TWI394967B - Defect inspection device and inspection method of solar cell - Google Patents

Description

Solar cell defect inspection device and inspection method Technical field

The present invention is a device and method for inspecting defects in a solar cell.

Background technique

In recent years, with the rising awareness of environmental protection, a large number of solar cells have been circulating in the market. As such, it is important to check the performance of the solar cell, specifying the manufacturing steps and removing defective solar cells.

Patent Document 1 below discloses a solar cell output detecting device using two light sources of a main light source and a sub light source. In a solar cell, when a plurality of solar cells are connected in series, the output current value of the entire device is the same as the current value generated by the solar cell with the least amount of power generation. Therefore, the main light source unit illuminates the light receiving surface of the detecting unit of the solar cell, and the sub light source unit illuminates the light receiving surface of the non-detecting target unit with high illuminance, and generates a high current for the non-detecting target unit. The value is thereby used to detect the in-plane distribution of the light receiving surface of the detection target unit.

Further, Patent Document 2 discloses an inspection apparatus by an electroluminescence (hereinafter referred to as EL) method. The device detects defects such as cracks or notches based on the characteristics of light emitted when a forward current is applied to the solar cell.

Advanced technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open No. 2010-238906

[Patent Document 2] Japanese Special Table 2006-59615

Invention

However, in the detection of the series and the module of the tandem solar cell unit, when the output detection is performed using the two main light sources of the main light source unit and the sub-light source unit, the generation current of the detection target unit irradiated with the light of the autonomous light source unit is generated. And detecting the generated current of the non-detecting target unit of the resistance component of the bypass and flowing detection target unit. That is, the solar cell unit can be represented by an equivalent circuit, and the equivalent circuit includes: a series current source and a diode, a resistor connected in parallel with the current source and the diode, and the current source and the diode The resistance of the body series. Therefore, when the solar cells are connected in series, the bypassed current flows in the resistors connected to the current source and the diode in the individual cells. For example, when the first solar cell is detected, the current generated by the cell after the second cell other than the non-detection source flows in the first step, except for the current value of the first cell. The parallel resistances of the cells are added together. Hereinafter, the bypassed current is referred to as a bias current.

Each unit constituting the string and the module has different internal resistance values depending on the quality unevenness of the unit manufacturing. Therefore, according to the light irradiation of the sub-light source portion, each solar cell unit will flow different bias currents, and the correct inspection result cannot be obtained.

In particular, when the bias current is large, the image of the defective unit in the display image of the inspection result exceeds the input range of the detection system, and thus becomes an image exceeding the upper limit of processing of the image data and the brightness is too high. a piece of snow White.

The bias current is larger than the power generation current of the main light source unit, and if it is converted into an image in the original state, for example, when detecting the first unit having a small resistance, the output unit detects that only the first one is detected. The unit's power generation is quite a erroneous result.

Further, depending on the unevenness of the resistance components of the solar cells in the string and the module, the defective portion may be judged to be good, or the good portion may be judged to be defective. Therefore, in the defect inspection apparatus using two light sources, it is necessary to detect the bias current and subtract the value from the added current value, and there is no description at all in Patent Document 1.

Further, in the EL method, when a polycrystalline solar cell is used, when a forward current has flowed, it is affected by the grain boundary portion of the power generation of the polycrystalline solar cell and the grain boundary portion of the non-power generation. However, there is a problem that it is difficult to discriminate by an image in which the grain boundary form of the polycrystalline solar cell unit is defective.

In view of the above circumstances, an object of the present invention is to provide a defect inspection device and an inspection method for a solar cell which can determine a defect with high precision.

The defect inspection device for a solar cell of the present invention is for inspecting a defect of a solar cell having a plurality of cells connected in series, and is characterized by comprising: a main light source, which is a device that irradiates light to a unit of the detection target in the unit; Illuminating the unit of the non-detecting object in the unit; the light source control circuit controls the illuminance of the main light source and the sub-light source respectively, so that the illuminance of the sub-light source is higher than the illuminance of the main light source; the current-voltage converter , is given the aforementioned solar cell The output current is converted into a voltage and output; the amplifier is given the voltage output by the current-voltage converter, and is amplified and output; the bias current extraction circuit is included in The bias current from the output of the amplifier is extracted and output; the bias current cancellation circuit subtracts the bias current drawn by the bias current extraction circuit from the output of the amplifier and outputs the output The A/D converter converts the output from the bias current canceling circuit into digital data and outputs it; the image processing device performs image processing on the digital data output by the A/D converter. And outputting the image data; and the display is provided to the image data output by the image processing device and displaying the image, and the defect inspection device determines the target according to the bias current The unit has generated the starting current component for power generation for inspection.

The method for inspecting a defect of a solar cell of the present invention is for inspecting a defect of a solar cell in which a plurality of cells have been connected in series, and is characterized in that the method comprises the steps of: detecting, by the first light source, a unit of the detection target in the unit by using the first light source Irradiating light; illuminating a unit of the non-detection target in the unit with a second illuminance higher than the first illuminance by a sub-light source; and extracting the output included in the solar cell by a bias current extraction circuit a bias current of the current; the bias current is offset from the current output by the solar cell by the bias current canceling circuit; and the output from the bias current canceling circuit is used for image processing and display In the display, the inspection is performed based on the starting current component that has been subjected to the aforementioned bias current and the unit of the detection target has been generated.

According to the defect inspection apparatus and the inspection method of the solar battery of the present invention, the two main light sources and the sub-light source unit are used in total, and the detection of the correct current generated by the bias current can be performed. As a result, the defect can be appropriately performed. The image is displayed. Further, according to the present invention, even when the solar cell uses the polycrystalline solar power, since it is not affected by the grain boundary, the grain boundary pattern is not formed when the image is formed, and only the defect portion such as the crack can be specified.

Simple description of the schema

Fig. 1 is a perspective view showing the overall configuration of a defect inspection device for a solar cell according to an embodiment of the present invention.

Fig. 2 is a circuit diagram showing a configuration example of a bias current extraction circuit in the same defect inspection device.

The third (a) to (d) diagrams are graphs showing the voltage waveforms of the respective portions of the bias current extraction circuit having the configuration shown in Fig. 2.

Fig. 4 is a circuit diagram showing another configuration example of the bias current extraction circuit in the same defect inspection device.

Fig. 5 is a timing chart showing the timing of extracting the bias current in the same bias current drawing circuit.

The sixth (a) to (c) diagrams are explanatory diagrams showing a method of imaging with the detection value of the generated current by the defect inspection device.

Fig. 7 is a graph showing the detected current before the bias current is offset in the defect inspection device.

Fig. 8 is an explanatory view showing an inspection image before the bias current is canceled in the defect inspection device.

Figure 9 shows the inspection after offsetting the bias current in the same defect inspection device. A chart of current flow.

Fig. 10 is an explanatory view showing an inspection image after the bias current is canceled in the defect inspection device.

Form for implementing the invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 shows the overall configuration of a defect inspection device for a solar cell according to an embodiment of the present invention.

The defect inspection device includes a mounting table 1, an inspection pin 2, a main light source 3, a sub-light source 4, a light source control circuit 5, a moving mechanism 6, a shunt resistor 7, an amplifier 8, a bias current extraction circuit 9, and a bias current. The offset circuit 10, the mute circuit 11, the analog digital (hereinafter referred to as A/D) converter 12, the image processing device 13, and the display 14.

The mounting table 1 is placed on the upper portion of the defect inspection device to mount the solar battery S, and the solar cell S to be detected is placed with the light receiving surface facing downward. Moreover, the solar cell S here refers to a series of solar cell strings and modules connected to the strings. The mounting table 1 is preferably made of a material having transparency such as glass.

The inspection pins 2 that are provided at both ends of the mounting table 1 are respectively connected to the tab leads protruding from the both ends of the mounted solar cells S. In this state, the main light source 3 disposed under the mounting table 1 emits light to the state battery unit to be detected. Here, the main light source 3 can be moved toward the longitudinal direction of the solar cell S by the moving mechanism 6. The initial position of the main light source 3 is directly below the first unit of the solar cell S which is the first detection target. In the present embodiment, a laser light source is used as the main light source 3.

All the cells remaining in the solar cell S (that is, the entire non-detection target cell) are irradiated with light from a plurality of sub-light sources 4. At this time, the illuminance of the light of the sub-light source 4 is controlled to be higher than the illuminance of the light of the main light source 3 by the light source control circuit 5.

The current of the detected detection unit is taken out from the inspection pin 2, and the voltage generated at both ends of the shunt resistor 7 is amplified by an amplifier, thereby converting the detected current into a voltage. However, it is not limited to the shunt resistor 7 as long as it is a current-voltage converter that converts a current into a voltage.

The amplified voltage value Va+Vb is applied to the bias current extraction circuit 9, and the bias voltage value Vb corresponding to the bias current component generated by the irradiation of the light of the sub-light source 4 is extracted. On the other hand, Va is a voltage generated by the light-initiating power in the detection target unit.

The bias current canceling circuit 10 is composed of a noise amplifier, and is supplied with a voltage Va+Vb output from the amplifier 8 and a bias voltage Vb extracted from the bias current extracting circuit 9, and is subtracted from the voltage Va+Vb. The value of the bias voltage Vb is amplified and output. The output from the bias current canceling circuit 10 is given to the masking circuit 11.

The shielding circuit 11 is configured to be capable of muting the transient signal generated when the bias current canceling circuit 10 cancels the bias current component, and is not displayed on the image in the subsequent display 14. Although the masking circuit 11 is desirably set to be a transitional signal, the image does not affect the image, but it is not necessarily an indispensable condition as long as it is set according to the desired image quality.

The output from the masking circuit 11 is converted into a number by the A/D converter 12. The bit data is subjected to image processing in the image device 13 and displayed on the display 14.

In this way, the output current is offset from the output of the first solar cell from the detection target, and only the generated current is taken out and displayed on the display 14.

After the detection of the first solar cell of the detection target is completed, the detection target unit moves to the second solar cell. Therefore, the main light source 3 moves toward the lower portion of the second solar cell unit by the moving mechanism 6, and illuminates the second solar cell unit. At this time, the object to be irradiated by the sub-light source 4 is switched to all of the non-detection target units other than the second solar battery cell that has become the new detection target unit by the light source control circuit 5. The subsequent steps are the same as the detection process of the first unit.

After such a process, until the detection of all the cells of the solar cell S is completed, the detection of the output current from the solar cell unit, the offset of the bias current, the processing until the image formation, and the detection of each unit are repeated. Each generated current is displayed as image data.

Fig. 2 is a view showing an example of the circuit configuration of the bias current extraction circuit 9. This configuration employs an analog circuit method and includes a low pass filter 21, a subtraction circuit 22, an envelope detection circuit 23, an addition circuit 24, a sample and hold circuit 25, and a timing signal generation circuit 26.

The operation of the bias current extraction circuit 9 will be described using a third diagram showing the waveforms of the voltages V1 to V6 output from the circuit elements in the second drawing.

The voltage V1 (=Va+Vb) amplified by the amplifier 8 shown in Fig. 1 has a wave including a high-frequency component as shown in Fig. 3(a). shape.

This voltage V1 is input to the low-pass filter 21 and integrated, and the high-frequency component is removed and output as the voltage V2 as shown in the third figure (a).

The voltage V2 and the voltage V1 output from the amplifier 8 are input to the subtraction circuit 22, and the voltage V1 is subtracted from the voltage V2. Thereby, the voltage V3 having the high-frequency component (that is, the waveform shown in FIG. 3 corresponding to the generated current) included in the voltage V1 can be extracted. This voltage V3 contains ripples.

This voltage V3 is applied to the voltage envelope detecting circuit 23, and by detecting the lower limit of the voltage, a voltage V4 having a waveform as shown in Fig. 3(b) can be obtained.

The voltage V4 and the voltage V2 output from the low-pass filter 21 are input to the adding circuit 24 and added, and a voltage V5 corresponding to the bias current component as shown in the third figure (c) can be obtained.

However, the voltage V5 remains with the chopping generated in the envelope detecting circuit 23. Therefore, the sampling signal of the predetermined timing generated by the display timing generating circuit 26 is used to perform sampling and holding in the sample and hold circuit so that the bias current has a constant value. Thereby, the voltage V6 corresponding to the bias current as shown in FIG. 3(d) can be obtained. Further, the subtraction circuit 22 and the addition circuit 24 may be constituted by an arithmetic amplifier, a transistor, or the like.

Fig. 4 shows an example of another circuit configuration of the bias current extraction circuit 9. This configuration corresponds to an example in which a microcomputer is used and a digital circuit system is used, and includes an A/D converter 31, a microcomputer 32, a timing signal generating circuit 33, and a D/A converter 34.

When the bias current extraction circuit 9 is used, the entire solar cell S other than the detection target unit is irradiated with only the light of the sub-light source 4 before the inspection of the solar cell S using the main light source 3 is started. In other words, only the first unit of the detection target is not irradiated with light, and the entire surface of the solar cell S other than the first unit is irradiated, and the bias current is detected in this state.

Next, the light of the sub-light source 4 is irradiated to the entire solar cell S other than the second cell, and the bias current value is detected. By using such a process, the non-irradiation object of the sub-light source 4 is switched, the detection of the bias current value of all the cells is completed, and the measured bias current value of the analog form is converted into digital data by the A/D converter 31. The data in the timing generated by the timing signal generating circuit 33 is stored in the microcomputer 32 in advance. When the data is read by the microcomputer 32, it is converted into an analog current bias current value by the D/A converter 34 and output.

After that, the inspection of the solar cell S is started. The irradiation target of the sub-light source 4 is switched as the main light source 3 of the irradiation detection target unit moves. With this switching, the data held by the microcomputer 32 can be read, and the bias current canceling circuit 10 subtracts the bias current value from the detected value, and only the generated current of the detecting target unit is obtained.

Figure 5 shows the timing of extracting the bias current component. Here, LED1 to LED5 are used as the sub-light source 4.

When the detection target unit is the first unit, the LED 1 located immediately below the first unit is turned off, and the LEDs 2 to 5 corresponding to all other units are turned on.

Next, before starting to detect the second unit as the detection target unit, the LED 1 is turned on, and the LED 2 is turned off to replace it. Other LED3~LED5 are dimensional Hold the light state. The timing of switching between the lighting and the extinction may be, for example, the boundary of the adjacent unit or the timing at which the main light source 3 moves toward the next detection target, or the like.

When the LEDs 1 to 5 are turned on or off according to the boundary of the adjacent unit, infrared rays, a laser sensor, or the like is used to detect the boundary of the unit. However, when outputting light from a sensor such as a laser sensor, it is preferable to use a smaller output than the main light source 3 for inspection.

Similarly, before starting to detect the third unit as the detection target unit, the LED 2 is turned on, and the LED 3 is turned off instead, and the other LEDs 1 and LED4 to LED5 are kept in the lighting state. Before starting the detection of the fourth unit as the detection target unit, the LED 3 is turned on, and the LED 4 is turned off, and the other LEDs 1 to 2 and 2 are kept lit. Before the detection of the fifth unit as the detection target unit, the LED 4 is turned on, and the LED 5 is turned off instead, and the other LEDs 1 to LED3 and the LED 5 are kept in the lighting state.

Through such a flow, the bias currents Ib1 to Ib5 of the first to fifth cells are output, and the current bias current value is obtained at a predetermined timing.

Referring to Fig. 6, a method of performing image display using the light starting current generated by the solar cell S will be described.

As shown in Fig. 6(a), for a solar cell having a surface defect (crack), in the direction orthogonal to the mark wires protruding at both ends, the laser light of the autonomous light source 3 will be left to right from the figure. Come scan. The generated currents I1, I2, ..., In (n is an integer of 2 or more) obtained thereby include current components corresponding to the defect positions on the respective scanning lines.

The current value of the generated currents I1, I2, ..., In is used in a time series To connect, an oscilloscope or the like can be used to display a waveform as shown in Fig. 6(b). Next, by performing image processing on the generated currents I1, I2, ..., In, an image can be displayed and a defect can be specified as shown in Fig. 6(c).

Figure 7 shows an image corresponding to the detected current value before the bias current is cancelled. The detected current value corresponds to the voltage generated across the shunt resistor 7 shown in Fig. 1, and is added to the start current and the bias current generated by the detection target unit.

Here, the solar cell unit is a string of three cells that have been connected in series. Since each unit has a different resistance, it is known that the bias currents are also different.

Figure 8 shows an inspection image of the string before the bias current is cancelled. In the figure, when the solar cell on the left side is the unit 1, the unit in the center is the unit 2, and the unit on the right side is the unit 3, the unit 2 and the unit 3 will exceed the input range of the detection system, because the processing limit of the image data is exceeded. Image data cannot be obtained because image processing cannot be performed.

Fig. 9 shows an image corresponding to the detected current value after the bias current is cancelled. It can be seen that the detected value of the generated current based on 0 V is obtained from the first unit 1 located on the left side.

Figure 10 shows an inspection image of the string after the bias current is cancelled. It can be seen that in all of the cells 1 to 3, image data showing defects (cracks) can be obtained without being affected by the bias current, and the examiner can recognize the image data.

In the method of detecting the light-starting current generated by the solar cell and detecting the defective portion, in order to correctly image the defective portion of the generated current based on the detection target unit, it is necessary to detect and offset the detection current. Bias current. According to this embodiment, by detecting only the startup current as described above, it is possible to return It is avoided that the crystal form of the EL method is a dark portion and it is difficult to specify a defect portion.

Each of the above embodiments is an example, and can be modified into various types within the technical scope of the present invention.

1‧‧‧mounting table

2‧‧‧Check the pins

3‧‧‧Main light source

4‧‧‧Sub Light Source

5‧‧‧Light source control circuit

6‧‧‧Mobile agencies

7‧‧‧Shunt resistor

8‧‧‧Amplifier

9‧‧‧Butable current extraction circuit

10‧‧‧Bias Current Offset Circuit

11‧‧‧Shielding circuit

12, 31‧‧‧A/D converter

13‧‧‧Image processing device

14‧‧‧ display

21‧‧‧low pass filter

22‧‧‧Subtraction circuit

23‧‧‧Envelope Detection Circuit

24‧‧‧Addition circuit

25‧‧‧Sampling and holding circuit

26, 33‧‧‧ timing signal generation circuit

32‧‧‧Microcomputer

34‧‧‧D/A converter

S‧‧‧ solar battery

I1, I2~In‧‧‧ generating current

Ib1~Ib5‧‧‧ bias current

LED1~LED5‧‧‧Sub Light Source

V1~V6‧‧‧ voltage

Fig. 1 is a perspective view showing the overall configuration of a defect inspection device for a solar cell according to an embodiment of the present invention.

Fig. 2 is a circuit diagram showing a configuration example of a bias current extraction circuit in the same defect inspection device.

The third (a) to (d) diagrams are graphs showing the voltage waveforms of the respective portions of the bias current extraction circuit having the configuration shown in Fig. 2.

Fig. 4 is a circuit diagram showing another configuration example of the bias current extraction circuit in the same defect inspection device.

Fig. 5 is a timing chart showing the timing of extracting the bias current in the same bias current drawing circuit.

The sixth (a) to (c) diagrams are explanatory diagrams showing a method of imaging with the detection value of the generated current by the defect inspection device.

Fig. 7 is a graph showing the detected current before the bias current is offset in the defect inspection device.

Fig. 8 is an explanatory view showing an inspection image before the bias current is canceled in the defect inspection device.

Fig. 9 is a graph showing the detected current after canceling the bias current in the defect inspection device.

Figure 10 shows the inspection chart after offsetting the bias current in the same defect inspection device. Like the illustration.

1‧‧‧mounting table

2‧‧‧Check the pins

3‧‧‧Main light source

4‧‧‧Sub Light Source

5‧‧‧Light source control circuit

6‧‧‧Mobile agencies

7‧‧‧Shunt resistor

8‧‧‧Amplifier

9‧‧‧Butable current extraction circuit

10‧‧‧Bias Current Offset Circuit

11‧‧‧Shielding circuit

12‧‧‧A/D converter

13‧‧‧Image processing device

14‧‧‧ display

S‧‧‧ solar battery

Claims (4)

A solar cell defect inspection device for inspecting a defect of a solar cell in which a plurality of cells are connected in series is characterized in that: a main light source is included, and a unit that detects a target object in the unit is irradiated with light; And illuminating the unit of the non-detection object in the unit; the light source control circuit controls the illuminance of the main light source and the sub-light source respectively, so that the illuminance of the sub-light source is higher than the illuminance of the main light source; current voltage conversion Is given to the current output by the solar cell and converted into a voltage and output; the amplifier is given the voltage output by the current-voltage converter, and is amplified and output; bias The current extraction circuit extracts and outputs a bias current included in an output from the amplifier; the bias current cancellation circuit subtracts the output from the amplifier from the bias current extraction circuit The aforementioned bias current is output to the output; the A/D converter converts the output from the aforementioned bias current cancellation circuit The digital data is output to the image processing device, and the image processing device performs image processing on the digital data outputted by the A/D converter and outputs the image data; and the display is provided to the image processing device. The image data is displayed and displayed, and the defect inspection device is based on the bias current The starting current component that has been generated by the unit of the detection object is checked. The solar cell defect inspection device according to claim 1, wherein the bias current extraction circuit has a low-pass filter that is supplied with an output from the amplifier as a first voltage, and outputs a high-frequency component. a second voltage; a subtraction circuit that supplies the first voltage and the second voltage, and outputs a third voltage that includes the high frequency component by subtracting the second voltage from the first voltage; a voltage envelope The detection circuit is provided with the third voltage, and outputs a fourth voltage that has detected the lower limit of the voltage; and the adding circuit supplies the second voltage and the fourth voltage, and outputs the second voltage. a fifth voltage that is added to the fourth voltage; the sample-and-hold circuit is supplied with the fifth voltage, and the sixth voltage that has been sampled and held at a predetermined timing is used as the bias current and is output; and the moving mechanism And moving the main light source toward a longitudinal direction of the solar cell, and the defect inspection device moves the unit to the detection target by the moving mechanism Between the time point corresponding to, or corresponding to timing of the series connection portion of the unit, obtaining a flow of the bias current to be detected of the unit. The solar cell defect inspection device of claim 1, wherein the bias current extraction circuit has an A/D converter that is supplied with an output from the amplifier and converted into a digital signal and outputter. ; The microcomputer, at a predetermined timing, stores the output from the A/D converter as a bias current detection data; the D/A converter converts the bias current detection data stored in the microcomputer into an analogy a signal outputting as the bias current; and a moving mechanism for moving the main light source toward the longitudinal direction of the solar cell, and detecting each bias current of each unit before the inspection starts The bias current detection data is stored in the microcomputer; and the defect inspection device is at a timing corresponding to a time point at which the main light source has been moved toward the unit to be detected by the moving mechanism, or a unit connected in series The timing corresponding to the connection portion outputs the bias current detection data stored by the microcomputer, and the bias current is outputted by the D/A converter. A method for inspecting a defect of a solar cell is a defect of a solar cell in which a plurality of cells have been connected in series, and is characterized in that the method comprises the steps of: illuminating a unit of the detection target in the unit with a first illuminance by a main light source; Light, by means of a secondary light source, illuminating a unit of the non-detection target in the unit with a second illuminance higher than the first illuminance; and extracting a current included in the solar cell by a bias current extraction circuit a bias current; the current output from the solar cell is offset by the bias current offset circuit; and Image processing is performed using the output from the bias current canceling circuit and displayed on the display, whereby the inspection is performed based on the starting current component that has been subjected to the aforementioned bias current and the unit of the detection target has generated power.