CdTe power generation glass and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, and discloses CdTe power generation glass and a preparation method thereof.The power generation glass structurally comprises an ultra-white float glass layer, a transparent conductive layer, a power generation layer, a back contact layer and a back electrode layer which are sequentially stacked from bottom to top; in the power generation layer activation process, a fluorine source is adopted to replace a chlorine source, the problem of non-uniform activation caused by non-uniform coating amount of the chlorine source is solved, and the improvement of the activation uniformity improves the efficiency and the stability of the battery. The mass flow meter is adopted to control the introduction amount of the fluorinated gas, the fluorinated gas is directly introduced into the activation equipment to conveniently control the gas distribution uniformity, so that the uniform distribution of a fluorine source is ensured, the flow direction of the fluorinated gas and the atmosphere proportion can be conveniently controlled by combining compressed air and a high-power fan, the activation uniformity of a film layer is improved, and the service life of the film layer is prolonged. Product appearance problems caused by excessive activation are avoided, and the requirements of BIPV products are met.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a CdTe power generation glass and a preparation method thereof. Background Art

[0002] Cadmium telluride (CdTe) power generation glass is a "one material, multiple functions", green, energy-saving, and energy-creating energy-based building material. It is made of ordinary glass covered with cadmium telluride photovoltaic materials. This material can transform ordinary glass from an insulator into a solar cell that can generate electricity. CdTe solar cells are usually multi-layer thin film stacks containing CdTe thin films and other functional thin film materials. The quality of the CdTe thin film crystals directly determines the power generation performance and service life of the entire solar cell. During the production process of CdTe thin films, there will inevitably be lattice mismatch and a large number of grain boundaries inside the crystals. Photogenerated carriers will recombine at these grain boundaries and defect recombination centers formed by some impurities, thereby reducing the minority carrier lifetime and causing rapid degradation of battery performance.

[0003] At present, high-temperature activation is a commonly used technical means to passivate grain boundary defects in CdTe films. That is, the CdTe film is placed in a chlorine atmosphere and heated to a very high temperature for a period of time and then rapidly cooled (chlorine annealing) to achieve recrystallization and orderly distribution of CdTe grains and reduce the number of grain boundaries.

[0004] On the other hand, due to the high work function of CdTe materials, direct contact between CdTe and metal electrodes will produce relatively large resistance, resulting in low battery output power. Usually, a back contact layer that can achieve heavy doping is inserted between CdTe and the metal electrode to reduce the contact resistance, but the doped ions generally have strong migration ability and will diffuse into the battery to form defect recombination centers, causing rapid battery attenuation. For this reason, the diffusion of doped ions can be suppressed by increasing the thickness of the CdTe film layer.

[0005] However, for a CdTe film layer that is too thick, a higher activation temperature is required. The existing technology usually uses a chemical water bath or chemical coating method to coat a CdCl2 aqueous solution on the power generation layer, and then transfers it to an activation furnace for high-temperature annealing. The CdCl2 on the power generation layer is converted into chlorinated gas in a high-temperature environment to provide a chlorine source for high-temperature activation. Since the uniformity of the chemical water bath or chemical coating method is difficult to control, the coating amount in different areas of the power generation layer varies greatly, resulting in difficulty in controlling the gas distribution and atmosphere ratio during the high-temperature activation process, and uneven activation is prone to occur, that is, insufficient activation and excessive activation exist at the same time, which in turn leads to reduced battery power generation performance and accelerated attenuation. In addition, products with uneven activation have obvious water ripple morphology when viewed outdoors, which does not meet the color difference requirements of BIPV products. Summary of the invention

[0006] To solve the above technical problems, the present invention provides a CdTe power generation glass and a preparation method thereof. A fluorine source is used to replace the chlorine source to activate the power generation layer, improve the activation uniformity of the power generation film layer, reduce over-activation, and further improve the battery efficiency.

[0007] To achieve this technical purpose, the present invention adopts the following solutions: In a first aspect, the present invention provides a CdTe power generation glass. The structure of the power generation glass includes a super-white float glass layer (glass), a transparent conductive layer (TCO), a power generation layer, a back contact layer, and a back electrode layer stacked in sequence from bottom to top; wherein the power generation layer is activated by fluorine annealing.

[0008] Further, the light transmittance of the super-white float glass is above 93%, and the thickness is 3.2 mm; The transparent conductive layer (TCO) is one of FTO (SnO2:F), AZO (ZnO:Al), or ITO (In2O3:Sn), and the thickness is 300 - 400 nm; The material of the power generation layer is CdS / CdTe or CdSe x Te 1-x , the thickness of CdS / CdTe is 3 - 5 μm; CdSe x Te 1-x The thickness is 3 - 5 μm, where x is 0.025 - 0.04; The material of the back contact layer is ZnTe:Ag y Cu 1-y , and the film layer thickness is 12 ± 1 nm; The back electrode layer is a conductive thin film composed of a three-layer composite of molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel, and the total thickness is 200 - 400 nm.

[0009] Further, the power generation layer is activated by fluorine annealing. The specific activation method is as follows: Introduce a fluorinated gas and compressed air (CDA) into the activation furnace, control the gas flow through a mass flow meter (MFC), and at the same time control the gas flow direction and the proportion of the fluorinated gas atmosphere in the activation furnace through a high-power blower. The fluorinated gas flow is 500 - 1000 sccm, and the compressed air flow is 1000 - 1500 sccm; the temperature curve of the activation furnace is set as follows: rapidly heat up to 440 - 450 °C at a heating rate of 32 ± 0.5 °C / min, then maintain 440 - 450 °C for 23 ± 1 min, and finally rapidly cool to room temperature.

[0010] Preferably, the fluorinated gas flow is 650 - 800 sccm, and the compressed air flow is 1200 - 1300 sccm. The blower frequency is 30 - 50 Hz, and the tail exhaust pressure difference is 250 - 350 Pa.

[0011] Further, the fluorinated gas is one or more of hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), HF vapor, NF3, and gases from the combustion of fluoropolymers; the fluoropolymer material is one or more of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polychlorotrifluoroethylene (PCTFE).

[0012] In a second aspect, the present invention provides a method for preparing the CdTe power generation glass described above, comprising the following steps: Growing a transparent conductive layer on the ultra-clear float glass layer, and the growth method includes at least one of magnetron sputtering and chemical vapor deposition; Preparing a power generation layer by the close space sublimation method, with a deposition pressure of 7 ± 0.2 Pa and a coating temperature of 500 - 550 °C, and then annealing and activating the power generation layer with fluorine; Preparing a back contact layer and a back electrode layer by magnetron sputtering to obtain the CdTe power generation glass.

[0013] Further, after annealing and activating with fluorine, the power generation layer is etched with a hydrochloric acid solution with a concentration of 11 mS to make the film surface flat.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses a fluorine source to replace the chlorine source, solving the problem of uneven activation caused by uneven coating amount of the chlorine source. The improvement of activation uniformity improves the battery efficiency and stability.

[0015] Using a mass flow meter facilitates the control of the flow rate of the fluorinated gas. Directly introducing the fluorinated gas into the activation equipment facilitates the control of the gas distribution uniformity, thereby ensuring the uniform distribution of the fluorine source. Combining compressed air (CDA) and a high-power blower can conveniently control the flow direction and atmosphere ratio of the fluorinated gas, thereby improving the activation uniformity of the film layer and avoiding product appearance problems caused by over-activation (i.e., obvious water ripple morphology can be visually observed outdoors), meeting the requirements of BIPV products. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the structure of the power generation glass in the embodiment of the present invention.

[0017] Figure 2 It is the light decay result of CdTe cells under different conditions in the embodiment of the present invention. Detailed Embodiments

[0018] To fully understand the purpose, features, and effects of the present invention, the present invention will be described in detail through the following specific embodiments, but the present invention is not limited thereto.

[0019] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or prepared by existing methods.

[0020] The present invention provides a CdTe power generation glass and a preparation method. Refer to Figure 1 , the structure of the CdTe power generation glass includes a super-white float glass layer (glass), a transparent conductive layer (TCO), a power generation layer, a back contact layer, and a back electrode layer stacked in sequence from bottom to top; wherein the power generation layer is activated by fluorine annealing. By sequentially laying busbars / collecting bars, a POE film + butyl rubber edge sealing layer, and a tempered backplate glass on the power generation glass, a battery module is encapsulated, which can be used in scenarios such as photovoltaic power stations and photovoltaic curtain walls.

[0021] The light transmittance of the super-white float glass is above 93%, and the thickness is 3.2 mm.

[0022] The transparent conductive layer (TCO) is one of FTO (SnO2:F), AZO (ZnO:Al), or ITO (In2O3:Sn), with a thickness of 300 - 400 nm; it is prepared by at least one of magnetron sputtering and chemical vapor deposition.

[0023] The material of the power generation layer is CdS / CdTe or CdSe x Te 1-x , the thickness of CdS / CdTe is 3 - 5 μm; CdSe x Te 1-x The thickness is 3 - 5 μm, where x is 0.025 - 0.04; the power generation layer is prepared by the close-spaced sublimation method, the deposition pressure is 7 ± 0.2 Pa, the coating temperature is 500 - 550 °C, and then the power generation layer is activated by fluorine annealing.

[0024] To passivate the grain boundary defects of the power generation layer, the power generation layer needs to be annealed and activated. The specific activation method is: introduce a fluorinated gas into the activation furnace, control the gas flow through a mass flow controller (MFC), and at the same time introduce compressed air (CDA), control the gas flow direction and the proportion of the fluorinated gas atmosphere in the activation furnace through a high-power blower. The fluorinated gas flow is 500 - 1000 sccm, and the compressed air flow is 1000 - 1500 sccm. The temperature curve of the activation furnace is set as: rapidly heat up to 440 - 450 °C at a heating rate of 32 ± 0.5 °C / min, then maintain at 440 - 450 °C for 23 ± 1 min, and finally rapidly cool to room temperature. The fluorinated gas is one or several of hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), HF vapor, NF3, and gases from the combustion of fluoropolymers; the fluoropolymer material is one or several of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polychlorotrifluoroethylene (PCTFE).

[0025] Preferably, the flow rate of the fluorinated gas is 650 - 800 sccm, the flow rate of the compressed air is 1200 - 1300 sccm, the frequency of the fan is 30 - 50 Hz, and the differential pressure at the tail exhaust is 250 - 350 Pa.

[0026] After fluorine annealing activation, a hydrochloric acid solution with a concentration of 11 mS is used to etch the power generation layer to make the film surface flat and prevent the power generation layer from piercing through the thinner back contact layer and directly contacting the back electrode layer.

[0027] The material of the back contact layer is ZnTe:Ag y Cu 1-y , the film thickness is 12 ± 1 nm, and it is prepared by magnetron sputtering.

[0028] For the first channel P1 laser scribing, a laser with a wavelength of 355 nm is used to cut the transparent conductive layer / power generation layer / back contact layer into equally wide sub-long strips with a width of 5 - 10 mm. Insulating glue is filled in the first channel P1 through photolithography technology.

[0029] For the second channel P2 laser scribing, a laser with a wavelength of 532 nm is used to cut the power generation layer / back contact layer into equally wide sub-long strips with a width of 5 - 10 mm at an interval of 60 - 90 μm based on P1.

[0030] The back electrode layer is a conductive thin film composed of a triple-layer composite of molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel, with a total thickness of about 200 - 400 nm. It fills the second channel P2 and is connected in series with the transparent conductive layer. Molybdenum nitride / aluminum / chromium / nickel are all prepared by an integrated magnetron sputtering device. Molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel are deposited on the back contact layer in sequence, and finally a triple-layer composite conductive film layer is formed. Among them, the process gas for molybdenum nitride is a mixed gas of nitrogen and argon, and the flow ratio is 3:7 - 5:5. The process gases for aluminum / chromium / nickel are all argon.

[0031] For the third channel P3 laser scribing, a laser with a wavelength of 532 nm is used to cut the power generation layer / back contact layer / back electrode layer into equally wide sub-long strips with a width of 5 - 10 mm at an interval of 60 - 90 μm based on P2.

[0032] The rapid thermal annealing process (RTA) is used to optimize the back contact layer and the back electrode layer. The power generation glass is quickly heated to 248 - 250 °C, held for 28 minutes, and then quickly cooled to room temperature.

[0033] For the fourth channel P4, the four sides of the power generation glass are cleared by laser or mechanical means, and the edge clearing width is 9 - 11 mm. On the one hand, it provides an insulating substrate for butyl rubber coating, and on the other hand, it ensures the isolation of the power generation area of the power generation glass from the external environment and prevents pollution of the power generation area.

[0034] The above are the complete steps for fabricating the power - generating glass. Subsequently, by sequentially laying busbars / collecting bars, a POE film + butyl rubber edge - sealing layer, and a tempered back - plate glass on the power - generating glass, it is encapsulated into a battery module, which can be used in scenarios such as photovoltaic power stations and photovoltaic curtain walls.

[0035] The busbars / collecting bars will be sequentially bonded to the back - electrode layers on both sides, and the current will be led out through the holes in the tempered glass.

[0036] For the POE film + butyl rubber edge - sealing layer, the butyl rubber edge - seals, mainly playing a role in edge waterproofing. The main role of the POE is to bond the power - generating glass and the tempered back - plate glass into one body; the width of the butyl rubber is 10 mm - 12 mm, the thickness is 0.5 mm, and the thickness of the POE film is 0.76 mm; the tempered glass plays a role in supporting and protecting the power - generating glass.

[0037] Next, in combination with specific embodiments, the present invention will be further elaborated. For the experimental methods without specific conditions noted in the following embodiments, they are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0038] Examples 1 - 4 Except for the activation step of the power - generating layer, the structures of the CdTe power - generating glass, the preparation methods, and the assembly of the CdTe battery in Examples 1 - 4 are the same. Examples 1 - 4 use a fluorine annealing process to activate the power - generating layer. The specific parameters and differences are shown in Table 1. In Table 1, 1# is Example 1, 2# is Example 2, 3# is Example 3, and 4# is Example 4.

[0039] Comparative Example 1 The difference from Example 1 is that a chlorine annealing process is used to activate the power - generating layer, and the CdCl2 concentration is 600 g / L. See Table 2, where 0# is Comparative Example 1.

[0040] Table 1 Group Fluorine flow rate (sccm) CDA flow rate (sccm) Flow ratio 4# 500 1500 1 / 3 3# 650 1300 1 / 2 2# 800 1200 2 / 3 1# 1000 1000 1 / 1 Table 2 Group <![CDATA[CdCl2 concentration]]> 0# 600 g / L A function tester (FUCH) is used to test the output power of the CdTe batteries prepared in Examples 1 - 4 and Comparative Example 1. The test conditions are the current international standard test conditions. The output power (Pm) and other electrical performance parameters of the CdTe batteries under different conditions are shown in Table 3. In Table 3, 1# is Example 1, 2# is Example 2, 3# is Example 3, 4# is Example 4, and 0# is Comparative Example 1.

[0041] Table 3 Group Pm Isc Voc Rs Rsh FF 4# 268.91 2.259 181.46 21.04 1385.55 0.657 3# 272.48 2.27 180.62 20.44 1650.68 0.664 2# 276.42 2.27 180.68 20.08 1761.54 0.674 1# 271.31 2.266 180.69 20.04 1691.29 0.662 0# 272.45 2.264 182.26 18.66 1796.23 0.662 Given the slow change of the performance parameters of solar products themselves, it is difficult to obtain sufficient performance data in a very short time. In order to obtain the performance change of solar cells during long-term outdoor use, production enterprises usually simulate sunlight to irradiate solar cells with high intensity and conduct accelerated aging experiments by applying higher temperatures to measure their performance parameters accordingly. In this patent, the CdTe cell is placed in a light attenuation chamber and irradiated continuously with a standard irradiance of 1000W / m 2 while keeping the ambient temperature in the light attenuation chamber at 75°C all the time to compare the change trend of the output power of the CdTe cell with time under different conditions. The results are shown in Figure 2 .

[0042] In this application, the gas flow direction and the proportion of the fluorinated gas atmosphere in the activation furnace are controlled by adjusting the flow rate of the fluorinated gas, the flow rate of the compressed air and the rotation speed of the high-power fan. Taking chlorine annealing (CdCl2 concentration 600g / L) as the basic process, there are a total of five groups of control conditions, as shown in Figure 2 . The abscissa is the cumulative light attenuation duration, and the ordinate represents the maximum output power Pm that the CdTe cell can reach after a period of light attenuation test. Among them, the Pm corresponding to 0h is the initial power obtained by testing the CdTe cell with a function tester (FUCH).

[0043] Through comparative experiments, the preferred flow rate of the fluorinated gas in this application is 650 - 800 sccm, and the flow rate of the compressed air is 1200 - 1300 sccm. Due to the characteristics of the CdTe cell itself, after a period of light irradiation, the output power of the cell increases significantly and then gradually decreases with the increase of the light irradiation time. Therefore, in this application, the service life of the CdTe cell is characterized by accelerating the attenuation of the cell through light attenuation test. If the flow rate of the fluorinated gas is too low (less than 650 sccm), for example, when the flow rate of the fluorinated gas in condition 4# is 500 sccm, the proportion of the fluorine gas atmosphere is too low (1 / 3), and the activation is insufficient, resulting in too low initial power of the cell. After light irradiation, the output power of the cell is less than that of other conditions for a long time. And if the flow rate of the fluorinated gas is too high (more than 800 sccm), for example, when the flow rate of the fluorinated gas in condition 1# is 1000 sccm, the proportion of the fluorine gas atmosphere is too high (1 / 1), and the over-activation causes the cell to decay too fast after light irradiation. After 30 hours of light attenuation test, the Pm of the cell drops to 309.67W, with a decay of 2.89%. For condition 2# where the flow rate of the fluorinated gas is controlled at about 800 sccm, the proportion of the fluorinated gas atmosphere is 2 / 3, and the Pm of the cell remains at a relatively high level for a long time. After 30 hours of light attenuation test, the Pm of the cell drops to 326.62W, with only a decay of 0.28%. Therefore, it is the optimal condition.

[0044] After 10 hours of light exposure, the average power of fluorine annealing is significantly higher than that of chlorine annealing. For chlorine annealing, during the high-temperature activation process, uneven activation or even over-activation is likely to occur, which in turn leads to a decrease in the power generation performance of the battery and an accelerated attenuation. For example, under condition 0#, the initial power of the battery is similar to that of fluorine annealing, but the Pm decays too fast after light exposure. After 30 hours of light attenuation test, the Pm of the battery drops to 291.132W, with an attenuation of 2.88%.

[0045] Finally, it should be noted that the above-listed are only the preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and its equivalent technologies, they should be considered within the protection scope of the present invention.

Claims

1. A CdTe power generation glass, characterized in that, The structure of the power generation glass includes a super white float glass layer, a transparent conductive layer, a power generation layer, a back contact layer, and a back electrode layer stacked in sequence from bottom to top; among them, the power generation layer is activated by fluorine annealing.

2. The CdTe power generation glass according to claim 1, wherein The light transmittance of the super white float glass is above 93%, and the thickness is 3.2 mm; The transparent conductive layer is one of FTO, AZO, or ITO, and the thickness is 300 - 400 nm; The material of the power generation layer is CdS / CdTe or CdSe x Te 1-x , the thickness of CdS / CdTe is 3 - 5 μm; CdSe x Te 1-x has a thickness of 3 - 5 μm, where x is 0.025 to 0.04; The material of the back contact layer is ZnTe:Ag y Cu 1-y , and the film thickness is 12 ± 1 nm; The back electrode layer is a conductive thin film composed of a molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel triple-layer composite, and the total thickness is 200 - 400 nm.

3. The CdTe power generation glass according to claim 1, wherein The power generation layer is activated by fluorine annealing. The specific activation method is as follows: introduce a fluorinated gas and compressed air into the activation furnace, control the gas flow through a mass flow meter, and at the same time control the gas flow direction and the proportion of the fluorinated gas atmosphere in the activation furnace through a high-power blower. The flow rate of the fluorinated gas is 500 - 1000 sccm, and the flow rate of the compressed air is 1000 - 1500 sccm; the temperature curve of the activation furnace is set as follows: rapidly heat up to 440 - 450 °C at a heating rate of 32 ± 0.5 °C / min, then maintain 440 - 450 °C for 23 ± 1 min, and finally rapidly cool to room temperature.

4. The CdTe power generation glass according to claim 3, wherein The flow rate of the fluorinated gas is 650 - 800 sccm, and the flow rate of the compressed air is 1200 - 1300 sccm.

5. The CdTe power generation glass according to claim 3 or 4, characterized in that, The fluorinated gas is one or several of hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, HF vapor, NF3, and gases from the combustion of fluoropolymers; the fluoropolymer material is one or several of polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, and polyvinyl trichloride.

6. The preparation method of the CdTe power generation glass according to any one of claims 1-5, characterized in that, It includes the following steps: Grow the transparent conductive layer on the super white float glass layer, and the growth method includes at least one of magnetron sputtering and chemical vapor deposition; Prepare the power generation layer by the near-space sublimation method, with a deposition pressure of 7 ± 0.2 Pa and a coating temperature of 500 - 550 °C; then activate the power generation layer by fluorine annealing; Prepare the back contact layer and the back electrode layer by magnetron sputtering to obtain CdTe power generation glass.

7. The preparation method of the CdTe power generation glass according to claim 6, wherein, After fluorine annealing activation, etch the power generation layer with a hydrochloric acid solution with a concentration of 11 mS to make the film surface flat.

Images