Real-time diagnosis method for efficient solar cells based on reliable extraction of equivalent circuit parameters

Abstract

The present invention proposes a real-time diagnosis method for high-efficiency solar cells based on reliable extraction of equivalent circuit parameters, which is used to extract parameters of equivalent circuit equations of high-efficiency solar cells and perform performance diagnosis, and includes the following steps: step S1, importing measurement data; step S2, solving by approximation; step S3, parameter space constraints; step S4, nonlinear fitting; step S5, solving parameters using constraints; the present invention shows stability, reliability and universality in parameter extraction of high-efficiency solar cells, and can efficiently perform real-time diagnosis of solar cells.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic power generation, in particular to a high-efficiency solar cell real-time diagnosis method based on reliable extraction of equivalent circuit parameters. Background Art

[0002] Solar cells are expected to achieve low-carbon, environmentally friendly, large-scale clean energy supply. They are the focus of current basic research and industrial research and are widely valued. With the continuous exploration and improvement of solar cells, various high-efficiency solar cells (energy conversion efficiency PCE ≥ 22%, fill factor FF ≥ 80%) are gradually entering the industrial transformation stage. However, researchers still lack simple characterization techniques to conduct rapid and real-time analysis of finished solar cells to reveal the photoelectric processes and material properties of solar cell devices under working conditions. Equivalent circuit parameters (diode saturation current I o , saturation photocurrent I ph , ideal factor n id , series resistance R s And the parallel resistor R sh ) is the most direct way to diagnose solar cells and further infer their physical mechanisms. It is also the basis for analyzing the internal mechanisms of devices and an important criterion for judging technology development. Therefore, the detection method based on equivalent circuit parameters is expected to achieve real-time diagnosis of high-efficiency solar cells during the development and production process.

[0003] Parameter extraction refers to extracting the equivalent circuit parameters of the battery from experimental data. The most direct extraction is to extract the equivalent circuit parameters from the current-voltage (IV) curve of the device. Traditional parameter extraction methods are unstable, inaccurate, and have poor universality. They are not suitable for the high-efficiency solar cells currently being studied and cannot meet the requirements of real-time diagnosis of high-efficiency solar cells. Therefore, it is still necessary to improve the effectiveness of real-time diagnosis technology by improving the performance of parameter extraction methods.

[0004] Existing methods for extracting solar cell equivalent circuit parameters include the following methods:

[0005] (1) Analytical method: The analytical method is based on specific point values ​​(such as open circuit voltage point (V oc ,0), short-circuit current point (0,I sc ) and maximum power point (V mpp , I mpp ) and the corresponding derivatives, the diode model is converted into an algebraic equation of parameters, and the equivalent circuit parameters are obtained by solving the equation.

[0006] (2) Parameter optimization method: This method uses an optimization algorithm to reduce the error between the calculated value and the measured value. By finding the minimum error, the corresponding equivalent circuit parameter value is obtained. The most commonly used optimization algorithms include genetic algorithm, Newton-Raphson iteration method, nonlinear fitting method and particle swarm optimization algorithm.

[0007] However, the IV curve of high-efficiency solar cells presents a steeper rising curve compared to conventional solar cells, and its measurement is easily interfered by measurement factors, such as voltage fluctuations, current-voltage hysteresis effect, capacitance effect, and environmental interference of the measured battery. Due to the characteristics of the IV curve of high-efficiency solar cells mentioned above, the traditional method of extracting equivalent circuit parameters from IV curve data often shows problems such as inaccuracy, non-uniqueness, and initial value dependence, exposing many shortcomings and deficiencies of traditional methods. Specifically:

[0008] When extracting equivalent circuit parameters from steep IV curves of high-efficiency solar cells, the shortcomings of the above two traditional methods are fully exposed, specifically:

[0009] (1) Disadvantages of analytical methods: Because this type of method only relies on a few specific points, it is very sensitive to measurement uncertainty and interference, and has high requirements for specific point values ​​and poor tolerance for measurement errors. Therefore, for analytical methods, smooth experimental curves and accurate special point values ​​are necessary conditions for obtaining correct equivalent circuit parameter results. In addition, in the IV curve of high-efficiency solar cells, most of the steep line segments have large errors, so only a small number of data points can be supported.

[0010] (2) Deficiencies of parameter optimization methods: Due to the large data search space, this method requires a lot of machine time to converge to the target accuracy of the mean square error. During the optimization process, due to the existence of many feasible local minimum points, the algorithm may fall into a local minimum point, where the accuracy of the mean square error does not reach the target accuracy. In addition, the solution at the local minimum point may have non-physical negative values. Therefore, parameter optimization methods are usually inaccurate, non-convergent, and dependent on initial values.

[0011] Experience and extensive research have shown that both the analytical method and the parameter optimization method are not applicable to the IV curves of the high-efficiency solar cells currently being studied. Summary of the invention

[0012] The present invention proposes a high-efficiency solar cell real-time diagnosis method based on reliable extraction of equivalent circuit parameters, which exhibits stability, reliability and universality in parameter extraction of high-efficiency solar cells and can efficiently perform real-time diagnosis on solar cells.

[0013] The present invention adopts the following technical solutions.

[0014] The real-time diagnosis method of a high-efficiency solar cell based on reliable extraction of equivalent circuit parameters is used to extract parameters of an equivalent circuit equation of a high-efficiency solar cell and perform performance diagnosis. The equivalent circuit equation of the high-efficiency solar cell is:

[0015]

[0016] Where I is the real-time output current density of the solar cell, in mA / cm 2 ; V is the real-time output voltage of the solar cell, in V; I ph is the photocurrent density of the solar cell, in mA / cm 2 ;I o is the reverse saturation current density of the diode in the solar cell, in mA / cm 2 ; q is the elementary charge; R s is the equivalent series resistance of the solar cell; R sh is the parallel resistance; n id is the ideal factor; k B is the Boltzmann constant; T is the temperature;

[0017] In the diagnostic method, the method for extracting parameters from the equivalent circuit equation includes the following steps:

[0018] Step S1, importing measurement data consisting of a column of voltage values ​​and a column of current values;

[0019] Step S2: Solve R by approximation sh , that is, the differential value dV / dI of the data point is used to find the insensitive parameter R sh According to formula 4, I ph Approximately I sc Matching the characteristics of high-efficiency solar cells, the expression of dV / dI is:

[0020]

[0021] Assume that the equivalent circuit of a high-efficiency solar cell is in a short-circuit state, and I ph =-I SC and V = 0, that is

[0022] By (0, I sc ) to find R sh The value of

[0023] Step S3: parameter space constraints, specifically:

[0024] Assuming the equivalent circuit of a high-efficiency solar cell is open circuit, I = 0 and V = VOC ,Right now:

[0025]

[0026] By (V OC , 0) around the data points to obtain the value of dV / dI and determine n id With R s to realize the constraints on the values ​​of these two parameters;

[0027] Step S4, nonlinear fitting, specifically: using Lambert W function, convert formula 4 into the following formula

[0028]

[0029] Then, the nonlinear least square method is used to fit the curve and extract parameters. When extracting parameters, the mean square error between the calculated value and the measured value is used as the criterion for judging the accuracy of convergence;

[0030] Step S5, using constraints to solve parameters, specifically using the parameters obtained in step S4 to solve the remaining parameters required for solving the equivalent circuit equation according to constraint formula seven.

[0031] The performance diagnosis method includes performance diagnosis technology under different light intensities. Specifically, after extracting the parameters required by the equivalent circuit equation, the IV curve data of the solar cell under different light intensities are fitted, and the equivalent circuit parameters are extracted. The working performance of the solar cell is diagnosed and studied according to the change trend of the parameters under different light.

[0032] The diagnostic method includes a real-time performance monitoring method, specifically, according to the PCE, FF, n id , R s and I o The specific reasons for performance degradation can be evaluated by combining the changing patterns of the device performance and the performance parameters of the solar cell with the changing patterns of the device performance over time.

[0033] In the real-time performance monitoring method, if the solar cell R s The smaller the transmission layer is, the less likely it is that the solar cell R s If the interface performance of the device changes, the reason for the decrease in performance under long-term illumination is n id Rise and I o If it increases, it is determined that the light absorbing material inside the solar cell device has changed.

[0034] The diagnostic method is used for high efficiency solar cells with energy conversion efficiency greater than 22% and fill factor greater than 80%.

[0035] The energy conversion efficiency of the high-efficiency solar cell is greater than 22%, the filling factor FF is greater than 80%, and R sh The value is greater than 1000Ωcm 2 , R s The value is less than 5Ωcm 2 , its IV curve is a steep linear shape.

[0036] In the diagnostic method, the method for solving the parameters of the equivalent circuit equation is used for perovskite solar cells, perovskite crystalline silicon stacked solar cells, crystalline silicon solar cells or organic solar cells.

[0037] The diagnostic method also includes performance diagnostic technology under different measurement methods, that is, using a parameter extraction method of an equivalent circuit equation to fit IV curve data of high-efficiency solar cells under different measurement methods, and studying the performance of solar cell devices based on the fitting results; the different measurement methods include forward scanning and reverse scanning.

[0038] The technical advantages of the present invention are:

[0039] 1. The solution of the present invention is stable, will not produce non-physical solutions, and is insensitive to initial values.

[0040] 2. The present invention solves (I o , I ph , n id ) or (I o , I ph , R s ) The consistency of the results can introduce new criteria for judging the pros and cons of the optimization methods.

[0041] 3. The present invention can be applied to the parameter extraction of perovskite solar cells, perovskite crystalline silicon stacked solar cells, crystalline silicon solar cells, organic solar cells and the like.

[0042] 4. Suitable for high-efficiency solar cells with energy conversion efficiency higher than 22% and fill factor greater than 80%.

[0043] 5. Real-time monitoring of device working status and performance under different physical environments such as light, temperature, and time is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0045] Attached Figure 1 It is the equivalent circuit diagram of a high-performance solar cell;

[0046] Attached Figure 2 It is a schematic diagram of the process of the present invention;

[0047] Attached Figure 3 is a schematic diagram of the result of a typical IV curve fitting performed in step S4;

[0048] Attached Figure 4 This is a schematic diagram comparing the IV curve fitting results (solid line) and experimental results (circles) in the performance diagnosis technology under different light intensities.

[0049] Attached Figure 5 It is a schematic diagram of parameter extraction results in performance diagnosis technology under different light intensities (used to show the changing trend of parameters under different light intensities);

[0050] Attached Figure 6 It is a schematic diagram of fitting results in the case of forward scanning and reverse scanning in the performance diagnosis technology under different measurement methods;

[0051] Attached Figure 7 It is a typical high-efficiency solar device PCE, FF, n id , R s and I o Schematic diagram of the changing rules and performance parameters of solar cells;

[0052] Attached Figure 8 This is a schematic diagram comparing the IV curves of high-efficiency solar cells and conventional solar cells. DETAILED DESCRIPTION

[0053] As shown in the figure, the real-time diagnosis method of high-efficiency solar cells based on reliable extraction of equivalent circuit parameters is used to extract parameters of the equivalent circuit equation of the high-efficiency solar cell and perform performance diagnosis. The equivalent circuit equation of the high-efficiency solar cell is:

[0054]

[0055] Where I is the real-time output current density of the solar cell, in mA / cm 2 ; V is the real-time output voltage of the solar cell, in V; I ph is the photocurrent density of the solar cell, in mA / cm 2 ;I o is the reverse saturation current density of the diode in the solar cell, in mA / cm 2 ; q is the elementary charge; R s is the equivalent series resistance of the solar cell; R sh is the parallel resistance; n id is the ideal factor; k B is the Boltzmann constant; T is the temperature;

[0056] In the diagnostic method, the method for extracting parameters from the equivalent circuit equation includes the following steps:

[0057] Step S1, importing measurement data consisting of a column of voltage values ​​and a column of current values;

[0058] Step S2: Solve R by approximation sh , that is, the differential value dV / dI of the data point is used to find the insensitive parameter R sh According to formula 4, I ph Approximately I sc Matching the characteristics of high-efficiency solar cells, the expression of dV / dI is:

[0059]

[0060] Assume that the equivalent circuit of a high-efficiency solar cell is in a short-circuit state, and I ph =-I sc and V = 0, that is

[0061] By (0, I sc ) to find R sh The value of

[0062] Step S3: parameter space constraints, specifically:

[0063] Assuming the equivalent circuit of a high-efficiency solar cell is open circuit, I = 0 and V = V Oc ,Right now:

[0064]

[0065] By (V OC , 0) around the data points to obtain the value of dV / dI and determine n id With R s to realize the constraints on the values ​​of these two parameters;

[0066] Step S4, nonlinear fitting, specifically: using Lambert W function, convert formula 4 into the following formula

[0067]

[0068] Then, the nonlinear least square method is used to fit the curve and extract parameters. When extracting parameters, the mean square error between the calculated value and the measured value is used as the criterion for judging the accuracy of convergence;

[0069] Step S5, using constraints to solve parameters, specifically using the parameters obtained in step S4 to solve the remaining parameters required for solving the equivalent circuit equation according to constraint formula seven.

[0070] The performance diagnosis method includes performance diagnosis technology under different light intensities. Specifically, after extracting the parameters required by the equivalent circuit equation, the IV curve data of the solar cell under different light intensities are fitted, and the equivalent circuit parameters are extracted. The working performance of the solar cell is diagnosed and studied according to the change trend of the parameters under different light.

[0071] The diagnostic method includes a real-time performance monitoring method, specifically, according to the PCE, FF, n id , R s and I o The specific reasons for performance degradation can be evaluated by combining the changing patterns of the device performance and the performance parameters of the solar cell with the changing patterns of the device performance over time.

[0072] In the real-time performance monitoring method, if the solar cell R s The smaller the transmission layer is, the less likely it is that the solar cell R s If the interface performance of the device changes, the reason for the decrease in performance under long-term illumination is n id Rise and I o If it increases, it is determined that the light absorbing material inside the solar cell device has changed.

[0073] The diagnostic method is used for high efficiency solar cells with energy conversion efficiency greater than 22% and fill factor greater than 80%.

[0074] The energy conversion efficiency of the high-efficiency solar cell is greater than 22%, the filling factor FF is greater than 80%, and R sh The value is greater than 1000Ωcm 2 , R s The value is less than 5Ωcm 2 , its IV curve is a steep linear shape.

[0075] In the diagnostic method, the method for solving the parameters of the equivalent circuit equation is used for perovskite solar cells, perovskite crystalline silicon stacked solar cells, crystalline silicon solar cells or organic solar cells.

[0076] The diagnostic method also includes performance diagnostic technology under different measurement methods, that is, using a parameter extraction method of an equivalent circuit equation to fit IV curve data of high-efficiency solar cells under different measurement methods, and studying the performance of solar cell devices based on the fitting results; the different measurement methods include forward scanning and reverse scanning.

[0077] Example:

[0078] In this example, when performing performance diagnosis under different light intensities, the parameter extraction method of this scheme is used to fit the IV curve data under different light intensities and extract the equivalent circuit parameters. For example, Figure 4 The comparison between IV curve fitting results (solid line) and experimental results (circles) is given. Figure 5 The parameter extraction results are given, revealing the changing trend of the parameters under different light intensities, which provides more information for the study of the working mechanism of solar cells.

[0079] In this example, when performing performance diagnosis under different measurement methods, the parameter extraction method of this scheme is used to fit the IV curve data under different measurement methods. For example, Figure 6 The fitting results of the forward scan and reverse scan are given, which show that the extracted parameters provide more information, which can be used to study the performance of the device.

[0080] In this example, when used for real-time performance monitoring, the parameter extraction method of this scheme is adopted to fit the IV curve data of different time periods and extract the equivalent circuit parameters. Figure 7 A typical high-efficiency solar device PCE, FF, n id , R s and I o The change law of the device performance over time and the performance parameters of the solar cell. Combined with the change law of the device performance over time, the specific reasons for the performance degradation can be obtained. For example, the reason for the initial performance improvement of the application device in this case is that R s The reason for the decrease in long-term lighting performance is n id Rise and I o This reflects the changes in the device interface and internal material properties. This technology provides more guidance information for improving device performance and stability.

Claims

1. A real-time diagnosis method for high-efficiency solar cells based on reliable extraction of equivalent circuit parameters, which is used to extract parameters of equivalent circuit equations of high-efficiency solar cells and perform performance diagnosis, and is characterized by: The equivalent circuit equation of the high-efficiency solar cell is: Where I is the real-time output current density of the solar cell, in mA / cm 2 ; V is the real-time output voltage of the solar cell, in V; I ph is the photocurrent density of the solar cell, in mA / cm 2 ;I o is the reverse saturation current density of the diode in the solar cell, in mA / cm 2 ; q is the elementary charge; R s is the equivalent series resistance of the solar cell; R sh is the parallel resistance; n id is the ideal factor; k B is the Boltzmann constant; T is the temperature; In the diagnostic method, the method for extracting parameters from the equivalent circuit equation includes the following steps: Step S1, importing measurement data consisting of a column of voltage values ​​and a column of current values; Step S2: Solve R by approximation sh , that is, the differential value dV / dI of the data point is used to find the insensitive parameter R sh According to formula 4, I ph Approximately I sc Matching the characteristics of high-efficiency solar cells, the expression of dV / dI is: Assume that the equivalent circuit of a high-efficiency solar cell is in a short-circuit state, and I ph =-I sc and V = 0, that is By (O, I sc ) to find R sh The value of Step S3: parameter space constraints, specifically: Assuming the equivalent circuit of a high-efficiency solar cell is open circuit, I = 0 and V = V OC ,Right now: By (V OC , 0) around the data points to obtain the value of dV / dI and determine n id With R s to realize the constraints on the values ​​of these two parameters; Step S4, nonlinear fitting, specifically: using Lambert W function, convert formula 4 into the following formula Then, the nonlinear least square method is used to fit the curve and extract parameters. When extracting parameters, the mean square error between the calculated value and the measured value is used as the criterion for judging the accuracy of convergence; Step S5, using the constraints to solve the parameters, specifically using the parameters obtained in step S4 to solve the remaining parameters required for solving the equivalent circuit equation according to constraint formula seven; The diagnostic method includes a performance diagnostic technology under different light intensities, specifically, after extracting the parameters required by the equivalent circuit equation, fitting the IV curve data of the solar cell under different light intensities, and extracting the equivalent circuit parameters, and conducting a diagnostic study on the working performance of the solar cell according to the changing trends of the parameters under different light intensities; The diagnostic method includes a real-time performance monitoring method, specifically, according to the PCE, FF, n id , R s and I o The specific reasons for performance degradation can be evaluated by combining the change law of device performance over time and the performance parameters of solar cells; In the real-time performance monitoring method, if the solar cell R s The smaller the transmission layer is, the less likely it is that the solar cell R s If the interface performance of the device changes, the reason for the decrease in performance under long-term illumination is n id Rise and I o If it increases, it is determined that the light absorption material inside the solar cell device has changed; The diagnostic method is used for high-efficiency solar cells with an energy conversion efficiency greater than 22% and a filling factor greater than 80%. The high-efficiency solar cells have an energy conversion efficiency greater than 22%, a filling factor FF greater than 80%, and R sh The value is greater than 1000Ωcm 2 , R s The value is less than 5Ωcm 2 , its IV curve is a steep linear type; In the diagnostic method, the method for solving the parameters of the equivalent circuit equation is used for perovskite solar cells, perovskite crystalline silicon tandem solar cells, crystalline silicon solar cells or organic solar cells; The diagnostic method does not produce non-physical solutions and is insensitive to initial values. o , I ph , n id ) or (I o , I ph , R s ) results and introduces a basis for judging the pros and cons of the optimization method.

2. The high-efficiency solar cell real-time diagnosis method based on reliable extraction of equivalent circuit parameters according to claim 1 is characterized in that: The diagnostic method also includes performance diagnostic technology under different measurement methods, that is, using a parameter extraction method of an equivalent circuit equation to fit IV curve data of high-efficiency solar cells under different measurement methods, and studying the performance of solar cell devices based on the fitting results; the different measurement methods include forward scanning and reverse scanning.

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