CN108923750B - Photovoltaic device capacitance-voltage characteristic curve test method - Google Patents

Abstract

The invention provides a photovoltaic device capacitance-voltage characteristic curve testing method based on hysteresis effect analysis, which is based on a conventional photovoltaic device current-voltage curve measuring method and comprises the steps of firstly measuring a series of current-voltage curves of a photovoltaic device under the test conditions of different scanning time and the same scanning point number, testing the photovoltaic device in two scanning directions of 0V to open-circuit voltage (forward scanning) and 0V (reverse scanning) under each test condition, and then calculating the capacitance-voltage curve of the photovoltaic device to be tested by using a hysteresis effect equation derived from an equivalent circuit of the photovoltaic device and applying a numerical algorithm. The testing method can obtain the capacitance-voltage characteristic curve of the photovoltaic device only by conventional current-voltage curve testing equipment. The testing method provided by the invention can accurately test the capacitance-voltage characteristic curve of the high-efficiency photovoltaic device and is beneficial to evaluating the interface state and the defect density of the photovoltaic device.

Description

Photovoltaic device capacitance-voltage characteristic curve test method

technical field

The invention belongs to the field of photovoltaic testing, in particular to a method for testing capacitance-voltage characteristic curves of high-efficiency photovoltaic devices based on hysteresis effect analysis.

Background technique

With the rapid development of the photovoltaic industry and the continuous updating of photovoltaic device technology, its characteristic characterization plays an increasingly important role in the improvement of the device process. The test of the capacitance-voltage characteristic curve can be used to study the defects and interface states of photovoltaic devices, and then use Based on its process parameters and analyzing the failure mechanism, it provides a basis for the performance improvement of photovoltaic devices.

Generally, the capacitance-voltage characteristic curve test of photovoltaic devices needs to load a variable DC bias voltage at the two poles of the test sample, and at the same time use a small AC voltage signal of a certain frequency for measurement. According to the equivalent diode circuit model of the photovoltaic device under test, the relationship between the frequency of the applied AC voltage signal and the impedance value of the photovoltaic device under test, the capacitance value of the photovoltaic device under the corresponding DC bias voltage can be deduced. The relationship between capacitance and voltage of photovoltaic devices is helpful for the study of doping concentration, defect level and interface state in photovoltaic devices.

The capacitance value of ordinary photovoltaic devices is generally in the order of picofarads to nanofarads; for high-efficiency photovoltaic cells, the capacitance at the maximum power point can reach 20μF/cm ² , and the capacitance value at the open circuit voltage can even reach the order of millifarads , far exceeding the effective range of most capacitance-voltage characteristic curve test instruments; due to the power level limitation, the existing capacitance-voltage characteristic curve tester is only suitable for small-area solar cells, but cannot test photovoltaic modules; in addition, capacitance- Voltage curve testers are not conventional equipment in photovoltaic testing laboratories, and additional special equipment needs to be purchased for capacitance testing of photovoltaic devices, resulting in an increase in testing costs.

To sum up, the test of the capacitance-voltage curve of photovoltaic devices is very necessary, but the existing test equipment and test methods still have major shortcomings, especially for high-efficiency photovoltaic devices, the higher capacitance value often affects the To the performance testing and practical use of photovoltaic devices, a new method for the capacitance-voltage characteristic curve of high-efficiency photovoltaic devices needs to be established.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a photovoltaic device capacitance-voltage characteristic curve testing method based on hysteresis effect analysis, which is used to solve the problem of high capacitance value of high-efficiency photovoltaic devices in the prior art. Issues affecting the performance testing and actual use of photovoltaic devices.

In order to achieve the above purpose and other related purposes, the present invention provides a photovoltaic device capacitance-voltage characteristic curve test method based on hysteresis effect analysis, comprising the following steps: 1) based on the photovoltaic device current-voltage characteristic curve test standard and test process, Under the simulated light source, by adjusting the test parameters of the current-voltage characteristic curve tester, multiple groups of current-voltage characteristic curves of the photovoltaic device under test with hysteresis error with the same number of scanning points and different scanning times under different scanning directions are obtained; 2 ) Calculate the hysteresis error values of the two current-voltage characteristic curves under the same test parameters and the first scanning direction and the second scanning direction under different bias voltages; 3) Combine the data of the different current-voltage characteristic curves And the hysteresis error value under the corresponding bias voltage is substituted into the hysteresis effect equation of the photovoltaic device, and a numerical algorithm is used to obtain the capacitance value of the photovoltaic device under different bias voltages, and the capacitance-voltage characteristic curve is obtained at the same time.

Preferably, the photovoltaic device is a high-efficiency silicon-based photovoltaic device.

Further, the high-efficiency silicon-based photovoltaic device includes, but is not limited to, one of a silicon heterojunction photovoltaic device and a silicon-based photovoltaic device with a passivated emitter backside contact.

Preferably, the capacitance at the maximum power point of the photovoltaic device is not less than 20 μF/cm 2 .

Preferably, the first scanning direction of the two current-voltage characteristic curves in different scanning directions in step 2) is from 0 volts to open circuit voltage, and the second scanning direction is from open circuit voltage to 0 volts.

Preferably, step 1) also includes the current-voltage characteristic curve test standard and test process based on the photovoltaic device, and the same number of scan points in different scanning directions is obtained by adjusting the test parameters of the current-voltage characteristic curve tester under the simulated light source. and at least one set of current-voltage characteristic curves of the photovoltaic device to be tested without hysteresis error at different scanning times; step 2) also includes obtaining different biases through the at least one set of current-voltage characteristic curves of the photovoltaic device to be tested without hysteresis error The output current value of the photovoltaic device without hysteresis error under the voltage; Step 3) further includes substituting the output current value of the photovoltaic device without hysteresis error under the corresponding bias voltage into the hysteresis effect equation.

Preferably, in step 2), the calculation formula for calculating the hysteresis error value ε _t(V) of the two current-voltage characteristic curves under the same test parameters and different scanning directions under different bias voltages is:

Wherein, P _t(V)f and P _t(V)r in the above formula are the powers of the respective bias voltages V during the first scan and the second scan, respectively.

Preferably, the algorithm for calculating the current-voltage characteristic curve of a high-efficiency photovoltaic device is based on the following hysteresis effect equation:

Among them, the meanings represented by each symbol in the above formula are as follows:

ε _t(V) is the hysteresis error of the two current-voltage characteristic curves with different scanning directions and the same scanning parameters under different bias voltages V, where the hysteresis error is equal to the power of the corresponding two current-voltage characteristic curves when the voltage is V The difference is divided by the sum of the power;

_Req(V) is the equivalent resistance of the photovoltaic device in the diode equivalent circuit under different bias voltages V;

I _(V) is the output current value of the photovoltaic device without hysteresis error under different bias voltages V;

t is the effective voltage holding time of each scan point;

△V is the voltage difference between adjacent test points in the current-voltage characteristic curve test of photovoltaic devices, which is inversely proportional to the number of scanning points;

C _d(V) is the capacitance value corresponding to different bias voltages V.

The hysteresis effect formula involved in the test method can be obtained from the equivalent circuit model of the photovoltaic device simplified by Thevenin's theorem, as shown in FIG. 3 .

Preferably, the testing method is a method for obtaining a corresponding capacitance-voltage characteristic curve based on a photovoltaic device current-voltage characteristic curve.

As mentioned above, the method for testing the capacitance-voltage characteristic curve of photovoltaic devices based on hysteresis effect analysis of the present invention has the following beneficial effects:

1) The test method of the present invention can obtain the capacitance-voltage curve of the photovoltaic device by repeatedly testing the current-voltage characteristic curve of the high-efficiency photovoltaic device without changing the hardware structure of the existing long-pulse steady-state analog light source.

2) The testing method of the present invention can accurately test the capacitance-voltage characteristic curve of a high-efficiency photovoltaic device, which is helpful for evaluating the interface state and defect density of the photovoltaic device.

3) The test method of the present invention is not only applicable to the test of the capacitance-voltage characteristic curve of a monolithic high-efficiency photovoltaic cell, but also to the test of the capacitance-voltage characteristic curve of a photovoltaic module.

Description of drawings

FIG. 1 is a graph showing the capacitance-voltage characteristic curve of the high-efficiency photovoltaic module in the present invention.

FIG. 2 shows a test flow chart of a method for testing capacitance-voltage characteristic curves of photovoltaic devices based on hysteresis effect analysis in Example 1 of the present invention.

FIG. 3 shows a simplified model of the equivalent circuit of the photovoltaic device in the present invention.

FIG. 4 shows a test flow chart of a method for testing capacitance-voltage characteristic curves of photovoltaic devices based on hysteresis effect analysis in Example 2 of the present invention.

Component label description

S11～S13 Embodiment 1 Step 1)～Step 3)

S21～S23 Step 1)～Step 3) of Example 2

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to Figure 1 to Figure 4. It should be noted that the diagrams provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the diagrams only show the components related to the present invention rather than the number, shape and the number of components in the actual implementation. For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

Example 1

As shown in FIG. 2 and FIG. 3 , this embodiment provides a method for testing capacitance-voltage characteristic curves of photovoltaic devices based on hysteresis effect analysis, including the following steps:

As shown in FIG. 2 , step 1) S11 is first performed, based on the current-voltage characteristic curve test standard and test process of the photovoltaic device, under the simulated light source, different scanning directions are obtained by adjusting the test parameters of the current-voltage characteristic curve tester Below, multiple sets of current-voltage characteristic curves of the photovoltaic device under test with hysteresis error with the same number of scan points and different scan times.

The photovoltaic device is a high-efficiency silicon-based photovoltaic device. Further, the high-efficiency silicon-based photovoltaic device includes, but is not limited to, one of a silicon heterojunction photovoltaic device and a silicon-based photovoltaic device with a passivated emitter backside contact. For example, the capacitance at the maximum power point of the photovoltaic device is not less than 20 μF/cm ² , and the capacitance-voltage characteristic curve of the high-efficiency photovoltaic module in the present invention is shown in FIG. 1 .

As shown in FIG. 2 , step 2) S12 is performed to calculate the hysteresis error values of the two current-voltage characteristic curves under different bias voltages under the same test parameters and the first scanning direction and the second scanning direction.

The first scanning direction of the two current-voltage characteristic curves under different scanning directions is from 0 volts to open-circuit voltage, the first scanning direction can be defined as a forward scanning direction, and the second scanning direction can be defined as a forward scanning direction. The direction is from the open circuit voltage to 0 volts, and the second scan direction can be defined as the reverse scan direction.

As shown in Figure 2, step 3) S13 is finally performed, the data of the different current-voltage characteristic curves and the hysteresis error value under the corresponding bias voltage are substituted into the photovoltaic device hysteresis effect equation, and a numerical algorithm is used to obtain the photovoltaic device. Capacitance values under different bias voltages, while obtaining capacitance-voltage characteristic curves.

In step 2), the calculation formula for calculating the hysteresis error value ε _t(V) of the two current-voltage characteristic curves under the same test parameters and different scanning directions under different bias voltages is:

Wherein, P _t(V)f and P _t(V)r in the above formula are the powers of the respective bias voltages V during the first scan and the second scan, respectively.

In step 3), the algorithm for calculating the current-voltage characteristic curve of the high-efficiency photovoltaic device is based on the following hysteresis effect equation:

Among them, the meanings represented by each symbol in the above formula are as follows:

ε _t(V) is the hysteresis error of the two current-voltage characteristic curves with different scanning directions and the same scanning parameters under different bias voltages V, where the hysteresis error is equal to the power of the corresponding two current-voltage characteristic curves when the voltage is V The difference is divided by the sum of the power;

_Req(V) is the equivalent resistance of the photovoltaic device in the diode equivalent circuit under different bias voltages V;

I _(V) is the output current value of the photovoltaic device without hysteresis error under different bias voltages V;

t is the effective voltage holding time of each scanning point, and the effective voltage holding time is the above-mentioned scanning time;

△V is the voltage difference between adjacent test points in the current-voltage characteristic curve test of photovoltaic devices, which is inversely proportional to the number of scanning points;

C _d(V) is the capacitance value corresponding to different bias voltages V.

The hysteresis effect formula involved in the test method can be obtained from the equivalent circuit model of the photovoltaic device simplified by Thevenin's theorem, as shown in FIG. 3 . The simplified equivalent circuit of the photovoltaic device is a conventional resistor-capacitor (R-C) circuit. Using the discharge characteristics of the resistor-capacitor circuit, the power expressions under different scanning directions are deduced respectively, and the hysteresis error calculation formula can be substituted into the simplification. The hysteresis effect equation.

In general, the method for testing capacitance-voltage characteristic curves of photovoltaic devices based on hysteresis effect analysis is a method for obtaining corresponding capacitance-voltage characteristic curves based on the current-voltage characteristic curves of photovoltaic devices.

Example 2

As shown in FIG. 4 , this embodiment provides a method for testing capacitance-voltage characteristic curves of photovoltaic devices based on hysteresis effect analysis, including the following steps:

As shown in FIG. 4 , first step 1) S21 is performed, based on the current-voltage characteristic curve test standard and test process of the photovoltaic device, under the simulated light source, different scanning directions are obtained by adjusting the test parameters of the current-voltage characteristic curve tester Under the same scanning points and different scanning times, multiple groups of current-voltage characteristic curves of the photovoltaic device to be tested with hysteresis error are obtained by adjusting the test parameters of the current-voltage characteristic curve tester under the simulated light source. Under different scanning directions, at least one group of current-voltage characteristic curves of the photovoltaic device to be tested without hysteresis error with the same number of scanning points and different scanning times.

The photovoltaic device is a high-efficiency silicon-based photovoltaic device. Further, the high-efficiency silicon-based photovoltaic device includes one of a silicon heterojunction photovoltaic device and a silicon-based photovoltaic device with a back contact of a passivated emitter. For example, the capacitance at the maximum power point of the photovoltaic device is not less than 20 μF/cm ² , and the capacitance-voltage characteristic curve of the high-efficiency photovoltaic module in the present invention is shown in FIG. 1 .

As shown in Figure 4, then step 2) S22 is performed to calculate the hysteresis error values of the two current-voltage characteristic curves under different bias voltages under the same test parameters and the first scanning direction and the second scanning direction, and at the same time, The hysteresis-free output current value of the photovoltaic device under different bias voltages is obtained through the at least one set of current-voltage characteristic curves of the photovoltaic device to be tested without hysteresis error.

The first scanning direction of the two current-voltage characteristic curves under different scanning directions is from 0 volts to open-circuit voltage, the first scanning direction can be defined as a forward scanning direction, and the second scanning direction can be defined as a forward scanning direction. The direction is from the open circuit voltage to 0 volts, and the second scan direction can be defined as the reverse scan direction.

As shown in FIG. 4 , step 3) S23 is finally performed, and the data of the different current-voltage characteristic curves and the hysteresis error value under the corresponding bias voltage and the no-voltage of the photovoltaic device under the corresponding bias voltage are compared. The hysteresis error output current value is substituted into the hysteresis effect equation into the hysteresis effect equation of the photovoltaic device, and a numerical algorithm is used to obtain the capacitance value of the photovoltaic device under different bias voltages, and simultaneously obtain the capacitance-voltage characteristic curve.

In step 2), the calculation formula for calculating the hysteresis error value ε _t(V) of the two current-voltage characteristic curves under the same test parameters and different scanning directions under different bias voltages is:

Wherein, P _t(V)f and P _t(V)r in the above formula are the powers of the respective bias voltages V during the first scan and the second scan, respectively.

In step 3), the algorithm for calculating the current-voltage characteristic curve of the high-efficiency photovoltaic device is based on the following hysteresis effect equation:

Among them, the meanings represented by each symbol in the above formula are as follows:

ε _t(V) is the hysteresis error of the two current-voltage characteristic curves with different scanning directions and the same scanning parameters under different bias voltages V, where the hysteresis error is equal to the power of the corresponding two current-voltage characteristic curves when the voltage is V The difference is divided by the sum of the power;

_Req(V) is the equivalent resistance of the photovoltaic device in the diode equivalent circuit under different bias voltages V;

I _(V) is the output current value of the photovoltaic device without hysteresis error under different bias voltages V, which can be obtained from the above steps 1) and 2);

t is the effective voltage holding time of each scanning point, and the effective voltage holding time is the above-mentioned scanning time;

△V is the voltage difference between adjacent test points in the current-voltage characteristic curve test of photovoltaic devices, which is inversely proportional to the number of scanning points;

C _d(V) is the capacitance value corresponding to different bias voltages V.

The hysteresis effect formula involved in the test method can be obtained from the equivalent circuit model of the photovoltaic device simplified by Thevenin's theorem, as shown in FIG. 3 .

In general, the method for testing capacitance-voltage characteristic curves of photovoltaic devices based on hysteresis effect analysis is a method for obtaining corresponding capacitance-voltage characteristic curves based on the current-voltage characteristic curves of photovoltaic devices.

As mentioned above, the method for testing the capacitance-voltage characteristic curve of photovoltaic devices based on hysteresis effect analysis of the present invention has the following beneficial effects:

1) The test method of the present invention can obtain the capacitance-voltage curve of the photovoltaic device by repeatedly testing the current-voltage characteristic curve of the high-efficiency photovoltaic device without changing the hardware structure of the existing long-pulse steady-state analog light source.

2) The testing method of the present invention can accurately test the capacitance-voltage characteristic curve of a high-efficiency photovoltaic device, which is helpful for evaluating the interface state and defect density of the photovoltaic device.

3) The test method of the present invention is not only applicable to the test of the capacitance-voltage characteristic curve of a monolithic high-efficiency photovoltaic cell, but also to the test of the capacitance-voltage characteristic curve of a photovoltaic module.

Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (7)

1. A method for testing a capacitance-voltage characteristic curve of a photovoltaic device based on hysteresis effect analysis is characterized in that the photovoltaic device is a high-efficiency silicon-based photovoltaic device and comprises the following steps:

1) based on the current-voltage characteristic curve test standard and test flow of the photovoltaic device, a plurality of groups of current-voltage characteristic curves of the photovoltaic device to be tested with hysteresis errors in different scanning directions and at the same scanning point number and different scanning time are obtained by adjusting test parameters of the current-voltage characteristic curve tester under a simulated light source;

2) calculating hysteresis error values of two current-voltage characteristic curves under the same test parameters and the first scanning direction and the second scanning direction under different bias voltages;

3) substituting the data of the different current-voltage characteristic curves and the hysteresis error value under the corresponding bias voltage into a photovoltaic device hysteresis effect equation, obtaining capacitance values of the photovoltaic device under different bias voltages by using a numerical algorithm, and obtaining a capacitance-voltage characteristic curve at the same time;

the algorithm for calculating the current-voltage characteristic curve of the high-efficiency photovoltaic device is based on the following hysteresis effect equation:

wherein, the meaning represented by each symbol in the above formula is as follows:

_t(V)the hysteresis error of two current-voltage characteristic curves in different scanning directions and with the same scanning parameters under different bias voltages V is equal to the sum of the power divided by the difference of the power of the two current-voltage characteristic curves when the voltage is V;

R_eq(V)the equivalent resistance of the photovoltaic device in the diode equivalent circuit under different bias voltages V;

I_(V)outputting a current value without hysteresis error of the photovoltaic device under different bias voltages V;

t is the effective voltage holding time of each scanning point;

the delta V is the voltage difference of adjacent test points in the photovoltaic device current-voltage characteristic curve test, and the numerical value is in inverse proportion to the number of scanning points;

C_d(V)the capacitance values correspond to different bias voltages V.

2. The hysteresis effect analysis-based photovoltaic device capacitance-voltage characteristic curve testing method according to claim 1, wherein: the high-efficiency silicon-based photovoltaic device comprises a silicon heterojunction photovoltaic device and one of silicon-based photovoltaic devices with passivated emitter back contacts.

3. The hysteresis effect analysis-based photovoltaic device capacitance-voltage characteristic curve testing method according to claim 1, wherein: the capacitance at the maximum power point of the photovoltaic device is not less than 20 [ mu ] F/cm²。

4. The hysteresis effect analysis-based photovoltaic device capacitance-voltage characteristic curve testing method according to claim 1, wherein: the first scanning direction of the two current-voltage characteristic curves in the different scanning directions in the step 2) is from 0 volt to an open-circuit voltage, and the second scanning direction is from the open-circuit voltage to 0 volt.

5. The hysteresis effect analysis-based photovoltaic device capacitance-voltage characteristic curve testing method according to claim 1, wherein: the method comprises the following steps that 1) a current-voltage characteristic curve testing standard and a testing process based on the photovoltaic device are further included, and at least one group of current-voltage characteristic curves of the photovoltaic device to be tested, which have no hysteresis error, in different scanning directions, the same number of scanning points and different scanning times are obtained by adjusting testing parameters of a current-voltage characteristic curve tester under a simulated light source; step 2) obtaining the hysteresis error-free output current value of the photovoltaic device under different bias voltages through the at least one group of current-voltage characteristic curves of the photovoltaic device to be tested without hysteresis errors; and 3) substituting the output current value without the hysteresis error of the photovoltaic device under the corresponding bias voltage into the hysteresis effect equation.

6. The hysteresis effect analysis-based photovoltaic device capacitance-voltage characteristic curve testing method according to claim 1, wherein: in step 2), calculating the hysteresis error value of two current-voltage characteristic curves under the same test parameters and different scanning directions under different bias voltages_t(V)The calculation formula of (2) is as follows:

wherein, in the above formula, P_t(V)fAnd P_t(V)rThe power of each bias voltage V at the first scan and the second scan, respectively.

7. The hysteresis effect analysis-based photovoltaic device capacitance-voltage characteristic curve testing method according to claim 1, wherein: the testing method is a method for acquiring a corresponding capacitance-voltage characteristic curve based on a current-voltage characteristic curve of a photovoltaic device.

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