A method for fitting current-voltage characteristics of an organic thin film photodetector device

Abstract

The application discloses a current-voltage characteristic fitting method of an organic thin film light detection device. In the organic thin film light detection device, physical parameters such as carrier concentration distribution, potential distribution and recombination rate distribution cannot be measured through experiments. The application models and simulates the organic thin film light detection device, obtains the physical parameter distribution of the device and analyzes the performance of the device. By inputting basic parameters such as energy level, mobility, trap distribution and film thickness of the device, the current-voltage characteristic of the device is fitted, and the fitting curve is consistent with the actually measured experimental data. Therefore, the basic characteristics of the device can be directly mastered through calculation simulation, and further, some parameter values which are difficult to directly obtain in experiments are obtained through fitting of the experimental data, so as to meet the purpose of further studying the organic semiconductor device.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic devices, particularly to the field of electrical models for optoelectronic devices, and specifically to a method for fitting the current-voltage characteristics of the output of an organic thin-film photodetector. Background Technology

[0002] For organic photodetectors, charge injection from the metal electrodes under reverse bias is a significant source of noise. Organic semiconductor materials are diverse and exhibit varying properties, leading to inconsistent current-voltage characteristics in devices. Given the high cost of organic materials, it is necessary to conduct appropriate performance evaluations before device fabrication to select the best for mass production.

[0003] In the field of organic semiconductor optoelectronic device simulation, commonly used methods include Monte Carlo simulation and master equation simulation. Monte Carlo simulation, also known as random sampling, uses a large number of random numbers to conduct experiments to obtain specific patterns and then perform numerical solutions. This method is computationally time-consuming, requires a large amount of data, and its accuracy is directly related to the computation time and the amount of data. The underlying logic of master equation simulation is to model and analyze the device using physical equations describing the internal electrical transport of the device (including the Poisson equation, drift-diffusion equation, and continuity equation), thereby obtaining important physical parameters and device characteristics. Currently, this simulation method is mostly used for the performance analysis of organic light-emitting diodes (OLEDs) and organic solar cells. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, this invention provides a method for fitting the current-voltage characteristics of organic thin-film photodetectors. The method utilizes the master equation method to solve for the potential, charge density, and current distribution within the device, thereby fitting the device's current-voltage characteristics.

[0005] The fitting method involved in this invention mainly includes four processes: initial data input, solving for potential, solving for carrier concentration, and calculating current. Specifically, it is divided into the following steps:

[0006] A method for fitting the current-voltage characteristics of an organic thin-film photodetector, characterized by comprising the following steps:

[0007] Step 1: Define the active layer thickness and the set grid length of the organic thin-film photodetector as L and h, respectively. Divide the device into N (i.e., L / h) units along a direction perpendicular to the electrode plane. Record the starting point of the first unit, starting from the anode, as X. 1 The starting point of the last unit ending at the cathode is denoted as X. N X N+1 As the termination point, the midpoint of the j-th cell is moved to X. 1 The distance is defined as x j+1 / 2Based on the internal carrier concentration and potential distribution of the device, an initial value is given (e.g., Figure 5 (as shown);

[0008] Step 2: Apply the Poisson equation Calculate the internal potential distribution V of an organic semiconductor device old Where V(x) is the electric potential at position x (or can be expressed as...) (represented by q), where q is the unit charge, n(x) and p(x) represent the electron and hole concentrations at position x, and C(x) represents any other possible variations such as doping;

[0009] Step 3: Substitute the calculated potential distribution back into the Poisson equation; the differential form is as follows: in φ p(n) These represent the quasi-Fermi levels of holes and electrons, respectively, and their relationship with the corresponding carrier concentrations can be expressed as follows: Where h i This represents the length of the i-th grid point within the device;

[0010] Step 4: Using the updated Poisson equation, repeat step 2 to obtain the new potential distribution V. new ;

[0011] Step 5: Calculate V new With V old If the difference δV is greater than the set error value, return to step 2. new As V old V new +δV as V new Perform the calculation; otherwise, proceed to step 6.

[0012] Step 6: Apply the continuity equation Calculate the internal carrier concentration n of an organic semiconductor device old J n (x) and J p (x) represents the electron current density and hole current density at position x, and G(x) and R(x) represent the charge generation rate and recombination rate, respectively.

[0013] Step 7: Substitute the calculated carrier concentration distribution back into the continuity equation;

[0014] Step 8: Using the updated continuity equation, repeat step 6 to obtain the new carrier concentration n. new ;

[0015] Step 9: Calculate n new With n old If the difference δn is greater than the set error value, return to step 6, nnew As n old n new +δn as n new Perform the calculation; otherwise, proceed to step 10.

[0016] Step 10: Apply the drift-diffusion equation and The current density distribution within the device is calculated using the corrected potential distribution V and carrier concentration n. Where D... n =μ n，p ·V t Let μ be the Einstein diffusion coefficient. n，p For charge mobility, This is thermal voltage.

[0017] Furthermore, prior to step 1, the following steps are also included:

[0018] (1) Fabrication of organic thin-film photodetector devices;

[0019] (2) Obtain the energy levels of the electrodes and the bulk heterojunction by cyclic voltammetry or Kelvin testing;

[0020] (3) The thickness of the bulk heterostructure layer was obtained by step tester;

[0021] (4) Test the current-voltage curve of the fabricated device.

[0022] Furthermore, its device structure is composed of a substrate, a first electrode, a first charge-blocking layer (which can be removed), a bulk heterojunction photosensitive layer, a second charge-blocking layer (which can be removed), and a second electrode stacked in sequence.

[0023] Furthermore, the substrate is glass.

[0024] Furthermore, the first electrode is indium tin oxide (ITO); the first charge barrier layer is zinc oxide.

[0025] Furthermore, the bulk heterojunction photosensitive layer comprises an electron donor material and an electron acceptor material, wherein the electron donor material is PBDB-T and the acceptor material is any one or more of ITIC, IT-2F and IT-4F.

[0026] Furthermore, the second charge-blocking layer is molybdenum oxide (MoO3); the second electrode is silver (Ag).

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. This invention enables modeling and quantitative analysis of organic semiconductor devices, revealing the relationship between the microscopic physical properties and macroscopic performance of organic semiconductor devices.

[0029] 2. This invention relates to the trap state factor that is ubiquitous in organic semiconductor materials, further narrowing the difference between experimental data and theoretical simulation results, thereby verifying the role of trap states in device performance. Attached Figure Description

[0030] Figure 1 This is a flowchart of the current-voltage characteristic fitting method described in this invention.

[0031] Figure 2 These are the experimental and fitted values ​​of the current-voltage curve of the organic photodetector in Example 1 of this invention.

[0032] Figure 3 These are the experimental and fitted values ​​of the current-voltage curve of the organic photodetector in Example 2 of the present invention.

[0033] Figure 4 These are the experimental and fitted values ​​of the current-voltage curves of the organic photodetector in Example 3 of this invention.

[0034] Figure 5 This is a grid distribution diagram after one-dimensional spatial discretization. Detailed Implementation

[0035] This invention provides a method for fitting the current-voltage characteristics of the output of an organic thin-film photodetector. To more clearly illustrate this invention, the following examples will explain the specific fitting process proposed by this invention. Those skilled in the art should understand that the specific descriptions below are illustrative and not restrictive, and should not be construed as limiting the scope of protection of this invention.

[0036] Example 1

[0037] A method for fitting the current-voltage characteristics of an organic thin-film photodetector, wherein the fabrication process of the organic thin-film photodetector includes the following steps: An ITO substrate is ultrasonically cleaned sequentially with a cleaning agent, acetone, deionized water, and isopropanol, and then dried in a 75°C oven; a pure zinc oxide precursor solution is spin-coated onto the ITO substrate at 2600 rpm using a spin coater, and then annealed on a 200°C heating stage for 1 hour; an electron donor material PBDB-T and an electron acceptor material ITIC are mixed at a 1:1 mass ratio and dissolved in chlorobenzene (CB) to a total concentration of 30 mg / ml; the blended solution of the electron donor and electron acceptor materials is spin-coated onto the ITO substrate using a spin coater to obtain an active layer film with a thickness of approximately 280 nm; the device is transferred to a vapor deposition chamber, and when the vacuum level of the vapor deposition chamber drops to 3 × 10⁻⁶, the process is repeated. -6 During the bar deposition process, 10 nm thick MoO3 and 100 nm thick metallic Ag are deposited sequentially.

[0038] The above-mentioned method for fitting the current-voltage characteristics of an organic thin-film photodetector includes four modules: a data input module, a potential calculation module, a carrier concentration calculation module, and a current calculation module.

[0039] The first module, the data input module, requires inputting test parameters. These parameters are categorized into three types: material physical properties (bandgap width, photosensitive layer thickness, electron mobility, hole mobility, lattice constant, contact barrier, effective density of states in the valence / conduction band, ambient temperature), trap parameters (trap state density, trap state Gaussian distribution width, trap state central energy level), and test parameters (voltage range, test step size, number of cycles). Preferably, among the material physical properties, the bandgap width is set to 1.3 eV, the photosensitive layer thickness to 280 nm, and both electron and hole mobilities to 1*10⁻⁶. -4 cm -2 v -1 The lattice constant is 2.8, the left contact barrier is 1.2 eV, the right contact barrier is 0 eV, and the effective density of states in the valence band / conduction band is 1*10^6 eV. 25 m -3 The ambient temperature was 295K; in the trap parameters, the trap state density, the trap state Gaussian distribution width, and the trap state center energy level were not set, and the system was considered to be a trap-free material; in the test parameters, the voltage range was 0V to 10V, the test step size was 0.1V, and the number of cycles was 2.

[0040] The second module, the potential calculation module, calculates the potential distribution that conforms to the Poisson equation. The Poisson equation is expressed as... Its differential form is expressed as: in φp(n) These represent the quasi-Fermi levels of holes and electrons, respectively, and their relationship with the corresponding carrier concentrations can be expressed as follows: Where h i This represents the length of the i-th grid point within the device;

[0041] To correct the internal potential distribution of organic semiconductor devices using the Poisson equation, we calculate relevant physical quantities using the current carrier concentration and potential distribution in each iteration. Considering the boundary conditions of the potentials across the device, we obtain N+1 equations with N+1 unknowns, which can be represented as an N+1 order square matrix. Solving the matrix yields a numerical solution, which is compared to the required potential accuracy. The corrected potential distribution is then re-introduced into the Poisson equation, updating the coefficients and incorporating them into the next iteration. This process continues until the potential difference between two iterations is less than the set error value, at which point the process proceeds to the third module, the carrier concentration solution module. This third module calculates the carrier concentration distribution that conforms to the continuity equation. The continuity equation is expressed as follows: The derivative of electron concentration with respect to time can be expressed as: J n (x) and J p (x) represents the electron current density and hole current density at position x, G(x) and R(x) represent the charge generation rate and recombination rate, and n(x) represents the free electron concentration at position x.

[0042] Since the equation contains a first derivative, interpolation calculations are needed for the carrier concentration at two adjacent grid points. Here, an exponential distribution is first used for interpolation to calculate the electric field distribution of each grid, thus obtaining the carrier mobility. After considering the boundary conditions of carrier concentration at both ends of the device, electrons and holes can each yield N+1 equations containing N+1 unknowns, which can be represented as N+1 order square matrices. Solving the matrices yields a numerical solution, which is compared with the required accuracy of the carrier concentration distribution. The corrected carrier concentration is then substituted back into the equations, updating the coefficients and incorporating them into the next iteration until the accuracy requirement is met, at which point the process proceeds to the fourth module, the current calculation module.

[0043] The fourth module, the current calculation module, uses the drift-diffusion equation to determine the total current of the device. Given the aforementioned potential distribution and carrier concentration, the total current of the device can be calculated using the drift-diffusion equation. The drift-diffusion equation is expressed as follows: and Finally, the total current of the device is expressed as J(x) = J n (x)+J p (x). Where Dn=μ n，p ·V t Let μ be the Einstein diffusion coefficient.n，p For charge mobility, This is thermal voltage.

[0044] The fitted current-voltage curve is compared with the measured current-voltage curve to further correct the initial input trap parameters until the two curves coincide.

[0045] Example 2

[0046] A method for fitting the current-voltage characteristics of an organic thin-film photodetector, wherein the fabrication process of the organic thin-film photodetector includes the following steps: An ITO substrate is ultrasonically cleaned sequentially with a cleaning agent, acetone, deionized water, and isopropanol, and then dried in a 75°C oven; a pure zinc oxide precursor solution is spin-coated onto the ITO substrate at 2600 rpm using a spin coater, and then annealed on a 200°C heating stage for 1 hour; an electron donor material PBDB-T and an electron acceptor material IT-2F are mixed at a 1:1 mass ratio and dissolved in chlorobenzene (CB) to a total concentration of 30 mg / ml; the blended solution of the electron donor and electron acceptor materials is spin-coated onto the ITO substrate using a spin coater to obtain an active layer film with a thickness of approximately 280 nm; the device is transferred to a vapor deposition chamber, and when the vacuum level of the vapor deposition chamber drops to 3 × 10⁻⁶, the process is repeated. -6 During the bar deposition process, 10 nm thick MoO3 and 100 nm thick metallic Ag are deposited sequentially.

[0047] The aforementioned method for fitting the current-voltage characteristics of an organic thin-film photodetector includes four modules: a data input module, a potential calculation module, a carrier concentration calculation module, and a current calculation module.

[0048] The first module, the data input module, requires inputting test parameters. These parameters are categorized into three types: material physical properties (bandgap width, photosensitive layer thickness, electron mobility, hole mobility, lattice constant, contact barrier, effective density of states in the valence / conduction band, ambient temperature), trap parameters (trap state density, trap state Gaussian distribution width, trap state central energy level), and test parameters (voltage range, test step size, number of cycles). Preferably, among the material physical properties, the bandgap width is set to 1.3 eV, the photosensitive layer thickness to 280 nm, and both electron and hole mobilities to 1*10⁻⁶. -4 cm -2 v -1 The lattice constant is 2.8, the left contact barrier is 1.2 eV, the right contact barrier is 0.23 eV, and the effective density of states in the valence band / conduction band is 1*10^6. 25 m -3 The ambient temperature is 295K; among the trap parameters, the trap state density is 1×10⁻⁶. 22 m -3The Gaussian distribution width of the trap state is 60 meV, and the energy level of the trap state center is 0.3 eV. Among the test parameters, the voltage range is 0V to 10V, the test step size is 0.1V, and the number of cycles is 2.

[0049] The second module, the potential calculation module, calculates the potential distribution that conforms to the Poisson equation. The Poisson equation is expressed as... Its differential form is expressed as: in φ p(n) These represent the quasi-Fermi levels of holes and electrons, respectively, and their relationship with the corresponding carrier concentrations can be expressed as follows: Where h i This represents the length of the i-th grid point within the device;

[0050] To correct the internal potential distribution of organic semiconductor devices using the Poisson equation, we calculate relevant physical quantities using the current carrier concentration and potential distribution in each iteration. Considering the boundary conditions of the potentials across the device, we obtain N+1 equations with N+1 unknowns, which can be represented as an N+1 order square matrix. Solving the matrix yields a numerical solution, which is compared to the required potential accuracy. The corrected potential distribution is then re-introduced into the Poisson equation, updating the coefficients and incorporating them into the next iteration. This process continues until the potential difference between two iterations is less than the set error value, at which point the process proceeds to the third module, the carrier concentration solution module. This third module calculates the carrier concentration distribution that conforms to the continuity equation. The continuity equation is expressed as follows: The derivative of electron concentration with respect to time can be expressed as: J n (x) and J p (x) represents the electron current density and hole current density at position x, G(x) and R(x) represent the charge generation rate and recombination rate, and n(x) represents the free electron concentration at position x.

[0051] Since the equation contains a first derivative, interpolation calculations are needed for the carrier concentration at two adjacent grid points. Here, an exponential distribution is first used for interpolation to calculate the electric field distribution of each grid, thus obtaining the carrier mobility. After considering the boundary conditions of carrier concentration at both ends of the device, electrons and holes can each yield N+1 equations containing N+1 unknowns, which can be represented as N+1 order square matrices. Solving the matrices yields a numerical solution, which is compared with the required accuracy of the carrier concentration distribution. The corrected carrier concentration is then substituted back into the equations, updating the coefficients and incorporating them into the next iteration until the accuracy requirement is met, at which point the process proceeds to the fourth module, the current calculation module.

[0052] The fourth module, the current calculation module, uses the drift-diffusion equation to determine the total current of the device. Given the aforementioned potential distribution and carrier concentration, the total current of the device can be calculated using the drift-diffusion equation. The drift-diffusion equation is expressed as follows: and Finally, the total current of the device is expressed as J(x) = J n (x)+J p (x). Where D n =μ n，p ·V t Let μ be the Einstein diffusion coefficient. n，p For charge mobility, This is thermal voltage.

[0053] The fitted current-voltage curve is compared with the measured current-voltage curve to further correct the initial input trap parameters until the two curves coincide.

[0054] Example 3

[0055] A method for fitting the current-voltage characteristics of an organic thin-film photodetector, wherein the fabrication process of the organic thin-film photodetector includes the following steps: An ITO substrate is ultrasonically cleaned sequentially with a cleaning agent, acetone, deionized water, and isopropanol, and then dried in a 75°C oven; a pure zinc oxide precursor solution is spin-coated onto the ITO substrate at 2600 rpm using a spin coater, and then annealed on a 200°C heating stage for 1 hour; electron donor material PBDB-T and electron acceptor material IT-4F are mixed at a 1:1 mass ratio and dissolved in chlorobenzene (CB) to a total concentration of 30 mg / ml; the blended solution of electron donor and electron acceptor materials is spin-coated onto the ITO substrate using a spin coater to obtain an active layer film with a thickness of approximately 280 nm; the device is transferred to a vapor deposition chamber, and when the vacuum level of the vapor deposition chamber drops to 3 × 10⁻⁶, the process is repeated. -6 During the bar deposition process, 10 nm thick MoO3 and 100 nm thick metallic Ag are deposited sequentially.

[0056] The aforementioned method for fitting the current-voltage characteristics of an organic thin-film photodetector includes four modules: a data input module, a potential calculation module, a carrier concentration calculation module, and a current calculation module.

[0057] The first module, the data input module, requires inputting test parameters. These parameters are categorized into three types: material physical properties (bandgap width, photosensitive layer thickness, electron mobility, hole mobility, lattice constant, contact barrier, effective density of states in the valence / conduction band, ambient temperature), trap parameters (trap state density, trap state Gaussian distribution width, trap state central energy level), and test parameters (voltage range, test step size, number of cycles). Preferably, among the material physical properties, the bandgap width is set to 1.3 eV, the photosensitive layer thickness to 280 nm, and both electron and hole mobilities to 1*10⁻⁶. -4 cm -2 v -1 The lattice constant is 2.8, the left contact barrier is 1.2 eV, the right contact barrier is 2.1 eV, and the effective density of states in the valence band / conduction band is 1*10^6 eV. 25 m -3 The ambient temperature is 295K; among the trap parameters, the trap state density is 1×10⁻⁶. 22 m -3 The Gaussian distribution width of the trap state is 80 meV, and the energy level of the trap state center is 0.3 eV. Among the test parameters, the voltage range is 0V to 10V, the test step size is 0.1V, and the number of cycles is 2.

[0058] The second module, the potential calculation module, calculates the potential distribution that conforms to the Poisson equation. The Poisson equation is expressed as... Its differential form is expressed as: in φ p(n) These represent the quasi-Fermi levels of holes and electrons, respectively, and their relationship with the corresponding carrier concentrations can be expressed as follows: Where h i This represents the length of the i-th grid point within the device;

[0059] To correct the internal potential distribution of organic semiconductor devices using the Poisson equation, we calculate relevant physical quantities using the current carrier concentration and potential distribution in each iteration. Considering the boundary conditions of the potentials across the device, we obtain N+1 equations with N+1 unknowns, which can be represented as an N+1 order square matrix. Solving the matrix yields a numerical solution, which is compared to the required potential accuracy. The corrected potential distribution is then re-introduced into the Poisson equation, updating the coefficients and incorporating them into the next iteration. This process continues until the potential difference between two iterations is less than the set error value, at which point the process proceeds to the third module, the carrier concentration solution module. This third module calculates the carrier concentration distribution that conforms to the continuity equation. The continuity equation is expressed as follows: The derivative of electron concentration with respect to time can be expressed as: J n (x) and J p (x) represents the electron current density and hole current density at position x, G(x) and R(x) represent the charge generation rate and recombination rate, and n(x) represents the free electron concentration at position x.

[0060] Since the equation contains a first derivative, interpolation calculations are needed for the carrier concentration at two adjacent grid points. Here, an exponential distribution is first used for interpolation to calculate the electric field distribution of each grid, thus obtaining the carrier mobility. After considering the boundary conditions of carrier concentration at both ends of the device, electrons and holes can each yield N+1 equations containing N+1 unknowns, which can be represented as N+1 order square matrices. Solving the matrices yields a numerical solution, which is compared with the required accuracy of the carrier concentration distribution. The corrected carrier concentration is then substituted back into the equations, updating the coefficients and incorporating them into the next iteration until the accuracy requirement is met, at which point the process proceeds to the fourth module, the current calculation module.

[0061] The fourth module, the current calculation module, uses the drift-diffusion equation to determine the total current of the device. Given the aforementioned potential distribution and carrier concentration, the total current of the device can be calculated using the drift-diffusion equation. The drift-diffusion equation is expressed as follows: and Finally, the total current of the device is expressed as J(x) = J n (x)+J p (x). Where D n =μ n，p ·V t Let μ be the Einstein diffusion coefficient. n，p For charge mobility, This is thermal voltage.

[0062] The fitted current-voltage curve is compared with the measured current-voltage curve to further correct the initial input trap parameters until the two curves coincide.

[0063] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for fitting the current-voltage characteristics of an organic thin-film photodetector, characterized in that, Includes the following steps: Step 1: Define the active layer thickness and the set grid length of the organic thin-film photodetector as... L and h The device is divided into N units along a direction perpendicular to the electrode plane, and the starting point of the first unit, starting from the anode, is denoted as... X 1 The starting point of the last unit ending at the cathode is denoted as X N , X N+1 As the termination point, the midpoint of the j-th cell is moved to... X 1 The distance is defined as x j+1 / 2 An initial value is given based on the carrier concentration and potential distribution inside the device. Step 2: Apply the Poisson equation Calculate the internal potential distribution of organic semiconductor devices V old ,in for x The electric potential at the location, q For a unit charge, express x Electron and hole concentrations at location, This indicates any other possible variations or doping; Step 3: Substitute the calculated potential distribution back into the Poisson equation; the differential form is as follows: ,in This represents the length of the i-th grid point within the device; Step 4: Using the updated Poisson equation, repeat step 2 to obtain the new potential distribution V. new ; Step 5: Calculate V new With V old The difference If the error exceeds the set error value, return to step 2, V new As V old V new + As V new Perform the calculation; otherwise, proceed to step 6. Step 6: Apply the continuity equation Calculate the internal carrier concentration n of an organic semiconductor device old , and express x Electron current density and hole current density at location, Indicates charge generation rate and recombination rate; Step 7: Substitute the calculated carrier concentration distribution back into the continuity equation; Step 8: Using the updated continuity equation, repeat step 6 to obtain the new carrier concentration n. new ; Step 9: Calculate n new With n old The difference If the error exceeds the set error value, return to step 6. new As n old n new + As n new Perform the calculation; otherwise, proceed to step 10. Step 10: Apply the equation and The current density distribution within the device is calculated using the corrected potential distribution V and carrier concentration n; where The Einstein diffusion coefficient is... For charge mobility, This is thermal voltage.

2. The method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 1, characterized in that, Before step 1, the following steps are also included: (1) Fabrication of organic thin-film photodetector devices; (2) Obtain the energy levels of the electrodes and the bulk heterojunction by cyclic voltammetry or Kelvin testing; (3) The thickness of the bulk heterostructure layer was obtained by step tester; (4) Test the current-voltage curve of the fabricated device.

3. The method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 2, characterized in that, Its device structure consists of a substrate, a first electrode, a first charge-blocking layer, a bulk heterojunction photosensitive layer, a second charge-blocking layer, and a second electrode stacked sequentially.

4. The method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 2, characterized in that, The device structure consists of a substrate, a first electrode, a bulk heterojunction photosensitive layer, a second charge blocking layer, and a second electrode stacked sequentially.

5. The method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 2, characterized in that, The device structure consists of a substrate, a first electrode, a first charge blocking layer, a bulk heterojunction photosensitive layer, and a second electrode stacked sequentially.

6. The method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 2, characterized in that, The device structure consists of a substrate, a first electrode, a bulk heterojunction photosensitive layer, and a second electrode stacked sequentially.

7. A method for fitting the current-voltage characteristics of an organic thin-film photodetector according to any one of claims 3 to 6, characterized in that, The substrate is glass.

8. The method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 3 or 5, characterized in that, The first electrode is indium tin oxide (ITO); the first charge barrier layer is zinc oxide.

9. A method for fitting the current-voltage characteristics of an organic thin-film photodetector according to any one of claims 3 to 6, characterized in that, The bulk heterojunction photosensitive layer comprises an electron donor material and an electron acceptor material, wherein the electron donor material is PBDB-T and the acceptor material is any one or more of ITIC, IT-2F and IT-4F.

10. A method for fitting the current-voltage characteristics of an organic thin-film photodetector according to claim 3 or 4, characterized in that, The second charge-blocking layer is molybdenum oxide (MoO3); the second electrode is silver (Ag).

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