Liquid crystal micromolecule auxiliary orientation full-micromolecule linearly polarized light photoelectric detector and preparation method and application thereof

Abstract

The invention discloses a liquid crystal micromolecule auxiliary orientation full-micromolecule linearly polarized light photoelectric detector. The liquid crystal micromolecule auxiliary orientation full-micromolecule linearly polarized light photoelectric detector comprises a cathode, an electron transport layer, a photoactive layer, a hole transport layer and an anode. Wherein the material of the optical active layer comprises a P-type liquid crystal micromolecule material and an N-type micromolecule acceptor material; the full-micromolecule polarization sensitive photoelectric detection element is simple in structure, easy to prepare, low in energy consumption, capable of working at room temperature, flexible, adjustable in spectrum and low in cost, and has a huge application prospect in a light, small, integrated and spatial polarization detection system in the future.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to a fully small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules, a preparation method thereof, and an application thereof. Background Art

[0002] Polarization is one of the important physical properties of light in addition to intensity (amplitude), wavelength (frequency), and phase. Introducing polarization into a detector can expand the detectable dimensions of optical signals. These dimensions include degree of polarization, polarization angle, polarization ellipticity, polarization rotation direction, etc., significantly enhancing the detection and analysis capabilities of imaging systems, and thus being widely used in aspects such as atmospheric remote sensing, target detection, reconnaissance, biomedicine, industrial production, etc.

[0003] With the rapid development of microelectronic devices towards high integration and miniaturization, polarization-sensitive photodetector devices based on organic semiconductor materials have received extensive attention. Organic semiconductor materials have the advantages of being flexible, thin, light, simple to prepare, and low in cost, and can be roughly divided into polymer and small-molecule materials. However, compared with small molecules, there are often differences between batches of polymers, resulting in different characteristics of polymers. Taking molecular weight as an example, polymers with different molecular weights have different effects when treated with the same method, and the experimental repeatability is relatively low. Small-molecule materials usually exhibit higher batch consistency due to their clear molecular structure and controllable synthesis methods. In addition, due to its high-efficiency purification process characteristics, this system shows significant cost advantages over polymer materials in large-scale production. In addition, small-molecule materials have occupied a dominant position in commercial display devices represented by smartphone OLED screens on the market at present, and there is mature commercial experience, but there is currently no research on the preparation of fully small-molecule polarization detectors.

[0004] People have long been committed to developing simpler and more compact high-performance polarization-sensitive photodetectors to improve their applicability, performance, and integration in various application fields. However, achieving high-quality polarization detection, especially in the near-infrared region, remains a major challenge in the field of organic semiconductors. Currently, a common device structure strategy is to use uniaxially oriented π-conjugated polymers, and their high molecular aspect ratio gives them inherent linear dichroism. However, although the global orientation of the polymer backbone results in a uniaxial arrangement of transition dipole moments at different scales, relying solely on the polymer system has become a limiting factor for further improving polarization detection performance.

[0005] Small molecules have a smaller aspect ratio compared to polymers. It is difficult for a single small molecule to form a film with a certain ordered arrangement. In previous related reports, more often, polymers with a larger aspect ratio such as P3HT were added to form an ordered-structured film. Based on this film, optoelectronic devices achieved a polarization effect. Small molecules have their outstanding advantages compared to polymers. However, small molecule systems have not yet been introduced into the fabrication of organic optoelectronic polarization detectors. In view of this, seeking a method to fabricate an all-small molecule polarization detector has great practical significance. Summary of the Invention

[0006] Based on the defects and deficiencies in the prior art, the present invention provides a liquid crystal small molecule-assisted orientation all-small molecule linear polarization optoelectronic detector.

[0007] An object of the present invention is to provide the above-mentioned liquid crystal small molecule-assisted orientation all-small molecule linear polarization optoelectronic detector, which includes the following structure: a cathode, an electron transport layer, a photoactive layer, a hole transport layer, and an anode;

[0008] Among them, the material of the photoactive layer includes a P-type liquid crystal small molecule material and an N-type small molecule acceptor material;

[0009] The material of the P-type liquid crystal small molecule includes but is not limited to one or more of BTR, BTR-Cl, and B1;

[0010] The material of the N-type small molecule acceptor includes but is not limited to one or more of Y6, L8-BO, BTP-eC9, PC 61 BM and PC 71 BM;

[0011] The photoactive layer can be a single layer or a multi-layer composite layer, and must include an alignment layer and may include a non-alignment layer;

[0012] Further, the content of the P-type liquid crystal small molecule material is not less than 10 wt%.

[0013] Further, the material of the electron transport layer includes but is not limited to one or more of ZnO, PFN-Br, and PNDIT-F3N.

[0014] Further, the electron transport layer can be a single layer or a multi-layer composite layer.

[0015] Further, the material of the hole transport layer includes but is not limited to one or more of MoO3, PEDOT:PSS, WO3, PVK, TPD, Spiro-TPD, and NPD.

[0016] Further, the hole transport layer can be a single layer or a multi-layer composite layer.

[0017] Furthermore, the thickness of the photoactive layer is 5 - 500 nm.

[0018] Specifically, the materials of the cathode and anode include, but are not limited to, conductive oxides (such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO)), metals (such as one or more of silver (Ag), gold (Au), and aluminum (Al)), and one or more of metal nanowires.

[0019] Specifically, the electron transport layer can help improve the energy level matching between the photoactive layer and the cathode, and promote electron transport from the photoactive layer to the electrode. The electron transport layer includes, but is not limited to, one or more of ZnO, PFN-Br, and PNDIT-F3N.

[0020] Specifically, the hole transport layer can help improve the energy level matching between the photoactive layer and the anode, and promote hole transport from the photoactive layer to the electrode. The hole transport layer includes, but is not limited to, one or more of MoO3, PEDOT:PSS, WO3, PVK, TPD, Spiro-TPD, and NPD.

[0021] Furthermore, the incident direction of the optical signal is the cathode or the anode.

[0022] Specifically, the preparation method of the photoactive layer includes one or more of spin coating, floating film transfer, high-temperature friction, mechanical stretching, and blade scraping methods.

[0023] Specifically, as Figure 3 shown, preparing the photoactive layer by the molecular orientation method can make it have optical anisotropy. When the electric field direction of the incident linearly polarized light is parallel to the direction of the optical transition dipole moment, the absorption intensity is the largest, and this polarization direction is defined as the (0°) direction, while the absorption in the perpendicular direction is the smallest, and this polarization direction is defined as the (90°) direction. The device utilizes the difference in the absorption intensity of the photoactive layer for light with different polarization directions to generate different current responses. This difference enables the device to detect and distinguish light with different linear polarization states, thereby realizing the detection function of linearly polarized light.

[0024] In particular, the photodetector of the present invention has a polarization detection function in the visible light and near-infrared bands.

[0025] Another object of the present invention is to provide the application of the all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules in the field of semiconductor materials.

[0026] The beneficial effects of the present invention are as follows:

[0027] The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules in the present invention can achieve high-efficiency performance in polarization detection by using small molecules with a low aspect ratio as the material of the photoactive layer. Moreover, the photodetector of the present invention has a simple structure, is easy to prepare, has low energy consumption, can work at room temperature, is flexible, has adjustable spectrum, and is inexpensive, and has great application prospects in future light, small and integrated, and space-type polarization detection systems. Description of the Drawings

[0028] Figure 1 Shows a schematic structural diagram of the all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules of the present invention.

[0029] In the figure: 1. Anode; 2. Hole transport layer; 3. Photoactive layer; 4. Electron transport layer; 5. Cathode.

[0030] Figure 2 Shows a structural diagram of the active layer organic semiconductor materials used in Examples 1-3 and Comparative Example 1.

[0031] Figure 3 Shows a schematic diagram of the floating film transfer method used in Examples 1-3 and Comparative Example 1.

[0032] Figure 4 Shows the definitions of the linearly polarized light angles of 0°, 45°, 90°, and 135° in Examples 1-3 and Comparative Example 1.

[0033] Figure 5 Shows the absorption spectrum of the photoactive layer thin film of Example 1.

[0034] Figure 6 Shows the spectrum of the current density varying with wavelength under visible light at 605 nm in Example 1.

[0035] Figure 7 Shows the spectrum of the current density varying with wavelength under near-infrared light at 850 nm in Example 1.

[0036] Figure 8 Shows the external quantum efficiency spectrum of the all-small-molecule polarization-sensitive photodetector element of Example 1 under polarized light irradiation.

[0037] Figure 9 Shows the light response signal-time spectrum of the all-small-molecule polarization-sensitive photodetector element of Example 1 at 630 nm.

[0038] Figure 10 Shows the light response signal-time spectrum of the all-small-molecule polarization-sensitive photodetector element of Example 1 at 630 nm.

[0039] Figure 11Shows the current density-voltage curve of the photodetector of Example 2 under illumination with linearly polarized light at 605 nm.

[0040] Figure 12 Shows the current density-voltage curve of the photodetector of Example 2 under illumination with linearly polarized light at 850 nm. Detailed implementation manners

[0041] To more clearly illustrate the technical solutions of the present invention, the following examples are listed. Unless otherwise specified, the raw materials, reactions, and post-treatment means appearing in the examples are common raw materials on the market and technical means well-known to those skilled in the art.

[0042] The terms "preferred", "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain cases. However, in the same or other cases, other embodiments may also be preferred. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention.

[0043] It should be understood that unless otherwise indicated in any operating example or otherwise, all numbers representing the amounts of ingredients used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and appended claims are approximations that vary depending upon the desired properties sought to be obtained by the present invention.

[0044] Example 1

[0045] A fully small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules, the structure of which is as Figure 1 shown, and its device structure is successively: cathode 5 (ITO, 55 nm) / electron transport layer 4 (ZnO, 50 nm, PFN-Br, 10 nm) / photoactive layer 3 (PC 61 BM, 10 nm, BTR:Y6, 10:1, wt / wt, 100 nm) / hole transport layer 2 (MoO3, 10 nm) / anode 1 (Ag, 100 nm).

[0046] The preparation method of the fully small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules is as follows:

[0047] S1. Take 10 μL of ZnO solution and uniformly coat it on the upper surface of the cathode, and spin-coat to obtain the ZnO layer under the conditions of 1000 rpm and 15 s; then take 10 μL of PFN-Br solution and spin-coat to obtain the PFN-Br layer under the conditions of 1000 rpm and 10 s; the two layers together constitute the electron transport layer;

[0048] Among them, the ZnO solution is prepared according to the ratio of 100 mg of dehydrated zinc acetate and 28 mg of ethanolamine dissolved in 1 ml of ethylene glycol monoethyl ether; the solvent used for the PFN-Br solution is methanol, and the concentration is 1 mg / ml;

[0049] S2-1. Take 10 μL of the PC 61 BM solution and spin-coat it under the condition of 1500 rpm to obtain the PC 61 BM layer;

[0050] Among them, the solvent used for the PC 61 BM solution is chlorobenzene, and the concentration is 20 mg / ml;

[0051] S2-2. Blend the liquid crystal small molecule donor BTR and the non-fullerene small molecule acceptor Y6 (10:1, wt / wt) and dissolve them in chloroform to ensure that the concentration of the solute in the mixed solution is 30 mg / ml. After sufficient shaking, place it at room temperature for later use;

[0052] The structures of the said BTR and Y6 are as Figure 2 shown;

[0053] S2-3. Place 100 mL of water:ethylene glycol mixture (1:1, v / v) in a square petri dish, drop 10 μL of the mixed solution at the contact interface between the mixture and the square petri dish, and form a ribbon-like film on the liquid matrix surface;

[0054] S2-4. Transfer the film from the liquid matrix liquid surface to the PC 61 BM layer by transfer printing and perform a drying treatment to obtain a photoactive layer with optical anisotropy;

[0055] S3. Deposit the hole transport layer on the photoactive layer by vacuum evaporation: place the above-prepared sample in a mask plate with an effective area of 0.047 cm 2 , and evaporate 10 nm of MoO3 at a speed of 0.1 nm / s under the condition of a vacuum degree of 5×10 -4 Pa;

[0056] S4. Deposit Ag on the hole transport layer as the anode by vacuum evaporation: evaporate 100 nm of Ag at a speed of 0.1 nm / s under the condition of a vacuum degree of 5×10 -4 Pa to obtain a fully small molecule linearly polarized light photodetector assisted by liquid crystal small molecules.

[0057] Figure 6 and Figure 7The current density-voltage curves of the photodetector of Example 1 under linearly polarized light illumination at 605 nm and 850 nm are respectively shown. It can be seen that there are differences in the device responses under different polarized lights, that is, polarization sensitivity. Therefore, the detection element described in the present invention has the ability to detect linearly polarized light signals.

[0058] Figure 8 The external quantum efficiency spectrum of the photodetector of Example 1 is shown. It can be seen that the device has polarization-sensitive characteristics.

[0059] Figure 9 and Figure 10 The time-responsivity curve of the photodetector of Example 1 under 630 nm illumination is shown, and the rise and fall times of the detector are given as 14 μs and 582 μs respectively.

[0060] Example 2

[0061] A fully small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules has a structure as Figure 1 shown. Its device structure is in sequence: cathode 5 (ITO, 55 nm) / electron transport layer 4 (ZnO, 50 nm, PFN-Br, 10 nm) / photoactive layer 3 (PC 61 BM, 10 nm, BTR-Cl:L8-BO, 10:1, wt / wt, 100 nm) / hole transport layer 2 (MoO3, 10 nm) / anode 1 (Ag, 100 nm);

[0062] The preparation method of the fully small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules is as follows:

[0063] S1. Take 10 μL of ZnO solution and evenly coat it on the upper surface of the cathode, and spin-coat to obtain the ZnO layer under the conditions of 1000 rpm and 15 s; then take 10 μL of PFN-Br solution and spin-coat to obtain the PFN-Br layer under the conditions of 1000 rpm and 10 s; the two layers together constitute the electron transport layer;

[0064] Among them, the ZnO solution is prepared according to the ratio of 100 mg of dehydrated zinc acetate and 28 mg of ethanolamine dissolved in 1 ml of ethylene glycol monoethyl ether; the solvent of the PFN-Br solution is methanol and the concentration is 1 mg / ml;

[0065] S2-1. Take 10 μL of PC 61 BM solution and spin-coat to obtain the PC 61 BM layer under the condition of 1500 rpm;

[0066] Among them, the solvent of the PC 61 BM solution is chlorobenzene and the concentration is 20 mg / ml;

[0067] S2-2. Blend the small molecule donor BTR-Cl and the non-fullerene small molecule acceptor L8-BO (10:1, wt / wt) and dissolve them in chloroform to ensure that the concentration of the solute in the mixed solution is 30 mg / ml. After thorough shaking, place it at room temperature for later use;

[0068] The structures of the aforementioned BTR-Cl and L8-BO are as Figure 2 shown;

[0069] S2-3. Place 100 mL of glycerol:water mixture (1:1, v / v) in a square petri dish. Drop 10 μL of the mixed solution at the contact interface between the mixture and the square petri dish to form a ribbon-like film on the liquid matrix surface;

[0070] S2-4. Transfer the film from the liquid matrix surface to the PC 61 BM layer by transfer printing and perform a drying treatment to obtain a photoactive layer with optical anisotropy;

[0071] S3. Deposit the hole transport layer on the photoactive layer by vacuum evaporation: Place the prepared sample in a mask with an effective area of 0.047 cm 2 Under the condition of a vacuum degree of 5×10 -4 Pa, deposit 10 nm of MoO3 at a speed of 0.1 nm / s;

[0072] S4. Deposit Ag on the hole transport layer as the anode by vacuum evaporation: Under the condition of a vacuum degree of 5×10 -4 Pa, deposit 100 nm of Ag at a speed of 0.1 nm / s to obtain a fully small molecule linearly polarized light photodetector assisted by liquid crystal small molecules.

[0073] Figures 11 - 12 Figure shows the current density-voltage curves of the photodetector in Example 2 under the illumination of linearly polarized light at 605 nm and 850 nm. It can be seen that there are differences in the device responses under different polarized lights, that is, polarization sensitivity.

[0074] Example 3

[0075] A fully small molecule linearly polarized light photodetector assisted by liquid crystal small molecules, whose structure is as Figure 1 shown. Its device structure is in sequence: cathode 5 (ITO, 55 nm) / electron transport layer 4 (ZnO, 50 nm, PFN-Br, 10 nm) / photoactive layer 3 (PC 61 BM, 10 nm, B1:BTP-eC9, 10:1, wt / wt, 100 nm) / hole transport layer 2 (MoO3, 10 nm) / anode 1 (Ag, 100 nm);

[0076] The preparation method of the all-small molecule linearly polarized light photodetector assisted by liquid crystal small molecules is as follows:

[0077] S1. Take 10 μL of ZnO solution and evenly apply it on the upper surface of the cathode, and spin-coat it at 1000 rpm for 15 s to obtain a ZnO layer; then take 10 μL of PFN-Br solution and spin-coat it at 1000 rpm for 10 s to obtain a PFN-Br layer; the two layers together constitute the electron transport layer;

[0078] The ZnO solution was prepared by dissolving 100 mg of dehydrated zinc acetate and 28 mg of ethanolamine in 1 ml of ethylene glycol ether; the PFN-Br solution used methanol as solvent with a concentration of 1 mg / ml;

[0079] S2-1. Take 10 μL PC 61 BM solution was spin-coated at 1500 rpm to obtain PC 61 BM layer;

[0080] Among them, PC 61 The solvent used for BM solution was chlorobenzene, with a concentration of 20 mg / ml;

[0081] S2-2. The small molecule donor B1 and the non-fullerene small molecule acceptor BTP-eC9 were mixed (10:1, wt / wt) and dissolved in chloroform to ensure that the concentration of the solute in the mixed solution was 30 mg / ml, and then fully shaken and placed at room temperature for use;

[0082] The structures of B1 and BTP-eC9 are as follows Figure 2 As shown;

[0083] S2-3. 150 mL of ethylene glycol was placed in a square culture dish, and 10 μL of the mixed solution was dropped on the contact interface between ethylene glycol and the square culture dish. The mixed solution rapidly diffused and expanded in a strip-like form, forming a strip-like film on the surface of the liquid matrix;

[0084] S2-4. Transferring the film from the liquid matrix to the PC by transfer printing 61 On the BM layer, and drying treatment is performed to obtain a photoactive layer with optical anisotropy;

[0085] S3. Deposit the hole transport layer on the photoactive layer by vacuum evaporation: The prepared sample is placed on an effective area of 0.047 cm 2 In the mask, the vacuum degree is 5×10 -4 Pa, 10nmMoO3 was evaporated at a speed of 0.1nm / s;

[0086] S4. Ag was deposited on the hole transport layer as the anode by vacuum evaporation: at a vacuum of 5×10-4 Under the condition of [[Pa]], Ag with a thickness of 100 nm was evaporated at a speed of 0.1 nm / s to obtain a fully small-molecule linearly polarized light photodetector assisted by small liquid crystal molecules for orientation.

[0087] Comparative Example 1

[0088] A photodetector, the difference between this comparative example and Example 1 is that the material of the active layer is TQ1:Y6 (10:1, wt / wt), and other structural designs are the same as those in Example 1.

[0089] Test Example

[0090] Performance tests were carried out on the photodetectors of Examples 1-3 and Comparative Example 1.

[0091] Current anisotropy ratio test method: Construct a vertical optical path structure of light source - polarizer - sample, so that 605 nm and 850 nm light sources generate linearly polarized light through polarization modulation. Use Keithley 2600 to determine the extreme values of current density by real-time monitoring of the transient current response, fix the sample for steady-state J-V characteristic testing, and then rotate the sample 90° to the orthogonal orientation to record the minimum value of the J-V curve. Finally, calculate the current anisotropy ratio according to the I max / I min ratio.

[0092] The test results are shown in Table 1.

[0093] Table 1 Performance test results of the photodetectors of Examples 1-3 and Comparative Example 1

[0094]

[0095] It can be seen from Table 1 that the devices of the three examples have polarization-sensitive characteristics in visible light (605 nm) and near-infrared light (850 nm), especially in near-infrared light, the current polarization ratio can reach nearly 3; compared with Comparative Example 1, the current anisotropy ratios of the three examples are better; Figures 6 - 10 The J-V diagrams, external quantum efficiency diagrams, and time-response diagrams of Example 1 under 605 nm and 850 nm light illumination are shown respectively. It can be seen that the device has good performance, high photoelectric conversion efficiency and fast speed.

[0096] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

[0097] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A fully small-molecule linearly polarized light photodetector assisted by a liquid crystal small molecule, characterized in that, The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules includes the following structure: a cathode, an electron transport layer, a photoactive layer, a hole transport layer, and an anode; Among them, the material of the photoactive layer includes a P-type liquid crystal small molecule material and an N-type small molecule acceptor material; The material of the P-type liquid crystal small molecule includes, but is not limited to, one or more of BTR, BTR-Cl, and B1; The materials of the N-type small molecule acceptor include but are not limited to Y6, L8-BO, BTP-eC9, PC 61 BM and PC 71 one or more of BM.

2. The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to claim 1, wherein The content of the P-type liquid crystal small molecule material is not less than 10 wt%.

3. The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to claim 1, wherein The material of the electron transport layer includes, but is not limited to, one or more of ZnO, PFN-Br, and PNDIT-F3N.

4. The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to claim 1, wherein The material of the hole transport layer includes, but is not limited to, one or more of MoO3, PEDOT:PSS, WO3, PVK, TPD, Spiro-TPD, and NPD.

5. The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to claim 1, characterized in that The thickness of the photoactive layer is 5 - 500 nm.

6. The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to claim 1, wherein The incident direction of the optical signal is the cathode or the anode.

7. The all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to claim 1, wherein The preparation method of the photoactive layer includes one or more of spin coating method, floating film transfer method, high-temperature rubbing method, mechanical stretching method, and blade scraping method.

9. Application of the all-small-molecule linearly polarized light photodetector assisted by liquid crystal small molecules according to any one of claims 1 - 7 in the field of semiconductor materials.

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