Method for testing quantum efficiency of three-terminal tandem solar cell

Abstract

A method for testing the quantum efficiency of a three-terminal tandem solar cell is disclosed. When measuring the external quantum efficiency (EQE) of the first or second sub-cell, a bias condition is applied between the second and common electrodes, or between the first and common electrodes, of the three-terminal tandem solar cell. This ensures that the second or first sub-cell does not become a current-limiting unit when measuring its spectral response, and suppresses optical and electrical interference that may be introduced by the second or first sub-cell. By applying appropriate bias conditions to the non-test sub-cells and precisely controlling the cell temperature under standard test conditions, this invention can accurately obtain the EQE of each sub-cell separately while effectively avoiding overestimation of the bottom cell's EQE due to light-emitting coupling from the top cell. Furthermore, it is applicable to both series and reverse series structures.

Description

Technical Field

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

[0002] External quantum efficiency (EQE) is a fundamental parameter characterizing the spectral response of each sub-cell in a solar cell. Accurate EQE data for each sub-cell is essential for calculating current matching factors, correcting spectral mismatches, and optimizing cell performance under standard test conditions. However, in a three-terminal tandem solar cell, the two sub-cells are coupled both electrically and optically. For example, the electroluminescence (luminescence coupling) of the top cell under forward bias generates additional photocurrent in the bottom cell. If the operating point of the top cell is not constrained when measuring the EQE of the bottom cell, the EQE of the bottom cell will be significantly overestimated, especially in the short-wavelength region where spurious response tails will appear. Summary of the Invention

[0003] This invention addresses the limitations of existing quantum efficiency measurement techniques for three-terminal tandem solar cells, which are constrained by measurement errors caused by electrical and optical coupling between sub-cells and the inability to simultaneously measure both series and reverse series structures. It proposes a new method for testing the quantum efficiency of three-terminal tandem solar cells. By applying appropriate bias conditions to the non-test sub-cells and precisely controlling the cell temperature under standard testing conditions, the external quantum efficiency of each sub-cell can be accurately obtained separately. This method effectively avoids overestimating the EQE of the bottom cell due to light-emitting coupling from the top cell, and 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 method for testing the quantum efficiency of a three-terminal tandem solar cell. By applying a bias condition between the second electrode and the common electrode or between the first electrode and the common electrode when measuring the external quantum efficiency of the first or second sub-cell of the three-terminal tandem solar cell, the second or first sub-cell does not become a current-limiting unit when measuring the spectral response of the first or second sub-cell, and optical and electrical interference that may be introduced by the second or first sub-cell is suppressed.

[0006] The three-terminal stacked solar cell includes a first sub-cell, a second sub-cell, a first electrode, a second electrode, and a common electrode, wherein the first sub-cell is located between the first electrode and the common electrode, and the second sub-cell is located between the second electrode and the common electrode.

[0007] The first sub-cell is the top cell of the three-terminal stacked battery, and the second sub-cell is the bottom cell of the three-terminal stacked battery.

[0008] The bias conditions include: when measuring the external quantum efficiency of the first sub-cell, short-circuiting the second electrode and the common electrode, or applying a load resistance equal to the equivalent resistance value of the maximum power point of the second sub-cell between the second electrode and the common electrode; or when measuring the external quantum efficiency of the second sub-cell, short-circuiting the first electrode and the common electrode, or applying a load resistance equal to the equivalent resistance value of the maximum power point of the first sub-cell between the first electrode and the common electrode.

[0009] The maximum power point equivalent resistance value is obtained by: simultaneously applying a first voltage between the first electrode and the common electrode and measuring the first current; applying a second voltage between the second electrode and the common electrode and measuring the second current; multiplying the first voltage and the first current to obtain the first output power, i.e., the output power of the first battery; multiplying the second voltage and the second current to obtain the second output power, i.e., the output power of the second battery; continuously applying different values ​​of the first voltage and the second voltage, when the sum of the two output powers reaches its maximum value, both sub-batteries are in the maximum power operating state. At this time, the maximum power point equivalent resistance value of the first battery is calculated based on the first voltage and the first current, and the maximum power point equivalent resistance value of the second battery can be calculated based on the second voltage and the second current.

[0010] The external quantum efficiency is calculated by illuminating the test cell with monochromatic light wavelength by wavelength after applying a bias condition and measuring the short-circuit current through the test cell at each wavelength. After calibration with a standard detector, the external quantum efficiency is obtained.

[0011] The monochromatic light wavelength-by-wavelength irradiation is preferably performed by simultaneously irradiating the entire three-terminal stacked cell with bias white light or bias light of a specific wavelength that is asynchronously modulated with the monochromatic light during spectral scanning. This allows the sub-cell under test to be at a carrier generation level close to that under standard illumination. At the same time, a lock-in amplifier is used to extract the small AC signal generated by the monochromatic light to obtain EQE data with a high signal-to-noise ratio.

[0012] The specific wavelength of the bias light is 200-1200nm.

[0013] The aforementioned test method maintains a constant temperature of 25±1℃ for the three-terminal tandem solar cell throughout the entire measurement process to meet the requirements of standard test conditions and avoid measurement errors caused by temperature drift.

[0014] Technical effect

[0015] When measuring the external quantum efficiency of the first or second sub-cell of a three-terminal tandem solar cell, the present invention applies a bias condition between the second electrode and the common electrode or between the first electrode and the common electrode of the three-terminal tandem solar cell. Attached Figure Description

[0016] Figure 1 This is a connection diagram for measuring the EQE of the first sub-cell of a three-terminal stacked solar cell according to the present invention;

[0017] Figure 2 This is a connection diagram for measuring the EQE of the second sub-cell of a three-terminal stacked solar cell according to the present invention;

[0018] Figure 3 This is a schematic diagram illustrating the effect of the example;

[0019] In the figure: 1 Light source device, 2 Temperature control sample stage, 3 Sample to be tested, 31 First sub-cell, 32 Second sub-cell, 33 First electrode, 34 Second electrode, 35 Common electrode, 4 Bias device, 5 Current measuring device, 6 Processor. Detailed Implementation

[0020] like Figure 1 As shown, this embodiment relates to a method for testing the quantum efficiency of a three-terminal tandem solar cell. The area of ​​the cell under test is 4 cm². The three-terminal tandem solar cell includes a nip perovskite top cell as a first sub-cell 31 and an n-type HBC bottom cell as a second sub-cell 32. The front surface of the top cell is the first electrode 33, the p-type region on the back surface of the bottom cell is the second electrode 34, and the n-type region on the back surface of the bottom cell is the common electrode 35.

[0021] The testing method includes:

[0022] Step 1: Fix the battery on the temperature-controlled sample stage 2 at 25°C.

[0023] Step 2: Measure the EQE of the first sub-cell 31: Connect the input terminal of the current testing device to the first electrode 33 and the common electrode 35. Connect a copper wire directly between the second electrode 34 and the common electrode 35 to simulate the short-circuit state of the bottom cell. Turn on the bias white light source and scan the 300-800nm ​​wavelength band using monochromatic light modulated by a chopper. The lock-in amplifier reads the short-circuit AC current signal, and after calibration, the processor calculates the EQE curve of the top cell.

[0024] Step 3: Measure the EQE of the second sub-cell 32: Connect the input terminal of the current testing device to the second electrode 34 and the common electrode 35. Connect a 10Ω load resistor (±0.1% precision wire-wound resistor) between the first electrode 33 and the common electrode 35. This resistor value is close to the equivalent resistance of the top cell's maximum power point determined by the IV test previously, so that the top cell operates near its maximum power point, thereby controlling its luminescent coupling current at a reasonable level. Scan the 800–1200nm band with biased white light superimposed with modulated monochromatic light, and use a lock-in amplifier to detect the short-circuit current to obtain the bottom cell EQE curve.

[0025] Using the obtained EQE data of the two sub-cells, the photocurrent of each sub-cell under the standard AM1.5G spectrum can be calculated, and the light source can be adjusted by combining the spectral mismatch factor to achieve standardized performance testing of three-terminal stacked cells.

[0026] Through practical application experiments, in an environment including a Keithley 2400 source meter, an SR830 lock-in amplifier, and self-developed LabVIEW measurement and control software, the quantum efficiency testing method of the three-terminal tandem solar cell of this invention was tested by controlling the battery temperature at 25°C, connecting a 10Ω load resistor matching the equivalent resistance of the maximum power point between the non-tested sub-electrodes, and performing biased white light superposition modulation monochromatic light scanning in 10nm steps in the 200-1200nm wavelength range. The experimental data obtained are as follows: Figure 3 As shown. Compared with existing measurement methods, the method in this paper eliminates the false EQE tail (red dashed line) that appears in the 200-600nm band of silicon-based solar cells.

[0027] Compared with the prior art, the present invention introduces a load resistor during the measurement process, so that the top cell is in the maximum power point state. The measured EQE data of the silicon bottom cell is the true EQE under normal battery operation, which fundamentally eliminates the light-emitting coupling between the two sub-cells introduced by the existing EQE measurement method.

[0028] 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 method for testing quantum efficiency of a three-terminal tandem solar cell, characterized by, By applying a bias condition between the second electrode and the common electrode or between the first electrode and the common electrode when measuring the external quantum efficiency of the first or second sub-cell of a three-terminal tandem solar cell, the second or first sub-cell does not become a current-limiting unit when measuring the spectral response of the first or second sub-cell, and optical and electrical interference that may be introduced by the second or first sub-cell is suppressed.

2. The method of claim 1, wherein the three-terminal tandem solar cell is a solar cell of the type shown in FIG.

1. The three-terminal stacked solar cell includes a first sub-cell, a second sub-cell, a first electrode, a second electrode, and a common electrode, wherein the first sub-cell is located between the first electrode and the common electrode, and the second sub-cell is located between the second electrode and the common electrode.

3. The method of claim 1 or 2, wherein the three-terminal tandem solar cell is a solar cell of the type shown in FIG.

1. The bias conditions include: when measuring the external quantum efficiency of the first sub-cell, short-circuiting the second electrode and the common electrode or applying a load resistance between the second electrode and the common electrode that matches the equivalent resistance of the maximum power point of the second sub-cell; or when measuring the external quantum efficiency of the second sub-cell, short-circuiting the first electrode and the common electrode or applying a load resistance between the first electrode and the common electrode that matches the equivalent resistance of the maximum power point of the first sub-cell.

4. The method of claim 3, wherein the three-terminal tandem solar cell is a solar cell according to any one of claims 1 to 2. The external quantum efficiency is calculated by illuminating the test cell with monochromatic light wavelength by wavelength after applying a bias condition and measuring the short-circuit current through the test cell at each wavelength. After calibration with a standard detector, the external quantum efficiency is obtained.

5. The method of claim 3, wherein the three-terminal tandem solar cell is a GaAs / Ge tandem solar cell. The monochromatic light is irradiated wavelength by wavelength. During spectral scanning, the entire three-terminal stacked cell is simultaneously irradiated with bias white light or bias light of a specific wavelength that is asynchronously modulated with the monochromatic light. This makes the sub-cell under test at a carrier generation level close to that under standard illumination. At the same time, a lock-in amplifier is used to extract the small AC signal generated by the monochromatic light to obtain EQE data with a high signal-to-noise ratio.

6. The method of claim 5, wherein the three-terminal tandem solar cell is a GaAs / Ge tandem solar cell. The specific wavelength mentioned is the 200-1200nm band.

7. The method of testing quantum efficiency of a three-terminal tandem solar cell according to any one of claims 1 to 6, wherein the method is characterized by, Throughout the entire measurement process, the temperature of the three-terminal tandem solar cell was kept constant at 25±1℃ to meet the requirements of standard test conditions and avoid measurement errors caused by temperature drift.

8. The method for testing the quantum efficiency of a three-terminal tandem solar cell according to any one of claims 1-6, characterized in that, The maximum power point equivalent resistance is obtained as follows: simultaneously applying a first voltage between the first electrode and the common electrode and measuring the first current; applying a second voltage between the second electrode and the common electrode and measuring the second current; multiplying the first voltage and the first current to obtain the first output power, i.e., the output power of the first battery; multiplying the second voltage and the second current to obtain the second output power, i.e., the output power of the second battery; continuously applying different values ​​of the first voltage and the second voltage, when the sum of the two output powers reaches its maximum value, both sub-batteries are in the maximum power operating state. At this time, the maximum power point equivalent resistance value of the first battery is calculated based on the first voltage and the first current, and the maximum power point equivalent resistance value of the second battery can be calculated based on the second voltage and the second current.

9. The method for testing the quantum efficiency of a three-terminal tandem solar cell according to claim 3, characterized in that, The load resistor is a precision wire-wound resistor with a resistance of 10Ω and an error of ±0.1%.

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