A method for preparing low-cost ultra-high reflectivity microcrystalline photovoltaic glass ink without pre-nuclear heat treatment

Abstract

The present invention discloses a method for preparing a low-cost, ultra-high reflectivity microcrystalline photovoltaic glass ink that does not require pre-nuclear heat treatment. The method comprises the following steps: Step 1: Using CaCl2, Ti(OC4H9)4, H2O, and C2H6O as raw materials, the raw materials are dissolved, mixed, and added to a reactor according to a formula, and a metastable CaTi2O5 nanopowder is synthesized by a one-step hydrothermal method. Step 2: According to a glass flux formula, the raw materials are mixed, melted, and cooled to obtain a ZnO-B2O3-SiO2 glass frit, which is then ball-milled and passed through a 250-mesh sieve to obtain a low-melting-point glass powder. Step 3: The low-melting-point glass powder, inorganic filler, varnish, and CaTi2O5 nanopowder are mixed in proportion, ground, and passed through a 250-mesh sieve to obtain the glass ink. The glass ink prepared by this method is printed on a glass substrate using a 200-mesh screen and sintered to produce an inorganic high-reflectivity coating with good acid resistance and adhesion.

Description

Technical Field

[0001] The present invention relates to the technical field of glass inks, and in particular to a method for preparing low-cost ultra-high reflectivity microcrystalline photovoltaic glass ink that does not require pre-nuclear heat treatment. Background Art

[0002] With the continuous development of photovoltaic technology, solar energy, as an environmentally friendly new energy source, has significantly superior application advantages over other renewable energy sources such as wind and tidal energy. Photovoltaic power generation technology utilizes the photovoltaic effect generated by solar energy at the interface of semiconductors to achieve efficient conversion of light energy into electrical energy. Currently, photovoltaic power generation systems widely use double-glass photovoltaic modules, which are generally composed of front glass, back glass, and solar cells. To further improve the efficiency of photovoltaic modules in utilizing sunlight, a high-reflectivity coating is required on the surface of the back glass to enhance the power generation efficiency of the solar cells, thereby achieving the goals of reducing costs and improving performance.

[0003] High-reflectivity coatings on photovoltaic glass backsheets efficiently reflect sunlight back onto the solar cell surface, significantly improving the photovoltaic conversion efficiency of solar cells and serving as a key technological tool for enhancing module performance. PV glass backsheet coatings can be categorized as inorganic or organic, depending on the type of binder. Organic coatings are susceptible to UV rays, heat, moisture, and chemicals, leading to aging, degradation, or loss of adhesion. This poor long-term stability limits their practical application. In contrast, the binder in inorganic coatings is typically composed of stable inorganic low-melting-point glass, which offers high thermal stability, UV resistance, and chemical resistance, maintaining excellent performance in harsh environments such as high temperature, humidity, and UV rays. Therefore, current commercial development and research in high-reflectivity coatings for photovoltaic backsheets primarily focuses on inorganic coatings. These inorganic coatings primarily consist of a low-temperature inorganic glass flux (binder), TiO2 (filler), and varnish. They are tempered simultaneously with the glass substrate at approximately 600°C and then solidified upon cooling. The reflectivity of inorganic coatings prepared using conventional processes typically hovers around 75%, leaving room for improvement. To improve the reflectivity of inorganic coatings, costly methods such as pre-nuclear heat treatment of low-temperature inorganic glass fluxes or the addition of expensive microcrystal inducers are often used to precipitate tiny crystals within the glass flux, thereby enhancing the coating's light reflectivity. These improvements can also improve the chemical stability of the inorganic coating, further enhancing the power generation efficiency and long-term stability of photovoltaic modules. Chinese patent CN114455853B discloses an inorganic coating for photovoltaic backsheets. By adding 20-40% (mass fraction) of Bi2O3 as a microcrystal inducer, Bi2Ti2O7 microcrystals with a diameter of 5-1000 nm are precipitated within the coating, achieving a maximum reflectivity of 80% for the coating ink. However, the Bi2O3 raw material is expensive, produces toxic gases during thermal decomposition, and the precipitation and size of Bi2Ti2O7 crystals are easily affected by temperature and process factors. Consequently, its practical application is limited by cost, environmental concerns, and stability considerations. Chinese patent CN117326797A discloses a pre-nucleated microcrystalline glass powder for high-reflectivity inorganic coatings on photovoltaic backsheets and its preparation method. By adding a small amount of ZrO2, a microcrystalline nucleating agent, to the glass flux formula, a pre-nucleation heat treatment is performed, consisting of an annealing treatment at 450-500°C for 1-2 hours and a microcrystallization heat treatment at 650-720°C for 0.5-2 hours. This causes tiny Zn2SiO4 crystals to precipitate from the glass flux. These crystals fill the pores of the TiO2 filler particles, significantly improving the coating's density and reducing light transmittance, thereby achieving a reflectivity as high as 88.7%. Furthermore, the precipitated Zn2SiO4 crystals enhance the coating's acid resistance and adhesion. However, this method requires a complex pre-nucleation heat treatment process, and the crystal precipitation and size are highly sensitive to heat treatment conditions, making it difficult to consistently obtain ideal Zn2SiO4 microcrystals. Summary of the Invention

[0004] In order to overcome the problems of the prior art, the present invention provides a method for preparing low-cost ultra-high reflectivity microcrystalline photovoltaic glass ink which is low-cost, simple in process, suitable for large-scale production and does not require pre-nuclear heat treatment.

[0005] The technical solution of the present invention is: a method for preparing a low-cost ultra-high reflectivity microcrystalline photovoltaic glass ink without pre-nuclear heat treatment, characterized by comprising the following steps:

[0006] Step 1: Using CaCl2, Ti(OC4H9)4, H2O, and C2H6O as raw materials, according to the formula, they are dissolved, mixed, and added into a reactor to synthesize metastable CaTi2O5 nanopowder through a one-step hydrothermal method;

[0007] Step 2: According to the glass flux formula, the raw materials are mixed, melted, and cooled to obtain ZnO-B2O3-SiO2 glass frit, and the obtained glass frit is crushed and ball-milled and then passed through a 250 mesh sieve to obtain low-melting-point glass powder;

[0008] Step 3: Mix low-melting-point glass powder, inorganic filler, varnish and CaTi2O5 nanopowder in proportion, grind them and pass them through a 250-mesh sieve to obtain glass ink.

[0009] The formula molar ratio of the metastable CaTi2O5 nanopowder synthesized in the step 1 is: CaCl2:Ti(OC4H9)4:H2O:C2H6O=1:1~2:40~50:10~20, and the size range of the powder is 70~120nm.

[0010] In the step 1, the pH value in the reactor is 5-6, the hydrothermal reaction temperature is 160-200° C., and the reaction time is 24-48 h.

[0011] The formula of the glass flux in the step 2 is Na2O2~12mol / %, K2O0~4mol / %, BaO0~5mol / %, CaO0~6mol / %, ZnO30~50mol / %, B2O317~19mol / %, SiO216~43mol / %, and Al2O30~1mol / %.

[0012] The temperature of the melting process in step 2 is 1260-1320° C., and the melting time is 4-5 hours.

[0013] The thermal expansion coefficient of the low melting point glass powder in step 2 is α( 室温~300 ℃ ) is 5.43~9.32×10 -6 ℃, softening temperature T f It is 508~605℃.

[0014] The mass percentages of low-melting-point glass powder, inorganic filler, varnish and CaTi2O5 nanopowder in step three are: 50-68%, 15-30%, 15-30% and 2-4%; the inorganic filler is rutile titanium dioxide, and the varnish is an organic flux and resin.

[0015] The organic solvent is any one or more of turpentine, terpineol and n-octanol mixed evenly; the resin is any one of polyvinyl butyral, polyketone high hydroxy resin and epoxy resin.

[0016] The glass ink prepared in the step 3 is printed on a glass substrate by 200-mesh screen printing, and sintered together with a glass back plate at 700-750° C. for 100-180 seconds to prepare an inorganic high-reflectivity coating.

[0017] The reflectivity of the prepared inorganic high-reflectivity coating ranges from 93.2% to 96.8%.

[0018] The present invention has the following beneficial effects:

[0019] The present invention provides a high-reflectivity coating technology for microcrystalline photovoltaic glass with a simple preparation process, no need for pre-nuclear heat treatment, and strong operability. The glass flux has a stable thermal expansion coefficient, a low melting temperature, and is lead-free and bismuth-free, low-cost and environmentally friendly. At present, in order to obtain a high-reflectivity microcrystalline photovoltaic glass coating, the glass flux is usually subjected to a pre-nuclear heat treatment to promote the precipitation of microcrystals from the glass flux, thereby improving the reflectivity. However, this process consumes the components in the flux, destroys the stable structure of the glass flux, causes its cohesive force to drop sharply, and thus affects the adhesion of the coating. At the same time, the existing pre-nuclear heat treatment process lacks sufficient control during the microcrystal precipitation process, resulting in certain limitations on the stability of the coating and the inability to achieve long-term high-efficiency reflective performance. The technology of this invention introduces CaTi2O5 and evenly disperses it in the ZnO-B2O3-SiO2 glass flux, where it decomposes in situ to form fine and uniform rutile and anatase TiO2 crystallites. These in situ decomposed crystallites fill the pores of the titanium dioxide filler particles. This hybrid effect of multiple crystals achieves high performance, with a reflectivity of up to 96.8%. This ultra-high reflectivity is primarily due to the thermal decomposition of CaTi2O5 in the glass to produce crystallites with different crystalline structures, primarily due to the following effects:

[0020] 1. Multi-interface reflection effect: Due to the presence of rutile TiO2 (refractive index 2.70) and anatase TiO2 (refractive index 2.55) microcrystals, light is reflected multiple times at the microcrystal interface, and the superposition significantly enhances the overall reflectivity of the coating;

[0021] 2. Photon localization effect: The high and low refractive index regions formed in the microcrystalline structure cause photons to be localized, resulting in multiple reflections and interference, preventing light from penetrating the coating, similar to the light trapping effect in photonic crystals, thereby further improving reflection efficiency;

[0022] 3. Effective refractive index gradient effect: The distribution of microcrystals creates a gradually changing refractive index gradient. Light continuously encounters refractive index changes as it passes through the coating, significantly reducing light transmission and enhancing reflection. This mechanism is similar to the reflection phenomenon seen on butterfly wings or pearl surfaces.

[0023] In addition, the high-reflectivity coating of the present invention has excellent acid resistance, stability and high reflectivity, which not only effectively improves the power generation efficiency of photovoltaic modules, but also reduces the domestic dependence on imported photovoltaic glass inks. Therefore, it has significant strategic significance and economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The XRD patterns of the CaTi2O5 nanopowder at different calcination temperatures in Example 1 of the present invention are as follows;

[0025] Figure 2 This is the XRD pattern of the coating after sintering and cooling at 750°C for 120 seconds in Example 1;

[0026] Figure 3 This is an SEM image of the coating after sintering and cooling at 720°C for 180 seconds in Example 3;

[0027] Figure 4 This is a reflectivity test chart of the coating after sintering and cooling at 720°C for 180 seconds in Example 3;

[0028] Figure 5 This is a test diagram of photovoltaic glass ink adhesion in Example 2;

[0029] Figure 6 This is the appearance morphology of the photovoltaic glass ink of Example 2. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] Step 1: Synthesize metastable CaTi2O5 nanopowder using the formula of CaCl2:Ti(OC4H9)4:H2O:C2H6O=1:1:50:10;

[0033] Step 2: Using a hydrothermal temperature of 180°C, a holding time of 48 hours, and a pH value of 5.2, to synthesize metastable CaTi2O5 nanopowder with a powder size of 70 nm;

[0034] Step 3: Using Na2O4mol / %, K2O4mol / %, BaO5mol / %, CaO6mol / %, ZnO30mol / %, B2O319mol / %, SiO231mol / %, and Al2O31mol / % as a basic formula, all raw materials are mixed, melted at 1280°C for 4 hours using a high-temperature melting method, and cooled to obtain a glass frit;

[0035] Step 4: crush the glass frit and grind it through a 250 mesh sieve to obtain low melting point glass powder; the thermal expansion coefficient of the glass powder is α( 室温~300 ℃ )=8.13×10 -6 ℃, softening temperature T f =541℃;

[0036] Step 5: 50% low-melting-point glass powder, 30% inorganic filler, 17% varnish (turpentine + polyketone high-hydroxy resin), and 3% CaTi2O5 nanopowder were mixed and ground. The mixture was then screen-printed onto a glass substrate using a 200-mesh screen. Finally, the coating was sintered at 750°C for 120 seconds to produce an inorganic high-reflectivity coating. The ink's adhesion performance tested failed ISO Class 0, with a light reflectivity range of 93.9%. The ink showed no signs of cracking or flaking after acid resistance testing.

[0037] Figure 1 The results show that when the powder is not calcined and calcined at 650℃, it is mainly composed of CaTi2O5 crystals; when the calcination temperature reaches 750℃, the phase composition is transformed into anatase and rutile TiO2; and after calcination at 850℃, the phase is completely transformed into a single rutile TiO2.

[0038] Figure 2 It is shown in the figure that when CaTi2O5 nanopowder is not added, the phase composition of the coating is rutile TiO2; after adding CaTi2O5 nanopowder, the phase composition becomes a mixed structure of anatase and rutile TiO2.

[0039] Example 2

[0040] Step 1: Synthesize metastable CaTi2O5 nanopowder using the formula of CaCl2:Ti(OC4H9)4:H2O: C2H6O=1:1.5:40:20;

[0041] Step 2: using a hydrothermal temperature of 200°C, a holding time of 36 hours, and a pH value of 6 to synthesize metastable CaTi2O5 nanopowder with a powder size of 120 nm;

[0042] Step 3: Using Na2O12mol / %, K2O0mol / %, BaO1mol / %, CaO3mol / %, ZnO50mol / %, B2O317mol / %, SiO216mol / %, and Al2O31mol / % as the basic formula, all raw materials are mixed, melted at 1300°C for 4h by a high-temperature melting method, and cooled to obtain a glass frit;

[0043] Step 4: crush the glass frit and grind it through a 250 mesh sieve to obtain low melting point glass powder; the thermal expansion coefficient of the glass powder is α( 室温~300 ℃ )=9.32×10 -6 ℃, softening temperature T f =508℃;

[0044] Step 5: 55% low-melting-point glass powder, 26% inorganic filler, 15% varnish (n-octanol + polyvinyl butyral), and 4% CaTi2O5 nanopowder were mixed and ground. The mixture was then screen-printed onto a glass substrate using a 200-mesh screen. Finally, the sample was tempered at 700°C for 100 seconds to produce a photovoltaic glass ink. The ink's adhesion performance tested failed ISO grade 0, with a light reflectivity range of 93.2%. The ink showed no signs of cracking or flaking after acid resistance testing.

[0045] Figure 5 The test results show that its adhesion level reaches ISO standard level 0, showing excellent adhesion performance.

[0046] Figure 6 The coating surface is uniform and smooth, without visible defects, with high whiteness and excellent surface quality.

[0047] Example 3

[0048] Step 1: Synthesize metastable CaTi2O5 nanopowder using the formula of CaCl2:Ti(OC4H9)4:H2O:C2H6O=1:2:45:15;

[0049] Step 2: Synthesize metastable CaTi2O5 nanopowder at a hydrothermal temperature of 160°C, a holding time of 24 hours, and a pH value of 5.5. The powder size is 90 nm.

[0050] Step 3: Using Na2O5mol / %, K2O3mol / %, BaO3mol / %, CaO6mol / %, ZnO33mol / %, B2O317mol / %, SiO233mol / %, and Al2O30mol / % as the basic formula, all raw materials are mixed, melted at 1320°C for 4.5h by high-temperature melting method, and cooled to obtain a glass frit;

[0051] Step 4: crush the glass frit and grind it through a 200 mesh sieve to obtain low melting point glass powder; the thermal expansion coefficient of the glass powder is α( 室温~300 ℃ )=7.18×10 -6 ℃, softening temperature T f =526℃;

[0052] Step 5: 53% low-melting-point glass powder, 15% inorganic filler, 30% varnish (terpineol + epoxy resin), and 2% CaTi2O5 nanopowder were mixed and ground. The mixture was then screen-printed onto a glass substrate using a 200-mesh screen. Finally, the sample was tempered at 720°C for 180 seconds to produce a photovoltaic glass ink. The ink's adhesion performance tested failed ISO grade 0, with a light reflectivity range of 96.8%. The ink showed no signs of cracking or flaking after acid resistance testing.

[0053] Figure 3 It is shown in the figure that the coating is mainly composed of filler (rutile TiO2) with a size range of 500-2000 nm and anatase and rutile TiO2 microcrystals with a size of 100-150 nm, and the particles are evenly distributed.

[0054] Figure 4 The test included a comparison of the reflectivity of the coating without and with CaTi2O5 nanopowder. The results showed that the coating with CaTi2O5 nanopowder added had a higher reflectivity than the coating without, with the highest value reaching 96.8%.

[0055] Example 4

[0056] Step 1: Synthesize metastable CaTi2O5 nanopowder using the formula of CaCl2:Ti(OC4H9)4:H2O:C2H6O=1:1.5:40:20;

[0057] Step 2: Using a hydrothermal temperature of 180°C, a holding time of 36 hours, and a pH value of 5, synthesize metastable CaTi2O5 nanopowder with a powder size of 95 nm;

[0058] Step 3: Using Na2O10mol / %, K2O1mol / %, BaO2mol / %, CaO0mol / %, ZnO36mol / %, B2O318mol / %, SiO232mol / %, and Al2O31mol / % as the basic formula, all raw materials are mixed, melted at 1260°C for 5h by a high-temperature melting method, and cooled to obtain a glass frit;

[0059] Step 4: crush the glass frit and grind it through a 200 mesh sieve to obtain low melting point glass powder; the thermal expansion coefficient of the glass powder is α( 室温~300 ℃ )=5.43×10 -6 ℃, softening temperature T f =586℃;

[0060] Step 5: 68% low-melting-point glass powder, 15% inorganic filler, 15% varnish (terpineol + turpentine + polyketone high-hydroxy resin), and 2% CaTi2O5 nanopowder were mixed and ground. The mixture was then screen-printed onto a glass substrate using a 200-mesh screen. Finally, the sample was tempered at 730°C for 120 seconds to produce a photovoltaic glass ink. The ink's adhesion performance tested failed ISO grade 0, with a light reflectivity range of 94.5%. The ink showed no signs of cracking or flaking after acid resistance testing.

[0061] Example 5

[0062] Step 1: Synthesize metastable CaTi2O5 nanopowder using the formula of CaCl2:Ti(OC4H9)4:H2O:C2H6O=1:1.8:45:15;

[0063] Step 2: Using a hydrothermal temperature of 180°C, a holding time of 30 hours, and a pH value of 5.3, to synthesize metastable CaTi2O5 nanopowder with a powder size of 105 nm;

[0064] Step 3: Using Na2O2mol / %, K2O2mol / %, BaO0mol / %, CaO1mol / %, ZnO33mol / %, B2O318.2mol / %, SiO243mol / %, and Al2O30.8mol / % as the basic formula, all raw materials are mixed, melted at 1300°C for 5h by a high-temperature melting method, and cooled to obtain a glass frit;

[0065] Step 4: crush the glass frit and grind it through a 200 mesh sieve to obtain low melting point glass powder; the thermal expansion coefficient of the glass powder is α( 室温~300 ℃ )=7.36×10 -6 ℃, softening temperature T f =605℃;

[0066] Step 5: 55% low-melting-point glass powder, 25% inorganic filler, 16% varnish (terpineol + n-octanol + polyketone high-hydroxy resin), and 4% CaTi2O5 nanopowder were mixed and ground. The mixture was then screen-printed onto a glass substrate using a 200-mesh screen. Finally, the sample was tempered at 750°C for 100 seconds to produce a photovoltaic glass ink. The ink's adhesion performance tested failed ISO Class 0, with a light reflectivity range of 95.6%. The ink showed no signs of cracking or flaking after acid resistance testing.

[0067] The above embodiments are merely illustrative of the principles and effects of the present invention, as well as some embodiments of its application, and are not intended to limit the present invention. It should be noted that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing low-cost ultra-high reflectivity microcrystalline photovoltaic glass ink without pre-nuclear heat treatment, characterized in that The steps include: Step 1: Using CaCl2, Ti(OC4H9)4, H2O, and C2H6O as raw materials, according to the formula, they are dissolved, mixed, and added into a reactor to synthesize metastable CaTi2O5 nanopowder through a one-step hydrothermal method; Step 2: According to the glass flux formula, the raw materials are mixed, melted, and cooled to obtain ZnO-B2O3-SiO2 glass frit, and the obtained glass frit is crushed and ball-milled and then passed through a 250 mesh sieve to obtain low-melting-point glass powder; Step 3: Mix low-melting-point glass powder, inorganic filler, varnish and CaTi2O5 nanopowder in proportion, grind them and pass them through a 250-mesh sieve to obtain glass ink.

2. The preparation method according to claim 1, wherein: The formula molar ratio of the metastable CaTi2O5 nanopowder synthesized in the step 1 is: CaCl2: Ti(OC4H9)4: H2O: C2H6O=1: 1~2: 40~50: 10~20, and the size range of the CaTi2O5 nanopowder is 70~120nm.

3. The preparation method according to claim 1, wherein: In the step 1, the pH value in the reactor is 5-6, the hydrothermal reaction temperature is 160-200° C., and the reaction time is 24-48 hours.

4. The preparation method according to claim 1, wherein: The formula of the glass flux in the step 2 is Na2O2-12mol / %, K2O 0-4mol / %, BaO 0-5mol / %, CaO 0-6mol / %, ZnO 30-50mol / %, B2O3 17-19mol / %, SiO2 16-43mol / %, and Al2O3 0-1mol / %.

5. The preparation method according to claim 1, wherein: The temperature of the melting process in step 2 is 1260-1320° C., and the melting time is 4-5 hours.

6. The preparation method according to claim 1, wherein: The thermal expansion coefficient of the low melting point glass powder in step 2 is α( 室温~300 ℃ ) is 5.43~9.32×10 -6 ℃, softening temperature T f It is 508~605 ℃.

7. The preparation method according to claim 1, wherein: The mass percentages of low-melting-point glass powder, inorganic filler, varnish and CaTi2O5 nanopowder in step three are: 50-68%, 15-30%, 15-30% and 2-4%; the inorganic filler is rutile titanium dioxide, and the varnish is an organic flux and resin.

8. The preparation method according to claim 7, characterized in that: The organic solvent is any one or more of turpentine, terpineol and n-octanol mixed evenly; the resin is any one of polyvinyl butyral, polyketone high hydroxy resin and epoxy resin.

9. The preparation method according to claim 1, wherein: The glass ink prepared in the step 3 is printed on a glass substrate by 200-mesh screen printing, and sintered together with the glass substrate at 700-750° C. for 100-180 seconds to prepare an inorganic high-reflectivity coating.

10. The preparation method according to claim 9, characterized in that: The reflectivity of the prepared inorganic high-reflectivity coating ranges from 93.2% to 96.8%.

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