A thermionic photodetector and a preparation method and application thereof

Abstract

The application discloses a kind of hot electron photodetector and preparation method and application thereof.The composition of the hot electron photodetector of the application includes the light-transmitting substrate, the light-transmitting anode layer, the organic semiconductor layer, the electron injection layer and the cathode layer which are sequentially stacked.The preparation method of the hot electron photodetector of the application includes the following steps:1) covering anode material on the single side of the light-transmitting substrate to form the light-transmitting anode layer;2) using thermal evaporation method to deposit the organic semiconductor layer, the electron injection layer and the cathode layer on the surface of the light-transmitting anode layer in sequence, and the hot electron photodetector is obtained.The hot electron photodetector of the application can realize wide spectral band response from ultraviolet to near infrared, and its structure is simple, the preparation process is less, the preparation process is simple, and it is suitable for large-scale industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detector, in particular to a thermionic photoelectric detector and a preparation method and application thereof. BACKGROUND

[0002] Photoelectric detectors are widely used in various fields of military and national economy, for example: photoelectric detectors in visible light or near-infrared wave band are mainly used in ray measurement and detection, industrial automatic control, photometric measurement, etc.; photoelectric detectors in infrared wave band are mainly used in missile guidance, infrared thermal imaging, infrared remote sensing, etc. With the development of science and technology and the progress of society, people's demand for photoelectric detectors with flexibility, wide spectral response and high response speed is increasing. The existing photoelectric detectors mainly use organic semiconductor materials (with advantages of flexibility, rich variety, adjustable band gap and low price, etc.) to absorb photons, so the working spectral range is determined by the energy gap of the active layer of organic materials. However, due to the lack of low-energy-gap organic materials and suitable molecular combinations for effective exciton dissociation, few photoelectric detectors in the near-infrared wave band range have been reported.

[0003] Therefore, it is of great significance to develop a photoelectric detector with simple structure and wide spectral response from ultraviolet to near-infrared. SUMMARY

[0004] The present application relates to the technical field of photoelectric detector, in particular to a thermionic photoelectric detector and a preparation method and application thereof.

[0005] The technical scheme adopted by the present application is:

[0006] A thermionic photoelectric detector, which comprises a light-transmitting substrate, a light-transmitting anode layer, an organic semiconductor layer, an electron injection layer and a cathode layer which are sequentially stacked.

[0007]

[0008] Preferably, the LUMO energy level of the organic semiconductor material in the organic semiconductor layer is close to the work function of the constituent material of the electron injection layer and the cathode layer (easy to produce electron injection).

[0009] Preferably, the light-transmitting substrate is one of a glass substrate, a quartz substrate, a sapphire substrate and a light-transmitting polymer substrate.

[0010] Preferably, the light-transmitting polymer substrate is one of a polyimide film, a polyethylene terephthalate film, a polyethylene terephthalate film and a polyethylene terephthalate film.

[0011] Preferably, the light-transmitting anode layer is one of an indium tin oxide (ITO) thin film, a fluorine-doped tin dioxide (FTO) thin film, and an indium gallium zinc oxide (IGZO) thin film. The light-transmitting substrate and the light-transmitting anode layer facilitate photon transmission and impingement on the cathode layer.

[0012] Preferably, the thickness of the organic semiconductor layer is 50 nm to 200 nm.

[0013] Preferably, the composition of the electron injection layer comprises at least one of LiF, C S F, and Li2O.

[0014] Preferably, the thickness of the electron injection layer is 0.5 nm to 1 nm.

[0015] Preferably, the composition of the cathode layer comprises at least one of Al, Ba, Ca, and Cs.

[0016] A method for preparing the thermionic photodetector as described above comprises the following steps:

[0017] 1) covering an anode material on a single side of the light-transmitting substrate to form a light-transmitting anode layer;

[0018] 2) sequentially depositing an organic semiconductor layer, an electron injection layer, and a cathode layer on the surface of the light-transmitting anode layer by a thermal evaporation method, to obtain the thermionic photodetector.

[0019] A detection device comprising the thermionic photodetector as described above.

[0020] Principle of the present application: The present application utilizes the metal of the cathode layer to absorb incident photons to generate high-energy “hot” electrons, wherein a part of the “hot” electrons reaches the Schottky interface, and the excited-state carriers with sufficient energy can be emitted to the organic semiconductor layer to generate a photocurrent, and the wide spectral band of organic photodetection from ultraviolet to near-infrared can be realized by adjusting the height of the energy barrier.

[0021] Advantages of the present application: The thermionic photodetector of the present application can realize a wide spectral band response from ultraviolet to near-infrared, and has a simple structure, a few preparation procedures, and a simple preparation process, and is suitable for large-scale industrial application.

[0022] Specifically:

[0023] 1) The thermionic photodetector of the present application can realize a wide spectral band response from ultraviolet to near-infrared, and has a very broad application prospect in the field of photodetection;

[0024] 2) The organic semiconductor layer in the thermionic photodetector of the present application can adopt a wide-bandgap organic semiconductor material, which does not affect the response of the device, and widens the types of selectable organic semiconductor materials;

[0025] 3) The thermal electron photodetector of the present application has simple structure, less preparation process and simple preparation process, and is suitable for large-scale industrial application in the field of photodetection. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Part of the device structure and principle of the thermal electron photodetector of Example 1.

[0027] Figure 2 UV-visible light absorption spectrum of the TmPyPB layer in Example 1 and test results of the external quantum efficiency of the thermal electron photodetector under different wavelengths.

[0028] Figure 3 Current density-voltage relationship curve of the thermal electron photodetector of Example 1 under light of wavelength 450 nm, wavelength 520 nm, wavelength 660 nm and wavelength 780 nm.

[0029] Figure 4 External quantum efficiency-voltage relationship curve of the thermal electron photodetector of Example 1 under light of wavelength 450 nm, wavelength 520 nm, wavelength 660 nm and wavelength 780 nm.

[0030] Figure 5 Photovoltage-time normalized curve of the thermal electron photodetector of Example 1 under light of wavelength 450 nm, wavelength 488 nm, wavelength 520 nm, wavelength 660 nm and wavelength 780 nm.

[0031] Figure 6 UV-visible light absorption spectrum of the TPBi layer in Example 2 and spectrum of the light source of wavelength 450 nm.

[0032] Figure 7 External quantum efficiency-voltage relationship curve of the thermal electron photodetector of Example 2 under light of wavelength 450 nm. DETAILED DESCRIPTION

[0033] The present application will be further explained and described below in conjunction with specific embodiments.

[0034] Example 1:

[0035] A thermal electron photodetector (part of the device structure and principle as shown in Figure 1 The thermal electron photodetector is composed of a glass substrate, an ITO layer, an organic semiconductor layer, an electron injection layer and a cathode layer which are sequentially stacked from bottom to top; the organic semiconductor layer is a TmPyPB layer with a thickness of 100 nm; the electron injection layer is a LiF layer with a thickness of 1 nm; and the cathode layer is an Al layer with a thickness of 120 nm.

[0036] The preparation method of the above-mentioned hot electron photodetector is as follows:

[0037] 1) A glass substrate with ITO film deposited on one side (a conventional product on the market, size specification: 32 mm x 32 mm, square resistance: 15 Ω / sq~20 Ω / sq, thickness of ITO film: about 90 nm) was sequentially cleaned with acetone, cleaning agent, deionized water and isopropyl alcohol for 10 min each by ultrasonic cleaning, and then was placed in a vacuum drying oven for drying at 75°C, and was then placed in a vacuum plasma cleaning machine for O2 plasma treatment on the surface of the ITO film for 2 min (to remove organic impurities on the surface of the ITO film and to improve the hydrophilicity of the surface of the ITO film);

[0038] 2) The pretreated glass substrate with ITO film deposited on one side was placed in an anhydrous and anaerobic glove box filled with high-purity nitrogen, and the evaporation material was loaded into a vacuum evaporation chamber, and a mechanical pump and a molecular pump were started, and when the pressure in the evaporation chamber reached 3x10 4 Pa, the hot evaporation of the film was started, and a specific mask was used to sequentially evaporate a TmPyPB layer, a LiF layer and an Al layer, and the thickness of the evaporation layer was monitored in real time by a quartz crystal film thickness detector, thereby obtaining a hot electron photodetector.

[0039] Performance test:

[0040] 1) The ultraviolet-visible light absorption spectrum of the TmPyPB layer in the embodiment and the test result graph of the external quantum efficiency of the hot electron photodetector under different wavelengths are shown in Figure 2 .

[0041] It can be known from Figure 2 that the light with a wavelength of 450 nm~800 nm is not within the absorption range of the TmPyPB layer, but the hot electron photodetector of the embodiment can form a photoelectric response, which indicates that the photoelectric response is not caused by the absorption of the TmPyPB itself.

[0042] 2) The current density-voltage relationship curves of the hot electron photodetector of the embodiment under light with a wavelength of 450 nm, a wavelength of 520 nm, a wavelength of 660 nm and a wavelength of 780 nm in the dark are shown in Figure 3 .

[0043] It can be known from Figure 3 that the current density of the hot electron photodetector of the embodiment under the irradiation of light with different wavelengths under ITO forward bias is greater than that in the absence of light, but the current density under reverse bias is basically the same, which further verifies that the hot electrons are generated by the photoexcitation of the metal, and enter the organic semiconductor layer under the action of the electric field to form a photocurrent.

[0044] 3) The external quantum efficiency (EQE)-voltage relationship curve of the hot electron photodetector of this example under light of wavelength 450 nm, wavelength 520 nm, wavelength 660 nm and wavelength 780 nm is shown in FIG. 3. Figure 4

[0045] As can be seen from FIG. 3, the hot electron photodetector of this example can produce photoelectric response to different light sources under ITO positive bias, and the EQE increases with the increase of electric field. Figure 4

[0046] 4) The photocurrent-time normalized curve of the hot electron photodetector of this example under light of wavelength 450 nm, wavelength 488 nm, wavelength 520 nm, wavelength 660 nm and wavelength 780 nm is shown in FIG. 4. Figure 5

[0047] As can be seen from FIG. 4, the hot electron photodetector of this example can produce photoelectric response to light of wavelength 450 nm, wavelength 488 nm, wavelength 520 nm, wavelength 660 nm and wavelength 780 nm. Figure 5

[0048] Example 2:

[0049] A hot electron photodetector, except that the organic semiconductor layer is replaced from "TmPyPB layer with a thickness of 100 nm" to "TPBi layer with a thickness of 100 nm", and the electron injection layer is replaced from "LiF layer with a thickness of 1 nm" to "Li2O layer with a thickness of 0.5 nm", and the rest is exactly the same as the hot electron photodetector of Example 1.

[0050] Performance test:

[0051] The ultraviolet-visible light absorption spectrum of the TPBi layer in this example and the spectrum of the light source of wavelength 450 nm are shown in FIG. 5, and the external quantum efficiency-voltage relationship curve of the hot electron photodetector of this example under light of wavelength 450 nm is shown in FIG. 6. Figure 6 Figure 7

[0052] As can be seen from FIG. 5 and FIG. 6, the spectrum of the light source of wavelength 450 nm is not within the absorption range of TPBi, but the hot electron photodetector of this example can produce more than 10% EQE (under 10V bias) to the light source of wavelength 450 nm (lower than the band gap energy of TPbi), which indicates that the photoelectric response is not produced by the absorption of TPBi itself. Figure 6 Figure 7 In addition, the same test found that:

[0053]

[0054] ​​​​​​​​Adjusting the composition of the organic semiconductor layer to 3TPYMB, Bphen, B3PyMPM, PO-T2T, TSPO1 or B4PyMPM, or to a combination of at least two of TmPyPB, TPBi, 3TPYMB, Bphen, B3PyMPM, PO-T2T, TSPO1 and B4PyMPM, the obtained thermoelectronic photodetector can also achieve wide spectral band response.

[0055] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A thermionic photodetector, characterized in that, The composition includes a light-transmitting substrate, a light-transmitting anode layer, an organic semiconductor layer, an electron injection layer, and a cathode layer stacked sequentially; the organic semiconductor layer comprises at least one of the following organic semiconductor materials: ； The composition of the electron injection layer includes at least one of LiF, CsF, and Li2O; The cathode layer comprises at least one of Al, Ba, Ca, and Cs.

2. The thermionic photodetector according to claim 1, characterized in that: The light-transmitting substrate is one of a glass substrate, a quartz substrate, a sapphire substrate, or a light-transmitting polymer substrate.

3. The thermionic photodetector according to claim 1, characterized in that: The light-transmitting anode layer is one of indium tin oxide film, fluorine-doped tin dioxide film, and indium gallium zinc oxide film.

4. The thermionic photodetector according to claim 1, characterized in that: The thickness of the organic semiconductor layer is 50 nm to 200 nm.

5. The thermionic photodetector according to claim 1, characterized in that: The thickness of the electron injection layer is 0.5 nm to 1 nm.

6. A method for fabricating a thermionic photodetector as described in any one of claims 1 to 5, characterized in that, Includes the following steps: 1) Anode material is coated on one side of a light-transmitting substrate to form a light-transmitting anode layer; 2) An organic semiconductor layer, an electron injection layer, and a cathode layer are sequentially deposited on the surface of the transparent anode layer using a thermal evaporation method to obtain a thermionic photodetector.

7. A detection device, characterized in that, It includes the thermionic photodetector as described in any one of claims 1 to 5.

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