Organic micro-nano eutectic crystal, preparation method thereof and application thereof in near-infrared light absorbing material

Abstract

This invention discloses an organic micro / nano cocrystal, its preparation method, and its application in near-infrared light absorption materials. The organic micro / nano cocrystal is formed by the self-assembly of donor and acceptor molecules. The preparation method includes the following steps: (1) dissolving the donor and acceptor molecules in a good organic solvent to obtain a homogeneous solution; (2) adding a poor organic solvent to the homogeneous solution prepared in step (1) and mixing thoroughly; then dropping the mixed liquid onto a substrate and allowing the solvent to evaporate to obtain the organic micro / nano cocrystal. This invention prepares the above-mentioned organic micro / nano cocrystal using a simple solution method. The preparation method is simple and reproducible, and the obtained cocrystal has high crystallinity and low defect density. This organic micro / nano cocrystal possesses near-infrared light absorption and photoelectric conversion capabilities. By adjusting the types of donor and acceptor molecules, the cocrystal can absorb near-infrared light in different wavelength ranges from 740nm to 2500nm, showing promising application prospects in near-infrared photodetectors.

Description

Technical Field

[0001] This invention relates to the field of organic optoelectronic materials technology, specifically to an organic micro / nano eutectic, its preparation method, and its application in near-infrared light absorbing materials. Background Technology

[0002] Photodetectors, as highly efficient photoelectric conversion devices, possess immense potential and have achieved significant progress in fields such as artificial intelligence, optical communication, and biological imaging. They play a crucial role in advancing optoelectronic information technology platforms by controlling and understanding related structure-property relationships and device engineering. Organic photoresponsive materials have attracted widespread attention due to their low cost, ease of large-scale preparation, solution processability, biocompatibility, and customizable photoelectric properties. Furthermore, unlike other solution-processable materials such as quantum dots and mixed-metal perovskites, organic semiconductor materials are free of heavy metal toxicity, environmentally friendly, and safe for use in photodetectors, thus contributing positively to promoting green and sustainable development. These data also indicate that organic photoresponsive materials can be strong candidates for the next generation of photosensitive materials.

[0003] One of the major challenges facing high-sensitivity broadband photodetectors is the design and synthesis of active organic materials with near-infrared absorption and photoresponse. Among emerging organic photoactive materials, research has primarily focused on organic dyes, rare-earth metal coordination compounds, and polymers. These materials exhibit inherently soft, lightweight, and tunable photoelectric properties, and through molecular structure design, they possess characteristics such as flexibility, low cost, and large-scale production capabilities. Furthermore, organic near-infrared photodetectors without cooling systems can be applied to future wearable electronics for real-time health monitoring. For example, Chou and colleagues fabricated high-performance OLED devices using novel Pt(II) complexes, which exhibited significant near-infrared emission characteristics above 930 nm, with a maximum external quantum efficiency of 4.31% (Nat. Photonics 2020, 14, 570). In addition, near-infrared absorbing materials may also possess organic thermally activated delayed fluorescence (TADF) properties, exhibiting long lifetimes and biocompatibility, showing great promise for applications in bioimaging. Researchers have also been able to achieve near-infrared performance in polymers through strategies such as increasing conjugation length, reducing bond length, and enhancing matrix rigidity.

[0004] On the other hand, small-molecule semiconductors with well-defined structures are also a promising class of materials for manufacturing commercially available high-sensitivity organic photodetectors. Currently, the acceptor-donor-acceptor (ADA) concept has proven to be one of the most effective molecular design strategies for constructing small-molecule semiconductors with tunable band gaps, where their molecular orbitals are formed through the hybridization of electron-donating "D" segments and electron-withdrawing "A" segments of original non-interacting orbitals. However, some drawbacks exist in organic active materials that can currently achieve near-infrared photodetection. For polymers, the unavoidable large structural disorder during preparation and the poor batch-to-batch reproducibility of polymer quality (e.g., molecular weight and polymer dispersion index) hinder the development of polymer optoelectronic devices that rely on near-infrared absorption. For small organic molecules, it has been difficult to achieve continuous redshifts by primitively tuning the molecular backbone or chromophore function, especially in the study of near-infrared emission systems in the near-infrared II region and communication bands.

[0005] Therefore, it is extremely important to develop a simple and universal method to extend the application of organic near-infrared materials to optoelectronic devices that rely on near-infrared absorption. Summary of the Invention

[0006] This invention provides an organic micro / nano cocrystal, its preparation method, and its application in near-infrared light absorption materials. The organic micro / nano cocrystal is prepared by a simple solution method. This organic micro / nano cocrystal has near-infrared light absorption and photoelectric conversion capabilities. Furthermore, by adjusting the types of donor and acceptor molecules, the cocrystal can absorb near-infrared light in different wavelength ranges from 740nm to 2500nm, showing good application potential in near-infrared photodetectors.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] The first aspect of this invention provides an organic micro / nano cocrystal, which is formed by the self-assembly of organic donor molecules and organic acceptor molecules;

[0009] The organic donor molecule is selected from benzo[1,2-b:5,4-b']dithiophene, naphtho[1,2-b:5,6-b']dithiophene, alpha-terthiophene, 2,5-dibromodithiophene[3,2-b:2',3'-d]thiophene, benzo[b]benzo[4,5]thieno[2,3-d]thiophene, thieno[3,2-f:4,5-f]di[1]benzothiophene, bisnaphtho[2,3- One of the following: b:2',3'-f]thiophene[3,2-b]thiophene, benzo[1,2-b:5,4-b']dithiophene, 2',3'-d-dithiophene, naphtho[2,3-b]thiophene, benzotrithiophene, 7h-benzo[c]carbazole, 2,5-bis(thiophene-2-yl)thiophene[3,2-b]thiophene, and 2,6-bis(thiophene-2-yl)dithiophene[3,2-b:2',3'-d]thiophene;

[0010] The organic acceptor molecule is selected from 7,7,8,8-tetracyano-p-benzoquinone dimethane, 2-fluoro-7,7,8,8-tetracyanoquinone dimethane, 2,5-difluoro-7,7,8,8-tetracyanoquinone dimethane, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone, 11,11,12,12-tetracyanonaphthalene-2,6-quinolinemethane, 2, One of 2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile, 2,2'-(benzo[1,2-b:4,5-b']dithiophene-4,8-diylidene)dimalononitrile, 2,5-dimethyl-7,7,8,8-tetracyanoquinone dimethylane, N,N'-(2,5-dimethyl-2,5-cyclohexadiene-1,4-diylidene)dicyanamide, and tetracyanoethylene.

[0011] Furthermore, the organic micro / nano eutectic can be formed by the self-assembly of organic donor molecules and organic acceptor molecules in any molar ratio.

[0012] The second aspect of this invention provides a method for preparing the organic micro / nano eutectic described in the first aspect, comprising the following steps:

[0013] (1) Dissolve organic donor molecules and organic acceptor molecules in a good organic solvent to obtain a homogeneous solution;

[0014] (2) Take a small amount of the homogeneous solution prepared in step (1) and drop it onto the substrate. After the solvent evaporates, organic micro-nano eutectic is obtained; or add a poor organic solvent to the homogeneous solution prepared in step (1) and mix evenly. Take a small amount of the mixed liquid and drop it onto the substrate. After the solvent evaporates, organic micro-nano eutectic is obtained.

[0015] The organic donor molecule is selected from benzo[1,2-b:5,4-b']dithiophene, naphtho[1,2-b:5,6-b']dithiophene, alpha-terthiophene, 2,5-dibromodithiophene[3,2-b:2',3'-d]thiophene, benzo[b]benzo[4,5]thieno[2,3-d]thiophene, thieno[3,2-f:4,5-f]di[1]benzothiophene, and bisnaphtho[2,3-b:2'] One of the following: [3'-f]thiophene[3,2-b]thiophene, benzo[1,2-b:5,4-b']dithiophene, 2',3'-d-dithiophene, naphtho[2,3-b]thiophene, benzotrithiophene, 7h-benzo[c]carbazole, 2,5-bis(thiophene-2-yl)thiophene[3,2-b]thiophene, and 2,6-bis(thiophene-2-yl)dithiophene[3,2-b:2',3'-d]thiophene; the structure is shown below:

[0016]

[0017] The organic acceptor molecule is selected from 7,7,8,8-tetracyano-p-benzoquinone dimethyl ... One of the following: perfluoronaphthalene-2,6-diylidene dimalononitrile, 2,2'-(benzo[1,2-b:4,5-b']dithiophene-4,8-diylidene dimalononitrile, 2,5-dimethyl-7,7,8,8-tetracyanoquinone dimethane, N,N'-(2,5-dimethyl-2,5-cyclohexadiene-1,4-diylidene)dicyanamide, and tetracyanoethylene; the structure is shown below:

[0018]

[0019] In some preferred embodiments, the organic donor molecule is benzo[1,2-b:5,4-b']dithiophene or 2,5-bis(thiophen-2-yl)thiophene[3,2-b]thiophene, and the organic acceptor molecule is 2,5-difluoro-7,7,8,8-tetracyanoquinone dimethane, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone or 7,7,8,8-tetracyano-p-benzodiquinone dimethane.

[0020] Further, in step (1), the good organic solvent is preferably one or more of dichloromethane, trichloromethane, acetonitrile, toluene, tetrahydrofuran, and chlorobenzene.

[0021] Further, in step (1), the molar volume ratio of solute to solvent in the homogeneous solution is preferably 0.1-10 mmol / L, and the solute is an organic donor molecule and an organic acceptor molecule.

[0022] Furthermore, in step (1), if the organic donor small molecule and / or organic acceptor are not completely dissolved in the good solvent, the filtration process is performed before adding the poor solvent to remove the residual solid and avoid affecting the formation of the eutectic.

[0023] Further, in step (2), the undesirable organic solvent is preferably one or more of methanol, ethanol, cyclohexane, n-hexane, and isopropanol.

[0024] Furthermore, the volume ratio of the good solvent to the poor solvent is 1:0.1-10.

[0025] Furthermore, in step (2), it is preferable to evaporate the solvent at 10-40°C.

[0026] The third aspect of this invention provides an application of the organic micro / nano eutectic described in the first aspect in organic near-infrared light absorbing materials.

[0027] Furthermore, the organic nano-eutectic is used as an organic near-infrared light absorbing material in near-infrared photodetectors.

[0028] Furthermore, electrodes are fabricated on the surfaces at both ends of the organic micro / nano eutectic, and the surface of the organic micro / nano eutectic is irradiated with a near-infrared light source to be tested to collect photocurrent signals.

[0029] Furthermore, the wavelength of the near-infrared light is 740nm-2500nm.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention prepares organic micro / nano cocrystals from organic donor molecules and organic acceptor molecules using a simple solution method. The cocrystal contains two or more different molecules arranged regularly and closely in a crystal lattice. On the one hand, the crystal is not limited to a single molecule, which is beneficial for expanding the organic near-infrared system. On the other hand, the regularly arranged molecules can form an ordered conductive network, which is beneficial for carrier transport and promotes charge transfer. Moreover, the above method is simple to operate and has good repeatability. The prepared cocrystal has high crystallinity and low defect density, which can give full play to the advantages of single crystals and reduce charge loss during transfer.

[0032] 2. The present invention prepares organic micro / nano eutectic crystals using the above method. By selecting donor and acceptor molecules with different energy level structures, new excited states are generated in the eutectic crystal, resulting in a narrower optical band gap. This causes the absorption of the eutectic crystal to shift towards redder wavelengths. Therefore, the present invention can adjust the absorption of near-infrared light by adjusting the types of acceptor and donor molecules, extending from short-wave near-infrared to the near-infrared III region. This allows the eutectic crystal to absorb near-infrared light in different wavelength ranges from 740nm to 2500nm, showing promising application prospects in near-infrared photodetectors. Attached Figure Description

[0033] Figure 1 Microscopic image of the BDP-F2TCNQ eutectic prepared in Example 1;

[0034] Figure 2 The molecular packing mode in the BDP-F2TCNQ eutectic prepared in Example 1;

[0035] Figure 3 The XRD pattern of the BDP-F2TCNQ eutectic prepared in Example 1;

[0036] Figure 4 SEM image of the BDP-F2TCNQ eutectic prepared in Example 1;

[0037] Figure 5 AFM diagram of the BDP-F2TCNQ eutectic prepared in Example 1;

[0038] Figure 6 The absorption spectrum of the BDP-F2TCNQ eutectic prepared in Example 1;

[0039] Figure 7 An optical image of the BDP-F2TCNQ eutectic photodetector device prepared in Example 1;

[0040] Figure 8 The relationship between current density and incident light intensity of the BDP-F2TCNQ eutectic photodetector device prepared in Example 1 under 850nm wavelength illumination;

[0041] Figure 9 The responsivity (a) and specific detectivity (b) of the BDP-F2TCNQ eutectic photodetector device prepared in Example 1 at a wavelength of 850 nm as a function of incident light intensity;

[0042] Figure 10 Microscopic image of the BDP-F4TCNQ eutectic prepared in Example 2;

[0043] Figure 11 The absorption spectrum of the BDP-F4TCNQ eutectic prepared in Example 2;

[0044] Figure 12 The relationship between current density and incident light intensity of the BDP-F4TCNQ eutectic photodetector device prepared in Example 1 under 1064nm wavelength illumination;

[0045] Figure 13 The responsivity (a) and specific detectivity (b) of the BDP-F2TCNQ eutectic photodetector device prepared in Example 2 as a function of incident light intensity at a wavelength of 1064 nm.

[0046] Figure 14 Microscopic image of the DTTP-TCNQ eutectic prepared in Example 3;

[0047] Figure 15 The absorption spectrum of the DTTP-TCNQ eutectic prepared in Example 3;

[0048] Figure 16 The photocurrent of the DTTP-TCNQ eutectic photodetector device prepared in Example 3 under 1310nm wavelength illumination;

[0049] Figure 17 Microscopic image of the DTTP-F2TCNQ eutectic prepared in Example 4;

[0050] Figure 18 The absorption spectrum of the DTTP-F2TCNQ eutectic prepared in Example 4;

[0051] Figure 19 The relationship between current density and incident light intensity of the DTTP-F2TCNQ eutectic photodetector device prepared in Example 4 under 1550nm wavelength illumination;

[0052] Figure 20 Microscopic image of the eutectic prepared for Comparative Example 1. Detailed Implementation

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. "Comprising" or "containing" as used herein means that it may include or contain other components in addition to the stated components. "Comprising" or "containing" as used herein may also be replaced with the closed form "is" or "consisting of".

[0054] The present invention will be further described below with reference to specific embodiments and accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0055] Example 1

[0056] This embodiment provides a fabrication method for organic micro / nano BDP-F2TCNQ eutectic and BDP-F2TCNQ eutectic photodetector devices. The specific fabrication process is as follows:

[0057] (1) 1.9 mg of benzo[1,2-b:5,4-b']dithiophene (BDP) and 2.4 mg of 2,5-difluoro-7,7,8,8-tetracyanoquinone dimethane (F2TCNQ) were added to 4 mL of acetonitrile and sonicated for 5 min to obtain BDP-F2TCNQ acetonitrile stock solution;

[0058] (2) Take 2 mL of the stock solution and add it to 1 mL of ethanol and shake well. Take it out and drop it onto the substrate. Wait for the organic solvent to completely evaporate and dry to obtain a long BDP-F2TCNQ eutectic.

[0059] The BDP-F2TCNQ eutectic prepared in this embodiment is as follows: Figure 1 As shown, it exhibits a banded structure. In the co-crystal prepared in this embodiment, the donor and acceptor molecules are arranged in a face-to-face mixed packing pattern (e.g., Figure 2 As shown in the figure, the molecules are arranged more closely and orderly, which is conducive to the formation of an interpenetrating conductive network and promotes the transfer of charge carriers.

[0060] Figure 3 The XRD pattern of the BDP-F2TCNQ eutectic prepared in this embodiment shows that the diffraction peaks are narrow and have high intensity, which also indicates that the BDP-F2TCNQ eutectic prepared in this embodiment has good crystallinity.

[0061] Figure 4 , 5 The SEM and AFM images of the BDP-F2TCNQ eutectic prepared in this embodiment are shown below. Figure 4 It can be seen that the BDP-F2TCNQ eutectic surface prepared in this embodiment has no obvious defects; from Figure 5 As can be seen, the prepared eutectic is thin, only 80 nm thick, and has a surface roughness of 0.42 nm. The thin eutectic with a certain roughness is more conducive to contact with the electrode and promotes charge transport.

[0062] Figure 6 The figure shows the absorption spectrum of the BDP-F2TCNQ eutectic prepared in this embodiment. As can be seen from the figure, the eutectic has a relatively strong absorption signal in the near-infrared region.

[0063] Fabrication of BDP-F2TCNQ eutectic photodetector device:

[0064] In this embodiment, gold electrodes are fabricated at both ends of the BDP-F2TCNQ eutectic, resulting in the following: Figure 7 The eutectic photodetector device shown.

[0065] The photoelectric performance of the eutectic photodetector device prepared above was tested. Near-infrared light of different incident intensities at 850 nm was irradiated onto the eutectic, and its current density was measured. The results are as follows: Figure 8 As shown, the current density of the BDP-F2TCNQ eutectic photodetector increases linearly with increasing incident light intensity. Figure 9 As shown, through the formula R = (I light -I dark ) / PS calculation (where R is the photoresponsivity, I light For photocurrent, I dark (where P is the dark current, S is the incident light intensity, and S is the device area.) The responsivity of the BDP-F2TCNQ eutectic device can reach 375 A / W, and the specific detectivity can reach 2.27 × 10⁻⁶. 14 Jones.

[0066] Example 2

[0067] This embodiment provides a fabrication method for organic micro / nano BDP-F4TCNQ eutectic and BDP-F4TCNQ eutectic photodetector devices. The specific fabrication process is as follows:

[0068] (1) 1.9 mg of benzo[1,2-b:5,4-b']dithiophene (BDP) and 2.76 mg of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4TCNQ) were added to 4 mL of acetonitrile and sonicated for 5 min to obtain BDP-F4TCNQ acetonitrile stock solution;

[0069] (2) Take 1 mL of the stock solution and add it to 4 mL of ethanol and shake well. Take it out and drop it onto the substrate. Wait for the organic solvent to completely evaporate and dry to obtain a long BDP-F4TCNQ eutectic.

[0070] The BDP-F4TCNQ eutectic prepared in this embodiment is as follows: Figure 10 As shown, it exhibits a banded structure similar to the BDP-F2TCNQ eutectic prepared in Example 1.

[0071] Figure 11 The figure shows the absorption spectrum of the BDP-F4TCNQ eutectic prepared in this embodiment. As can be seen from the figure, the eutectic prepared in this embodiment has an absorption value at 1064 nm in the near-infrared II region.

[0072] Fabrication of BDP-F4TCNQ eutectic photodetector device:

[0073] In this embodiment, gold electrodes are fabricated at both ends of the BDP-F4TCNQ eutectic to obtain the BDP-F4TCNQ eutectic photodetector device.

[0074] The photoelectric performance of the prepared eutectic photodetector device was tested by irradiating the eutectic with near-infrared light of different incident intensities at 1064 nm and measuring its current density. The results are as follows: Figure 12 As shown, the current density of the BDP-F4TCNQ eutectic photodetector increases with increasing incident light intensity. Calculations using the formula show that the responsivity of the BDP-F4TCNQ eutectic device can reach 500 A / W, and the specific detectivity can reach 1.75 × 10⁻⁶. 14 Jones (as) Figure 13 (As shown).

[0075] Example 3

[0076] This embodiment provides a fabrication method for organic micro / nano DTTP-TCNQ eutectic and DTTP-TCNQ eutectic photodetector devices. The specific fabrication process is as follows:

[0077] (1) 3.05 mg of 2,5-bis(thiophen-2-yl)thiophene[3,2-B]thiophene (DTTP) and 2.04 mg of 7,7,8,8-tetracyano-p-benzoquinone dimethane (TCNQ) were added to 4 mL of dichloromethane and sonicated for 3 min to obtain a dichloromethane stock solution of DTTP-TCNQ;

[0078] (2) Take 2 mL of the stock solution and add it to 4 mL of ethanol and shake well. Take it out and drop it onto the substrate. Wait for the organic solvent to evaporate completely to obtain DTTP-TCNQ eutectic.

[0079] The DTTP-TCNQ eutectic prepared in this embodiment is as follows: Figure 14 As shown, it has a rod-like structure.

[0080] Figure 15 The figure shows the absorption spectrum of the DTTP-TCNQ eutectic prepared in this embodiment. As can be seen from the figure, the eutectic prepared in this embodiment has an absorption value at 1310 nm in the near-infrared II region.

[0081] Fabrication of DTTP-TCNQ eutectic photodetector devices:

[0082] In this embodiment, gold electrodes are fabricated at both ends of the DTTP-TCNQ eutectic to obtain a DTTP-TCNQ eutectic photodetector device.

[0083] The photoelectric performance of the eutectic photodetector device prepared above was tested, such as... Figure 16 As shown, the current of the eutectic photodetector device under no light source conditions and under 1310nm near-infrared light illumination is significantly different. According to the formula calculation, the responsivity of the DTTP-TCNQ eutectic device at a wavelength of 1310nm can reach 0.14A / W.

[0084] Example 4

[0085] This embodiment provides a fabrication method for organic micro / nano DTTP-F2TCNQ eutectic and DTTP-F2TCNQ eutectic photodetector devices. The specific fabrication process is as follows:

[0086] (1) 3.05 mg of 2,5-bis(thiophen-2-yl)thiophene[3,2-B]thiophene (DTTP) and 2.4 mg of 2,5-difluoro-7,7,8,8-tetracyanoquinone dimethane (F2TCNQ) were added to 4 mL of dichloromethane and sonicated for 10 min to obtain acetonitrile stock solution of DTTP-F2TCNQ;

[0087] (2) After the ultrasound is completed, the product is taken out and dropped onto the substrate. After the organic solvent has completely evaporated, the DTTP-F2TCNQ eutectic is obtained.

[0088] Figure 17 The image shows a microscopic image of the DTTP-F2TCNQ eutectic prepared in this embodiment. As can be seen from the image, the DTTP-F2TCNQ eutectic prepared in this embodiment has a rod-like structure.

[0089] Figure 18 The absorption spectrum of the DTTP-F2TCNQ eutectic prepared in this embodiment is shown in the figure. As can be seen from the figure, the eutectic prepared in this embodiment has an absorption value at 1550 nm in the near-infrared II region, and it can extend to 2000 nm.

[0090] Fabrication of DTTP-F2TCNQ eutectic photodetector device:

[0091] In this embodiment, gold electrodes are fabricated at both ends of the DTTP-F2TCNQ eutectic to obtain the DTTP-F2TCNQ eutectic photodetector device.

[0092] The photoelectric performance of the eutectic photodetector device prepared above was tested. Near-infrared light of different incident intensities at 1550 nm was irradiated onto the eutectic, and its current density was measured. The results are as follows: Figure 19 As shown, the current density of the DTTP-F2TCNQ eutectic photodetector increases linearly with the increase of incident light intensity. Calculations using the formula show that the responsivity of the DTTP-F2TCNQ eutectic device can reach 500 A / W.

[0093] Comparative Example 1

[0094] 1.9 mg of naphtho[1,2-b:5,6-b']dithiophene (NDP) and 2.45 mg of tetrachlorobenzoquinone were added to 4 mL of dichloromethane and sonicated for 5 min to obtain a dichloromethane stock solution containing the two components. After sonication, the solution was removed and dropped onto a substrate. After the organic solvent had completely evaporated, a eutectic was obtained.

[0095] The cocrystal formed by the above-mentioned organic donor and organic acceptor is as follows: Figure 20 As shown, the eutectic is linear and has an irregular morphology.

[0096] Comparative Example 2

[0097] 1.9 mg of naphtho[1,2-b:5,6-b']dithiophene (NDP) and 4.23 mg of tetrabromo-p-benzoquinone were added to 5 mL of dichloromethane and sonicated for 10 min to obtain a dichloromethane stock solution containing the two components. After sonication, the solution was removed and dropped onto a substrate. After the organic solvent had completely evaporated, a eutectic was obtained, but the eutectic morphology was irregular.

[0098] Comparative Example 3

[0099] 2.4 mg of benzo[b]benzo[4,5]thieno[2,3-d]thieno and 2.45 mg of tetrachlorobenzoquinone were added to 4 mL of dichloromethane and sonicated for 5 min to obtain a dichloromethane stock solution containing the two components. After sonication, the solution was removed and dropped onto a substrate. After the organic solvent had completely evaporated, a eutectic was obtained, but the eutectic morphology was irregular.

[0100] Comparative Example 4

[0101] 2.4 mg of benzo[b]benzo[4,5]thieno[2,3-d]thiophene and 2.27 mg of 2,3-dichloro-5,6-dicyanobenzoquinone were added to 5 mL of acetonitrile and sonicated for 10 min to obtain a stock solution of the two components in acetonitrile. After sonication, the solution was removed and dropped onto a substrate. After the organic solvent had completely evaporated, a eutectic was obtained, but the eutectic morphology was irregular.

[0102] Comparative Example 5

[0103] 2.82 mg of 1,4-bis(trans-2-phenylethyl)benzene and 2.4 mg of 2,5-difluoro-7,7,8,8-tetracyanoquinone dimethyl ether were added to 5 mL of acetonitrile and sonicated for 10 min to obtain an acetonitrile stock solution. After sonication, the solution was taken out and dropped onto a substrate. After the organic solvent had completely evaporated, a eutectic formed by the two components was obtained.

[0104] In summary, the types of organic donor and acceptor molecules affect the formation and morphology of eutectic. By using specific organic donor and acceptor molecules, regular ribbon or rod-shaped eutectic materials can be prepared. These eutectic materials have good photoelectric conversion performance and can be used to prepare eutectic photodetector devices.

[0105] The embodiments described above are merely preferred examples to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. Use of an organic micro-nano eutectic in an organic near-infrared light absorbing material, characterized in that, The organic micro / nano cocrystal is used as an organic near-infrared light absorbing material in near-infrared photodetectors; the organic micro / nano cocrystal is formed by the self-assembly of organic donor molecules and organic acceptor molecules. The organic donor molecule is benzo[1,2-b:5,4-b']dithiophene or 2,5-bis(thiophen-2-yl)thiophene[3,2-b]thiophene; The organic acceptor molecule is 2,5-difluoro-7,7,8,8-tetracyanoquinone dimethyl methyl methyl methyl benzoquinone or 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl p-benzoquinone. The preparation of the organic micro / nano eutectic includes the following steps: (1) Dissolve the organic donor molecule and the organic acceptor molecule in a good organic solvent to obtain a homogeneous solution; the good organic solvent is one or more of dichloromethane, trichloromethane, acetonitrile, toluene, tetrahydrofuran, and chlorobenzene; The homogeneous solution has a molar volume ratio of solute to good organic solvent of 0.1-10 mmol / L, and the solute is an organic donor molecule and an organic acceptor molecule. (2) Take a small amount of the homogeneous solution prepared in step (1) and drop it onto the substrate. After the solvent evaporates, organic micro-nano eutectic is obtained; or add a poor organic solvent to the homogeneous solution prepared in step (1) and mix evenly. Take a small amount of the mixed liquid and drop it onto the substrate. After the solvent evaporates, organic micro-nano eutectic is obtained. The undesirable organic solvent is one or more of methanol, ethanol, cyclohexane, n-hexane, and isopropanol; the volume ratio of the good organic solvent to the undesirable organic solvent is 1:0.1-10. The solvent evaporates at 10-40 ℃.

2. Use according to claim 1, characterized in that, Electrodes were fabricated on the surfaces at both ends of an organic micro / nano eutectic, and the surface of the organic micro / nano eutectic was irradiated with a near-infrared light source to be tested, and the photocurrent signal was collected.

3. The application according to claim 1, characterized in that, The wavelength of the near-infrared light is 740 nm-2500 nm.

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