Solar wavelength conversion material, solar cell encapsulant including the same, and solar cell including the same

Abstract

The present invention relates to a solar energy conversion material with improved efficiency and a solar cell including the same. According to one embodiment of the present invention, the present invention provides a solar energy conversion material including an aluminum hydroxide precursor and lanthanide ions or a derivative including the same.

Description

Technical Field

[0001] This invention relates to a solar wavelength conversion material with improved efficiency, a solar cell encapsulation, and a solar cell including the same. Background Technology

[0002] The most common commercially available solar cells are made of silicon, and because of the mismatch between the natural solar spectrum and the band gap of silicon-based materials, about 50% of the light cannot be utilized. That is, the natural solar spectrum has a broad distribution of wavelengths from ultraviolet to infrared (280 to 2500 nm, 0.5 to 4.4 eV), while silicon solar cells can only absorb some wavelengths of ultraviolet and visible light.

[0003] Recently, to address this issue, research has been proposed on using solar wavelength conversion materials to improve the light conversion efficiency of natural sunlight and silicon solar cells (Chem. Soc. Rev., 2013, 42, 173). Specifically, this research introduces solar wavelength conversion materials (solar spectrum converters) into silicon solar cells. These materials convert light from the ultraviolet region where silicon absorbs insufficient sunlight, or from the infrared region with energy smaller than silicon's bandgap, into visible or near-infrared wavelengths, which are well absorbed by silicon.

[0004] In addition, since solar cells or solar modules, which are usually composed of solar cells, are installed outdoors and are exposed to the external environment for a long time, such as heat, humidity, solar radiation or pollution sources, long-term durability must be ensured to avoid the effects of these external factors.

[0005] To address the aforementioned issues, functional additives can be dispersed within the encapsulation. For example, long-term durability can be ensured by adding UV stabilizers, UV absorbers, or a combination of absorbers and stabilizers to the encapsulation; these can be added to improve durability against UV rays.

[0006] However, in the case of ultraviolet absorbers, light near the ultraviolet region cannot be incident on the solar cell, thus potentially reducing the overall initial output of the solar cell module undesirably. Furthermore, while introducing inorganic particles (such as silica or magnesium hydroxide) can improve the durability of the encapsulation to some extent to enhance insulation or induce moisture trapping, this can interfere with the light absorption of the solar cell due to scattering or reflection of sunlight incident on its front surface. Therefore, while adding various functional additives to address these issues can improve the durability of the encapsulation, it may reduce the overall output of the solar cell or solar cell module. Summary of the Invention

[0007] Description of technical issues in the implementation plan

[0008] To address the aforementioned problems, the present invention aims to provide a solar wavelength conversion material that can improve the photocurrent conversion efficiency of solar cells.

[0009] Another object of the present invention is to provide a solar cell encapsulation, and a solar cell with high durability and excellent photocurrent conversion efficiency.

[0010] Solution to the problem

[0011] To achieve the objectives of this invention, this invention provides a solar wavelength conversion material comprising a luminescent aluminum hydroxide precursor.

[0012] According to the implementation plan, the preferred aluminum hydroxide precursor is one of the following: aluminum monoacetate, aluminum triacetate, aluminum diacetate, triethylaluminum, trimethylaluminum, aluminum alkoxide, diethylaluminum chloride, aluminum sulfate, aluminum cyanide, aluminum nitrite, aluminum carbonate, aluminum sulfite, aluminum hydroxide, aluminum oxide, aluminum chlorate, aluminum sulfide, aluminum chromate, aluminum trichloride, aluminum perchlorate, aluminum nitrate, aluminum permanganate, aluminum bicarbonate, aluminum phosphate, aluminum oxalate, aluminum hydrogen phosphate, aluminum thiosulfate, aluminum chlorite, aluminum bisulfate, aluminum dichromate, aluminum bromide, aluminum hypochlorite, aluminum chloride hexahydrate, aluminum dihydrogen phosphate, aluminum phosphite, potassium aluminum sulfate dodecahydrate, aluminum bromate, aluminum nitride, or derivatives thereof.

[0013] According to the implementation plan, the solar wavelength conversion material preferably includes Al(OH)3, AlOOH, 5Al2O3·2H2O or Al2O3 structure.

[0014] According to the implementation scheme, the luminescent aluminum hydroxide preferably has a size in the range of 1 nm to 1000 μm.

[0015] According to the implementation plan, the luminescent aluminum hydroxide preferably has a porous structure.

[0016] According to the implementation scheme, the solar wavelength conversion material preferably further includes lanthanideions or derivatives thereof.

[0017] According to the implementation plan, lanthanide ions are preferably capable of emitting light in the near-infrared, ultraviolet, or visible wavelength regions.

[0018] According to the implementation scheme, the near-infrared luminescent lanthanide ion precursor is preferably selected from one or more of Yb (ytterbium), Nd (neodymium), Er (erbium), Ho (holmium), Tm (thulium), and derivatives thereof.

[0019] According to the implementation scheme, the lanthanide ion precursor preferably contains elements whose emission wavelength is in the visible light wavelength region.

[0020] According to the implementation scheme, based on 100 parts by weight of aluminum hydroxide precursor, lanthanide ions or derivatives containing them preferably comprise an amount of 0.001 to 10 parts by weight.

[0021] According to the implementation scheme, the solar wavelength conversion material preferably further comprises an aromatic ring compound or a derivative thereof.

[0022] According to the implementation scheme, the aromatic ring compound or its derivative is preferably located within 10 nm of the aluminum hydroxide precursor or the aluminum hydroxide derived therefrom, or preferably formed by covalent bonds.

[0023] According to the implementation scheme, the aromatic ring compound is preferably one or more of the following: an aromatic hydrocarbon in which only carbon and hydrogen are bonded together; an aromatic heterocyclic compound in which some of the carbon atoms forming the ring are replaced by oxygen, nitrogen or sulfur atoms other than carbon; or a derivative in which some hydrogen atoms in the aromatic hydrocarbon and aromatic heterocyclic compound molecules are replaced by functional groups.

[0024] According to the implementation scheme, the aromatic ring compound is preferably one or more of the following: furan, benzo[benz[furan], isobenzo[benz[furan], pyrrole, indole, isoindole, thiophene, benzo[benz[thiophene], imidazole, benzimidazole, purine, pyrazole, indazole, oxazole, benzo[oxazole], oxazole isoxazole, benzo[oxazole] isoxazole, thiazole, benzo[benz[thiazole], benzo[benz ...

[0025] According to the implementation plan, the particle size of the solar wavelength conversion material is preferably in the range of 0.5 nm to 500 μm.

[0026] According to the implementation plan, the maximum absorption wavelength of the solar wavelength conversion material is 200nm to 500nm, preferably 300nm to 450nm.

[0027] According to the implementation plan, the maximum emission wavelength of the solar wavelength conversion material is preferably between 450 nm and 1100 nm.

[0028] To achieve another objective of the present invention, the present invention provides a solar cell encapsulation comprising a solar wavelength conversion material according to the present invention.

[0029] According to the implementation scheme, the encapsulant is preferably in the form of a film with a thickness of 100 μm or less.

[0030] According to the implementation plan, the encapsulant is preferably EVA (ethylene vinyl acetate), POE (polyolefin elastomer), cross-linked polyolefin (PO), TPU (thermoplastic polyurethane), PVB (polyvinyl butyral), silicone (or polysiloxane), silicone / polyurethane hybrid or ionomer.

[0031] According to the implementation scheme, based on 100 parts by weight of the resin of the encapsulation, the solar wavelength conversion material is preferably included in an amount of 0.0001 to 10 parts by weight, preferably 1 to 10 parts by weight.

[0032] To achieve another objective of the present invention, the present invention provides a solar cell comprising a solar wavelength conversion material or a solar cell encapsulation according to the present invention.

[0033] According to the implementation scheme, the solar wavelength conversion material is preferably coated on the front surface of the solar cell or on the rear surface of the encapsulation on the front surface of the solar cell.

[0034] According to the implementation plan, the coating is preferably applied by spraying or screen coating.

[0035] According to the implementation plan, the solar cell encapsulant is preferably EVA (ethylene vinyl acetate), POE (polyolefin elastomer), cross-linked polyolefin (PO), TPU (thermoplastic polyurethane), PVB (polyvinyl butyral), silicone, silicone / polyurethane hybrid, or ionomer.

[0036] Furthermore, in a preferred embodiment of the invention, the encapsulation according to the invention is laminated on the front and rear surfaces of the solar cell, the glass is laminated on the front surface of the encapsulation located on the front surface of the solar cell, and the backsheet is laminated on the rear surface of the encapsulation located on the rear surface of the solar cell.

[0037] The beneficial effects of disclosure

[0038] When solar modules are manufactured by uniformly dispersing solar wavelength conversion materials with ultraviolet absorption and visible light photoluminescence properties in resin, not only can the ultraviolet light blocking effect through ultraviolet light absorption be expected, but also the down-conversion effect of visible light photoluminescence can be expected, thereby creating solar modules with higher output and durability.

[0039] In addition, since aluminum hydroxide can absorb heat and moisture, the durability of the encapsulated material can be further improved through its heat resistance and moisture-proof properties.

[0040] Therefore, a solar module including a package in which a solar wavelength conversion material with such photoluminescence properties is dispersed can prevent output reduction due to long-term outdoor exposure by increasing long-term durability, which contributes to the generation of solar energy.

[0041] Furthermore, the solar wavelength conversion material according to the present invention can emit one or more photons from ultraviolet light with low photocurrent conversion efficiency of solar cells to visible and near-infrared wavelength regions with high photocurrent conversion efficiency, thereby maximizing the efficiency of solar cells.

[0042] Furthermore, the solar wavelength conversion material according to the present invention introduces aromatic ring compounds and / or lanthanide ions in the step of synthesizing luminescent aluminum hydroxide to further improve the absorbance in the ultraviolet region, thereby achieving effective down-conversion and simultaneously improving the durability of the solar cell, thereby reducing the power generation cost of the solar cell and ensuring long-term output.

[0043] Solar wavelength conversion materials can improve the efficiency of solar cells by coating the front of the cell or the back of the encapsulation on the front of the cell. When the material is coated directly onto the solar cell, it induces down-conversion, thereby increasing output.

[0044] Furthermore, when the solar wavelength conversion material is located at the interface between the encapsulation and the solar cell, an increase in photovoltaic current due to the anti-reflective coating effect and an increase in Na2O generated from the tempered glass of the module can also be expected. + The solar modules are resistant to PID (potential-induced degradation) caused by ions, and to LeTID (light and high temperature-induced degradation) caused by ultraviolet light blocking and heat dissipation performance. Attached Figure Description

[0045] Figure 1 This is a cross-sectional schematic diagram of a package containing luminescent aluminum hydroxide particles, including a solar photovoltaic (PV) cell and a solar module.

[0046] Figure 2 A schematic diagram of the photoluminescence principle of aluminum hydroxide for ultraviolet light absorption and visible and near-infrared photoluminescence is shown: (a) visible light photoluminescence principle; and (b) visible and near-infrared photoluminescence principle.

[0047] Figure 3 The absorbance and photoluminescence spectrum of luminescent aluminum hydroxide are shown: the dashed line represents absorbance; and the solid line represents the photoluminescence spectrum.

[0048] Figure 4The excitation and photoluminescence spectra of near-infrared luminescent aluminum hydroxide are shown: (a) Yb doping; (b) Ce and Yb doping; (c) Tb and Yb doping; and (d) Yb and 2-naphthoic acid doping.

[0049] Figure 5 The spectrum shown illustrates the variation in photoluminescence (PL) intensity of 2-naphthoic acid-doped near-infrared luminescent aluminum hydroxide.

[0050] Figure 6 The extinction and photoluminescence spectra of luminescent aluminum hydroxide, including luminescent aluminum hydroxide, aromatic cyclic compounds and their derivatives, are shown:

[0051] (a) and (d) show the extinction and photoluminescence spectra of luminescent aluminum hydroxide (AlOH);

[0052] (b) and (e) show the extinction and photoluminescence spectra of luminescent aluminum hydroxide (AlOH-NA) containing 2-naphthoic acid; and

[0053] (c) and (f) show the extinction and photoluminescence spectra of luminescent aluminum hydroxide (AlOH-CA) containing 1,2,3,4-tetrahydrocarbazole-4-one.

[0054] Figure 7 The time-resolved fluorescence spectra of luminescent aluminum hydroxide (a) AlOH and (b) AlOH-NA are shown.

[0055] Figure 8 The total transmittance spectra of the solar encapsulants before and after the introduction of luminescent aluminum hydroxide and ultraviolet absorber are shown: the double-dotted line represents the total transmittance of EVA, the single-dotted line represents the total transmittance of EVA-AlOH 0.1, the solid line represents the total transmittance of EVA-AlOH 0.5, and the dashed line represents the total transmittance of EVA-C81 0.2.

[0056] Figure 9 The total transmittance spectra of the encapsulated material before and after the introduction of luminescent aluminum hydroxide are shown: (a) UV aging after 2000 hours; and (b) damp heat aging after 2000 hours.

[0057] Figure 10 The external quantum efficiency spectra of solar cell #2 and the AlOH-NA-Yb coated cell of Example 4 are shown in Tables 5 and 6.

[0058] Figure 11 The spectra obtained by measuring the changes in total reflectance of solar cell #2 and the AlOH-NA-Yb coated cell of Example 4 in Tables 5 and 6 are shown.

[0059] Figure 12The external quantum efficiency spectra of a silicon solar cell before and after coating it with luminescent aluminum hydroxide are shown.

[0060] Figure 13 The reflectance spectra of a silicon solar cell before and after coating it with luminescent aluminum hydroxide are shown. Detailed Implementation

[0061] The invention will be described in more detail below, but this is for the purpose of describing the invention in more detail and not intended to limit the scope of the invention.

[0062] According to an embodiment of the present invention, the present invention provides a solar wavelength conversion material comprising luminescent aluminum hydroxide having ultraviolet absorption and visible light photoluminescence properties.

[0063] Based on the light conversion method, solar wavelength conversion materials are mainly divided into two types: down-conversion and up-conversion.

[0064] First, downconversion is divided into: downshift, in which a photon with a short wavelength having an energy higher than the silicon band gap (e.g., ultraviolet light) is absorbed and then converted into a photon with a low-energy long wavelength region that silicon can absorb well; and quantum cleaving, in which the absorbed photon is converted into two or more photons in a low-energy region with a wavelength at least twice the wavelength of the absorbed photon.

[0065] Conversely, a technique known as upconversion involves absorbing and transmitting two photons in the infrared region, where the energy is less than the band gap of silicon, without being absorbed by silicon, and then converting them into a single photon that is easily absorbed by silicon in the high visible light region.

[0066] According to an embodiment of the present invention, a solar wavelength conversion material is provided, comprising: a luminescent aluminum hydroxide precursor; and lanthanide ions or derivatives containing therefrom.

[0067] According to an embodiment of the present invention, a solar wavelength conversion material is provided, comprising: a luminescent aluminum hydroxide precursor; and an aromatic cyclic compound or a derivative thereof.

[0068] This invention relates to a solar wavelength conversion material comprising low-cost luminescent aluminum hydroxide with improved efficiency and a solar cell including the same, and to a technique for improving photocurrent conversion efficiency by positioning the solar wavelength conversion material at the interface between the solar cell and the pre-encapsulation material in sunlight, or by dispersing the solar wavelength conversion material in the encapsulation material to induce downconversion, anti-reflective coating effect and improved durability in response to an increase in short-circuit current.

[0069] Figure 1This is a cross-sectional schematic diagram of a package containing luminescent aluminum hydroxide particles, including a solar photovoltaic (PV) cell and a solar module.

[0070] Reference Figure 1 Silicon solar cell modules can be manufactured by lamination after the glass / encapsulation layer / solar photovoltaic (PV) cell / encapsulation layer / backsheet are stacked in the order of glass / encapsulation layer / solar photovoltaic (PV) cell / encapsulation layer / backsheet from the front side where light is incident.

[0071] <Solar Wavelength Conversion Materials>

[0072] In order to manufacture solar wavelength conversion materials that can improve photocurrent conversion efficiency and improve the durability of encapsulation, the present invention uses luminescent aluminum hydroxide, which is a low-cost material and has properties such as excellent light absorption and photoluminescence characteristics, heat resistance and moisture resistance.

[0073] Luminescent aluminum hydroxide includes Al(OH)3, AlOOH, 5Al2O3·2H2O or Al2O3 structures, and in this invention, such structures are referred to hereinafter as aluminum hydroxide, AlOH or aluminum hydroxide.

[0074] The luminescent aluminum hydroxide precursor is one of the following: aluminum monoacetate, aluminum triacetate, aluminum diacetate, triethylaluminum, trimethylaluminum, aluminum alkanol, diethylaluminum chloride, aluminum sulfate, aluminum cyanide, aluminum nitrite, aluminum carbonate, aluminum sulfite, aluminum hydroxide, aluminum oxide, aluminum chlorate, aluminum sulfide, aluminum chromate, aluminum trichloride, aluminum perchlorate, aluminum nitrate, aluminum permanganate, aluminum bicarbonate, aluminum phosphate, aluminum oxalate, aluminum hydrogen phosphate, aluminum thiosulfate, aluminum chlorite, aluminum bisulfate, aluminum dichromate, aluminum bromide, aluminum hypochlorite, aluminum chloride hexahydrate, aluminum dihydrogen phosphate, aluminum phosphite, potassium aluminum sulfate dodecahydrate, aluminum bromate, aluminum nitride, or a derivative thereof.

[0075] According to the implementation scheme, the luminescent aluminum hydroxide preferably has a porous structure. The prepared luminescent aluminum hydroxide can be synthesized to have porosity based on variables such as precursors, solvents, impurities, or thermal decomposition reaction temperature and time. When the prepared luminescent aluminum hydroxide has porosity, the surface area is increased, and thus the durability of the encapsulated material, such as moisture resistance and heat resistance, can be improved.

[0076] According to an embodiment of the present invention, the solar wavelength conversion material according to the present invention preferably further comprises lanthanide ions or derivatives thereof.

[0077] Specifically, if lanthanide ions capable of near-infrared photoluminescence are introduced, they can absorb ultraviolet light and simultaneously emit visible and near-infrared light. Therefore, when these lanthanide ions are applied to high-efficiency solar cells with excellent power generation efficiency in the visible and near-infrared wavelength ranges, higher photocurrent conversion efficiency can be achieved.

[0078] Furthermore, when aluminum hydroxide absorbs high energy in the ultraviolet wavelength region and transfers it to lanthanide ions capable of near-infrared photoluminescence, it emits long-wavelength photons with low energy in two near-infrared wavelength regions, which are more than twice the absorption wavelength, thereby maximizing the photocurrent conversion efficiency of the solar cell.

[0079] Lanthanide ions can emit light in the near-infrared, ultraviolet, or visible wavelength regions.

[0080] According to embodiments of the present invention, in order to induce near-infrared photoluminescence, some lanthanide ions can be introduced. Near-infrared luminescent lanthanide precursors capable of emitting light in the near-infrared region with wavelengths above 800 nm can include Yb (ytterbium), Nd (neodymium), Er (erbium), Ho (holmium), Tm (thulium), etc., and based on the external quantum efficiency characteristics of the solar cell, ions with photoluminescence spectra at wavelengths with high photocurrent conversion efficiency of the solar cell can be selected and doped into aluminum hydroxide.

[0081] According to embodiments of the present invention, lanthanide ions capable of achieving near-infrared photoluminescence are selected, and for example, when Yb is selected, all derivatives including Yb can be used as precursors of Yb. Therefore, examples may include ytterbium trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate hydrate, ytterbium chloride, ytterbium fluoride, ytterbium iodide, ytterbium chloride hexahydrate, ytterbium oxide, ytterbium nitrate pentahydrate, ytterbium acetate tetrahydrate, ytterbium acetate hydrate, ytterbium polystyrene sulfonate, 3-hydroxy-2-naphthyl(2-hydroxybenzylidene)hydrazide, ytterbium isopropoxide, ytterbium bromide, tris[N,N-bis(trimethylsilyl)amide]ytterbium, etc.

[0082] Furthermore, according to embodiments of the present invention, in order to induce an effective energy transfer from luminescent aluminum hydroxide to near-infrared light, lanthanide-based ions (or lanthanide-based ions or lanthanide ions) precursors having photoluminescence wavelengths in the visible light wavelength region can be co-doped.

[0083] According to embodiments of the present invention, based on 100 parts by weight of the aluminum hydroxide precursor, lanthanide ions or derivatives thereof may be included in an amount of 0.001 to 10 parts by weight. Based on 100 parts by weight of the aluminum hydroxide precursor, when an excess of lanthanide ions is introduced beyond the range of 0.001 to 10 parts by weight, the photoluminescence performance may be degraded due to quenching caused by lanthanide ion aggregation, while when a small amount of lanthanide ions or derivatives thereof are introduced, the energy transfer from luminescent aluminum hydroxide to lanthanide ions may be limited, and therefore the downconversion effect may be difficult to predict.

[0084] According to embodiments of the present invention, when impurities or aromatic ring compounds and their derivatives are appropriately added, the trap state of aluminum hydroxide can be changed, and the position of the emission wavelength can be controlled according to the changed trap state.

[0085] According to embodiments of the present invention, based on 100 parts by weight of the aluminum hydroxide precursor, an aromatic cyclic compound or a derivative thereof may be included in an amount of 0.001 to 10 parts by weight.

[0086] Furthermore, when the light absorbed by aromatic ring compounds and their derivatives is at an energy higher than that of captured emission, energy transfer from the aromatic ring compounds and their derivatives to the captured state of aluminum hydroxide can be achieved. In this case, the photoluminescence intensity of near-infrared luminescent aluminum hydroxide is amplified through additional energy transfer. That is, aromatic ring compounds and their derivatives can act as antennas, capturing light in the ultraviolet wavelength region and transferring the captured light to aluminum hydroxide.

[0087] Therefore, compared to aluminum hydroxide alone, the presence of aromatic ring compounds and their derivatives together enables efficient ultraviolet light absorption and stronger visible and near-infrared photoluminescence. Furthermore, due to the reduced position of the trapped state, the emission wavelength shifts to a longer wavelength, and the Stokes shift (the difference between the absorption and emission wavelengths) can increase, thereby reducing the reabsorption of light emitted from the material.

[0088] For energy to be effectively transferred from aromatic cyclic compounds and their derivatives to aluminum hydroxide, the distance between the two materials must be within 10 nm or they must be covalently bonded. Therefore, the aromatic cyclic compound is preferably located within 10 nm of the aluminum hydroxide precursor or the aluminum hydroxide derived therefrom, or is in a state of being covalently bonded.

[0089] According to embodiments of the present invention, the aromatic ring compound is preferably one or more of the following: an aromatic hydrocarbon wherein only carbon and hydrogen are bonded together; an aromatic heterocyclic compound wherein some of the carbon atoms forming the ring are replaced by oxygen, nitrogen or sulfur atoms other than carbon; or a derivative wherein some of the hydrogen atoms in the aromatic hydrocarbon and aromatic heterocyclic compound molecules are replaced by functional groups.

[0090] According to embodiments of the present invention, the aromatic ring compound may be selected from one or more of the following: furan, benzo[benz[furan], isobenzo[benz[furan], pyrrole, indole, isoindole, thiophene, benzo[benz[thiophene], imidazole, benzimidazole, purine, pyrazole, indazole, oxazole, benzo[oxazole], oxazole isoxazole, benzo[oxazole] isoxazole, thiazole, benzo[benz[thiazole], benzo[benz ...

[0091] Solar wavelength conversion materials can be prepared using methods such as hydrothermal synthesis, sol-gel synthesis, and thermal decomposition synthesis. In this invention, the thermal decomposition synthesis method is described in more detail, but the scope of the invention is not limited thereto.

[0092] In the synthesis of luminescent aluminum hydroxide via thermal decomposition, materials with boiling points higher than the thermal decomposition temperature of the aluminum precursor can be used as solvents. For example, materials with boiling points of 200°C or higher, such as hexadecylamine, 1-eicosene, 1-octadecene, docosane, phenyl ether, benzyl ether, octyl ether, oleic acid, oleylamine, and polyisobutylene, can be used as solvents.

[0093] The solvent can act as a solvent and provide impurities such as carbon, carbonyl radicals, oxalate-phosphate radicals, and sulfuric acid, thereby controlling the luminescence properties or further improving the luminescence performance. Furthermore, in the pyrolysis synthesis step, by adding impurities such as alkyl groups (C1 to C2), n Acetate, thereby allowing control over absorbance and photoluminescence properties.

[0094] Furthermore, the light absorption during the pyrolysis synthesis step, particularly the absorbance of near-infrared luminescent aluminum hydroxide when appropriately supplemented with aromatic ring compounds and their derivatives having high extinction coefficients in the ultraviolet wavelength region, can induce increased photoluminescence and a large Stokes shift. Therefore, in the pyrolysis synthesis step, aromatic ring compounds are added together with aluminum hydroxide precursors and lanthanide ions.

[0095] One or more aluminum precursors, one or more lanthanide ions, and an aromatic cyclic compound and its derivatives are dispersed in a solvent and then reacted at the pyrolysis temperature of the aluminum precursors. When the reaction is complete, the product can be separated and purified to obtain the final luminescent aluminum hydroxide (solar wavelength conversion material).

[0096] Aluminum hydroxide synthesized by pyrolysis exhibits photoluminescence properties due to trapped emission caused by defects in the metal oxide. In trapped emission, when defects exist in the material, a trapped state is formed between the ground state and the excited state. Electrons that transfer from the ground state to the excited state through external energy are stabilized and move to a lower energy level generated by the defect, emitting light while transferring to the final ground state. Figure 2 (a) In this case, when doped with a small amount of one or more lanthanide ions capable of near-infrared photoluminescence, energy is transferred from aluminum hydroxide to the lanthanide ions, and near-infrared photoluminescence occurs at low energy (with a wavelength greater than twice the wavelength of photoluminescence of aluminum hydroxide). Specifically, two or more photons can be emitted in the near-infrared wavelength region. Figure 2 (b)).

[0097] Since the solar wavelength conversion material is located at the front of the solar cell, it is advantageous to use particles smaller than the wavelength of sunlight incident on the solar cell. If the particle size is similar to or larger than the wavelength of the incident sunlight, the incident sunlight may be scattered or reflected, potentially reducing the overall efficiency of the solar cell. Therefore, the particle size of the solar wavelength conversion material can range from 0.5 nm to 500 μm, preferably from 1 nm to less than 100 μm.

[0098] The luminescent aluminum hydroxide according to the present invention preferably has an absolute quantum yield of 40% or higher.

[0099] Figure 3 The absorbance and photoluminescence spectra of luminescent aluminum hydroxide prepared by pyrolysis synthesis are shown. More specifically, the dashed line represents the absorption spectrum of aluminum hydroxide, which begins to absorb at 450 nm and exhibits strong absorbance in the ultraviolet region, and the solid line represents the photoluminescence spectrum, showing a maximum emission peak at 526 nm.

[0100] To apply solar wavelength conversion materials to silicon solar cells, these materials should exhibit absorbance in the ultraviolet wavelength region and photoluminescence properties in the visible and near-infrared wavelength regions. Specifically, the absorption wavelength region of the solar wavelength conversion material is preferably formed in the range of 200 to 500 nm. Furthermore, the photoluminescence wavelength region is preferably formed at 450 nm or greater, and more preferably in the range of 450 nm to 1100 nm.

[0101] In particular, regarding solar wavelength conversion materials, it is preferable that the absorption wavelength region and the photoluminescence wavelength region do not overlap, and it is advantageous to use materials with a large Stokes shift, because when the absorption wavelength region and the photoluminescence wavelength region overlap, the reabsorption of light emitted by the material will be considered a loss.

[0102] The prepared luminescent aluminum hydroxide can be synthesized to have porosity based on variables such as precursors, solvents, impurities, or thermal decomposition reaction temperature and time. When the luminescent aluminum hydroxide has porosity, the surface area increases, which can improve the durability of solar modules, such as moisture resistance and heat resistance.

[0103] For solar wavelength conversion materials, especially down-conversion materials, the required characteristics include high luminous efficiency, high extinction coefficient, high light safety, ultraviolet light absorption, photoluminescence below visible wavelengths, and a large Stokes shift (the wavelength difference between the maximum absorption wavelength and the maximum emission wavelength (Δλ = λ)). 发射 -λ 吸收 ))wait.

[0104] For downconversion materials to be used in solar cells, they must appropriately meet the required characteristics. Otherwise, the efficiency of the solar cell may be reduced. For example, when a low-luminescence-efficiency material is introduced into the front of a solar cell, sunlight may be absorbed but not converted into visible light, and thus may significantly hinder the solar cell's solar energy absorption.

[0105] Furthermore, materials with low extinction coefficients are unlikely to exhibit downconversion effects due to their low absorption efficiency, even with high luminous efficiency. For materials with absorbance lower in the visible light region than in the ultraviolet light region, commercially available silicon solar cells cannot be expected to show additional downconversion effects because the photocurrent conversion efficiency in the visible light region is already as high as 90%. Additionally, materials with small Stokes shifts have a large overlap between their absorption wavelength and photoluminescence wavelength, and therefore may suffer losses due to reabsorption of emitted light, thus preventing the expectation of effective downconversion.

[0106] Meanwhile, when quantum cutting is induced, short-wavelength photons that the solar cell cannot absorb are emitted as two or more long-wavelength photons, resulting in high conversion efficiency of the solar cell, thus significantly improving the efficiency of the solar cell.

[0107] According to the implementation plan, the solar wavelength conversion material is preferably used in the form of a thin film with a thickness of 100 μm or less, prepared by dispersing it in a light-transmitting resin.

[0108] In the following description, in order to demonstrate that the solar wavelength conversion material manufactured according to the present invention is an excellent solar wavelength conversion material capable of improving the efficiency of solar cells, the present invention will be described with reference to the accompanying drawings.

[0109] Figure 4 The excitation and photoluminescence spectra of the near-infrared luminescent aluminum hydroxide thus prepared are shown. Figure 4(a) shows the excitation and photoluminescence spectra of near-infrared luminescent aluminum hydroxide doped with Yb alone. When a xenon lamp was used as the excitation source to irradiate 350 nm ultraviolet light, blue light emission (dotted line) near 450 nm and near-infrared light emission (dashed line) near 1000 nm appeared simultaneously. To determine in which wavelength regions the visible and near-infrared photoluminescence of aluminum hydroxide was absorbed and expressed, the excitation spectrum was analyzed.

[0110] exist Figure 4 In (a), the dotted line represents the excitation spectrum of photoluminescence at 450 nm, and the dashed line represents the excitation spectrum of photoluminescence at 1000 nm. This confirms that both visible-light photoluminescence and near-infrared photoluminescence occur by absorbing wavelengths in the ultraviolet region within the range of 300 nm to 500 nm. Furthermore, in Figure 4 In (b) and 4(c), even with the additional introduction of Ce and Tb, no Ce and Tb photoluminescence peaks were observed, but only alumina and Yb photoluminescence peaks were observed, confirming that effective energy transfer occurs in the order of hydroxide, Ce (or Tb) and Yb.

[0111] at the same time, Figure 4 (d) shows the excitation and photoluminescence spectra of near-infrared luminescent aluminum hydroxide prepared by introducing 2-naphthoic acid with Y as an aromatic cyclic compound and its derivatives. Figure 4 In (d), the double-dotted and dashed lines represent the maximum emission peaks near 500 nm and 1000 nm in the photoluminescence spectrum, respectively. When 2-naphthoic acid is added, it can be seen that... Figure 4 (a) In comparison, the maximum emission peak shifts to a longer wavelength of approximately 50 nm, which implies, as described above, an alteration of the trapped state by introducing 2-naphthoic acid, and also implies a reduction in reabsorption loss due to the longer wavelength shift in the photoluminescence spectrum. Furthermore, the observation of an emission peak for Yb in the near-infrared region confirms that efficient energy transfer was achieved in the order of 2-naphthoic acid, aluminum hydroxide, and Yb. (See reference...) Figure 4 (a) to Figure 4 As described in (c), observation of the excitation spectrum confirms that visible and near-infrared light emitted near 500 nm and 1000 nm are absorbed by wavelengths in the ultraviolet region in the range of 300 nm to 500 nm. Figure 4 (d)).

[0112] Figure 5The near-infrared photoluminescence spectra of aluminum hydroxide with Yb alone or with Yb containing 2-naphthoic acid are shown. The dashed line represents the photoluminescence spectrum of Yb alone, and the solid line represents the photoluminescence spectrum of Yb and 2-naphthoic acid introduced together. It is confirmed that when 2-naphthoic acid is added, the photoluminescence of aluminum hydroxide is amplified with increasing UV absorption, and efficient energy is transferred to Yb, thereby improving the photoluminescence intensity of Yb.

[0113] Figure 6 The extinction spectrum and photoluminescence spectrum of the luminescent aluminum hydroxide complex are shown. Specifically, Figure 6 (a) and Figure 6 (d) Extinction and photoluminescence spectra of aluminum hydroxide (AlOH) are shown separately, with absorption starting at 450 nm and exhibiting absorption in the ultraviolet region. Furthermore, characteristic photoluminescence peaks are observed at 390 nm, 465 nm, and 514 nm, with the maximum emission wavelength at 465 nm. Figure 6 (b) and Figure 6 (e) shows the extinction and photoluminescence spectra of luminescent aluminum hydroxide (AlOH-NA) prepared by introducing 2-naphthoic acid along with an aluminum precursor during the synthesis step. Similar to aluminum hydroxide AlOH alone, absorption begins at 450 nm and exhibits strong absorption in the 380 nm wavelength region. Meanwhile, the maximum emission wavelength is 520 nm, which is a longer wavelength shift to approximately 55 nm compared to AlOH. Figure 6 Images (c) and 6(f) show the extinction and photoluminescence spectra of luminescent aluminum hydroxide (AlOH-CA) prepared by introducing 1,2,3,4-tetrahydrocarbazole-4-one along with an aluminum precursor during the synthesis step. Absorption begins at 500 nm, and strong absorption is observed in the 370 nm wavelength region. Simultaneously, the maximum emission wavelength is 530 nm, a longer wavelength shift of approximately 65 nm compared to AlOH. Figure 6 The results confirmed that when aromatic ring compounds were introduced into the pyrolysis synthesis step, the absorption in the ultraviolet region was improved, and the difference between the maximum absorption wavelength and the photoluminescence wavelength was further increased, thus minimizing the loss due to reabsorption.

[0114] Time-resolved fluorescence (TRF) can provide a clearer understanding of the changes in the photoluminescence properties of luminescent aluminum hydroxide caused by the addition of aromatic cyclic compounds and their derivatives, as well as the energy transfer effects of aromatic cyclic compounds and their derivatives.

[0115] Figure 7 (a) and Figure 7 (b) shows the TRF spectra of AlOH and AlOH-NA, and the mean lifetime (τ) can be calculated from these spectra. 平均 ). Figure 7 (a) Shows the emission wavelengths of AlOH observed at 400 nm, 450 nm, and 500 nm, respectively, and the mean lifetime (τ) 平均 The values ​​were 1.07 ns, 2.19 ns, and 3.39 ns, respectively. Meanwhile, Figure 7 (b) shows the emission wavelengths of AlOH-NA observed at 400 nm, 450 nm, 500 nm, and 520 nm, respectively, and it can be seen that the average lifetime of AlOH-NA at each wavelength is greater than the average lifetime of AlOH (τ). 平均 ), and the average lifetime (τ) calculated from this figure. 平均 The values ​​are 1.21 ns, 8.18 ns, 11.25 ns, and 11.84 ns, respectively. This means that the average lifetime of AlOH emission is typically extended because the energy of the ultraviolet light absorbed by the NA is transferred to AlOH. In other words, when aromatic ring compounds or their derivatives are introduced together in the synthetic steps, it can be seen that strong absorption of light in the ultraviolet region and efficient energy transfer are achieved. This implies the realization of efficient downconversion.

[0116] Depending on where the material is introduced, methods for introducing synthetic solar wavelength conversion materials into solar cells may include methods for manufacturing silicon solar cells in sheet form by dispersing the material in an encapsulation used to protect the silicon solar cell, methods for applying the material directly to the entire surface of the silicon solar cell, methods for applying the material to the surface of an encapsulation bonded to the front surface of the solar cell, and so on.

[0117] <Solar Cell Encapsulation>

[0118] Solar wavelength conversion materials are dispersed in resin to form sheets and are used to manufacture solar photovoltaic modules.

[0119] First, materials such as ethylene vinyl acetate (EVA), polyolefin elastomer (POE), cross-linked polyolefin, thermoplastic polyurethane (TPU), polyvinyl butyral (PVB), silicone, silicone / polyurethane hybrids, ionomers, etc., are used as encapsulation for solar cells, with EVA or POE being the most commonly used.

[0120] Typically, numerous methods for manufacturing solar cell modules by thermal lamination are being reported, whereby solar wavelength conversion materials are introduced into an encapsulation and placed on the front surface of the solar cell, and there are instances where these reported methods are applied to commercial production.

[0121] However, in this case, due to the refractive index (n ~ 1.4) of the polymer constituting the encapsulation (such as EVA or POE) and the SiN on the surface of the silicon solar cell,x The significant difference in refractive index (n~2.5) means that light emitted from the solar wavelength conversion material inside the encapsulation cannot travel to the solar cell but instead travels to the side of the encapsulation sheet. This is because waveguide phenomena caused by total internal reflection within the encapsulation dominate. This phenomenon can be considered as light loss from the solar cell side.

[0122] <Applied to the surface of the solar cell>

[0123] Conversely, when applied to the surface of a solar cell or its encapsulation, the solar wavelength conversion material is located at the interface between the encapsulation and the solar cell. Due to its silicon texture structure ranging from several micrometers (μm) to tens of micrometers (μm), light does not travel laterally but instead travels into the interior of the solar cell. Furthermore, if the solar wavelength conversion material can be tuned to a value between the refractive index of the encapsulation (n ~ 1.4) and the refractive index of the solar cell surface (n ~ 2.5), according to Snell's law, all light traveling towards the encapsulation, the solar wavelength conversion material, and the solar cell becomes highly advantageous. Therefore, more light can be utilized on the solar cell side, thereby improving photocurrent conversion efficiency. In other words, both the downconversion effect and the anti-reflective coating effect of the solar wavelength conversion material can be expected.

[0124] When dispersed in a solvent, solar wavelength conversion materials can be applied to the surface of solar cells. Methods for application to solar cell surfaces include spin coating, bar coating, spraying, dip coating, and screen printing. Furthermore, when applied to encapsulations, all methods except spin coating can be used.

[0125] <Solar cell module / Solar cell>

[0126] According to an embodiment of the present invention, in the case of a silicon solar module, such as Figure 1 As shown in the schematic diagram, a silicon solar cell module is fabricated by stacking glass / encapsulation layer / photovoltaic (PV) cell / encapsulation layer / backsheet on the front surface from which light is incident, and then by lamination, wherein luminescent aluminum hydroxide can be dispersed on the front surface of the encapsulation or dispersed on both the front and back surfaces of the encapsulation.

[0127] According to embodiments of the present invention, the type and size of the materials constituting the solar cell are not limited thereto. For example, the present invention relates to a solar cell that can be applied regardless of the material type, including organic photovoltaic (OPV) cells, solar cells based on semiconductors such as copper indium gallium selenide (CIGS), cadmium telluride (CdTe), perovskite, etc., silicon-based solar cells, and solar cells based on semiconductor-silicon tandem structures, wherein the photocurrent conversion efficiency of the solar cell is improved.

[0128] However, in order to explain the present invention, a 6-inch polycrystalline silicon solar cell is used and described.

[0129] In this invention, a spraying method that enables rapid and uniform coating is used with consideration for commercial production applications, but the invention is not limited thereto.

[0130] Publication method

[0131] Preferred embodiments of the present invention will be described in detail below; however, the following embodiments are provided only to facilitate understanding of the invention, and the scope of the invention is not limited to the following embodiments.

[0132] Preparation Example 1: Preparation of Solar Wavelength Conversion Material (Aluminum Hydroxide Precursor)

[0133] 10 g of aluminum acetate was mixed with 100 ml of 1-octadecene solvent, and then subjected to a thermal decomposition reaction at 300 °C with stirring for 30 minutes. After the reaction was completed, the aluminum hydroxide was separated by centrifugation and redispersed in 10 ml of toluene solvent. Figure 3 The UV-Vis and photoluminescence spectra of the luminescent aluminum hydroxide solution prepared in this way are shown, where the dashed lines represent absorption and the solid lines represent photoluminescence spectra. Examples based on the aluminum hydroxide content are designated as Examples 1 and 2, respectively.

[0134] Preparation Example 2: Preparation of Solar Wavelength Conversion Material (Aluminum Hydroxide Precursor + Lanthanide Ions)

[0135] 10 g of aluminum acetate was mixed with 10 ml of 1-octadecene solvent. Ytterbium(III) acetate hydrate (from the aforementioned near-infrared luminescent lanthanide ions) was added to this mixture at an amount of 0.2 wt%, compared to the aluminum precursor, and then a thermal decomposition reaction was carried out at 300 °C with stirring for 30 minutes. After the reaction was complete, the aluminum hydroxide was separated by centrifugation and redispersed in 10 ml of toluene solvent. The solar wavelength conversion material thus synthesized was used in Example 3, and the solar wavelength conversion material synthesized without the addition of ytterbium(III) acetate hydrate was used in Comparative Example 5.

[0136] Preparation Example 3: Preparation of Solar Wavelength Conversion Material (Aluminum Hydroxide + Aromatic Ring Compound)

[0137] 10 g of aluminum acetate was mixed with 100 ml of 1-octadecene solvent, and then subjected to a thermal decomposition reaction at 300 °C with stirring for 30 minutes. After the reaction was completed, the aluminum hydroxide was separated by centrifugation and redispersed in 10 ml of toluene.

[0138] To control the photoluminescence properties, 3-hydroxy-2-naphthoic acid was added as an aromatic ring compound at a rate of 5% by weight, compared with aluminum acetate as an aluminum precursor, and the mixture was subjected to thermal decomposition at 300°C under stirring for 30 minutes, followed by separation and purification.

[0139] Preparation Example 4: Preparation of Solar Wavelength Conversion Materials (Aluminum Hydroxide + Lanthanide Ions + Aromatic Ring Compounds)

[0140] The solar wavelength conversion material was prepared in the same manner as in Preparation Example 2, except that, to further enhance ultraviolet absorption and control photoluminescence properties, 0.2% by weight of 3-hydroxy-2-naphthoic acid, an aromatic ring compound derivative, was added instead of the aluminum precursor, and the reaction was carried out under stirring in the same manner as described above, followed by separation and purification. The solar wavelength conversion material thus synthesized was used in Example 4, and the solar wavelength conversion material synthesized without the addition of ytterbium(III) acetate hydrate was used in Comparative Example 6.

[0141] Examples 1 and 2: Manufacturing encapsulation sheets containing solar wavelength conversion materials

[0142] In the encapsulation sheet manufacturing step, the solar wavelength conversion material prepared in Preparation Example 1 was added to the encapsulation resin, and then an encapsulation sheet in which the solar wavelength conversion material was dispersed was prepared by extrusion. As the encapsulation resin, an ethylene vinyl acetate copolymer (manufactured by Hanwha Total Petrochemical Co., Ltd.) with a melt index of 15 g / 10 min and a vinyl acetate content of 28 wt% was used. One part by weight of Luperox TBEC (tert-butyl-2-ethylhexyl monoperoxycarbonate) manufactured by Alkemas, 0.5 parts by weight of TAICROS (traceryl isocyanurate) manufactured by Evonik as a crosslinking aid, 0.1 parts by weight of Tinuvin 770 (bis-2,2,6,6,-tetramethyl-4-piperidinyl sebacate) manufactured by Ciba as a UV stabilizer, and 0.3 parts by weight of OFS-6030 (methacryloyloxypropyltrimethoxysiloxane) manufactured by Dow Corning as a silane coupling agent were added to 100 parts by weight of EVA and mixed. EVA sheets were then manufactured by extrusion at a temperature maintained at 100°C and a T-die temperature maintained at 100°C, with a sheet thickness of 0.5 mm. Hereinafter, each sheet thus prepared is referred to as "EVA".

[0143] For the evaluation of durability, sheets were manufactured in the same manner as the above-described EVA sheet manufacturing method, except that 0.1 or 0.5 parts by weight of luminescent aluminum hydroxide were added to 100 parts by weight of EVA in the EVA sheet manufacturing method, and the manufactured sheets were designated as "EVA-AlOH 0.1" and "EVA-AlOH 0.5", and respectively designated as Example 1 and Example 2.

[0144] For comparative evaluation, Comparative Example 1 used sheets manufactured in the same manner as in Example 1, except that luminescent aluminum hydroxide (hereinafter referred to as "EVA" sheet) was not used, and the sheets were prepared in the same manner, except that 0.1, 0.2, and 0.5 parts by weight of Chimassorb 81 (2-hydroxy-4-octyloxy-benzophenone) manufactured by Ciba was added as an ultraviolet light absorber, and was designated as "EVA-C81 0.1", "EVA-C81 0.2", and "EVA-C81 0.5", respectively, for Comparative Examples 2 to 4.

[0145] The examples and comparative examples are listed in Table 1 below, based on the introduction and content of luminescent aluminum hydroxide (AlOH) and ultraviolet absorber (C81).

[0146] Table 1

[0147] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Added AlOH (wt%) 0.1 0.5 - - - - Added C81 (wt%) - - - 0.1 0.2 0.5

[0148] <Manufacturing solar modules including encapsulated materials containing luminescent aluminum hydroxide>

[0149] Each encapsulation sheet manufactured in Examples 1 and 2, as well as Comparative Examples 1 to 4, was stacked in the following order: glass (200 mm × 200 mm), encapsulation layer, 6-inch polycrystalline solar cell manufactured by GINTECH, encapsulation layer, and PVDF (polyvinylidene fluoride) based backsheet manufactured by SFC, and micromodules were manufactured by thermal lamination. In the thermal lamination process, after a vacuum step at 150°C for 6 minutes, crosslinking was performed for 11 minutes by maintaining a pressure difference of 0.4 MPa between the upper and lower pressures of the laminator.

[0150] Experimental Example 1: Evaluation of Encapsulation Durability

[0151] To evaluate the durability of the encapsulation based on the introduction of luminescent aluminum hydroxide, accelerated weathering tests were conducted on samples in which the encapsulation was located between a fabricated miniature solar module and two glass plates. For the UV aging test, the samples were exposed to a UV lamp (340 nm, 0.9 W / m²) at a temperature of 63°C. 2 Under conditions of 85°C and 85% humidity, changes in the total transmittance characteristics (of the glass sample) and the solar cell efficiency (of the solar micromodule sample) were observed over time. For the damp heat aging test, changes in the total transmittance characteristics (of the glass sample) and the solar cell efficiency (of the solar micromodule sample) were observed over time by exposing the samples to these conditions. Solar cell efficiency was analyzed using a solar simulator (WXS-156S-10) manufactured by WACOM, and transmittance characteristics were analyzed using an UltraScan PRO spectrometer (HunterLab).

[0152] Figure 8The total transmittance of the samples obtained by thermally laminating the encapsulants of Examples 1 and 2 and Comparative Examples 1 and 3 between two glass substrates is shown. The double-dotted line represents the total transmittance of the EVA sample (Comparative Example 1), which shows a high transmittance of 90% across the entire wavelength range. The EVA-AlOH 0.1 and EVA-AlOH 0.5 samples (Examples 1 and 2) show an AlOH (aluminum hydroxide) absorption peak at or above 450 nm in the ultraviolet region and a high transmittance of 90% in the visible light region, similar to the EVA sample (Comparative Example 1). Meanwhile, it can be seen that the transmittance of EVA-C81 (Comparative Example 3) drops sharply in the ultraviolet region at or above 400 nm. That is, as described above, when using ultraviolet light absorbers, the durability of the encapsulant can be improved through the ultraviolet light blocking effect. However, ultraviolet light at or below 400 nm cannot be absorbed by the solar cell and cannot be converted into electrical energy, resulting in an undesirable reduction in initial output.

[0153] Figure 9 The total transmittance of a sample thermally laminated with an encapsulant placed before and after the introduction of luminescent aluminum hydroxide between two glass substrates is shown after 2000 hours of UV and damp heat aging tests. Figure 9 (a) shows the results of the UV aging test, confirming that the encapsulations of Example 1 (EVA-AlOH 0.1, dashed line) and Example 2 (EVA-AlOH 0.5, double-dotted line) (in which aluminum hydroxide was introduced) maintained the same properties as... Figure 3 The accelerated testing showed the same transmittance level as before, but the transmittance of EVA decreased in the ultraviolet region at 400 nm and above. Additionally, Figure 9 (b) shows the results of the damp heat aging test, confirming that the encapsulations of Example 1 (EVA-AlOH 0.1, dashed line) and Example 2 (EVA-AlOH 0.5, double-dotted line) (in which aluminum hydroxide was introduced) maintained their properties. Figure 8 The same transmittance level as before the accelerated test, similar to Figure 9 (a) UV aging test, but Comparative Example 1 EVA has a sharp drop in transmittance in the UV region of 400 nm or above, which means that light in the UV region of 400 nm or above cannot pass through the encapsulation and therefore cannot reach the solar cell, indicating that the solar cell cannot convert as much light into electrical energy as possible.

[0154] Tables 2 to 4 show the open-circuit voltage (V) determined by current-voltage (IV) curve analysis of the micro solar modules before and after durability evaluation based on the introduction of luminescent aluminum hydroxide. oc ), short-circuit current density (J sc ), fill factor (FF), and efficiency value.

[0155] Table 2

[0156]

[0157]

[0158] In Table 2, prior to weathering degradation, the solar modules using the encapsulations of Example 1 (EVA-AlOH 0.1) and Example 2 (EVA-AlOH 0.5) incorporating luminescent aluminum hydroxide showed improvements in relative efficiency of 2.33% and 2.68%, respectively, compared to modules using encapsulations containing EVA alone. That is, it can be seen that by introducing luminescent aluminum hydroxide, the initial efficiency of the solar module increases with the increase in short-circuit current density due to the down-conversion of ultraviolet absorption and visible light photoluminescence.

[0159] Table 3

[0160]

[0161] Furthermore, according to Table 3, regarding the efficiency change of the samples after 2000 hours of UV aging testing, the solar modules using the encapsulation of Example 1 (EVA-AlOH 0.1) and Example 2 (EVA-AlOH 0.5) incorporating luminescent aluminum hydroxide showed an improvement of 3.35% and 3.59% in relative efficiency, respectively, compared to modules using encapsulations that only used EVA. That is, as referenced above... Figure 9 As described, in the case of using EVA encapsulation alone (Comparative Example 1), the transmittance of the EVA encapsulation layer decreases with UV aging, thus reducing the photocurrent conversion efficiency of the solar cell under the encapsulation. However, in the cases of EVA-AlOH 0.1 and EVA-AlOH 0.5 encapsulations, the same transmittance level as before UV aging was maintained, thereby preventing a decrease in the output of the solar cell. Furthermore, in Comparative Examples 2 to 4, Chimassorb 81 (2-hydroxy-4-octyloxy-benzophenone) manufactured by Ciba was added to EVA as a UV absorber. Compared with the EVA encapsulation alone (Comparative Example 1), the efficiencies of EVA-C81 0.1, 0.2, and 0.5 were 0.12%, -0.18%, and -1.43%, respectively, indicating unfavorable results compared to the examples. It can also be seen that when using encapsulations in Comparative Examples 2 and 4 with the same content of luminescent aluminum hydroxide as in Examples 1 and 2 of the present invention, undesirable results were obtained.

[0162] Table 4

[0163]

[0164] Furthermore, as shown in Table 4, regarding the efficiency change of the samples after 2000 hours of exposure in the damp heat aging test, the solar modules using the encapsulations of Example 1 (EVA-AlOH 0.1) and Example 2 (EVA-AlOH 0.5) incorporating luminescent aluminum hydroxide showed improvements in relative efficiency of 5.43% and 5.87%, respectively, compared to modules using encapsulations containing EVA alone. The relative efficiency values ​​for the incorporation of luminescent aluminum hydroxide showed a greater difference in the damp heat aging test results than in the UV aging test, because the EVA encapsulation showed more severe degradation in the damp heat aging test than in the UV aging test, and this degradation could be prevented by the introduction of luminescent aluminum hydroxide, thereby maintaining the transmittance of the encapsulation. As described above, the present invention provides a technique in which, when solar cells and solar modules are formed by dispersing luminescent aluminum hydroxide in a solar encapsulation, the transmittance of the encapsulation layer is maintained by improving the durability of the encapsulation, thereby improving the long-term durability of the solar cells and solar modules, and ensuring power generation by minimizing the reduction in output over time.

[0165] Examples 3 to 6: Manufacturing encapsulation sheets containing solar wavelength conversion materials

[0166] The aluminum hydroxide solutions prepared in Preparation Examples 2 and 4 (Examples 3 and 4) and Preparation Examples 1 and 3 (Examples 5 and 6) were each applied to the surface of a 6-inch polycrystalline silicon solar cell using a spraying method, positioning it at the interface between the silicon cell and the encapsulation. The front surface, from which light incident, was laminated in the order of glass / encapsulation layer / photovoltaic (PV) cell / encapsulation layer / backsheet, and then a silicon solar cell module was fabricated by lamination. In the fabricated solar cell module, near-infrared emitting aluminum hydroxide was located between the encapsulation and the solar cell interface. The composition of the solar wavelength conversion materials constituting the solar cell is shown in Table 5, and each comprises 50 mg.

[0167] Comparative Example 5: Fabrication of a solar cell containing luminescent aluminum hydroxide

[0168] In comparison, a simple mixed solution of 50 mg of separately prepared luminescent aluminum hydroxide as a precursor of aluminum hydroxide and 0.1 mg of lanthanide ion ytterbium(III) acetate hydrate was sprayed onto the surface of a silicon cell. The solar cell was prepared in the same manner as in Example 3, except that the simple mixed solution of luminescent aluminum hydroxide and ytterbium(III) acetate hydrate was prepared.

[0169] Table 5 (Unit: mg / ml)

[0170]

[0171] Experimental Example 2: Performance Evaluation of Solar Cells Containing Solar Wavelength Conversion Materials

[0172] To analyze the change in solar cell efficiency based on the introduction of luminescent aluminum hydroxide, a solar simulator (WXS-156S-10) manufactured by WACOM was used. Furthermore, to measure the total reflectance based on the aluminum hydroxide coating, a UV-3600NIR (with MPC-3100) manufactured by Shimadzu was used, and the changes before and after the coating were analyzed.

[0173] Table 6 shows the results of measuring the efficiency of 6-inch polycrystalline silicon solar cells coated with luminescent aluminum hydroxide. To improve the accuracy of the efficiency measurement, the efficiency of all solar cells was measured before the application of aluminum hydroxide and then compared with the results after the application of aluminum hydroxide. Solar cells 1 to 5 below are solar cells manufactured under the same conditions as the corresponding example and comparative example solar cells, excluding solar wavelength conversion materials.

[0174] Table 6

[0175]

[0176]

[0177] Table 6 shows that applying luminescent aluminum hydroxide AlOH, AlOH-NA, AlOH-Yb, and AlOH-NA-Yb improved both short-circuit current density and efficiency compared to uncoated silicon solar cells. The relative efficiency changes for AlOH, AlOH-NA, AlOH-Yb, and AlOH-NA-Yb were 1.33%, 2.27%, 3.51%, and 5.04%, respectively, which are better than those for AlOH and AlOH-NA, doping with Yb to achieve near-infrared photoluminescence. Specifically, it was confirmed that the relative efficiency was significantly improved when 2-naphthoic acid was co-doped with Yb compared to Yb doping alone.

[0178] Furthermore, in Comparative Example 5, when a solar cell was fabricated by spraying a mixed solution of luminescent aluminum hydroxide (AlOH) synthesized using a single aluminum hydroxide precursor and ytterbium(III) acetate hydrate (a lanthanide ion) onto the surface of a silicon cell, a relative efficiency improvement of 1.29% was demonstrated. This is similar to the results of Comparative Example 5, where only luminescent aluminum hydroxide was coated. This is because no effective energy transfer from luminescent aluminum hydroxide to Yb ions occurred; therefore, only the downconversion effect of luminescent aluminum hydroxide was achieved. This clearly demonstrates the light conversion effect of luminescent aluminum hydroxide according to the present invention.

[0179] To verify this efficiency improvement, the photocurrent conversion efficiency (or external quantum efficiency) before and after the luminescent aluminum hydroxide coating was measured, and Figure 10 The results of measuring the changes in external quantum efficiency of solar cell #2 in Table 6 and the AlOH-NA-Yb coated cell in Example 4 are shown.

[0180] exist Figure 10 In the table, the dashed line represents the external quantum efficiency spectrum of solar cell #2 in Table 6, and the solid line represents the external quantum efficiency spectrum of the AlOH-NA-Yb coated cell in Example 4. Furthermore, it can be seen that after Yb coating, the conversion efficiency from 300 nm to approximately 500 nm is significantly improved through downconversion.

[0181] Figure 11 The results of measuring the change in total reflectance of solar cells #2 and AlOH-NA-Yb coated cells of Example 4 in Table 6 are shown. The dashed line represents the total reflectance before coating with near-infrared photoluminescent aluminum hydroxide, and the solid line represents the reflectance spectrum after coating with AlOH-NA-Yb. It can be seen that after coating, the reflectance decreases more in the 300 to 500 nm and 800 to 1100 nm regions, resulting in lower reflectance, which is more beneficial for solar cells. That is, by coating the surface of silicon solar cells with near-infrared luminescent aluminum hydroxide, the downconversion effect of ultraviolet absorption and visible and near-infrared photoluminescence, as well as the anti-reflection coating effect (where the refractive index of near-infrared luminescent aluminum hydroxide has a value between the refractive index of the silicon solar cell surface and the refractive index of the encapsulant (1.5) is achieved). <n 氢氧化铝 <2.5)) The short-circuit current of silicon solar cells increases, thereby improving the overall efficiency, which in turn facilitates the entry of light into silicon solar cells.

[0182] The present invention provides a technique in which, when solar cells and solar modules are formed by dispersing luminescent aluminum hydroxide in a solar encapsulation, the transmittance of the encapsulation layer is maintained by improving the durability of the encapsulation, thereby improving the long-term durability of the solar cells and solar modules, and ensuring power generation by minimizing the reduction in output over time.

[0183] Examples 7 to 12: Manufacturing encapsulation sheets containing solar wavelength conversion materials

[0184] Use 6-inch polycrystalline silicon solar cells.

[0185] The solar wavelength conversion material solution prepared according to Preparation Example 3 was coated onto the surface of a 6-inch silicon cell by spraying, so that it was located at the interface between the silicon solar cell and the encapsulation.

[0186] The front surface onto which light is incident is stacked in the following order: glass / encapsulation layer / solar wavelength conversion material / solar cell / encapsulation layer / backsheet, and then a silicon solar cell module can be manufactured by lamination. In the manufactured solar cell module, luminescent aluminum hydroxide is located at the interface between the encapsulation and the solar cell. As a component of the solar wavelength conversion material constituting the solar cell, luminescent aluminum hydroxide prepared using the method described above is used. In these examples, a solar wavelength conversion material prepared by adding an aromatic ring compound is used. In Examples 10 to 12, solar cells are prepared in the same manner as in Examples 7 to 9, except that only luminescent aluminum hydroxide is used without the aromatic ring compound. The content of the solar wavelength conversion material is shown in Table 7 below.

[0187] Table 7 (Unit: mg / ml)

[0188] Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Solar Wavelength Conversion Materials 8.3 16.6 20 8.3 16.6 20

[0189] Comparative Example 6

[0190] In addition to preparing the coating composition by simply mixing and dispersing the same amount of aluminum hydroxide precursor (20 mg / ml) and aromatic cyclic compound 3-hydroxy-2-naphthoic acid (2 mg / ml) as in Example 7, the solar cell was manufactured in the same manner as in Example 7, and then the coating composition was placed on the light-receiving side of the solar cell material.

[0191] Experiment Example 3: Performance Evaluation of Solar Cells Containing Solar Wavelength Conversion Materials

[0192] To analyze the efficiency changes of solar cells with the introduction of luminescent aluminum hydroxide, a solar simulator (WXS-156S-10) manufactured by WACOM was used to measure the efficiency changes before and after aluminum hydroxide coating, as well as before and after thermal lamination. Furthermore, to analyze the external quantum efficiency at various wavelengths, an IPCE (QEX10) device manufactured by PV Measurement was used to observe the changes in conversion efficiency before and after aluminum hydroxide coating. Additionally, depending on the aluminum hydroxide coating, a UV-3600NIR (with MPC-3100) manufactured by Shimadzu was used to measure the total reflectance and analyze the changes before and after coating.

[0193] Table 8 shows the results of measuring the efficiency of 6-inch polycrystalline silicon solar cells coated with luminescent aluminum hydroxide. To improve the accuracy of the efficiency measurement, the efficiency of all solar cells was measured before the application of aluminum hydroxide and then compared with the results after the application of aluminum hydroxide. Solar cells 5 to 11 below are solar cells manufactured under the same conditions as the corresponding example and comparative example solar cells, excluding solar wavelength conversion materials.

[0194] Table 8

[0195]

[0196] In Table 8, the short-circuit current density and efficiency of the silicon solar cells increased when luminescent aluminum hydroxide (AlOH) or AlOH-NA was applied compared to uncoated silicon solar cells. In particular, the short-circuit current density and efficiency were better when AlOH-NA was applied than when AlOH was applied.

[0197] Furthermore, when solar cells were fabricated by adding AlOH and NA separately, mixing and coating them (Comparative Example 6), efficient energy transfer from NA to AlOH became infeasible, and the desired results were not obtained.

[0198] To verify this increase in efficiency, the incident photon-current efficiency (IPCE) was measured before and after aluminum hydroxide coating. Figure 12 The photocurrent conversion efficiency based on wavelength, i.e., external quantum efficiency (EQE) spectrum, is shown as a result of IPCE measurements.

[0199] Figure 12 The results for solar cells #10 (Example 12) and #7 (Example 9) in Table 8 are shown. The dashed line represents the EQE spectrum before coating, the double-dotted line represents the EQE spectrum after AlOH coating (Example 12), and the solid line represents the EQE spectrum after AlOH-NA coating (Example 9). Figure 12 The results show that when coated with luminescent aluminum hydroxide, the conversion efficiency from 300 nm to about 500 nm is improved by downconversion, and when coated with AlOH-NA, more efficient downconversion can be achieved than when coated with AlOH.

[0200] also, Figure 13The results of measuring the reflectance changes of solar cells #10 (Example 12) and #7 (Example 9) in Table 8 based on the luminescent aluminum hydroxide coating are shown. The solid line represents the total reflectance before aluminum hydroxide coating, the double-dotted line represents the reflectance spectrum when AlOH is coated, and the dashed line represents the reflectance spectrum after AlOH-NA coating. It can be seen that after coating, the reflectance decreases more in the 300 to 500 nm and 800 to 1100 nm regions. Similar to the EQE spectrum, AlOH-NA has a lower reflectance in the ultraviolet wavelength region than AlOH, which is beneficial to solar cells. That is, by coating the silicon solar cell surface with luminescent aluminum hydroxide, and through the downconversion effect of ultraviolet absorption and visible light photoluminescence and the anti-reflection coating effect (wherein the refractive index of near-infrared luminescent aluminum hydroxide has the same refractive index on the silicon solar cell surface as the refractive index of the encapsulant (1.5)... <n 氢氧化铝 Values ​​between <2.5) increase the short-circuit current of silicon solar cells, thereby improving the overall efficiency and thus facilitating the entry of light into silicon solar cells.

[0201] The present invention provides a technique in which, when solar cells and solar modules are formed by dispersing luminescent aluminum hydroxide in a solar encapsulation, the transmittance of the encapsulation layer is maintained by improving the durability of the encapsulation, thereby improving the long-term durability of the solar cells and solar modules, and ensuring power generation by minimizing the reduction in output over time.

Claims

1. A solar energy wavelength conversion material, comprising luminescent aluminum hydroxide exhibiting ultraviolet light absorption and visible light photoluminescence properties. The solar wavelength conversion material further comprises lanthanide ions or derivatives thereof; or aromatic ring compounds or derivatives thereof. The solar wavelength conversion material includes Al(OH)3, AlOOH, 5Al2O3·2H2O or Al2O3 structure.

2. The solar wavelength conversion material according to claim 1, wherein the aluminum hydroxide precursor is any one of the following: aluminum monoacetate, aluminum triacetate, aluminum diacetate, triethylaluminum, trimethylaluminum, aluminum alkoxide, diethylaluminum chloride, aluminum sulfate, aluminum cyanide, aluminum nitrite, aluminum carbonate, aluminum sulfite, aluminum hydroxide, aluminum oxide, aluminum chlorate, aluminum sulfide, aluminum chromate, aluminum trichloride, aluminum perchlorate, aluminum nitrate, aluminum permanganate, aluminum bicarbonate, aluminum phosphate, aluminum oxalate, aluminum hydrogen phosphate, aluminum thiosulfate, aluminum chlorite, aluminum bisulfate, aluminum dichromate, aluminum bromide, aluminum hypochlorite, aluminum chloride hexahydrate, aluminum dihydrogen phosphate, aluminum phosphite, potassium aluminum sulfate dodecahydrate, aluminum bromate, aluminum nitride, or derivatives thereof.

3. The solar wavelength conversion material according to claim 1, wherein the size of the luminescent aluminum hydroxide is in the range of 1 nm to 1000 μm.

4. The solar wavelength conversion material according to claim 1, wherein the luminescent aluminum hydroxide has a porous structure.

5. The solar wavelength conversion material according to claim 1, wherein the lanthanide ions are capable of emitting light in the near-infrared, ultraviolet, or visible wavelength regions.

6. The solar wavelength conversion material according to claim 1, wherein the precursor of the near-infrared luminescent lanthanide ions is one or more selected from ytterbium, neodymium, erbium, holmium, thulium, and derivatives thereof.

7. The solar wavelength conversion material according to claim 1, wherein the lanthanide ion precursor comprises an element having a photoluminescence wavelength in the visible light wavelength region.

8. The solar wavelength conversion material according to claim 1, wherein the lanthanide ion or its derivatives comprising the lanthanide ion are included in an amount of 0.001 to 10 parts by weight based on 100 parts by weight of the aluminum hydroxide precursor.

9. The solar wavelength conversion material according to claim 1, comprising lanthanide ions or derivatives thereof; and aromatic ring compounds or derivatives thereof.

10. The solar wavelength conversion material according to claim 1, wherein the aromatic ring compound or its derivative is located within 10 nm of the aluminum hydroxide precursor or the aluminum hydroxide derived therefrom, or is formed by covalent bonds.

11. The solar wavelength conversion material according to claim 1, wherein the aromatic ring compound is one or more of the following: an aromatic hydrocarbon wherein only carbon and hydrogen are bonded together; an aromatic heterocyclic compound wherein some of the carbon atoms forming the ring are replaced by oxygen, nitrogen, or sulfur atoms other than carbon; or a derivative wherein some of the hydrogen atoms in the aromatic hydrocarbon and the aromatic heterocyclic compound molecules are replaced by functional groups.

12. The solar wavelength conversion material according to claim 1, wherein the aromatic ring compound is one or more of the following: furan, benzo[a]benzo[a]furan, isobenzo[a]benzo[a]furan, pyrrole, indole, isoindole, thiophene, benzo[a]benzo[a]thiophene, imidazole, benzimidazole, purine, pyrazole, indazole, oxazole, benzo[a]oxazole, oxazole isoxazole, benzo[a]oxazole isoxazole, thiazole, benzo[a]benzo[a]thiazole, benzo[a]benzene, naphthalene, anthracene, pyridine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cyclophosphine, phthalazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine and its derivatives.

13. The solar wavelength conversion material according to claim 1, wherein the particle size of the solar wavelength conversion material is from 0.5 nm to 500 μm.

14. The solar wavelength conversion material according to claim 1, wherein the maximum absorption wavelength of the solar wavelength conversion material is 200 nm to 500 nm.

15. The solar wavelength conversion material according to claim 1, wherein the maximum emission wavelength of the solar wavelength conversion material is 450 nm to 1100 nm.

16. A solar cell encapsulation comprising a resin in which a solar wavelength conversion material is dispersed, wherein the solar wavelength conversion material is the solar wavelength conversion material according to any one of claims 1 to 15.

17. The encapsulation of claim 16, wherein the encapsulation is in the form of a film with a thickness of less than 100 μm.

18. The encapsulation of claim 16, wherein the encapsulation is ethylene vinyl acetate, a polyolefin elastomer, a cross-linked polyolefin, a thermoplastic polyurethane, polyvinyl butyral, a silicone, a silicone / polyurethane hybrid, or an ionomer.

19. The encapsulation of claim 16, wherein the solar wavelength conversion material is included in an amount of 0.0001 to 10 parts by weight based on 100 parts by weight of the resin of the encapsulation.

20. A solar cell comprising a solar wavelength conversion material at an interface between an encapsulation located on a front surface of the solar cell where sunlight is incident and the solar cell, wherein the solar wavelength conversion material is the solar wavelength conversion material of any one of claims 1 to 15.

21. The solar cell of claim 20, wherein the solar wavelength conversion material is coated on the front surface of the solar cell or on the rear surface of the encapsulation on the front surface of the solar cell.

22. The solar cell of claim 21, wherein the coating is spray coating or screen coating.

23. The solar cell of claim 20, wherein the encapsulant of the solar cell is ethylene vinyl acetate, polyolefin elastomer, cross-linked polyolefin, thermoplastic polyurethane, polyvinyl butyral, organosilicon, organosilicon / polyurethane hybrid, or ionomer.

24. A solar cell, wherein the encapsulation of claim 16 is laminated on the front and rear surfaces of the solar cell, glass is laminated on the front surface of the encapsulation located on the front surface of the solar cell, and a backsheet is laminated on the rear surface of the encapsulation located on the rear surface of the solar cell.

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