P-N Junction Hydrogen Sensor of Laser-Induced Graphene and Its Preparation Method

Abstract

The present application provides a P-N junction hydrogen sensor based on laser-induced graphene and a preparation method thereof. In the present application, a coherent N-type graphene structure and a P-type graphene structure are formed on a flexible substrate by means of laser induction, and metal particles are deposited on the surface of the graphene structure. The present application utilizes the coupling reaction of the metal particles with hydrogen to form a space charge region at the P-N junction formed by the coherent conduction between the N-type graphene structure and the P-type graphene structure, and provides a sensing current signal through the hydrogen-induced resistance change generated by the metal particles / graphene of the P-N junction sensor device and the double enhancement effect of the P-N junction, so as to realize the identification of hydrogen concentration by detecting the current change of the P-N junction hydrogen sensor device. The present application has low preparation cost and high test accuracy, and can simultaneously form large-scale hydrogen sensors by calcination on a large-area flexible substrate through laser induction technology, realizing large-scale mass production.

Description

Technical Field

[0001] The present application relates to the technical field of gas sensors, and in particular to a P-N junction hydrogen sensor based on laser-induced graphene and a preparation method thereof. Background Art

[0002] In hydrogen fuel cell vehicles and hydrogen production workshops, hydrogen leakage can pose a major safety hazard, so hydrogen leakage monitoring is required. According to different detection principles, gas detection devices are mainly divided into different types such as gas-sensitive type, cantilever beam frequency type, capacitive type, photoelectric type, ion migration, and chromatograph. The disadvantages of capacitive and cantilever beam frequency type gas sensors mainly lie in the lack of selectivity, and any gas change will cause changes in the resonance frequency and capacitance; photoelectric type gas sensors are expensive, complex to detect, and not conducive to widespread use; the disadvantages of ion type gas sensors mainly lie in the need for an additional ion source, which will lead to a large device volume; the chromatograph mechanism is also expensive and not conducive to widespread industrial use.

[0003] For conventional gas-sensitive hydrogen sensing technology, its working principle is to convert the hydrogen concentration signal into an electrical signal output, so as to achieve the measurement of hydrogen concentration. Existing gas-sensitive hydrogen sensing technology is usually limited by the response characteristics of electrical components and has the defect of low accuracy, but it is cheap and has good stability. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present application provides a P-N junction hydrogen sensor based on laser-induced graphene and a preparation method thereof. When the P-N junction hydrogen sensor device of the present application encounters hydrogen, hydrogen will cause a double enhancement effect on the metal particles / graphene and P-N junction of the P-N junction sensor device, resulting in a resistance change based on the hydrogen-induced resistance effect. Thus, the hydrogen concentration is identified by detecting the current change of the P-N junction hydrogen sensor device. Through the micro-nano structure of laser-induced graphene and the enhancement effect generated in the material, the present application can enhance the selectivity to hydrogen, and has the advantages of simple processing technology, low cost, high flexibility, light weight, and easy mass production. The present application specifically adopts the following technical solutions.

[0005] First, to achieve the above object, a P-N junction hydrogen sensor based on laser-induced graphene is proposed, which includes: a flexible substrate; an N-type graphene structure formed by laser-induced calcination within a first preset temperature range; a P-type graphene structure formed by laser-induced calcination within a second preset temperature range; metal particles are deposited on the surfaces of the N-type graphene structure and the P-type graphene structure, and at least one pair of connection ends are formed by connecting the N-type graphene structure and the P-type graphene structure to each other. The N-type graphene structure and the P-type graphene structure are arranged side by side and opposite to each other and conduct electricity through the connection ends.

[0006] Optionally, a laser-induced graphene PN junction hydrogen sensor as described above, wherein the flexible substrate is any one of the following: polyimide (PI) film, polyetherimide (PEI) film, polyetheretherketone (PEEK) film, polyphenylene sulfide (PPS) film; and the first preset temperature range is set between 250°C and 450°C, or between 800°C and 1000°C.

[0007] Optionally, in any of the above laser-induced graphene PN junction hydrogen sensors, the second preset temperature range is set to be lower than 250°C, or set to be between 450°C and 800°C.

[0008] Optionally, a laser-induced graphene PN junction hydrogen sensor as described above, wherein the N-type graphene structure includes: a plurality of transverse N-type docking arms and a longitudinal N-type connecting bar running through the end of each transverse N-type docking arm; the P-type graphene structure includes: a plurality of transverse P-type docking arms and a longitudinal P-type connecting bar running through the end of each transverse P-type docking arm, which are symmetrically arranged with the N-type graphene structure; wherein the head end of each transverse N-type docking arm is connected to the head end of each transverse P-type docking arm side by side, the longitudinal N-type connecting bar and the longitudinal P-type connecting bar are respectively arranged on the outside of each transverse N-type docking arm and each transverse P-type docking arm, and the length and width dimensions of each transverse N-type docking arm and each transverse P-type docking arm are the same and the spacing distance is the same.

[0009] Optionally, a laser-induced graphene PN junction hydrogen sensor as described above, wherein the middle portion of the longitudinal N-type connecting strip is electrically connected to a first conductive terminal, the middle portion of the longitudinal P-type connecting strip is electrically connected to a second conductive terminal, and the conductive terminals are respectively connected to conductive wires to form an electrical path to output the current change caused by the resistance change between the N-type graphene structure and the P-type graphene structure due to the hydrogen-induced resistance effect.

[0010] Optionally, in a laser-induced graphene PN junction hydrogen sensor as described above, the metal particles are platinum particles or palladium particles, and the metal particles are deposited on the upper surface of the N-type graphene structure and the P-type graphene structure with a thickness of 1nm-10nm by magnetron sputtering or electron beam evaporation.

[0011] A preparation method of a P-N junction hydrogen sensor based on laser-induced graphene, the steps of which include: on a flexible substrate, coherently forming an N-type graphene structure by laser-induced calcination at a first preset temperature range on one side, and adjusting the laser emission power on the other side to calcine at a second preset temperature range to form a P-type graphene structure; depositing metal particles on the upper surfaces of the N-type graphene structure and the P-type graphene structure by magnetron sputtering or electron beam evaporation; fixing a first wire terminal outside the N-type graphene structure, fixing a second conductive terminal outside the P-type graphene structure, and connecting wires to the two wire terminals respectively to form an electrical path to output the current change generated by the resistance change due to the hydrogen-induced resistance effect between the N-type graphene structure and the P-type graphene structure.

[0012] Optionally, in the preparation method of the P-N junction hydrogen sensor based on laser-induced graphene as described in any one of the above, the flexible substrate is a polyimide (PI) film, a polyetherimide (PEI) film, a polyetheretherketone (PEEK) film or a polyphenylene sulfide (PPS) film with a thickness between 10 μm and 10 mm, and porous graphene is generated by laser induction of a carbon dioxide light source with a power of 10 W to 100 W.

[0013] Optionally, in the preparation method of the P-N junction hydrogen sensor based on laser-induced graphene as described in any one of the above, the laser-induced calcination temperature of the N-type graphene structure is controlled between 250 °C and 450 °C, or between 800 °C and 1000 °C; the laser-induced calcination temperature of the P-type graphene structure is controlled to be lower than 250 °C, or between 450 °C and 800 °C.

[0014] Optionally, in the preparation method of the P-N junction hydrogen sensor based on laser-induced graphene as described in any one of the above, the metal particles are platinum particles or palladium particles, and the deposition thickness is between 2 nm and 8 nm.

[0015] Beneficial effects

[0016] In this application, a coherent N-type graphene structure and a P-type graphene structure are formed on a flexible substrate by laser induction, and metal particles are deposited on the surface of the graphene structure. This application uses the coupling reaction of metal particles and hydrogen to form a space charge region at the P-N junction formed by the coherent conduction between the N-type graphene structure and the P-type graphene structure. The hydrogen-induced resistance change generated by the metal particles / graphene of the P-N junction sensor device and the double enhancement effect of the P-N junction in the space charge region provides a sensing current signal, so as to realize the identification of hydrogen concentration by detecting the current change of the P-N junction hydrogen sensor device. The preparation process of this application is simple, with low cost and high test accuracy. Large-scale hydrogen sensors can be formed by calcination on a large-area flexible substrate through laser induction technology, realizing large-scale batch production. The sensor structure of this application is lightweight, has high selectivity for hydrogen, and can be arranged at any position according to the detection requirements through the flexible substrate, is flexible and wearable, and has a wide range of application scenarios.

[0017] The porous structure N-type graphene induced by laser and the porous structure P-type graphene induced by laser in the present invention are mainly realized by regulating the temperature of the laser, and can be directly prepared on the surface of a polyimide film (PI) by laser induction, having good compatibility with the original material. Compared with conventional hydrogen sensors, it has flexible and bendable properties, a faster response speed, can meet the flexible development trend of wearable mobile intelligent devices, and is convenient for applications facing the Internet of Things.

[0018] To achieve the selective identification of hydrogen with low concentration and doped with other environmental gases, the P-N junction structure proposed in the present invention can achieve the selectivity for hydrogen through the reaction of platinum or palladium metal particles and hydrogen, and can realize the coupling enhancement recognition effect for hydrogen. The P-N junction structure itself can realize the double enhancement effect of the metal particle / graphene coupling mechanism and the P-N junction through the internal electric field in the space charge region, enhancing the recognition effect of the sensor for hydrogen. Through the resistance change caused by the hydrogen-induced resistance effect in this application, the hydrogen concentration can be directly identified by detecting the current change in the wire connected to both ends of the graphene.

[0019] The metal particles deposited on the surface of the porous structure graphene in this application can control the thickness of the particles by controlling the time of magnetron sputtering or the method of electron beam evaporation. Magnetron sputtering can achieve full coverage on the micro-nano structure surface of the porous structure, and can further enhance the identification of low-concentration hydrogen.

[0020] Other features and advantages of this application will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing this application. Brief Description of the Drawings

[0021] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation to the present application. In the accompanying drawings:

[0022] Figure 1 is a schematic plan view of a P-N junction hydrogen sensor of laser-induced graphene of the present application;

[0023] Figure 2 is Figure 1 a side view of the sensor structure;

[0024] Figure 3 is a schematic diagram of realizing the conversion between P-type and N-type of CVD graphene by temperature regulation in the present application;

[0025] Figure 4 is a schematic diagram of the mechanism for enhancing the hydrogen-sensing characteristics of the planar structure P-N junction realized by the LIG method in the present application.

[0026] In the figure, 1 represents a polyimide film; 2 represents a first wire terminal; 3 represents an N-type graphene structure; 4 represents metal particles; 5 represents a P-type graphene structure; 6 represents a second conductive terminal; 7 represents a wire. Detailed Embodiments

[0027] To make the objectives and technical solutions of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0028] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as such here.

[0029] The meaning of "and / or" as used in the present application refers to the situation where each exists alone or both exist simultaneously.

[0030] The meaning of "connection" as used in the present application can be a direct connection between components or an indirect connection between components through other components.

[0031] As used in this application, the meanings of "upper" and "lower" refer to the direction from the polyimide film to the wire terminal when the user is facing the P-N junction hydrogen sensor of the laser-induced graphene. The direction from the polyimide film to the wire terminal is the upper direction, and vice versa. This is not a specific limitation on the device mechanism of this application.

[0032] Figure 1 A P-N junction hydrogen sensor of laser-induced graphene according to this application is prepared by laser-induced generation of a porous structure graphite on the surface of a flexible substrate such as a polyimide (PI) film, a polyetherimide (PEI) film, a polyetheretherketone (PEEK) film, or a polyphenylene sulfide (PPS) film using a carbon dioxide laser source.

[0033] In this application, the porous structure graphite on the flexible substrate includes two interconnected parts formed by continuous laser-induced calcination:

[0034] An N-type graphene structure 3, which is formed by laser-induced calcination within a first preset temperature range;

[0035] A P-type graphene structure 5, which is formed by laser-induced calcination within a second preset temperature range;

[0036] Metal particles 4 are deposited on the surfaces of the N-type graphene structure 3 and the P-type graphene structure 5. Moreover, the N-type graphene structure 3 and the P-type graphene structure 5 are interconnected to form at least one pair of docking ends, and within the docking ends, the N-type graphene structure 3 and the P-type graphene structure 5 form Figure 4 the indicated P-N junction, and the docking ends are arranged side by side and conduct with each other to form an intermediate charge region.

[0037] After molding, a first wire terminal 2 is fixed outside the N-type graphene structure 3, a second conductive terminal 6 is fixed outside the P-type graphene structure 5, and wires 7 are respectively connected to the two wire terminals to form an electrical path to output the current change generated by the resistance change due to the hydrogen-induced resistance effect between the N-type graphene structure 3 and the P-type graphene structure 5, thereby realizing the sensing detection signal output for low-concentration hydrogen.

[0038] Reference Figure 2 、 Figure 3As shown, in the present application, the laser can be set to scan back and forth on the surface of the flexible substrate film according to a preset pattern, and different calcination temperatures can be achieved by correspondingly controlling the power of the laser light source during the scanning process, so as to continuously form an N-type graphene structure 3 and a P-type graphene structure 5 on the flexible substrate. During the process of inducing graphene by the laser scanning back and forth coherently on both left and right sides of the flexible substrate, by correspondingly reducing the laser power on one side and increasing the laser power on the other side, porous graphene structures with different polarities can be formed on the flexible substrate with a thickness between 10 μm and 10 mm, and a space charge region providing the action of the internal electric field is formed at the junction position with a coherently conducting P-N junction. In the above process, a laser with a carbon dioxide light source with a power of 10 W - 100 W can generally be used to induce the corresponding porous graphene structure.

[0039] To increase the number of P-N junctions in the sensor, the calcination temperature can be controlled between 250 °C and 450 °C, or the laser between 800 °C and 1000 °C, to induce the formation of several transverse N-type docking arms and a longitudinal N-type connecting strip penetrating the ends of each transverse N-type docking arm on one side of the flexible substrate film; and by controlling the calcination temperature to be lower than 250 °C, or the laser between 450 °C and 800 °C, several transverse P-type docking arms symmetrically penetrating and arranged with the N-type graphene structure 3 and a longitudinal P-type connecting strip penetrating the ends of each transverse P-type docking arm are induced to be formed on the other side of the flexible substrate film. The first ends of each transverse N-type docking arm can be respectively connected in parallel and communicated with the first ends of the corresponding transverse P-type docking arms through continuous laser scanning. The longitudinal N-type connecting strip and the longitudinal P-type connecting strip are respectively arranged on the outer sides of each transverse N-type docking arm and each transverse P-type docking arm, and the length and width dimensions of each transverse N-type docking arm and each transverse P-type docking arm are the same and the spacing distance is the same.

[0040] After the graphene structure is generated, platinum particles or palladium particles with a thickness of 1 nm - 10 nm can be deposited on the upper surfaces of the N-type graphene structure 3 and the P-type graphene structure 5 by magnetron sputtering or electron beam evaporation. Then, a first wire terminal 2 is electrically connected to the middle of the longitudinal N-type connecting strip, a second conductive terminal ⑥ is electrically connected to the middle of the longitudinal P-type connecting strip, and wires ⑦ are respectively connected to each wire terminal to form an electrical path. After connecting it in series to the detection circuit, the current change generated by the resistance change due to the hydrogen-induced resistance effect between the N-type graphene structure 3 and the P-type graphene structure 5 can be output through the wire current, providing the detection of different concentrations of hydrogen. The thickness of the metal particles on the surface layer of the porous graphene structure is mainly controlled by controlling the sputtering or evaporation time. The ideal metal thickness is 1 nm - 10 nm, and preferably, the deposition thickness of platinum particles or palladium particles can be set between 2 nm and 8 nm by sputtering or evaporation for 5 - 20 seconds. The CVD sputtering method can achieve all-round coverage at multiple angles, and the evaporation method can achieve vertical coverage at an angle.

[0041] In the embodiment of the present application, the laser-induced porous structure graphene can quickly realize the P-type and N-type energy band graphene by temperature, so the preparation cost is low and it can be quickly prepared on a large scale. During the preparation process, the structure of the laser-induced porous structure graphene P-type and the laser-induced porous structure graphene N-type can be Figure 1 The relatively arranged E-type structure can also be set as a surface structure with any number of N-type and P-type surfaces in contact with each other. The surface length and width can be arbitrarily adjusted. As long as the P-type and N-type graphene can be close to each other and can be conductive, the sensing structure of the present application can be realized.

[0042] The main working principle of the hydrogen sensor of this application is:

[0043] When a PN junction hydrogen sensor device encounters hydrogen, the hydrogen reacts with the platinum particles or palladium particles as follows:

[0044]

[0045] Desorption: O2+2Pd / H+2[H]→2Pd+2H2O (2)

[0046] The metal particles / graphene and PN junction double enhancement effect of the PN junction sensor device, based on the resistance change of the hydrogen-induced resistance effect, can identify the hydrogen concentration by detecting the current change of the PN junction hydrogen sensor device.

[0047] In this application, polyimide (PI) film is preferred because it can produce porous graphene and also serve as a flexible substrate for hydrogen sensor devices. Laser-induced porous graphene (P-type) and laser-induced porous graphene (N-type) are primarily formed by high-temperature laser calcination. P-type and N-type are controlled by varying the laser intensity to achieve different calcination temperatures. Laser-induced P-type and N-type graphene enable rapid, large-scale production, as different graphene structures can be achieved simply by controlling the calcination temperature.

[0048] Platinum metal is used to enhance the sensor's hydrogen selectivity through its reaction with hydrogen. Furthermore, the metal particles and graphene enhance the hydrogen response, further enhancing the control of the sensor's current and resistance. The metal particles can be deposited via magnetron sputtering or electron beam evaporation. By controlling the magnetron sputtering and evaporation times, the thickness of the metal particles is optimally controlled to between 2 and 8 nanometers.

[0049] The wire terminal can provide a signal output interface for the sensor of the present application. The wire can be used for signal transmission.

[0050] In summary, in the present application, the P-type and N-type graphene structures are arranged side by side through laser spot calcination, so that the circuit conduction of the wire terminal can be achieved. The present invention is mainly a P-N junction hydrogen sensor based on the laser-induced graphene method related to flexible wearables and a preparation method thereof, with low preparation cost, capable of being rapidly and massively prepared, and capable of realizing the recognition of low-concentration hydrogen.

[0051] The above are only the implementation manners of the present application, and the description thereof is relatively specific and detailed, but it should not be understood as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application.

Claims

1. A P-N junction hydrogen sensor based on laser-induced graphene, characterized in that, Comprising: A flexible substrate; An N-type graphene structure (3), which is formed by laser-induced calcination within a first preset temperature range; A P-type graphene structure (5), which is formed by laser-induced calcination within a second preset temperature range; Metal particles (4) are deposited on the surfaces of the N-type graphene structure (3) and the P-type graphene structure (5). Moreover, at least one pair of docking ends are formed by connecting the N-type graphene structure (3) and the P-type graphene structure (5) to each other. The N-type graphene structure (3) and the P-type graphene structure (5) are arranged side by side and opposite to each other by the docking ends and are electrically connected to each other; Wherein, the flexible substrate is any one of the following: polyimide (PI) film, polyetherimide (PEI) film, polyetheretherketone (PEEK) film, polyphenylene sulfide (PPS) film; The first preset temperature range is set between 250°C and 450°C, or is set between 800°C and 1000°C; The second preset temperature range is set to be lower than 250°C, or is set between 450°C and 800°C.

2. The P-N junction hydrogen sensor of laser-induced graphene according to claim 1, wherein The N-type graphene structure (3) includes: a plurality of transverse N-type docking arms and a longitudinal N-type connecting bar passing through the ends of each transverse N-type docking arm; The P-type graphene structure (5) includes, symmetrically arranged with the N-type graphene structure (3): a plurality of transverse P-type docking arms and a longitudinal P-type connecting bar passing through the ends of each transverse P-type docking arm; Wherein, the first ends of each transverse N-type docking arm are respectively connected and communicated with the first ends of each transverse P-type docking arm side by side. The longitudinal N-type connecting bar and the longitudinal P-type connecting bar are respectively arranged outside each transverse N-type docking arm and each transverse P-type docking arm. The length and width dimensions of each transverse N-type docking arm and each transverse P-type docking arm are the same and the spacing distance is the same.

3. The P-N junction hydrogen sensor of the laser-induced graphene according to claim 2, characterized in that, A first wire terminal (2) is electrically connected to the middle of the longitudinal N-type connecting bar, and a second conductive terminal (6) is electrically connected to the middle of the longitudinal P-type connecting bar. Wires (7) are respectively connected to the wire terminals to form an electrical path to output the current change generated by the resistance change due to the hydrogen-induced resistance effect between the N-type graphene structure (3) and the P-type graphene structure (5).

4. The P-N junction hydrogen sensor made of laser-induced graphene according to claim 3, characterized in that, The metal particles (4) are platinum particles or palladium particles. The metal particles are deposited on the upper surfaces of the N-type graphene structure (3) and the P-type graphene structure (5) with a thickness of 1 nm - 1 nm by magnetron sputtering or electron beam evaporation.

5. A preparation method of a P-N junction hydrogen sensor based on laser-induced graphene, characterized in that, Steps for preparing the P-N junction hydrogen sensor of laser-induced graphene according to claim 1, including: On the flexible substrate, an N-type graphene structure (3) is formed by laser-induced calcination on one side within a first preset temperature range in a continuous manner, and the laser emission power is adjusted on the other side to calcine to form a P-type graphene structure (5) within a second preset temperature range; Metal particles (4) are deposited on the upper surfaces of the N-type graphene structure (3) and the P-type graphene structure (5) by magnetron sputtering or electron beam evaporation; Fix the first wire terminal (2) outside the N-type graphene structure (3), fix the second conductive terminal (6) outside the P-type graphene structure (5), and connect wires (7) to the two wire terminals respectively to form an electrical path to output the current change generated due to the resistance change caused by the hydrogen-induced resistance effect between the N-type graphene structure (3) and the P-type graphene structure (5).

6. The preparation method of the P-N junction hydrogen sensor of laser-induced graphene according to claim 5, wherein, The flexible substrate is a polyimide (PI) film, a polyetherimide (PEI) film, a polyetheretherketone (PEEK) film or a polyphenylene sulfide (PPS) film with a thickness between 10 μm and 10 mm, and porous structure graphene is generated by laser induction of a carbon dioxide light source with a power of 10 W to 100 W.

7. The preparation method of the P-N junction hydrogen sensor of laser-induced graphene according to claim 6, characterized in that, The laser-induced calcination temperature of the N-type graphene structure (3) is controlled between 250 °C and 450 °C, or between 800 °C and 1000 °C; The laser-induced calcination temperature of the P-type graphene structure (5) is controlled to be lower than 250 °C, or between 450 °C and 800 °C.

8. The preparation method of the P-N junction hydrogen sensor of laser-induced graphene according to claim 7, characterized in that, The metal particles (4) are platinum particles or palladium particles, and the deposited thickness is between 2 nm and 8 nm.

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