TW201303320A - Method for analyzing electrical properties of solar cell - Google Patents

Abstract

A method for analyzing the electrical properties of the solar cell is disclosed in the present invention. The method can immediately determine whether the factor leading to solar cell's efficiency drop is due to the substrate quality or the process. Firstly, a database must be established by collecting the electrical data. The electrical data is obtained by irradiating the solar cell with different rank with a solar simulator, a light source having long wavelength or short wavelength. On the production line, the solar cell is irradiated by the solar simulator initially to measure the efficiency. Once the solar cell with the abnormal or low efficiency is found, an additional light source with long wavelength or short wavelength is used to irradiate the solar cell to measure the electrical data, which provides the information mainly come from the interior or the process-layer of the solar cell. Through comparing these electrical data with the database, the factor leading to solar cell's abnormal efficiency can be determined immediately.

Description

Solar cell electrical analysis method

The invention relates to a method for electrical analysis of a solar cell, in particular to a method for instantly determining the cause of abnormal solar cell efficiency on a production line.

The power generation efficiency of solar cells and the efficiency of energy conversion determine whether solar energy can completely replace existing petrochemical energy in the future as a main source of power. Conventional solar cell processes include: cleaning, texturing, diffusion doping, insulation, anti-reflective coating, screen printing electrodes, and sintering. As shown in FIG. 1 , the structure of the solar cell 1 is divided into a substrate region 10 and a process layer 11 , wherein the substrate region 10 refers to a region that has not been subjected to the above process flow; the process layer 11 is located at the surface of the solar cell 1 , including the doping The structural layers such as the impurity layer 110, the anti-reflection layer 111, and the electrode 112 are generally from the surface of the solar cell to below, and have a depth of about 10 μm.

In the solar industry, after each solar cell substrate completes the surface process, the finished product needs to be tested with a solar light source to detect its energy conversion efficiency, that is, the current that the solar cell can output under illumination. In addition to grading the solar cells according to the measurement results and judging whether the photoelectric conversion efficiency has reached the expected standard, when the yield is not good, the process parameters can be traced back to the process parameters to optimize them.

Therefore, when the product test results are not as expected, the engineering staff is bound to find out the key reasons for reducing the photoelectric conversion efficiency to further adjust the process parameters. According to experience, most of the reason for the decrease in efficiency is because the carrier lifetime is shortened. There are two reasons for affecting the life of the carrier: First, because the raw materials of the solar cell itself are of poor quality, that is, the poor electrical conductivity of the substrate region causes the efficiency of the solar cell to decrease; second, because the process parameters are not appropriate, that is, The process layer causes the carrier life to become shorter.

For manufacturers using single crystal germanium as a raw material for solar cells, the first factor may be overlooked. However, for manufacturers using polysilicon as a solar cell substrate, the quality of each wafer is not as fixed as the use of a single crystal germanium solar cell substrate. Therefore, engineers need to compare and analyze various data to determine whether the cause is from the process layer or the substrate area, which often takes one or two days to determine.

Since the solar industry has a very large daily production volume, a production line can produce about 20,000 to 30,000 pieces a day, so once there is a problem, the production line needs to be stopped before the cause is found to avoid causing a large loss; It was discovered that because of the problem of raw materials, the photoelectric conversion efficiency could only be improved by changing the materials. As a result, the time it took to stop the production line and the time spent by the engineers was quite worthless.

Therefore, if a method can be developed, it is possible to determine the problem of the raw material or the process in a short time, and in addition to saving time and cost, the loss due to process error can be quickly avoided.

At present, in the industry, before the start of the solar cell process, the raw materials are analyzed and tested. However, since the conventional detection method is to use a microwave to generate electrons in a semiconductor, a coil is used to sense the amount of electrons generated to know the quality of the material itself. However, this type of detection is affected by a large number of dangling bonds on the surface of the wafer, making it impossible to know exactly whether the material itself has a problem. Therefore, before the test, it is usually necessary to do some surface treatment, such as surface passivation or annealing, to reduce the problem that the dangling bond affects the actual measurement results. However, if each wafer is to be processed and tested, the cumulative process cost will be considerable.

In U.S. Patent No. 4,301,409, it is disclosed that a monochromatic light, such as a laser, is used to scan the surface of a solar cell. When the solar cell is scanned, the amount of electricity outputted at each point is displayed on the screen in brightness, thereby detecting the solar cell. Whether the surface has cracks and other defects.

In another U.S. Patent No. 6,541,754, the use of a plurality of different wavelength sources for detecting the photoelectric characteristics of a photoelectric conversion device is also mentioned. The photoelectric conversion device has a stacked structure and is formed by stacking a plurality of semiconductor junctions. The photoelectric characteristics of the photoelectric conversion device under standard test conditions are inferred by measuring the measured short-circuit current of each unit cell compared to the offset under standard test conditions and the actual measured photoelectric characteristics.

However, this patent is mainly for a multi-layer stacked photoelectric conversion device, and each unit cell itself absorbs light sources of different wavelengths to know the photoelectric conversion efficiency of each layer of unit cells, and the materials used are single crystals. The quality of itself is very good, so there is no problem with the present invention.

In summary, it is an object of the present invention to provide a method for instantly determining the cause of abnormal solar cell efficiency.

It is an object of the present invention to provide an electrical analysis method for a solar cell, which is to determine the cause of abnormal solar cell efficiency, and is a substrate or process from a solar cell. The solar cell has completed all processes and has a substrate region and a process layer.

The method comprises the steps of: establishing a database for respectively illuminating a normal light source, a long wavelength light source or a short wavelength light source for collecting solar cells of different levels of photoelectric conversion efficiency, so as to measure the solar cells. Electrical data, and individual electrical data of the substrate area or process layer, the normal light source is a solar analog light source, and the long wavelength light source or the short wavelength light source is relative to the normal light source wavelength range; setting a warning standard Each solar cell on the production line is sequentially illuminated with a normal light source, and the electrical data of the solar cells are measured, and the solar cell with abnormal efficiency is found according to the warning standard; and the solar cell with abnormal efficiency is applied with a long wavelength or The short wavelength source is illuminated to obtain electrical data primarily from the substrate region or process layer.

Finally, comparing the data of the database and the efficiency of the abnormal solar cell under different illumination conditions, the reason for the abnormality of the solar cell efficiency is determined by the substrate area or the process layer.

The method provided by the invention, when it is found that the solar cell is inefficient, can be immediately distinguished by the cause of the process or the raw material itself, and helps the engineering personnel to immediately determine the subsequent processing manner to reduce the loss.

In order to make the above objects, features and advantages of the present invention more comprehensible, the following is a detailed description of the electrical analysis method of the solar cell according to the present invention, with reference to the accompanying drawings.

As described above, the solar cell performs all processes, and the structure can be roughly divided into a substrate region and a process layer, wherein the process layer is located on the surface of the substrate region, from the surface of the solar cell to a depth of 10 μm. When the photoelectric conversion efficiency of the solar cell is not good, the present invention uses a normal light source and an external light source, such as a long wavelength light source or a short wavelength light source, for detection.

Wherein, the normal light source is a solar light source, and the long wavelength light source or the short wavelength light source is relative to the normal light source wavelength range, wherein the long wavelength or short wavelength light source is an external light source, or filtered by one The sheet is filtered by a normal light source. In the embodiment of the present invention, the long-wavelength light source has a wavelength range of about 700 to 1100 nm, and the short-wavelength light source has a wavelength range of about 400 to 500 nm, but in practice, the two light sources may also select monochromatic light having a wavelength within the above range.

Since the long-wavelength light source can penetrate up to about 100 to 150 μm below the surface of the solar cell, and the surface depth of the solar cell is only about 10 μm, the measured electrical data can represent the electrical properties of the solar cell substrate region, while ignoring solar energy. The effect of the battery surface process on the electrical results.

The short-wavelength light source can only reach a depth of about 10 μm below the surface of the solar cell, so the measured result represents the electrical data of the process layer. Therefore, the present invention uses the above two external light sources for detection to distinguish the cause of poor solar cell yield, which is caused by the substrate or process factors.

For detailed detection steps, please refer to FIG. 2, which is a flowchart of an embodiment of the present invention. In step S200, a database is created. The database is established by irradiating a normal light source, a long-wavelength light source or a short-wavelength light source with solar cells of different levels of photoelectric conversion efficiency, to measure the electrical data of the solar cells, and the substrate. Individual electrical data for the zone or process layer. The database can be represented by looking up a table or a diagram.

In the embodiment of the present invention, the manner of establishing the database is as follows in steps S201 to S203. The drawing method includes: measuring the solar cell electrical data as a Y-axis by a normal light source; measuring the electrical data of the substrate region or the processing layer measured by the long-wavelength light source or the short-wavelength light source as an X-axis, and drawing a relationship Figure, and preset an error tolerance range, as shown in Figure 3. The relationship diagram includes at least one relationship curve.

In this embodiment, the normal light source, the long-wavelength or the short-wavelength light source is used to illuminate the batch of solar cells of different grades, and when measuring the electrical property, the photoelectric conversion efficiency and the three factors affecting the photoelectric conversion efficiency can be known. : filled factor, open circuit voltage (V _oc ), and short circuit current (I _sc ).

In the actual process, the photoelectric conversion efficiency is easily affected by the process parameters, for example, the thickness of the line width of the surface electrode line of the solar cell is slightly different. Therefore, in the embodiment of the present invention, the measured electrical data is obtained. In the middle, it is preferable to select one of the open circuit voltage (V _oc ) or the short circuit current (I _sc ) to draw the relationship diagram.

Referring to FIG. 3, the relationship diagram drawn in the above manner is used as a database. The figure includes three linear relationship curves 20 to 21, and the solar cells are irradiated from the bottom to the top by a short-wavelength light source, a normal light source, and a long-wavelength light source, and the measured open circuit voltage (V _oc ) is plotted as an X-axis. Further, in the preferred embodiment of the present invention, the tolerance of the setting relationship curve is approximately 3 to 5%.

Next, a warning criterion is set, as in step S205. When the warning standard is set, the solar cell on the production line is irradiated with a normal light source, and the photoelectric conversion efficiency is measured. When the photoelectric conversion efficiency of one of the solar cells is lower than a predetermined value, the following steps are immediately performed to detect the solar energy. The reason for poor battery efficiency. Among them, the predetermined value can be set by the manufacturer according to the customer's needs, or set by the manufacturer itself.

In step S210, each solar cell on the production line is sequentially illuminated with a normal light source, the electrical data of the solar cells is measured, and the solar cell with abnormal efficiency is found according to the warning standard.

In step S215, the solar cell with abnormal efficiency is further irradiated with a long-wavelength light source or a short-wavelength light source to obtain electrical data mainly from the solar cell substrate region or the process layer.

Finally, in step S220, comparing the electrical data measured by the database and the efficiency abnormal solar cell under different illumination conditions, the reason for accurately determining the solar cell efficiency abnormality is from the substrate region or the process layer. .

In the embodiment of the present invention, the discriminating method includes: setting the electrical data measured by the solar cell with abnormal illumination efficiency of the normal light source as the Y coordinate, as in step S221. Next, the solar cell whose efficiency is abnormal with a long-wavelength or short-wavelength light source is used, and the measured electrical data is set to the X coordinate, as by step S222. Finally, by judging whether the coordinate (X, Y) is in the relationship diagram, whether the position falls within the relationship curve or the error tolerance range, as in step S223, if YES, the cause of the solar cell efficiency abnormality is derived from the substrate. If "no", it comes from the process.

Here, the following is exemplified by FIGS. 4A and 4B. Referring first to Fig. 4A, there is shown a relationship diagram of an open circuit voltage measured by a long wavelength light source illuminating a solar cell, that is, an open circuit voltage measured in a substrate region as an X axis, and an open circuit voltage measured by a normal light source illuminating a solar cell as a Y axis. Among them, the three points 4a, 4b, and 4c respectively represent the measurement results of three solar cells with abnormal efficiency. From Fig. 4A, it can be seen that the measured coordinate values of the 4a and 4b test pieces are (V _{sb, a} , V _ay ), (V _{sb, b} , V _by ), respectively.

The X coordinate value of the 4a test piece V _sb,a , the relationship curve 22 established by the comparison database should originally correspond to V _oc,A , but the actual value V _ay and the standard value V _oc , _A are caused by the process factors. There is a bias; the condition of the 4b test piece is also true. Therefore, points 4a and 4b represent the reasons for the abnormal efficiency of the two test pieces 4a and 4b, mainly from the process layer.

Referring to FIG. 4A again, the measured coordinate values of the 4c test piece are respectively (V _{sb, c} , V _cy ), which just fall on the relationship curve 22. Since V _cy is the actual measured value, it indicates that the efficiency of the 4c test piece is not as expected due to the poor properties of the substrate itself.

In another embodiment, FIG. 4B shows that the solar current test piece is irradiated with a short-wavelength light source, and the measured open circuit voltage is the X-axis of the process layer open circuit voltage. The open circuit voltage measured by the normal light source is a relationship diagram of the Y axis. The conditions and determination methods of the three test pieces 4a', 4b', and 4c' are the same as those in Fig. 4A.

In summary, the method of the embodiment of the present invention can immediately determine the cause of the poor efficiency of the solar cell, and the method of the present invention has the following advantages:

(1) The method is simple, the cost is low, and the process can be automated. As long as the program is set, once the solar cell efficiency is detected to be lower than a predetermined value, and the light source is detected, and the data base is compared, the cause of the abnormality can be determined. For the manufacturer who originally prepared the solar energy, it is hardly As a result, redundant testing costs are incurred.

(2) It is possible to immediately eliminate the condition of the production line with problems in the process to avoid a large loss. When the efficiency of the solar cell is abnormal, it is quickly determined whether it is a process factor or a raw material itself. It is not necessary to wait for a full day of production line stop, and then perform a sampling test on the low-efficiency film.

(3) It can save time and cost, and avoid the problem that the production volume is reduced because it takes only one or two days to waste the analysis of the production line.

(4) For the solar cell whose raw material is polycrystalline, amorphous or single crystal, the method of the invention can be used to achieve the purpose of rapid detection. In particular, when an amorphous or polycrystalline raw material is used, it is easy to cause a problem that it is difficult to discriminate that it is a process or a raw material, resulting in inefficiency, and the method of the embodiment of the present invention can more effectively exert its efficacy.

The present invention has been described above by way of a preferred example, but it is not intended to limit the spirit of the invention and the inventive subject matter. Those who are familiar with the technology can easily understand and utilize other components or methods to produce the same effect. Modifications made without departing from the spirit and scope of the invention are intended to be included within the scope of the appended claims.

1. . . Solar battery

10. . . Substrate area

11. . . Process layer

110. . . Doped layer

111. . . Antireflection layer

112. . . Metal electrode

S200, S201, S202, S203, S205, S210, S215, S220, S221, S222, S223. . . Detection step

20~22. . . Relationship lines

Figure 1 is a simplified schematic view of a conventional solar cell structure;

2 is a flow chart of a method for instantly determining the cause of abnormal solar cell efficiency according to the present invention;

Figure 3 is a diagram showing the relationship between the measured electrical data by illuminating a solar cell with a normal light source, a long wavelength, and a short wavelength source;

4A is a relationship diagram of measured electrical data by irradiating a solar cell with a normal light source and a long wavelength light source; and

Fig. 4B is a diagram showing the relationship between the measured electrical data by irradiating the solar cell with a normal light source and a short-wavelength light source.

S200, S201, S202, S203, S205, S210, S215, S220, S221, S222, S223. . . Detection step

Claims (9)

An electrical analysis method for a solar cell, which can immediately determine the cause of abnormal solar cell efficiency on the production line, is a substrate or a process from the solar cell, wherein the solar cell has completed all processes, and has a substrate region and a process layer The method comprises the steps of: establishing a database for collecting solar cells of different levels of photoelectric conversion efficiency, respectively irradiating a normal light source, a long wavelength light source or a short wavelength light source to measure the solar energy The electrical data of the battery, the normal light source is a sunlight analog light source, and the long wavelength light source or the short wavelength light source is relative to the normal light source wavelength range; setting a warning standard; each solar energy on the production line The battery sequentially illuminates the normal light source, and measures the electrical data of the solar cells, and finds the solar cell with abnormal efficiency according to the warning standard; and applies the long-wavelength light source or the short wavelength to the solar cell with abnormal efficiency. Irradiating the light source to obtain mainly from the solar cell substrate region or in the process layer Electrical data; and the electrical data of the database and comparing the efficiency of the solar cell abnormality under different illumination conditions, and determines the cause of the abnormality of the solar cell efficiency. The method of claim 1, wherein the method for establishing the database comprises: respectively, measuring the electrical data of the solar cells under the illumination of the normal light source as a Y-axis, the long-wavelength light source or Under the illumination of the short-wavelength light source, the measured electrical data of the solar cells is an X-axis; and a relationship diagram is drawn, the relationship diagram includes at least one relationship curve, and an error tolerance range is preset. The method of claim 1, wherein the method for determining the abnormality of the solar cell efficiency is that the method of the substrate or the process comprises: irradiating the solar cell with the abnormal efficiency by the normal light source, and measuring The obtained electrical data is set to the Y coordinate; the solar cell having the abnormal efficiency is irradiated with the long-wavelength or short-wavelength light source, and the measured electrical data is set as the X coordinate; and the judgment coordinate (X, Y) is in the In the diagram, whether the position falls on the relationship curve or within the tolerance of the error, if "Yes", the cause of the solar cell efficiency abnormality is from the substrate, and if "No", it is from the process. The method of claim 2, wherein in the measured electrical data, one of an open circuit voltage (V _oc ) or a short circuit current (I _sc ) is selected as the X axis and the Y axis. The method of claim 1, wherein the normal light source has a wavelength range of about 400 to 1100 nm, the long wavelength source has a wavelength range of about 700 to 1100 nm, and the short wavelength source has a wavelength range of about 400 to 500 nm. . The method of claim 1, wherein the long wavelength light source or the short wavelength light source is an external light source or a filter is used to filter the normal light source. The method of claim 1, wherein the method is directed to a solar cell having a polycrystalline, amorphous or single crystal material. The method of claim 1, wherein when the warning standard is set, the solar cell on the production line is irradiated with a normal light source, and the photoelectric conversion efficiency is measured, and when the measured photoelectric conversion efficiency is found to be lower than a predetermined one, At the time of the value, the subsequent steps are immediately performed to detect the cause of the inefficiency of the solar cell. The method of claim 1, wherein the error tolerance range is about 3 to 5%.