Device for detecting cadmium chloride film based on conductivity meter and detection method

Abstract

The invention provides a device for detecting a cadmium chloride thin film based on a conductivity meter and a detection method thereof, and relates to the field of solar thin film cells. Comprising a dissolving tank, a weight block and a sealing ring, the bottom of the dissolving tank is provided with a first opening which can be in contact with a cadmium chloride film, and the top of the dissolving tank is provided with a second opening through which a conductivity meter can enter and exit; the sealing ring is arranged at the first opening, and the weight bearing block is connected with the outer wall of the dissolving tank. The detection method comprises the following steps: adding quantitative deionized water into the dissolving tank, and testing the conductivity of liquid in the dissolving tank by using a conductivity meter after the cadmium chloride film in the dissolving tank is dissolved; the cadmium chloride concentration corresponding to the conductivity is calculated through a cadmium chloride concentration-conductivity curve graph, and the thickness of the cadmium chloride thin film at the sampling point is calculated based on the amount of deionized water added into the dissolving tank and the area of the cadmium chloride thin film in the dissolving tank; the device and the method are low in detection cost, short in time and high in precision.

Description

Technical Field

[0001] The present invention relates to the field of solar thin-film batteries, and more particularly, to an apparatus and a detection method for detecting cadmium chloride thin films based on a conductivity meter. Background Art

[0002] Cadmium chloride (CdCl 2 ) coating is a coating process for cadmium telluride solar cells, and this process plays a key role in improving the performance and efficiency of solar cells.

[0003] In the production process of cadmium telluride solar cells, cadmium chloride is mainly coated on the cadmium telluride cell interface by roll coating or spraying to form a cadmium chloride thin film, and then through high-temperature activation, Cl - ions penetrate into the cadmium telluride film layer by about 1000 nm, improving the continuity and microscopic uniformity of the cadmium telluride film layer, reducing charge loss at the interface, and thus improving the conversion efficiency of the battery.

[0004] Since the preparation process has high requirements for the thickness and uniformity of the cadmium chloride thin film, it is necessary to frequently detect the coating effect of the substrate. Currently, the EDTA titration method is commonly used in the industry. This method requires slicing for sampling, preparing titration reagents, dissolving the sample slices, and EDTA titration. Its detection cost is high, the time is long, and the detection accuracy is not high. Summary of the Invention

[0005] The purpose of the present invention is to provide an apparatus for detecting cadmium chloride thin films based on a conductivity meter, which can detect the thickness and uniformity of the cadmium chloride thin film through this apparatus, without slicing the cadmium chloride thin film, without operations such as preparing titration reagents and dissolving the sample slices. Its detection cost is low, the time is short, and the accuracy is high.

[0006] Another purpose of the present invention is to provide a detection method for detecting cadmium chloride thin films based on a conductivity meter, which uses the detection apparatus to take samples at multiple points on the cadmium chloride thin film and in-situ dissolve the cadmium chloride thin film, which can save detection time, has low cost, and high accuracy.

[0007] The present invention solves its technical problems by adopting the following technical solutions.

[0008] On the one hand, an embodiment of the present invention provides an apparatus for detecting cadmium chloride thin films based on a conductivity meter, including a dissolution cell, a weight block, and a sealing ring. The bottom of the dissolution cell is provided with a first opening that can contact the cadmium chloride thin film, and the top of the dissolution cell is provided with a second opening through which the conductivity meter can enter and exit; the sealing ring is arranged at the first opening, and the weight block is connected to the outer wall of the dissolution cell.

[0009] In some embodiments of the present invention, the interior of the dissolution tank is cylindrical. The areas of the cross-sections of the cylinder are the same. During the process of dissolving the cadmium chloride film, it is convenient to stir the dissolution liquid, so that the solute in the dissolution liquid is evenly distributed, thereby improving the accuracy of the detection by the conductivity meter and reducing the error caused by uneven solute distribution.

[0010] In some embodiments of the present invention, the weight block is detachably connected to the dissolution tank, and the weight block is sleeved on the outer wall of the dissolution tank. The detachable connection method facilitates separating the weight block and the dissolution tank, which is convenient for cleaning the device for repeated use. Preferably, the whole dissolution tank is a cylinder with a cavity inside, and the configuration block is also a hollow cylinder inside. The configuration block is sleeved outside the dissolution tank. Under the action of the gravity of the weight block, a downward pressure can be evenly applied to the sealing ring, so as to ensure that all parts of the sealing ring are in contact with the cadmium chloride film evenly, improve the sealing effect of the sealing ring, and avoid the deionized water inside the dissolution tank from flowing out, resulting in sampling failure.

[0011] In some embodiments of the present invention, the material of the dissolution tank is PVC. The PVC material is stable and will not introduce other impurities into the cadmium chloride film dissolution liquid. Secondly, the cost of the PVC material is low.

[0012] Second, the embodiments of the present invention provide a method for detecting a cadmium chloride film based on a conductivity meter, including the following steps:

[0013] Divide a plurality of sampling points on the cadmium chloride film to be detected;

[0014] Place the device according to any one of claims 1-4 on one of the sampling points so that the first opening is in contact with the cadmium chloride film;

[0015] Add a certain amount of deionized water to the dissolution tank. After the cadmium chloride film in the dissolution tank is dissolved, use a conductivity meter to measure the conductivity of the liquid in the dissolution tank;

[0016] Calculate the cadmium chloride concentration corresponding to the conductivity through the cadmium chloride concentration-conductivity curve graph, and calculate the thickness of the cadmium chloride film at this sampling point based on the amount of deionized water added to the dissolution tank and the area of the cadmium chloride film in the dissolution tank;

[0017] Repeat the above operations to detect the remaining multiple sampling points, obtain the thicknesses of the cadmium chloride films at multiple sampling points, and calculate the thickness and uniformity of the entire cadmium chloride film through statistics and analysis.

[0018] In some embodiments of the present invention, the dissolution time of the cadmium chloride film in the dissolution tank is 30-50 s.

[0019] In some embodiments of the present invention, the graph of cadmium chloride concentration - conductivity is obtained by testing at 25°C.

[0020] In some embodiments of the present invention, it further includes recording the temperature during detection.

[0021] In some embodiments of the present invention, the number of sampling points is 5 - 10.

[0022] In some embodiments of the present invention, the area of the cadmium chloride thin film located in the dissolution tank is 2000 - 3000 mm 2 .

[0023] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0024] The detection device provided by the present invention includes a dissolution tank, a sealing ring and a weight. The dissolution tank is provided with a first opening and a second opening. When using this device to detect the cadmium chloride thin film, directly place the device on the cadmium chloride thin film. Under the action of the weight, the cadmium chloride thin film is pressed on the cadmium chloride thin film. A seal can be formed at the second opening through the sealing ring, that is, the cadmium chloride thin film at the sampling point is circled in the dissolution tank, and then deionized water is used for dissolution. The structure of this device is simple, it can quickly sample on the cadmium chloride thin film, without slicing the cadmium chloride thin film, saving detection time and being convenient to operate; secondly, this device can also be reused.

[0025] The detection method provided by the present invention directly samples at multiple points on the cadmium chloride thin film, combines with a conductivity meter to test the concentration of cadmium chloride in the dissolution tank, can quickly detect multiple sampling points, greatly saving detection time and detection cost; at the same time, compared with the traditional EDTA titration detection, the operation of the conductivity meter is more convenient and the error is smaller.

[0026] In summary, the detection device and detection method provided by the present invention have the advantages of high accuracy, high detection efficiency and low detection cost, and can be widely applied in the actual production process of cadmium telluride solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0028] Figure 1 It is an exploded view of the detection device provided by the embodiments of the present invention;

[0029] Figure 2 Cross-sectional schematic view of the detection device according to an embodiment of the present invention;

[0030] Figure 3 Physical diagram of the detection device according to an embodiment of the present invention;

[0031] Figure 4 Sampling division schematic diagram of cadmium chloride film in Example 2;

[0032] Figure 5 Curve graph of cadmium chloride concentration - conductivity;

[0033] Figure 6 Physical diagram during the detection of the conductivity meter in Example 2;

[0034] Figure 7 Color change diagram during the EDTA titration process in Example 2.

[0035] Icons: 1 - Dissolution tank, 2 - Load weight, 3 - Sealing ring. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0037] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0038] Example 1

[0039] An embodiment of the present invention provides a device for detecting cadmium chloride film based on a conductivity meter. As shown in the attached Figures 1-3 , it includes a dissolution tank, a load weight, and a sealing ring. The bottom of the dissolution tank is provided with a first opening that can contact the cadmium chloride film. The sealing ring is arranged at the first opening. The top of the dissolution tank is provided with a second opening through which the conductivity meter can enter and exit. The inside of the dissolution tank is cylindrical. The load weight is detachably connected to the dissolution tank and sleeved on the outer wall of the dissolution tank. The materials of the dissolution tank and the load weight are both PVC. Among them, the radius r of the sealing ring at the first opening of the dissolution tank is 27.5 mm.

[0040] Example 2

[0041] 1. At the standard temperature (25 °C), test and formulate the curve graph of cadmium chloride concentration - conductivity: (1) Preparation of tools and materials

[0042] Burette, large beaker, 20 ml graduated cylinder, magnetic stirrer, dry cadmium chloride powder, wet weight balance, calibrated conductivity meter

[0043] (2) Prepare a cadmium chloride solution with a known concentration

[0044] Weigh 4 mg of dry cadmium chloride powder with a wet weight balance, measure 100 ml of deionized water with a graduated cylinder, prepare a cadmium chloride solution with a concentration of 0.04 g / l, and place it on a magnetic stirrer and stir for 10 minutes.

[0045] After the cadmium chloride is completely dissolved, use a conductivity meter to detect and record the conductivity value and temperature value of the 0.04 g / l cadmium chloride solution

[0046] Add a certain amount of deionized water to the burette, place the solution under the burette, and then while stirring, drip 5 ml of deionized water into the solution. At this time, the concentration is 0.038 g / l. Use a conductivity meter to detect and record the conductivity value and temperature value of the solution at this concentration again, and then continue to add deionized water to dilute the solution and measure the conductivity. Repeat this process continuously until the measured concentration-conductivity data is sufficient to cover the range corresponding to the cadmium chloride film thickness.

[0047] (3) Data processing to generate a curve

[0048] Organize the recorded data of cadmium chloride concentration versus conductivity, and use an EXCEL spreadsheet to generate a cadmium chloride concentration-conductivity curve from these data, and then obtain the cadmium chloride concentration-conductivity conversion relationship.

[0049] (4) Error control

[0050] This experiment has high requirements for data accuracy. The following measurement error controls are mainly adopted: 1. The graduated cylinder, burette, conductivity meter, and wet weight balance must be calibrated before the experiment. 2. Reduce the difference between each group of concentrations as much as possible within the allowable range to ensure that the final curve is closer to the actual situation and the conversion formula is more accurate. 3. The measured data range does not need to be too large, just covering the common measurement results is sufficient.

[0051] 2. Sampling: Take the same cadmium chloride thin film chip, cut 2 groups of samples, 9 pieces in each group, as Figure 4 . Conduct EDTA tests on the (Rn, Cn, Ln) combination, and conduct conductivity measurement tests on the (rn, cn, ln) combination. The sampling area for EDTA titration is 100 cm 2 , and the sampling area for the conductivity test is 23.81 cm 2 ;

[0052] 3. Conductivity detection, based on the device provided in Example 1, detect the cadmium chloride thin film according to the following steps:

[0053] As shown in the appendix Figure 4 Multiple sampling points are demarcated on the cadmium chloride film to be detected;

[0054] Place the sampling device of Example 1 on one of the sampling points so that the first opening is in contact with the cadmium chloride film;

[0055] Add a certain amount of deionized water to the dissolution pool. Under the action of the bottom sealing ring, the deionized water in the dissolution pool will not leak out. After stirring with a glass rod for 30 s, the cadmium chloride film in the dissolution pool dissolves, and the conductivity of the liquid in the dissolution pool is measured with a conductivity meter;

[0056] Through Figure 5 The cadmium chloride concentration corresponding to this conductivity is calculated from the cadmium chloride concentration-conductivity curve graph, and based on the amount of deionized water added to the dissolution pool and the area of the cadmium chloride film in the dissolution pool, the thickness of the cadmium chloride film at this sampling point is calculated;

[0057] Repeat the above operations to detect the remaining multiple sampling points, obtain the thicknesses of the cadmium chloride films at multiple sampling points, and calculate the thickness and uniformity of the entire cadmium chloride film through statistics and analysis.

[0058] The calculation formula is as follows:

[0059] V, the volume of the solution, that is, the volume of deionized water added;

[0060] S1, the sampling area of the sampler;

[0061] According to the measured conductivity (E), referring to the cadmium chloride concentration-conductivity curve graph( Figure 5 , the abscissa X is the cadmium chloride concentration, and Y is the conductivity), the concentration of cadmium chloride is obtained,

[0062] C = (SQRT(970997.8521 - 10455.6*(3.8402 - E)) - 985.39) / 5227.8;

[0063] The mass of CdCl 2 within the unit area (S2: usually 1 m 2 ): G1 = C*V*S2 / S1;

[0064] The relative density of cadmium chloride is 4.05 g / cm 3 , film thickness (nm) = film weight per unit area (g / m 2 ) ÷ (film density (g / cm 3 ), so the thickness of CdCl 2 : H = G1 / 4.05;

[0065] Deviation of a single sampling point: P1 = (G1 - Gave) / Gave;

[0066] Comprehensive deviation: P2 = (G1MAX - G1min) / Gave;

[0067] The relevant data detected at different sampling points are shown in Table 1.

[0068] 4. Detection by EDTA titration method

[0069] (1) Preparation of tools and materials

[0070] ① Experimental equipment

[0071] Pure water, EDTA (C10H14N2O8Na2·2H2O), NH4Cl, ammonia water, Eriochrome Black (indicator)

[0072] ② Titration drugs

[0073] Several beakers, titration tubes and their racks, droppers, medicine spoons, funnels, funnel racks, spray bottles, magnetic stirrers / glass rods

[0074] ③ Preparation of buffer solution

[0075] Buffer solution: Put 5.4 g of NH4Cl into 35 ml of 25% ammonia water and mix well, then add pure water to make it reach 100 ml. After the solution is prepared, store it in a brown solution bottle and label it.

[0076] ④ Preparation of EDTA solution

[0077] EDTA solution: The concentration of the EDTA solution is 0.005 mol / L. That is, 0.93 g of EDTA is put into 500 ml of pure water and mixed well. After the solution is prepared, store it in a brown solution bottle and label it.

[0078] (2) Titration process

[0079] Cut the 1.2 m * 1.6 m chip into Figure 4 9 sample pieces (L1-3 / C1-3, R1-3)

[0080] ① Install the funnel and the funnel rack, place a beaker under the funnel rack, and fill the spray bottle with pure water.

[0081] ② Spray the surface with the spray bottle filled with pure water. Note that be sure not to spray the back of the sample piece, because the light-receiving surface of the sample may also be contaminated with CdCl 2 , which will cause the titration result to be too large. After spraying about 200 - 300 ml of pure water, titration can be carried out.

[0082] ③ Prepare the titration rack and the magnetic stirrer.

[0083] ④ Pour out a part of the prepared 0.005 mol / L EDTA solution into a small beaker, and pour it from the upper part of the titration tube so that the liquid level is above the 0 scale of the titration tube.

[0084] ⑤ Place the small beaker containing the EDTA solution below the liquid outlet of the titration tube, slowly turn the glass stopcock to titrate and evacuate the gas in the titration tube, and control the liquid level at the 0 scale.

[0085] ⑥ Take a sample solution and place it below the burette. Slowly turn the glass stopcock of the titration tube and observe the color change of the CdCl 2 solution after the EDTA solution drops. Continuously stir during this period using a magnetic stirrer or a glass rod.

[0086] ⑦ When the color changes to Figure 7 blue (the final color depth will vary according to the amount of eriochrome black added), close the glass stopcock and wait for one to two minutes to see if the color in the beaker will change back. If the color changes back to pink or red, continue titrating; if the color is stable, read the liquid level reading of the titration tube.

[0087] ⑧ Data recording;

[0088] ⑨ Instrument cleaning: After titration, empty the EDTA solution in the titration tube into the small beaker. Pour pure water from the upper part of the titration tube to exceed the 0 scale line, let it stand for a few minutes and then empty it, and repeat once. Wash all tools such as beakers, droppers, and medicine spoons with pure water.

[0089] (3) Data analysis

[0090] 1 mol EDTA = 1 mol Cd 2+ ;

[0091] 1 ml of 0.005 mol / L EDTA = 0.562 mg Cd 2+ ;

[0092] 1 ml of 0.005 mol / L EDTA = 0.9165 mg CdCl 2 ;

[0093] 1 ml of 0.005 mol / L EDTA = 1.1415 mg CdCl 2 ·2.5H 2 O;

[0094] The results are shown in Table 2.

[0095] Table 1 Conductivity test method

[0096]

[0097] Table 2 EDTA Titration Method

[0098]

[0099] Because the sampling points are random, the data of the two groups of titration tests can reflect the coating situation of the chip.

[0100] According to the comparison of the two groups of experimental data: for the same chip using the EDTA titration method, the deviation is 99.2%, while using a conductivity meter, it reaches 27.8%.

[0101] It can be preliminarily inferred that due to its small sampling area, the conductivity meter measurement method is more sensitive to the chip deviation. The two methods have little deviation in the measurement of the coating amount of CdCl 2 .

[0102] It should be noted that in Tables 1 and 2 above, the deviation is not an error, but the film thickness deviation between the test samples of the cadmium chloride film. This index reflects the uniformity index of the cadmium chloride film. The process allows a deviation of within 15%. This example verifies that the smaller the sampling area, the greater the sample film thickness deviation.

[0103] Table 3 Costs and Errors of Two Detection Methods

[0104]

[0105] It can be obtained from Table 3 that the conductivity measurement method provided by the present invention has fewer error - generating nodes, that is, less cumulative error, high measurement accuracy, short detection time, and low detection cost.

[0106] In summary, the detection method provided by the embodiments of the present invention directly samples at multiple points on the cadmium chloride film, combines with the conductivity meter to measure the concentration of cadmium chloride in the dissolution pool, can quickly detect multiple sampling points, greatly saving the detection time and cost; at the same time, compared with the traditional EDTA titration detection, the operation of the conductivity meter is more convenient and the error is smaller.

[0107] The above - described embodiments are some embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A device for detecting cadmium chloride thin film based on a conductivity meter, characterized in that: It includes a dissolution tank, a weight block and a sealing ring. The bottom of the dissolution tank is provided with a first opening that can contact the cadmium chloride film, and the top of the dissolution tank is provided with a second opening that can allow an electric conductivity meter to enter and exit; the sealing ring is arranged at the first opening, and the weight block is connected to the outer wall of the dissolution tank.

2. The device for detecting cadmium chloride thin film based on conductivity meter according to claim 1, characterized in that: The interior of the dissolving tank is cylindrical.

3. The device for detecting cadmium chloride thin film based on conductivity meter according to claim 1, characterized in that: The weight block is detachably connected to the dissolution tank, and the weight block is sleeved on the outer wall of the dissolution tank.

4. The device for detecting cadmium chloride thin film based on conductivity meter according to claim 1, characterized in that: The material of the dissolving tank is PVC.

5. A method for detecting cadmium chloride thin film based on conductivity meter, characterized in that: The following steps are involved: Divide a plurality of sampling points on the cadmium chloride film to be tested; Placing the device according to any one of claims 1 to 4 on one of the sampling points so that the first opening is in contact with the cadmium chloride film; Adding a certain amount of deionized water into the dissolution tank, and after the cadmium chloride film in the dissolution tank is dissolved, testing the conductivity of the liquid in the dissolution tank with a conductivity meter; The cadmium chloride concentration corresponding to the conductivity is calculated through a curve of cadmium chloride concentration-conductivity, and the thickness of the cadmium chloride film at the sampling point is calculated based on the amount of deionized water added to the dissolution tank and the area of ​​the cadmium chloride film in the dissolution tank; Repeat the above operation to detect the remaining multiple sampling points to obtain the thickness of the cadmium chloride film at the multiple sampling points. Through statistics and analysis, the thickness and uniformity of the entire cadmium chloride film are calculated.

6. The method for detecting cadmium chloride thin film based on conductivity meter according to claim 5, characterized in that: The time for dissolving the cadmium chloride film in the dissolution tank is 30-50s.

7. The method for detecting cadmium chloride thin film based on conductivity meter according to claim 5, characterized in that: The cadmium chloride concentration-conductivity curve is obtained by testing at 25°C.

8. The method for detecting cadmium chloride thin film based on conductivity meter according to claim 5, characterized in that: Also includes recording the temperature during detection.

9. The method for detecting cadmium chloride thin film based on conductivity meter according to claim 5, characterized in that: The number of the sampling points is 5-10.

10. The method for detecting cadmium chloride thin film based on conductivity meter according to claim 5, characterized in that: The area of ​​the cadmium chloride film in the dissolution tank is 2000-3000mm 2 .

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