A benzoxazole-based short-wavelength light-converting material and its short-wavelength light-converting adhesive film

Abstract

This invention provides a class of short-wavelength light-converting materials based on benzoxazole, with the structure shown in Formula I, where R1 and R2 are each independently hydrogen atoms, C1-C18 straight-chain or branched alkyl groups; and R3 is an aryl group or a substituted aryl group. The short-wavelength light-converting material of this invention possesses advantages such as excellent short-wavelength ultraviolet light absorption, high luminous quantum efficiency, good photostability, low cost, and ease of mass production. When doped at a certain concentration into the encapsulating film of solar cells, it can efficiently absorb short-wavelength ultraviolet light to avoid UVID (ultraviolet-induced power degradation), and convert the absorbed short-wavelength ultraviolet light into long-wavelength ultraviolet or blue-violet light that can be efficiently utilized by solar cells, thereby increasing power generation. This is of great significance for improving the overall performance and economic benefits of photovoltaic modules.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module encapsulation film technology, and more specifically, to a benzoxazole-based short-wave light conversion material and its short-wave light conversion film. Background Technology

[0002] In recent years, solar cells have seen continuous efficiency improvements through technological advancements. With the ongoing development of solar cell technology, the most promising technologies for crystalline silicon cells currently include TOP-Con (top-contact, tunneling oxide passivated contact) cells, HJT (heterojunction) cells, and BC (back contact) cells. However, most existing high-efficiency solar cells employ silicon hydrogenation passivation technology, which is susceptible to damage from ultraviolet radiation in sunlight. This damage can lead to the breakage of Si-H bonds within the cell, a significant decrease in hydrogen content, and an increase in interface defect density. Consequently, the open-circuit voltage and fill factor of the cell decrease, ultimately resulting in power degradation.

[0003] To address the UVID (power degradation caused by ultraviolet aging) phenomenon in photovoltaic modules, there are currently two main technical solutions: one is to add a UV cut-off agent (absorbing ultraviolet light below 320nm) to the module encapsulation film to reduce the damage of ultraviolet radiation to the cells; the other is to add a light conversion agent to the module encapsulation film, which can convert ultraviolet light of 300-360nm into near-ultraviolet or blue-violet light that can be absorbed and utilized by the cells.

[0004] However, existing technical solutions still have some problems: On the one hand, while simply adding UV blockers can reduce the damage of ultraviolet radiation to the solar cells, ultraviolet light energy is wasted, resulting in a significant decrease in power generation compared to high-transmittance solutions; on the other hand, the conversion band of existing light conversion agents is mainly 300-360nm, but their blocking effect on short-wave ultraviolet light (280-300nm) is limited. Furthermore, for TOP-Con and BC modules, excessively long light conversion bands (e.g., exceeding 340nm) can actually reduce the module's power generation efficiency (because the power generation efficiency of long-wave ultraviolet light conversion is lower than the power generation efficiency of the solar cells themselves).

[0005] Therefore, developing a material that can efficiently absorb short-wavelength ultraviolet light (280-340nm) and efficiently convert the absorbed short-wavelength ultraviolet light into long-wavelength ultraviolet or blue-violet light is of great significance for improving the overall performance and economic benefits of solar cells. Summary of the Invention

[0006] This invention aims to provide a novel short-wave ultraviolet light conversion material, which is a type of small organic molecule material based on benzoxazole. It can convert short-wave ultraviolet light and improve the power generation of solar cells. It has the advantages of excellent short-wave ultraviolet light absorption rate, high luminous efficiency, good photostability, low price and easy mass production. It can be used as a short-wave ultraviolet light conversion material in the encapsulation film of solar cells, which can improve the service life and power of solar cells.

[0007] Specifically, the technical solution of the present invention is as follows:

[0008] A class of benzoxazole-based short-wavelength light-converting materials, with the structure shown in Formula I, wherein: R1 and R2 are each independently hydrogen atoms, C1-C18 straight-chain or branched alkyl groups; R3 is an aryl group or a substituted aryl group.

[0009]

[0010] Formula I

[0011] Preferably, R1 and R2 are methyl, ethyl, n-butyl, isobutyl, tert-butyl, n-octyl, n-dodecyl, n-hexadecyl, or n-octadecyl. Different alkyl substituents can adjust the physicochemical properties of the material, such as solubility, melting point, and optical properties, thereby meeting the needs of different application scenarios.

[0012] Preferably, the aryl group in R3 is phenyl or biphenylnaphthyl; the substituent is further represented by R4, and the substitution position of R4 is arbitrary and not fixed. R4 is preferably a halogen, C1-C18 alkyl, halogen-substituted alkyl, alkoxy, ester, cyano, hydroxyl, carboxyl, amide, acyloxy, C1-C6 alkenyl, or combinations thereof, as shown in the following structures:

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0020] The choice of the R3 aryl group has a significant impact on the optical properties of the material. Different aromatic substituents can adjust the absorption wavelength and emission wavelength of the material, thereby optimizing the short-wave ultraviolet light cutoff performance and light conversion efficiency of the material.

[0021] Preferably, R3 is phenyl, 4-biphenyl, 2-biphenyl, or 2-naphthyl.

[0022] Preferably, in R3, the biphenyl and naphthyl groups are 4'-biphenyl and 2-naphthyl.

[0023] Preferably, in R4, the substituted aryl group is 4-tert-butylphenyl, 4-fluorophenyl, 4-methoxyphenyl, 3,5-di-tert-butylphenyl, 4-tert-butylbiphenyl, 4-fluorobiphenyl, 4-methoxybiphenyl, or 3,5-di-tert-butylbiphenyl.

[0024] Preferably, R3 is 4-tert-butylphenyl, 4-fluorophenyl, 4-methoxyphenyl, or 3,5-di-tert-butylphenyl.

[0025] The technical solution of the present invention also includes a short-wave light-converting film, wherein the short-wave light-converting film is a composite material formed by the benzoxazole-based short-wave light-converting material and a polymer resin.

[0026] In the short-wavelength light-converting film, the doping concentration of the benzoxazole-based short-wavelength light-converting material in the composite is 0.01%-1%. Preferably, the doping concentration of the benzoxazole-based short-wavelength light-converting material in the composite is 0.1%-0.5%.

[0027] The choice of doping concentration is crucial to the performance of the material. When the doping concentration is below 0.01%, the absorption of short-wave ultraviolet light is not significant, and the protection effect on the solar cell is limited. When the doping concentration is above 1%, although the absorption of short-wave ultraviolet light is enhanced, it will lead to a decrease in the transmittance of the encapsulant film, affecting the overall power generation efficiency of the solar cell. Therefore, a doping concentration range of 0.01%-1% can ensure the absorption of short-wave ultraviolet light without significantly affecting the transmittance of the encapsulant film.

[0028] In the short-wavelength light-converting adhesive film, the polymer resin is selected from one or more of POE (polyolefin elastomer), EVA (ethylene-vinyl acetate copolymer), PVB (polyvinyl butyral), and silicone gel. These resin materials have good light transmittance, weather resistance, and processing performance, and are well compatible with benzoxazole-based small organic molecule materials to form a uniform composite material.

[0029] Preferably, the thickness of the short-wavelength light-converting film is 100µm-600µm. More preferably, the thickness of the short-wavelength light-converting film is 200µm-500µm. The selection of the film thickness needs to comprehensively consider factors such as mechanical strength, light transmittance, and cost. When the film thickness is less than 100µm, the mechanical strength is insufficient, and it is easily damaged during the manufacturing and use of solar cell modules; when the film thickness is greater than 600µm, although the mechanical strength is improved, the material cost increases, and it may affect the light transmittance. Therefore, a thickness range of 100µm-600µm can ensure mechanical strength while balancing light transmittance and cost.

[0030] The benzoxazole-based short-wavelength light-converting material of the present invention has a suitable conjugated system, a rigid planar structure and high photoluminescence efficiency, while also having high optical and thermal stability, maintaining stable performance during long-term use.

[0031] The benzoxazole-based short-wavelength light-converting material and the short-wavelength light-converting film prepared therefrom can efficiently absorb high-energy short-wavelength ultraviolet light below 340nm, protecting photovoltaic modules from damage caused by high-energy short-wavelength ultraviolet light and effectively improving the service life and reliability of solar cell modules. At the same time, it can convert short-wavelength ultraviolet light into near-ultraviolet or visible light that can be absorbed and utilized by solar cells, thereby increasing the power generation of solar cells. Attached Figure Description

[0032] Figure 1 These are the transmittance spectra of light-transfer films A and B in Example 8 of this invention.

[0033] Figure 2 These are the fluorescence emission spectra of light-transfer films A and B in Example 8 of this invention.

[0034] Figure 3 This is an EQE curve diagram of the ultraviolet cutoff film, long-wave light-converting film, light-converting film A, and light-converting film B in Example 9 of the present invention. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1:

[0037] Benzooxazole-based short-wavelength optical conversion material A with the structure shown in Formula II:

[0038]

[0039] Formula II

[0040] Add 5.4g (1.0 eq) of 2-amino-4-tert-butylphenol, 7g (1.2 eq) of 4-tert-butylbenzoic acid, and 0.49g (0.1 eq) of boric acid catalyst to a reaction vessel. Add 35ml of trichlorobenzene and 50ml of toluene to the vessel, start stirring, fill the water separator with toluene, replace with N2, protect with N2, start heating, 150℃ for 3h, continuously separate water during the process, 220℃ for 3h.

[0041] Trichlorobenzene was removed by vacuum distillation, dissolved in dichloromethane, and then decolorized with 5% activated carbon. Recrystallization from dichloromethane and methanol yielded 8.71 g of a white powder (86.5% yield). Mass spectrometry: [MS+H] + 308.79, 1H-NMR (400MHz, CDCl3) (ppm) δ = 1.36-1.39 (18H, m), 7.38-7.41 (1H, m), 7.47-7.54 (3H, m), 7.79-7.80 (1H, m), 8.15-8.18 (2H, m).

[0042] Example 2:

[0043] Benzooxazole-based short-wavelength optical conversion material B with the structure shown in Formula III:

[0044]

[0045] Formula III

[0046] The synthesis steps for Formula III are the same as those for Formula II, except that 4-tert-butylbenzoic acid is replaced with 4-phenylbenzoic acid. 8.54 g of white powder was collected, with a yield of 79.7%. Mass spectrometry: [MS+H] + 328.61, 1H-NMR (400MHz, CDCl3) (ppm) δ = 1.41 (9H, s), 7.37-7.51 (5H, m), 7.65-7.82 (5H, m), 8.30-8.32 (2H, m).

[0047] Example 3:

[0048] The benzoxazole-based short-wavelength light-converting material C with the structure shown in Formula IV is synthesized.

[0049]

[0050] Formula IV

[0051] The synthesis steps for Formula IV are the same as those for Formula II, except that 4-tert-butylbenzoic acid is replaced with 2-phenylbenzoic acid. 8.65 g of white powder was collected, with a yield of 80.7%. Mass spectrometry: [MS+H] +328.62, 1H-NMR (400MHz, CDCl3) (ppm) δ = 1.36 (9H, s), 7.17-7.19 (1H, m), 7.25-7.33 (6H, m), 7.47-7.51 (2H, m), 7.55-7.59 (1H, m), 7.72-7.73 (1H, m), 8.08-8.10 (1H, m).

[0052] Example 4:

[0053] The benzoxazole-based short-wavelength optical conversion material D with the structure shown in formula V:

[0054]

[0055] Formula V

[0056] The synthesis steps for material V are the same as for material II, except that 4-tert-butylbenzoic acid is replaced with 4-benzoic acid. 6.84 g of white powder was collected, with a yield of 83.1%. Mass spectrometry: [MS+H] + 252.56, 1H-NMR (400MHz, CDCl3) (ppm) δ = 1.39 (9H, s), 7.40-7.42 (1H, m), 7.48-7.52 (4H, m), 7.80-7.82 (1H, m), 8.23-8.26 (2H, m).

[0057] Example 5:

[0058] The benzoxazole-based short-wavelength optical conversion material E with the structure shown in formula VI:

[0059]

[0060] Formula VI

[0061] The synthesis steps for Formula VI are the same as those for Formula II, except that 4-tert-butylbenzoic acid is replaced with 4-fluorobenzoic acid. 7.12 g of white powder was collected, with a yield of 80.8%. Mass spectrometry: [MS+H] + 270.42, 1H-NMR (400MHz, CDCl3) (ppm) δ = 1.38 (9H, s), 7.18-7.25 (2H, m), 7 .39-7.42(1H,m), 7.47-7.49(1H,m), 7.77-7.78(1H,m), 8.21-8.25(1H,m).

[0062] Example 6: Spectral property testing of materials:

[0063] The absorption spectrum of the solution and the transmittance of the visible region of the film (T, 400-700 nm, calculated average) were measured using a PerkinElmer Lambda750 UV-Vis spectrophotometer with an integrating sphere. The excitation and emission spectra (Ex, Em) and fluorescence quantum efficiency (PLQY) were measured using a Tianmei FLS 1000 fluorescence spectrometer.

[0064] The spectral properties of materials A / B / C / D / E from Examples 1-5 in dichloromethane solution were tested and are shown in Table 1. Maximum absorption wavelength, maximum emission wavelength, and fluorescence quantum efficiency were tested with a 0.005% w / w DCM solution; fluorescence quantum efficiency was tested with a 0.1% w / w PMMA 400µm film.

[0065] Table 1. Spectroscopic properties of materials A / B / C / D / E in dichloromethane solution and PMMA membrane.

[0066]

[0067] a: Tested in a 0.005% w / w dichloromethane solution; b: Tested in a 0.1% w / w PMMA 400µm film.

[0068] It can be seen that the light-converting materials prepared in Examples 1-5 of this invention have an absorption peak range of 290-330 nm and an emission peak range of 340-380 nm. The fluorescence quantum efficiency is slightly low in dichloromethane solution, but the luminescence efficiency dispersed in PMMA polymer film can mostly reach more than 90%. This indicates that the light-converting materials of this invention have high fluorescence efficiency and strong wavelength conversion capability.

[0069] Example 7 Preparation of light-converting adhesive film

[0070] The short-wave light-converting material and EVA resin described in this invention are mixed at a mass ratio of 1:19 (with the addition of certain antioxidants and slip agents). The mixture is then melt-mixed using a twin-screw extruder, extruded, and granulated to obtain a masterbatch (material content 5%, w / w). The obtained masterbatch is then mixed with blank EVA particles at a mass ratio of 1:24, and crosslinking agents tert-butyl peroxide-3,5,5-trimethylhexanoate (0.5 wt%), trimethylolpropane triacrylate (0.3 wt%), and γ-glycidyl etheroxypropyltrimethoxysilane (0.3 wt%) are added. The light stabilizer bis(1,2,2,6,6-pentamethylpiperidinol) sebate (0.4 wt%) is also added. The mixture is then melt-mixed using a twin-screw extruder and then cast to form a uniform polymer film, thus obtaining the light-converting film.

[0071] Formula 1, EVA film, light-converting material A from Example 1, thickness 500um, material content 0.08% w / w, the resulting light-converting film is denoted as light-converting film A.

[0072] Formula 2, POE film, light-converting material B from Example 2, added at 0.1% w / w, with a thickness of 400 μm, the resulting light-converting film is denoted as light-converting film B.

[0073] Formula 3, silicone gel film, light-converting material E from Example 5, added at 0.12% w / w, with a thickness of 400 μm, the resulting light-converting film is denoted as light-converting film E.

[0074] Comparative Example 1:

[0075] Preparation of UV-blocking EVA film:

[0076] The preparation method is the same as in Example 7, except that the light-converting material is replaced with commercially available ultraviolet absorber UV326 (structural formula shown in Formula VII), the amount of UV326 added is 0.1% w / w, and the thickness of the EVA film is 400 μm, thus obtaining an ultraviolet-blocking EVA film.

[0077]

[0078] Formula VII

[0079] Comparative Example 2:

[0080] Preparation of long-wavelength light-converting EVA film:

[0081] The preparation method is the same as in Example 7, except that the short-wave light conversion material is replaced with long-wave light conversion material B1 (the structural formula is shown in Formula VIII). The amount of B1 added is 0.1% w / w, and the EVA film thickness is 400 μm to obtain a long-wave light conversion film.

[0082]

[0083] Formula VIII

[0084] Example 8: Film Spectroscopy Test

[0085] The testing equipment used is the same as in Example 6.

[0086] The transmittance spectra of light-converting films A and B are as follows: Figure 1 As shown, the emission spectrum is as follows Figure 2 As shown.

[0087] from Figure 1 and Figure 2As can be seen, the transmittance of light-converting film A in the ultraviolet region below 325nm is less than 1%, while the transmittance in the visible and near-infrared regions of 400nm-700nm is higher than 87%. This indicates that the film can completely absorb high-energy short-wave ultraviolet light below 325nm. Furthermore, the fluorescence emission emitted by the film under ultraviolet irradiation is mainly concentrated in the wavelength range of 320nm-410nm; and the fluorescence quantum efficiency is as high as 97%.

[0088] The transmittance of the light-converting film B in the ultraviolet region below 345nm is less than 1%, while the transmittance in the visible and near-infrared regions of 400nm-700nm is higher than 91%. This indicates that the film can completely absorb high-energy short-wavelength ultraviolet light below 345nm. Furthermore, the fluorescence emission emitted by the film under ultraviolet irradiation is mainly concentrated in the wavelength range of 350nm-450nm; the tested fluorescence quantum efficiency is as high as 99%.

[0089] The transmittance of UV-blocking EVA film in the UV light region below 370nm is less than 1%, but the film has no fluorescence emission and no light conversion function, resulting in a waste of UV light energy.

[0090] The long-wavelength light-converting EVA film has a transmittance of less than 1% in the ultraviolet light region below 370nm, can absorb ultraviolet light below 370nm, and has a maximum emission wavelength of 420nm; the fluorescence quantum efficiency is 94%.

[0091] Example 9: Testing of Photovoltaic Modules

[0092] The EVA light-converting films A and B prepared in Example 7, the UV-cutoff film of Comparative Example 1, and the long-wavelength light-converting film of Comparative Example 2 were used to encapsulate TOP-Con modules. The encapsulation structure, from bottom to top, consisted of ultra-clear tempered glass, light-converting film / cutoff film, a heterojunction solar cell array welded in series and parallel, a regular film, and ultra-clear tempered glass. The measured power output of the modules corresponding to the four types of films are shown in Table 2.

[0093] Table 2. Component power corresponding to the four types of adhesive films

[0094]

[0095] As shown in Table 2, based on the power of the UV-cut-off encapsulant film, the power of the long-wave light-conversion encapsulant film is increased by 0.35%, and the power of light-conversion encapsulants A and B are increased by 0.78% and 0.52%, respectively. This also indicates that the solution of the present invention has a superior power improvement effect on photovoltaic modules.

[0096] Analysis of the reasons:

[0097] The external quantum efficiency (EQE) curves of the four films in the 300nm-1100nm wavelength range were tested, as follows: Figure 3As shown. The larger the EQE, the higher the photoelectric conversion efficiency of the solar cell for incident light in that wavelength band.

[0098] To protect TOPCon solar cells from UV damage, the UV-blocking film absorbs incident UV light and converts it entirely into heat energy. As a result, the EQE of the corresponding modules below 370nm is almost zero, resulting in a loss of UV light energy and thus lower power output.

[0099] Due to waveguide factors, the maximum EQE of the light-converting film is approximately 65%. The long-wavelength light-converting film has light-converting function, and its EQE is greater than that of the UV-cut-off film. The measured module power is greater than that of the UV-cut-off film. The light-converting film B has a greater EQE in the 350-370nm band than the long-wavelength light-converting film, and its measured module power is greater than that of the long-wavelength light-converting film. The light-converting film A has a greater EQE in the 320-350nm band than the light-converting film B, and its measured module power is greater than that of the light-converting film B.

[0100] Light-converting films A and B can completely absorb high-energy short-wave ultraviolet light below 325nm and 345nm, protecting photovoltaic modules from damage caused by high-energy short-wave ultraviolet rays and effectively improving the lifespan and reliability of solar cell modules. At the same time, their fluorescence emission is in the 320-450nm range, which coincides with the photoelectric conversion sensitive region of solar cells, and their fluorescence quantum efficiencies are all greater than 95%, which is beneficial to improving the photoelectric conversion efficiency of solar cells, thereby increasing cell power. This is of great significance for improving the overall performance and economic benefits of solar cells.

[0101] The benzoxazole-based short-wavelength light-converting material and the short-wavelength light-converting film prepared therefrom can efficiently absorb high-energy short-wavelength ultraviolet light below 340nm, protecting photovoltaic modules from damage caused by high-energy short-wavelength ultraviolet light and effectively improving the service life and reliability of solar cell modules. At the same time, it can convert short-wavelength ultraviolet light into near-ultraviolet or visible light that can be absorbed and utilized by solar cells, thereby increasing the power generation of solar cells.

[0102] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical principles disclosed in the present invention, such as using hydrolytic enzymes from other sources with similar specificity, or making equivalent substitutions for the chromatographic packing materials and conditions in the purification step, should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A benzoxazole-based short-wavelength light-converting material, characterized in that, The structure of the short-wavelength light-converting material is shown in Formula I, where: R1 and R2 are each independently hydrogen atoms, C1-C18 straight-chain or branched alkyl groups; R3 is an aryl group or a substituted aryl group; Formula I.

2. The benzoxazole-based short-wavelength light-converting material as described in claim 1, characterized in that, R1 and R2 are methyl, ethyl, n-butyl, isobutyl, tert-butyl, n-octyl, n-dodecyl, n-hexadecyl, and n-octadecyl.

3. The benzoxazole-based short-wavelength light-converting material as described in claim 1, characterized in that, R3 is phenyl, 4-biphenyl, 2-biphenyl, or 2-naphthyl.

4. The benzoxazole-based short-wavelength light-converting material as described in claim 1, characterized in that, R3 is 4-tert-butylphenyl, 4-fluorophenyl, 4-methoxyphenyl, or 3,5-di-tert-butylphenyl.

5. A short-wavelength light-converting adhesive film, characterized in that, The short-wave light-converting film is a composite material formed by the benzoxazole-based short-wave light-converting material of claim 1 and a polymer resin.

6. The short-wavelength light-converting adhesive film as described in claim 5, characterized in that, In the short-wavelength light-converting film, the doping concentration of benzoxazole-based short-wavelength light-converting materials in the composite is 0.01%-1%.

7. The short-wavelength light-converting adhesive film as described in claim 5, characterized in that, In the short-wavelength light-converting film, the doping concentration of benzoxazole-based short-wavelength light-converting materials is 0.1%-0.5%.

8. The short-wavelength light-converting adhesive film as described in claim 5, characterized in that, In the short-wavelength light-converting adhesive film, the polymer resin is selected from one or more of polyolefin elastomers, ethylene-vinyl acetate copolymers, polyvinyl butyral, and silicone gel.

9. The short-wavelength light-converting adhesive film as described in claim 5, characterized in that, The thickness of the short-wavelength optical conversion film is 100um-600um.

10. The short-wavelength light-converting adhesive film as described in claim 9, characterized in that, The thickness of the short-wavelength light-converting film is 200um-500um.

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