Spectrum detection system and method for defects of flexible organic semiconductor film

Abstract

The invention discloses a spectrum detection system and method for defects of a flexible organic semiconductor film, the detection method is implemented by adopting the detection system, and the detection system comprises a pump light source, a light splitting device, a film defect detection module, a background spectrum monitoring module and a data acquisition module; the pump light source is used for exciting pump light, the light splitting device is arranged on a light path of the pump light and is used for dividing the pump light into two paths, one path enters the film defect detection module, and the other path enters the background spectrum monitoring module; and the data acquisition module is used for collecting photo-thermal deflection signal spectral data generated by the film defect detection module and background spectral data generated by the background spectrum monitoring module. Accurate control of photo-thermal deflection light spots and the position of a tensile sample in the tensile test process of the organic film can be realized, so that the optimal signal stability, the measurement accuracy and the repeatability are ensured, the vacancy of a flexible film detection system in the market is filled, and hardware support is provided for scientific research and industrial upgrading of the flexible organic semiconductor film.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spectral detection technology, and in particular to a defect detection system and method for an organic semiconductor thin film. BACKGROUND

[0002] Organic semiconductor materials exhibit diverse and tunable optical, electrical, and magnetic properties due to their highly designable chemical structures, while possessing advantages such as lightweight flexibility, large-area solution processing, environmental friendliness, and biocompatibility. Based on these characteristics, related functional devices have become the core of flexible electronics research, driving the continuous expansion of their integrated applications. With continuous optimization of materials and device structures, organic semiconductor devices have gradually achieved stable optoelectronic performance under multi-dimensional mechanical strain, giving rise to the frontier direction of "stretchable semiconductor devices". This breakthrough has significantly expanded the application scenarios of devices, providing key support for wearable electronics, stretchable displays, and biomedical sensing, and continuously enabling the iterative upgrading of flexible electronics technology.

[0003] Unlike inorganic semiconductors with long-range ordered lattice structures, organic semiconductors are prone to form a large number of shallow and deep defect states due to intrinsic molecular conformation changes and complex intermolecular interactions in thin films, significantly affecting key processes such as optical absorption, carrier transport, and recombination. Therefore, characterization of the energy level structure of defect states is of great significance for in-depth understanding of the optoelectronic properties of organic semiconductors. During mechanical stretching of flexible organic thin films, lattice vibrations, chemical bond breakage, and intramolecular and intermolecular structure reconstruction further trigger the dynamic evolution of energy level structures and defect states. Therefore, achieving in-situ defect characterization under stretching conditions is a key step in revealing the physical mechanisms and guiding the design and optimization of materials and devices. Current typical techniques applied to defect characterization of organic semiconductors include space-charge-limited current (SCLC), deep level transient spectroscopy (DLTS), thermal admittance spectroscopy (TAS), and high-sensitivity external quantum efficiency (s-EQE). These techniques mainly target complete device structures and are difficult to directly and independently analyze defects in organic thin films. Photothermal deflection spectroscopy (PDS) is a high-sensitivity pump-probe characterization method based on photothermal effects, which can directly probe semiconductor thin films at room temperature. By coupling with theoretical models, this method not only has the ability to qualitatively identify defect types, but also can achieve quantitative analysis of parameters such as defect state density, thus exhibiting wide applicability and frontier value in the study of semiconductor material defects.

[0004] The application of the current photothermal deflection technology based on the pump-probe mechanism in this field still faces two significant limitations: first, there is a lack of photothermal deflection test platform design for flexible samples, making it difficult to meet the characterization needs under in-situ stretching conditions. Traditional photothermal deflection spectroscopy systems are mainly designed for inorganic semiconductor materials such as silicon, and their optical layout and calibration units are developed around rigid substrate materials, which cannot adapt to the deformation characteristics of flexible films during the stretching process. Second, the photothermal deflection test is highly sensitive to the relative position accuracy between the sample, the laser beam, and the detector. For flexible film samples that deform under in-situ stretching conditions, the existing test platform cannot accurately control and dynamically calibrate the positions of each module, which restricts the widespread application of photothermal deflection technology in flexible scenarios. Therefore, developing a photothermal deflection detection system with in-situ stretching and defect characterization functions will provide key support for the basic research and device performance optimization of flexible semiconductor materials, and has important scientific significance and application prospects. SUMMARY

[0005] The present application provides an integrated photothermal deflection spectroscopy detection system and method for in-situ defect characterization of flexible stretchable organic semiconductor thin films, to solve the technical problem that the existing detection devices cannot adapt to flexible samples mentioned in the background art.

[0006] To solve the above technical problems, the technical solution proposed by the present application is: A photothermal deflection spectroscopy detection system for defects of flexible organic semiconductor thin films, comprising a pump light source, a light splitting device, a thin film defect detection module, a background spectrum monitoring module, and a data acquisition module. The pump light source is used to excite pump light. The light splitting device is arranged on the optical path of the pump light and is used to divide the pump light into two paths, one of which enters the thin film defect detection module, and the other of which enters the background spectrum monitoring module. The data acquisition module is used to collect the photothermal deflection signal spectrum data generated by the thin film defect detection module and the background spectrum data generated by the background spectrum monitoring module. The thin film defect detection module includes a probe light generating device, a probe light receiving device, a cuvette for holding a test medium, and a stretching device for stretching the flexible organic semiconductor thin film. The stretching device is located inside the cuvette, and the stretching device makes the center of the organic semiconductor thin film coincide with the optical path of the pump light, so that the pump light forms a refractive index gradient in the test medium around the center of the organic semiconductor thin film. The probe light generating device is used to emit probe light that passes through the area around the center of the organic semiconductor thin film, and the probe light receiving device is used to receive the probe light after photothermal deflection to generate photothermal deflection signal spectrum data.

[0007] The present application is designed for flexible organic semiconductor thin film photothermal deflection detection system, the technical principle mainly depends on the optical mirage effect. Mirage effect refers to the deflection of light in the medium with refractive index gradient, which is caused by the spatial refractive index distribution caused by the change of temperature, density or composition. When the intensity modulated pump light irradiates the sample surface, the non-radiation heat absorption causes local temperature rise, and then forms a thermal induced refractive index gradient in the gas or liquid near the sample, so that the probe light beam vertically through the area is deflected slightly, which constitutes the physical basis of photothermal deflection signal, and is the specific application of mirage effect in photothermal deflection test. Through accurate measurement of the deflection angle, displacement and other information of the probe light combined with the corresponding physical model, the weak light absorption characteristics of the sample can be indirectly obtained, which is especially suitable for high sensitivity characterization of thin film semiconductor, photovoltaic material and other low absorption materials. The traditional photothermal deflection spectrum detection system is usually composed of fixed sample table, fixed incident pump light path and probe light path, and static signal receiver. This kind of system is mainly designed for traditional inorganic semiconductor materials. Because inorganic materials are usually rigid and brittle, they cannot be stretched for testing, so the position offset problem of the sample in the deformation process is not considered in the design. During the test, the relative position of the sample and the light beam remains fixed to meet the measurement requirements. However, when this kind of system is used for flexible organic thin film, the flexible thin film will produce obvious deformation and displacement during stretching, and the traditional device lacks dynamic adjustment ability, which cannot guarantee the effective alignment of the light beam and the sample, resulting in the drift or even loss of photothermal deflection signal, so it is difficult to obtain accurate test results. The light path of the photothermal deflection system is optimized from the traditional vertical arrangement to the parallel arrangement, and the sample can be vertically suspended in space by using the stretching device to meet the stretching requirements of flexible thin film, and an in-situ defect characterization detection device specially applied to flexible stretchable organic semiconductor thin film is obtained.

[0008] As a further preferred embodiment of the above technical solution, the stretching device is installed on the calibration platform, and the stretching device includes an upper sliding block, a lower sliding block and a threaded screw rod. The synchronous reverse or opposite movement of the upper sliding block and the lower sliding block is realized by rotating the threaded screw rod. After the sample is installed, the threaded screw rod is rotated to drive the two sliding blocks to move synchronously and reversely, so as to realize the stable stretching of the flexible sample, and ensure that the position of the probe light spot remains unchanged during stretching, so that the system of the present application has the functions of synchronous stretching and in-situ optical detection.

[0009] As a further preferred embodiment of the above technical solution, a scale ruler is arranged beside the threaded screw rod. The scale ruler is used to record the stretching amount.

[0010] As a further preferred embodiment of the above technical solution, the stretching device is mounted on the calibration platform via a connecting rod, and the calibration platform is driven by a driver to move in four directions (forward, backward, left, and right) and rotate around an axis in the horizontal direction.

[0011] As a further preferred embodiment of the above technical solution, the detection light receiving device is mounted on the detector base, and the detector base is driven by a driver to move in four directions (forward, backward, left, and right) in the horizontal direction, as well as rotate around the axis and adjust the pitch angle.

[0012] In photothermal deflection testing, the beam deflection angle is detected. With temperature gradient obey: ; To ensure that thermal fluctuations have the strongest effect on the probe beam, high-precision displacement control is required to keep the sample in the optimal measurement position at all times. However, during the in-situ stretching of the flexible thin film, the sample thickness changes with stretching, causing relative displacement between the sample and the beam, affecting the stability and accuracy of the signal. Furthermore, thickness variations lead to differences in material absorption and thermal diffusion behavior, resulting in significant changes in the probe beam deflection characteristics. This invention addresses these issues by constructing a calibration platform that uses a driver to adjust the position and angle of the stretching device, achieving high-precision adjustment of the sample's spatial position and angle to ensure the sample surface remains strictly parallel to the probe beam, thus improving signal stability. Simultaneously, the detector base precisely controls the position, angle, and pitch angle of the probe beam receiver, working in conjunction with the calibration platform. This provides the hardware foundation for subsequent real-time signal acquisition and analysis through programming, and for dynamically optimizing the sample and detector positions based on signal intensity distribution.

[0013] As a further preferred embodiment of the above technical solution, a collimating and focusing lens and a chopper are sequentially arranged along the optical path of the pump light between the beam splitter and the thin film defect detection module. After being shaped by the collimating and focusing lens, the pump light is periodically modulated by the chopper and focused onto the stretching device. The chopper modulates the continuous pump light into a periodic pulse signal and uses its frequency as a reference signal for synchronously extracting the photothermal deflection response signal.

[0014] As a further preferred embodiment of the above technical solution, the photothermal deflection signal spectral data generated by the thin film defect detection module is amplified by a lock-in amplifier and then sent to the data acquisition module.

[0015] As a further preferred embodiment of the above technical solution, the detector light generating device is a helium-neon laser generator with a power of 1.5~2mW and a power stability of less than 2.5%. The excitation light from the helium-neon laser generator has no destructive effect on the surface of the semiconductor sample, and the beam diameter matches the receiving area of ​​the photodetector, which is beneficial for efficient signal acquisition.

[0016] As a further preferred embodiment of the above technical solution, the pump source includes a xenon lamp and a monochromator arranged sequentially. The wavelength range of the excitation light output by the pump source is 250~2500nm, and the wavelength resolution is 5~20nm. If the refractive index gradient is too strong, it may cause nonlinear deflection of the probe light, thereby increasing background noise or even signal distortion; conversely, if the refractive index change is too small, the deflection angle is insufficient, and the signal strength received by the detector is too low, which will also lead to inaccurate measurement results. Therefore, in actual testing, this invention uses a kilowatt-level xenon lamp source combined with a monochromator to construct an adjustable monochromatic light source system as the pump excitation source. While ensuring sufficient excitation intensity, it has a wide spectral coverage range and is suitable for photothermal response testing of most semiconductor materials.

[0017] As a further preferred embodiment of the above technical solution, the background spectrum monitoring module includes a collimating focusing lens, a photodiode, and a photometer arranged sequentially along the optical path of the pump light. The pump light after beam splitting is focused onto the photodiode by the background spectrum collimating focusing lens group 6 for background signal detection. The photodiode is a thermal probe with active thermal background compensation function, which can achieve high-resolution, low-drift, low-power optical signal detection in the 190nm to 2500nm wavelength range. The photometer is connected to the data acquisition module for real-time acquisition and display of optical power data corresponding to different wavelengths, and for plotting real-time spectra.

[0018] As a further preferred embodiment of the above technical solution, the spectral detection system is entirely installed within a sealed enclosure. The outer surface of the enclosure is black, and the interior is lined with sound-absorbing cotton to shield against ambient light and noise interference. The enclosure is mounted on a pendulum-type air-float platform to reduce the impact of environmental vibrations on the system.

[0019] Based on the same technical concept, the present invention also provides a method for detecting defects in flexible organic semiconductor thin films according to the above-mentioned technical solution, which is implemented using a spectroscopic detection system for defects in flexible organic semiconductor thin films according to the above-mentioned technical solution, and includes the following steps: S1. Install the sample of the flexible organic semiconductor thin film in the stretching device of the thin film defect detection module, adjust the position of the stretching device, and stretch the flexible organic semiconductor thin film after filling the cuvette with the test medium. S2. After setting the parameters of the pump light source according to the properties of the sample, turn on the pump light source and the probe light generator. S3. The excitation light generated by the pump source goes to the thin film defect detection module, forming a refractive index gradient in the test medium around the center of the organic semiconductor thin film. The probe light generated by the probe light generator passes through the test medium with the refractive index gradient and undergoes photothermal deflection. It is then received by the probe light receiver to obtain the photothermal deflection signal spectral data. The excitation light generated by the pump source goes to the background spectrum monitoring module to obtain the background spectrum data. S4. Combining the photothermal deflection signal and the background spectrum, the absorption coefficient of the thin film is calculated using the Tauc model. Based on the absorption coefficient data of the thin film, the Urbach energy of the thin film is calculated using the Urbach model, thereby realizing a quantitative evaluation of the degree of defects in the thin film.

[0020] The present invention has the following beneficial effects: This invention establishes a biaxial in-situ tensile testing system and method suitable for flexible organic semiconductor thin films. It can achieve precise position control during the tensile process, thereby ensuring optimal signal stability, measurement accuracy and repeatability. It fills the gap in the market for flexible thin film testing systems and provides hardware support for scientific research and industrial upgrading of flexible organic semiconductor thin films. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the spectral detection system for defects in flexible organic semiconductor thin films according to Example 1; Figure 2 This is a schematic diagram of the thin film defect detection module in Example 1; Figure 3 The front side of the original stretching device in Example 1 ( Figure 3 (a) and side structure diagram ( Figure 3 (b)); Figure 4 The calibration platform of Example 1 is used for the calibration spectrum of the photothermal deflection signal; Figure 5 The calibration spectrum of the detector base in Example 1 for deflection spot self-alignment and tracking; Figure 6 The image shows the in-situ tensile defect test spectrum of the ITIC organic semiconductor thin film in Example 1.

[0022] Legend: 1. Pump light source; 2. Beam splitter; 3. Collimating and focusing lens group; 4. Chopper; 5. Thin film defect detection module; 51. Probe light receiver; 52. Detector base; 53. Calibration platform; 54. Tensioning device; 541. Upper slider; 542. Lower slider; 543. Threaded screw; 544. Scale; 55. Probe light generator; 56. Cuvette; 6. Photodiode; 7. Photometer; 8. Lock-in amplifier; 9. Data acquisition module. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0024] Example 1: like Figure 1 As shown, the spectral detection system for defects in flexible organic semiconductor thin films in this embodiment includes a pump light source 1, a beam splitter 2, a thin film defect detection module 5, a background spectral monitoring module, and a data acquisition module 9. The pump light source 1 is used to excite pump light. The beam splitter 2 is a beam splitter mirror, which is set in the optical path of the pump light to split the pump light into two paths, one of which enters the thin film defect detection module 5 and the other of which enters the background spectral monitoring module. The data acquisition module 9 is used to collect the photothermal deflection signal spectral data generated by the thin film defect detection module 5 and the background spectral data generated by the background spectral monitoring module. The beam splitter 2 and the thin film defect detection module 5 are sequentially provided with a collimating focusing lens group 3 and a chopper 4 along the direction of the pump light optical path.

[0025] like Figure 2 As shown, the thin film defect detection module 5 includes a probe light generator 55, a probe light receiver 51, a cuvette 56 for holding the test medium, and a stretching device 54 for stretching the flexible organic semiconductor thin film. The stretching device 54 is located inside the cuvette 56, and the stretching device 54 makes the center of the organic semiconductor thin film coincide with the optical path of the pump light, so that the pump light forms a refractive index gradient in the test medium around the center of the organic semiconductor thin film. The probe light generator 55 is used to emit probe light (parallel to the organic semiconductor thin film sample) that passes through the region around the center of the organic semiconductor thin film, and the probe light receiver 51 is used to receive the probe light after photothermal deflection, generating photothermal deflection signal spectral data. Figure 3 (a) and Figure 3As shown in (b), the stretching device 54 includes an upper slider 541, a lower slider 542, and a threaded screw 543. The upper slider 541 and the lower slider 542 move synchronously in opposite directions or in opposite directions by rotating the threaded screw 543. A scale 544 is provided next to the threaded screw 543. The stretching device 54 is mounted on the calibration platform 53 via a connecting rod. The calibration platform 53 is driven by a driver (a stepper motor with local displacement scanning, step size setting, and time delay control functions) to move in four directions (forward, backward, left, and right) and rotate around an axis in the horizontal direction. The sample position point corresponding to the maximum value of the deflection signal is determined by local displacement scanning, and the device automatically moves to that position after scanning is completed, thereby achieving automatic calibration of the phase matching position between the thin film sample and the probe beam. During in-situ tensile testing, although the pump light spot position remains constant, the film thickness change caused by mechanical stretching necessitates recalibrating the sample and probe laser positions to obtain the strongest photothermal deflection signal. The calibration platform 53 is controlled via software, controlling the X, Y, Z, and R axes, setting the zero displacement point, scanning range, and delay time. Simultaneously, the data acquisition module 9 is configured with the sampling number and output average. Based on the four-axis displacement coordinates and the photothermal deflection signal, the system generates a calibration spectrum (e.g., ...). Figure 4 As shown in the figure, the X-axis coordinate corresponding to the peak value of the Y-axis signal is the optimal sample position, which completes the automatic and accurate calibration of the sample and the probe beam.

[0026] The probe light receiver 51 is used to collect current data caused by the photothermal deflection beam. The probe light receiver 51 is connected to a gain-adjustable signal conversion circuit. The deflection voltage signal output by this circuit is connected to a lock-in amplifier 8 and then sent to the data acquisition module 9. The probe light receiver 51 is mounted on a detector base 52. Driven by a driver (a stepper motor with local displacement scanning, step size setting, and time delay control functions), the detector base 52 can move horizontally in four directions (forward, backward, left, and right), as well as rotate around its axis and adjust its pitch angle. Through software design, after the detector collects the photothermal deflection signal, combined with changes in the bias voltage, the bottom displacement platform can adjust its displacement in real time. It can also obtain the detector position point corresponding to the maximum value of the deflection signal through local displacement scanning, and automatically move to this optimal position after scanning, thereby achieving self-alignment and real-time tracking of the deflection spot. Changes in the sample position cause changes in the deflection displacement of the probe beam, requiring synchronous adjustment of the position of the probe light receiver 51 to achieve real-time tracking of the probe light spot. The five-degree-of-freedom detector base 52 is controlled by computer software, which sets the zero point of the X-axis displacement, scanning range, delay time, and the number of samples and average outputs of the data acquisition module 9. A calibration spectrum (such as...) is generated based on the X-axis displacement coordinates and photothermal deflection signal during the adjustment process. Figure 5As shown in the figure, the X-axis coordinate corresponding to the peak value of the photothermal deflection signal is the optimal position of the detection spot, thus completing the automatic and accurate tracking of the detection beam deflection spot.

[0027] The probe light generating device 55 is a helium-neon laser generator with a power of 1.5mW and a power stability of less than 2.5%.

[0028] The pump source 1 includes a xenon lamp, a monochromator, and a high-pass filter wheel arranged in sequence. The wavelength range of the excitation light output by the pump source 1 is 250–2500 nm, and the wavelength resolution is 1–20 nm.

[0029] The background spectrum monitoring module includes a collimating focusing lens, a photodiode 6, and a photometer 7 arranged sequentially along the optical path of the pump light. The pump light after beam splitting is focused onto the photodiode 6 by the collimating focusing lens group 3 for background signal detection. The photodiode 6 is a thermal probe with active thermal background compensation function, which can achieve high-resolution, low-drift, low-power optical signal detection in the 190nm to 2500nm wavelength range. The photodiode 6 is connected to the photometer 7, and the photometer 7 is connected to the data acquisition module 9 for real-time acquisition and display of optical power data corresponding to different wavelengths, and for plotting real-time spectrum graphs.

[0030] The entire testing system is housed in a sealed enclosure with a black exterior and sound-absorbing material inside to shield against ambient light and noise interference. The enclosure is mounted on a pendulum-type air-float platform to reduce the impact of environmental vibrations on the system.

[0031] The method for detecting defects in flexible organic semiconductor thin films in this embodiment is implemented using the detection system of this embodiment and includes the following steps: S1. Install the sample of the flexible organic semiconductor film in the stretching device 54 of the film defect detection module 5, adjust the position of the stretching device 54, fill the cuvette 56 with the test medium, and stretch the flexible organic semiconductor film. S2. Perform parameterized control on the monochromator, set the wavelength scanning range, switching delay time and wavelength resolution according to the optical characteristics of the thin film sample to be tested, achieve high-precision wavelength tuning and excitation light output, and turn on the pump light source 1 and the probe light generator 55. S3. The excitation light generated by pump source 1 is split by a beam splitter (the beam splitting flux ratio of the beam splitter is 99:1 for the thin film defect detection module 5 and the background spectrum detection module). One path is shaped by collimating and focusing lens group 3, and then periodically modulated by chopper 4 (chopper 4 modulates the continuous pump light into a periodic pulse signal, and its frequency is used as a reference signal input to lock-in amplifier 8 for synchronous extraction of photothermal deflection response signal). The light is then focused into thin film defect detection module 5, forming a refractive index gradient in the test medium around the center of the organic semiconductor thin film, and the probe light generating device... The probe light generated by 55 passes through the test medium with a refractive index gradient and undergoes photothermal deflection. It is then received by the probe light receiving device 51 to obtain the photothermal deflection signal spectral data. The excitation light generated by the pump light source 1 goes to the background spectrum monitoring module. By selecting the target scanning band, the background spectrum data is collected. Finally, the computer outputs the wavelength-optical power relationship graph (and background spectrum) to provide a benchmark for subsequent photothermal deflection signal normalization and quantitative analysis. The organic semiconductor thin film is stretched in situ at different ratios, the stretching amplitude is recorded, and the corresponding photothermal deflection signal data is repeatedly collected. S4. Combining the photothermal deflection signal spectral data with the background spectrum, the photothermal deflection spectrum measures the power of the sample's absorbed light converted into heat, thus causing a change in the refractive index gradient of the probe medium. The signal intensity S(E) is normalized with the known ultraviolet-visible absorption region to obtain the absorbance data A(E). When the thickness of the film to be measured is known as d, according to the Tauc model... Calculate the absorption coefficient of the thin film at different photon energies E. Based on the absorption coefficient data of the thin film, the Urbach energy of the thin film was calculated using the Urbach model. By varying the stretching amount of the organic thin film using a stretching sample stage, the Urbach energy under different stretching states was measured. The level of Urbach energy corresponds to the size of shallow-level defects in the organic thin film, and a curve showing the relationship between the stretching degree and the Urbach energy was plotted (e.g., Figure 5 As shown in the figure, this enables a quantitative evaluation of the degree of defects in the in-situ stretched state of the film.

[0032] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

[0033] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A spectroscopic detection system for defects in flexible organic semiconductor thin films, characterized in that, The system includes a pump light source (1), a beam splitter (2), a thin film defect detection module (5), a background spectrum monitoring module, and a data acquisition module (9). The pump light source (1) is used to excite pump light. The beam splitter (2) is set in the optical path of the pump light to split the pump light into two paths, one of which enters the thin film defect detection module (5) and the other enters the background spectrum monitoring module. The data acquisition module is used to collect the photothermal deflection signal spectral data generated by the thin film defect detection module (5) and the background spectrum data generated by the background spectrum monitoring module. The thin film defect detection module (5) includes a probe light generator (55), a probe light receiver (51), a cuvette (56) for holding the test medium, and a stretching device (54) for stretching the flexible organic semiconductor thin film. The stretching device (54) is located inside the cuvette (56), and the stretching device (54) makes the center of the organic semiconductor thin film coincide with the optical path of the pump light, so that the pump light forms a refractive index gradient in the test medium around the center of the organic semiconductor thin film. The probe light generator (55) is used to emit probe light that passes through the area around the center of the organic semiconductor thin film, and the probe light receiver (51) is used to receive the probe light after photothermal deflection and generate photothermal deflection signal spectral data.

2. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to claim 1, characterized in that, The tensioning device (54) is installed on the calibration platform. The tensioning device (54) includes an upper slider (541), a lower slider (542) and a threaded screw (543). The upper slider (541) and the lower slider (542) move synchronously in opposite directions or in opposite directions by rotating the threaded screw (543).

3. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to claim 2, characterized in that, A scale (544) is provided next to the threaded screw (543).

4. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to claim 2, characterized in that, The stretching device (54) is mounted on the calibration platform (53) via a connecting rod. The calibration platform (53) is driven by a driver to move in four directions (forward, backward, left, and right) and rotate around an axis in the horizontal direction.

5. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to claim 1, characterized in that, The detection light receiving device (51) is mounted on the detector base (52). The detector base (52) is driven by a driver to move in four directions in the horizontal direction (forward, backward, left, and right), as well as rotate around the axis and adjust the pitch angle.

6. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to any one of claims 1-5, characterized in that, A collimating focusing lens (3) and a chopper (4) are sequentially arranged between the beam splitter (2) and the thin film defect detection module (5) along the optical path of the pump light.

7. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to any one of claims 1-5, characterized in that, The detection light generating device (55) is a helium-neon laser generator with a power of 1.5~2mW and a power stability of less than 2.5%.

8. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to any one of claims 1-5, characterized in that, The pump light source (1) includes a xenon lamp and a monochromator arranged in sequence. The wavelength range of the excitation light output by the pump light source (1) is 250~2500nm and the wavelength resolution is 1~20nm.

9. The spectroscopic detection system for defects in flexible organic semiconductor thin films according to any one of claims 1-5, characterized in that, The background spectrum monitoring module includes a collimating focusing lens (3), a photodiode (6), and a photometer (7) arranged sequentially along the optical path of the pump light.

10. A method for detecting defects in flexible organic semiconductor thin films, characterized in that, The implementation using the spectroscopic detection system for defects in flexible organic semiconductor thin films according to any one of claims 1-9 includes the following steps: S1. Install the sample of the flexible organic semiconductor film in the stretching device (54) of the film defect detection module (5), adjust the position of the stretching device (54), and after filling the test medium in the cuvette (56), stretch the flexible organic semiconductor film. S2. After setting the parameters of the pump light source (1) according to the properties of the sample, turn on the pump light source (1) and the probe light generator (55). S3. The excitation light generated by the pump light source (1) goes to the thin film defect detection module (5) and forms a refractive index gradient in the test medium around the center of the organic semiconductor thin film. The probe light generated by the probe light generator (55) passes through the test medium with the refractive index gradient and undergoes photothermal deflection. It is then received by the probe light receiver (51) to obtain the photothermal deflection signal spectral data. The excitation light generated by the pump light source (1) goes to the background spectrum monitoring module to obtain the background spectrum data. S4. Combining the photothermal deflection signal and the background spectrum, the absorption coefficient of the thin film is calculated using the Tauc model. Based on the absorption coefficient data of the thin film, the Urbach energy of the thin film is calculated using the Urbach model, thereby realizing a quantitative evaluation of the degree of defects in the thin film.

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