Photovoltaic laminates with thiol-ENE polymers and inorganic nanoparticles

Abstract

The present disclosure relates to a method of manufacturing a polymeric laminate composition suitable for a photovoltaic element comprising, said polymeric laminate composition comprises off-stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles, wherein the method comprises performing a surface modification of provided luminescent nanoparticles resulting in the introduction of photopolymerizable functional groups on said provided luminescent nanoparticles, wherein the luminescent nanoparticles in the polymeric laminate composition having a surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer of 20-50%.

Description

[0001] PHOTOVOLTAIC LAMINATES WITH THIQL-ENE POLYMERS AND INORGANIC NANOPARTICLES

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to a method of manufacturing a polymeric laminate composition suitable for a photovoltaic device comprising off-stoichiometry thiol-ene polymer (OSTE) and surface modified luminescent nanoparticles. The present disclosure further relates to a photovoltaic device comprising a polymeric laminate composition manufactured according to said method.

[0004] BACKGROUND

[0005] Photovoltaic elements, that are able to convert light into electricity, have quickly become a common source for renewable energy. Traditionally, photovoltaic elements are provided in the form of dark colored, non-transparent panels to be placed either on top of buildings (for instance on roofs) or placed as individual elements on fields etc. As the technology behind photovoltaic elements evolves, the implementation and integration of these elements in more complex applications and structures has become of interest.

[0006] Integrated photovoltaic elements, i.e. where the photovoltaic elements are integrated into building envelopes, have become a promising field in order to reduce the carbon footprint of buildings. In theory, these integrated photovoltaic elements could either be integrated in the form of photovoltaic skins, i.e. walls, or glazing units, i.e. windows, resulting in a larger structural area of the building being used as a photovoltaic element.

[0007] Conventional photovoltaic elements have been used in limited coverage as windows in buildings due to their dark color and low transparency. If a photovoltaic element is to be used as a window, light transmittance of said elements becomes highly relevant for aesthetic and practical reasons.

[0008] Several solutions have been proposed to manufacture semi-transparent photovoltaic elements. One possibility is p-n junction photovoltaic element wherein the absorbing layer is made so thin so to not negatively affect the esthetical properties of the photovoltaic element. However, by reducing the thickness of the absorbing layer, the overall photovoltaic efficiency of the photovoltaic element is also reduced due to stronger role of the surface and interface defects.

[0009] Another proposed solution to manufacture semi-transparent photovoltaic elements is to create small openings in conventional photovoltaic elements. These openings are individually indistinguishable to the human eye, yet provide a general perception of semi-transparency. However, manufacturing of said small openings requires extensive clean room processing efforts which may not be suitable for practically relevant large area devices.

[0010] Another proposed solution is to utilize a luminescent solar concentration concept. In this case a slab doped with light converting fluorophores absorbs part of the solar light and emitted luminescence propagates by the total internal reflection to the edges for subsequent collection by standard solar cells. Organic dyes have been utilized for this application. These dyes are however not photostable, making them unsuitable for large scale production.

[0011] Composite structures comprising nanoparticles for this purpose are known. These can be made by a host matrix of acrylic polymers such as PMMA or PLMA. However, acrylic polymers usually exhibit a strong polymerization shrinkage, and, hence, do not provide good compatibility with glass structures. In that case a polymer slab needs to be inserted into an insulating glazing unit as a separate sheet, as opposed to an integrated glass laminate. When embedded into a polymer matrix, nanophosphor performance, such as luminescence quantum yield, usually deteriorates due to detrimental effects of surface chemistry and nanoparticle aggregation.

[0012] On the other hand, two component thiol-ene polymer laminates are compatible with glass due to their low polymerization shrinkage and favourable interface chemistry with hydroxyl groups on the glass surface. For these reasons thiol-ene polymers are employed for the fabrication of mechanically strong glass laminates, such as hurricane or bullet-proof glass.

[0013] Quantum dots have demonstrated promising properties as suitable fluorophores for solar windows due to their good stability, high photoluminescence quantum yield, and suppressed reabsorption loss by a large Stokes Shift. In particular, Si quantum dots have emerged as promising fluorophores for transparent photovoltaic devices due to their low toxicity, elemental abundance and large Stokes shift. A proposed solution is presented in Jing Huang, Jingjian Zhou, ErikJungstedt, Archana Samanta, Jan Linnros, Lars A. Berglund, and Ilya Sychugov, ACS Photonics 20229 (7), 2499- 2509. However, in the proposed solution, the layer thickness needs to be substantially reduced (concentration of quantum dots in the absorbing layer needs to be substantially increased) in order to achieve suitable transparency and haze values. As the photovoltaic efficiency is related to the amount of quantum dots present in the photovoltaic element, the proposed solution with a thick layer (10 mm) is limited in industrial applicability. In view of the above, there is a need for a photovoltaic device exhibiting suitable properties, i.e. high transparency / low haze and good photovoltaic properties, to be used as a building-integrated photovoltaic elements, such as a semi-transparent photovoltaic device in window applications, solving the problems of the prior-art solutions.

[0014] SUMMARY OF THE DISCLOSURE

[0015] The object of the present disclosure is to overcome the drawbacks of the prior art and present a method of manufacturing a polymeric laminate composition suitable for a photovoltaic device that not only provides improved transparency and haze values, but also improved photovoltaic and esthetical properties.

[0016] In a first aspect, the present disclosure relates to a method of manufacturing a polymeric laminate composition suitable for a photovoltaic element. The composition comprises off-stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles. The method comprises the steps of: a) providing luminescent nanoparticles in the form of noble metal nanoclusters, wherein said noble metal nanoclusters are selected from the group consisting of one or more of Au, Ag, Cu, Pd, Pt and a combination thereof, b) providing a thiol-functional monomer and an allyl-functional monomer, wherein said thiol-functional monomer and said allyl-functional monomer are provided in an off-stoichiometric amount, c) performing a surface modification of the provided luminescent nanoparticles of step a), resulting in the introduction of photopolymerizable functional groups on said provided luminescent nanoparticles, d) mixing the surface modified nanoparticles of step c) with the provided thiol- functional monomer and the allyl-functional monomer, e) exposing the mixture of step d) to UV light in order to induce thiol-ene photopolymerization and photopolymerization between the introduced photopolymerizable functional groups of step c) to thiol-ene polymer, thereby forming a polymeric laminate composition comprising off-stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles.

[0017] The method is characterized by step e) resulting in the luminescent nanoparticles in the polymeric laminate composition of step e) having a surface coverage of introduced photopolymerizable functional groups bonded to thiol-ene polymer of 20- 50%. Suitably, the surface coverage may be 25 - 50 %, 25 - 45%, 30 - 45 % or 30 - 40 %. The surface modification in step c) comprises reacting the noble metal nanoclusters with a thiol-containing ligand, by a wet-chemical method, thereby forming a ligand-noble metal nanocluster.

[0018] The surface modification performed in step c) of the provided luminescent nanoparticles in step a) introduces photopolymerizable functional groups to the surface of the provided luminescent nanoparticles. Said functional groups act as reactive sites in the photopolymerization performed in step e), wherein a photopolymerization between the introduced photopolymerizable functional groups on the surface modified nanoparticles of step c) and the provided thiol-functional monomer and an allyl-functional monomer occurs, thereby forming a polymeric laminate composition.

[0019] By a luminescent nanoparticle's surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer is meant the amount (given in %) of the luminescent nanoparticle's surface having bonds to thiol-ene polymer through the surface introduced photopolymerizable functional groups. A surface coverage of 0 % means a lack of bonds between the luminescent nanoparticles to the thiol-ene polymer. A surface coverage of 100% means that all the introduced photopolymerizable functional groups on the surface (at full surface coverage) of the luminescent nanoparticles have bonded to thiol-ene polymer.

[0020] It has surprisingly been discovered that the degree of surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer on the surface of the luminescent nanoparticles affects the properties of the resulting polymeric laminate composition suitable for a photovoltaic device. More precisely, it has been discovered that the surface coverage must be sufficiently high so to introduce a sufficient amount of reactive sites and hence improved photopolymerization. However, if the surface coverage is too low, the resulting photopolymerization may lead to agglomeration of the luminescent nanoparticles in the resulting polymeric laminate composition. Agglomeration will result in deteriorated visual characteristics of the composition and detrimental light conversion efficiency, and may make the composition unsuitable to be used as a photovoltaic element, such as in a semitransparent photovoltaic element in window applications. On the other hand, if the surface coverage is too high the light conversion efficiency may again deteriorate presumably due to non-passivated surface defect states.

[0021] As the reactivity between the provided luminescent nanoparticles to the provided thiol-functional monomer and the allyl-functional monomer is the key parameter for the resulting polymeric laminate composition's photovoltaic properties, it is possible to manufacture a polymeric laminate composition suitable for a photovoltaic device comprising a high concentration of luminescent nanoparticles with improved haze and thickness properties compared to the prior art. The higher the amount of luminescent nanoparticles within the polymeric laminate composition, the higher the photovoltaic properties (such as power conversion efficiency). However, the amount of luminescent particles is also directly correlated to increased haze of the resulting polymeric laminate composition.

[0022] The present disclosure allows for the manufacturing of a polymeric laminate composition suitable for a photovoltaic device comprising off-stoichiometry thiol-ene polymer (OSTE) comprising a high amount of luminescent nanoparticles while keeping haze sufficiently low to be suitable for usage in semi-transparent photovoltaic devices in window applications, solving the problems of the prior-art solutions.

[0023] Throughout the present disclosure, it is to be understood that by polymeric laminate composition is meant a polymeric composition suitable for producing a laminate, preferably a glass laminate. It could hence be described as a polymeric composition as well.

[0024] The surface coverage as defined above may be measured according to any suitable method depending on the provided luminescent nanoparticles in step a) known to the skilled person. For instance, if noble metal nanoclusters are provided in step a), the surface coverage may suitably be estimated by comparing the Stoke Shift of ligand surface modified noble metal nanoclusters mixed with an off-stoichiometric thiol-ene matrix monomer solution when subjected to a controlled UV-dose. The in- situ reaction of the ligand surface modified noble metal nanoclusters with the monomers is controlled by a UV-dose, i.e. bonding formation between ligand and thiol-ene polymer. Nanocluster emission and absorption spectra shift as a result of the reaction with the monomers, reflecting modified electronic structure of the nanoparticle. The resulting surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer may then be estimated by comparing the Stoke Shift for a specific timepoint over the total Stoke Shift when reaction is complete, i.e. when the emission / absorption spectra are no longer changing, or substantially not changing, with UV treatment reaching saturation (full surface coverage).

[0025] The surface modification is a wet-chemical reaction of the provided metal nanoclusters with a ligand to form a ligand-noble metal nanocluster.

[0026] The ligand may be an alkene chain with or without carbon double bond or carbonoxygen bond at the end, thiol-containing molecules, such as 1-adamanatanethiol, etc. By such a method, surface modification of the provided luminescent nanoparticles is achieved so that the reactivity of the surface modified luminescent nanoparticles is improved for the photopolymerization of step e).

[0027] Step e) may comprise applying 300 - 500 nm UV-light to the mixture of step d). Preferably 350-450 nm UV-light may be applied, even more preferably 350-400 nm UV-light.

[0028] The wavelength is selected so to start the photopolymerization reaction between the surface modified luminescent nanoparticles and the provided thiol-functional monomer and the allyl-functional monomer using a photoinitiatior. The photopolymerization takes place between the introduced photopolymerizable functional groups of step c) with the provided thiol-functional monomer and the allyl- functional monomer.

[0029] Said thiol-functional monomer may comprise 3 or more thiol groups per monomer. Further, said allyl-functional monomer may be an allyl amine monomer. In a preferred embodiment, said thiol-functional monomer may be pentaerythritol tetrakis (3-mercaptobutylate) and said allyl-functional monomer may be Triallyl- l,3,5-triazine-2,4,6(lH,3H,5H)-trione.

[0030] Said thiol-functional monomer may be pentaerythritol tetrakis [3- mercaptopropionate], trimethylolpropane tris [3-mercaptopropionate], TMXDI terra thiol, IPDI tetra thiol, HDI terra thiol, hexanedithiol, ethyleneglycol di-2- mercaptoacetate, pentaerythritol tetrakis(2-mercaptoacetate), trimethyolopropane tris(2-mercaptoacetate), ethyleneglycol di-3-mercaptoproprionate, or combinations thereof.

[0031] The thiol-functional monomer and said allyl-functional monomer may be provided in a molar ratio of 1:3. The thiol-functional monomer and said allyl-functional monomer may be provided in a molar ratio of 1:5 - 2:5, preferably around 2. The molar ratio is presented as the mole of thiol-functional monomer over the mole of allyl-functional monomer.

[0032] The method may further comprise the step of providing silicon nanospheres having a diameter of 100 - 200 nm to the mixture.

[0033] Silicon nanospheres act as resonant Mie scatterers for visible light wavelengths. Dispersing such complementary nanophosphors results in reflection of specific colors towards a color-neutral device preferred for esthetical reasons. The method may further comprise the step of providing Co+2doped ZnO nanoparticles with a diameter of 2 - 4 nm to the mixture of step d) as selective absorbers towards the same function. The diameter of the particles may be measured by TEM of AFM. The former uses transmission electron beam to image a dispersed nanoparticle solution on a carbon mesh with a sub-nm resolution, while the latter relies on the nanoparticle height measurements in a tapping mode with a sub-nm resolution.

[0034] The luminescent nanoparticles of step b) are noble metal nanoparticle selected from the group consisting of from one or more of Au, Ag, Cu, Pt, Pd and a combination thereof. Further, the surface modification in step c) comprises reacting the noble metal nanoparticle with a thiol-containing ligand, by a wet-chemical method, thereby forming a ligand-noble metal nanocluster, preferably the thiol-containing ligand may be 1-adamantanethiol.

[0035] The noble metal nanoparticle precursors are preferably provided as salts or acids, such as silver nitrate salt or a chloroauric acid (gold chlorate trihydrate).

[0036] Step e) may result in the noble metal nanoclusters in the polymeric laminate composition having a surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer of 30 - 50 %, preferably 25 - 35 %, as measured according to the present disclosure. As previously described, it has been discovered that the surface coverage must be sufficiently high so to introduce a sufficient amount of reactive sites and hence improved photopolymerization and light conversion efficiency, yet not too low to avoid agglomeration.

[0037] It has been discovered that the surface coverage (including polymer bonding) can be controlled by the post-processing UV-exposure of noble metal nanocluster during the photopolymerization. Optimum light conversion efficiency can be achieved by applying a controlled UV-dose for nanoclusters dispersed in a monomer mix. This is demonstrated in the examples of the present disclosure. With increased UV-exposure (leading to increased surface coverage) the efficiency drops, while the emission and absorption spectra keep changing, suggesting continuing surface passivation reaction until saturation (full surface coverage).

[0038] The method may further comprise the step of pouring the mixture of step d) to a glass mold before exposing the mixture to UV-light according to step e), thereby forming a composite structure wherein the mixture of step d) forms a middle layer sandwiched between two glass layers. The noble metal nanoclusters may be provided in an amount of 0.1 - 1 wt-% based on the total weight of the polymeric laminate composition, preferably of 0.2 - 0.6 wt- %, even more preferably of 0.25 wt% - 0.5 wt-%.

[0039] In a second aspect, the present disclosure relates to a photovoltaic device comprising a polymeric laminate composition manufactured according to any one of the first aspects.

[0040] In a further embodiment of the second aspect, the middle layer has a thickness of 0.5

[0041] - 5 mm and comprises 0.05 - 1 weight-% of luminescent nanoparticles, preferably 0.1

[0042] - 1 weight-% of luminescent nanoparticles. By luminescent nanoparticles is meant surface modified nanoparticles according to the present disclosure. Preferably wherein the middle layer has a thickness of 0.5 - 2 mm and comprises 0.25 - 1 weight-% of luminescent nanoparticles.

[0043] In a further embodiment of the second aspect, said photovoltaic device exhibits a visible light transparency of > 50%, haze of < 10% in the visible range, preferably less than 8, less than 7 or less than 5, and tunable colors, including a neutral color (color coordinates a* and b* is between -10 and 10).

[0044] In a further aspect of the present disclosure, the present disclosure relates to a polymeric laminate composition suitable for a photovoltaic device, said polymeric laminate composition comprises off-stoichiometry thiol-ene polymer (OSTE) and surface modified noble metal nanoclusters as luminescent nanoparticles. The polymeric laminate composition has a thickness of 0.5 - 5 mm and comprises 0.1 -1 weight-% of luminescent nanoparticles, preferably wherein the polymeric laminate composition has a thickness of 0.5 - 2 mm, a haze of < 10% in the visible range measured according to ASTM International D1003 "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" (ASTM D1003-00, 2000) and comprises 0.25-1 weight-% of luminescent nanoparticles, preferably 0.25 - 0.75 weight-%, even more preferably 0.25 - 0.5 weight%. The noble metal nanoclusters may be surface modified to introduce photopolymerizable functional groups on said provided luminescent nanoparticles. Said luminescent nanoparticles may be noble metal nanoclusters selected from the group consisting of one or more of Au, Ag, Cu, Pd, Pt and a combination thereof. Suitably, the noble metal nanoclusters may be surface modified by reacting the noble metal nanoclusters with a thiol-containing ligand, by a wet-chemical method, thereby forming a ligand-noble metal nanocluster, preferably the thiol-containing ligand 1 adamantanethiol. In one further aspect of the present disclosure, the above-mentioned polymeric laminate composite is manufactured according to any one method according to the first aspect.

[0045] The present disclosure also relates to yet a further aspect being a polymeric laminate composition suitable for a photovoltaic device, wherein a polymeric laminate composite is manufactured according to the method according to the first aspect, but wherein the luminescent nanoparticles are Si nanocrystal quantum dots instead. In such an aspect, the provided luminescent nanoparticles are Si nanocrystal quantum dots, it may be suitable to estimate the surface coverage by TGA after the surface modification. In that case a weight loss of a functionalized Si QD sample under annealing at temperatures below 900 °C is measured in TGA. This value, which corresponds to the amount of detached ligands, is then compared with an expected loss for a sample with a fully functionalized surface for a given nanoparticle size. The ratio between these two quantities represents the fraction of surface coverage for a given sample before nanocomposite fabrication. The surface coverage in this case represents the surface coverage degree of introduced photopolymerizable functional groups on the surface of the luminescent nanoparticle. These functional groups are able to photopolymerize at a later stage. Due to the amount of thiol-functional monomer and allyl-functional monomer introduced before photopolymerization, it is assumed that all surface introduced photopolymerizable functional groups will react

[0046] If Si nanocrystal quantum dots are provided, the surface modification may be thermal hydrosilylation of the provided Si nanocrystal quantum dots.

[0047] Said luminescent nanoparticles of step b) may be Si nanocrystal quantum dots. Further, the surface modification may in step c) comprise grafting an ester ligand to the surface of the Si nanocrystal quantum dots by a thermal hydrosilylation process. By such a method, an improved reactivity and dispersibility of the Si nanocrystal quantum dots in the thiol-ene polymer is achieved.

[0048] Step e) may result in Si nanocrystal quantum dots having a surface coverage of ester ligands bonded to thiol-ene polymer of 30 - 50%, more preferably of 30 - 40%. The surface coverage may in this case be measured by TGA as previously described.

[0049] The thermal hydrosilylation process may comprise the step of mixing the Si nanocrystal quantum dots with an ester solution in a ratio of 1ml ester : 10 mg of Si nanocrystal quantum dots. The thermal hydrosilylation process may comprise the step of mixing the Si nanocrystal quantum dots with an ester solution in a ratio of 0.5 - 3 ml ester : 5 - 20 mg of Si nanocrystal quantum dots, preferably 0.5 - 2 ml ester : 5 - 15 mg of Si nanocrystal quantum dots.

[0050] Providing an ester solution with a ratio of 1ml ester : 10 mg is an example of a hydrosilylation process according to the present disclosure.

[0051] The ester ligand may be methyl 10-undercenoate.

[0052] The method may further comprise washing the surface modified nanoparticles of step c) with an antisolvent before performing the mixing according to step d), wherein the volume ratio of ester ligand to antisolvent is or is about 1:4, preferably the antisolvent is hexane. Preferably, 2-3 washing cycles are performed.

[0053] It has been discovered that the surface coverage of the ester ligands on the surface of the Si nanocrystal quantum dots can be controlled by the ester ligand / antisolvent ratio and the number of washing cycles. A method according to the present disclosure allows for a surface coverage of the ester ligand on the Si nanocrystal quantum dots leading to improved reactivity in the subsequent photopolymerization, as has previously been described. The improved reactivity leads to a higher amount of Si nanocrystal quantum dots reacting with the thiol-functional monomer and the allyl-functional monomer, which in turns leads to the possibility to create a polymeric laminate composition comprising an increased concentration of Si QDs without effects on haze compared to the prior art. This will be further demonstrated in the examples of the present disclosure.

[0054] FIGURES

[0055] The disclosure will now be described in more detail with reference to the appended figures, wherein

[0056] Fig. la shows emission and absorption spectra of metal nanoclusters as a function of UV-treatment in a mixture with thiol-ene monomers.

[0057] Fig. lb shows quantum yield (PLQY) as a function of UV-treatment

[0058] Fig. 2 shows the relative power conversion efficiency values as a function of UV aging time.

[0059] DETAILED DESCRIPTION OF THE DISCLOSURE

[0060] In the following section, the present disclosure will be exemplified in more detail. By wt-% in the present disclosure, is meant weight percentage of a specific component's weight within a mixture or solution or composition, relative to the total weight of the mixture or solution or composition.

[0061] Example 1: Polymeric laminate composition comprising SI nanocrystal quantum dots (QDs).

[0062] One embodiment of a thiol-ene polymeric laminate composition with luminescent nanoparticles comprising Si nanocrystal quantum dots (QDs), which are 5-10 nm in diameter, is provided in Example 1. Si QDs can be synthesized by disproportionation reaction of silicon-rich solid precursors. Different non-stochiometric silica glass-like compounds can be selected for the precursor role, such as hydrogen silsesquioxane (HSQ), triethoxysilane (TES), trimethoxysilane (TMS) or trichlorosilane. The precursor powder (TES in this case) is annealed at 950°C for one hour to create Si QDs in glass matrix through phase separation. After release from the annealed matrix by hydrofluoric acid, Si QDs have hydrogen-terminated surface in a solution.

[0063] To increase the reactivity of the Si nanocrystal quantum dots with the OSTE matrix, ester ligands (methyl 10-undercenoate) are attached to the surface of Si QDs by thermal hydrosilylation process. Hydrogen-terminated Si QDs are mixed with a certain amount of ester solution (1 mL ester per 10 mg of Si QDs). Ultrasonic treatment is employed to the mixture until it becomes homogenous solution. Subsequently, the suspension is transferred to a flask, which then connects to an argon-filled Schlenk line to isolate from oxygen and moisture. The surface-capping reaction is kept at 150°C for 19 h. To extract Si QDs out from the ester solution, four times volume of hexane, is added, followed by centrifugation at 10000 RPM for 10 min. After 2-3 washing cycles the precipitate is collected for the subsequent dispersion to the polymer.

[0064] The surface coverage was measured by TGA. As previously described, a weight loss of a functionalized Si QD sample under annealing at temperatures below 900 degrees C is measured in TGA (most organic ligand detachment takes place between 300 and 600 degree C without any significant weight loss at higher temperatures for the remaining Si QD cores). This value, which corresponds to the amount of detached ligands, is then compared with an expected loss for a sample with a fully functionalized surface for a given nanoparticle size. The ratio between these two quantities represents the fraction of surface coverage for a given sample. For this example, the surface coverage was measured to 30-50%, with the main uncertainty coming from nanoparticle size distribution. Pentaerythritol tetrakis (3-mercaptobutylate) is used as thiol monomer and trial lyl- l,3,5-triazine-2,4,6 (lH,3H,5H)-trione as allyl monomer. Photo-initiator is 1- Hydroxycyclohexyl phenyl ketone (lrgacure-184). 0.02g of Si QDs are first dispersed in 0.96 g of allyl monomer in a glass vial by ultrasonication. 3.11 g thiol polymer and 0.04 g of photo-initiator are added to the clear orange solution above. This resulted in a mixture comprising 0.5 weight% of Si QDs, allowing for a thin polymer interlayer (0.5-1 mm thick). Compared to the prior art, the method of the present disclosure allows for the manufacture of thinner polymer interlayers while at the same time achieving a higher concentration of luminescent nanoparticles within the polymer interlayer.

[0065] After sufficient mix under ultrasonic and vortex, the solution is kept in an evacuated desiccator to remove the air bubbles inside. The homogeneous solution was poured into a prepared glass mold (made of low-iron borosilicate glass, 20x20x0.7 cm3or 30x30x0.7 cm3total volume) and cured with 360 nm UV light for 30 s to trigger the thiol-ene polymerization reaction. This resulted in a polymer layer sandwiched between two pieces of glass, the polymer layer having a thickness of 0.5-1 mm.

[0066] The resulting polymeric laminate composition exhibited a haze value of < 3% and was measured according to ASTM International D1003 "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" (ASTM D1003-00, 2000).

[0067] The photovoltaic performance of cured composition was measured as external quantum efficiency and power conversion efficiency values in a solar simulator (LEDbased 350 - 1100 nm spectral range, ASTM E927 class AAA+, 25x25 cm2spot size) as is shown in Table 1. Both devices were > 80% transparent for visible light).

[0068] Table 1

[0069] Example 2: Polymeric laminate composition comprising noble metal nanocluster

[0070] Another embodiment is composed of metal nanoclusters (NCs) as luminescent nanoparticles.

[0071] Here 1-adamantanethiol (1-AdSH) protected Aui6Ag7(SAdm)i5NCs is made compatible with OSTE host matrix. For the synthesis of NCs, 66 mg HAuCI4-3H20, 15 mg AgNO3and 120 mg 1-adamantanethiol were mixed in 15 mL THF and vigorously stirred for 30 min at room temperature. Then 144 mg of NaBH4dissolved in ice-cold water is added directly, and the reaction proceeded for 3 h. After 3 hours, the crude product is collected, washed by methanol three times, and extracted by acetone. Then the material is further dissolved in toluene and ethanol mixture to react overnight and finally extracted with DCM to get pure ligand protected NCs. The resulting clusters of Aui6Ag7(SAdm)i5are dissolved in DCM and used for optical characterization.

[0072] The surface coverage of polymer bonded thiol-containing ligand on the formed ligand protected metal nanocluster, corresponding to the optimal light conversion efficiency, was estimated by monitoring emission and absorption spectra modifications with a UV-dose. This is shown more precisely in Fig. la and Fig lb. 2 mg of Aui6Ag7(SAdm)i5 is mixed with an off-stoichiometric amount (0.57g / 1.85 g t hiol / a I lyl ) of thiol-ene matrix monomer solution. The in-situ reaction with the monomers is controlled by applying a controlled UV-dose (by a 365nm UV-lamp UVP B-100 producing ~ 30 mW / cm2power density at ~ 10 cm distance from it). The absorption and emission spectrum was studied at specific timepoints. The timedependent UV-VIS spectra under UV light is presented in Fig. la. As clearly visible in Fig. la, the photoluminescent (PL) peak red-shifted with increased time. The PL-peak red shifted from about 720 nm (30 min), to about 750 (20 hours), to about 800 (36 hours), to about 830 (55 hours) to about 850 nm (72 hours). The appearance of different absorption and emission spectrum of the resulting composite compared to the starting material can be attributed to the formation of new cluster initiated by the radical reaction form the OSTE counterpart with the ligand containing noble metal nanocluster. It can also be noted that, while the PL peak still red-shifted between 36 to 72 hours, the shift was considered sufficiently small for the reaction to be claimed reaching almost saturation at 72 hours. Indeed the shift rate reduces significantly with the UV-dose increase. Nanocluster's emission and absorption spectra shift as a result of the reaction with the monomers, reflecting modified electronic structure of the nanoparticle. The photoluminescence quantum yield (PLQY) of the resultant polymer formed during the reaction was also studied over time, see Fig. lb. As can be seen, the highest PLQY value was achieved at 20 hours. The resulting surface coverage corresponding to the optimal light conversion efficiency may then be estimated by comparing the Stoke Shift for the specific timepoint 20 hours over the total Stoke Shift when reaction is complete (72 hours). It was found that a surface coverage of the ligand on the noble metal nanocluster of about 30% resulted in the highest PLQY values. This value can be controlled by the UV-exposure time in metal nanoclusters nanocomposites as Fig. la demonstrates.

[0073] To make NCs / OSTE composite, at first 2 mg of vacuum dried Aui6Ag7(SAdm)i5is dispersed with allyl (0.57g) and thiol (1.85g) monomer (th iol / a I lyl group ratio of 2 / 1) along with 0.04 of lrgacure-184 photo initiator, which results in clear brownish orange solution. Then the solution was placed in a desiccator to remove air bubbles and finally poured into a glass mold 20x20x0.7 cm3to be cured with 365 nm UV light according to the preferred conditions as described above, i.e. for 20 hours. After 10 min of UV exposure, the composite solution became solid due to thiol-ene polymerization reaction.

[0074] This AuAgNCs@OSTE composite also can be used as an interlayer for laminated glass, making the composite suitable for triplex LSC fabrication

[0075] The resulting polymeric laminate composition exhibited a haze value of < 10% for visible light and was measured according to ASTM International D1003 "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" (ASTM D1003-00, 2000).

[0076] The photovoltaic performance of cured composition was measured as external quantum efficiency and power conversion efficiency values in a solar simulator (LEDbased 350 - 1100 nm spectral range, ASTM E927 class AAA+, 25x25 cm2spot size) as is shown in Table 2. The device was > 80% transparent for visible light)

[0077] Table 2

[0078] As can be seen from Table 2 the values exceeding by ~ 1.5 times that of the same size device (20x20x0.7 cm3) made of Si QDs reported in the prior art were recorded, attributed to stronger solar light absorption and higher light conversion efficiency in metal nanoclusters.

[0079] Example 3: Effect of noble metal nanocluster concentration

[0080] To evaluate nanocluster concentration effect on photovoltaic device performance, 10x10 cm2LSC devices were fabricated. They contained different amounts of noble metal nanoclusters in the thiol-ene matrix, and those were measured under a solar simulator according to Example 1 and 2 to extract power conversion efficiency values.

[0081] The resulting effect of UV-aging is shown in Figure 2. The device with a high load showed no improvement in the photovoltaic performance. However, those with low and medium load revealed a marked improvement in PCE. Note that the low load device has low absolute solar power absorption (~ 7%), thus the absolute values of PCE are also lower.

[0082] Clearly, there is an optimal concentration range allowing for NC-thiol-ene reaction to take place. It improves composite optical properties, such as quantum yield and Stokes shift, resulting in enhanced device photovoltaic performance.

Claims

CLAIMS1. A method of manufacturing a polymeric laminate composition suitable for a photovoltaic element, said polymeric laminate composition comprises off- stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles, wherein the method comprises the steps of: a) providing luminescent nanoparticles in the form of noble metal nanoclusters, and wherein said noble metal nanoclusters are selected from the group consisting of one or more of Au, Ag, Cu, Pd, Pt and a combination thereof, b) providing a thiol-functional monomer and an allyl-functional monomer, wherein said thiol-functional monomer and said allyl-functional monomer are provided in an off-stoichiometric amount, c) performing a surface modification of the provided luminescent nanoparticles of step a), resulting in the introduction of photopolymerizable functional groups on said provided luminescent nanoparticles, d) mixing the surface modified nanoparticles of step c) with the provided thiol-functional monomer and the allyl-functional monomer of step b), e) exposing the mixture of step d) to UV light in order to induce thiol-ene photopolymerization and photopolymerization between the introduced photopolymerizable function groups of step c) to thiol-ene polymer, thereby forming a polymeric laminate composition comprising off- stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles, wherein step e) results in the luminescent nanoparticles in the polymeric laminate composition of step e) having a surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer of 20- 50%, preferably of 30 - 50 even more preferably of 25 - 35%, and wherein the surface modification in step c) comprises reacting the noble metal nanoclusters with a thiol-containing ligand, by a wet-chemical method, thereby forming a ligand-noble metal nanocluster.

2. The method according to claim 1, wherein step e) comprises applying 300 - 500 nm UV-light to the mixture of step d), preferably 350-450 nm UV-light, even more preferably 350-400 nm UV-light.

3. The method according to any one of the previous claims, wherein said thiol- functional monomer contains 3 or more thiol groups per monomer, and wherein said allyl-functional monomer is an allyl amine monomer, preferably wherein said thiol-functional monomer is pentaerythritol tetrakis (3- mercaptobutylate) and said allyl-functional monomer is Trial lyl-l,3,5-triazine- 2,4,6(lH,3H,5H)-trione.

4. The method according to any one of the previous claims, wherein said thiol- functional monomer and said allyl-functional monomer are provided in a molar ratio of 1:3.

5. The method according to any one of claims 1 - 3, wherein said thiol-functional monomer and said allyl-functional monomer are provided in a molar ratio of between 1:5 - 2:5.

6. The method according to any one of the previous claims, further comprising the step of providing silicon nanospheres having a diameter of 100 - 200 nm to the mixture as selective scatterers.

7. The method according to any one of the previous claims, further comprising the step of providing Co+2doped ZnO nanoparticles with a diameter of 2 - 4 nm to the mixture as selective absorbers.

8. The method according to any one of the previous claims, wherein step e) results in noble metal nanocluster having a surface coverage of thioIcon ta in i ng ligand bonded to thiol-ene polymer of 25 - 45%, more preferably of 25 - 35%.

9. The method according to any one of the previous claims, wherein the thiol- containing ligand is 1-adamantanethiol.

10. The method according to any one of the previous claims, wherein the noble metal nanoclusters are provided in an amount of 0.1 - 1 wt-% based on the total weight of the polymeric laminate composition, preferably of 0.2 - 0.6 wt- %, even more preferably of 0.25 wt% - 0.5 wt-%.

11. The method according to any one of the previous claims, wherein the method further comprises the step of pouring the mixture of step d) into a glass mold before exposing the mixture to UV-light according to step e), thereby forming a composite structure wherein the mixture of step d) forms a middle layer sandwiched between two glass layers.

12. A photovoltaic device comprising a polymeric laminate composition manufactured according to claim 11.

13. The photovoltaic device according to claim 12, wherein the middle layer comprises a polymeric laminate composition manufactured according to any one of claims 1 - 11, wherein said middle layer has a thickness of 0.5 - 5 mm and comprises 0.1 -1 weight-% of luminescent nanoparticles, preferably wherein the middle layer has a thickness of 0.5 - 2 mm and comprises 0.25-1 weight-% of luminescent nanoparticles.

14. A polymeric laminate composition manufactured by a method of manufacturing a polymeric laminate composition suitable for a photovoltaic element, said polymeric laminate composition comprises off-stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles, wherein the method comprises the steps of: a) providing luminescent nanoparticles selected from the group consisting of Si nanocrystal quantum dots and noble metal nanoclusters, b) providing a thiol-functional monomer and an allyl-functional monomer, wherein said thiol-functional monomer and said allyl-functional monomer are provided in an off-stoichiometric amount, c) performing a surface modification of the provided luminescent nanoparticles of step a), resulting in the introduction of photopolymerizable functional groups on said provided luminescent nanoparticles, d) mixing the surface modified nanoparticles of step c) with the provided thiol-functional monomer and the allyl-functional monomer of step b), e) exposing the mixture of step d) to UV light in order to induce thiol-ene photopolymerization and photopolymerization between the introduced photopolymerizable function groups of step c) to thiol-ene polymer, thereby forming a polymeric laminate composition comprising off- stoichiometry thiol-ene polymer (OSTE) and luminescent nanoparticles, wherein step e) results in the luminescent nanoparticles in the polymeric laminate composition of step e) having a surface coverage of photopolymerizable functional groups bonded to thiol-ene polymer of 20- 50%, preferably of 30 - 50 even more preferably of 25 - 35%, wherein said laminate composition has a thickness of 0.5 - 5 mm and comprises 0.1 -1weight-% of luminescent nanoparticles, preferably wherein the laminate composition has a thickness of 0.5 - 2 mm, a haze of < 10% in the visible range measured according to ASTM International D1003 "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" (ASTM D1003-00, 2000) and comprises 0.25-1 weight-% of luminescent nanoparticles.

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