A method for preparing a heterojunction green light detector of a subphthalocyanine derivative

Abstract

The present invention relates to a heterojunction type green light detector of a subphthalocyanine derivative and a preparation method thereof. The subphthalocyanine derivatives are divided into a P-type subphthalocyanine and three N-type subphthalocyanines, and all are sensitive to green light. The heterojunction in the photodetector comprises adjacent P-type subphthalocyanine thin films and N-type subphthalocyanine thin films, a hole transport layer PEDOT:PSS and a transparent conductive substrate ITO glass are sequentially arranged on one side of the P-type subphthalocyanine thin film, and an electron transport layer C is sequentially arranged on one side of the N-type subphthalocyanine thin film. 60 , electronic buffer layer LiF and metal back electrode Ag. The subphthalocyanine derivatives described in the present invention have a larger transition dipole moment in the molecule than subphthalocyanine. The photosensitive layer based on the P / N heterojunction type helps the hole-electron pairs to achieve efficient dissociation and accelerate the transport of carriers under the action of the built-in electric field, thereby improving the photocurrent, photoresponsivity and photodetection rate of the photodetector.

Description

[Technical field]

[0001] The invention belongs to the technical field of photoelectric detectors and relates to a method for preparing a heterojunction visible light photoelectric detector of a subphthalocyanine derivative.

Technical Background

[0002] In recent years, photodetectors (OPDs) have attracted widespread attention in the fields of digital imaging technology, sensing, communication technology, artificial intelligence, etc. due to their inherent mechanical flexibility, easy processing, good light sensing performance and biocompatibility. Photodetectors in different wavelength regions play an important role in various optoelectronic technology fields. For example: ultraviolet band detection is mainly used for environmental monitoring, biomedicine, space detection, etc.; infrared band detection is mainly used for night vision, infrared thermal imaging and infrared remote sensing, etc.; visible light band can be used in many military and civilian fields such as photometry, medical imaging, optical communication, artificial intelligence, etc., especially in the optoelectronic field related to vision systems. Therefore, the development of high-performance visible light photodetectors is of great significance to the development of science and technology.

[0003] Commonly used photosensitive materials in photodetectors include inorganic materials and organic materials, but most inorganic semiconductor materials are not conducive to wavelength-selective photodetection due to their wide absorption spectra from visible light to infrared regions. There are many types of organic materials, and the molecular structure can be flexibly designed to adjust the physicochemical properties of the materials, thus making up for the shortcomings of inorganic materials. Organic subphthalocyanine (SubPc) material is one of the most popular phthalocyanine compounds in recent years. It not only has chemical stability similar to phthalocyanine, but its unique near-planar cone structure makes it have nonlinear optical properties that are superior to general planar molecules (such as phthalocyanine) and linear molecules; in addition, subphthalocyanine materials can flexibly introduce axial functional groups and ring peripheral substituent groups to adjust their own molecular structure, and effectively regulate the energy level through material modification, thereby optimizing the photoelectric effects of the material. At the same time, in order to achieve high-performance visible light photodetectors, heterojunctions formed using similar materials can achieve effective separation of excitons, so that the photoelectric gain and responsivity of the device are synergistically increased. [Summary of the invention]

[0004] The present invention aims to provide a method for preparing a heterojunction type green light detector of a subphthalocyanine derivative. The subphthalocyanine derivative heterojunction photodetector comprises a P-type subphthalocyanine film and an N-type subphthalocyanine film arranged adjacent to each other. When the heterojunction is formed, hole-electron pairs are more easily dissociated under the action of a built-in electric field and carrier transport is accelerated, thereby improving the photocurrent, photoresponsivity and photodetection rate of photodetection.

[0005] The technical solution of the present invention:

[0006] 1. Preparation process of heterojunction green light detector of subphthalocyanine derivatives:

[0007] The ITO glass substrate is used as the anode, the PEDOT:PSS spin-coated on the substrate is used as the hole transport layer, the P-type subphthalocyanine derivative and the N-type subphthalocyanine derivative evaporated on the PEDOT:PSS are used as the photosensitive layer, and the C 60 As the electron transport layer, it was evaporated on C 60 The LiF on the surface is used as an electron buffer layer, and the metal Ag evaporated on the LiF is used as a cathode. The P-type subphthalocyanine film is Br-BsubPc, and its molecular structure is as follows Figure 1-1 The chemical formula of the N-type subphthalocyanine is X-BsubPcF 12 , where X is a phenoxy group, an aldehyde group and a nitro group, and its molecular structure is as follows Figure 1-2 shown.

[0008] The device structure of the prepared subphthalocyanine derivative heterojunction green light detector is:

[0009] Device 1: ITO / PEDOT:PSS / Br-BSubPc / NO2-Pho-BSubPcF 12 / C 60 / LiF / Ag

[0010] Device 2: ITO / PEDOT: PSS / Br-BSubPc / CHO-Pho-BSubPcF 12 / C 60 / LiF / Ag

[0011] Device 3: ITO / PEDOT:PSS / Br-BSubPc / Pho-BSubPcF 12 / C 60 / LiF / Ag

[0012] The specific steps for making a photodetector are as follows:

[0013] (1) The ITO glass substrate was ultrasonicated in acetone, isopropanol, and deionized water for 15 minutes respectively, and then dried in an infrared drying oven;

[0014] (2) placing the cleaned ITO glass substrate in a UV ozone apparatus for surface hydrophilic treatment for 15 minutes;

[0015] (3) Spin coating PEDOT:PSS on the hydrophilic ITO glass substrate at a speed of 3000 rpm for 30 s, and then annealing on a hot stage at 120°C for 20 min;

[0016] (4) Vacuum evaporation method was used on PEDOT:PSS film to form a 5x10 -5 Pa, the deposition rate of P-type subphthalocyanine was 1 nm / s and the thickness was 50 nm.

[0017] (5) Vacuum evaporation method was used on P-type subphthalocyanine film to form a 5x10 -5 Pa, N-type subphthalocyanine was evaporated at a deposition rate of 1 nm / s and a thickness of 30 nm;

[0018] (6) Vacuum evaporation method was used on N-type subphthalocyanine film to form a 5x10 -5 Pa pressure evaporated electron transport layer C 60 , deposition rate is 1nm / s, thickness is 33nm;

[0019] (7) In C 60 The film was deposited by vacuum evaporation at 5x10 -5 The electronic buffer layer LiF was evaporated at a pressure of Pa, with a deposition rate of 0.1nm / s and a thickness of 1nm;

[0020] (8) Using vacuum evaporation method on the electron transport layer LiF thin film, 5x10 -5 The metal cathode Ag was evaporated at a pressure of Pa with a deposition rate of 3nm / s and a thickness of 120nm.

[0021] 2. The subphthalocyanine derivative heterojunction green light detector was tested and characterized by the following methods:

[0022] (1) The UV-visible absorption test of the subphthalocyanine derivative thin film spin-coated on the quartz glass substrate was carried out using a UV-2501PC UV-visible spectrophotometer. From the test results, it can be seen that the absorption peaks of the four subphthalocyanine materials are all located in the green light wavelength range, which also provides the possibility of making photodetectors using the selective absorption characteristics of light.

[0023] (2) The prepared photodetector device was placed on the spectral response test system (IPCE) of QEM24-S to test the photocurrent, photoresponsivity and photodetection rate of the detector under green excitation light.

[0024] 3. Compared with the prior art, the present invention has the following advantages:

[0025] (1) The axial and peripheral electron-withdrawing groups of this type of subphthalocyanine derivative disperse the electron cloud of the material, and the transition dipole moment is larger than that of traditional subphthalocyanine, making it easier for hole-electron pairs to dissociate under the excitation of the light field.

[0026] (2) Traditional P / N heterojunctions are composed of different types of materials. The contact characteristics at the heterojunction interface are often poor, which easily leads to defects that capture photogenerated carriers, resulting in leakage current and reducing the transport efficiency of photogenerated carriers. However, the P / N heterojunction formed by the same type of materials has a similar molecular structure, which makes the heterojunction interface more tightly bonded, forming a good interface contact, which can effectively improve the transport efficiency of photogenerated carriers.

[0027] (3) When this type of subphthalocyanine derivative forms a P / N heterojunction, a large built-in electric field will be formed in the depletion layer at the interface. The direction of the electric field is opposite to that of the external electric field, which is conducive to the dissociation of excitons. Compared with the existing technology, the HOMO energy level difference between the P-type subphthalocyanine and the hole transport layer and the LUMO energy level difference between the N-type subphthalocyanine and the electron transport layer are smaller, and the energy level structure is more optimized, which can effectively improve the photocurrent, photoresponsivity and photodetection rate of the device.

[0028] (4) The photodetector has a simple preparation process, low cost, small size, high stability, and can be prepared on a flexible substrate. [Specific implementation method]

[0029] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0030] Embodiment 1:

[0031] The schematic diagram of the structure of the heterojunction green light detector of the subphthalocyanine derivative of the present invention is as follows Figure 2 As shown in the figure, the heterojunction green light detector of the subphthalocyanine derivative is composed of the following from bottom to top: transparent conductive substrate, hole transport layer, P-type subphthalocyanine, N-type subphthalocyanine, electron transport layer, electron buffer layer and metal cathode. The heterojunction is adjacent to the hole transport layer and the electron transport layer, wherein the P-type subphthalocyanine is adjacent to the hole transport layer, and the N-type subphthalocyanine is adjacent to the electron transport layer. The structure of the prepared device is:

[0032] Device 1: ITO / PEDOT:PSS / Br-BSubPc / NO2-Pho-BSubPcF 12 / C 60 / LiF / Ag

[0033] Device 2: ITO / PEDOT: PSS / Br-BSubPc / CHO-Pho-BSubPcF 12 / C 60 / LiF / Ag

[0034] Device 3: ITO / PEDOT:PSS / Br-BSubPc / Pho-BSubPcF 12 / C 60 / LiF / Ag

[0035] The preparation method of a heterojunction green light detector of a subphthalocyanine derivative comprises the following steps:

[0036] (1) The ITO glass substrate was ultrasonicated in acetone, isopropanol, and deionized water for 15 minutes respectively, and then dried in an infrared drying oven;

[0037] (2) Place the cleaned ITO glass substrate in a UV ozone apparatus for surface hydrophilic treatment for 15 minutes;

[0038] (3) Spin coating PEDOT:PSS on the hydrophilic ITO glass substrate at a speed of 3000 rpm for 30 s, and then annealing on a hot stage at 120°C for 20 min;

[0039] (4) Vacuum evaporation method was used on PEDOT:PSS film to form a 5x10 -5 Pa, the deposition rate of P-type subphthalocyanine was 1 nm / s and the thickness was 50 nm.

[0040] (5) Vacuum evaporation method was used on P-type subphthalocyanine film to form a 5x10 -5 Pa, N-type subphthalocyanine was evaporated at a deposition rate of 1 nm / s and a thickness of 30 nm;

[0041] (6) Vacuum evaporation method was used on N-type subphthalocyanine film to form a 5x10 -5 Pa pressure evaporated electron transport layer C 60 , deposition rate is 1nm / s, thickness is 33nm;

[0042] (7) In C 60 The film was deposited by vacuum evaporation at 5x10 -5 The electronic buffer layer LiF was evaporated at a pressure of Pa, with a deposition rate of 0.1nm / s and a thickness of 1nm;

[0043] (8) Using vacuum evaporation method on the electron transport layer LiF thin film, 5x10 -5 The metal cathode Ag was evaporated at a pressure of Pa with a deposition rate of 3nm / s and a thickness of 120nm.

[0044] Embodiment 2:

[0045] The UV-visible absorption spectrum of the subphthalocyanine derivative thin films spin-coated on a quartz substrate was tested. Figure 3The UV-visible absorption spectrum of subphthalocyanine derivative materials is shown. It can be seen from the figure that the absorption peak of P-type subphthalocyanine is 576nm, and the absorption peaks of the three N-type subphthalocyanines are 563nm, 570nm and 574nm respectively. Its higher absorption coefficient indicates that it has good application value in photodetectors.

[0046] Embodiment 3:

[0047] During the testing of the photodetector, 560nm excitation light is emitted into the photodetector from one side of the transparent conductive substrate. Figure 4 The light and dark currents of the subphthalocyanine derivative heterojunction green photodetector (devices 1-3) in the dark state and under illumination are shown. As can be seen from the figure, all three devices show large photocurrents under 560nm wavelength illumination. Figure 5 The photocurrent response diagram of the subphthalocyanine derivative heterojunction green light detector device is shown. It can be seen that this type of detector has a good photocurrent response. The photocurrents of devices 1-3 are 3.38μA, 2.54μA and 2.35μA respectively. It is calculated that the photoresponsivity of devices 1-3 is 1.69x10 -2 A / W, 1.43x10 -2 A / W and 1.09x10 -2 A / W; the light detection rates of devices 1-3 are: 1.9x10 12 cm·Hz 1 / 2 / W, 1.43x10 12 cm·Hz 1 / 2 / W and 1.09x10 12 cm·Hz 1 / 2 / W. From the above results, it can be seen that device 1 exhibits the best green light detection effect.

[0048] Comparative Example 1:

[0049] The specific implementation contents are the same as those of Example 1 except that the N-type subphthalocyanine material is not included:

[0050] The structure of the device 4 is: ITO / PEDOT:PSS / Br-BSubPc / C 60 / LiF / Ag.

[0051] Depend on Figure 5 It can be seen that the photocurrent of device 4 is 0.9μA. The photoresponsivity of device 4 is calculated to be 0.45x10 -2 A / W, light detection rate is 0.46x10 12 cm·Hz 1 / 2 / W. By comparison, it can be seen that the photoelectric detection characteristics of devices 1-3 are significantly improved compared with device 4. Among them, the photocurrent, photoresponsivity and photodetection rate of device 1 are improved by 275%, 283% and 313% respectively compared with device 4.

[0052] The above results show that device 1 has the best green light detection performance. This is because the axial substituent of the N-type subphthalocyanine derivative in device 1 is a nitro group, which has the strongest electron-withdrawing ability among the three, and can reduce the conjugated electron cloud density of the subphthalocyanine to a greater extent, thereby increasing the transition dipole moment and exciton dissociation efficiency of the material. Compared with device 4, the P-type subphthalocyanine and the N-type subphthalocyanine form a P / N heterojunction, which further enhances the efficiency of photogenerated carriers at the heterojunction interface. From the energy level structure diagram of the device ( Figure 6 ) can be seen that the HOMO energy difference between P-type subphthalocyanine and PEDOT:PSS is about 0.2eV, and that between N-type subphthalocyanine and C 60 The LUMO energy difference is about 0.5 eV, and a more appropriate energy level matching is conducive to the transmission of photogenerated carriers, thereby improving the overall performance of the device. The above results show that heterojunction photodetectors based on such subphthalocyanine derivatives have broad application prospects in the field of visible light detection.

Brief Description of the Drawings

[0053] Figure 1 is a schematic diagram of the structure of the subphthalocyanine derivative of the present invention;

[0054] Figure 2 It is a schematic diagram of the structure of the optical detection device of the present invention;

[0055] Figure 3 It is the UV-visible absorption spectrum of the subphthalocyanine derivative material;

[0056] Figure 4 The photocurrent spectra of the subphthalocyanine derivative heterojunction green light detector in the dark state and under 560nm wavelength illumination;

[0057] Figure 5 It is a subphthalocyanine derivative heterojunction type green light detector and a photocurrent response spectrum of the subphthalocyanine derivative green light detector;

[0058] Figure 6 Schematic diagram of the energy levels of the photodetector device of the present invention.

Claims

1. A heterojunction green light detector of a subphthalocyanine derivative, characterized in that: The heterojunction green light detector of the subphthalocyanine derivative comprises a P-type subphthalocyanine film and an N-type subphthalocyanine film of the same material arranged adjacently, wherein the material of the P-type subphthalocyanine film is Br-BSubPc, and the material of the N-type subphthalocyanine film is NO2-Pho-BSubPcF 12 ; A hole transport layer is provided on the side of the P-type subphthalocyanine film facing away from the N-type subphthalocyanine film, and a transparent conductive substrate is provided on the side of the hole transport layer facing away from the P-type subphthalocyanine film; an electron transport layer and an electron buffer layer are provided on the side of the N-type subphthalocyanine film facing away from the P-type subphthalocyanine film, and a metal electrode is provided on the side of the electron buffer layer facing away from the N-type subphthalocyanine film.

2. The heterojunction green light detector of a subphthalocyanine derivative according to claim 1, characterized in that The transparent conductive substrate is ITO glass, ITO is a conductive anode, and its square resistance is 20-30Ω. The required ITO glass substrate is cleaned, dried and pre-treated.

3. According to the heterojunction green light detector of a subphthalocyanine derivative as claimed in claim 1, the hole transport layer is a PEDOT:PSS thin film, which is spin-coated on an ITO glass substrate using a solution method and has a film thickness of 50 nm.

4. The heterojunction green light detector of a subphthalocyanine derivative according to claim 1, characterized in that The thickness of the P-type subphthalocyanine film is 50 nm, and the thickness of the N-type subphthalocyanine film is 30 nm. Both subphthalocyanine films are prepared by vacuum thermal evaporation.

5. The heterojunction green light detector of a subphthalocyanine derivative according to claim 1, characterized in that The electron transport layer is a fullerene material C 60 , with a film thickness of 25 nm; the electron buffer layer material adjacent to the electron transport layer is LiF, with a film thickness of 1 nm; the electron transport layer and the electron buffer layer are both prepared by vacuum thermal evaporation. 6 . The heterojunction green light detector of a subphthalocyanine derivative according to claim 5 , wherein the metal electrode is a Ag thin film, which is evaporated on LiF after being shielded by a mask plate, and the film thickness is 100 nm.

7. A heterojunction green light detector of a subphthalocyanine derivative according to any one of claims 1 to 6, characterized in that The detector preparation process includes the following steps: (1) preparing a hole transport layer on a transparent conductive substrate; (2) evaporating a P-type subphthalocyanine thin film on the surface of the hole transport layer obtained in step (1); (3) evaporating an N-type subphthalocyanine film on the P-type subphthalocyanine film obtained in step (2); (4) evaporating an electron transport layer on the N-type subphthalocyanine film obtained in step (3); (5) Vapor depositing an electron buffer layer on the electron transport layer obtained in step (4).

8. The heterojunction green light detector of a subphthalocyanine derivative according to claim 1, characterized in that The wavelength detection range of the prepared detector is 520-580nm.

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