CdTe power generation glass and preparation method thereof

Abstract

The present invention relates to the field of solar cell technology, and discloses a CdTe power generation glass and a preparation method thereof. The power generation glass structure includes an ultra-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. In the activation process of the power generation layer, a fluorine source is used instead of a chlorine source, which solves the problem of uneven activation caused by uneven coating of the chlorine source. The improvement of activation uniformity improves battery efficiency and stability. A mass flow meter is used to control the amount of fluorinated gas introduced, and the fluorinated gas is directly introduced into the activation equipment to facilitate the control of gas distribution uniformity, thereby ensuring the uniform distribution of the fluorinated source. The combination of compressed air and a high-power fan can conveniently control the flow direction of the fluorinated gas and the proportion of the atmosphere, thereby improving the uniformity of film activation and avoiding product appearance problems caused by excessive activation, which meets the requirements of BIPV products.

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, multi-functional," green, energy-saving, and energy-generating 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 capable of generating electricity. CdTe solar cells are typically 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 manufacturing process of CdTe thin films, lattice mismatch and a large number of grain boundaries are inevitably present within the crystals. Photogenerated carriers will recombine at these grain boundaries and at defect recombination centers formed by some impurities, thereby reducing the minority carrier lifetime and causing rapid degradation of cell performance.

[0003] Currently, high-temperature activation is a commonly used technical means to passivate grain boundary defects in CdTe films. This involves placing the CdTe film in a chlorine atmosphere, heating it to a very high temperature for a period of time, and then rapidly cooling it (chlorine annealing) to achieve recrystallization and orderly distribution of the CdTe grains, thereby reducing the number of grain boundaries.

[0004] On the other hand, due to the high work function of CdTe material, direct contact between CdTe and metal electrodes produces relatively large resistance, resulting in low battery output power. A heavily doped back contact layer is usually inserted between CdTe and the metal electrode to reduce contact resistance. However, the dopant ions generally have strong migration capabilities and will diffuse into the battery, forming defect recombination centers and causing rapid battery degradation. To this end, the diffusion of dopant ions can be suppressed by increasing the thickness of the CdTe film layer.

[0005] However, for CdTe film layers that are 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 above the power generation layer is converted into chlorinated gas in a high-temperature environment, providing 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. Uneven activation is prone to occur, that is, insufficient activation and excessive activation coexist, 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] In order to solve the above technical problems, the present invention provides a CdTe power generation glass and a preparation method thereof, which uses a fluorine source instead of a chlorine source to activate the power generation layer, improves the activation uniformity of the power generation film layer, reduces over-activation, and further improves battery efficiency.

[0007] To achieve this technical purpose, the present invention adopts the following scheme:

[0008] In a first aspect, the present invention provides a CdTe power generation glass, the power generation glass structure comprising an ultra-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.

[0009] Furthermore, the light transmittance of ultra-clear float glass is above 93% and the thickness is 3.2mm;

[0010] The transparent conductive layer (TCO) is one of FTO (SnO2:F), AZO (ZnO:Al) or ITO (In2O3:Sn), with a thickness of 300~400nm;

[0011] The power generation layer material is CdS / CdTe or CdSe x Te 1-x , CdS / CdTe thickness is 3-5μm; CdSe x Te 1-x The thickness is 3-5 μm, where x is 0.025~0.04;

[0012] The material of the back contact layer is ZnTe:Ag y Cu 1-y , the film thickness is 12±1nm;

[0013] The back electrode layer is a conductive film composed of three layers of molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel, with a total thickness of 200-400nm.

[0014] Furthermore, the power generation layer is activated by fluorine annealing. The specific activation method is: fluorinated gas and compressed air (CDA) are introduced into the activation furnace, the gas flow rate is controlled by a mass flow meter (MFC), and the gas flow direction and the proportion of the fluorinated gas atmosphere in the activation furnace are controlled by a high-power fan. The fluorinated gas flow rate is 500~1000sccm, and the compressed air flow rate is 1000~1500sccm; the temperature curve of the activation furnace is set as: rapidly heating to 440~450℃ at a heating rate of 32±0.5℃ / min, then maintaining 440~450℃ for 23±1min, and finally rapidly cooling to room temperature.

[0015] Preferably, the fluorination gas flow rate is 650-800 sccm, the compressed air flow rate is 1200-1300 sccm, the fan frequency is 30-50 Hz, and the tail exhaust pressure difference is 250-350 Pa.

[0016] Furthermore, the fluorinated gas is one or more of hydrofluorocarbon (HFC), perfluorocarbon (PFC), sulfur hexafluoride (SF6), HF vapor, NF3 and gas from combustion of fluoropolymer; the fluoropolymer material is one or more of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE).

[0017] In a second aspect, the present invention provides a method for preparing the aforementioned CdTe power generation glass, comprising the following steps:

[0018] Growing a transparent conductive layer on the ultra-clear float glass layer, wherein the growing method comprises at least one of a magnetron sputtering method and a chemical vapor deposition method;

[0019] The power generation layer is prepared by close-space sublimation method, with a deposition pressure of 7±0.2Pa and a coating temperature of 500-550℃, followed by fluorine annealing to activate the power generation layer;

[0020] The back contact layer and the back electrode layer are prepared by magnetron sputtering to obtain CdTe power generation glass.

[0021] Furthermore, after fluorine annealing and activation, the power generation layer is etched using a hydrochloric acid solution with a concentration of 11mS to make the surface of the film layer smooth.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention adopts a fluorine source instead of a chlorine source, thereby solving the problem of uneven activation caused by uneven coating amount of the chlorine source. The improvement of activation uniformity improves battery efficiency and stability.

[0024] The use of a mass flow meter facilitates the control of the amount of fluorinated gas introduced, and the direct introduction of fluorinated gas into the activation equipment facilitates the control of gas distribution uniformity, thereby ensuring uniform distribution of the fluorine source. Combining compressed air (CDA) and a high-power fan can conveniently control the flow direction of the fluorinated gas and the proportion of the atmosphere, thereby improving the uniformity of film activation and avoiding product appearance problems caused by excessive activation (i.e., obvious water ripples when viewed outdoors), meeting the requirements of BIPV products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the power generation glass in an embodiment of the present invention.

[0026] Figure 2 These are the light decay results of CdTe cells under different conditions in the embodiments of the present invention. DETAILED DESCRIPTION

[0027] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments, but the present invention is not limited thereto.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0029] The present invention provides a CdTe power generation glass and a preparation method thereof, see Figure 1 The CdTe power generation glass structure consists of a stacked, bottom-up layer of ultra-clear float glass, a transparent conductive layer (TCO), a power generation layer, a back contact layer, and a back electrode layer. The power generation layer is activated by fluorine annealing. By sequentially laying lead / bus bars, a POE film + butyl adhesive edge sealant, and tempered back glass on the power generation glass, a cell module is encapsulated and can be used in photovoltaic power plants, photovoltaic curtain walls, and other applications.

[0030] The transmittance of ultra-clear float glass is above 93% and its thickness is 3.2mm.

[0031] The transparent conductive layer (TCO) is one of FTO (SnO2:F), AZO (ZnO:Al) or ITO (In2O3:Sn), with a thickness of 300~400nm; it is prepared by at least one method of magnetron sputtering and chemical vapor deposition.

[0032] The power generation layer material is CdS / CdTe or CdSe x Te 1-x , CdS / CdTe thickness is 3-5μm; CdSe x Te 1-x The thickness is 3-5μm, where x is 0.025~0.04; the power generation layer is prepared by the near-space sublimation method, the deposition pressure is 7±0.2Pa, the coating temperature is 500-550℃, and then fluorine annealing is performed to activate the power generation layer.

[0033] To passivate the grain boundary defects in the power generation layer, the power generation layer requires annealing and activation. The specific activation method is to introduce fluorinated gas into the activation furnace, with the gas flow controlled by a mass flow meter (MFC). At the same time, compressed air (CDA) is introduced. A high-power fan controls the gas flow direction and the proportion of the fluorinated gas atmosphere in the activation furnace. The fluorinated gas flow rate is 500-1000sccm, and the compressed air flow rate is 1000-1500sccm. The activation furnace temperature curve is set as follows: rapidly increase the temperature to 440-450°C at a heating rate of 32±0.5°C / min, then maintain 440-450°C for 23±1min, and finally rapidly cool to room temperature. The fluorinated gas is one or more of hydrofluorocarbon (HFC), perfluorocarbon (PFC), sulfur hexafluoride (SF6), HF vapor, NF3 and gas from combustion of fluoropolymer; the fluoropolymer material is one or more of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE).

[0034] Preferably, the fluorination gas flow rate is 650-800 sccm, the compressed air flow rate is 1200-1300 sccm, the fan frequency is 30-50 Hz, and the tail exhaust pressure difference is 250-350 Pa.

[0035] After fluorine annealing and activation, the power generation layer is etched with a hydrochloric acid solution with a concentration of 11mS to make the film surface smooth and prevent the power generation layer from piercing the thinner back contact layer and directly contacting the back electrode layer.

[0036] The material of the back contact layer is ZnTe:Ag y Cu 1-y The film thickness is 12±1nm and is prepared by magnetron sputtering.

[0037] The first trench P1 is laser-scribed using a 355nm laser to cut the transparent conductive layer / power generation layer / back contact layer into strips of equal width, 5-10mm. The first trench P1 is then filled with insulating glue using photolithography.

[0038] The second channel P2 is laser-scribed using a laser with a wavelength of 532nm. The power generation layer / back contact layer is cut into sub-strips of equal width of 5~10mm at intervals of 60~90μm based on P1.

[0039] The back electrode layer is a three-layer composite conductive film of molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel, with a total thickness of approximately 200-400nm. It fills the second channel P2 and is connected in series with the transparent conductive layer. Molybdenum nitride / aluminum / chromium / nickel are all produced using an integrated magnetron sputtering device. Molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel are deposited sequentially on the back contact layer to form a three-layer composite conductive film. The process gas for molybdenum nitride is a mixture of nitrogen and argon with a flow ratio of 3:7 to 5:5. The process gas for aluminum / chromium / nickel is argon.

[0040] The third channel P3 is laser-scribed using a laser with a wavelength of 532nm. The power generation layer / back contact layer / back electrode layer is cut into sub-strips of equal width of 5~10mm at intervals of 60~90μm based on P2.

[0041] The rapid thermal annealing (RTA) process is used to optimize the back contact layer and the back electrode layer. The power generation glass is quickly heated to 248~250℃, maintained for 28 minutes, and then quickly cooled to room temperature.

[0042] The fourth channel P4 is used to laser or mechanically clean the four edges of the power generation glass. The cleaning width is 9~11mm. On the one hand, it provides an insulating substrate for the butyl rubber coating. On the other hand, it ensures that the power generation area of ​​the power generation glass is isolated from the external environment to prevent pollution of the power generation area.

[0043] The above is a complete process for preparing photovoltaic glass. Subsequently, the photovoltaic glass is sequentially laid with lead / bus bars, a POE film + butyl adhesive edge sealant, and tempered back glass to form a cell module for use in photovoltaic power plants, photovoltaic curtain walls, and other applications.

[0044] The lead / bus bars will be bonded to the back electrode layers on both sides in sequence to lead the current out through the holes in the tempered glass.

[0045] POE film + butyl rubber edge sealing layer, butyl rubber edge sealing mainly plays the role of edge waterproofing, POE's main function is to bond the power generation glass and the tempered back glass into one; the width of butyl rubber is 10mm~12mm, the thickness is 0.5mm, and the thickness of POE film is 0.76mm; tempered glass plays a supporting and protective role for the power generation glass.

[0046] The present invention will be further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally determined in accordance with national standards. Where no corresponding national standards are available, the methods were performed in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0047] Examples 1-4

[0048] Aside from the activation step for the power generation layer, the CdTe power generation glass structure, preparation method, and CdTe cell assembly in Examples 1-4 are identical. Examples 1-4 utilize a fluorine annealing process to activate the power generation layer. Specific parameters and differences are shown in Table 1. In Table 1, #1 represents Example 1, #2 represents Example 2, #3 represents Example 3, and #4 represents Example 4.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that a chlorine annealing process is used to activate the power generation layer, and the CdCl2 concentration is 600g / L. See Table 2, where 0# in Table 2 is Comparative Example 1.

[0051] Table 1

[0052] 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

[0053] Table 2

[0054] Group <![CDATA[CdCl2 concentration]]> 0# 600g / L

[0055] The output power of the CdTe cells prepared in Examples 1-4 and Comparative Example 1 was tested using a functional tester (FUCH). The test conditions were the current international standard test conditions. The output power (Pm) and other electrical performance parameters of the CdTe cells 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.

[0056] Table 3

[0057] 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

[0058] Given that the performance parameters of solar products themselves change slowly, it is difficult to obtain sufficient performance data in a short period of time. In order to obtain the performance changes of solar cells during long-term outdoor use, manufacturers usually use simulated sunlight to irradiate solar cells with high intensity and adopt accelerated aging experiments with high temperatures to measure their performance parameters accordingly. 2 The standard irradiance was continuously irradiated, and the ambient temperature in the light decay box was kept at 75°C to compare the change trend of CdTe cell output power over time under different conditions. The results are shown in Figure 2 .

[0059] This application controls the gas flow direction and the proportion of fluorinated gas atmosphere in the activation furnace by adjusting the fluorinated gas flow, compressed air flow and high-power fan speed. Chlorine annealing (CdCl2 concentration 600g / L) is used as the basic process. There are five groups of control conditions, such as Figure 2As shown in the figure, the horizontal axis is the accumulated light decay time, and the vertical axis represents the maximum output power Pm that the CdTe cell can achieve after a period of light decay testing. Among them, the Pm corresponding to 0h is the initial power obtained by testing the CdTe cell using a functional tester (FUCH).

[0060] Through comparative experiments, the preferred fluorination gas flow rate in this application is 650-800 sccm, and the compressed air flow rate is 1200-1300 sccm. Due to the characteristics of CdTe cells themselves, after a period of illumination, the cell output power increases significantly, and then gradually decreases as the illumination time increases. Therefore, this application uses light decay testing to accelerate the decay of the cell to characterize the service life of the CdTe cell. If the fluorination gas flow rate is too low (less than 650 sccm), for example, when the fluorination gas flow rate in condition 4 is 500 sccm, the fluorination atmosphere accounts for too low a proportion (1 / 3) and insufficient activation, resulting in too low initial cell power. After illumination, the cell output power is long-term lower than other conditions. If the fluorination gas flow rate is too high (greater than 800 sccm), for example, when the fluorination gas flow rate in condition 1 is 1000 sccm, the fluorination atmosphere accounts for too high a proportion (1 / 1) and excessive activation causes the cell to decay too quickly after illumination. After 30 hours of light decay testing, the cell Pm dropped to 309.67W, a decay of 2.89%. For condition 2, when the fluorine gas flow rate is controlled at around 800 sccm, the fluorine gas atmosphere accounts for 2 / 3, and the battery Pm remains at a high level for a long time. After 30 hours of light decay testing, the battery Pm drops to 326.62W, attenuating only 0.28%, making it the optimal condition.

[0061] After 10 hours of illumination, the average power of fluorine annealing was significantly higher than that of chlorine annealing. Chlorine annealing can easily lead to uneven activation or even over-activation during high-temperature activation, which can reduce the battery's power generation performance and accelerate decay. For example, in condition 0#, the initial power of the battery was similar to that of fluorine annealing, but the Pm decayed too quickly after illumination. After 30 hours of light decay testing, the battery Pm dropped to 291.132W, a decay of 2.88%.

[0062] Finally, it should be noted that the above-listed embodiments are merely preferred embodiments of the present invention. Of course, those skilled in the art may 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 their equivalents, they should be considered to be within the scope of protection of the present invention.

Claims

1. A CdTe power generation glass, characterized in that: The power generation glass structure includes an ultra-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; the power generation layer uses a fluorine source instead of a chlorine source for fluorine annealing activation, and the specific activation method is: introducing fluorine gas and compressed air into the activation furnace, and controlling the gas flow direction and the proportion of fluorine gas atmosphere in the activation furnace by adjusting the fluorine gas flow, compressed air flow and high-power fan speed. The fluorine gas flow is 500~1000sccm, and the compressed air flow is 1000~1500sccm; the activation furnace temperature curve is set as: rapidly heating to 440~450℃ at a heating rate of 32±0.5℃ / min, then maintaining 440~450℃ for 23±1min, and finally rapidly cooling to room temperature.

2. The CdTe power generation glass according to claim 1, characterized in that: Ultra-clear float glass has a light transmittance of over 93% and a thickness of 3.2mm; The transparent conductive layer is one of FTO, AZO or ITO, with a thickness of 300~400nm; The power generation layer material is CdS / CdTe or CdSexTe1-x, the thickness of CdS / CdTe is 3-5μm; the thickness of CdSexTe1-x is 3-5μm, where x is 0.025~0.04; The material of the back contact layer is ZnTe:AgyCu1-y, and the film thickness is 12±1nm; The back electrode layer is a conductive film composed of three layers of molybdenum nitride / aluminum / chromium or molybdenum nitride / aluminum / nickel, with a total thickness of 200-400nm.

3. The CdTe power generation glass according to claim 1, characterized in that: The fluorination gas flow rate is 650~800sccm, and the compressed air flow rate is 1200-1300sccm.

4. The CdTe power generation glass according to claim 1, characterized in that: The fluorinated gas is one or more of hydrofluorocarbon, perfluorocarbon, sulfur hexafluoride, HF vapor, NF3 and gas from combustion of fluoropolymer; the fluoropolymer material is one or more of polyvinyl fluoride, polyvinylidene fluoride and polytetrafluoroethylene.

5. A method for preparing CdTe power generation glass according to any one of claims 1 to 4, characterized in that: The following steps are involved: Growing a transparent conductive layer on the ultra-clear float glass layer, wherein the growing method comprises at least one of a magnetron sputtering method and a chemical vapor deposition method; The power generation layer is prepared by close-space sublimation method, with a deposition pressure of 7±0.2Pa and a coating temperature of 500-550℃; then fluorine annealing is performed to activate the power generation layer; The back contact layer and the back electrode layer are prepared by magnetron sputtering to obtain CdTe power generation glass.

6. The method for preparing CdTe power generation glass according to claim 5, characterized in that: After fluorine annealing and activation, the power generation layer is etched with a hydrochloric acid solution with a concentration of 11mS to make the surface of the film smooth.

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