in organic solvents. The optional substituents may be linear or branched atkyl groups. The optional substituents may be Ci to C30 linear or branched alkyl groups. The optional substituents may be Ci to C10 linear or branched alkyl groups or Ci to C₈ linear or branched alkyl groups or C₂ to C₈ linear or branched alkyl groups or C₄ to C« linear or branched alkyl groups [0026] One or more of the photoiuminescent chromophores may comprise one or more optionally substituted arylethenes or optionally substituted biaryls. Non-limiting examples include tetrapheny!ethene. tetraarylanthraquinodimethane, tetraarylpentaquinodimethane, phenylbianthraquinodimethane, and hexaphenyl butadiene.

[0027] An combination of the herein disclosed photoiuminescent chromophores may be employed in the luminescent solar concentrator.

[0020] Any one of the herein disclosed photolumtnescent chromophores may be donor chromophores.

[0029] The luminescent solar concentrator may comprise any one or more of the above disclosed photoiuminescent chromophores and an acceptor dye. The acceptor dye may be a high quantum yield acceptor dye.

[0030] The acceptor dye may be 4-(dfcyanomefhylene}-2-terf-buty!-6-

(1 ,1 ,7, 7-tetrameth yl ju lol idyl - 9-enyl) - 4H-py ran .

[0031] One or more of the photoiuminescent chromophores may comprise one or more acrylonitriles optionaily substituted with one or more optionally substituted aryl groups. The optionally substituted aryl groups may be optionally substituted phenyl groups. The optional substftuenis on the phenyl groups may be aryiamino groups.

[0032] The chromophore may be triphenylacrylonitrile or triphenylacrylonitrile having one or more of the phenyl groups optionally substituted. The chromophore may be 2-{4-(diphenylamino)phenyl)-3,3-diphenyiacfyionitrile. The acceptor dye may be 4-{dicyanomethylene)-2-teit-butyi-6-(1 ,1 ,7,7-tetramethyijuloltdyl-9-enyl}- 4H-pyran. [0033] The luminescent solar concentrator may comprise an acceptor dye in an amount of less than 5% by weight relative to the total weight of photoiuminescent chromophore and acceptor dye, or an amount less than 3% by weight, or an amount less than 2% by weight.

[0034] The luminescent solar concentrator may comprise any one or more of the herein disclosed photoiuminescent chromophores with the proviso that the chromophore is not 2-(4-(dfphenyiamino)phenyi)-3,3-diphenylacry!onitrile.

[0035] The luminescent solar concentrator may comprise any one or more of the herein disclosed photoiuminescent chromophores with the proviso that the chromophore is not 2-(4-{dtphenylamino)phenyl)-3,3-diphenylacry!onitrile and the acceptor dye is not 4-(dicyanomethylene)-2-fert-butyl-6-(1 ,1 ,7,7- tetramethyljuloiidyl~9-enyl)-4H-pyran.

[0036] The aforementioned optional substituents may be selected from any combination of alkyl, alkenyt, alkynyL carbocyciyi, aryl, heterocyclyl, heteroaryl, acyl, ara!kyl, alkaryl, alkheterocyciy!, a!kheteroaryl, aikcarbocyciyi, halo, haloalky!, haloalken l, haloalkyny!, haloaryl, halocarbocyclyl, haloheterocyclyL ha!oheteroaryl, naloacyl, haioaryalkyl, hydroxy, hydroxyaikyi, hydroxyaikenyl, hydroxyaikynyl, hydroxycarbocyclyl, hydroxyaryl, hydroxyheterocyclyl, hydroxyheteroaryl, hydroxyacyl, hydroxyaralkyl, alkoxyalkyi, alkoxyaikenyl, alkoxyalkynyl, alkoxycarbocyc! l, aikoxyaryl, aikoxyheterocyciyl, alkoxyheteroaryl, alkoxyacyl, alkoxyaraikyl, aikoxy, alkenyloxy, aikynyloxy, aryloxy, carbocyclyloxy, ara!kyloxy, heteroaryloxy, heterocyclyloxy, acyloxy, haioalkoxy, ha!oalkenyioxy, haloalkynyloxy, haloaryloxy, haiocarbocyclyloxy, haloaralky!oxy, ha!oheteroaryloxy, haloheterocyciyioxy, ha!oacyioxy, nitro, nitroalkyi, nitroa!kenyl, nitroaikynyl, nitroaryl, nitroheterocyciyi, niiroheteroayf. nitrocarbocyc!y!, nitroacyl, nitroaralkyl, amino (NH2), aikylamino, diaikylamino, alkenylamino, alkynylamino, arylamino, diarylamino, aralkylamino, diaraikyiamino, acy!amino, diacylamino, heterocyciami.no, heteroaryiamino, carboxy, carboxyester, amido, alkyisulphonyloxy, arylsulphenyloxy, alkylsulphenyl, aryisu!phenyl, t io, a!kyithio, alkenylthio, alkynylthio, arylthio, aralkyithio, carboeyclyithio, heterocyclylthio, heteroarylthio. aeylthio, sulfoxide, sulfonyl, sulfonamide, aminoa!kyl, aminoalkenyl, aminoalkynyf, amlnocarboeyclyi, aminoaryl, ami oheterocyclyl, aminoheteroaryi, aminoacy!, aminoaralkyi, thioalkyl, thioaikenyl, thioalkynyi, thiocarbocyclyl, thioaryl, thioheterocyeiyi, thioheteroaryl, thioacyl, thioara!kyt, earboxyaikyl, carboxyalkeny!, carboxyalkyny!, earboxycarbocycly!, carboxyaryl, carboxyheterocyclyi, earboxyheteroaryl, carboxyacyi, carboxyara!kyl, carboxyesteralkyl, carboxyesteratkenyl, carboxyesteralkynyl, carboxyestercarbocycl l, carboxyesteraryl, carboxyesterheterocyclyl, carboxyesterheteroaryl, carboxyesteraeyl, carboxyesteraraikyl, amidoalkyl, amidoalkenyl, amidoalkynyi, amidocarboeyclyi, amidoaryl, amidoheterocycl l, amidoheteroaryl, amidoacyi, amidoaraikyl, formylalkyl, formy!aikenyl, formylaikynyl, formylcarbocyclyl, formylaryi. formyiheterocyc!y!, formylheteroaryl, formylacyl, formylaralkyl, acylalkyl, acylaikenyl, acylalRynyl, acy!carboeyclyl, acylaryt, acylheterocyclyl, acylheteroaryl, acylacy!, acyiara!ky!, sulfoxide alky I, sulfoxidealkenyt, sulfoxsdealkynyl, sulfoxidecarbocyclyl, sulfo idearyl, sulfoxideheterocyclyl, suifoxideheteroaryi, sulfoxideacyl, sulfoxidearalkyl, sulfonylalkyl, sulfonylalkenyl, sulfonylalkyny!, sulfony!carbocyciyl, sulfonylaryl, sulfonylheterocyclyl, suifonyiheteroaryl, suifonyiacyl, sulfonylara!k l, sulfonamidoalkyl, suifonamidoa!kenyi, suifonamidoalkynyl, sulfonamidocarboeyclyl, sulfonamidoaryl, sulfonamidoheterocyelyl, sulfonamidoheteroaryl, sutfonamidoacyl, sulfonamidoaralkyl, nitroa!kyL nitroalkenyl, nitroal.kynyi, nitrocarbocyclyl, nitroaryl, nitro.heterocycfyl, nitroheteroaryl, nitroacyl, nitroaralkyl, cyano, sulfate and phosphate groups.

[0037] The luminescent^' solar concentrator may comprise any one or more of the aforementioned features in any combination.

[0038] There is further provided a solar concentrator as hereinbefore described wherein the solar concentrator is coupled to a photovoltaic device for energy conversion. In some embodiments the photovoltaic device is a solar ceil.

[0039] There is yet further provided a spectrum converter comprising one or more photoluminescent chromophores as hereinbefore described wherein the one or more photoluminescent chromophores exhibit aggregation induced emission.

[0040] In another aspect there is provided a skylight or light well comprising one or more photoluminescent chromophores as hereinbefore described wherein the one or more photoluminescent chromophores exhibit aggregation induced emission, in some embodiments according to this aspect the skylight or light well comprises a fibre optic system. In alternate embodiments the skylight or light well may be flexible.

[0041] In another aspect there is provided a use of a skylight or tight well as hereinbefore described in tunnelling light.

[0042] In another aspect there is provided a use of a solar concentrator as hereinbefore described in the concentration of solar energy. [0043] In another aspect there is provided a use of a sofar concentrator as hereinbefore described coupled to a photovoltaic device in the generation of solar power.

[0044] In another aspect ther is provided a photovoltaic device comprising a soiar concentrator as hereinbefore described.

[0045] As noted above an advantageous feature of the AIE materials is the fact that they show enhanced fluorescence quantum yields in the solid state. This overcomes the significant problem of current LSG dyes, which must be used at low concentrations typically dispersed in a polymer matrix to prevent aggregation induced quenching of fluorescence. An additional advantage of the ehromophores disclosed in the present application is their relatively large Stokes shift which reduces parasitic reabsorption resulting in increased optical output in the LSC devices.

[0046] Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

BRIEF DESCRIPTION OF FIGURES

Figure 1 : Illustrates structures of twisted and contorted aromatics with propellerlike phenyl rings used in the present disclosure.

Figure 2; illustrates crystal structures of (a) chrornophore 2 and (b) chromophore 4. Figure 3: Illustrates the absorption spectra and photoluminescence (PL) spectra of chromophores 1 (top) and 5 (bottom) as neat films.

Figure 4: Illustrates the temperature dependence of the fluorescence spectra for chromophores 1 and 5.

Figure 5: Illustrates the performance characteristics of an LSC device including: Experimental OQE spectra of LSCs (G==2.5) using chromophore 1 (a) and 5 (b); modelled LSC output using chromophore 1 as active fluorescent material as a function of geometric factor (c); IPCE spectra of actual LSC (G=6) using chromophore 1 as the active fluorescent material and quartz as substrate (25 mm x 25 mm x 1 mm) when coupled to a reference silicon solar cell; and IPCE spectra of blank quartz measured as a control (d).

Figure 6: Illustrates the structures of DPATPAN and DGJTB.

DETAILED DESCRIPTION

£0047] It will now be convenient to further describe the disclosure with reference to particular embodiments and examples. These embodiments and examples are illustrative only and should not be construed as limiting upon the scope of the disclosure. It will be understood that variations upon the described disclosure as would be apparent to the skilled artisan are within the scope of the disclosure. Similarly, the present disclosure is capable of finding appiication in areas that are not explicitly recited i this document and the fact that some applications are not specifically described should not be considered as a limitation on the overall applicability of the disclosure.

|0048] Further, before the present compounds, components, compositions, devices, and/or methods are disclosed and described, it is to be understood that unless otherwise indicated this disclosure is not limited to specific compounds, components, compositions, reactants, reaction conditions, Iigands, structures, devices, or the like, and as such may vary, unless otherwise specified. It is also to be understood that the terminology used herein is for th purpose of describing particular embodiments only and is not intended to be limiting.

[0049] It is noted thai, as used in the specification and the appended claims, the singular forms "a,^N "an" and "the" include plural referents unless otherwise specified. Thus, for exampie, reference to "a haiogen atom" as in a compound "substituted with a halogen atom" includes more than one halogen atom, such that the compound may be substituted with two or more halogen atoms, reference to "a substituent" includes one or more substituents, reference to "a ligand" includes one or more Iigands, and the like.

[0050] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with an other upper limit to recite a range not explicitly recited.

[0051] In this specification "optionally substituted" is taken to mean that a group may or may not be substituted or fused (so as to form a condensed polycyclic group) with one, two, three or more of organic and inorganic groups (i.e. the optional substituent) including those selected from: alkyl, alkenyi, alkynyl, carbocyclyl, aryl, heterocyclyl, heteroaryl, acyl, aralkyl, aSkary!, alkheterocyclyl, alkheteroaryl, alkcarbocyclyl, halo, haioaikyl, haloalkenyl, haloalkynyl, haloaryl, haiocarbocyciyl. haloheterocyclyi, haioheteroaryl, haloacyi, haloaryalkyi, hydroxy, hydroxyalkyl, hydroxyalkenyi, hydroxyalkyny!, hydroxycarbocyclyl, hydroxyaryl, hydroxyheterocyclyl, hydroxyheteroaryl, hydroxyacyi, hydroxyaralkyf, alkoxya!ky!, alkoxyalkenyi, alkoxyalkynyl, a!koxycarbocyclyl, alkoxyaryi, aikoxyheterocyclyl, alkoxyheteroaryl, alkoxyacyl, aikoxyaraikyl, alkoxy. al enyloxy, alkyny!oxy, aryloxy, carbocyclyloxy, aralkyloxy, heteroaryloxy, heterocyciytoxy, acyloxy, haloalkoxy, haloalkenyloxy, halaalkynyloxy, haloaryloxy, halGcarbocyelyloxy, haioaralkyloxy, haloheteroaryloxy, haioheterocyclyloxy, haloacyloxy, nitro, nitroalkyl, nitroaikenyl, nitroa!kynyf, nitroaryl, nitroheterocyclyi, nitroheteroayl, nitrocarbocyclyl, nitroaeyl, nitroaraikyl, amino {NH2), aSkylamino, dtalkylamino, alkenylamino, alkynylamino, arylamtno, diary!amino, araikylamtno, diaralkylamino, acylamino, diacylamino, heteroeyclamino, heteroarylamino, carboxy, carboxyester, amido, alkyisulphonyloxy, arylsulphenyloxy, alkylsulphenyl, arylsulphenyl, thio, alkylthio, alkenylthio, alkynylthio, arylthio, aralkylthio, carboeyc!ylthio, heterocyciytthio, heteroarylthio, acylthio, sulfoxide, sulfonyl, sulfonamide, aminoalkyl. aminoaikenyi, aminoalkynyl, aminocarbocycl l, aminoaryl, aminoheterocyciyl, aminoheteroaryl, aminoacyl, aminoaralkyl, thioaikyl, thioalkenyl, thioatkynyl, thiocarbacyclyl, thioaryl, thioheterocycl l, thioheteroaryl, thioacyi, thioaralkyi, carboxyalkyi, carboxyalkenyl, carboxyaikynyl, carboxycarbocyclyl, carboxyaryl, carboxyheterocyclyl, carboxyheteroaryl, carboxyac l, carboxyaralkyl, carboxyesteralky!, carboxyesteralken l, carboxyesteralkynyl, carboxyestercarbocyciyl, earboxyesteraryl, carboxyesterheterocyciy I , carboxyesterheieroaryl , carboxyesteracyl , carboxyesteraralkyl, amidoalkyi, amidoalkenyl, amidoalkynyl, amidocarbocyclyl, amidoaryl, amidoheterocyc!yl, amidoheteroaryl, amidoacyl, amidoaralkyl, formyialkyl, formylalkenyi, formylalkynyi, formylcarbocyciyl, formylaryl, formyiheterocyclyl, formylheteroaryl, formyiacyi, formylaralkyi, acylalkyl, acyialkenyl, acylalkynyl, acylcarboeyciy!, acySaryl, aeyiheterocycly!, acyiheteroaryl, acylacyl, acyiaralkyl, suifoxkjealky!, suffoxidealkenyl, sulfoxideaikynyl, sulfoxideearbocyclyl, sulfoxidearyi, sulfoxideheterocyclyl, sulfoxideheteroaryl, sulfoxideacyl, sulfoxidearaikyl, sulfonyiaSkyi, suifonylalkenyl, sulfony!alkynyl, sulfonylcarbocyclyl, sulfony!aryl, suifonyiheterocyclyl, sulfonylheteroaryl, sulfonylacyi, sulfonylaraikyi, sulfonamidoalkyi, suifonamidoa!kenyl, sulfonamidoalkynyl, suifonamidocarbocyclyl, sulionamidoaryl, sulfonamidoheteroeyclyl, suKonamido eteroaryl, sulfonamidoacyl, sulfonamidoaratkyl, nitroaikyi, nitroaikenyl, nitroalkynyl, nitrocarbocyclyl, nitroaryl, nitroheterocyclyl, nitroheteroaryl, nitroacyi, nitroaralkyl, qyano, sulfate and phosphate groups.

£0052] Preferred optional substituents include alkyi, (e.g. C1-6 alky! such as methyl, ethyl, propyl, butyl, cyc!opropy!, eyclobufyl, cydopentyi or cyclohexyl), hydroxyalkyl (e.g. hydroxymethyi, hydroxyethyi, hydroxypropyl), alkoxyalkyl (e.g. methoxymethyl, methoxyethyl, methoxypropyl, ethoxymethyl, ethoxyethyl, ethoxypropyl etc) alkoxy (e.g. C1 -6 alkoxy such as methoxy, ethoxy, propoxy, butoxy, cyc!opropoxy, cyclobLftoxy), halo, trifluoromethyl, inchloramethyl, tribromomethyl, hydroxy, phenyl (which itself may be further substituted e.g., by C1 -6 alkyi, halo, hydroxy, hydraxyCI-6 alkyl, CI -6 alkoxy, haloC1-6alkyl, cyano, nitro OC(0)C1 -6 alkyl, and amino), benzyl (wherein benzyl itself may be further substituted e.g., by C1-6 alkyl, halo, hydroxy, hydroxyC1-6alkyl, G1 -6 alkoxy, haloCi-6 alkyl, cyano, nitro OG(0)C1 -8 alkyl, and amino), phenoxy (wherein phenyl itself may be further substituted e.g., by C1~6 alkyl, halo, hydroxy, hydroxyC1 -6 alkyl, C1 -6 aikoxy, haioC1~6 alkyl, cyano, nitro OC(0)G1~6 a!kyl, and amino), benzyloxy (wherein benzyl itself may be further substituted e.g., by C1 -6 alkyl, halo, hydroxy, hydroxyC -6 aikyl, C1 -6 aikoxy, hataC1-6 alkyl, cyano, nitro OC(0)C1-6 alkyl, and amino), amino, alkylamino (e.g. C1-6 alkyl, such as methylamino, ethylamino, propylamine etc), diaikyiamino (e.g. C1-6 alkyl, such as dimethylamino, diethylamide, dipropylamino), acylamino (e.g. NHC(0}CH3), phenylamino (wherein phenyl itseif may be further substituted e.g., by C1-6 alkyl, halo, hydroxy hydroxyCi-6 afkyl, CI -6 alkoxy, haloC1 -6 aikyl, cyano, nitro OC(0)C1-6 alkyl, and amino), nitro, formyl, --G{0)~alkyl (e.g. C1-6 alkyl, such as acetyl), 0-C(0)-alkyl (e.g. C1-6alkyl, such as acetyloxy), benzoyl (wherein the phenyl group itself may be further substituted e.g., by C1-6 aikyl, halo, hydroxy hydroxyC1 -6 alkyi, C1-6 aikoxy, haloC1 -6 alkyi, cyano, nitro OC(0)C1 -6a!kyl, and amino), replacement of CH2 with C=0, C02H, C02a!kyi (e.g. C1-6 alkyl such as methyl ester, ethyl ester, propyl ester, butyi ester), C02-phenyl (wherein phenyl itself may be further substituted e.g., by C1-6 aikyl, halo, hydroxy, hydroxy! C1 -6 alkyi, C1-6 aikoxy, halo G1-6 aikyl, cyano, nitro OC(0)C1-6 aikyl, and amino), GONH2, CONHphenyl (wherein phenyl itseif may be further substituted e.g., by G1 -8 alkyl, halo, hydroxy, hydroxy! C1 -6 alkyl, C1 -6 aikoxy, halo C1 -6 aikyl, cyano, nitro OC(0)Gl-8 alkyi, and amino), CONHbenzyl (wherein benzyl itself may be further substituted e.g., by CI -6 a!kyl, halo, hydroxy hydroxy! C -6 alkyl, G1-6 aikoxy, halo C1-6 aikyl, cyano, nitro OC(0)C1 -6 aikyl, and amino), CONHalkyI (e.g. C1 -6 alkyi such as methyl ester, ethyl ester, propyl ester, butyl amide) GGNBdialkyl (e.g. C1 -6 a!kyl)aminoa!kyi (e.g., HIM G1 -6 alkyl-, C1 - 6aikylHN~~C1 -6 alkyi- and (C1 -6 a!ky!)2N~~G1 -6 alkyl-), thioaikyl (e.g., HS C1 -6 alkyi-), carboxyalkyl (e.g., H02CC1 -8 alkyi-), carboxyesteralkyl (e.g., C1 -6 alkyi02CC1-8 alkyl-), amidoalkyi {e.g., H2N(0)CC1-6 alkyi-, H{C1 -6 alkyON(0)CC1 -6 alkyl-), formy!aikyl (e.g., OHCC1 -6alky!-), acylaikyl (e.g., C1 -6 alkyl{0)CC1 -6 alkyi-), nitroalkyi (e.g., 02NC1-6 alkyl-), suifoxidealkyl (e.g., R3(0)SC1 -6 alkyl, such as G1 -6 alky!(0)SC1-6 alky!-), suifonylalkyl (e.g., R3{0)2SC1 -6 alkyl- such as C1 -6 a!ky!(0)2SC1 -6 alkyl-), sulfonamidoalkyl (e.g., 2HRN(0)SC1 -6 alkyl, H(C1 -6 alkyi)N(0)SC1 -6 alky!-}.

[0053] As used herein, the term "aikyl", used eithe aione or in compound words denotes straight chain, branched or cyclic alkyl, for example C1 -40 alkyl, or Gt -20 or C1 -10. Examples of straight chain and branched alkyl include methyl, ethyl, n-propyl, isopropyi, n- butyl, sec-butyl, t-butyi, n-pentyl, n-hexyl, 1 ,2- dimethylpropyl, 1 ,1 -dimethyf-propy!, hexyS, 4~methylpentyi_! 1 -methylpenty!, 2- methylpentyl, 3-methy!pentyl, 1 ,1 -dimethy!butyl, 2,2-dimethylbutyl, 3,3- dimethylbutyi, 1 ,2-dimethylbutyl, 1 ,3-di methyl butyi, 1 ,2,2-trimethyipropyl, 1 ,1 ,2- trimethyipropyl, heptyl, 5-methylhexyf, i -methylhexyl, 2,2-dimethylpentyl, 3,3- dimethylpenty!, 4,4-dimethy!pentyl, 1 ,2-dimethylpentyl, 1 ,3-dimethylpentyl, 1 ,4- dimethyl-penty!, 1 ,2,3-trimethylbutyi, 1 , 1 ,2-tri meth l but l, 1 ,1 ,3-trimethylbutyl, octyl, 6-methylheptyl, 1-methylhep†y!, 1 ,1 ,3,3-tetramethyibuiyl, nonyl, 1 -, 2-, 3-, 4-, 5-, 6- or 7-methyloctyl, 1-, 2-, 3-, 4- or 5-ethylheptyl, 1 2- or 3-propyihexyl, decyl, 1 -, 2-. 3-, 4-, 5-, 6-, 7- and 8-methyinonyl, 1 -, 2-, 3-, 4-, 5- or 6-ethyloctyi, 1 -, 2-, 3- or 4-propylheptyl, dimethyloctyi, undecyl, 1 -, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9- methyldecyl, 1-, 2-, 3-, 4-, 5-, 6- or 7-ethyJ nonyl, 1 -, 2-, 3-, 4- or 5-propyloctyl, 1-, 2- or 3-butyiheptyl, 1 -peniylhexyi, dodecyf, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10- methylundecyi, 1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-ethyldecyl, 1-, 2-, 3-, 4-, 5- or 6- propyinonyl, 1 -, 2-, 3- or 4-butyloctyl, 1-2-penty!heptyi, tridecyl, tetradecyl, pentadecyi, hexadeeyl, heptadecyl, octadecyi, nonoadeeyl, eicosyl and the like. Examples of cyclic alkyl include mono- or polycyciic afkyl groups such as cyclopropy!, cyclobutyl, cyclopentyi, cyciohexyl, cycloheptyl, cyclooctyl, eyclononyl, cyciodecyl and the like. Where an alkyl group is referred to generally as "propyl", butyl" etc, it will be understood that this can refer to any of straight, branched and cyclic isomers where appropriate. An alkyl group ma be optionally substituted by one or more optional substituents as herein defined.

10054] As used herein, term "alkenyl" denotes groups formed from straight chain, branched or cyclic hydrocarbon residues containing at least one carbon to carbon double bond including ethylenicalSy mono-, di- or polyunsaturated alky! or cycloalkyi groups as previously defined, for example C2-4G alkenyl, or C2-20 or C2-10. Thus, alkenyl is intended to include propeny!, butytenyl, pentenyi, hexaenyl, heptaenyl, octaenyl, nonaenyl, decenyl, undecenyl, dodeceny!, tridecenyf, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nondecenyl, eicosenyl hydrocarbon groups with one or more carbon to carbon double bonds. Examples of alkenyl include vinyl, al!yi, 1-methylvinyl, butenyl, iso- butenyl, 3-methyl-2-buteny!, 1 -pentenyi, cyc!opentenyl, 1 -methyl -cycl ope ntenyl, 1 - hexenyl, 3-hexenyl, cycloriexenyl, 1-heptenyl, 3-heptenyl, 1-octenyt, cyclooctenyl, 1 -nonenyi, 2-nonenyl, 3-nonenyl, 1 -decenyl, 3-decenyS, 1 ,3-butadienyl, 1 ,4- pentadienyl, 1 ,3-cyclopentadienyl, 1 ,3-hexadienyl, 1,4-hexadienyl, 1 ,3- eyclohexadienyl, 1 ,4-cycSohexadienyi, 1 ,3-cycioheptadtenyl, 1 ,3,5- cyctoheptatrienyl and 1 ,3,5,7-cyciooctatetraenyt. An alkenyl group may be optionally substituted by one or more optional substituents as herein defined.

[0055] As used herein the term "aikynyl" denotes groups formed from straight chain, branched or cyclic hydrocarbon residues containing at least one carbon-carbon triple bond including ethylenically mono-, di- or polyunsaturated alkyl or cycloaikyl groups as previously defined, for example, C2-40 alkenyt, or C2-20 or C2-10. Thus, alkynyf is intended to include propynyl, butylynyl, pentynyl, hexaynyl, heptaynyl, octaynyl, nonaynyl, decynyi, undecynyl, dodecynyl, tridecynyl, tetradecynyl, pentadecynyi, hexadecyny!, heptadecynyl, octadecynyl, nondecynyi, eicosynyl hydrocarbon groups with one or more carbon to carbon triple bonds. Examples of aikynyl include ethynyl, 1 -propynyl, 2-propynyl, and butynyi isomers, and pentynyf isomers. An aikynyl grou may be optionally substituted by one or more optional substituents as herein defined.

£0056] An alkenyl group may comprise a carbon to carbon triple bond and an aikynyl group may comprise a carbon to carbon double bond (i.e. so called ene-yne or yne-ene groups).

{0057] As used herein, the term "aryi" (or ^Mearboaryl)^H denotes any of single, polynuclear, conjugated and fused residues of aromatic hydrocarbon ring systems. Examples of aryt include phenyl, bipheny!, terphenyl, quaterphenyl, naphthy!, tetrahydronaphthy!, anihracenyl, dihydroanthracenyl, benzanthracenyt, dibenzanthracenyl, phenanthrenyl, fluorenyl, pyrenyl, idenyl, azulenyl, chrysenyl. Preferred aryl include phenyl and naphthyf. An aryi group may be optionally substituted by one or more optional substituents as herein defined. [0058] As used herein, the terms "aikylene", "aikenylene", and "ary!ene" are intended to denote the divalent forms of "aikyl", "aikenyl", and "aryl", respectively, as herein defined.

[0059] The term "halogen" ("halo"} denotes fluorine, chlorine, bromine or iodine (fluoro, chloro, bromo or iodo).

[0060] The term "carbocyciyi" includes any of non-aromatic monocyclic, poiycyclic, fused or conjugated hydrocarbon residues, preferably C. 3-20 (e.g. C 3-1.0 or C3-8). The rings may be saturated, e.g. cye!oalkyl, or may possess one or more double bonds (cycloa!kenyl) and/or one or more triple bonds (cycloaikynyl). Particularly preferred carbocyciyi moieties are 5-6-membered or 9-10 membered ring systems. Suitable examples include cyclopropyi, cyeiobutyl, cyclopentyl, cyclohexyl, cyc!oheptyl, cyclooctyf, cyclononyl, cyeiodecyi, cyelopenten l, cyclohexenyl, cycloocteny!, cyclopentadienyl, cyclohexadienyl, cycSooctatetraenyl, indany!, decalinyl and indenyj.

[0061] The term "heterocyclyl" when used alone or in compound words includes any of monocyclic, poiycyclic, fused or conjugated hydrocarbon residues, preferably C3-20 (e.g. C3-10 or C3-B) wherein one or more carbon atoms are replaced by a heteroatom so as to provide a non-aromatic residue. Suitable heteroatoms include O, N, S, P and Se. particulariy O, N and S. Where two or more carbon atoms are replaced, this may be by two or more of the same heteroatom or by different heteroatoms. The heterocyclyl group may be saturated or partially unsaturated, i.e. possess one or more double bonds. Particulariy preferred heterocyclyl are 5-6 and 9-10 membered heterocyclyl. Suitable examples of heterocyclyl groups may inciude azridinyl, oxiranyl, thiiranyl, azetidinyl, oxetanyl, thietanyl, 2H-pyrroiyl, pyrroiidinyi, pyrrolinyl. piperidyl, piperazinyl, morphojinyl, indolinyl, tmtdazoiidinyi, imidazolinyl, pyrazolidinyl, thiomorpholinyl, dioxanyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydropyrrolyl, tetrahydrathiophenyl, pyrazolinyl, dioxa!anyi, thiazolidinyl, isoxazolidinyl, dihydropyranyl, oxazinyl, thiazinyi, thiomorpholinyl, oxathianyl, dithianyt, tnoxanyl, thiadiazinyl, dithiazinyl, trithianyl, azepinyl-, oxepinyl, thiepinyl, indenyl, indanyl, 3H~indolyl, isoindolinyl, 4H-qutno!azinyl, chromenyl, chromanyl, isochromanyl, pyranyl and dihydropyranyl.

[0062] The term "heteroary!" includes any of monocyclic, polycyc!ic, fused or conjugated hydrocarbon residues, wherein one or more carbon atoms are replaced by a heteroatom so as to provide an aromatic residue. Preferred heteroaryl have 3-20 ring atoms, e.g. 3-10. Particularly preferred heteroaryl are 5~ 6 and 9-10 membered foicyc!ic ring systems. Suitable heteroatoms include, O, N, S, P and Se, particularly O. N and S. Where two or more carbon atoms are replaced, this may be by two O more of the same heteroatom or by different heteroatoms. Suitable examples of heteroaryl groups may include pyridyL pyrrolyl, thienyl, imidazo!yf, furany!, benzothieny!, isobenzothienyl, benzofuranyl, isobenzofuranyl, indolyl, isoindolyl, pyrazolyS, pyraztnyl, pyrimidinyl, pyridazinyl, tndolizinyl, quinolyl, isoquinolyl, phthalazinyl, 1 ,5-naphthyridinyl, quinozalinyl, quinazolinyl, quinolinyl, oxazolyl, thia2olyl, isothiazolyi, isoxazolyl, triazoiyl, oxadialzolyl, oxatriazolyl, triazinyi, and furazanyi.

£0063] The term "acyl" either alone or in compound words denotes a group containing the agent C=0 (and not being a carboxylic acid, ester or amide) Preferred acyl includes C{0)-Rx, wherein Rx is hydrogen or an alky!, a!kenyl, alkynyi, aryl, heteroaryl, carbocyclyl, or heterocyclyl residue. Examples df acyl include formyl, straight chain or branched alkanoyl (e.g. 01 -20) su h as, acetyl, propanoyl, butanoyl, 2-methylpropanoyl, pentanoyl, 2,2-dimethylpropanoyL hexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyi, undecanoyl, dodecanoyl, tridecanoyl, tetradecanoyf, pentadecanoyi, hexadecanoyl, heptadecanoyl, oetadecanoyl, nonadecanoyl and icosanoyl; cycloalkylcarbonyl such as eyclopropyicarbonyl cycfobutylcarbonyi, cyciopentylcarbonyl and cyclohexylcarbonyr; aroyl such as benzoyl, toluoy! and naphthoyl; aralkanoyi such as phenylalkanoyl (e.g. pheny!acetyi, phenyipropanoyl, phenylbutanoyl, phenylisobutylyl, phenylpentanoyi and phenylhexanoyi) and naphthylatkanoyi (e.g. naphthylacetyl, naphthyfpropanoyi and naphthyibutanoyl]; aralkenoyl such as phenylalkenoyl (e.g. pheny!propenoyl, phenyibutenoyl, phenylmethacryioyl, phenylpentenoy] and phenylhexenoyl and naphthyialkenoyl (e.g. naphthyipropenoyl, naphthyibutenoyl and naphthylpentenoyl); aryioxyafkanoy! such as phenoxyacetyl and phenoxypropionyl; arylthiocarbamoyl such as phenylthiocarbamoyl; ary!g!yoxyioyl such as phenylglyoxyloyi and naphthyiglyoxyloyi; arylsulfonyl such as phenyjsulfonyl and napthyisulfonyl; heterocycliccarbonyl; heterocyclicalkanOyl such as thienylacetyl, thienylpropanoyl, thienylbutanoyi, thienyipentanoyl, thienyihexanoyi, thiazolylacetyl, thiadiazolylacetyl and tetrazolylacetyl; heterocyciicalkenoyt such as heterocyclicpropenoyl, heterocyclicbutenoyl, heterocyc!icpentenoyl and heterocyciichexenoyl; and heterocyciicgiyoxyloyl such as thiazolyg!yoxy!oyl and thienylglyoxyioyl. The Rx residue may be optionally substituted as described herein. [0064] The term "sulfoxide", either alone o in a compound word, refers to a group ~S(0)Ry wherein Ry is selected from hydrogen, alkyl, aikenyl, alkynyl, aryl, heteroaryl, heteroeyclyl, carbocyciyi, and aralkyi. Examples of preferred Ry include C1 -20alkyl, phenyl and benzyf,

[0065] The term "suifonyl", either alone or in a compound word, refers to a group S{Q)2--Ry, wherein Ry is selected from hydrogen, alkyl, aikenyl, alkynyl, aryl, heteroaryl, heteroeyclyl, carbocyciyi and aralkyi. Examples of preferred Ry include C1 -20alkyl, phenyl and benzyl.

[0066] The term "sulfonamide", either alone or in a compound word, refers to a group S(0)NRyRy wherein each Ry is independently selected from hydrogen, alkyl, aikenyl, alkynyl, aryl, heteroaryl, heteroeyclyl, carbocyciyi, and aralkyi. Examples of preferred Ry include C1-20alkyi, phenyl and benzyf. In a preferred embodiment at least one RY is hydrogen, in another form, both Ry are hydrogen.

[0067] The term, "amino" is used herein its broadest sense as understood in the art and includes groups of the formula NRARB wherein RA and RB may be any independently selected from hydrogen, alkyl, aikenyl, alkynyl, aryl, carbocyciyi, heteroaryl, heteracyclyl, aralkyi, and acy!. RA and RB, together with the nitrogen to which they are attached, may also form a monocyclic, or polycyciic ring system e.g. a 3-10 membered ring, particularly, 5-6 and 9-10 membered systems. Examples of "amino" include NH2, NHalkyf (e.g. Cl ^Oalkyl), NHaryl (e.g. Hphenyl), NHaralkyi {e.g. NHbenzyi), NHacyl (e.g. NHC(O}C1-20a!kyl, NHC{0)phenyl), Nafkylalkyl {wherein each alkyl, for example C1 -2G, may be the same or different) and 5 or 6 membered rings, optionally containing one or more same or different heteroatoms (e.g. O, and S).

[0068] The term "amido" is used here in its broadest sense as understood in the art and includes groups having the formula C{0}NRAR.sup,B, wherein RA and RB are as defined as above. Examples of amido include C(0)NH2, C(0)NHalky! (e.g. C1 ~2Qa!kyi), C{0)!MHaryi (e.g. C{Q)NHphenyi), C(0)NHaralkyt (e.g. C(O)NHbenzyl), C(0)NHacyi (e.g. C(O)NHC(O)Cl~20a!kyl, G(0}NHG(0)phenyl), C(G)Nalkyla!kyl (wherein each alkyl, for example C1-20, may be the same or different) and 5 or 6 membered rings, optionally containing one or more same or different heteroatoms (e.g. O, N and S).

[0069] The term "carboxy ester" is used here in its broadest sense as understood in the art and includes groups having the formula C02Rz, wherein Rz may be selected from groups including alkyl, alkenyl. alkynyl, ary!, carbocyclyl, heteroaryl, heterocyeiyl, aralkyl, and acy!. Examples of carboxy ester include CO2C1 -20alkyl, C02aryl (e.g. CG2phenyi), C02aralkyl (e.g. CG2 benzyl).

[0070] The term "heteroatom" or "hetera" as used herein in its broadest sense refers to any atom other than a carbon atom which ma be a member of a cyclic organic group. Particular examples of heteroatoms include nitrogen, oxygen, sulfur, phosphorous, boron, silicon, selenium and tellurium, more particularly nitrogen, oxygen and sulfur.

[0071] Tetraphenylethene (1) is a compound well known for its aggregation induced emission (AIE) (also referred to as rigidification induced emission (R..IE) behaviour (Figure 1 ). The quantum yield of 1 has been reported to increase as the molecule is rigidified, i.e. phenyl rotations are hindered thus favouring the radiative pathway [Y. Dong, J, W. Y. Lam, A. Qin, J. Liu, Z. Li, B. Z. Tang, J. Sun, H. S. Kwok, Appt. Phys. Lett 2007, 91, 011 11 1 -01 1 113]. In order to assess the potential of twisted and contorted aromatic compounds in LSC applications, a series of molecules with phenyl ethene moieties (1-5) were synthesised. The synthesis of all five compounds has been described previously in the literature [ . Banerjee, S. Emond. S. Lindeman, R. Rathore, J. Org. Chem. 2007, 72, 8054- 8061 ; S. Pola, C.-H. Kuo, W.-T, Peng, . M. Islam, I. Chao, Y.-T. Tao, Chem. Mater. 2012, 24, 2566-2571 ; Z, Zeng, Y. Sung, N. Bao, D. Tan, R. Lee, J, Zafra, B. Lee, M. Ishida, J. Ding, J. Lopez Navarrete, Y. Li, . Zeng, D. Kim, K.-W, Huang, R. Webster, J, Casado, J. Wu, J. Am. Chem, Sec. 2012, 134, 14513- 14525; G,-Y. Chiu, B, Kim, A. A. Gorodetsky, W. Sattler, S. Wei, A, Sattler, M. Steigerwald, C. Nuckolls, Chem. Sci. 2011 , 2, 1480-1486; T, Satoh, S. Ogino, M. Miura, M. Nomura, Angew. Chem. int. Ed. 2004, 43, 5063-5065]. Tetraarylanthraquinodimethane 2 and tetraarylpentaquinodimethane 4 are precursors to contorted benzocoronene materials [S. Pola, C.-H. Kuo, W.-T. Peng, . M. Islam, I. Chao, Y.-T. Tao, Chem. Mater. 2012, 24, 2566-2571 ; C.-Y. Chiu, B. Kim, A. A. Gorodetsky, W. Sattler, S. Wei, A. Sattler, . Steigerwald, C. Nuckolls, Chem. Sci. 2011 , 2, 1480-1486]. Phenylbianthraquinodimethane 3 was the subject of a recent study on Chichibabin's hydrocarbons jZ, Zeng, Y. Sung, N, Bao, D. Tan, R. Lee, J. Zafra, B. Lee, . Ishida, J. Ding, J. Lopez Navarrete, Y. Li, W. Zeng, D. Kim, K.-W. Huang, R. Webster, J. Casado, J. Wu, J, Am. Chem. Soc. 2012, 134, 14513-14525] and the butadiene 5 resulted from a synthetic methodology study on palladium-catalyzed arylation of alkynes [T. Satoh, S. Ogino, . Miura, . Nomura, Angew. Chem. int. Ed. 2004, 43, 5063-50653. ^Tne choice of fe/t-butyl groups on compounds 2. 3 and 4 is to maintain solubilit and solution processability of the materials (Figure 1). The full synthetic pathway of all described compounds have been discussed previously in references cited (vide supra),

[0072] The identity and purity of the compounds were confirmed by N R spectroscopy and mass spectrometry and the data were identical to previous reports. Single crystals, appropriate for X~ray diffraction studies, were grown from slow evaporation of dichloromefhane:isopropanol (1 :3) solutions for all five compounds. The crystal structures of compounds 2 and 4 were soived and are illustrated in Figure 2, while the structures of 1 [V. Dong, J. W. Y. Lam, A. Gin, J, Liu, Z, Li, B. Z. Tang, J. Sun, H. S. Kwok, Appl. Phys, Lett. 2007, 91, 011 11 1 - 01 1113], 3 [Z. Zeng, Y. Sung, N. Bao, D. Tan, R. Lee, J. Zafra, B. Lee, M. Ishida, J, Ding, J. Lopez Navarrete, Y. U, W. Zeng, D. Kim, K.-W. Huang, R. Webster, J. ■Casado, J. u, J. Am. Chem, Soc. 2012, 134, 14513-14525], and 5 J I . Satoh, S. Ogino, . Miura, . Nomura, Angew, Chem, Int. Ed, 2004, 43, 5063-5065] are already known. The structures of compounds 2 and 4 reveal butterfly-like motifs. The steric crowding between the freely rotating phenyl rings and either the anthraquinone ring (for 2) or pentaquinone ring (for 4) forces the polyaromatic backbone to bend out of p!anarity. Interestingly, compound 2 without the terf-butyi groups formed rod shaped crystals that suggest self-waveguiding fluorescence behaviour [Q. Zhao, S. Zhang, Y. Liu, J. ei, S. Chen, P. Lu, A. Qin, Y. Ma, J. 2. Sun, B. Z. Tang, J. Mater, Chem. 2012, 22, 7387-7394]. The photoluminescence (PL) emission (excitation from UV lam at 365 nm} is much more intense at the ends of the crystal rods due to the wavegutding effect. [0073] The photophysicaf properties of the compounds in solution and in solid state were examined using UV-vis and photoluminescence (PL) spectroscopy. The solution absorption spectra of all chromophores show broad absorption peaks with absorption maxima found in the UV region (Table 1 ). In thin films, there is a slight red shift (5-10 nm) for all chromophores with concomitant broadening. There is evidence of a considerable Stokes shift for all chromophores that minimizes reabsorption (Table 1 and Figure 3).

Table 1. Spectroscopic properties and performance characteristics in a LSC of chromophores 1 -5

Absorption Thin Fifm Thin Film Overall

rption SioJces Optical coefficient at Abso Fluorescence Quantum Light

Chromophore Shift Quantum yieid^M Trapping

[nm Efficiency⁶¹

|.>: KP tvi ^' cm^"1] [nm] [rim] Efficiency*

1 ,03 449 49.5% 60:5% 20.4%

310 139

(61,1%) {20.6%.)

2 1.90 314 493 9.9% 179 -

3 2.65 348 502 9.2 % 154 - -

4 6.42 301 455 4.1% 154 - -

5 1.55 55.8% 9.5%

307 405 31.2%

SB

(61.1%) (10.2%)

'Extinction coefficient measured in solution using dic iorornethane as solvent. Absorption maxima described here are the nearest maximum ak in the absorption spectra to the solar spectrum threshold in the UV region (-3Q0 nm}; "'Measured using an integrating sphere on quartz substrates (10 mm x 10 mm x 1 mm). Ali samples were excited at 320 nm; ^Wavelength difference between nearest solid state absorption and emission maxima; ^Experimental light trapping efficiency, defined as the ratio of edge emission to total emission, was measured using an integrating sphere. Theoretical Sight trapping efficiency (in parenthesis) of the full perimeter LSC was caiculated using Monte Carlo ray tracing modelling in MATLA8 (100,000 input photons)

optical quantum efficiency (OQE) at 320 nm was determined using art integrating sphere, Theoretical OQEs at 320 nm (in parenthesis) of the ful! perimeter LSC were calculated using Monte Carlo ray tracing modelling. [0074] The fluorescence of ail chromophores in solution at room temperature is very weak (Figure 4). Deposition of the compounds as neat films on quartz plates greatly enhanced their fluorescence indicating AIE behaviour. As discussed above, this type of fluorescence behaviour has been ascribed to rigidification of the freely rotating phenyl rings. To verify that the fluorescence enhancement of such chromophores is due to rigidity, fluorescence behaviour at cryogenic temperatures (80 K) was examined using 2- methyltetrahydrafuran as the solvent (Figure 4). Intensities of the PL spectra of the chromophores in Figure 4 were normalized relative to the maximum intensit at low temperature. Normalized PL spectra of the chromophores as thin films wer only added for comparison. The PL of the chromophores was activated at below the freezing point of the solvent (137 K). The frozen solvent formed a clear glass in which the chromophores are embedded. This restricted the free rotation of the phenyl groups in the chromophores and channelled the excitation energy towards fluorescence [Y. Hong, J. W. Y. Lam, B. 2, Tang, Chem. Commun. 200S, 4332- 4353].

{0075] The quantum yield of the neat film of the chromophores was measured using an integrating sphere (Table 1). The trends observed suggested that increasing the conjugated plane of the chromophore (as in 2, 3, and, 4} reduced the quantum yield. The pentaquinone derivative 4 has the largest planar aromatic unit out of the five compounds and the quantum yield was the lowest at 4.1% (Table 1 ). Increasing the number of freely rotating phenyl rings (as in 5) also did not improve the quantum yield relative to 1. Compounds 2, 3, and 4 with contorted moiecuiar structures showed noticeably brighter PL in their single crystal form compared to their neat amorphous films on quartz substrate. It is possible that in amorphous films opportunities for quenching can exist, perhaps by formation of singlet exciton traps or surface quenching [R, C. Powell, Z. G. Soos, . Lumin, 1975, 11, 1 -45].

[0076] Based on the quantum yield measurements, chromophores 1 and 5 were the best candidates for LSC applications. Simple LSG devices were fabricated by slowly evaporating a drop cast dichSoromethane solution (1 mg/mL) of the individual chromophores on a quartz substrate (10 mm ^χ 10 mm * 1 mm), Using an integrating sphere, the optical quantum efficienc (OQE) of the prototypical LSG was measured and calculated. OQE is a measure of the quantum efficiency of edge light output of the LSG device. The edge and face emission were differentiated using a black marker to block the edges of the quartz substrate. OQE is limited by the quantum yield of the chromophore and the trapping efficiency of the waveguide. Due to the limitations of the sample arrangement in the instrument used in the study, the experiment was limited to a geometric gain (G) of 2.5. Geometric gain is defined as the ratio of the surface area of the concentrator face to the surface area of the concentrator edge. The OQE spectra of the best candidate chromophores 1 and 5 are shown in Figure 5a and 5b, respectively.

[0077] Theoretical OQE of 1 {-50% quantum yield, ~73% theoretical trapping efficiency of quartz, and -67% absorption at 320 nm) is 24%. Theoretical modelling using Monte Carlo ray tracing [C. Haines, . Chen, K. P. Ghiggino, Sot. Energy Mater. SoL Cells 2012, 105, 287-292] predicted an OQE of 20.8%. In both cases, the experimental value is in good agreement with the theoretical approaches. The values obtained here are similar to the OQE obtained in LSCs utilizing aligned dyes with cascade Forster resonance energy transfe (FRET) to minimize reabsorption and maximize light trapped in the waveguide [A. Menendez-Velazquez, C. L, Mulder, N, d. Thompson, T, L. Andrew, P, D. Reusswig, C. Rotschild, M. A. Baldo, Energy Environ, Set. 2013, 6, 72-75]. For 5 (~30% quantum yield, -73% theoretical trapping efficiency of quartz, and ~40 absorption at 320 nm), the OQE is theoretically estimated to be 9% white Monte Carlo ray tracing modelling predicted an OQE of 7.5%, both of which are in good agreement to the experimental value.

[0078] The foregoing discussion and upon comparison to the best reported materials based on OQE jM d. Currie, J, K. Mapel, T. D. Heidel, S. Goffri, M. A. Baldo, Science 2008, 321, 226-228] suggest that there is no significant reabsorption losses occurring in the LSC containing compounds 1 and 5. Furthermore, the OQE values were limited b the fraction of absorbed photons. The film thickness of the compounds on quartz substrate was -100 nm thick whereas typical LSC devices have micrometer thick layers. It should be noted that the crystallinity of tetraphenylethene 1 , when deposited using techniques other than drop casting (vacuum deposition or spray coating) on quart2 to increase thickness, resulted in considerable light scattering from the films rendering the LSC translucent.

[0079] To confirm that A!E-type chromophores can be used in a LSC application, a LSC device using 1 as the active chromophore was coupled to a photovoltaic cell. A quartz substrate with dimensions of 25 mm x 25 mm x 1 mm (G=6) was used as the waveguide and mounted perpendicular to a silicon solar cell (Oriel Reference Cell , Newport, 2 cm x 2 cm active area). The incident photon conversion efficiency (IPCE) spectrum of the solar cell was obtained by irradiating through a monochromator with the fight focused on the centre of the LSC which was positioned 8,5 cm from the light source equating to a beam size of approximately 1 mm. The film thickness of chromophore 1 on the quartz slide was 150 nm and a blank quartz slide was used as a control. The spectral shape of the IPCE spectrum coincided with the absorption spectrum of 1 in thin films, which suggests that the enhanced sensitivity of the reference silicon solar celt arises from the LSC chromophore emission (Figure 5d). The control experiment with the blank quartz slide showed no measurable IPCE response. It should be noted that the LSC used in this study has not been optimized (i.e. no additional optics other than the waveguide, no scattering layers, no silver mirrors}.

[0080] The spectral conversion from the UV region to the visible region of the chromophores could potentially overcome the poor spectral sensitivity of solar cells towards high energy photons [X, Huang, S. Han, W. Huang, X. Liu, Ghem. Soc. Rev. 2013, 42, 173-201]. As a proof-of-principle experiment, a simple LSC with a film of tetraphenylethene 1 deposited on a quartz slide was coupled with a silicon photovoltaic cell. The spectral response of the device matched the absorption spectrum of 1. The simplicity of synthesis of the chromophores, an important criterion to enable industrial scale production with minima! cost, combined with atypical properties compared to common fluorescent organic dyes are advantages that can assist the further development of high-performance LSCs. [0081] In another example the photo!uminescent chromophore is the donor chromophore, 2~(4~{diphenylamino}phenyl)-3_!3-diphenylacrylonitrile (DPATPAN), which exhibits aggregation-induced emission (AIE) behaviour. DPATPAN, has properties typical of AIE materials - the fluorescence quantum yield of DPATPAN in the solid-state is 100% compared to 0.80% in tetrahydrofuran solution, In addition, DPATPAN exhibits a large Stokes shift with a small spectral overlap between absorption and emission.

[0082] DPATPAN may be used in conjunction with a high quantum yield acceptor dye such as 4-(d!cyanomethylene)-2-ieii-butyl-6-(1 ,1 ,7,7- tetramethyljuloiidyi-9-enyl)-4W-pyran (DCJTB) at low concentration. The chemical structures of these species are shown in Figure 6.

[0083] There are several key advantages for the DPATPAN-DCJTB system in comparison to the previously reported rubrene-DGJTB (M. J. Currie, J. K. apel, T. D. Heide!, S. Goffri and . A. Baido, Science, 2008, 321 , 226-228). Unlike rubrene, DPATPAN can be used in high concentration such that the distance between DPATPAN and DCJTB are within the energy transfer critical distance while concomitantly avoiding concentration quenching. In addition, it is noteworthy to mention that other EET systems not using AiE materials also have to compromise between FRET efficiency, quantum yield, reabsorption, and amount of light absorbed (B. Balaban, S. Doshay, M. Osborn, Y. Rodriguez and S. A. Carter, J, Lumin,, 2014, 146, 258-262; Y. Shen, Y. Jia, X. Sheng, L. Shen, J. A. Rogers and N, C. Giebink, ACS Photonics, 2014, 1 , 746-753), The spectral matching of DPATPAN wit DCJTB is better than rubrene. Rubrene has an absorption band that overlaps with the DCJTB absorption causing both rubrene and DCJTB to reabsorb emission from DCJTB (H. Mattoussi, H. Murata, C. D. Merritt, Y. lizumi, J. Kido and Z. H. Kafafi, J, Αβρί P y$„ 1999, 86, 2642-2650). !n order to make comparisons with the rubrene LSC system published previously, attempts were mad to fabricate rubrene/PMMA films (30% w/w rubrene in PMMA) from solution. However, rubrene seems to be unstable when solution processed in ambient conditions as the absorption spectrum of the dried rubrene/PMMA film did not show th typical absorption features of rubrene, which is possibly due to photo-oxidation of rubrene in air. DPATPAN, however, can be processed in air without any stability issues. Therefore AIE compounds may be used as light-harvesting donors in an EET-based LSC.

|0084] DCJTB/DPATPAN films on glass were prepared by dissolving the chromophores and the polymer matrix, poly{methyl methaeryiate) {PMMA, weight average molecular weight ~ 350 kg/mole), In chloroform followed by drop-casting on a glass substrate. The solvent was evaporated slowly in a covered Petri dish to increase the vapour pressure Of the solvent under ambient conditions (in air at 22 °C). PMMA films with DCJTB only were similarly prepared. Due to the large Stokes shift and insensitivtty to concentration quenching, it is possible to have a high concentration of the DPATPAN donor in PMMA for total light absorption while keeping the concentration of the DCJTB acceptor in PMMA at a minimum to reduce the fluorescence reabsorption. More importantly, the concentration of DPATPAN can be very high without sacrificing energy transfer efficiency in contrast to a previously reported EET system (Y, Shen, Y. Jia, X. Sheng, L Shen, J. A. Rogers and N. C. Giebink, ACS Photonics, 2014, 1 , 746-753). As a proof-of- principie, the weight ratio of donor and acceptor used to investigate both EET and LSC efficiencies was set to 1 :99 (w/w) to minimize the absorption contribution of DCJTB relative to DPATPAN. Efficient energy transfer was observed from DPATPAN to DCJTB when doped in PMMA. The estimated energy transfer efficiency based on the normalized absorption and normalized excitation spectrum of the EET pair when doped in PMMA (10% w/w) is 86%.

[0085] The optimized film biend ratio, based on the measured quantum yield, was 10% w/w of the dye blend (DCJTB: DPATPAN 1 :99} in PMMA (Φ_Ρ - 92 + 1 ,5%). The concentration of DCJTB relative to PMMA was kept at 0.1% (w/w) to prevent fluorescence quenching of this acceptor dye due to aggregation.

[0086] The A!E fluorophores can be used in combination with other dyes taking advantage of fluorescence resonance energy transfer (FRET). Further, light concentration at a more appropriate wavelength range for use with photovoltaic cells can be employed.

Claims

1. A luminescent solar concentrator comprising one or more photdluminescent chromophores wherein the one or more photoluminescent chromophores exhibit aggregation induced emission.

2. A solar concentrator according to claim 1 wherein the one or more photoluminescent chromophores exhibits a higher fluorescence quantum yield in the solid state compared to in solution.

3. A solar concentrator according to claim 1 or claim 2 wherein the one or more photoluminescent chromophores exhibits an absorption maximum between 250 nm and 1300 nm and an emission maximum between 350 nm and 1300 nm.

4. A solar concentrator according to any one of claims 1 to 3 wherein the one or more photoluminescent chromophores exhibits less than 20% overlap between absorption and emission spectral bands, preferably less than 10% overlap, more preferably less than 5% overlap, most preferably less than 3% overlap, even more preferably less than 1% overlap.

5. A solar concentrator according to any one of claims 1 to 4 wherein the one or more photoluminescent chromophores contains subsiituents that are able to freely rotate in solution, said substituents having restricted rotation in the solid state.

6. A solar concentrator according to any one of claims 1 to 5 wherein the one or more photoluminescent chromophores comprises one or more optionally substituted arylethenes, ary!ethynes, arylamines, biaryls, heteroarenes, silofes, phospholes, acrylonitriles or wherein the photoluminescent chromophore comprises org an o metal lie compounds comprising one or more optionally substituted aryl or heteroaryl ligands.

7. A solar concentrator according to claim 8 wherein the one or more photoluminescent chromophores comprises one or more optionally substituted arylethenes or biaryls.

8. A solar concentrator according to claim 6 wherein the one o more photoluminescent chromophores comprises one or more optionally substituted acrylonitriles.

9. A solar concentrator according to claim 8 wherein the one or more photoluminescent chromophores comprises one or more acrylonitriles substituted with one or more optionally substituted phenyl groups.

10. A solar concentrator according to any one of claims 1 to 5 wherein the one or more photoluminescen† chromophores comprises one or more optionally substituted benzothiadiazole, benzooxodiazoie, benzoselenodiazole, benzobisthiadiazole, thiadiazoloquinoxafine, pyrazinoquinoxaiine, thiophene, thiazole, oxazole, phenothiazine, phenoxazine or carbazole moieties.

1 1 . A solar concentrator according to any one of claims 1 to 10 wherein the photoluminescent chromophore is a dono chromophore,

12. A solar concentrator according to claim 1 1 further comprising an acceptor dye.

13. A solar concentrator according to claim 12 wherein the acceptor dye is present in an amount of less than 5% by weight relative to the total weight of photoluminescent chromophore and acceptor dye, preferably in an amount less than 3% by weight.

14. A solar concentrator according to any one of claims 1 to 13 comprising a waveguide which is capable of directing light to a suitable energy collection device.

15. A soiar concentrator according to claim 14 wherein the one or more photoluminescent chromophores are doped or embedded in the structure of the waveguide.

16. A soiar concentrator according to claim 14 wherein the one or more photoluminescent chromophores are present as or within a coating on the waveguide.

17. A solar concentrator according to any one of claims 1 to 16 wherein the solar concentrator is flexible.

18. A solar concentrator according to any one of claim 1 to 17 further coupled to a photovoltaic device for energy conversion.

19. Use of a solar concentrator according to any one of claims 1 to 18 for the concentration of solar energy.

20. Use of a solar concentrator according to any one of claims 1 to 18 coupled to a photovoltaic device for the generation of solar power.

21 . A photovoltaic device comprising a solar concentrator according to any one of claims 1 to 18.