Near-infrared organic photoelectric detector based on carbazole derivative and application thereof

Abstract

The invention relates to a near-infrared organic photoelectric detector based on a carbazole derivative. A hole transport layer of the near-infrared organic photoelectric detector is the carbazole derivative; wherein the carbazole derivative is formed by connecting an alkyl chain with carboxylic acid to a carbazole N atom. When the hole transport layer adopts the carbazole derivative modified by carboxylic acid, the photoresponsiveness of the photosensitive layer in a near-infrared region can be obviously improved, and the intensity of the photosensitive layer even exceeds the photoresponse intensity of the photosensitive layer in a range of 700-950 nm. The defect that a near-infrared detector in the prior art is weak in response in a near-infrared band is greatly overcome. In addition, the near-infrared detector also has an excellent light and dark current ratio under bias voltage, which is mainly benefited from an extremely low dark current value. Data show that after the near-infrared detector is placed in the air for a long time, the performance of the near-infrared detector is slightly reduced. This shows that the device also has excellent stability.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic devices, and in particular relates to a near-infrared organic photodetector based on carbazole derivatives and applications thereof. Background Art

[0002] A photodetector is a device that converts light signals into electrical signals. Its function is to effectively convert light signals into electrical signals. This feature makes it widely used in many fields, including health monitoring, optical communications, image sensing, and industrial automation. Compared with other types of photodetectors, organic photodetectors have shown incomparable unique advantages in specific application scenarios and system integration due to their excellent lightweight characteristics, cost-effective manufacturing costs, and excellent flexible design.

[0003] In organic photodetectors of upright or flip-chip devices, the hole transport layer plays an important role. The hole transport layer can adjust the work function of ITO, block the recombination of carriers and regulate the crystallization of the photosensitive layer. PEDOT:PSS is widely used as a star polymer for the hole transport layer, but PEDOT:PSS has serious water absorption and corrosion of the device substrate due to the presence of sulfonic acid groups, which is not conducive to future applications. In addition, batch differences in polymers also affect the yield of the device. In the past few years, self-assembled molecules, as a single-layer material for hole transport, have shown broad application prospects due to their low optical and electrical losses and easy modulation of energy levels. Considering the commercial application of photodetectors, the self-assembled monolayer used must be simple to synthesize, low in cost, and able to guarantee the performance of the photodetector and have good stability.

[0004] In the prior art of solar cell devices, some people have adopted carbazole-based hole transport layer structures. For example, the perovskite solar cell device of CN117337115A uses carboxylic acid-modified carbazole as the hole transport layer, and obtains excellent photoelectric conversion efficiency, reaching up to 23.4%; the perovskite solar cell of CN114716476A uses phosphoric acid-modified carbazole as the hole transport layer, and its photoelectric conversion efficiency also exceeds 20%.

[0005] However, the above existing technologies only illustrate that carbazole derivatives can greatly improve the photoelectric efficiency as a hole transport layer in perovskite solar cells. As another important branch of optoelectronic devices, near-infrared photodetectors focus on parameters that are completely different from perovskite cells. That is, we pay more attention to the parameters of the light response and sensitivity of near-infrared photodetectors in the near-infrared band, which is different from the spectral absorption and response of the short-wavelength band that solar cells focus on. At present, copying the technology of solar cells to the field of near-infrared photodetectors has also encountered many barriers and cannot solve the problems we are concerned about.

[0006] In summary, there is an urgent need to develop a new technical solution to solve the problems existing in the existing technology and meet the development needs of the current market. Summary of the invention

[0007] Based on this, the present invention discloses a near-infrared organic photodetector based on carbazole derivatives, wherein the hole transport layer is a carbazole derivative;

[0008] The carbazole derivative is an alkyl chain with a carboxylic acid connected to the N atom of the carbazole.

[0009] Furthermore, the carbazole derivative is selected from one of 3-carbazole acetic acid, 3-carbazole propionic acid, 3-carbazole butyric acid, 3-carbazole valeric acid or 3-carbazole hexanoic acid, or a mixture of the above materials.

[0010] Furthermore, the near-infrared organic photodetector based on carbazole derivatives further includes a photosensitive layer, wherein the photosensitive layer includes a blended structure of a p-type material and an n-type material;

[0011] The p-type material is selected from materials having an optical band edge of an absorption spectrum exceeding 1000 nm;

[0012] The p-type material is selected from organic small molecule materials or organic polymer materials.

[0013] Furthermore, the n-type material is selected from PCBM materials, organic small molecule materials or organic polymer materials.

[0014] Furthermore, the near-infrared organic photodetector based on carbazole derivatives is selected from a face-up structure or a flip-down structure.

[0015] Furthermore, the thickness of the hole transport layer is 3-30 nm.

[0016] Furthermore, the near-infrared organic photodetector based on carbazole derivatives also includes an electron transport layer, an anode and a cathode.

[0017] Furthermore, the n-type material is selected from one or more of COTIC-4F and Y6.

[0018] Another object of the present invention is to disclose the application of the above-mentioned near-infrared organic photodetector based on carbazole derivatives in the field of near-infrared detection.

[0019] The beneficial effects of the present invention are:

[0020] The present invention uses self-assembled monomolecular materials as core components, which exhibit excellent hole transport performance, comparable to commercial materials such as PEDOT:PSS and 2PACz that are widely used in the current market, and even surpasses them in some key performance indicators. This breakthrough not only verifies the great potential of self-assembled monomolecular materials in the field of photodetectors, but also provides the possibility of replacing traditional expensive or performance-limited materials.

[0021] Specifically, the photosensitive layer of the present invention uses a p-type material with an absorption band edge exceeding 1000nm, and is blended with a small molecule n-type material. Surprisingly, it is found that when the hole transport layer of the present invention uses a carboxylic acid-modified carbazole derivative, the light responsiveness of the photosensitive layer in the near-infrared region is significantly improved. Specifically, it is reflected in the EQE value and the intensity of the specific detection rate, and its intensity even exceeds the EQE value and the intensity of the specific detection rate in the range of 700-950nm. This greatly makes up for the defect that the near-infrared detector in the prior art has a weak response in the near-infrared band.

[0022] In addition, the near-infrared detector has an excellent light-to-dark current ratio under bias, which is mainly due to its extremely low dark current value. Data show that the performance of the near-infrared detector decreases slightly after being placed in the air for a long time, which shows that the device also has excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The structures of the materials involved in the examples are shown.

[0024] Figure 2 The device structure of the near-infrared organic photodetector based on the carbazole derivative in the embodiment is shown. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solution of the present invention, the following examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0026] It should be understood that, except in any operating examples, or where otherwise indicated, all numbers expressing, for example, the amounts of ingredients used in the specification and claims should be understood to be modified in all instances by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary depending on the desired properties to be obtained by the present invention.

[0027] The carboxylic acid carbazole derivatives in the examples of the present invention were synthesized in the laboratory according to the literature; PTB7-Th, COTIC-4F and Y6 are all commercial materials.

[0028] Example 1

[0029] A near-infrared organic photodetector based on a carbazole derivative, the structure of which is as follows Figure 2 From bottom to top, it includes: a semi-transparent anode (ITO, 150nm), a hole transport layer (3-carbazoleacetic acid, 10nm), a photosensitive layer (PTB7-Th:COTIC-4F+Y6, 200nm), an electron transport layer (C60, 20nm), and a cathode (silver, 100nm).

[0030] Among them, the mass ratio of p-type material to n-type material is 1:1.5; the mass ratio of COTIC-4F to Y6 is 2:1.

[0031] The preparation process of the above-mentioned near-infrared organic photodetector based on carbazole derivatives is as follows:

[0032] S1. First, ultrasonically clean the glass substrate with ITO with isopropanol, then ultrasonically clean it with deionized water and detergent, then repeat the ultrasonic cleaning with deionized water three times, and finally ultrasonically clean it again with isopropanol, and put it in an oven to dry for later use;

[0033] S2, performing oxygen plasma treatment on the glass substrate with ITO for 3 min;

[0034] S3, spin-coat the prepared 1 mol / L 3-carbazole acetic acid solution (solvent is ethanol) onto the ITO glass substrate treated in S2, at a spin-coating speed of 3000 rpm and a spin-coating time of 30 s, then spin-coat ethanol onto the sample at a spin-coating speed of 6000 rpm and a spin-coating time of 20 s, repeat twice, and anneal on a hot plate at 70°C for 30 min to obtain a hole transport layer;

[0035] S4, spin-coat the prepared 25 mg / mL photosensitive layer solution (the solvent is chlorobenzene, and 2 wt% of chloronaphthalene additive is added) on the hole transport layer obtained in S3. The spin coating process is step-by-step spin coating, first at 800 rpm for 40 seconds, then at 2000 rpm for 20 seconds, and transfer the sample to a 100°C hot stage for annealing for 10 minutes. Then transfer the sample to a vacuum chamber and evacuate for 2 hours;

[0036] S5, transferring the sample to a vacuum evaporation system, and evaporating a C60 electron transport layer on the photosensitive layer;

[0037] S6. Transfer the above sample to a vacuum evaporation system, and evaporate a layer of metallic silver on the electron transport layer as a cathode to obtain a device.

[0038] Example 2

[0039] A near-infrared organic photodetector based on a carbazole derivative, the structure of which is as follows Figure 2 From bottom to top, it includes: a semi-transparent anode (ITO, 150nm), a hole transport layer (3-carbazole propionic acid, 5nm), a photosensitive layer (PTB7-Th:COTIC-4F+Y6, 200nm), an electron transport layer (C60, 20nm), and a cathode (silver, 100nm).

[0040] Among them, the mass ratio of p-type material to n-type material is 1:1; the mass ratio of COTIC-4F to Y6 is 2:1.

[0041] The preparation method thereof is referred to Example 1.

[0042] Example 3

[0043] A near-infrared organic photodetector based on a carbazole derivative, the structure of which is as follows Figure 2 From bottom to top, it includes: a semi-transparent anode (ITO, 150nm), a hole transport layer (3-carbazole valeric acid, 5nm), a photosensitive layer (PTB7-Th:COTIC-4F+Y6, 200nm), an electron transport layer (C60, 20nm), and a cathode (silver, 100nm).

[0044] Among them, the mass ratio of p-type material to n-type material is 1:1.2; the mass ratio of COTIC-4F to Y6 is 2:1.

[0045] The preparation method thereof is referred to Example 1.

[0046] Comparative Example 1

[0047] The materials, device structure and preparation method used in Comparative Example 1 are the same as those in Example 1. The only difference is that the photosensitive layer in Comparative Example 1 is made of perovskite Cs0.15 FA 0.85 Pb 0.5 Sn 0.5 I 3 .

[0048] Comparative Example 2

[0049] The materials, device structure and preparation method used in Comparative Example 2 are the same as those in Example 1, with the only difference being that the hole transport layer in Comparative Example 2 uses PEDOT:PSS.

[0050] Test Case

[0051] The performance of the near-infrared organic photodetectors based on carbazole derivatives prepared in Examples 1-3 and Comparative Examples 1-2 was tested.

[0052] Test method:

[0053] The optical test methods used in the examples and comparative examples of the present invention are all well known to those skilled in the art. The results are shown in Table 1.

[0054] Table 1 Performance test results of near-infrared organic photodetectors based on carbazole derivatives

[0055]

[0056] It can be clearly seen from the data in Table 1 that the EQE value and the specific detection rate of Examples 1-3 in the near-infrared band are higher than the intensity at 860nm. However, the EQE value and the specific detection rate in the near-infrared band of Comparative Example 2 are significantly attenuated, which shows that the introduction of the hole transport layer of the present invention has a significant positive effect on maintaining the intensity of the EQE and the specific detection rate in the near-infrared band.

[0057] More obviously, after 4 months, the EQE value of the same band was tested again, and it was found that the attenuation behavior of Comparative Examples 1-2 was very significant, while Examples 1-3 had almost no negative attenuation results. This shows that the hole transport layer of the present invention has a more obvious effect on the service life of the device.

[0058] From the light-to-dark current ratio and dark current of the device working under -0.1V bias, the hole transport layer of the present invention is also very effective in suppressing dark current and maintaining a high light-to-dark current ratio. 5 This is an extremely important parameter for near-infrared detectors.

[0059] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0060] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A near-infrared organic photodetector based on a carbazole derivative, characterized in that: The hole transport layer of the near-infrared organic photodetector based on carbazole derivatives is a carbazole derivative; The carbazole derivative is an alkyl chain with a carboxylic acid connected to the N atom of the carbazole.

2. The near-infrared organic photodetector based on carbazole derivatives according to claim 1, characterized in that: The carbazole derivative is selected from one of 3-carbazole acetic acid, 3-carbazole propionic acid, 3-carbazole butyric acid, 3-carbazole valeric acid or 3-carbazole hexanoic acid or a mixture of the above materials.

3. The near-infrared organic photodetector based on carbazole derivatives according to claim 1, characterized in that: The near-infrared organic photodetector based on carbazole derivatives further includes a photosensitive layer, wherein the photosensitive layer includes a blended structure of a p-type material and an n-type material; The p-type material is selected from materials having an optical band edge of an absorption spectrum exceeding 1000 nm; The p-type material is selected from organic small molecule materials or organic polymer materials.

4. The near-infrared organic photodetector based on carbazole derivatives according to claim 3, characterized in that: The n-type material is selected from PCBM materials, organic small molecule materials or organic polymer materials.

5. The near-infrared organic photodetector based on carbazole derivatives according to claim 1, characterized in that: The near-infrared organic photodetector based on carbazole derivatives is selected from a face-up structure or a face-down structure.

6. The near-infrared organic photodetector based on carbazole derivatives according to claim 1, characterized in that: The thickness of the hole transport layer is 3-30 nm.

7. The near-infrared organic photodetector based on carbazole derivatives according to claim 1, characterized in that: The near-infrared organic photodetector based on carbazole derivatives further includes an electron transport layer, an anode and a cathode.

8. The near-infrared organic photodetector based on carbazole derivatives according to claim 3, characterized in that: The n-type material is selected from one or more of COTIC-4F and Y6.

9. Use of the near-infrared organic photodetector based on the carbazole derivative according to any one of claims 1 to 8 in the field of near-infrared detection.

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