Method for testing a three-terminal tandem solar cell

Abstract

The application discloses a testing method for a three-terminal tandem solar cell. The method comprises the following steps: setting a source measurement unit (SMU) between a common electrode and a bottom electrode of a three-terminal tandem solar cell to be tested, setting another SMU between a top electrode and the common electrode, and simultaneously applying a voltage to detect a steady-state current passing through the two SMUs; obtaining an electrical performance parameter and a maximum power point (MPP); further narrowing a voltage setting range and repeating the test to obtain an accurate value of the MPP. The application can be simultaneously applied to a series structure and a reverse series structure.

Description

Technical Field

[0001] This invention relates to a technology in the field of solar cells, specifically a testing method for a three-terminal stacked solar cell. Background Technology

[0002] Tandem solar cells represent the most promising route to breaking the theoretical efficiency limit of single-junction solar cells. Three-terminal tandem solar cells utilize back-contact solar cells on the bottom cell. Current testing methods for three-terminal tandem cells require both sub-cells to operate simultaneously; the sum of their output power is the accurate output power of the three-terminal tandem cell. Furthermore, since the two sub-cells require different voltages, accurately determining the maximum power operating point (MPP) necessitates setting numerous test voltage points within two voltage ranges, resulting in an excessive number of data points and prolonged testing time. Another issue is that, depending on whether the diodes in the two sub-cells are aligned in the same or opposite directions, three-terminal tandem solar cells are classified into series and anti-series structures. Current testing methods are only applicable to one structure and cannot be universally applied to different three-terminal tandem cell structures. Summary of the Invention

[0003] This invention addresses the problems of existing measurement techniques that require separate measurements of individual cells during operation, resulting in discrepancies with actual electrical performance, slow detection speed, and insufficient accuracy. It proposes a three-terminal tandem solar cell testing method that is applicable to both series and reverse series structures.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a testing method for a three-terminal tandem solar cell, comprising:

[0006] Step 1: Set up a source measurement unit (SMU) between the common electrode and the bottom electrode, and between the top electrode and the common electrode, respectively, of the three-terminal tandem solar cell under test.

[0007] The source measurement unit includes a voltage source and a current measurement unit, wherein the voltage source is positioned between the input and output terminals of the source measurement unit to apply a given voltage value, and the current measurement unit measures the current value passing through the input and output terminals of the source measurement unit.

[0008] Step 2: Under a standard spectrum (AM1.5G) on the Earth's surface, a first source measurement unit is set up to apply a first voltage within a first voltage range to the bottom electrode and the common electrode in a preset step size, and the first steady-state current is measured; at the same time, a second source measurement unit is set up to apply a second voltage within a second voltage range to the top electrode and the common electrode in a preset step size, and the second steady-state current is measured, thereby obtaining the electrical performance parameters of the three-terminal tandem solar cell under test.

[0009] The first and second voltage ranges are obtained in the following way:

[0010] a) For a series structure, the first voltage range is from 0V to the open-circuit voltage of the bottom cell, and the second voltage range is from 0V to the sum of the open-circuit voltages of the top and bottom cells.

[0011] b) For the reverse series structure, the first voltage range is 0V to the open circuit voltage of the bottom cell, and the second voltage range is 0V to the open circuit voltage of the top cell.

[0012] The preset step size refers to a preset voltage value, which is applied gradually at voltage intervals within the voltage range.

[0013] The term "gradual application" refers to applying voltage values ​​within the voltage range in ascending or descending order. After each voltage value is applied and the corresponding steady-state current is measured, a preset step size is increased or decreased before applying the next voltage, until the voltage range is exceeded.

[0014] The preset step sizes for the first and second voltage ranges can be the same or different. Based on the set first and second voltage ranges, a suitable step size can be selected to balance test accuracy and total test time. When applying the first and second voltage ranges, the voltage can be applied in an ascending or descending direction according to the set step size.

[0015] The total number of steps is the product of the number of steps within the first voltage range and the second voltage range. For example, in a preferred embodiment, the bottom cell of a reverse-series three-terminal tandem solar cell is a heterojunction back-contact (HBC) solar cell with an open-circuit voltage of less than 0.8V, therefore the first voltage range is set to 0-0.8V. To reduce the total number of test steps and control the initial test time, ensuring that the number of steps within the first voltage range is less than 100, a preset step size of approximately 20mV is set, resulting in 41 applied first voltage values. The top cell is a perovskite solar cell with an open-circuit voltage of less than 1.5V, therefore the second voltage range is 0-1.5V, with a preset step size of 20mV, resulting in 76 applied second voltage values. In the actual test, voltages were applied in ascending order: first, a first voltage of 0V was applied, followed by second voltages of 0, 0.02, 0.04, 0.06, ..., 1.5V; then, a first voltage of 0.02V was applied, followed by second voltages of 0, 0.02, 0.04, 0.06, ..., 1.5V; and so on. Therefore, a total of 41 × 76 = 3116 voltage combinations were measured in the preliminary test.

[0016] The simultaneous setting refers to applying the first voltage and the second voltage simultaneously so that both the bottom cell and the top cell of the three-terminal tandem solar cell under test are in working condition.

[0017] The electrical performance parameters include:

[0018] a) For a series structure, the control source measurement unit first applies voltage and then measures current, and determines during the test:

[0019] i) For a certain voltage combination, when the measured first steady-state current and second steady-state current are both zero, the battery as a whole is in an open circuit state. At this time, the applied first voltage is the open circuit voltage of the bottom battery, and the applied second voltage is the sum of the open circuit voltages of the bottom battery and the top battery.

[0020] ii) When both the first and second applied voltages are zero, the battery as a whole is in a short-circuit state. At this time, the first steady-state current is the difference between the short-circuit currents of the bottom battery and the top battery, and the second steady-state current is the minimum value of the short-circuit currents of the bottom battery and the top battery. The relationship between the magnitudes of the short-circuit currents of the top battery and the bottom battery can be determined based on the direction of the first steady-state current.

[0021] iii) Based on the applied voltage and measured steady-state current at any step, the sum of the output power measured by the two source measurement units is the output power of the three-terminal tandem battery. The maximum power operating point (MPP) is obtained when the output power of the three-terminal tandem battery is at its maximum.

[0022] b) For the reverse series structure, the control source measurement unit applies voltage first and then measures current, and determines during the test:

[0023] i) When the measured first steady-state current and second steady-state current are both zero under a certain voltage combination, the battery as a whole is in an open circuit state. At this time, the applied first voltage is the open circuit voltage of the bottom battery, and the applied second voltage is the open circuit voltage of the top battery.

[0024] ii) When both the first and second applied voltages are zero, the battery as a whole is in a short-circuit state. The first steady-state current measured at this time is the short-circuit current of the bottom battery, and the second steady-state current measured at this time is the short-circuit current of the top battery.

[0025] iii) Based on the applied voltage and measured steady-state current at any step, the output power measured by the first source measurement unit is the output power of the bottom cell, and the output power measured by the first source measurement unit is the output power of the top cell. The sum of the two output powers is the output power of the three-terminal stacked cell. The maximum power operating point is obtained when the output power of the three-terminal stacked cell is at its maximum.

[0026] Step 3: Set the third and fourth voltage ranges of the first and second source measurement units according to the maximum power operating point (MPP), and repeat step 2 to obtain the accurate value of the maximum power operating point.

[0027] The maximum power operating point refers to the first voltage, second voltage, first steady-state current, and second steady-state current corresponding to the maximum output power of the three-terminal tandem solar cell during the test in step two.

[0028] The third voltage range should be smaller than the first voltage range, the fourth voltage range should be smaller than the second voltage range, and the step size of the third and fourth voltage ranges should be smaller than the step size of the first and second voltage ranges.

[0029] For example, for a three-terminal tandem solar cell with a reverse series structure, the first and second voltage ranges applied are 0-0.75V and 0-1.4V, respectively, with a step size of 10mV. The determined first and second voltages for the MPP are 0.67V and 1.12V, respectively. Therefore, in repeated measurements, the applied third and fourth voltage ranges are set to 0.62V-0.72V and 1.07V-1.17V, respectively, with a step size of 1mV.

[0030] This method can quickly determine the approximate location of the MPP in the initial test, and obtain the accurate voltage value of the MPP through repeated measurements with smaller steps.

[0031] Technical effect

[0032] This invention involves a two-stage test with both sub-cells operating simultaneously, and is applicable to both series and reverse series structures of three-terminal tandem solar cells. Compared to existing technologies, the test results of this invention are more reasonable, and the accuracy and measurement time are significantly improved. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the invention;

[0034] Figure 2 This is a test circuit diagram for a three-terminal stacked solar cell with a series structure.

[0035] Figure 3 Test circuit diagram for a three-terminal stacked solar cell with reverse series structure;

[0036] Figure 4 This is a flowchart of the testing process for this invention;

[0037] In the diagram: 1 top battery, 2 bottom battery, 3 top electrode, 4 common electrode, 5 bottom electrode, 6 first source measurement unit, 7 second source measurement unit. Detailed Implementation

[0038] Example 1

[0039] like Figure 1As shown, this embodiment illustrates a test method for a three-terminal tandem solar cell with a perovskite / silicon heterojunction back-contact (HBC) back-contact structure, with an area of ​​16.0 cm². 2 The testing steps include:

[0040] S1: The first source measurement unit is connected to the bottom electrode, and the second source measurement unit is connected to the top electrode; both are connected to a common electrode. The circuit structure after connection is shown below. Figure 2 .

[0041] S2: The bottom cell of this three-terminal tandem solar cell is an HBC cell with an open-circuit voltage not exceeding 0.8V; the top cell is a wide-bandgap perovskite solar cell with an open-circuit voltage not exceeding 1.5V. The sum of the open-circuit voltages of the top and bottom cells does not exceed 2.3V. Therefore, the first voltage range is set to 0-0.8V with a step size of 20mV; the second voltage range is set to 0-2.3V with a step size of 20mV.

[0042] S3: Apply the first voltage range and the second voltage range sequentially from small to large, while simultaneously measuring the first steady-state current and the second steady-state current. During this process, the open-circuit voltage of the bottom battery was measured to be 0.62V, and the short-circuit current was measured to be 18.47mA / cm. 2 The open-circuit voltage of the top battery is 1.14V, and the short-circuit current is 21.22mA / cm. 2 .

[0043] S4: The first output power is given by the product of the first voltage and the first steady-state current, and the second output power is given by the product of the second voltage and the second steady-state current. The total output power of the three-terminal tandem solar cell is the sum of the first output power and the second output power.

[0044] S5: Based on the output power measured under all combinations of the first and second voltages, the maximum output power is found to be 0.416W, and the corresponding maximum power operating point is 0.54V at the first voltage and 2.69mA / cm² at the first steady-state current. 2 The second voltage is 1.42V, and the second steady-state current is 17.28mA / cm. 2 .

[0045] S6: Based on the first and second maximum power operating voltages corresponding to the maximum power operating point, set the third voltage range to 0.54V±0.05V and the fourth voltage range to 1.42±0.05V, with a step size of 1mV for each.

[0046] S7: Apply the third voltage range and the fourth voltage range in ascending order, while simultaneously measuring the first steady-state current and the second steady-state current.

[0047] S8: Repeating the algorithm in S4, a more accurate maximum output power of 0.418W is obtained, along with the corresponding maximum power operating point precision values ​​of 0.548V (first voltage) and 2.70mA / cm² (first steady-state current). 2 The second voltage is 1.423V, and the second steady-state current is 17.32mA / cm. 2 .

[0048] Example 2

[0049] like Figure 3 As shown, this embodiment relates to a testing method for a perovskite / HBC reverse series three-terminal tandem solar cell. The difference from Embodiment 1 is that, for the reverse series structure, the names of the bottom electrode and the common electrode are interchanged, and in step S2, the first voltage range is set to 0-0.8V with a step size of 20mV; the second voltage range is set to 0-1.5V with a step size of 20mV. The circuit connection method is as follows... Figure 3 As shown.

[0050] Subsequent testing procedures were consistent; after determining the maximum power operating point in the same way, the tests were repeated to obtain a more accurate maximum output power. The open-circuit voltage of the bottom battery was 0.64V, and the short-circuit current was 18.12mA / cm². 2 The open-circuit voltage of the top battery is 1.14V, and the short-circuit current is 21.65mA / cm. 2 The maximum output power is 0.411W, corresponding to a maximum power operating point of 0.552V at the first voltage and a first steady-state current of 16.44mA / cm. 2 The second voltage is 0.916V, and the second steady-state current is 18.25mA / cm. 2 .

[0051] Compared with the prior art, the present invention measures the electrical performance parameters of two sub-batteries working simultaneously more quickly and accurately; S8 measures the precise value of the maximum power operating point with higher precision; in Embodiment 2, only the two electrodes of the sub-batteries need to be interchanged in the connection circuit to achieve universality for different battery structures.

[0052] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A testing method for a three-terminal tandem solar cell, characterized in that, The maximum power point (MPP) is obtained by setting a source measurement unit (SMU) between the common electrode and the bottom electrode and between the top electrode and the common electrode of the three-terminal stacked solar cell to be tested respectively, and detecting the steady-state current passing through after applying voltage, and then further narrowing the voltage setting range and repeating the test to obtain accurate electrical performance parameters, specifically including: Step one, setting a source measurement unit between the common electrode and the bottom electrode and between the top electrode and the common electrode of the three-terminal stacked solar cell to be tested respectively; Step two, under a standard spectrum on the earth's surface, setting the first source measurement unit to gradually apply a first voltage in a first voltage range on the bottom electrode and the common electrode with a preset step size, and measuring a first steady-state current; at the same time, setting the second source measurement unit to apply a second voltage in a second voltage range on the top electrode and the common electrode with a preset step size, and measuring a second steady-state current, thereby obtaining the electrical performance parameters of the three-terminal stacked solar cell to be tested; Step three, setting the third voltage range and the fourth voltage range of the first and second source measurement units according to the maximum power point, and repeating step two to obtain the accurate value of the maximum power point.

2. The testing method for three-terminal stacked solar cells according to claim 1, characterized in that, The first and second voltage ranges are obtained by the following methods: a) for a series structure, the first voltage range is 0V to the open circuit voltage of the bottom cell, and the second voltage range is 0V to the sum of the open circuit voltages of the top cell and the bottom cell; b) for a reverse series structure, the first voltage range is 0V to the open circuit voltage of the bottom cell, and the second voltage range is 0V to the open circuit voltage of the top cell.

3. The method of claim 1, wherein the method further comprises: applying a voltage to the first electrode of the test cell; and measuring a current through the test cell. The preset step size refers to a preset voltage value, which is used as the voltage interval when gradually applying the voltages in the voltage range; The gradual application refers to applying the voltage values in the voltage range in order from small to large or from large to small, and after applying each voltage value and measuring the corresponding steady-state current, increasing or decreasing a preset step size, and then applying the next voltage, until the voltage range is exceeded.

4. The method of claim 1, wherein the three-terminal stacked solar cell is a tandem solar cell. The simultaneous setting refers to the simultaneous application of the first voltage and the second voltage to make the bottom cell and the top cell of the three-terminal stacked solar cell to be tested both in working condition.

5. The method of claim 1, wherein the method further comprises: applying a voltage to the first electrode of the three-terminal stacked solar cell; and measuring a current through the second electrode of the three-terminal stacked solar cell. The electrical performance parameters include: a) for a series structure, the control source measurement unit applies voltage first and then measures current, and in the test process, it is determined that: i) for a certain voltage combination, when the measured first steady-state current and second steady-state current are both zero, the overall cell is in an open circuit state, at this time the applied first voltage is the open circuit voltage of the bottom cell, and the applied second voltage is the sum of the open circuit voltages of the bottom cell and the top cell; ii) when the applied first voltage and second voltage are both zero, the overall cell is in a short circuit state, at this time the measured first steady-state current is the difference between the short circuit currents of the bottom cell and the top cell, and the measured second steady-state current is the minimum value of the short circuit currents of the bottom cell and the top cell, and the size relationship of the short circuit currents of the top cell and the bottom cell is determined according to the direction of the first steady-state current. iii) according to the applied voltage and the measured steady-state current of any step, the sum of the output power measured by the two source measurement units is the output power of the three-terminal tandem cell, and the maximum output power of the three-terminal tandem cell is obtained at the maximum power point (MPP) b) for the reverse series structure, the source measurement unit is controlled to apply voltage and measure current, and during the test, it is determined that: i) for a certain voltage combination, when the measured first steady-state current and second steady-state current are both zero, the whole battery is in an open circuit state, at this time, the applied first voltage is the open circuit voltage of the bottom cell, and the applied second voltage is the open circuit voltage of the top cell; ii) when the applied first voltage and second voltage are both zero, the whole battery is in a short circuit state, at this time, the measured first steady-state current is the short circuit current of the bottom cell, and the measured second steady-state current is the short circuit current of the top cell; iii) according to the applied voltage and the measured steady-state current of any step, the output power measured by the first source measurement unit is the output power of the bottom cell, the output power measured by the first source measurement unit is the output power of the top cell, the sum of the two output powers is the output power of the three-terminal tandem cell, and the maximum output power of the three-terminal tandem cell is obtained at the maximum power point.

6. The method of claim 5, wherein the method further comprises: applying a voltage to the first electrode of the test cell; and applying a voltage to the second electrode of the test cell. The maximum power point refers to: in step two, when the output power of the three-terminal tandem solar cell is maximum, the corresponding first voltage, second voltage, first steady-state current and second steady-state current are obtained.

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