Self-driven transparent ultraviolet flexible photoelectric detector and image sensing array

Abstract

The invention relates to the technical field of photoelectric detection and image sensing, and discloses a self-driven transparent ultraviolet flexible photoelectric detector and an image sensing array. The detector provided by the invention has excellent mechanical stability and high transparency, and supports 360-degree omnibearing optical signal detection. Wherein water molecules in the PEDOT / Alg (Fe < 3 + >) hydrogel between graphene and titanium dioxide are polarized by utilizing Fermi energy level difference between graphene and titanium dioxide. Under the irradiation of a light source, the photon-generated carrier further induces part of water molecules to be polarized, so that transient light polarization current is generated, and high-sensitivity detection of light signals is realized. On the basis of the photoelectric detector, an image sensing array formed by the photoelectric detector is further constructed, image capture can be achieved in a bent state, and imaging processing can be conducted on multi-angle incident optical signals. Accurate recognition and classification can be performed on the acquired images in combination with a convolutional neural network (CNN), and the wide application prospect of the device in the fields of artificial intelligence and machine vision is fully shown.

Description

Technical Field

[0001] The present application belongs to the field of photoelectric detectors and image sensing technologies, and relates to a self-driven transparent ultraviolet flexible photoelectric detector and image sensing array based on polar molecular polarization theory. Background Art

[0002] Photodetectors are important components in the fields of image sensing, optical communications, spectral analysis, and optoelectronics. Traditional photodetectors are mainly made of semiconductor materials such as silicon, gallium nitride, or gallium arsenide. Although they have advantages in response speed, they have obvious limitations in flexibility, stretchability, and adaptability to complex surface shapes, making it difficult to meet the application requirements of flexible wearable devices and complex environments.

[0003] Flexible ultraviolet photodetectors have shown broad application prospects in the fields of wearable medical monitoring, bendable imaging sensors and portable optical communications due to their low cost, good foldability, light weight and wear resistance. However, the transparency and imaging performance of most flexible photodetectors currently do not fully meet the actual needs of omnidirectional optical signal detection and curved imaging.

[0004] Titanium dioxide (TiO2), as a broadband semiconductor material, is widely used in UV photodetectors due to its cost-effectiveness, simple synthesis process and excellent thermal stability. As an n-type semiconductor, its bandgap is about 3eV. Graphene (Gr), as a new type of two-dimensional semiconductor, is also widely used in optoelectronic devices due to its strong electron interaction and no bandgap characteristics, with carrier multiplication and superconductivity.

[0005] Hydrogel is a polymer material with a three-dimensional network structure and water as a dispersion medium. In this structure, free water molecules show significant fluidity. Hydrogel has been widely used in flexible devices due to its good transparency, non-toxicity, easy preparation and excellent mechanical flexibility. And its abundant water molecules can be polarized between p-type and n-type semiconductors, which is conducive to the development of flexible photodetectors (FPDs) with excellent performance.

[0006] Based on this, the present invention designs a flexible photodetector, which breaks through the limitations of traditional detectors by introducing a heterostructure of graphene and titanium dioxide and conductive hydrogel. Compared with existing devices, the detector not only has excellent flexibility and bending performance, can adapt to various complex curvatures and irregular surfaces, but also has good transparency, and can achieve 360° all-round optical signal detection and curved imaging capabilities. These characteristics enable the device to show significant technical advantages in the fields of image sensing and optical communications, providing a new solution for the development of flexible wearable devices and curved imaging systems, and demonstrating its great potential in future applications. Summary of the invention

[0007] The present invention aims to solve the problems in the prior art and proposes a flexible transparent photodetector based on polarity theory. The flexible photodetector has bendability and can detect 360° all-round light signals, significantly improving the flexibility and reliability of the image sensing system.

[0008] The first object of the present invention is to provide a self-driven transparent ultraviolet flexible photodetector, the photodetector comprising: graphene, titanium dioxide film and PEDOT / Alg (Fe 3+ ) hydrogel, and a first electrode and a second electrode are respectively provided on the graphene and the titanium dioxide.

[0009] The preparation method thereof comprises the following steps: Transferring graphene to a first flexible substrate, and depositing a titanium dioxide film on a second flexible substrate; preparing a first electrode on the graphene, and preparing a second electrode on the titanium dioxide film; Preparation of PEDOT / Alg(Fe 3+ ) hydrogel; Combine PEDOT / Alg(Fe 3+ ) hydrogel is placed in the non-electrode area of ​​the titanium dioxide film; the first flexible substrate is turned over so that the graphene side covers the PEDOT / Alg(Fe 3+ ) hydrogel to obtain the self-driven transparent ultraviolet flexible photodetector.

[0010] The first flexible substrate and the second flexible substrate are polyethylene terephthalate (PET).

[0011] The first electrode and the second electrode are independently selected from one or more of gold, titanium, chromium, nickel and silver, and the thickness of the electrode is 100-300nm.

[0012] The graphene is a single layer or a multilayer, and is combined with PET to improve the flexibility and mechanical stability of the detector.

[0013] The PEDOT / Alg(Fe 3+)Hydrogel is a polymer containing a large number of water molecules, which not only provides mechanical flexibility, but also enhances charge transfer performance and optimizes photoelectric response effects. It is prepared by dissolving sodium alginate (Alg) in deionized water, stirring to form a viscous liquid, adding PEDOT:PSS aqueous solution, and continuing to stir to form a PEDOT / Alg solution. Ferric chloride (FeCl3) is dissolved in deionized water, mixed with a solution of GDL dissolved in deionized water, and then added to the PEDOT / Alg solution. The solution is allowed to stand to complete ionic crosslinking to form a hydrogel. Finally, the hydrogel is immersed in a FeCl3 solution for further crosslinking to enhance conductivity and mechanical stability. After rinsing with water, PEDOT / Alg (Fe 3+ ) hydrogel.

[0014] The first electrode and the second electrode are made of one or more materials selected from gold, titanium, chromium, nickel or silver, and have a thickness of 100-300 nm to ensure the conductivity and stability of the detector.

[0015] The second purpose of the present invention is to provide an image sensing array based on the above-mentioned photodetector, which is based on the above-mentioned self-driven transparent ultraviolet flexible photodetector as a unit, arranged in an array, and a mask plate and a light source with a pattern to be identified are sequentially arranged above the array. The current of each unit in the array is detected by a detection device to obtain a two-dimensional current distribution diagram, and the pattern of the mask plate can be captured after processing. The image sensing array can improve the ability to capture image signals and is particularly suitable for bendable and wearable application scenarios. Due to its good transparency, the system can achieve sensitive capture of 360° light signals through flexible photodetectors, and generate and process images through efficient signal processing.

[0016] The light source is an ultraviolet enhanced xenon lamp with a wavelength of 360nm.

[0017] The detection device is a current measuring instrument.

[0018] The processing is to use a trained convolutional neural network to identify the mask pattern corresponding to the two-dimensional current distribution map.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The present invention proposes a self-driven transparent ultraviolet flexible photodetector based on polarity theory, which has a simple structure and comprises graphene, PEDOT / Alg(Fe 3+ ) hydrogel, titanium dioxide, a first electrode and a second electrode. Due to its good transparency, the detector can detect light signals in all directions at 360 degrees and provide excellent light response performance without an external bias.

[0021] (2) The image sensing array of the present invention utilizes the high-efficiency light signal capture capability of flexible photodetectors. Due to its good transparency, it can realize imaging of light at any angle. Thanks to its excellent mechanical flexibility, the array can still perform light imaging normally in a bent state. In addition, the images generated based on the image sensing array have broad application potential in the fields of image recognition, artificial intelligence, and machine vision. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the structure of the photoelectric detector in Example 1; Figure 2 Schematic diagram of the energy band of the photodetector in the initial state in Example 1; Figure 3 Schematic diagram of the energy band of the photodetector in Example 1 under illumination; Figure 4 is the rise and fall time of the photodetector described in Example 1; Figure 5 The time-current diagram of the photodetector in Example 1 under different bending states; Figure 6 Schematic diagram of the UV image sensor array experimental device in Example 2; Figure 7 This is the two-dimensional current mapping diagram corresponding to the image sensing array under 360nm laser in Example 2; Figure 8 The device diagram and two-dimensional current mapping diagram of the image sensor array in Example 2 in a 30-degree bending state; Fig. 9 Schematic diagram of light incident from any angle and a two-dimensional photocurrent mapping diagram in Example 2; Fig.10 This is a graph showing the result of using a convolutional neural network (CNN) to recognize an image generated by an image sensor array in Example 2. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Embodiment 1: A flexible photodetector comprising graphene (1), a titanium dioxide film (3) on PET, and PEDOT / Alg(Fe 3 +) hydrogel (2), a first electrode (6) and a second electrode (7). The first electrode (6) and the second electrode (7) are respectively arranged on the surface of the graphene (1) and the titanium dioxide (3). The preparation method thereof is as follows: 1) Take a piece of polyethylene terephthalate (PET) flexible substrate of appropriate size, immerse it in acetone and ethanol solutions for cleaning in turn to remove surface impurities, and blow dry it with nitrogen (N2). 2) On the front side of the PET flexible substrate, a titanium dioxide film with a thickness of 270 nm was deposited using magnetron sputtering technology to ensure surface uniformity. 3) Select one side of the PET flexible substrate as the front side and transfer the single-layer graphene to the surface of the PET substrate; 4) Dissolve 2g of sodium alginate (Alg) in 50mL of deionized water, stir for 40 minutes to form a viscous liquid, add 2mL of PEDOT:PSS aqueous solution, and continue stirring for 30 minutes to form a PEDOT / Alg solution. Dissolve 0.58g of ferric chloride (FeCl3) in 30mL of deionized water, mix with a solution of 1.29g of GDL dissolved in 20mL of deionized water, add to the PEDOT / Alg solution, and let stand for 12 hours to complete ionic crosslinking to form a hydrogel. Finally, soak the hydrogel in 0.2M FeCl3 solution for further crosslinking to enhance conductivity and mechanical stability, and rinse with water to obtain PEDOT / Alg (FeCl3). 3+ ) hydrogel. 5) A 100 nm thick silver electrode (first electrode) was fabricated on the graphene surface, and a 100 nm thick gold electrode (second electrode) was fabricated on the titanium dioxide surface. 6) Combine PEDOT / Alg(Fe 3+ ) hydrogel sandwiched between titanium dioxide and graphene to form graphene-PEDOT / Alg(Fe 3+ ) Hydrogel-TiO2 heterostructures, e.g. Figure 1 shown. 7) Connect the silver electrode on the graphene to the positive pole of the ammeter, and connect the gold electrode on the titanium dioxide to the negative pole of the ammeter. 8) Graphene-PEDOT / Alg(Fe 3+ ) The band structure of the hydrogel-titanium dioxide photodetector is as follows Figure 2 The changes of carriers after illumination are shown in Figure 3 When the light source illuminates the semiconductor surface, the semiconductor absorbs photons, causing the Fermi level difference between graphene and titanium dioxide to change, and the water molecules in the hydrogel are instantly polarized, generating a polarized current; after the light source is turned off, the photocarriers recombine, the water molecules are depolarized, and a negatively polarized current is generated. 9) Test the rise time and fall time of the photodetector, such as Figure 4 As shown, the measured rise time is 24.5ms and the fall time is 45.1ms. 10) Perform 500 bending tests on the photodetector at a bending angle of 90°. Figure 5 As shown, the value of the photocurrent remains unchanged and the device performance remains stable.

[0025] Embodiment 2: An image sensing device, the system combines convolutional neural network to perform image recognition. The system includes an ultraviolet enhanced xenon lamp (4), an image sensing array (8), a mask plate (9) having a pattern to be recognized, a detection device (5) and a signal processing module (10). The image sensing array (8) is composed of 8×8 flexible detection units, the wavelength of the ultraviolet enhanced xenon lamp is 360nm, and the mask plate (9) is a self-made copper-based mask plate with a hollow "Z", "J", "U", "C" or "O" shape in the middle. The detection device (5) is an instrument suitable for current measurement such as Keithley 6514 electrometer, which is used to accurately measure the electrical signal of each unit in the image sensing array (8). The signal processing module (10) is used to process the collected electrical signal to generate a two-dimensional current distribution map. The preparation specifically includes: 1) Using photolithography technology, transfer the 8×8 array pattern (unit size 500μm×500μm) to a PET substrate, deposit and etch titanium dioxide to form an array. Then design the electrode pattern, reserve the electrode contact area under the array, and deposit a gold film in the contact area to form an electrode by photolithography and magnetron sputtering technology. 2) The 8×8 array pattern (unit size 500μm×500μm) was transferred to the PET substrate by photolithography, and the graphene on the copper substrate was wet-transferred to the PET surface, and the excess graphene was etched away, leaving only the array unit. After cleaning, the electrode pattern was made, and a gold film was deposited in the contact area by photolithography and magnetron sputtering technology to complete the electrode. 3) Combine PEDOT / Alg(Fe 3+ ) hydrogel was cut into 500 μm × 500 μm size and placed between titanium dioxide and graphene array units to complete the graphene-PEDOT / Alg(Fe 3+ ) Preparation of hydrogel-titanium dioxide arrays. 4) Place a "Z"-shaped mask (9) above the image sensor array (8), and place the light source (4) directly above it. Figure 6 The current of each unit is measured by the detection device (5), and a clear two-dimensional photocurrent comparison diagram is obtained by using the signal processing module (10), as shown in FIG. Figure 7 shown. 5) When the image sensing array (8) is bent by 30°, a clear photocurrent comparison diagram can still be obtained by using the signal processing module (10), such as Figure 8 shown. 6) When the light of the ultraviolet enhanced xenon lamp (4) is incident on the image sensor array (8) from different angles, a clear two-dimensional current distribution diagram is obtained through the signal processing module (10), such as Fig. 9 shown. 7) A large number of two-dimensional current distribution maps obtained for various pattern masks and the corresponding mask patterns are used as data sets for image recognition training of convolutional neural networks. After 85 training iterations, the image recognition accuracy can reach 99%, showing efficient image recognition capabilities, such as Fig.10 shown.

Claims

1. A self-driven transparent ultraviolet flexible photodetector, characterized in that: The photoelectric detector comprises: graphene (1), a titanium dioxide film (3) and a PEDOT / Alg (Fe 3+ ) hydrogel (2), and a first electrode (6) and a second electrode (7) are respectively provided on the graphene and the titanium dioxide.

2. A method for preparing the self-driven transparent ultraviolet flexible photodetector as claimed in claim 1, characterized in that: These include: Transferring graphene to a first flexible substrate, and depositing a titanium dioxide film on a second flexible substrate; preparing a first electrode on the graphene, and preparing a second electrode on the titanium dioxide film; Preparation of PEDOT / Alg(Fe 3+ ) hydrogel; Combine PEDOT / Alg(Fe 3+ ) hydrogel is placed in the non-electrode area of ​​the titanium dioxide film; the first flexible substrate is turned over so that the graphene side covers the PEDOT / Alg(Fe 3+ ) hydrogel to obtain the self-driven transparent ultraviolet flexible photodetector.

3. The method for preparing the self-driven transparent ultraviolet flexible photodetector according to claim 2, characterized in that: The first flexible substrate and the second flexible substrate are polyethylene terephthalate (PET).

4. The self-driven transparent ultraviolet flexible photodetector according to claim 1, characterized in that: The first electrode (6) and the second electrode (7) are independently selected from one or more of gold, titanium, chromium, nickel and silver, and the thickness of the electrodes is 100-300 nm.

5. An image sensor array, characterized in that: The self-driven transparent ultraviolet flexible photodetector described in claim 1 is used as a unit and arranged in an array. A mask (9) having a pattern to be identified and a light source (4) are sequentially arranged above the array. The current of each unit in the array is detected by a detection device (5) to obtain a two-dimensional current distribution diagram, and the pattern of the mask can be captured after processing.

6. The image sensor array according to claim 5, characterized in that: The light source (4) is an ultraviolet-enhanced xenon lamp with a wavelength of 360 nm.

7. The image sensor array according to claim 5, characterized in that: The detection device (5) is a current measuring instrument.

8. The image sensing array according to claim 5, characterized in that: The processing is to use a trained convolutional neural network to identify the mask pattern corresponding to the two-dimensional current distribution map.

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