Calculation method and application of photo-generated minority carrier distribution

Abstract

The invention provides a calculation method and application of photo-generated minority carrier distribution. The calculation method comprises the following steps of (1) calculating the generation rate of photo-generated electron-hole pairs, (2) diffusing and compounding carriers, and (3) establishing a mathematical model and solving. The calculation method aims at improving the photoelectric conversion efficiency of the photoelectric material. The optimal thickness of the photoelectric film is calculated and determined by adopting the model for different types of photoelectric film materials and comprehensively considering the light absorption characteristic, the minority carrier generation and recombination mechanism and the distribution rule of the minority carriers in the materials, so that the optimization of the material performance is realized.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic materials, and in particular to a calculation method and application of photogenerated minority carrier distribution. Background Art

[0002] Photoelectrochemical (PEC) technology, as a method for directly converting solar energy into chemical energy, shows great potential in addressing the global energy crisis and environmental issues. The core component of a PEC system is the photoelectrode, whose performance directly affects energy conversion efficiency. The performance of a photoelectrode is influenced by multiple factors, among which the generation rate and collection efficiency of photogenerated minority carriers are key parameters. Photogenerated carriers, including electrons and holes, are generated in semiconductor materials under light excitation, and their efficient separation and transport are crucial for the PEC reaction.

[0003] In traditional PEC photoelectrode designs, improving the generation rate of photogenerated carriers typically relies on increasing the thickness of the photovoltaic film to capture more photons. However, this strategy has an inherent contradiction: while thick films can improve light absorption, they also limit the diffusion length of minority carriers to reach the electrode surface, as minority carriers may recombine before reaching the surface. This contradiction leads to a performance optimization problem, namely how to determine the optimal thickness of the film to achieve the highest photoelectrochemical activity under specific lighting conditions.

[0004] To address this issue, researchers typically use a trial-and-error approach, experimentally adjusting film thickness, testing its photoelectrochemical performance, and then optimizing based on the results. This approach is not only time-consuming and labor-intensive, but also expensive. Furthermore, it often only yields optimized solutions for specific materials and conditions, making it difficult to generalize to other materials or conditions. Summary of the Invention

[0005] This paper proposes a method for optimizing the optimal thickness of photovoltaic thin films based on a calculation model for the distribution of photogenerated minority carriers, aiming to improve the photoelectric conversion efficiency of photovoltaic materials. This model calculates and determines the optimal thickness of photovoltaic thin films for different types of photovoltaic thin film materials by comprehensively considering the light absorption characteristics, minority carrier generation and recombination mechanisms, and the distribution patterns of minority carriers within the material, thereby optimizing material performance.

[0006] The present invention provides a method for calculating the distribution of photogenerated minority carriers, the method comprising the following steps:

[0007] 1) Calculate the generation rate of photogenerated electron-hole pairs:

[0008] Obtaining the basic optical parameters of the thin film material, calculating the band gap energy of the thin film material through first-principles calculations, and then combining the reflection and transmission spectra of the thin film material to obtain the absorption coefficient α; based on the absorption coefficient α of the thin film material, calculating the absorption depth of the incident photon in the thin film, and finally calculating the generation rate G of photogenerated electron-hole pairs using formula I;

[0009] G=αφ0e -αx Formula I;

[0010] Where φ0 is the luminous flux per unit area, that is, the number of photons incident on the surface of the material; χ is the thickness of the thin film material.

[0011] The basic optical parameters of the thin film material include absorption coefficient and band gap energy. These parameters can be measured experimentally or found in the literature. The calculation of the absorption depth of the incident photon in the thin film: the absorption depth of the incident photon in the thin film is calculated based on the absorption coefficient of the material. The absorption depth is different for light of different wavelengths, so it is necessary to calculate the photon absorption within the entire solar spectrum. The generation of photogenerated minority carriers: the generation rate of photogenerated electron-hole pairs is calculated using the absorption depth data combined with the photon energy. This calculation takes into account the intensity of the incident light, the spectral distribution and the thickness of the film.

[0012] 2) Carrier Diffusion and Recombination. The diffusion process of carriers in thin films is described by the diffusion equation. For nanoscale photovoltaic films, surface recombination and interface effects significantly influence carrier behavior. This paper incorporates parameters for surface and interface recombination velocities into the diffusion model, enabling accurate simulation of carrier losses in films of varying thicknesses.

[0013] 3) Establish a mathematical model and solve it:

[0014] 3.1) The model equation is:

[0015] Where n is the minority carrier concentration, D is the minority carrier diffusion coefficient, μ is the minority carrier mobility, E is the electric field strength, τ is the minority carrier lifetime, and L is the minority carrier diffusion length;

[0016] 3.2) Determine boundary conditions

[0017] At the semiconductor / electrolyte interface, the boundary condition for x=0 is given by Formula III; at the semiconductor / substrate interface, the boundary condition for x=d is given by Formula IV;

[0018]

[0019] Where S is the surface recombination velocity, Si is the interface recombination velocity, and E0 is the surface electric field intensity;

[0020] 3.3) Use the finite difference method to discretize the continuous model equation to obtain the discretized equation:

[0021]

[0022] in, h is the spatial step length;

[0023] 3.4) Convert the discretized equation into a matrix form An = g, where A is a (d + 2)-dimensional square matrix, and n and g are (d + 2)-dimensional column vectors;

[0024] 3.5) Calculate the electric field distribution:

[0025] The relationship between electric field intensity E and electric potential φ is:

[0026] The electric potential distribution is obtained by solving the Poisson equation, and then the electric field distribution is calculated;

[0027] 3.6) Use linear algebra methods to solve the matrix equation An = g and obtain the photogenerated minority carrier distribution n(x).

[0028] Furthermore, in the calculation method of the photogenerated minority carrier distribution of the present invention, the model equation is obtained by simplifying the continuity equation of the minority carriers under steady-state conditions;

[0029] The continuity equation is:

[0030] Wherein, t is time; the steady-state condition is:

[0031] Furthermore, in the calculation method of the photogenerated minority carrier distribution described in the present invention, in step 3.2), S and Si in the boundary conditions are idealized to 0 and ∞, respectively; where 0 indicates that all minority carriers moving to the surface participate in the reaction, and ∞ indicates that all minority carriers moving to the interface undergo recombination losses.

[0032] Furthermore, in the calculation method of the photogenerated minority carrier distribution of the present invention, the calculation method solves two photogenerated minority carrier distributions n(x) under different film thicknesses for two cases where the light source is incident from the front and back.

[0033] Furthermore, in the calculation method of the light-generated minority carrier distribution of the present invention, the minority carrier concentration n and the flat band potential V of the thin film material are measured by the Mott-Schottky method.fb and slope s;

[0034] By formula Calculate n, where ε0 is the dielectric constant of vacuum, C sc Refers to the capacitance formed at the semiconductor-electrolyte interface;

[0035] Calculate the minority carrier mobility μ according to the formula σ=neμ, where σ is the conductivity;

[0036] Through the formula μ=eτ h m * Calculate the mean free time τ of majority carriers h , where m * is the effective mass of minority carriers; set the mean free time τ of minority carriers e Equal to the mean free time τ of majority carriers h , then by the formula Calculate the diffusion coefficient D of minority carriers and further obtain the diffusion length of minority carriers where k B is the Boltzmann constant, and T is the absolute temperature.

[0037] On the other hand, the present invention further provides a use of the method for calculating the distribution of photogenerated minority carriers based on any one of the above items, wherein the method for calculating the distribution of photogenerated minority carriers is used to determine the optimal thickness of a photovoltaic thin film.

[0038] Furthermore, in the use of the present invention, the photoelectric film includes an oxide semiconductor film.

[0039] Furthermore, in the use of the present invention, the oxide semiconductor film is a CuBi2O4 film, a BiFeO3 film, or a CuFeO2 film.

[0040] Furthermore, in the use of the present invention, the optimal thickness of the CuFeO3 thin film material is 300nm, the optimal thickness of the CuBi2O4 thin film is 100nm, and the optimal thickness of the Fe2O3 thin film is 50nm.

[0041] Furthermore, in the use of the present invention, the error range of the optimal thickness of the photoelectric thin film determined by the calculation method of the photogenerated minority carrier distribution is ±10 nm.

[0042] Taking into account multiple factors such as light absorption, carrier diffusion, and recombination mechanisms, the model was used to numerically simulate photovoltaic films of varying thicknesses. The distribution of photogenerated carriers at each thickness was calculated, resulting in the optimal thickness for the photovoltaic film. The simulation results were then verified experimentally.

[0043] Experimental design and data analysis

[0044] Experimental material preparation: Prepare photoelectric thin film samples of different thicknesses, ensuring that the surface of the samples is smooth and has no obvious defects.

[0045] Photoelectrochemical performance test: Using a xenon lamp light source and an electrochemical workstation, key parameters such as the photoresponse current and open circuit voltage of films of different thicknesses are measured.

[0046] Data analysis: By analyzing experimental data, the accuracy of the computational model is verified, and the optimized model is applied to more material systems to verify its wide applicability.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The calculation method and application of photogenerated minority carrier distribution described in this invention, through the establishment of a physical model and combined with experimental verification, provides an efficient means of predicting the optimal thickness of photovoltaic thin films. This model can provide theoretical guidance for photoelectrode design, reduce the number of experiments, lower research costs, and accelerate the development of new, high-efficiency photoelectrode materials.

[0049] The calculation method of the present invention also ensures the accuracy of model calculation, including:

[0050] Accurate simulation of light absorption properties: This model considers the absorption characteristics of photons of different wavelengths in thin film materials, as well as the effect of photon absorption on minority carrier generation. The model incorporates parameters such as the material's absorption coefficient, photon energy distribution, and the film's optical thickness, making the simulation of light absorption processes more realistic.

[0051] Detailed description of carrier generation and recombination mechanisms: This model takes into account the generation, diffusion, and recombination of minority carriers in the material, especially the interface and surface recombination.

[0052] Photovoltaic film thickness optimization algorithm: Based on the calculated distribution of photogenerated minority carriers, this paper further analyzes the diffusion and recombination of minority carriers in films of different thicknesses. By optimizing these parameters, the film thickness that maximizes photoelectric conversion efficiency is determined.

[0053] In summary, the present invention, through precise calculation of the distribution of photogenerated minority carriers and optimization of film thickness, not only significantly improves the photoelectric conversion efficiency of optoelectronic materials but also provides theoretical support for the design of novel optoelectronic materials. For example, optoelectronic devices using a CuBi2O4 photoelectric film with an optimal thickness of 100nm, as determined by the above-described method for calculating the distribution of photogenerated minority carriers, achieve a maximum photon-to-electron conversion efficiency of 20%. The photon-to-electron conversion efficiency of a 50nm-thick CuBi2O4 film is only 16.8%. This demonstrates that optimizing film thickness can significantly improve energy conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of the physical model for calculating the distribution of photogenerated minority carriers of the present invention;

[0055] Figure 2 The calculated results of minority carrier distribution of CuBi2O4 films of different thicknesses under front illumination in Example 1 of the present invention are as follows;

[0056] Figure 3 is a graph of surface minority carrier concentrations of CuBi2O4 films of different thicknesses when illuminated from the front in Example 1 of the present invention;

[0057] Figure 4 Calculation results of minority carrier distribution of CuBi2O4 films of different thicknesses when back-illuminated in Example 1 of the present invention;

[0058] Figure 5 This is a graph of surface minority carrier concentrations of CuBi2O4 films of different thicknesses when back-illuminated in Example 1 of the present invention;

[0059] Figure 6 The current density of the CuBi2O4 thin film in Example 1 of the present invention as a function of sample thickness, using 340nm LED front and back lighting. DETAILED DESCRIPTION

[0060] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the specific implementation method, they shall be carried out according to conventional conditions or conditions provided by the manufacturer.

[0061] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. Specific implementation method one:

[0063] A method for calculating the distribution of photogenerated minority carriers, the method comprising the following steps:

[0064] 1) Calculate the generation rate of photogenerated electron-hole pairs:

[0065] Obtaining the basic optical parameters of the thin film material, calculating the band gap energy of the thin film material through first-principles calculations, and then combining the reflection and transmission spectra of the thin film material to obtain the absorption coefficient α; based on the absorption coefficient α of the thin film material, calculating the absorption depth of the incident photon in the thin film, and finally calculating the generation rate G of photogenerated electron-hole pairs using formula I;

[0066] G=αφ0e -αx Formula I;

[0067] Where φ0 is the luminous flux per unit area, that is, the number of photons incident on the surface of the material; χ is the thickness of the film material;

[0068] 2) Carrier diffusion and recombination;

[0069] 3) Establish a mathematical model and solve it:

[0070] 3.1) The model equation is:

[0071] Where n is the minority carrier concentration, D is the minority carrier diffusion coefficient, μ is the minority carrier mobility, E is the electric field strength, τ is the minority carrier lifetime, and L is the minority carrier diffusion length;

[0072] 3.2) Determine boundary conditions

[0073] At the semiconductor / electrolyte interface, the boundary condition for x=0 is Formula III; at the semiconductor / substrate interface, the boundary condition for x=d is Formula IV;

[0074]

[0075] Where S is the surface recombination velocity, Si is the interface recombination velocity, and E0 is the surface electric field intensity;

[0076] 3.3) Use the finite difference method to discretize the continuous model equation to obtain the discretized equation:

[0077]

[0078] in, h is the spatial step length;

[0079] 3.4) Convert the discretized equation into a matrix form An = g, where A is a (d + 2)-dimensional square matrix, and n and g are (d + 2)-dimensional column vectors;

[0080] 3.5) Calculate the electric field distribution:

[0081] The relationship between electric field intensity E and electric potential φ is:

[0082] The electric potential distribution is obtained by solving the Poisson equation, and then the electric field distribution is calculated;

[0083] 3.6) Use linear algebra methods to solve the matrix equation An = g and obtain the photogenerated minority carrier distribution n(x).

[0084] In other embodiments, the model equation is a simplified continuity equation of minority carriers under steady-state conditions;

[0085] The continuity equation is:

[0086] Wherein, t is time; the steady-state condition is:

[0087] In other embodiments, in step 3.2), S and Si in the boundary conditions are idealized to 0 and ∞, respectively; 0 indicates that all minority carriers moving to the surface participate in the reaction, and ∞ indicates that all minority carriers moving to the interface undergo recombination losses.

[0088] In other embodiments, the calculation method solves two photogenerated minority carrier distributions n(x) under different film thicknesses for two cases where the light source is incident from the front and back.

[0089] In other embodiments, the minority carrier concentration N of the thin film material is measured by the Mott-Schottky method. A , flat band potential V fb and slope s;

[0090] By formula Calculate n, where ε0 is the dielectric constant of vacuum, C sc Refers to the capacitance formed at the semiconductor-electrolyte interface;

[0091] Calculate the minority carrier mobility μ according to the formula σ=neμ, where σ is the conductivity;

[0092] Through the formula μ=eτ h m * Calculate the mean free time τ of majority carriers h , where m * is the effective mass of minority carriers; set the mean free time τ of minority carriers e Equal to the mean free time τ of majority carriers h , then by the formula Calculate the diffusion coefficient D of minority carriers and further obtain the diffusion length of minority carriers where k B is the Boltzmann constant, and T is the absolute temperature. Specific implementation method two:

[0094] A use of the method for calculating the distribution of photogenerated minority carriers based on any one of the above embodiments, wherein the method for calculating the distribution of photogenerated minority carriers is used to determine the optimal thickness of a photovoltaic thin film.

[0095] In other embodiments, the photovoltaic film includes an oxide semiconductor film.

[0096] In other embodiments, the oxide semiconductor film is a CuBi2O4 film, a BiFeO3 film, or a CuFeO2 film.

[0097] In other embodiments, the optimal thickness of the CuFeO3 thin film material is 300 nm, the optimal thickness of the CuBi2O4 thin film is 100 nm, and the optimal thickness of the Fe2O3 thin film is 50 nm.

[0098] In other embodiments, the error range of the optimal thickness of the photovoltaic thin film determined by the calculation method of the photogenerated minority carrier distribution is ±10 nm.

[0099] Example 1:

[0100] A method for calculating the distribution of photogenerated minority carriers, such as Figure 1 FIG. 1 is a schematic diagram of a physical model for calculating the distribution of photogenerated minority carriers according to the present invention. In this embodiment 1, the photoelectrode film is taken as an example of a CuBi2O4 film.

[0101] Step 1: Calculation of light absorption characteristics: First, obtain the basic optical parameters of the CuBi2O4 thin film material. The band gap energy of the material can be obtained through first-principles calculations. Combined with the reflection and transmission spectra of the film, the absorption coefficient α can be obtained. Based on the absorption coefficient of the material, the absorption depth of the incident photon in the film can be calculated. Finally, the formula G = αφ0e-αx Calculate the generation rate of photogenerated electron-hole pairs.

[0102] Step 2 Diffusion and recombination of minority carriers: This example adds parameters of the surface recombination velocity S and the interface recombination velocity Si to the diffusion model, idealizing them to 0 and ∞, respectively, indicating that all minority carriers moving to the surface participate in the reaction, and all minority carriers moving to the interface suffer recombination losses.

[0103] Step 3: Establish a mathematical model and solve it: The core equation of the model is: Where n is the minority carrier concentration, D is the minority carrier diffusion coefficient, μ is the minority carrier mobility, E is the electric field strength, τ is the minority carrier lifetime, and L is the minority carrier diffusion length. First, we need to determine D, μ, and L.

[0104] In this example 1, the minority carrier concentration n, flat band potential Vfb and slope s of CuBi2O4 material are measured by Mott-Schottky method. The minority carrier concentration n is calculated as follows: Where ε0 is the dielectric constant of vacuum. The minority carrier mobility μ is calculated based on the conductivity σ = neμ. According to μ = eτ h m * , combined with the effective mass m* of the minority carriers, the mean free time τ of the majority carriers can be calculated h Assuming the mean free time τ of minority carriers e Equal to the mean free time τ of majority carriers h , then according to The minority carrier diffusion coefficient D is calculated using the formula.

[0105] Transform the equation into The obtained parameters are brought into the discretization and equation solving. For the two cases where the light source is incident from the front and back, two photogenerated minority carrier distributions n(x) under different film thicknesses are solved, such as Figure 2 and Figure 4 As shown. Solving the continuity equation by the above method can obtain the carrier concentration distribution on the film surface, as shown in Figure 3 and Figure 5 shown.

[0106] Step 4 Optimization of the thickness of the photoelectric film: It can be clearly seen that when the thickness is greater than the light penetration depth, the electron distribution in the sample gradually tends to be constant, such as Figure 2 A similar trend is seen in backlighting, as shown in Figure 4 However, the thickness-dependent photocurrents show different trends in these two cases, as Figure 3 and Figure 5As shown in the figure, the photocurrent under frontal illumination gradually increases and approaches its maximum value. Under backside illumination, the photocurrent first increases, reaches its maximum value at around 50 nm, and then rapidly decreases. The current under frontal illumination is greater than that under backside illumination. Therefore, we predict that the maximum photocurrent of the CuBi2O4 film under frontal illumination will occur when the thickness is around 100 nm.

[0107] Step 5 Experimental design and data analysis:

[0108] The photoelectrochemical performance of CuBi2O4 films of different thicknesses was tested by irradiating them with a 340nm wavelength LED light source from the front and back. The photocurrent density-film thickness curves are shown in the figure. Figure 6 As shown in the figure. Under front illumination, the photocurrent density does not vary much within the thickness range studied. The incident photon-to-electron conversion efficiency reaches 20%. In contrast, the photocurrent under back illumination decreases exponentially with increasing film thickness, with an incident photon-to-electron conversion efficiency of only 5%. In the strong absorption mechanism, this trend can be described by the formula J∝exp(-W / De), where De is the electron diffusion length and W is the thickness of the sample. The experimental result here is De = 45 ± 5 nm, which is consistent with previous research results and verifies the accuracy of the model.

[0109] Through systematic calculation and experimental verification, the present invention provides a practical calculation model for the distribution of photogenerated minority carriers and a method for optimizing the thickness of photoelectric thin films, which is suitable for the design and optimization of various photoelectric materials and has broad application prospects.

[0110] The present invention is described by the above-mentioned specific embodiments. It should be understood by those skilled in the art that various changes and equivalent substitutions may be made to the present invention without departing from the scope of the present invention. Parts not described in detail in the present specification are well-known technologies to those skilled in the art. In addition, various modifications may be made to the present invention for specific situations or specific circumstances without departing from the scope of this new use. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims of the present invention.

Claims

1. A method for calculating the distribution of photogenerated minority carriers and its use, characterized by: The calculation method comprises the following steps: 1) Calculate the generation rate of photogenerated electron-hole pairs: Obtaining the basic optical parameters of the thin film material, calculating the band gap energy of the thin film material through first-principles calculations, and then combining the reflection and transmission spectra of the thin film material to obtain the absorption coefficient α; based on the absorption coefficient α of the thin film material, calculating the absorption depth of the incident photon in the thin film, and finally calculating the generation rate G of photogenerated electron-hole pairs using formula I; G=αφ0e -αx Formula I; Where φ0 is the luminous flux per unit area, that is, the number of photons incident on the surface of the material; χ is the thickness of the thin film material; 2) Carrier diffusion and recombination; 3) Establish a mathematical model and solve it: 3.1) The model equation is: Where n is the minority carrier concentration, D is the minority carrier diffusion coefficient, μ is the minority carrier mobility, E is the electric field strength, τ is the minority carrier lifetime, and L is the minority carrier diffusion length; 3.2) Determine boundary conditions At the semiconductor / electrolyte interface, the boundary condition for x=0 is Formula III; at the semiconductor / substrate interface, the boundary condition for x=d is Formula IV; Where S is the surface recombination velocity, Si is the interface recombination velocity, and E0 is the surface electric field intensity; 3.3) Use the finite difference method to discretize the continuous model equation to obtain the discretized equation: in, h is the spatial step length; 3.4) Convert the discretized equation into a matrix form An = g, where A is a (d + 2)-dimensional square matrix, and n and g are (d + 2)-dimensional column vectors; 3.5) Calculate the electric field distribution: The relationship between electric field intensity E and electric potential φ is: The electric potential distribution is obtained by solving the Poisson equation, and then the electric field distribution is calculated; 3.6) Use linear algebra methods to solve the matrix equation An = g and obtain the photogenerated minority carrier distribution n(x).

2. The method for calculating the distribution of photogenerated minority carriers according to claim 1, wherein: The model equation is obtained by simplifying the continuity equation of minority carriers under steady-state conditions; The continuity equation is: Wherein, t is time; the steady-state condition is:

3. The method for calculating the distribution of photogenerated minority carriers according to claim 2, wherein: In step 3.2), S and Si in the boundary conditions are idealized to 0 and ∞, respectively; 0 means that all minority carriers moving to the surface participate in the reaction, and ∞ means that all minority carriers moving to the interface suffer recombination losses.

4. The method for calculating the distribution of photogenerated minority carriers according to claim 3, wherein: The calculation method is based on two situations where the light source is incident from the front and back, and obtains two photogenerated minority carrier distributions n(x) under different film thicknesses.

5. The method for calculating the distribution of photogenerated minority carriers according to claim 4, wherein: The minority carrier concentration N of the thin film material was measured by the Mott-Schottky method. A , flat band potential V fb and slope s; By formula Calculate n, where ε0 is the dielectric constant of vacuum, C sc Refers to the capacitance formed at the semiconductor-electrolyte interface; Calculate the minority carrier mobility μ according to the formula σ=neμ, where σ is the conductivity; Through the formula μ=eτ h m * Calculate the mean free time τ of majority carriers h , where m * is the effective mass of minority carriers; set the mean free time τ of minority carriers e Equal to the mean free time τ of majority carriers h , then by the formula Calculate the diffusion coefficient D of minority carriers and further obtain the diffusion length of minority carriers where k B is the Boltzmann constant, and T is the absolute temperature.

6. A use of the method for calculating the distribution of photogenerated minority carriers according to any one of claims 1 to 5, characterized in that: The calculation method of the photogenerated minority carrier distribution is used to determine the optimal thickness of the photovoltaic film.

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