Organic photovoltaic donor and receptor compatibility detection method based on terahertz emission spectrum

Abstract

The invention discloses an organic photovoltaic donor and receptor compatibility detection method based on terahertz emission signal intensity. The method comprises the following steps: S1, preparing a PM6: Y6 bulk heterojunction film of an organic photovoltaic material; s2, testing the steady-state absorption spectrum of each film sample, selecting wavelength light corresponding to an absorption peak to excite the sample, and respectively adopting light with the wavelengths of 550 nm and 750 nm to excite a donor-acceptor blended film (PM6: Y6), light with the wavelength of 550 nm to excite a pure donor film (PM6) and a pure acceptor film (Y6) with the wavelength of 750 nm; s3, collecting a terahertz wave signal emitted by the sample through the terahertz emission spectrum, changing a time delay line of a terahertz emission spectrum system, collecting a time-domain spectrum waveform of the terahertz wave field intensity emitted by the sample, taking the time delay line scanned at a place without the terahertz wave signal as background noise, taking a peak value of the time-domain spectrum waveform from which the background noise is deducted, and calculating the terahertz wave intensity of the sample; and taking the peak value as the terahertz signal intensity emitted by the sample, and judging the donor-receptor compatibility degree according to the signal intensity difference.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic solar cells and terahertz science and technology, and particularly relates to an organic photovoltaic donor-acceptor compatibility detection method based on terahertz emission spectroscopy. BACKGROUND

[0002] In recent years, organic solar cells have become a research hotspot in the photovoltaic field due to their low-cost solution processing technology, lightweight flexibility and other advantages. Organic solar cells are a kind of device that realizes the conversion of light energy into electrical energy by taking organic semiconducting materials such as polymers and small molecules as the core. Compared with traditional silicon-based solar cells, it has the advantages of flexibility, lightness, solution processing, low cost, etc., and its highest photoelectric conversion efficiency PCE has exceeded 19%, but the highest photoelectric conversion efficiency PCE and stability still need to be improved. The rapid development of organic solar cells benefits from the innovation of donor-acceptor materials, interface engineering and device structure optimization. At present, the light-absorbing layer of high-efficiency organic solar cells is mainly a bulk heterojunction formed by organic materials. The energy level, morphology and other properties of the donor-acceptor in the bulk heterojunction have a direct impact on the generation, recombination and transport process of photo-generated carriers, thus directly determining the photoelectric performance of the battery device. In the prior art, strategies such as developing new structures of donor-acceptor materials and controlling the morphology of the active layer are used to improve the photoelectric performance of the organic materials in the light-absorbing layer. However, there is a lack of direct characterization means for the carrier dynamics process in the organic materials in the light-absorbing layer of organic solar cells, especially the exciton separation process, which makes it impossible to directly and efficiently judge the pros and cons of the photoelectric performance of the materials.

[0003] In the prior art, the transient absorption spectroscopy technology uses pump-probe technology to monitor the excited state dynamics. The partial band spectral feature signals of the donor-acceptor material overlap, which limits the resolution accuracy. The energy transfer and charge transfer process and the structure-activity relationship of the donor-acceptor interface are not clear. The dynamic characteristics of the vertical direction interface carrier transport lack direct observation means. The exciton dissociation process can only be indirectly inferred by the signal decay rate. It is difficult to distinguish the interface charge transfer and the bulk recombination process. The time resolution is limited. The time-resolved fluorescence spectrum monitors the fluorescence intensity or lifetime change, but it indirectly judges the exciton separation by relying on the fluorescence quenching phenomenon. The time resolution is insufficient, and it cannot quantitatively characterize the charge separation efficiency.

[0004] Therefore, how to directly characterize in the exciton separation process, realize the detection of the carrier dynamics of the light-absorbing layer of the organic solar cell, realize the direct observation of the exciton separation process and judge the photoelectric performance of the organic photovoltaic material is a technical problem to be solved by those skilled in the art. SUMMARY

[0005] The purpose of the present application is to provide an organic photovoltaic donor-acceptor compatibility detection method based on terahertz emission spectroscopy to solve the problems in the prior art.

[0006] To this end, the above object of the present application is achieved by the following technical solutions:

[0007] The organic photovoltaic donor-acceptor compatibility detection method based on terahertz emission spectrum comprises the following steps:

[0008] S1, preparing PM6:Y6 bulk heterojunction films, pure donor films (PM6) and pure acceptor films (Y6) with the same thickness;

[0009] S2, testing the steady-state absorption spectra of the PM6:Y6 bulk heterojunction films, the pure donor films (PM6) and the pure acceptor films (Y6), selecting 550 nm and 750 nm as the excitation light according to the absorption peak position, respectively, and using 550 nm and 750 nm light to excite the PM6:Y6 bulk heterojunction films, respectively, using 550 nm light to excite the pure donor films (PM6), and using 750 nm light to excite the pure acceptor films (Y6);

[0010] S3, obtaining the terahertz time-domain waveform by changing the time delay line through the free-space electro-optical sampling method, and obtaining the peak field strength E _THz quantifying the signal intensity, wherein E _THz ∝dJ / dt, J is the transient photocurrent, and dJ / dt is the time derivative of the transient photocurrent, and E _THz The signal intensity is directly used as the compatibility judgment basis.

[0011] While the above technical solutions are adopted, the present application can also adopt or combine the following technical solutions:

[0012] As a preferred technical solution of the present application: in step S1, the preparation method of the PM6:Y6 bulk heterojunction film is as follows: PM6 and Y6 are mixed in a mass ratio of 1:1.2, a blended solution with a concentration of 12 mg / ml is prepared with chloroform as the solvent, the solution is stirred at room temperature in an inert atmosphere glove box for 12 hours, and then a donor-acceptor blended film is formed on a quartz substrate by spin coating at a speed of 4000 rpm for 30 seconds.

[0013] As a preferred technical solution of the present application: the PM6:Y6 bulk heterojunction film is spin-coated on a quartz substrate.

[0014] As a preferred technical solution of the present application: in step S1, the preparation method of the pure donor film (PM6) and the pure acceptor film (Y6) is as follows: PM6 and Y6 chloroform solutions are prepared with a concentration of 10 mg / ml, and the films are formed by using the same spin coating parameters as the PM6:Y6 bulk heterojunction film, so as to ensure the consistency of the film thickness.

[0015] As a preferred technical scheme of the present application: in step S2, the pump light is incident from the side of the quartz substrate at an incident angle of θ=45° to obtain the terahertz emission spectrum emitted from the side of the PM6:Y6 bulk heterojunction film.

[0016] As a preferred technical scheme of the present application: in step S3, the terahertz wave signal emitted by the sample is collected by the terahertz emission spectrum, the detection of the terahertz wave adopts a free-space electro-optical sampling method, the time-domain spectral waveform of the field intensity of the terahertz wave emitted by the sample is collected by changing the time delay line of the terahertz emission spectrum system, the peak value of the time-domain spectral waveform after deducting the background noise is taken as the terahertz signal intensity emitted by the sample, the terahertz signal emitted by the sample is derived from the transient photocurrent, the transient photocurrent J is formed by the photo-generated carriers generated by light excitation, the acceptor compatibility degree determines the intensity of the transient photocurrent formed by the photo-generated carriers, thereby determining the intensity of the terahertz signal emitted by the sample, and the acceptor compatibility degree can be judged according to the signal intensity difference.

[0017] Compared with the prior art, the organic photovoltaic acceptor compatibility detection method based on the terahertz emission spectrum has novelty. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the terahertz emission spectrum test;

[0019] Figure 2 It is the terahertz emission signal of the PM6:Y6 bulk heterojunction film sample;

[0020] Figure 3 It is the terahertz emission signal of the pure PM6 film sample;

[0021] Figure 4 It is the terahertz emission signal of the pure Y6 film sample. DETAILED DESCRIPTION

[0022] The present application will be further described in detail with reference to the drawings and specific examples.

[0023] The organic photovoltaic acceptor compatibility detection method based on the terahertz emission spectrum provided by the present application comprises the following steps:

[0024] Step one: taking quartz as a substrate, preparing a PM6:Y6 bulk heterojunction film, a pure PM6 film and a pure Y6 film. In the PM6:Y6 bulk heterojunction film, the acceptor materials PM6 and Y6 are weighed according to a mass ratio of 1:1.2, chloroform is used as a solvent for dissolution, and a PM6:Y6 bulk heterojunction film with a concentration of 12 mg / ml is prepared. -1blended solution, stirring at room temperature for 12 hours in a glove box, and then spin-coating the solution on a quartz substrate at a rotation speed of 4000 rpm for 30 s. For the pure PM6 film and the pure Y6 film, chloroform solutions with a concentration of 10 mg ml-1 were prepared using the same procedure. -1 The same procedure was used to prepare the chloroform solution with a concentration of 10 mg ml-1.

[0025] The method for preparing the PM6:Y6 bulk heterojunction film in the present application is described in the article entitled "Morphology Optimization of Nonhalogenated Twisty Volatile Solid Additives for High- Efficiency Organic Solar Cells", which is published in the journal Small, Volume 20, Article 2408610, 2024.

[0026] Step two: test the steady-state absorption spectrum of the film, select the wavelength of light with strong absorption to excite the sample, collect the terahertz waves emitted by the sample through terahertz emission spectroscopy, process the data, and then compare the size of the terahertz wave signals emitted by the sample to determine the performance of the organic photovoltaic material.

[0027] Terahertz emission spectroscopy (TES) is a technique for analyzing the physical properties of materials by detecting the terahertz radiation (0.1-10 THz) generated by the materials after excitation. It is based on optical nonlinear effects such as optical rectification, optical drag effect, spin-charge conversion process, or transient photocurrent, providing a unique perspective for studying the photoelectric response, carrier dynamics, and interface effects of materials. Terahertz emission spectroscopy has high resolution and transient nature, with a time resolution of picoseconds, making it suitable for capturing ultrafast physical processes such as carrier relaxation and spin dynamics. Due to its unique advantages, terahertz emission spectroscopy has become an important tool for frontier materials research and practical applications.

[0028] Examples

[0029] PM6:Y6 bulk heterojunction film detection

[0030] Step one: clean the quartz substrate, place the quartz substrate in an ultrasonic cleaning tank and clean it according to the following order: place the substrate in deionized water and add glass cleaner for ultrasonic cleaning for 10 minutes; then clean with deionized water for 10 minutes. After cleaning, place the quartz substrate in clean acetone and ultrasonically clean for 20 minutes; finally, place the substrate cleaned with acetone in isopropanol and clean for 15 minutes. Before use, transfer the quartz substrate to a plasma cleaner and process for 3 minutes.

[0031] Step two: for the PM6:Y6 bulk heterojunction film, first weigh the acceptor material in a glass bottle according to a mass ratio of 1:1.2, and dissolve it with chloroform as the solvent to prepare a solution with a concentration of 12 mg ml-1. -1blended solution. The prepared blended solution needs to be stirred at room temperature for 12 hours in the glove box, and then the solution is spin-coated on the quartz substrate in the glove box, the rotation speed of the spin coater is 4000 rpm, and the duration is 30 s. For the pure PM6 film and the pure Y6 film, in order to ensure the same thickness as the blended film, chloroform solutions with a concentration of 10 mg ml -1 The same procedure is used to prepare the chloroform solution.

[0032] Step three: Place the PM6:Y6 bulk heterojunction film sample spin-coated on the quartz substrate obtained in step two on the sample holder, adjust the angle of the sample holder so that the pump light is incident on the sample from the quartz side at θ = 45°. The terahertz emission spectrum of the PM6:Y6 bulk heterojunction film sample can be obtained.

[0033] Pure PM6 film detection

[0034] Replace the PM6:Y6 blended solution with a concentration of 12 mg ml -1 in step two of Example 1 with a PM6 solution with a concentration of 10 mg ml -1 . The pure PM6 film sample can be obtained. Replace the PM6:Y6 bulk heterojunction film sample in step three of Example 1 with the pure PM6 film sample. The terahertz emission signal of the pure PM6 film sample can be obtained, as shown in Figure 3 .

[0035] Pure Y6 film detection

[0036] Replace the PM6:Y6 blended solution with a concentration of 12 mg ml -1 in step two of Example 1 with a Y6 solution with a concentration of 10 mg ml -1 . The pure Y6 film sample can be obtained. Replace the PM6:Y6 bulk heterojunction film sample in step three of Example 1 with the pure Y6 film sample. The terahertz emission signal of the pure Y6 film sample can be obtained, as shown in Figure 4 .

[0037] Experimental results: The PM6:Y6 bulk heterojunction film sample spin-coated on the quartz substrate is tested by terahertz emission spectrum (TES), as shown in Figure 1 , it can be seen that the terahertz emission signal of the PM6:Y6 bulk heterojunction film sample is as shown in Figure 2 .

[0038] Figure 2 The terahertz emission signals of the PM6:Y6 bulk heterojunction film sample at wavelengths of 550 nm and 750 nm excitation, respectively, the terahertz signal is detected when the light excitation is 550 nm, while the terahertz signal is not detected when the light excitation is 750 nm, and the Figure 3When the pure Y6 film was excited by 750 nm light, no terahertz signal was detected, so it can be considered that the signal is related to the excitation of the PM6 donor, Figure 4 No terahertz signal was detected for the pure PM6 film excited by 550 nm light, which excludes the possibility that PM6 emits terahertz signals alone, so it can be considered that the terahertz signal emitted by the PM6:Y6 bulk heterojunction film sample is related to the existence of the bulk heterojunction interface in the sample, and is derived from the donor-acceptor interaction. No terahertz signal was detected in the reference sample, indicating that no transient photocurrent J was formed. When the mixed film sample was excited by 550 nm light, a strong terahertz signal intensity was detected, indicating that electron transfer occurred on the bulk heterojunction interface to generate a strong transient photocurrent, indicating that the compatibility of the donor and the acceptor is good.

[0039] The above specific embodiments are used to explain and illustrate the present application, and are only preferred embodiments of the present application, rather than limiting the present application. Any modification, equivalent replacement, improvement, etc. made to the present application within the spirit of the present application and the protection scope of the claims falls within the protection scope of the present application.

Claims

1. A method for detecting the compatibility of organic photovoltaic donors and acceptors based on terahertz emission spectroscopy, comprising the following steps: S1, Prepare PM6:Y6 bulk heterojunction films, pure donor films (PM6) and pure acceptor films (Y6) with the same thickness. S2. The steady-state absorption spectra of PM6:Y6 bulk heterojunction film, pure donor film (PM6) and pure acceptor film (Y6) were tested. According to the position of the absorption peak, wavelengths of 550 nm and 750 nm were selected as excitation light. PM6:Y6 bulk heterojunction film was excited by light of 550 nm and 750 nm respectively. Pure donor film (PM6) was excited by light of 550 nm and pure acceptor film (Y6) was excited by light of 750 nm. S3, using free-space electro-optic sampling, changes the time delay line to obtain the terahertz time-domain waveform, and after subtracting background noise, the peak field strength E is used as the final waveform. _THz Quantize the signal strength, where E _THz ∝dJ / dt, where J is the transient photocurrent, dJ / dt refers to the time derivative of the transient photocurrent, and E _THz Signal strength is directly used as the basis for compatibility judgment.

2. The method for detecting the compatibility of organic photovoltaic donors and acceptors based on terahertz emission spectroscopy as described in claim 1, characterized in that: In step S1, the PM6:Y6 bulk heterojunction film is prepared by mixing PM6 and Y6 at a mass ratio of 1:1.2, preparing a blend solution with a concentration of 12 mg / ml using chloroform as a solvent, stirring at room temperature in an inert atmosphere glove box for 12 hours, and then spin-coating on a quartz substrate at 4000 rpm for 30 seconds to form a donor-acceptor blend film.

3. The method for detecting the compatibility of organic photovoltaic donors and acceptors based on terahertz emission spectroscopy as described in claim 1, characterized in that: In step S1, the PM6:Y6 bulk heterojunction thin film is spin-coated onto a quartz substrate.

4. The method for detecting the compatibility of organic photovoltaic donors and acceptors based on terahertz emission spectroscopy as described in claim 1, characterized in that: In step S1, the pure donor film (PM6) and the pure acceptor film (Y6) are prepared by: preparing chloroform solutions of PM6 and Y6 at a concentration of 10 mg / ml, respectively, and forming films using the same spin-coating parameters as the PM6:Y6 bulk heterojunction film to ensure consistent film thickness.

5. The method for detecting the compatibility of organic photovoltaic donors and acceptors based on terahertz emission spectroscopy as described in claim 3, characterized in that: In step S2, the pump light is incident from one side of the quartz substrate at an incident angle of θ=45° to obtain the terahertz emission spectrum emitted from one side of the PM6:Y6 bulk heterojunction thin film.

6. The method for detecting the compatibility of organic photovoltaic donors and acceptors based on terahertz emission spectroscopy as described in claim 1, characterized in that: In step S3, the terahertz wave signal emitted by the sample is acquired by terahertz emission spectroscopy. The terahertz wave is detected by free-space electro-optic sampling. By changing the time delay line of the terahertz emission spectroscopy system, the time-domain spectrum waveform of the terahertz wave field intensity emitted by the sample is acquired. The time delay line scanned at the point where there is no terahertz wave signal is taken as the background noise. The peak value of the time-domain spectrum waveform after deducting the background noise is taken as the intensity of the terahertz signal emitted by the sample. The terahertz signal emitted by the sample originates from the transient photocurrent. The transient photocurrent J is formed by photogenerated carriers generated by photoexcitation. The degree of donor-acceptor compatibility determines the intensity of the transient photocurrent formed by photogenerated carriers, thereby determining the intensity of the terahertz signal emitted by the sample. The degree of donor-acceptor compatibility can be judged based on the difference in signal intensity.

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