Self-driven transparent ultraviolet flexible photodetector and image sensing array

Abstract

The present application 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 has excellent mechanical stability and high transparency, and supports 360-degree omnidirectional light signal detection. The water molecules in the PEDOT / Alg(Fe 3+ ) hydrogel between graphene and titanium dioxide are polarized by the Fermi level difference between graphene and titanium dioxide. Under light irradiation, the photo-generated carriers further induce the polarization of part of the water molecules, thereby generating a transient optical polarization current and realizing high-sensitivity detection of the light signal. Based on the photoelectric detector, the present application further constructs an image sensing array composed of the photoelectric detector, which can realize image capture in a bent state and image processing of light signals incident at multiple angles. The collected images can be accurately recognized and classified in combination with a convolutional neural network (CNN), fully demonstrating the broad application prospects of the device in the fields of artificial intelligence and machine vision.

Description

Technical Field

[0001] This application belongs to the field of photodetector and image sensing technology, and relates to a self-driven transparent ultraviolet flexible photodetector and image sensing array based on the polar molecular polarization theory. Background Technology

[0002] Photodetectors are crucial components in fields such as image sensing, optical communication, spectral analysis, and optoelectronics. Traditional photodetectors primarily utilize semiconductor materials such as silicon, gallium nitride, or gallium arsenide. While they exhibit advantages in response speed, they suffer from significant 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, due to their low cost, excellent folding ability, lightweight, and wear resistance, have shown broad application prospects in wearable medical monitoring, bendable imaging sensors, and portable optical communications. However, the transparency and imaging performance of most flexible photodetectors currently do not fully meet the practical requirements for omnidirectional optical signal detection and bending imaging.

[0004] Titanium dioxide (TiO2), as a broadband semiconductor material, is widely used in ultraviolet photodetectors due to its cost-effectiveness, simple synthesis process, and excellent thermal stability. As an n-type semiconductor, its bandgap is approximately 3 eV. Graphene (Gr), as a novel two-dimensional semiconductor, is also widely used in optoelectronic devices due to its strong electron interactions and bandgap-free characteristics, exhibiting carrier multiplication and superconductivity.

[0005] Hydrogels are polymer materials with a three-dimensional network structure, using water as the dispersion medium. In this structure, free water molecules exhibit significant fluidity. Due to their excellent transparency, non-toxicity, ease of preparation, and outstanding mechanical flexibility, hydrogels have been widely used in flexible devices. Furthermore, their abundant water molecules can polarize between p-type and n-type semiconductors, which is beneficial for developing high-performance flexible photodetectors (FPDs).

[0006] Based on this, this invention designs a flexible photodetector that overcomes the limitations of traditional detectors by introducing a heterostructure of graphene and titanium dioxide and a conductive hydrogel. Compared to existing devices, this detector not only possesses superior flexibility and bending performance, adapting to various complex curvatures and irregular surfaces, but also exhibits good transparency, enabling 360° omnidirectional optical signal detection and bending imaging capabilities. These characteristics give the device significant technical advantages in image sensing and optical communication, providing a novel solution for the development of flexible wearable devices and bending imaging systems, demonstrating its enormous potential for future applications. Summary of the Invention

[0007] This invention aims to solve the problems in the prior art. Based on polarity theory, it proposes a flexible transparent photodetector that is flexible and can detect light signals in all directions at 360°, which significantly improves the flexibility and reliability of image sensing systems.

[0008] The first objective of this invention is to provide a self-driven transparent ultraviolet flexible photodetector, comprising: graphene, a titanium dioxide thin film, and a PEDOT / Alg(Fe) film disposed between the two. 3+ The hydrogel has a first electrode and a second electrode respectively on graphene and titanium dioxide.

[0009] Its preparation methods include the following:

[0010] Graphene is transferred onto a first flexible substrate, and a titanium dioxide thin film is deposited on a second flexible substrate; a first electrode is fabricated on the graphene, and a second electrode is fabricated on the titanium dioxide thin film;

[0011] Preparation of PEDOT / Alg(Fe 3+ Hydrogel;

[0012] Combine PEDOT / Alg(Fe 3+ The hydrogel is placed in the non-electrode region of the titanium dioxide film; the first flexible substrate is flipped so that the graphene side covers the PEDOT / Alg(Fe) film. 3+ The self-driven transparent ultraviolet flexible photodetector was obtained on the hydrogel.

[0013] The first flexible substrate and the second flexible substrate are polyethylene terephthalate (PET).

[0014] 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 electrodes is 100-300 nm.

[0015] The graphene is single-layered or multi-layered, and when combined with PET, the flexibility and mechanical stability of the detector are improved.

[0016] The PEDOT / Alg(Fe 3+Hydrogels are polymers containing a large number of water molecules, providing both mechanical flexibility and enhanced charge transport properties, thus optimizing photoelectric response. Their preparation involves dissolving sodium alginate (Alg) in deionized water, stirring to form a viscous liquid, then adding a PEDOT:PSS aqueous solution and continuing stirring 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 added to the PEDOT / Alg solution. The mixture is allowed to stand to complete ionic crosslinking, forming a hydrogel. Finally, the hydrogel is immersed in a FeCl3 solution for further crosslinking to enhance conductivity and mechanical stability. After rinsing with water, the PEDOT / Alg (FeCl3 / GDL) hydrogel is obtained. 3+ Hydrogel.

[0017] The first and second electrodes are made of one or more materials selected from gold, titanium, chromium, nickel or silver, with a thickness of 100-300 nm to ensure the conductivity and stability of the detector.

[0018] The second objective of this invention is to provide an image sensing array based on the aforementioned photodetector. This array uses the self-driven transparent ultraviolet flexible photodetector as a unit, arranged in an array. A mask with a pattern to be identified and a light source are sequentially placed above the array. A detection device detects the current in each unit of the array to obtain a two-dimensional current distribution map. After processing, the pattern on the mask can be captured. This image sensing array enhances the image signal capture capability and is particularly suitable for flexible and wearable applications. Due to its excellent transparency, the system achieves sensitive capture of light signals from 360° using the flexible photodetector and performs image generation and processing through efficient signal processing.

[0019] The light source is an ultraviolet-enhanced xenon lamp with a wavelength of 360nm.

[0020] The detection device is a current measuring instrument.

[0021] The process involves using a trained convolutional neural network to identify the mask pattern corresponding to the two-dimensional current distribution map.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) This invention proposes a self-driven transparent ultraviolet flexible photodetector based on polarity theory. It has a simple structure and includes graphene, PEDOT / Alg(Fe) 3+ The detector consists of a hydrogel, titanium dioxide, a first electrode, and a second electrode. Due to its excellent transparency, the detector can detect light signals from all 360° omnidirectionally and provides excellent photoresponse performance without an external bias voltage.

[0024] (2) The image sensing array of the present invention utilizes the efficient light signal capture capability of a flexible photodetector. Due to its good transparency, it can achieve imaging of light at any angle. Thanks to its excellent mechanical flexibility, the array can still perform optical imaging normally even when bent. Furthermore, the images generated based on this image sensing array have broad application potential in fields such as image recognition, artificial intelligence, and machine vision. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the photodetector structure in Example 1;

[0026] Figure 2 This is a schematic diagram of the energy band structure of the photodetector in its initial state in Example 1;

[0027] Figure 3 This is a schematic diagram of the energy band structure of the photodetector under illumination in Example 1;

[0028] Figure 4 The rise and fall times of the photodetector described in Example 1;

[0029] Figure 5 The time-current graphs of the photodetector described in Example 1 under different bending states are shown.

[0030] Figure 6 This is a schematic diagram of the ultraviolet image sensing array experimental device in Example 2;

[0031] Figure 7 This is a two-dimensional current mapping diagram of the image sensing array under 360nm laser light in Example 2;

[0032] Figure 8 This is a diagram of the image sensing array in Example 2 under a 30-degree bend and a two-dimensional current mapping diagram.

[0033] Figure 9 This is a schematic diagram of light incident from any angle in Example 2 and a two-dimensional photocurrent mapping diagram;

[0034] Figure 10 This is a diagram showing the result of recognizing an image generated by an image sensing array using a convolutional neural network (CNN) in Example 2. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] Example 1:

[0037] A flexible photodetector includes graphene (1), a titanium dioxide film on PET (3), and PEDOT / Alg(Fe) 3 + The study comprises a hydrogel (2), a first electrode (6), and a second electrode (7). The first electrode (6) and the second electrode (7) are respectively disposed on the surfaces of graphene (1) and titanium dioxide (3). The preparation method is as follows:

[0038] 1) Take a piece of polyethylene terephthalate (PET) flexible substrate of appropriate size, immerse it in acetone and ethanol solutions in turn to clean it to remove surface impurities, and then dry it with nitrogen (N2).

[0039] 2) On the front side of the PET flexible substrate, a titanium dioxide film with a thickness of 270nm is deposited using magnetron sputtering technology to ensure surface uniformity.

[0040] 3) Select one side of the PET flexible substrate as the front side and transfer the monolayer graphene to the surface of the PET substrate;

[0041] 4) Dissolve 2g of sodium alginate (Alg) in 50mL of deionized water and stir for 40 minutes to form a viscous liquid. Then 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 and mix it with a solution of 1.29g of GDL dissolved in 20mL of deionized water. Add this mixture to the PEDOT / Alg solution and let it stand for 12 hours to complete ionic cross-linking and form a hydrogel. Finally, immerse the hydrogel in 0.2M FeCl3 solution for further cross-linking to enhance conductivity and mechanical stability. After rinsing with water, obtain PEDOT / Alg (FeCl3) solution. 3+ Hydrogel.

[0042] 5) A 100 nm thick silver electrode (first electrode) is fabricated on the graphene surface, and a 100 nm thick gold electrode (second electrode) is fabricated on the titanium dioxide surface.

[0043] 6) Combine PEDOT / Alg(Fe 3+ The hydrogel is sandwiched between titanium dioxide and graphene, forming graphene-PEDOT / Alg(Fe) 3+ The heterostructure of hydrogel-titanium dioxide, such as Figure 1 As shown.

[0044] 7) Connect the silver electrode on the graphene to the positive terminal of the ammeter, and connect the gold electrode on the titanium dioxide to the negative terminal of the ammeter.

[0045] 8) Graphene-PEDOT / Alg(Fe 3+The band structure of the hydrogel-titanium dioxide photodetector is as follows: Figure 2 As shown. The change in charge carriers after illumination is as follows. Figure 3 As shown, when a light source illuminates the semiconductor surface, the semiconductor absorbs photons, causing a change in the Fermi level difference between graphene and titanium dioxide. Water molecules in the hydrogel are instantaneously polarized, generating a polarization current. After the light source is turned off, photocarriers recombine, water molecules depolarize, and a negative polarization current is generated.

[0046] 9) Test the rise time and fall time of the photodetector, such as... Figure 4 As shown, the rise time was measured to be 24.5 ms and the fall time to be 45.1 ms.

[0047] 10) Perform 500 bending tests on the photodetector at a bending angle of 90°, such as... Figure 5 As shown, the value of the photocurrent remains constant, and the device performance remains stable.

[0048] Example 2:

[0049] An image sensing device is disclosed, which combines a convolutional neural network for image recognition. The system includes an ultraviolet-enhanced xenon lamp (4), an image sensing array (8), a mask (9) with 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 ultraviolet-enhanced xenon lamp has a wavelength of 360nm. The mask (9) is a self-made copper-based mask with a hollowed-out “Z”, “J”, “U”, “C”, or “O” shape. The detection device (5) is an instrument suitable for current measurement, such as a Keithley 6514 electrometer, 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 acquired electrical signals and generate a two-dimensional current distribution map.

[0050] Its preparation specifically includes:

[0051] 1) An 8×8 array pattern (unit size 500μm×500μm) was transferred onto a PET substrate using photolithography, and titanium dioxide was deposited and etched to form the array. Electrode patterns were then designed, with electrode contact areas reserved below the array, and gold films were deposited in the contact areas using photolithography and magnetron sputtering to form electrodes.

[0052] 2) An 8×8 array pattern (unit size 500μm×500μm) was transferred onto a PET substrate using photolithography. Graphene from a copper substrate was then wet-transferred to the PET surface, and excess graphene was etched away, leaving only the array units. After cleaning, electrode patterns were fabricated, and gold films were deposited in the contact areas using photolithography and magnetron sputtering to complete the electrodes.

[0053] 3) Combine PEDOT / Alg(Fe 3+ The hydrogel was cut into 500μm × 500μm pieces and placed between titanium dioxide and graphene array units to complete the graphene-PEDOT / Alg(Fe) array. 3+ Preparation of hydrogel-titanium dioxide array.

[0054] 4) Place a Z-shaped mask (9) above the image sensor array (8) and position the light source (4) directly above it. This structure is as follows: Figure 6 As shown. The current magnitude of each unit is measured by the detection device (5), and a clear two-dimensional photocurrent comparison diagram is obtained using the signal processing module (10), as shown. Figure 7 As shown.

[0055] 5) When the image sensor array (8) is bent at 30°, a clear photocurrent contrast diagram can still be obtained using the signal processing module (10), such as Figure 8 As shown.

[0056] 6) When the light from the ultraviolet-enhanced xenon lamp (4) is incident from different angles on the image sensing array (8), a clear two-dimensional current distribution map is obtained through the signal processing module (10), such as Figure 9 As shown.

[0057] 7) A large number of two-dimensional current distribution maps and corresponding mask patterns obtained from various patterned masks were used as a dataset for training the image recognition function of the convolutional neural network. After 85 training iterations, the image recognition accuracy reached 99%, demonstrating highly efficient image recognition capabilities. Figure 10 As shown.

Claims

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

2. The method for preparing the self-driven transparent ultraviolet flexible photodetector as described in claim 1, characterized in that, Including the following: Graphene is transferred onto a first flexible substrate, and a titanium dioxide thin film is deposited on a second flexible substrate; a first electrode is fabricated on the graphene, and a second electrode is fabricated on the titanium dioxide thin film; Preparation of PEDOT / Alg(Fe 3+ Hydrogel; Combine PEDOT / Alg(Fe 3+ The hydrogel is placed in the non-electrode region of the titanium dioxide film; the first flexible substrate is flipped so that the graphene side covers the PEDOT / Alg(Fe) film. 3+ The self-driven transparent ultraviolet flexible photodetector was obtained on the hydrogel.

3. The method for fabricating a 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 sensing array, characterized in that, Using the self-driven transparent ultraviolet flexible photodetector as described in claim 1 as a unit, arranged in an array, a mask (9) with a pattern to be identified and a light source (4) are sequentially set above the array. The current of each unit in the array is detected by the detection device (5) to obtain a two-dimensional current distribution map. After processing, the pattern of the mask can be captured.

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

7. The image sensing 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 process involves using a trained convolutional neural network to identify the mask pattern corresponding to the two-dimensional current distribution map.

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