Heterojunction battery IV curve test method and test device

Abstract

The present invention provides a test method and a test device for an IV curve of a heterojunction battery. The test method comprises the following steps: performing an initial forward scan and an initial reverse scan on the heterojunction battery to obtain an initial forward scan current-voltage curve and an initial reverse scan current-voltage curve; calculating and obtaining a forward scan power curve and a reverse scan power curve, wherein the forward scan power curve and the reverse scan power curve form a closed area in a power-voltage coordinate system; dividing the closed area into a plurality of closed sub-areas by a plurality of straight lines perpendicular to the voltage axis; performing a second forward scan and a second reverse scan on the heterojunction battery according to the change in the area of ​​the closed sub-areas; forming a second forward scan current-voltage curve and a second reverse scan current-voltage curve, and fitting the second forward scan current-voltage curve and the second reverse scan current-voltage curve to obtain a final current-voltage curve. The above test method can eliminate the test error introduced by the hysteresis effect.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell testing, and in particular to a testing method and a testing device for an IV curve of a heterojunction cell. Background Art

[0002] In the process of manufacturing solar cells, accurate testing of the electrical properties of solar cells is crucial. It helps to analyze the differences in the high and low grades of the produced solar cells, find the causes of the differences and make process improvements.

[0003] At present, the testing methods for solar cells are to simulate sunlight and apply external load tests. The simulator simulates sunlight with an irradiance of 1000. The solar cell is connected in parallel with the load while receiving light. In the process of the load slowly increasing from zero at the beginning, because the resistance of the load is small, the current almost flows through the load instead of through the parallel resistance. At this time, the current of the load represents the current of the solar cell; as the load resistance increases, when it increases to a certain extent and approaches infinity, the voltage across the series resistance can be ignored, and the voltage across the load represents the voltage of the solar cell. The data is reflected in the coordinate system (the horizontal axis x represents the voltage, and the vertical axis y represents the current), which will form a curve from left to right and gradually bends toward the x-axis. This curve is the volt-ampere characteristic curve of the solar cell, also called the IV curve. The current testing method calculates various parameters of battery performance through the IV curve.

[0004] In heterojunction solar cells, the gate electrodes on both sides, the upper and lower transparent conductive films, the N-type doped film, the P-type doped film, and the upper and lower intrinsic amorphous silicon films and the N-type silicon substrate that play a passivation role are equivalent to a capacitor. The multi-layer film and the N-type silicon substrate constitute the dielectric medium of the capacitor; the formation of this capacitance will lead to the generation of hysteresis effect, which in turn affects the test and affects the test accuracy. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to eliminate the test error introduced by the hysteresis effect.

[0006] The invention provides a method for testing an IV curve of a heterojunction battery, comprising the following steps: performing an initial forward scan and an initial reverse scan on the heterojunction battery to obtain an initial forward scan current-voltage curve and an initial reverse scan current-voltage curve respectively; calculating and obtaining a forward scan power curve and a reverse scan power curve according to the initial forward scan current-voltage curve and the initial reverse scan current-voltage curve, wherein the forward scan power curve and the reverse scan power curve form a closed area in a power-voltage coordinate system; dividing the closed area into a plurality of closed sub-areas by using a plurality of straight lines perpendicular to a voltage axis; performing a secondary forward scan and a secondary reverse scan on the heterojunction battery according to a change in the area of ​​the closed sub-areas, and respectively forming a secondary forward current-voltage curve and a secondary reverse current-voltage curve through the secondary forward scan and the secondary reverse scan, wherein: at each of the closed sub-areas, the time of the secondary forward scan and the time of the secondary reverse scan are proportional to the area of ​​the corresponding closed sub-area; and fitting the secondary forward current-voltage curve and the secondary reverse current-voltage curve to obtain a final current-voltage curve.

[0007] Optionally, the sum of the time of the initial forward scan and the time of the initial reverse scan is 20ms to 40ms; the sum of the time of the secondary forward scan and the time of the secondary reverse scan is 80ms to 160ms.

[0008] Optionally, the first scanning time is divided into a number of first sub-scanning times, and the first sub-scanning times correspond to the closed sub-regions one-to-one; the ratio of each of the first sub-scanning times to the first scanning time is equal to the ratio of the area of ​​each of the closed sub-regions to the area of ​​the closed region; the second scanning time is divided into a number of second sub-scanning times, and the second sub-scanning times correspond to the closed sub-regions one-to-one, and the ratio of each of the second sub-scanning times to the second scanning time is equal to the ratio of the area of ​​each of the closed sub-regions to the area of ​​the closed region.

[0009] Optionally, the closed sub-areas are distributed on the voltage axis at equal intervals from a first area to an Mth area, where M is an integer greater than or equal to 2.

[0010] Optional, M is 700-800.

[0011] Optionally, the test conditions for the initial forward scan of the heterojunction cell include: irradiance of 900W / m 2 ~1100W / m 2 ; The test conditions for the initial reverse scan of the heterojunction cell include: irradiance of 900W / m 2 ~1100W / m 2 .

[0012] Optionally, the range of the forward scan is from 0 volts to open circuit voltage, and the range of the reverse scan is from open circuit voltage to 0 volts.

[0013] The present invention also provides a testing device for the IV curve of a heterojunction battery, which is used to implement the above-mentioned testing method for the IV curve of a heterojunction battery, including: a scanning time control unit, which is used to control a first scanning time when the heterojunction battery is forward scanned; and, which is used to control a second scanning time when the heterojunction battery is reversely scanned; a time division unit, which is used to divide the closed area into a plurality of closed sub-areas; and a calculation unit, which is used to calculate and obtain a forward scanning power curve and a reverse scanning power curve, and to fit the secondary forward current-voltage curve and the secondary reverse current-voltage curve to obtain a final current-voltage curve.

[0014] Optionally, the scanning time control unit includes: a first scanning time control unit and a second scanning time control unit; the first scanning time control unit is used to control the first scanning time when the heterojunction battery is scanned forward; the second scanning time control unit is used to control the second scanning time when the heterojunction battery is scanned reversely.

[0015] Optionally, the time division unit includes: an input module, and the input module is used to input the number of the closed sub-areas.

[0016] The technical solution of the present invention has the following beneficial effects:

[0017] Since heterojunction batteries have more film structures, larger capacitance, and stronger hysteresis effects, the stronger the hysteresis effect, the longer it takes to accurately test. If the scanning time is not enough, during the forward scan, part of the current will charge the capacitor, so the collected current will be lower than the true value. During the reverse scan, the capacitor will discharge outward, so the collected current will be higher than the true value. If there is enough time to scan, you can wait until the charging and discharging are completed before collecting the current and voltage. From the initial forward scan current-voltage curve under the initial forward scan and the initial reverse scan current-voltage curve under the initial reverse scan, it can be seen that the maximum power point is greatly affected by the capacitor, so a longer scan time is required near the maximum power point to eliminate the hysteresis effect of the capacitor.

[0018] The test method of the IV curve of the heterojunction battery provided by the technical solution of the present invention forms a closed area in the power-voltage coordinate system by forward scanning power curve and reverse scanning power curve; the closed area is divided into several closed sub-areas by several straight lines perpendicular to the voltage axis, and the larger the area of ​​the closed sub-area, the greater the influence of the hysteresis effect of the capacitor of this part; the smaller the area of ​​the closed sub-area, the smaller the influence of the hysteresis effect of the capacitor of this part. Thus, the heterojunction battery can be subjected to a second forward scan and a second reverse scan, and at each closed sub-area, the time of the second forward scan and the time of the second reverse scan are proportional to the area of ​​the corresponding closed sub-area to cope with different capacitor hysteresis effects; a second forward current-voltage curve and a second reverse current-voltage curve are formed by the second forward scan and the second reverse scan, and the final current-voltage curve is obtained by fitting the second forward current-voltage curve and the second reverse current-voltage curve, so that the result of the final current-voltage curve is closer to the true value. Thus, the test error introduced by the hysteresis effect of the capacitor is eliminated, and the various parameters of the heterojunction battery obtained are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 Schematic diagram of an initial IV curve in a current-voltage coordinate system in an embodiment of the present application;

[0021] Figure 2 Schematic diagram of a PV curve in a power-voltage coordinate system in an embodiment of the present application;

[0022] Figure 3 It is a schematic diagram of a PV curve sub-region in a power-voltage coordinate system in an embodiment of the present application;

[0023] Figure 4 It is a schematic diagram of a quadratic IV curve in a current-voltage coordinate system in an embodiment of the present application;

[0024] Figure 5 It is an equivalent circuit diagram of IV test of heterojunction battery in the prior art;

[0025] Figure 6 This is a schematic diagram of the process of testing the IV curve of a heterojunction battery according to an embodiment of the present application;

[0026] Reference numerals:

[0027] 1. Initial forward sweep current-voltage curve; 2. Initial reverse sweep current-voltage curve; 3. Forward sweep power curve; 4. Reverse sweep power curve; 5. Secondary forward current-voltage curve; 6. Secondary reverse current-voltage curve; 7. Final current-voltage curve. DETAILED DESCRIPTION

[0028] When performing IV curve testing on heterojunction cells, when simulated light irradiates the solar cell, non-equilibrium carriers, namely electron carriers and hole carriers, will be excited inside the solar cell. Under the action of the built-in electric field of the PN junction, electron carriers will move to the n region to form current, and hole carriers will move to the p region under the action of the built-in electric field. The direction of positive charge movement is defined as the direction of current, so the current generated in the circuit is the sum of the currents formed by the movement of the two excited carriers.

[0029] The entire heterojunction battery will form a capacitor during testing. First, the directional movement of charges in the circuit will form a current. Due to the repulsion of like charges, the current is the largest at the beginning, and then it will gradually decrease. The charge of the capacitor is the smallest at the beginning of the charge movement, which is zero. During the charge movement process, the charge of the capacitor gradually increases, and the voltage between the upper and lower poles of the capacitor gradually increases. When the current gradually decreases to zero, the capacitor charging ends. When the light ends, the connection between the capacitor and the power supply is cut off, the capacitor will discharge, and the voltage between the two plates will gradually drop to zero. This capacitor charging and discharging process will cause errors in the process of testing the electrical performance of solar cells. During the forward scan, since part of the current will charge the capacitor, the collected current is lower than the true value; during the reverse scan, the capacitor will discharge outward, so the collected current will be higher than the true value; in the coordinate system, it is marked as two IV curves of different heights, and the difference between the two is caused by the hysteresis effect caused by the capacitor.

[0030] Circuit diagram reference for heterojunction battery voltammetry test Figure 5 , including: constant current source I ph , series resistance R s , parallel resistance R sh and adjustable external load R load The heterojunction battery has a first diode current I d1 and the second diode current I d2 .

[0031] Therefore, the present invention provides a method and a device for testing the IV curve of a heterojunction battery to eliminate the test error introduced by the hysteresis effect.

[0032] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Example 1

[0034] This embodiment provides a method for testing the IV curve of a heterojunction battery. Figure 6 , including the following steps:

[0035] Step S1: Perform an initial forward scan and an initial reverse scan on the heterojunction battery to obtain an initial forward scan current-voltage curve 1 and an initial reverse scan current-voltage curve 2, respectively. Figure 1 ;

[0036] Step S2: According to the initial forward sweep current-voltage curve 1 and the initial reverse sweep current-voltage curve 2, the forward sweep power curve 3 and the reverse sweep power curve 4 are calculated and obtained. The forward sweep power curve 3 and the reverse sweep power curve 4 form a closed area in the power-voltage coordinate system, with reference to Figure 2 ;

[0037] Step S3: Use a number of straight lines perpendicular to the voltage axis to divide the closed area into a number of closed sub-areas, referring to Figure 3 ;

[0038] Step S4: performing a second forward scan and a second reverse scan on the heterojunction battery according to the change in the area of ​​the closed sub-region, wherein at each closed sub-region, the time of the second forward scan and the time of the second reverse scan are proportional to the area of ​​the corresponding closed sub-region;

[0039] Step S5: After two forward scans and two reverse scans, a second forward current-voltage curve 5 and a second reverse current-voltage curve 6 are formed, and the second forward current-voltage curve 5 and the second reverse current-voltage curve 6 are fitted to obtain a final current-voltage curve 7, referring to Figure 4 .

[0040] In this embodiment, a closed area is formed in a power-voltage coordinate system by forward scanning power curve 3 and reverse scanning power curve 4; the closed area is divided into several closed sub-areas by several straight lines perpendicular to the voltage axis, and the larger the area of ​​the closed sub-area, the greater the influence of the hysteresis effect of the capacitor of this part; the smaller the area of ​​the closed sub-area, the smaller the influence of the hysteresis effect of the capacitor of this part. Thus, the heterojunction battery can be subjected to a secondary forward scan and a secondary reverse scan, and at each closed sub-area, the time of the secondary forward scan and the time of the secondary reverse scan are proportional to the area of ​​the corresponding closed sub-area to cope with different capacitor hysteresis effects; a secondary forward current-voltage curve 5 and a secondary reverse current-voltage curve 6 are formed by a secondary forward scan and a secondary reverse scan, and a final current-voltage curve 7 is obtained by fitting the secondary forward current-voltage curve 5 and the secondary reverse current-voltage curve 6, so that the result of the final current-voltage curve 7 is closer to the true value. Thus, the test error introduced by the hysteresis effect of the capacitor is eliminated, and the various parameters of the heterojunction battery obtained are more accurate.

[0041] In this embodiment, the forward scan is from 0 volts to the open circuit voltage, and the reverse scan is from the open circuit voltage to 0 volts. Specifically, during the forward scan test, the scan voltage value is 0V at the start time, and the scan voltage value is the maximum scan voltage of the heterojunction battery at the end time; during the reverse scan test, the scan voltage value is the maximum scan voltage of the heterojunction battery at the start time, and the scan voltage value is 0V at the end time.

[0042] Further, the sum of the initial forward scanning time for the initial forward scanning of the heterojunction battery and the initial reverse scanning time for the initial reverse scanning of the heterojunction battery is 20ms to 40ms; the sum of the first scanning time for the secondary forward scanning of the heterojunction battery according to the area of ​​each of the enclosed sub-regions and the second scanning time for the secondary reverse scanning of the heterojunction battery according to the area of ​​each of the enclosed sub-regions is 80ms to 160ms. Thus, on the basis of ensuring the test efficiency, the heterojunction battery is subjected to the secondary forward scanning IV curve test and the secondary reverse scanning IV curve test, and a longer scanning time is used for the enclosed sub-region with a larger area, so as to eliminate the test error introduced by the hysteresis effect of the capacitor, and then the final current-voltage curve 7 is obtained by fitting the secondary forward current-voltage curve 5 and the secondary reverse current-voltage curve 6, and the various parameters of the heterojunction battery are calculated according to the final current-voltage curve 7; because the test error introduced by the hysteresis effect of the capacitor is eliminated, the various parameters of the heterojunction battery obtained are more accurate.

[0043] Further, the first scanning time is divided into a number of first sub-scanning times, and the first sub-scanning times correspond to the closed sub-regions one-to-one; the ratio of each of the first sub-scanning times to the first scanning time is equal to the ratio of the area of ​​each of the closed sub-regions to the area of ​​the closed region; the second scanning time is divided into a number of second sub-scanning times, and the second sub-scanning times correspond to the closed sub-regions one-to-one, and the ratio of each of the second sub-scanning times to the second scanning time is equal to the ratio of the area of ​​each of the closed sub-regions to the area of ​​the closed region.

[0044] The IV curve test of the heterojunction battery is performed twice in the forward direction according to the time of each first sub-scanning time, and the IV curve test of the heterojunction battery is performed twice in the reverse direction according to the time of each second sub-scanning time. The test error introduced by the hysteresis effect of the capacitor is eliminated within a limited time, making the IV curve test value more accurate.

[0045] Furthermore, the closed sub-regions are equally spaced on the voltage axis from the first region to the Mth region, where M is an integer greater than or equal to 2. In the power-voltage coordinate system, since the spacing of each closed sub-region on the horizontal axis is equal, but the distances of the intersections with the forward scanning power curve and the reverse scanning power curve on the vertical axis are not equal, the area size of each closed sub-region can be intuitively seen, and it is also more convenient to accurately calculate the area of ​​the closed sub-region, thereby determining each first sub-scanning time or each second sub-scanning time corresponding to each closed sub-region.

[0046] In one embodiment, M is 700-800, 800, so that the secondary forward scan and the secondary reverse scan are divided into relatively more main test stages, and the time of each main test stage is distinguished to a certain extent, which better eliminates the hysteresis effect caused by the capacitance of the heterojunction battery.

[0047] In one embodiment, the test conditions for the initial forward scan of the heterojunction cell include: an irradiance of 900 W / m 2 ~1100W / m 2 , for example 1000W / m 2 .

[0048] The test conditions for the initial reverse scan of the heterojunction cell include: irradiance of 900W / m 2 ~1100W / m 2 , for example 1000W / m 2 .

[0049] Example 2

[0050] The present embodiment provides a heterojunction battery testing device, which is used to implement the above-mentioned heterojunction battery IV curve testing method, including: a scanning time control unit, which is used to control a first scanning time when the heterojunction battery is scanned in the forward direction; and, which is used to control a second scanning time when the heterojunction battery is scanned in the reverse direction; a time division unit, which is used to divide the closed area into a plurality of closed sub-areas; a calculation unit, which is used to calculate and obtain a forward scanning power curve and a reverse scanning power curve, and to fit the secondary forward current-voltage curve and the secondary reverse current-voltage curve to obtain a final current-voltage curve. By scanning the closed sub-region with a large influence of the hysteresis effect of the capacitor for a longer time, the test error introduced by the hysteresis effect of the capacitor is eliminated; then, a secondary forward current-voltage curve 5 and a secondary reverse current-voltage curve 6 are formed by secondary forward scanning and secondary reverse scanning, and the secondary forward current-voltage curve 5 and the secondary reverse current-voltage curve 6 are fitted to obtain a final current-voltage curve 7, so that the result of the final current-voltage curve 7 is closer to the true value, and various parameters of the heterojunction battery are calculated; since the test error introduced by the hysteresis effect of the capacitor is eliminated, the various parameters of the heterojunction battery obtained are more accurate.

[0051] Furthermore, the scanning time control unit includes: a first scanning time control unit and a second scanning time control unit; the first scanning time control unit is used to control the first scanning time when the heterojunction battery is scanned forward; the second scanning time control unit is used to control the second scanning time when the heterojunction battery is scanned reversely. Different control units are used to control the corresponding scanning time, and the scanning time control unit has high precision and good dynamic performance, and can improve the anti-interference ability of the scanning time control unit.

[0052] Furthermore, the time division unit includes: an input module, which is used to input the number of the closed sub-areas. As is well known, the more the number of closed sub-areas, the higher the test accuracy of the heterojunction battery test device, but the test time will also increase accordingly. By presetting the number of closed sub-areas before the test through the input module, the relationship between test accuracy and test efficiency can be effectively balanced.

[0053] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for testing IV curve of heterojunction battery, characterized in that: The steps include: Performing an initial forward scan and an initial reverse scan on the heterojunction battery to obtain an initial forward scan current-voltage curve and an initial reverse scan current-voltage curve, respectively; According to the initial forward sweep current-voltage curve and the initial reverse sweep current-voltage curve, a forward sweep power curve and a reverse sweep power curve are calculated and obtained, wherein the forward sweep power curve and the reverse sweep power curve form a closed area in a power-voltage coordinate system; Dividing the closed area into a number of closed sub-areas using a number of straight lines perpendicular to the voltage axis; According to the change of the area of ​​the closed sub-region, the heterojunction battery is subjected to a second forward scan and a second reverse scan, and a second forward current-voltage curve and a second reverse current-voltage curve are formed through the second forward scan and the second reverse scan, respectively, wherein: at each of the closed sub-regions, the time of the second forward scan and the time of the second reverse scan are proportional to the area of ​​the corresponding closed sub-region; The secondary forward current-voltage curve and the secondary reverse current-voltage curve are fitted to obtain a final current-voltage curve.

2. The method for testing the IV curve of a heterojunction battery according to claim 1, characterized in that: The sum of the time of the initial forward scan and the time of the initial reverse scan is 20ms to 40ms; The sum of the time of the second forward scan and the time of the second reverse scan is 80 ms to 160 ms.

3. The method for testing the IV curve of a heterojunction battery according to claim 2, characterized in that: The first scanning time is divided into a plurality of first sub-scanning times, wherein the first sub-scanning times correspond to the closed sub-regions one by one; the ratio of each of the first sub-scanning times to the first scanning time is equal to the ratio of the area of ​​each of the closed sub-regions to the area of ​​the closed region; The second scanning time is divided into a number of second sub-scanning times, each of the second sub-scanning times corresponds to the closed sub-areas one by one, and the ratio of each of the second sub-scanning times to the second scanning time is equal to the ratio of the area of ​​each of the closed sub-areas to the area of ​​the closed area.

4. The method for testing the IV curve of a heterojunction battery according to any one of claims 1 to 3, characterized in that: The closed sub-areas are evenly spaced on the voltage axis and are distributed from the first area to the Mth area, where M is an integer greater than or equal to 2.

5. The method for testing IV curve of heterojunction battery according to claim 4, characterized in that: M is 700-800.

6. The method for testing IV curve of heterojunction battery according to claim 1, characterized in that: The test conditions for the initial forward scan of the heterojunction cell included: irradiance of 900W / m 2 ~1100W / m 2 ; The test conditions for the initial reverse scan of the heterojunction cell include: irradiance of 900W / m 2 ~1100W / m 2 .

7. The method for testing the IV curve of a heterojunction battery according to any one of claims 1 to 3, characterized in that: The forward scanning range is from 0V to open circuit voltage, and the reverse scanning range is from open circuit voltage to 0V.

8. A heterojunction battery IV curve testing device, used for implementing the heterojunction battery IV curve testing method according to any one of claims 1 to 7, characterized in that: include: A scanning time control unit, the scanning time control unit is used to control a first scanning time when a forward scanning is performed on a heterojunction battery; and, for controlling a second scanning time when performing reverse scanning on the heterojunction battery; A time division unit, the time division unit is used to divide the closed area into a plurality of closed sub-areas; A calculation unit is used to calculate and obtain a forward sweep power curve and a reverse sweep power curve, and to fit the secondary forward current-voltage curve and the secondary reverse current-voltage curve to obtain a final current-voltage curve.

9. The heterojunction battery IV curve testing device according to claim 8, characterized in that: The scanning time control unit comprises: a first scanning time control unit and a second scanning time control unit; The first scanning time control unit is used to control the first scanning time when the heterojunction battery is scanned in the forward direction; The second scanning time control unit is used to control the second scanning time when performing reverse scanning on the heterojunction battery.

10. The heterojunction battery IV curve testing device according to claim 8, characterized in that: The time division unit includes: an input module, and the input module is used to input the number of the closed sub-areas.

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