Stress detection method of organic light-emitting device

Abstract

The invention provides a stress detection method of an organic light-emitting device, which belongs to the technical field of stress detection, and comprises the following steps: preparing a micro-nano scale through hole at each detection point by using a focused ion beam technology, and depositing a layer of quantum dot film with a stress sensitive characteristic around the through hole; calling an extreme stress scene and two random normal stress scenes of the device, and obtaining appearance deformation information and a luminescence spectrum of the corresponding quantum dot film under each change node in the full life cycle change set; the luminescence spectrum is converted into a corresponding stress value, anisotropy is determined in combination with appearance deformation information, and the corresponding stress value is adjusted; obtaining a stress state according to all adjustment values of each step simulation under the same stress scene, and obtaining a state vector of the corresponding stress scene; and constructing a state matrix based on all the state vectors to obtain a state span variable quantity and a state safety proportion, and determining an improvement suggestion. Powerful support is provided for optimizing the device preparation process and improving the product quality.

Description

Technical Field

[0001] The present invention relates to the technical field of stress detection, and in particular to a method for detecting stress of an organic light-emitting device. Background Art

[0002] Due to its many advantages such as self-luminescence, high contrast, wide viewing angle, and flexible display, organic light-emitting devices have been widely used in the display field. However, during the preparation, encapsulation, and use of organic light-emitting devices, stress is extremely likely to be generated inside the devices. These stresses may stem from factors such as the mismatch of the thermal expansion coefficients of materials, the influence of the encapsulation process, and mechanical bending (for flexible organic light-emitting devices).

[0003] The existence of stress will bring a series of serious problems to organic light-emitting devices, such as reducing the luminous efficiency, shortening the device life, causing pixel defects, and even leading to device failure. At present, although the industry realizes the importance of stress detection, the existing stress detection means have many limitations. Traditional mechanical testing methods can often only detect the macroscopic stress on the device surface and are difficult to deeply reflect the stress distribution at the microscopic structure inside the device; while some detection technologies based on optical principles, such as photoelasticity, have poor adaptability to the complex optical anisotropic characteristics of organic materials, with low detection accuracy and being easily interfered by external ambient light.

[0004] Therefore, the present invention proposes a method for detecting stress of an organic light-emitting device. Summary of the Invention

[0005] The present invention provides a method for detecting stress of an organic light-emitting device, which can accurately and efficiently detect the stress conditions at different positions and different levels inside the device, providing strong support for optimizing the device preparation process and improving product quality.

[0006] The present invention provides a method for detecting stress of an organic light-emitting device, including: Step 1: Select an organic light-emitting device to be detected, select multiple detection points on the device surface, use the focused ion beam technology to prepare micro-nano scale through holes at each detection point, the depth of the through holes extends to the key structure layer inside the device, and deposit a layer of quantum dot film with stress-sensitive characteristics around the through holes, wherein the key structure layer includes at least one of an organic light-emitting layer, an electron transport layer, and a hole transport layer; Step 2: Retrieve the extreme stress scenario and any two normal stress scenarios of the organic light-emitting device to be detected, respectively simulate the full life cycle change sets of each quantum dot film under different stress scenarios, and obtain the appearance deformation information and emission spectrum of the corresponding quantum dot film at each change node in the full life cycle change sets; Step 3: Convert the emission spectrum into the corresponding stress value according to the calibration curve of the quantum dot stress-luminescence characteristics, and determine the anisotropy to adjust the corresponding stress value in combination with the appearance deformation information; Step 4: Construct the corresponding stress map of the organic electroluminescent device to be detected based on all the adjustment values of each step simulation under the same stress scenario to obtain the stress state, and obtain the state vector of the corresponding stress scenario; Step 5: Construct a state matrix based on all state vectors, and obtain the state span change amount and the state safety ratio under the same step simulation, and determine the improvement suggestions for the organic electroluminescent device to be detected.

[0007] Preferably, the deposition thickness of the quantum dot thin film is 10-100 nm.

[0008] Preferably, the simulation of the quantum dot thin film under the stress scenario is related to the strain amounts of temperature, humidity, mechanical stretching, and temperature.

[0009] Preferably, the life cycle change set is realized based on multiple step simulations, and each step simulation corresponds to a change node, and the appearance deformation information of the quantum dot thin film under the change node is the appearance change between the end moment and the start moment of the corresponding step simulation.

[0010] Preferably, determining the anisotropy to adjust the corresponding stress value in combination with the appearance deformation information includes: Project the appearance deformation information into a preset space, and respectively capture the appearance change details at each unit angle, where the unit angle is 1°; Based on the detailed features of the appearance change details and the spatial increment features , construct a feature function , where there is a feature function at each unit angle ; Determine the anisotropy parameters according to the materials used in the quantum dot thin film, and in combination with the feature function , determine the theoretical value of the performance parameters of the quantum dot thin film at the corresponding unit angle, and obtain the correction factor at the corresponding unit angle, where the anisotropy parameters include: refractive index tensor and extinction coefficient tensor;

[0011]

[0012] Among them, represents the corresponding theoretical value of the performance parameters; represents the corresponding correction factor; represents the refractive index tensor for the feature function The first theoretical influence value; Indicates the extinction coefficient tensor for the eigenfunction The second theoretical influence value; Indicates the standard function; Adjust the corresponding stress values successively according to the correction factor to obtain the adjusted values.

[0013] Preferably, construct a corresponding stress map of the organic electroluminescent device to be detected based on all the adjusted values of each step simulation under the same stress scenario to obtain the stress state, including: Based on the adjusted values in 360 directions of each quantum dot thin film under each step simulation, obtain the value vector corresponding to the current step simulation; Construct a value matrix from the value vectors under all step simulations involved; Obtain the eigenvector of the value matrix and match it with the vector-state comparison table to obtain the corresponding stress state.

[0014] Preferably, obtain the state span change amount and the state safety ratio under the same step simulation, including: Sort the stress states under the same step simulation in different stress scenarios according to the extreme coefficient of the stress scenario to obtain the first sorting; Conduct an adjacent state difference analysis on the states in the first sorting to obtain a difference sorting, and obtain the maximum span change amount, the minimum span change amount, the average span change amount, and the variance of the span change amount, and then obtain the state span change amount;

[0015] Among them, Represents the corresponding state span change amount; Represents the corresponding average span change amount; Represents the corresponding maximum span change amount; Represents the corresponding minimum span change amount; Represents the corresponding variance of the span change amount; Is a threshold value, with a value of 0.1; Compare each stress state in the first sorting with the set standard under the same step simulation; Count the first number of stress states that meet the set standard, and calculate the ratio of the first number to all the numbers of the stress states involved in the first sorting as the state safety ratio.

[0016] Preferably, determine improvement suggestions for the organic electroluminescent device to be detected, including: Make a first comparison between the state span change amount under the same step simulation and the first threshold; Perform a second comparison between the state safety ratio under the same-step simulation and the second threshold; Based on the first bias of the first comparison result, the second bias of the second comparison result, and in combination with the actual application requirements of the organic electroluminescent device to be detected, determine improvement suggestions.

[0017] Compared with the prior art, the beneficial effects of this application are: Select a sample from the organic electroluminescent device to obtain a quantum dot thin film, which provides a sample basis for subsequent simulations of different stress scenarios. And then, through simulations of different stress scenarios, obtain a full-life cycle change set. Further, adjust and analyze the stress state by using the appearance change information to adjust the stress value obtained from the emission spectrum, and then optimize the organic electroluminescent device by combining the state span change amount and the state safety ratio, which provides strong support for optimizing the device manufacturing process and improving product quality. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a flowchart of the stress detection method for an organic electroluminescent device in an embodiment of the present invention. Detailed Embodiments

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0021] The present invention provides a stress detection method for an organic electroluminescent device, as Figure 1 shown, including: Step 1: Select an organic electroluminescent device to be detected, select a plurality of detection points on the device surface, use the focused ion beam technology to prepare micro-nano scale through holes at each detection point, the depth of the through holes extends to the key structure layer inside the device, and deposit a layer of quantum dot thin film with stress-sensitive characteristics around the through holes, where the key structure layer includes at least one of an organic light-emitting layer, an electron transport layer, and a hole transport layer; Step 2: Retrieve the extreme stress scenarios and any two random normal stress scenarios of the organic electroluminescent device to be detected, respectively simulate the full-life cycle change sets of each quantum dot thin film under different stress scenarios, and obtain the appearance deformation information and emission spectrum of the quantum dot thin film corresponding to each change node in the full-life cycle change sets; Step 3: Convert the emission spectrum into the corresponding stress value according to the quantum dot stress-luminescence characteristic calibration curve, and adjust the corresponding stress value by combining the appearance deformation information to determine the anisotropy; Step 4: Construct the corresponding stress map of the organic electroluminescent device to be detected based on all the adjusted values of each step simulation under the same stress scenario to obtain the stress state, and obtain the state vector of the corresponding stress scenario; Step 5: Construct a state matrix based on all the state vectors, obtain the state span change amount and the state safety occupancy ratio under the same step simulation, and determine the improvement suggestions for the organic electroluminescent device to be detected.

[0022] Preferably, the deposition thickness of the quantum dot thin film is 10 - 100 nm.

[0023] Preferably, the simulation of the quantum dot thin film under the stress scenario is related to the strain of temperature, humidity, mechanical stretching and temperature.

[0024] Preferably, the life cycle change set is realized based on multiple step simulations, each step simulation corresponds to a change node, and the appearance deformation information of the quantum dot thin film under the change node is the appearance change between the end moment and the start moment of the corresponding step simulation.

[0025] In this embodiment, first select the organic electroluminescent device to be detected, and reasonably select multiple detection points on the device surface. Using the focused ion beam technology, precisely prepare micro-nano scale through-holes at each detection point, so that the through-hole depth extends to the key structure layers inside the device (such as the organic light-emitting layer, electron transport layer, hole transport layer, etc.). Then, adopt a suitable thin film deposition technology (such as atomic layer deposition) to deposit a layer of quantum dot thin film with stress-sensitive characteristics with a thickness of 10 - 100 nm around the through-holes, prepare uniformly distributed micro-nano through-holes on the device surface, and deposit a complete quantum dot thin film. Through scanning electron microscope (SEM) observation, the through-hole diameter is controlled within 50 - 200 nm, the depth accurately reaches the target key structure layer, the quantum dot thin film has a uniform thickness, and is tightly combined with the through-hole edge.

[0026] The thin film composed of quantum dot materials, quantum dots are nano-scale semiconductor crystals with unique optical and electrical properties. In this solution, a quantum dot material sensitive to stress is selected to make the thin film, such as cadmium sulfide (CdS) quantum dot thin film. When subjected to stress, its luminescence characteristics will change.

[0027] Retrieve the extreme stress scenarios (such as high temperature and high humidity, high mechanical stress, etc.) and any two random normal stress scenarios of the device to be detected. Place the prepared device in an environmental chamber that can precisely control conditions such as temperature, humidity, and mechanical tension, and simulate the full life cycle change sets of each quantum dot thin film under different stress scenarios respectively. The full life cycle change sets are achieved based on multiple step simulations. Each step simulation corresponds to a change node. At the end moment of each change node, collect the appearance deformation information (such as surface crack generation, film wrinkling, etc.) and the emission spectrum of the quantum dot thin film.

[0028] When simulating the extreme stress scenario of high temperature and high humidity, through multiple step simulations, it is observed that tiny cracks begin to appear in the quantum dot thin film at the 5th change node, and the peak wavelength of the emission spectrum undergoes an obvious red shift; in the simulation of the normal stress scenario, the film appearance changes less and the emission spectrum is relatively stable.

[0029] The stress scenario refers to various stress environments that an organic electroluminescent device may face during actual use. For example, the extreme stress scenario may be an environment at -40°C, 90% RH humidity, and high mechanical tensile stress; the normal stress scenario can be an environment at room temperature of 25°C, 50% RH humidity, and no obvious mechanical stress.

[0030] The full life cycle change set is a set of a series of change data recorded through multiple step simulations for the entire process of a quantum dot thin film from start to end under a specific stress scenario. For example, under a certain stress scenario, 10 step simulations are carried out, and the film appearance deformation information and emission spectrum data of each simulation together constitute the full life cycle change set under this scenario.

[0031] In this embodiment, according to the pre-established calibration curve of the quantum dot stress-emission characteristics, convert the collected emission spectrum into the corresponding stress value. Then, project the appearance deformation information into a preset space, with 1° as the unit angle, and capture the details of the appearance changes at each unit angle. Based on these detailed features and spatial increment features, construct a feature function (each unit angle corresponds to a feature function). Determine the anisotropic parameters such as the refractive index tensor and extinction coefficient tensor according to the materials used in the quantum dot thin film, combine the feature function to determine the theoretical value of the performance parameters of the quantum dot thin film at the corresponding unit angle, and calculate the correction factor. Finally, adjust the initial stress value with the correction factor to obtain the final adjusted value.

[0032] In this embodiment, the initial stress value converted from the emission spectrum through the calibration curve, after being adjusted in combination with the appearance deformation information, more accurately reflects the actual stress situation of the thin film. For example, at a certain unit angle, the initial stress value is 10 MPa, and after being adjusted by the correction factor, it becomes 12 MPa, which is closer to the actual mechanical test result.

[0033] The calibration curve of the stress-luminescence characteristics of quantum dots is a curve that establishes the corresponding relationship between the luminescence characteristics of quantum dots (such as the wavelength and intensity of the luminescence spectrum, etc.) and the stress they are subjected to through experiments. For example, in the experiment, different magnitudes of stress are applied to the quantum dot thin film, and at the same time, its luminescence spectrum is measured, and the calibration curve of the peak wavelength of the stress-luminescence spectrum is plotted.

[0034] For each quantum dot thin film under each step simulation, a value vector is obtained based on the adjustment values in 360 directions. The value vectors under all step simulations are constructed into a value matrix, and the eigenvectors of the value matrix are obtained by mathematical methods, and then matched with the pre-established vector-state comparison table to determine the corresponding stress state. Based on the constructed value matrix, the eigenvectors are obtained, and by matching with the comparison table, the stress state of the device under different step simulations can be accurately judged, such as the stress concentration state, the uniform stress state, etc.

[0035] For example, under a certain step simulation, the state span change amount is relatively large, and the state safety ratio is lower than the set standard. According to the analysis results, suggestions such as improving the device packaging process and optimizing the material selection are given.

[0036] The beneficial effects of the above technical solution are: Selecting a quantum dot thin film from the organic electroluminescent device as a sample provides a sample basis for subsequent simulations of different stress scenarios. And then, through the simulations of different stress scenarios, a full-life cycle change set is obtained. Further, the stress values obtained from the luminescence spectrum are adjusted by the appearance change information to analyze the stress state, and the organic electroluminescent device is optimized by combining the state span change amount and the state safety ratio, which provides strong support for optimizing the device manufacturing process and improving the product quality.

[0037] The present invention provides a stress detection method for an organic electroluminescent device, which combines appearance deformation information to determine anisotropy and adjusts the corresponding stress values, including: Projecting the appearance deformation information into a preset space, and respectively capturing the details of the appearance change at each unit angle, where the unit angle is 1°; Based on the detailed features of the appearance change details and the spatial increment features , a characteristic function is constructed , where there is a characteristic function at each unit angle ; Determine the anisotropy parameters according to the materials used in the quantum dot thin film, and combine the characteristic function , determine the theoretical value of the performance parameters of the quantum dot thin film at the corresponding unit angle, and obtain the correction factor at the corresponding unit angle, where the anisotropy parameters include: refractive index tensor and extinction coefficient tensor;

[0038]

[0039] wherein, represents the theoretical value of the corresponding performance parameter; represents the corresponding correction factor; represents the first theoretical influence value of the refractive index tensor on the characteristic function ; represents the second theoretical influence value of the extinction coefficient tensor on the characteristic function ; represents the standard function; Adjust the corresponding stress value successively according to the correction factor to obtain the adjusted value.

[0040] In this embodiment, the characteristic function is a mathematical function constructed based on the detailed features of the appearance change and the spatial increment features of the quantum dot thin film, and is used to describe the relationship between the film performance and these features. For example, a function constructed with variables such as the crack length on the film surface and the particle displacement and the increment features of the spatial position change can be used to predict the theoretical value of the performance parameter of the film in different states.

[0041] In this embodiment, takes a value of 0.6, takes a value of 0.4.

[0042] In this embodiment, the characteristic function has a value range of (0, 1), and the standard function has a value range of (0, 1). It should be noted that the value thresholds of the standard function under different step simulations are different. For example, when the temperature is 30° and the humidity is A1, the value threshold of the standard function is 0.8.

[0043] In this embodiment, adjusted value = stress value × (1 - absolute value of the correction factor).

[0044] Collect the appearance deformation information of the quantum dot thin film using high-resolution optical imaging devices (such as high-power microscopes, electron microscopes, etc.) to obtain image data containing changes in the microscopic structure of the film surface. Project this image data onto a preset three-dimensional space coordinate system, with a fixed point on the quantum dot thin film as the coordinate origin, to establish a virtual space model corresponding to the actual physical space of the film. Divide the preset space by unit angles of 1°, and through image analysis algorithms (such as edge detection, feature extraction algorithms), respectively identify and extract the details of the morphological changes on the film surface at each unit angle, such as the direction, length, and width changes of cracks, and the displacement and deformation of particles, etc. In the experiment of simulating the stress acting on the quantum dot thin film, the collected deformation images were successfully projected onto the preset space, clearly capturing the details at each unit angle. For example, in the angular range of 30° - 31°, a new tiny crack with a length of about 50 nm and a width of about 5 nm was detected on the film surface, providing accurate data for subsequent analysis.

[0045] The preset space is a virtual three-dimensional space coordinate system artificially set for mapping the actual physical space of the quantum dot thin film. For example, taking the lower left corner vertex of the film as the origin, a three-dimensional space with the X, Y, and Z axes corresponding to the length, width, and height directions of the film is established, and all the collected film appearance information can find corresponding positions in this space.

[0046] The unit angle is to analyze the deformation of the thin film in different directions in detail. The 360° circumference is divided into multiple equal-angle intervals, and each interval is the unit angle. In this step, the unit angle is set to 1°, which means starting from 0° and analyzing the appearance change of the thin film every 1° to comprehensively cover the deformation information of the thin film in all directions.

[0047] Extract the detailed features from the captured appearance change details at each unit angle, such as the number of cracks, shape parameters (curvature, angle, etc.), and morphological change parameters of particles. At the same time, calculate the position changes of each point on the film surface in the three-dimensional space at different times to obtain spatial increment features, such as displacement vectors, strain tensors, etc. Based on these detailed features and spatial increment features, combined with the physical properties of the quantum dot thin film and relevant physical laws (such as elasticity mechanics, surface physics, etc.), select a suitable mathematical function form (such as polynomial function, exponential function, etc.) to establish a mathematical model describing the relationship between the film performance and these features. Train and optimize the model with a large amount of experimental data, adjust the model parameters, so that the model can accurately reflect the law of the film performance changing with the appearance change, and finally form the corresponding characteristic function at each unit angle. Taking the 45° direction as an example, the error between the predicted value and the actual measured value is within 5%.

[0048] The detailed features refer to the specific and local characteristic parameters in the appearance change of the quantum dot thin film. For example, the length, width, and bifurcation of cracks on the film surface, and the changes in the size and shape of particles all belong to the detailed features. These features are the intuitive manifestation of the local physical changes of the thin film under stress.

[0049] The spatial increment features describe the characteristics of the positions of points on the thin film surface changing with time or stress in three-dimensional space. For example, under the action of stress, a point on the thin film moves from the initial position (x1, y1, z1) to (x2, y2, z2), and its displacement vector [(x2 - x1), (y2 - y1), (z2 - z1)] is a form of manifestation of the spatial increment features, reflecting the overall deformation trend of the thin film.

[0050] According to the specific materials used in the quantum dot thin film (such as CdS, CdSe, etc.), through technical means such as X-ray diffraction (XRD) and spectral analysis, the crystal structure, electronic band structure, etc. of the materials are measured, and then anisotropic parameters such as the refractive index tensor and extinction coefficient tensor are calculated. At each unit angle, the determined anisotropic parameters and the appearance change characteristics corresponding to this angle (obtained from step 2) are substituted into the corresponding characteristic functions. According to the mathematical expression of the characteristic function, the theoretical values of the performance parameters of the quantum dot thin film at this unit angle are calculated, such as the theoretical refractive index and theoretical extinction coefficient. Through experimental measurement or reference to standard data, the actual measured values (or standard reference values) of the thin film performance parameters at this unit angle are obtained. The actual measured values (or standard reference values) are compared with the theoretically calculated values, and the correction factor is calculated according to the formula "correction factor = actual measured value (or standard reference value) / theoretically calculated value" for the corresponding unit angle. In the experiment on a certain CdSe quantum dot thin film, it is calculated that there is a difference between the theoretical value and the actual measured value of the performance parameters at the 60° unit angle, and the correction factor is obtained as 0.1 through calculation. This correction factor indicates that the theoretically calculated value needs to be multiplied by (1 - 0.1) to be closer to the actual situation, providing a basis for subsequent stress value adjustment.

[0051] After obtaining the correction factor for each unit angle, for the stress values previously obtained through the conversion of the quantum dot stress-luminescence characteristic calibration curve, multiplication operations are performed with the corresponding correction factors in sequence according to the unit angle. That is, the adjusted value = initial stress value × correction factor, and the stress adjustment value corrected by the anisotropy and appearance deformation factors is obtained, making the stress value more accurately reflect the true stress state of the quantum dot thin film under actual stress. In the simulated stress detection experiment, after correcting the initial stress value of a certain quantum dot thin film, the adjusted value is more in line with the actual stress distribution. For example, the initial stress value is 8 MPa, and after being adjusted by the correction factor, it is 7.2 MPa, which is closer to the actual stress value of 7.2 MPa measured by a high-precision stress sensor, effectively improving the accuracy of stress detection.

[0052] The stress value initially obtained through the quantum dot luminescence spectrum combined with the calibration curve is the initial stress value, which does not fully consider the anisotropy and appearance deformation effects of the thin film. For example, when the thin film is subjected to tensile stress, the initial stress value may underestimate the actual stress due to the neglect of anisotropy, and the adjusted value after correction can more accurately reflect the stress condition of the thin film in this direction.

[0053] The beneficial effects of the above technical solution are: The characteristic function can accurately predict the optical property changes of the thin film caused by appearance deformation under different stress conditions, and the stress value corrected by the correction factor more truly reflects the actual stress state of the thin film.

[0054] The present invention provides a method for detecting the stress of an organic electroluminescent device. The corresponding stress map of the organic electroluminescent device to be detected is constructed according to all the adjusted values of each step simulation in the same stress scenario to obtain the stress state, including: Based on the adjusted values in 360 directions of each quantum dot thin film under each step simulation, a value vector corresponding to the current step simulation is obtained; A value matrix is constructed from the value vectors under all the step simulations involved; The eigenvector of the value matrix is obtained and matched with the vector-state comparison table to obtain the corresponding stress state.

[0055] In this embodiment, the value vector is a vector composed of the stress adjustment values in 360 directions of each quantum dot thin film under each step simulation. For example, under a certain step simulation, the adjusted values in 360 directions are arranged in sequence to form a vector with a length of 360.

[0056] In this embodiment, the vector-state comparison table is established in advance through a large number of experiments and analyses, and is a table that associates different eigenvectors with the corresponding stress states. For example, the eigenvector [0.1, 0.2, 0.3,...] corresponds to the stress concentration state, and [0.05, 0.05, 0.05,...] corresponds to the uniform stress state.

[0057] In this embodiment, the value matrix is obtained by arranging the value vectors under several step simulations with gradually increasing variables in the order of up and down rows.

[0058] The beneficial effects of the above technical solution are: Constructing a value matrix based on the value vector and then obtaining the eigenvector provides a reliable basis for obtaining the stress state.

[0059] The present invention provides a method for detecting the stress of an organic electroluminescent device, obtaining the state span change amount and the state safety ratio under the same step simulation, including: Sort the stress states under the same-step simulation in different stress scenarios in sequence according to the extreme coefficient of the stress scenario to obtain the first sorting; Conduct an adjacent-state difference analysis on the first sorted state to obtain a difference sorting, and obtain the maximum span change, minimum span variable, average span change, and span change variance, and then obtain the state span change;

[0060] Among them, represents the corresponding state span change; represents the corresponding average span change; represents the corresponding maximum span change; represents the corresponding minimum span change; represents the corresponding span change variance; is the threshold, with a value of 0.1; Compare each stress state in the first sorting with the set standard under the same-step simulation respectively; Count the first quantity of stress states that meet the set standard, and calculate the ratio of the first quantity to all quantities of stress states involved in the first sorting as the state safety ratio.

[0061] The state span change is used to measure the change degree of stress states during the same-step simulation under different stress scenarios. For example, in the same-step simulation of different stress scenarios, when the stress state changes from uniform stress to stress concentration, its state span change is relatively large.

[0062] The state safety ratio represents the proportion of the number of stress states that meet the set standard in the total number of stress states under the same-step simulation. For example, if the set standard is that the stress value is safe within a certain range, and 80% of the stress states meet this standard in the same-step simulation, then the state safety ratio is 80%.

[0063] An extreme coefficient is set for each stress scenario. This coefficient is used to measure the severity of the stress scenario and can be determined based on the combined effects of parameters such as temperature, humidity, and mechanical stress in the scenario. For example, the extreme coefficient of a stress scenario with high temperature, high humidity, and high mechanical tension can be set to a relatively high value, while the extreme coefficient of a normal stress scenario with normal temperature, normal humidity, and no obvious mechanical stress is set to a relatively low value. For all stress states under the same-step simulation, they are sorted according to the magnitude of the extreme coefficient of the stress scenario to which they belong, thus obtaining the first sorting. During the sorting process, common sorting algorithms such as bubble sort and quick sort can be used to arrange the stress states corresponding to the stress scenarios with large extreme coefficients in the front and those with small extreme coefficients in the back, and the value range of the extreme coefficient is from 0 to 1. In the stress test experiment of simulating an organic electroluminescent device, three stress scenarios are set: high temperature and high humidity (80°C, 90%RH) and high mechanical tension (strain 5%), normal temperature and normal humidity (25°C, 50%RH) with no mechanical stress, and low temperature and low humidity (-20°C, 20%RH) and slight mechanical compression (strain 1%). Their extreme coefficients are set to 0.9, 0.1, and 0.5 respectively. Under a certain-step simulation, the stress states corresponding to these three scenarios are obtained. After sorting, the first sorting is the stress state of the high-temperature and high-humidity and high-mechanical-tension scenario, the stress state of the low-temperature and low-humidity and slight-mechanical-compression scenario, and the stress state of the normal-temperature and normal-humidity and no-mechanical-stress scenario.

[0064] After obtaining the first sorting, a difference analysis is performed on adjacent stress states. Specifically, the difference between adjacent states is measured by calculating the differences of key parameters (such as stress values, strain values, optical performance parameters, etc.) in the stress states. For the difference values of all adjacent states, the maximum value, minimum value, average value, and variance are statistically analyzed. The maximum value is the maximum span change, the minimum value is the minimum span variable, the average value is the average span change, and the variance reflects the dispersion degree of the span change. Combining these values gives the state span change. For example, if the values of a certain key stress parameter of adjacent stress states are 10 MPa, 12 MPa, and 15 MPa respectively, then the differences between adjacent states are 2 MPa and 3 MPa, the maximum span change is 3 MPa, the minimum span variable is 2 MPa, and the average span change is (2 + 3) / 2 = 2.5 MPa. Based on the first sorting of the above experiment, a difference analysis is performed on multiple key parameters of adjacent stress states. Taking the stress value as an example, the stress value differences between adjacent states are 8 MPa and 5 MPa. The calculated maximum span change is 8 MPa, the minimum span variable is 5 MPa, the average span change is 6.5 MPa, and the variance of the span change is 1.5. Combining these values, the state span change under this-step simulation is determined to evaluate the fluctuation degree of the influence of different stress scenarios on the stress state of the device.

[0065] Adjacent state difference refers to the difference in key performance parameters between two adjacent stress states in the first sorting. For example, in two adjacent stress states, the luminous intensity of the device is 100 cd / m² and 120 cd / m² respectively, then the adjacent state difference in terms of luminous intensity between them is 20 cd / m².

[0066] A series of standards are set in advance for the same-step simulation according to the performance requirements and safety standards of the organic light-emitting device, and these standards cover multiple aspects such as stress value range, strain range, optical performance indicators, etc. Each parameter of each stress state in the first sorting is compared with the corresponding set standards one by one to determine whether each stress state meets the standard requirements. The safety range of the device stress value under the same-step simulation is set as 0 - 20 MPa, the strain range is 0 - 3%, and the luminous intensity range is 80 - 150 cd / m² and other standards. After comparing the stress states in the first sorting, it is found that in the stress state of the high-temperature, high-humidity and high-mechanical-tensile scenario, the stress value reaches 25 MPa, exceeding the set standard; while the stress state of the normal-temperature, normal-humidity and no-mechanical-stress scenario meets all the standard requirements. The set standards are a series of performance index ranges formulated to evaluate whether the stress state of the organic light-emitting device is safe and qualified under a specific step simulation. For example, for the electrical performance of the device, standards such as working voltage range and current density range are set; for the optical performance, qualified intervals of brightness and chromaticity are set. These standards are determined according to the design requirements of the device, industry specifications and actual usage requirements.

[0067] Suppose there are 3 stress states in the first sorting, and 1 of them meets the set standards, then the state safety ratio is 1 / 3 ≈ 33.3%. This result indicates that under the current step simulation, about 33.3% of the stress states are within the safe and qualified range.

[0068] The beneficial effects of the above technical solution are: By analyzing the span change amount, the influence differences of different stress scenarios on the stress state of the device can be effectively determined, and the analysis of the state safety ratio can effectively indicate the risk situation faced by the device currently.

[0069] The present invention provides a stress detection method for an organic light-emitting device to determine improvement suggestions for the to-be-detected organic light-emitting device, including: Performing a first comparison between the span change amount of the state under the same-step simulation and a first threshold; Performing a second comparison between the state safety ratio under the same-step simulation and a second threshold; Determining improvement suggestions according to the first deviation of the first comparison result, the second deviation of the second comparison result, and in combination with the actual application requirements of the to-be-detected organic light-emitting device.

[0070] Based on the bias presented by the first comparison result and the second comparison result (i.e., the cases of being greater than, less than, or equal to the threshold), comprehensively consider the actual application requirements of the organic electroluminescent device to be detected. For example, if the device is applied to the aerospace display field with extremely high stability requirements, then even if the change amount of the state span and the state safety ratio are only slightly not up to the standard, relatively strict improvement measures need to be taken; while if it is applied to ordinary consumer electronics products, the degree of improvement measures can be relatively flexible. When the change amount of the state span is greater than the first threshold and the state safety ratio is lower than the second threshold, comprehensive improvements may be required in multiple aspects such as material selection, structural design, and manufacturing process; if only one of the indicators is not up to the standard, targeted optimization is carried out. For example, if the change amount of the state span is too large, the mechanical properties of the material can be considered for improvement or the device structure can be optimized to reduce stress concentration; if the state safety ratio is low, the quality inspection link can be strengthened or the encapsulation process can be improved to enhance the reliability of the device.

[0071] The beneficial effects of the above technical solutions are as follows: In the same stress scenario and step simulation, the change amount of the state span of the improved device is reduced, and the state safety ratio is increased, achieving the expected performance improvement effect. A series of measures aimed at improving the performance, reliability, and safety of the device are proposed according to the comparison results of the change amount of the state span and the state safety ratio with the threshold, combined with the actual application requirements of the device.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting stress of an organic electroluminescent device, characterized in that Including: Step 1: Select the organic electroluminescent device to be detected, select multiple detection points on the device surface, use the focused ion beam technology to prepare micro-nano scale through-holes at each detection point, the depth of the through-holes extends to the key structure layer inside the device, and deposit a quantum dot film with stress-sensitive characteristics around the through-holes. Among them, the key structure layer includes at least one of an organic light-emitting layer, an electron transport layer, and a hole transport layer; Step 2: Retrieve the extreme stress scenarios and any two random normal stress scenarios of the organic electroluminescent device to be detected, respectively simulate the full life cycle change sets of each quantum dot film under different stress scenarios, and obtain the appearance deformation information and emission spectrum of the quantum dot film corresponding to each change node in the full life cycle change sets; Step 3: Convert the emission spectrum into the corresponding stress value according to the quantum dot stress-luminescence characteristic calibration curve, and combine the appearance deformation information to determine the anisotropy and adjust the corresponding stress value; Step 4: Construct the corresponding stress map of the organic electroluminescent device to be detected based on all the adjusted values of each step simulation under the same stress scenario to obtain the stress state, and obtain the state vector corresponding to the stress scenario; Step 5: Construct a state matrix based on all state vectors, and obtain the state span change amount and state safety ratio under the same step simulation, and determine the improvement suggestions for the organic electroluminescent device to be detected.

2. The stress detection method of the organic electroluminescent device according to claim 1, wherein The deposition thickness of the quantum dot film is 10 - 100 nm.

3. The stress detection method for an organic electroluminescent device according to claim 1, characterized in that, The simulation of the quantum dot film under the stress scenario is related to the strain of temperature, humidity, mechanical tension, and temperature.

4. The stress detection method of the organic electroluminescent device according to claim 1, h characterized in that the life cycle change set is realized based on multiple step simulations, and each step simulation corresponds to a change node, and the appearance deformation information of the quantum dot film under the change node is the appearance change between the end moment and the start moment of the corresponding step simulation.

5. The stress detection method for an organic electroluminescent device according to claim 1, characterized in that, Combining the appearance deformation information to determine the anisotropy and adjust the corresponding stress value includes: Project the appearance deformation information into a preset space, and respectively capture the appearance change details at each unit angle, where the unit angle is 1°; Detail features based on the details of the appearance change and spatial increment features , construct a feature function , where there is a feature function at each unit angle ; Determine the anisotropy parameter according to the material used in the quantum dot thin film, and combine the characteristic function , determine the theoretical value of the performance parameter of the quantum dot thin film at the corresponding unit angle, and obtain the correction factor at the corresponding unit angle, where the anisotropy parameter includes: refractive index tensor and extinction coefficient tensor; Among them, represents the theoretical value of the corresponding performance parameter; represents the corresponding correction factor; represents the first theoretical influence value of the refractive index tensor on the eigenfunction ; represents the second theoretical influence value of the extinction coefficient tensor on the eigenfunction ; represents the standard function; Adjust the corresponding stress value successively according to the correction factor to obtain the adjusted value.

6. The stress detection method for an organic electroluminescent device according to claim 5, wherein Constructing the corresponding stress map of the organic electroluminescent device to be detected based on all the adjusted values of each step simulation under the same stress scenario to obtain the stress state includes: Based on the adjusted values of 360 directions of each quantum dot film under each step simulation, obtain the value vector corresponding to the corresponding step simulation; Construct a value matrix for all the value vectors involved in all step simulations; Obtain the eigenvector of the value matrix and match it with the vector-state comparison table to obtain the corresponding stress state.

7. The stress detection method of the organic electroluminescent device according to claim 1, wherein Obtaining the state span change amount and state safety ratio under the same step simulation includes: Sort the stress states under the same step simulation in different stress scenarios according to the extreme coefficient of the stress scenario to obtain the first sorting; Perform adjacent state difference analysis on the first sorting state to obtain a difference sorting, and obtain the maximum span change amount, the minimum span variable, the average span change amount, and the variance of the span change amount, and further obtain the state span change amount; Among them, represents the corresponding state span change amount; represents the corresponding average span change amount; represents the corresponding maximum span change amount; represents the corresponding minimum span change amount; represents the corresponding variance of the span change amount; is a threshold value, and its value is 0.1; Compare each stress state in the first sorting with the set standard under the same-step simulation respectively; Count the first quantity of stress states that meet the set standard, and calculate the ratio of the first quantity to all quantities of stress states involved in the first sorting as the state safety ratio.

8. The stress detection method of the organic electroluminescent device according to claim 1, wherein Determine improvement suggestions for the organic electroluminescent device to be detected, including: Perform a first comparison between the state span change amount under the same-step simulation and the first threshold; Perform a second comparison between the state safety ratio under the same-step simulation and the second threshold; Determine improvement suggestions according to the first bias of the first comparison result, the second bias of the second comparison result, and in combination with the actual application requirements of the organic electroluminescent device to be detected.

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