Photoelectric detector, preparation method thereof and photoelectric detection system

Abstract

The invention discloses a photoelectric detector, a preparation method thereof and a photoelectric detection system, and relates to the technical field of semiconductor devices. The photoelectric detector includes: a substrate; the photosensitive structure is positioned on one side of the substrate; the photosensitive structure extends along a first direction; the photosensitive structure is a eutectic structure comprising electron donor molecules and electron acceptor molecules; the first electrode structure and the second electrode structure extend in the second direction and are arranged in the first direction, and the first direction intersects with the second direction; the first electrode structure and the second electrode structure are electrically connected with the two opposite ends of the photosensitive structure respectively. According to the technical scheme, the photosensitive structure is set to be the eutectic structure comprising the electron donor molecules and the electron acceptor molecules, so that the spectral response range, the detection efficiency and the polarization sensitivity of the photoelectric detector can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device technology, and in particular to a photodetector and its preparation method and photodetector system. Background Technology

[0002] Photodetectors are core devices that convert optical signals into electrical signals, and are widely used in fields such as biomedical imaging, night vision monitoring, and information communication. In recent years, organic semiconductor materials, with advantages such as tunable bandgap, good mechanical flexibility, and room-temperature fabrication capabilities, have become important candidates for constructing next-generation photodetectors.

[0003] Due to the superior tissue penetration and lower light scattering characteristics of the near-infrared II (1000–1700 nm) wavelength range, the photodetector performance in this region is particularly crucial and holds significant application potential. Most existing organic photodetectors focus on light detection in the ultraviolet to visible light range, with relatively insufficient response capabilities in the near-infrared II region. Current research attempts to achieve near-infrared absorption using single small organic molecule structures; however, the significant π-stacking and strong dipole-dipole interactions between molecules often result in narrow absorption spectra, low emission efficiency, and difficulty in covering a wide spectral range, while also presenting bottlenecks in improving device detection responsivity. Summary of the Invention

[0004] This invention provides a photodetector and its fabrication method, as well as a photodetector system. By setting the photosensitive structure to a eutectic structure including electron donor molecules and electron acceptor molecules, the spectral response range, detection efficiency, and polarization sensitivity of the photodetector can be improved.

[0005] The first aspect of the present invention provides a photodetector, the photodetector comprising:

[0006] Substrate;

[0007] A photosensitive structure is located on one side of the substrate; the photosensitive structure extends along a first direction; the photosensitive structure is a eutectic structure comprising electron donor molecules and electron acceptor molecules;

[0008] The first electrode structure and the second electrode structure both extend along the second direction and are arranged along the first direction, and the first direction and the second direction intersect; the first electrode structure and the second electrode structure are electrically connected to the two ends opposite to the photosensitive structure.

[0009] Optionally, the photodetector further includes a planarization layer located between the first electrode structure and the second electrode structure and the substrate, and between the photosensitive structure and the substrate.

[0010] Optionally, the electron donor molecule may be made of benzothiophene compounds;

[0011] The electron acceptor molecule is made of fluorinated tetracyanoquinoline dimethyl compounds.

[0012] Optionally, the thickness L1 of the first electrode structure is in the range of 95nm≤L1≤105nm;

[0013] The thickness L2 of the second electrode structure has a range of 95nm ≤ L2 ≤ 105nm.

[0014] Optionally, the distance L3 between the first electrode and the second electrode can be in the range of 4μm≤L3≤6μm.

[0015] A second aspect of the present invention provides a method for fabricating a photodetector, the method comprising:

[0016] Provide substrate;

[0017] A photosensitive structure is formed on one side of the substrate; the photosensitive structure extends along a first direction; the photosensitive structure is a eutectic structure comprising electron donor molecules and electron acceptor molecules;

[0018] A first electrode structure and a second electrode structure are formed; both the first electrode structure and the second electrode structure extend along a second direction and are arranged along the first direction, and the first direction and the second direction intersect; the first electrode structure and the second electrode structure are electrically connected to the two ends opposite to the photosensitive structure, respectively.

[0019] Optionally, a photosensitive structure is formed on one side of the substrate, comprising:

[0020] The configuration includes a mixed solution comprising the electron donor molecule and the electron acceptor molecule;

[0021] The mixed solution is spin-coated onto the pretreated substrate surface to allow the solvent in the mixed solution to evaporate and form a eutectic structure comprising the electron donor molecule and the electron acceptor molecule.

[0022] Optionally, the electron donor molecule may be made of benzothiophene compounds; the electron acceptor molecule may be made of fluorotetracyanoquinoline dimethane compounds.

[0023] The configuration includes a mixed solution comprising the electron donor molecule and the electron acceptor molecule, comprising:

[0024] The first amount of benzothiophene compound and the second amount of fluorine-containing tetracyanoquinoline dimethane compound are dissolved in a predetermined volume of acetonitrile to prepare the mixed solution.

[0025] The amount of the first substance is equal to the amount of the second substance.

[0026] Optionally, a first electrode structure and a second electrode structure are formed, including:

[0027] Electrode arrays were prepared using a thermal evaporation process;

[0028] The electrode array is transferred to the two ends opposite to the photosensitive structure and electrically connected to form the first electrode structure and the second electrode structure.

[0029] A third aspect of the present invention provides a photoelectric detection system, which includes: a light source device, a signal processing device, and a photoelectric detector as described above;

[0030] The light source device is located on the side of the photosensitive structure opposite to the substrate, and is used to provide light signals to the photosensitive structure;

[0031] The signal processing device is electrically connected to the first electrode structure and the second electrode structure respectively, and is used to apply a bias voltage between the first electrode structure and the second electrode structure, and to collect the current signal generated by the photodetector to detect the optical signal.

[0032] The technical solution of this invention involves setting a substrate and a photosensitive structure located on one side of the substrate in a photodetector, with the photosensitive structure extending along a first direction. This allows the photosensitive structure to generate photocharge under illumination, providing a response output for the photodetector. By setting both the first and second electrode structures to extend along a second direction intersecting the first direction and arranged along the first direction, and by electrically connecting the first and second electrode structures to the opposite ends of the photosensitive structure, a stable output of the photocurrent generated by the photosensitive structure under illumination is ensured. By setting the photosensitive structure as a eutectic structure including electron donor and electron acceptor molecules, the photodetector's photoelectric conversion efficiency and response speed are improved, while the optical bandgap of the photosensitive material is significantly reduced. This allows the photodetector to effectively detect near-infrared II light signals, making it suitable for applications such as bioimaging, night vision, and long-distance communication. The transition dipole moments of the eutectic structure are distributed along the extension direction of the photosensitive structure, enhancing the intrinsic polarization sensitivity of the photodetector. This allows the photodetector to achieve polarized light detection without the need for external polarizers or polarization filters, contributing to the miniaturization and integration of the photodetector.

[0033] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a photodetector provided in an embodiment of the present invention;

[0036] Figure 2 This is a top view schematic diagram of a photodetector provided in an embodiment of the present invention;

[0037] Figure 3 This is a characterization result diagram of the benzothiophene / tetracyanoquinoline dimethane eutectic provided in the embodiments of the present invention;

[0038] Figure 4 This is a characterization result diagram of the benzothiophene / naphthylquinoline dimethane eutectic provided in the embodiments of the present invention;

[0039] Figure 5 This is a characterization result diagram of the benzothiophene / fluorinated tetracyanoquinoline dimethane eutectic provided in the embodiments of the present invention;

[0040] Figure 6 These are the ultraviolet-visible-near-infrared absorption spectra of different eutectics provided in the embodiments of the present invention;

[0041] Figure 7 This is a schematic diagram of another photodetector provided in an embodiment of the present invention;

[0042] Figure 8 This is a schematic flowchart of a method for fabricating a photodetector according to an embodiment of the present invention;

[0043] Figure 9 This is a schematic diagram of the fabrication process of a photodetector provided in an embodiment of the present invention;

[0044] Figure 10 These are the current-voltage characteristic curves of the photodetector provided in this embodiment of the invention under different light intensities;

[0045] Figure 11 These are the current-voltage characteristic curves of the photodetector provided in this embodiment of the invention at different polarization angles;

[0046] Figure 12 This is a schematic diagram of the structure of a photoelectric detection system provided in an embodiment of the present invention. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0048] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0049] Figure 1 This is a schematic diagram of the structure of a photodetector provided in an embodiment of the present invention. Figure 2 This is a top view schematic diagram of a photodetector provided in an embodiment of the present invention. Figure 1 and Figure 2 As shown, the photodetector includes: a substrate 1; a photosensitive structure 2 located on one side of the substrate 1; the photosensitive structure 2 extending along a first direction; the photosensitive structure 2 being a eutectic structure including electron donor molecules and electron acceptor molecules; a first electrode structure 31 and a second electrode structure 32, both extending along a second direction and arranged along the first direction, the first and second directions intersecting; the first electrode structure 31 and the second electrode structure 32 being electrically connected to the opposite ends of the photosensitive structure 2.

[0050] The substrate 1 serves to support the entire functional structure of the photodetector, and the material of the substrate 1 may include silicon. The photosensitive structure 2 is located on one side of the substrate 1 and extends along a first direction. The photosensitive structure 2 receives light signals provided by an external light source, enabling it to generate photogenerated charges under illumination, thereby converting the light signal into an electrical signal to provide a response output for the photodetector. Specifically, the photosensitive structure 2 is a eutectic structure comprising electron donor molecules and electron acceptor molecules. The electron donor molecules have a high HOMO energy level and can lose electrons after absorbing light, while the electron acceptor molecules have a low LUMO energy level and can effectively capture the electrons released by the electron donor molecules. When the photosensitive structure 2 receives a light signal, the electron donor molecules absorb light energy and excite electron transitions, forming electron-hole pairs. The excited-state electrons can transition from the HOMO of the donor to the LUMO of the acceptor, achieving charge separation. During the transition of the excited-state electrons, electrons are transferred to the electron acceptor molecules, while holes remain on the electron donor molecules, thus forming spatially separated free carrier pairs. By setting the photosensitive structure 2 as a eutectic structure including electron donor molecules and electron acceptor molecules, it is helpful to improve the photoelectric conversion efficiency and response speed of the photodetector.

[0051] Optionally, the electron donor molecule may be made of benzothiophene compounds; the electron acceptor molecule may be made of fluorotetracyanoquinodimethane compounds. For example, the electron donor molecule may include benzo[b]benzo[4,5]thieno[2,3-d]thiophene conjugated compounds, which have high hole mobility and molecular planarity, contributing to enhanced charge transport in the eutectic structure. The electron acceptor molecule may include 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane compounds, which possess strong electron-withdrawing ability and excellent molecular stacking ability. The fluoride ion in the electron acceptor molecule, as a strong electron-withdrawing group, can further enhance the electron affinity of the electron acceptor molecule, thereby improving its charge-trapping ability. Electron donor molecules and electron acceptor molecules can self-assemble into rod-shaped eutectic structures through intermolecular π-π interactions and charge transfer interactions, which have uniaxial transition dipole moments. In addition, the introduction of fluorine can enhance non-covalent interactions between molecules, such as halogen bonding, to improve the molecular packing order and crystal quality, thereby enhancing the order and directionality of the eutectic structure.

[0052] Through the strong charge-transfer interaction between the electron donor and electron acceptor molecules in photosensitive structure 2, a new charge-transfer excited state is formed in the eutectic structure, rearranging molecular orbitals and significantly reducing the optical bandgap of the photosensitive material. This enables photosensitive structure 2 to possess strong light absorption capabilities in the ultraviolet to near-infrared II region, overcoming the limitation of absorption bandwidth in traditional organic single-component photosensitive materials. The eutectic structure based on fluorine-containing electron acceptor molecules exhibits excellent photoelectric response characteristics in the 1064nm near-infrared band, effectively detecting near-infrared II light signals, making the photodetector suitable for applications such as biological imaging, night vision, and long-distance communication. Meanwhile, in the eutectic structure, electron donor molecules and electron acceptor molecules are highly anisotropically packed along the crystal growth direction. The transition dipole moment of the eutectic structure is distributed along the extension direction of the photosensitive structure 2, i.e., the first direction, thereby improving the intrinsic polarization sensitivity of the photodetector. This allows the photodetector to achieve polarized light detection without the need for external polarizers, polarization filters, or other separate optical components. While exhibiting significant anisotropic response characteristics in the near-infrared II region, it simplifies the structural design of the photodetector and contributes to its miniaturization and integration.

[0053] To determine the materials of the electron donor and electron acceptor molecules suitable for the photodetector in this embodiment, various charge-transfer eutectic systems can be prepared, and their crystal morphology, optical absorption properties, and near-infrared response capabilities can be investigated respectively. For example, charge-transfer cocrystals of benzo[b]benzo[4,5]thieno[2,3-d]thiophene with 7,7,8,8-tetracyanoquinodimethane (benzothiophene / tetracyanoquinodimethane cocrystal, BNQ), benzo[b]benzo[4,5]thieno[2,3-d]thiophene with 11,11,12,12-tetracyano-2,6-naphthoquinodimethane (benzothiophene / naphthoquinodimethane cocrystal, BNNQ), and benzo[b]benzo[4,5]thieno[2,3-d]thiophene with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (benzothiophene / fluorinated tetracyanoquinodimethane cocrystal, BF4NQ) can be constructed respectively.

[0054] Each eutectic material can be prepared via solution self-assembly. The preparation method for BNQ includes: weighing 0.01 mmol of benzo[b]benzo[4,5]thieno[2,3-d]thiophene and 0.01 mmol of 7,7,8,8-tetracyanoquinoline dimethane, and dissolving them together in 2 ml of dichloromethane to obtain an organic small molecule solution. Adding 2 ml of ethanol to the organic small molecule solution, maintaining a dichloromethane to ethanol volume ratio of 1:1, and shaking to mix thoroughly, yields a mixed solution. At room temperature, the obtained mixed solution is directly dropped onto substrate 1. As the solvent completely evaporates, intermolecular self-assembly occurs, and a benzo[b]thiophene / tetracyanoquinoline dimethane eutectic grows on the substrate. The prepared benzo[b]thiophene / tetracyanoquinoline dimethane eutectic is characterized using scanning electron microscopy, and the characterization results are as follows: Figure 3 As shown in the figure. The results show that the prepared eutectic exhibits a typical micron rod-like morphology with an average length of approximately 20 μm. The preparation method of BNNQ may include: weighing 0.01 mmol of benzo[b]benzo[4,5]thieno[2,3-d]thiophene and 0.01 mmol of 11,11,12,12-tetracyano-2,6-naphthylquinoline dimethane, dissolving them in 2 ml of dichloromethane to obtain a mixed solution. At room temperature, the mixed solution is directly dropped onto substrate 1. As the solvent evaporates naturally, the solute reaches a supersaturated state and crystals precipitate, growing a benzothiophene / naphthylquinoline dimethane eutectic on the substrate. The prepared benzothiophene / naphthylquinoline dimethane eutectic was characterized by scanning electron microscopy, and the characterization results are shown in the figure. Figure 4 As shown in the figure. The results show that the eutectic exhibits a slender, micron-like morphology with an average length of approximately 80 μm. The preparation method of BF4NQ may include: weighing 0.01 mmol of benzo[b]benzo[4,5]thieno[2,3-d]thiophene and 0.01 mmol of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethylethane, dissolving them in 2 ml of acetonitrile to obtain a mixed solution. At room temperature, the obtained mixed solution is directly dropped onto a glass substrate. As the solvent completely evaporates, electron donor and electron acceptor molecules undergo self-assembly through strong charge transfer interactions and halogen bonding, growing a benzothiophene / fluorinated tetracyanoquinodimethyl eutectic on the substrate. The prepared benzothiophene / fluorinated tetracyanoquinodimethyl eutectic was characterized by scanning electron microscopy, and the characterization results are shown in the figure. Figure 5 As shown in the figure. The results show that the eutectic exhibits a long-range ordered micron rod-like structure with an average length of approximately 60 μm.

[0055] To evaluate the optical properties of the aforementioned eutectic structures, ultraviolet-visible-near-infrared absorption spectra were measured for the three eutectic structures: BNQ, BNNQ, and BF4NQ. The test results are as follows: Figure 6As shown in the figure. The results show that all three eutectic structures exhibit a wide absorption bandwidth, covering the ultraviolet to near-infrared region. Among them, the optical band gaps of the BNQ eutectic structure and the BNNQ eutectic structure are approximately 1.47 eV and 1.46 eV, respectively, while the BF4NQ eutectic structure exhibits a wider absorption range, with the absorption edge extending to approximately 1100 nm and the optical band gap significantly reduced to 1.13 eV, indicating that the BF4NQ eutectic structure has superior near-infrared II light absorption capability. Therefore, the electron donor molecule of photosensitive structure 2 is preferably a benzothiophene compound, and the electron acceptor molecule is preferably a fluorotetracyanoquinoline dimethane compound.

[0056] Both the first electrode structure 31 and the second electrode structure 32 extend along a second direction intersecting the first direction and are arranged along the first direction, i.e., the first electrode structure 31 and the second electrode structure 32 span the length of the photosensitive structure 2, forming an electrode pair. The materials of the first electrode structure 31 and the second electrode structure 32 may include gold, silver, or other highly conductive metals. The first electrode structure 31 and the second electrode structure 32 are electrically connected to the opposite ends of the photosensitive structure 2. For example, the first electrode structure 31 and the second electrode structure 32 can both be disposed above the photosensitive structure 2 to ensure that the photocurrent generated by the photosensitive structure 2 under illumination can be stably output. It is understood that by applying a bias voltage between the first electrode structure 31 and the second electrode structure 32, the photogenerated carriers generated by the photosensitive structure 2 under illumination will migrate directionally under the action of the electric field, forming a measurable photocurrent signal. By analyzing the amplitude and characteristics of the photocurrent signal as a function of the polarization angle, the intensity information and polarization direction information of the incident light can be obtained.

[0057] In this embodiment, a substrate and a photosensitive structure located on one side of the substrate are disposed in the photodetector, and the photosensitive structure extends along a first direction. This allows the photosensitive structure to generate photocharge under illumination, providing a response output for the photodetector. By arranging the first and second electrode structures along a second direction intersecting the first direction and aligned along the first direction, and by electrically connecting the first and second electrode structures to the opposite ends of the photosensitive structure, a stable output of the photocurrent generated by the photosensitive structure under illumination is ensured. By setting the photosensitive structure as a eutectic structure including electron donor and electron acceptor molecules, the photodetector's photoelectric conversion efficiency and response speed are improved. Simultaneously, the optical bandgap of the photosensitive material is significantly reduced, enabling the photodetector to effectively detect near-infrared II light signals, suitable for applications such as bioimaging, night vision, and long-distance communication. The transition dipole moments of the eutectic structure are distributed along the extension direction of the photosensitive structure, enhancing the intrinsic polarization sensitivity of the photodetector. This allows the photodetector to achieve polarized light detection without the need for external polarizers or polarization filters, contributing to the miniaturization and integration of the photodetector.

[0058] Optional, Figure 7 This is a schematic diagram of another photodetector provided in an embodiment of the present invention. Figure 7 and Figure 2 As shown, the photodetector also includes a planarization layer 4 located between the first electrode structure 31 and the second electrode structure 32 and the substrate 1, and between the photosensitive structure 2 and the substrate 1.

[0059] Specifically, the planarization layer 4 is located between the first electrode structure 31 and the second electrode structure 32 and the substrate 1, and between the photosensitive structure 2 and the substrate 1, to form a uniform and flat support interface on the surface of the substrate 1. For example, the material of the planarization layer 4 may include silicon dioxide, which has good insulation, thermal stability, and mechanical stability, making it suitable for supporting and electrically isolating subsequent functional structures. By setting the planarization layer 4, the microscopic undulations on the surface of the substrate 1 can be effectively covered, thereby providing a flat foundation for the subsequent construction of the first electrode structure 31, the second electrode structure 32, and the photosensitive structure 2, which helps improve the consistency and stability of the photodetector structure. Simultaneously, the planarization layer 4 can achieve electrical isolation between different functional regions of the photodetector, thereby improving the signal-to-noise ratio and photodetector sensitivity.

[0060] Optional, continue to refer to Figure 7 The thickness L1 of the first electrode structure 31 has a range of 95nm ≤ L1 ≤ 105nm; the thickness L2 of the second electrode structure 32 has a range of 95nm ≤ L2 ≤ 105nm.

[0061] Specifically, the thickness L1 of the first electrode structure 31 ranges from 95 nm to 105 nm, and the thickness L2 of the second electrode structure 32 ranges from 95 nm to 105 nm. The thicknesses of both are similar or identical to ensure the structural integrity of the photodetector. By controlling the thickness of both the first electrode structure 31 and the second electrode structure 32 to approximately 100 nm, the continuity and conductivity of the electrode structures can be guaranteed. It is understandable that if the first electrode structure 31 and the second electrode structure 32 are too thin, it may lead to problems such as open circuits, breaks, or high contact resistance; if the first electrode structure 31 and the second electrode structure 32 are too thick, it may lead to structural warping, increased film stress, or even damage to the morphology or crystal orientation of the photosensitive structure 2, affecting the performance of the photodetector. Therefore, by controlling the thickness of the first electrode structure 31 and the second electrode structure 32 within an appropriate range, the process compatibility and device stability of the photodetector can be improved.

[0062] Optional, continue to refer to Figure 7The value range of the distance L3 between the first electrode structure 31 and the second electrode structure 32 is: 4μm≤L3≤6μm.

[0063] Specifically, the spacing between the first electrode structure 31 and the second electrode structure 32 ranges from 4 μm to 6 μm. This spacing corresponds to the channel length in the photodetector. By controlling the channel length to the micrometer level, a stronger electric field is established between the first electrode structure 31 and the second electrode structure 32, which effectively accelerates the separation and directional migration of photogenerated carriers in the photosensitive structure 2, improving the output efficiency and response speed of the photocurrent. Furthermore, if the spacing between the first electrode structure 31 and the second electrode structure 32 is too short, it may lead to increased leakage current and dark current, thus affecting the signal-to-noise ratio and stability of the photodetector. Therefore, controlling the spacing between the first electrode structure 31 and the second electrode structure 32 within a suitable range achieves a balance between enhancing the electric field strength and suppressing leakage current, improving the weak light detection capability and performance stability of the photodetector.

[0064] Based on the same inventive concept, this invention also provides a method for fabricating a photodetector. Figure 8 This is a schematic flowchart of a method for fabricating a photodetector according to an embodiment of the present invention. Figure 9 This is a structural schematic diagram of the fabrication process of a photodetector provided in an embodiment of the present invention, combined with... Figure 8 and Figure 9 As shown, the fabrication method of this photodetector includes:

[0065] S101, Provide substrate.

[0066] The substrate 1 is used to support the functional structure of the entire photodetector, and the material of the substrate 1 may include silicon.

[0067] S102, A photosensitive structure is formed on one side of the substrate.

[0068] Among them, the photosensitive structure 2 extends along the first direction; the photosensitive structure 2 is a eutectic structure including electron donor molecules and electron acceptor molecules.

[0069] Specifically, a photosensitive structure 2 can be formed on one side of substrate 1 through solution-induced crystallization. The photosensitive structure 2 extends along a first direction and is used to receive light signals provided by an external light source. Under illumination, it generates photogenerated charges, thereby converting the light signal into an electrical signal to provide a response output for the photodetector. The photosensitive structure 2 is a eutectic structure comprising electron donor molecules and electron acceptor molecules. The electron donor molecules have a high HOMO energy level and can lose electrons after absorbing light, while the electron acceptor molecules have a low LUMO energy level and can effectively capture the electrons released by the electron donor molecules. When the photosensitive structure 2 receives a light signal, the electron donor molecules absorb light energy and excite electron transitions, forming electron-hole pairs. The excited-state electrons can transition from the HOMO of the donor to the LUMO of the acceptor, achieving charge separation. During the transition of the excited-state electrons, electrons are transferred to the electron acceptor molecules, while holes remain on the electron donor molecules, thus forming spatially separated free carrier pairs. By setting the photosensitive structure 2 as a eutectic structure including electron donor molecules and electron acceptor molecules, it is helpful to improve the photoelectric conversion efficiency and response speed of the photodetector.

[0070] Optionally, a photosensitive structure 2 is formed on one side of the substrate 1, including: configuring a mixed solution comprising electron donor molecules and electron acceptor molecules; spin-coating the mixed solution onto the surface of the pretreated substrate 1 to allow the solvent of the mixed solution to evaporate and form a eutectic structure comprising electron donor molecules and electron acceptor molecules.

[0071] Specifically, the method for forming the photosensitive structure 2 on one side of the substrate 1 can be as follows: First, a mixed solution comprising electron donor molecules and electron acceptor molecules is prepared, and the mixed solution is spin-coated or dropped onto the surface of the substrate 1 after ozone pretreatment. At room temperature, the solvent in the mixed solution evaporates, and the electron donor and electron acceptor molecules spontaneously crystallize on the surface of the substrate 1 using intermolecular charge transfer interactions and π-π stacking effects, thereby forming a eutectic photosensitive structure with one-dimensional orientation.

[0072] Optionally, the preparation of a mixed solution comprising electron donor molecules and electron acceptor molecules includes: dissolving a first amount of a benzothiophene compound and a second amount of a fluorinated tetracyanoquinoline dimethane compound in a predetermined volume of acetonitrile to prepare the mixed solution; wherein the first amount is equal to the second amount.

[0073] Specifically, the method for preparing a mixed solution comprising electron donor and electron acceptor molecules can be as follows: a first molar amount of a benzothiophene compound and a second molar amount of a fluorinated tetracyanoquinoline dimethane compound are dissolved in a predetermined volume of acetonitrile at a 1:1 molar ratio to form a mixed solution of electron donor and electron acceptor molecules. For example, the mixed solution can be prepared by weighing 0.01 mmol of benzo[b]benzo[4,5]thieno[2,3-d]thiophene and 0.01 mmol of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinoline dimethane and dissolving them in 2 ml of acetonitrile. It is understood that using an equimolar ratio of electron donor and electron acceptor molecules can achieve a balance between the electron transfer driving force and intermolecular forces in the mixed solution, which helps to form a stable and ordered eutectic structure during subsequent solvent evaporation. Meanwhile, proportional mixing can also avoid the enrichment or absence of a certain component in the eutectic structure, improve the compositional uniformity and structural symmetry of the photosensitive structure 2, thereby improving the charge transfer efficiency and optical performance consistency of the photodetector.

[0074] S103, forming the first electrode structure and the second electrode structure.

[0075] The first electrode structure 31 and the second electrode structure 32 both extend along the second direction and are arranged along the first direction, and the first direction and the second direction intersect; the first electrode structure 31 and the second electrode structure 32 are electrically connected to the two ends opposite to the photosensitive structure 2, respectively.

[0076] Specifically, the first electrode structure 31 and the second electrode structure 32 can be formed through a thermal evaporation process. Both the first electrode structure 31 and the second electrode structure 32 extend along a second direction intersecting the first direction and are arranged along the first direction, meaning they span the length of the photosensitive structure 2, forming an electrode pair. The materials of the first electrode structure 31 and the second electrode structure 32 can include gold, silver, or other highly conductive metals. The first electrode structure 31 and the second electrode structure 32 are electrically connected to opposite ends of the photosensitive structure 2 to ensure a stable output of the photocurrent generated by the photosensitive structure 2 under illumination. It is understood that by applying a bias voltage between the first electrode structure 31 and the second electrode structure 32, the photogenerated carriers generated by the photosensitive structure 2 under illumination will migrate directionally under the influence of an electric field, forming a measurable photocurrent signal. By analyzing the amplitude and polarization angle characteristics of this photocurrent signal, the intensity and polarization direction information of the incident light can be obtained.

[0077] Optionally, forming the first electrode structure and the second electrode structure includes: preparing an electrode array using a thermal evaporation process; and transferring the electrode array to electrically connect the two ends opposite to the photosensitive structure 2 to form the first electrode structure 31 and the second electrode structure 32.

[0078] Specifically, a mask thermal evaporation process can be used to fabricate the metal electrode array. For example, within the constraints of a pre-defined mask pattern, a metal electrode pattern can be deposited on an independent substrate, such as a rigid silicon wafer or a flexible film, using thermal evaporation. Gold is preferably used as the electrode material, and the thickness can be controlled to approximately 100 nm to ensure good conductivity and structural stability of the electrode structure. After forming the electrode array, a microscope can be used for manipulation, and a microprobe can be used to control and position the electrode structure, electrically connecting the first electrode structure 31 and the second electrode structure 32 to their respective opposite ends of the photosensitive structure 2. The spacing between the first electrode structure 31 and the second electrode structure 32 can be controlled to approximately 5 μm, thereby completing the construction of the electrode structure.

[0079] The above-described method for fabricating the photodetector can be used to prepare the photodetector provided in any embodiment of the present invention, which possesses the corresponding functions and beneficial effects of a photodetector. Technical details not described in detail in this embodiment can be found in the photodetector provided in any embodiment of the present invention.

[0080] Since the photodetector fabrication method described above can be used to fabricate the photodetector in the embodiments of the present invention, those skilled in the art can understand the specific implementation methods and various variations of the photodetector fabrication method described in the embodiments of the present invention based on the photodetector described in the embodiments of the present invention. Therefore, how the photodetector fabrication method is implemented to fabricate the photodetector in the embodiments of the present invention will not be described in detail here. As long as those skilled in the art implement the method for fabricating the photodetector in the embodiments of the present invention, they are all within the scope of protection of this application.

[0081] To verify the performance of the photodetector in this embodiment of the invention, the following experimental tests can be performed on the photodetector. To verify the response performance of the photodetector in the near-infrared II band of this embodiment, electrical tests were performed on the photodetector using a semiconductor parameter analyzer under ambient temperature and atmospheric conditions, using a laser with a wavelength of 1064 nm as the incident light source. Figure 10The current-voltage characteristic curves of the photodetector under different light intensities are shown. Test results indicate that under no-light conditions, the dark current of the photodetector remains at the nanoampere level under a ±20V bias voltage, demonstrating excellent low-noise characteristics. Under laser irradiation, the photodetector generates a significant photocurrent, and this photocurrent increases linearly with the incident light power density increasing from 4.31 μW / cm² to 1429.02 μW / cm², indicating that the photodetector has a good linear response capability to light intensity. These results fully demonstrate that the organic photodetector based on the eutectic structure in this embodiment possesses excellent photoelectric conversion efficiency and weak light detection capability in the near-infrared II region.

[0082] To verify the polarization detection performance of the photodetector in this embodiment of the invention, under ambient temperature and with incident laser light at a wavelength of 1064 nm and a power density of 978.52 μW / cm², the polarization sensitivity of the photodetector was characterized by adjusting the polarization angle of the incident light using a half-wave plate. During the test, the bias voltage was kept constant, and different polarization angles, such as 0°, 30°, 60°, and 90°, were achieved by rotating the half-wave plate, and the corresponding photocurrent response was recorded. Figure 11 The current-voltage characteristic curves of the photodetector at different polarization angles are shown. The results indicate that the photocurrent reaches its maximum value at a polarization angle of 0°, i.e., when the polarization direction of the incident light is aligned with the extension direction of the eutectic structure, while it drops to its minimum at a polarization angle of 90°, exhibiting a significant anisotropic response. This periodic variation in photocurrent is attributed to the one-dimensional ordered stacking of electron donor and electron acceptor molecules along the crystal growth direction in the eutectic structure, resulting in a specific orientation of the charge transition dipole moment, thereby achieving an intrinsic response to the polarization state. This demonstrates that the photodetector of this embodiment can achieve excellent polarization detection capability without the need for an external polarizer.

[0083] Based on the same inventive concept, embodiments of the present invention also provide a photoelectric detection system. Figure 12 This is a schematic diagram of the structure of a photoelectric detection system provided in an embodiment of the present invention. Figure 12 As shown, the photoelectric detection system includes: a light source device 01, a signal processing device 02, and a photodetector according to an embodiment of the present invention; the light source device 01 is located on the side of the photosensitive structure 2 away from the substrate 1, and is used to provide an optical signal to the photosensitive structure 2; the signal processing device 02 is electrically connected to the first electrode structure 31 and the second electrode structure 32 respectively, and is used to apply a bias voltage between the first electrode structure 31 and the second electrode structure 32, and to collect the current signal generated by the photodetector to detect the optical signal.

[0084] Specifically, in the photoelectric detection system, the light source device 01 is located on the side of the photosensitive structure 2 facing away from the substrate 1, and is used to provide an optical signal to the photosensitive structure 2 so that the photosensitive structure 2 can generate photogenerated charges under illumination, thereby converting the optical signal into an electrical signal and providing a response output for the photodetector. The signal processing device 02 is electrically connected to the first electrode structure 31 and the second electrode structure 32 respectively, and is used to apply a bias voltage between the first electrode structure 31 and the second electrode structure 32, so that the photogenerated carriers generated by the photosensitive structure 2 under illumination can migrate directionally under the action of the electric field to form a measurable photocurrent signal. At the same time, the signal processing device 02 can also collect the photocurrent signal generated by the photodetector, and by analyzing the amplitude and polarization angle of the photocurrent signal, the intensity information and polarization direction information of the incident light can be obtained.

[0085] Therefore, the photoelectric detection system provided in this embodiment has the structure and operation of the photoelectric detector provided in the above embodiment, and can achieve the effect of the photoelectric detector in the above embodiment. The similarities can be referred to the above description, and will not be repeated here.

[0086] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0087] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A photodetector, characterized in that, include: Substrate; A photosensitive structure is located on one side of the substrate; The photosensitive structure extends along the first direction; The photosensitive structure is a eutectic structure comprising electron donor molecules and electron acceptor molecules; A first electrode structure and a second electrode structure, both extending along a second direction and arranged along the first direction, wherein the first direction and the second direction intersect; The first electrode structure and the second electrode structure are electrically connected to the two ends opposite to the photosensitive structure, respectively.

2. The photodetector according to claim 1, characterized in that, Also includes: A planarization layer located between the first electrode structure and the second electrode structure and the substrate, and between the photosensitive structure and the substrate.

3. The photodetector according to claim 1, characterized in that, The electron donor molecule is made of benzothiophene compounds; The electron acceptor molecule is made of fluorinated tetracyanoquinoline dimethyl compounds.

4. The photodetector according to claim 1, characterized in that, The thickness L1 of the first electrode structure has a range of 95nm ≤ L1 ≤ 105nm; The thickness L2 of the second electrode structure has a range of 95nm ≤ L2 ≤ 105nm.

5. The photodetector according to claim 1, characterized in that, Along the first direction, the spacing L3 between the first electrode structure and the second electrode structure ranges from 4μm≤L3≤6μm.

6. A method for fabricating a photodetector, characterized in that, include: Provide substrate; A photosensitive structure is formed on one side of the substrate; The photosensitive structure extends along the first direction; The photosensitive structure is a eutectic structure comprising electron donor molecules and electron acceptor molecules; A first electrode structure and a second electrode structure are formed; both the first electrode structure and the second electrode structure extend along a second direction and are arranged along the first direction, and the first direction and the second direction intersect; the first electrode structure and the second electrode structure are electrically connected to the two ends opposite to the photosensitive structure, respectively.

7. The method for fabricating a photodetector according to claim 6, characterized in that, A photosensitive structure is formed on one side of the substrate, comprising: The configuration includes a mixed solution comprising the electron donor molecule and the electron acceptor molecule; The mixed solution is spin-coated onto the pretreated substrate surface to allow the solvent in the mixed solution to evaporate and form a eutectic structure comprising the electron donor molecule and the electron acceptor molecule.

8. The method for fabricating a photodetector according to claim 7, characterized in that, The electron donor molecule is made of benzothiophene compounds; the electron acceptor molecule is made of fluorotetracyanoquinoline dimethane compounds. The configuration includes a mixed solution comprising the electron donor molecule and the electron acceptor molecule, comprising: The first amount of benzothiophene compound and the second amount of fluorine-containing tetracyanoquinoline dimethane compound are dissolved in a predetermined volume of acetonitrile to prepare the mixed solution. The amount of the first substance is equal to the amount of the second substance.

9. The method for fabricating a photodetector according to claim 6, characterized in that, The formation of the first electrode structure and the second electrode structure includes: Electrode arrays were prepared using a thermal evaporation process; The electrode array is transferred to the two ends opposite to the photosensitive structure and electrically connected to form the first electrode structure and the second electrode structure.

10. A photoelectric detection system, characterized in that, include: A light source device, a signal processing device, and a photodetector as described in any one of claims 1-6; The light source device is located on the side of the photosensitive structure opposite to the substrate, and is used to provide light signals to the photosensitive structure; The signal processing device is electrically connected to the first electrode structure and the second electrode structure respectively, and is used to apply a bias voltage between the first electrode structure and the second electrode structure, and to collect the current signal generated by the photodetector to detect the optical signal.

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