A photosensitive capacitor and its preparation method

Abstract

The present invention belongs to the technical field of capacitors and specifically relates to a photosensitive capacitor and a preparation method thereof. The photosensitive capacitor includes an upper plate, an upper electrode, a CuWO4-TiO2 dielectric layer, a lower electrode, a lower plate and a conductive wire, wherein the lower plate is arranged below the lower electrode, the upper plate is arranged above the upper electrode, the CuWO4-TiO2 dielectric layer is located between the upper electrode and the lower electrode, two conductive wires are provided, respectively connecting the upper electrode and the lower electrode, the CuWO4-TiO2 dielectric layer is obtained by sintering CuWO4 on both sides of a titanium dioxide film, and the present invention modifies and composites rutile titanium dioxide with CuWO4 as a dielectric layer, forms a stable crystal interface between CuWO4 and rutile titanium dioxide, and photons of visible light incident on the CuWO4 can excite holes generated by electrons, inducing the rutile titanium dioxide to generate small polarons, thereby maintaining a relatively high dielectric constant, so that the photosensitive capacitor can effectively utilize sunlight to regulate capacitance.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular to a photosensitive capacitor and a preparation method thereof. Background Art

[0002] The photocapacitance effect is an internal photoelectric effect, referring to the change in the dielectric constant or capacitance constant of a semiconductor or insulating material when exposed to external light. Generally, the photocapacitance of most semiconductors or insulators does not change significantly. However, experiments have shown that the photovaricapacitance effect is very significant under strong radiation conditions or in certain special materials (such as ZnS-CdS, SrTiO3, and organic polymers). The influence of photovaricapacitance must be considered in the design of precision electronic instruments, and capacitor elements must be shielded from light. The photocapacitance effect also has important potential applications in the optoelectronic field. A photosensitive capacitor is an optoelectronic device based on the principle of the photovaricapacitance effect. By adjusting the light exposure, its internal capacitance is changed, thereby achieving capacitance control in the circuit.

[0003] Chinese patent CN201510465003.7 discloses a photosensitive capacitor based on the small polaron effect, in which the dielectric material layer is made of TiO2, and a conductive layer and an encapsulation layer are sequentially provided on both sides of the dielectric material layer. However, the TiO2 band gap value is high, and the utilization of sunlight is insufficient, which limits its scope of application. TiO2 can be modified by element doping or by coupling with other semiconductor materials, but because its grain boundaries are affected during the TiO2 modification process, the change in grain boundaries will cause the dielectric constant to decrease, which is a major obstacle to the improvement of photosensitive capacitors. Therefore, it is urgent to develop a photosensitive capacitor that can efficiently utilize sunlight without reducing the dielectric constant, so as to expand its practical application range. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In view of the deficiencies in the prior art, the present invention provides a photosensitive capacitor and a method for preparing the same, with the aim of solving the problems of insufficient utilization of sunlight and reduced dielectric constant in conventional modified photosensitive capacitors.

[0006] (2) Technical solution

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A photosensitive capacitor includes an upper plate, an upper electrode, a CuWO4-TiO2 dielectric layer, a lower electrode, a lower plate, and a conductive wire. The lower plate is arranged below the lower electrode, the upper plate is arranged above the upper electrode, the CuWO4-TiO2 dielectric layer is located between the upper electrode and the lower electrode, two conductive wires are provided, connecting the upper electrode and the lower electrode respectively, and the CuWO4-TiO2 dielectric layer is obtained by sintering CuWO4 on both sides of a titanium dioxide film.

[0009] Preferably, the upper plate and the lower plate have a thickness of 200-300 μm and are transparent organic glass plates.

[0010] Preferably, the upper electrode is a columnar metal aluminum thin film layer with a thickness of 80-130 nm and a diameter of 2-4 mm.

[0011] Preferably, the lower electrode is a metallic silver thin film layer with a thickness of 80-130 nm.

[0012] Preferably, the titanium dioxide film is a rutile titanium dioxide film with a thickness of 100±10 nm.

[0013] The preparation method of the photosensitive capacitor proposed by the present invention is as follows:

[0014] (1) Cu(NO3)2 is added to acetic acid to form solution A, tungsten powder is dissolved in concentrated hydrogen peroxide solution, and stirred in an ice bath, then solution A is added and stirred continuously to react into a sol state to obtain a CuWO4 precursor sol;

[0015] (2) Pour half of the CuWO4 precursor sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread the rutile titanium dioxide film on the surface of the CuWO4 sol, and then evenly coat the remaining CuWO4 sol on the surface of the rutile titanium dioxide film, and pressurize it unidirectionally under normal pressure to form a composite layer, and transfer the composite layer to a muffle furnace for annealing to obtain a CuWO4-TiO2 dielectric layer;

[0016] (3) Assembly: Cut the upper plate, metal aluminum film layer, CuWO4-TiO2 dielectric layer, metal silver film layer and lower plate into the same length and width, and stack them in sequence. During the stacking process, insert two wires between the upper plate and the metal aluminum film layer, and between the metal silver film layer and the lower plate, respectively, and then apply unidirectional pressure to form a photosensitive capacitor.

[0017] Preferably, the mass fraction of Cu(NO3)2 in acetic acid in solution A of step (1) is 30%, the mass ratio of Cu(NO3)2, tungsten powder and concentrated hydrogen peroxide is 4.5-4.8:2:10-12, and the concentration of hydrogen peroxide is 20%.

[0018] Preferably, in the step (2), the pressurizing pressure is 250-350 MPa, the holding time is 3-5 min, the annealing temperature is 600-650° C., and the annealing time is 2-4 h.

[0019] Preferably, the pressurizing pressure in step (3) is 200-300 MPa, and the pressure holding time is 3-5 min.

[0020] (3) Beneficial technical effects

[0021] (1) The present invention proposes a photosensitive capacitor, which uses CuWO4 to modify and composite rutile titanium dioxide as a dielectric layer, and the grain boundaries serve as electron-hole recombination centers. CuWO4 has a lower band gap than titanium dioxide and can effectively absorb most of the visible light in the solar spectrum. Photons incident on CuWO4 can excite electrons to enter the conduction band of the semiconductor and leave holes in the valence band. These holes will induce rutile titanium dioxide to produce small polarons, maintaining a high dielectric constant, which can effectively increase the capacitance of the photosensitive capacitor. After the light is removed, since the small polarized molecules have a relatively long life, the increased dielectric constant in the dielectric layer decays very slowly, so that the photosensitive capacitor can effectively use sunlight to regulate the capacitance;

[0022] (2) The present invention proposes a photosensitive capacitor and a preparation method thereof, wherein CuWO4 sol is spread on both sides of a rutile titanium dioxide film and pressed tightly so that CuWO4 and the rutile titanium dioxide film are in close contact, followed by high-temperature calcination and annealing. During the sintering process, the residual hydrogen peroxide contained in the CuWO4 sol promotes the chemical bonding between titanium dioxide and CuWO4 to form a dielectric layer. The composite of CuWO4 and TiO2 improves the charge separation efficiency of the dielectric layer system and expands its spectral response range. The dielectric layer is assembled with various components to obtain a photosensitive capacitor;

[0023] (3) The present invention proposes a photosensitive capacitor and a preparation method thereof, which uses CuWO4 to modify and composite rutile titanium dioxide as a dielectric layer. Compared with mixed doping, CuWO4 forms a stable crystal interface between rutile titanium dioxide and the grain boundary, which acts as an electron-hole recombination center, providing a basis for maintaining a higher dielectric constant. DETAILED DESCRIPTION

[0024] To achieve the above object, the present invention provides the following embodiments and comparative examples:

[0025] Example 1

[0026] A method for preparing a photosensitive capacitor is as follows:

[0027] (1) Add 4.5g of Cu(NO3)2 to 10.5g of acetic acid to form solution A, dissolve 2g of tungsten powder in 10g of 20% hydrogen peroxide solution, and stir in an ice bath. Then add solution A and continue stirring to react into a sol state to obtain a CuWO4 precursor sol;

[0028] (2) Pour half of the CuWO4 precursor sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread a 100 nm thick rutile titanium dioxide film on the surface of the CuWO4 sol, and then evenly coat the remaining CuWO4 sol on the surface of the rutile titanium dioxide film. Pressurize the composite layer under normal pressure with a unidirectional pressure of 250 MPa and a holding time of 5 min, and transfer the composite layer to a muffle furnace and anneal at 550 ° C for 2 h to obtain a CuWO4-TiO2 dielectric layer.

[0029] (3) Assembly: Cut the transparent organic glass plate, the metal aluminum film layer, the CuWO4-TiO2 dielectric layer, the metal silver film layer and the transparent organic glass plate into a 3 cm × 4 cm rectangle and stack them in sequence. During the stacking process, insert two wires between the transparent organic glass plate and the metal aluminum film layer, and between the metal silver film layer and the transparent organic glass plate, respectively. Then, apply a unidirectional pressure of 200 MPa and maintain the pressure for 5 minutes to make a photosensitive capacitor.

[0030] Example 2

[0031] A method for preparing a photosensitive capacitor is as follows:

[0032] (1) Add 4.8g of Cu(NO3)2 to 11.2g of acetic acid to form solution A, dissolve 2g of tungsten powder in 11g of 20% hydrogen peroxide solution, and stir in an ice bath. Then add solution A and continue stirring to react into a sol state to obtain a CuWO4 precursor sol;

[0033] (2) Pour half of the CuWO4 precursor sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread a 110 nm thick rutile titanium dioxide film on the surface of the CuWO4 sol, and then evenly coat the remaining CuWO4 sol on the surface of the rutile titanium dioxide film. Pressurize the composite layer under normal pressure with a unidirectional pressure of 265 MPa and a holding time of 4 minutes, and transfer the composite layer to a muffle furnace and anneal at 600 ° C for 2 hours to obtain a CuWO4-TiO2 dielectric layer.

[0034] (3) Assembly: Cut the transparent organic glass plate, the metal aluminum film layer, the CuWO4-TiO2 dielectric layer, the metal silver film layer and the transparent organic glass plate into a 3 cm × 4 cm rectangle and stack them in sequence. During the stacking process, insert two wires between the transparent organic glass plate and the metal aluminum film layer, and between the metal silver film layer and the transparent organic glass plate, respectively. Then, apply a unidirectional pressure of 250 MPa and maintain the pressure for 4 minutes to make a photosensitive capacitor.

[0035] Example 3

[0036] A method for preparing a photosensitive capacitor is as follows:

[0037] (1) Add 9.6g of Cu(NO3)2 to 22.4g of acetic acid to form solution A, dissolve 4g of tungsten powder in 21g of 20% hydrogen peroxide solution, and stir in an ice bath. Then add solution A and continue stirring to react into a sol state to obtain a CuWO4 precursor sol;

[0038] (2) Pour half of the CuWO4 precursor sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread a 90nm thick rutile titanium dioxide film on the surface of the CuWO4 sol, and then evenly coat the remaining CuWO4 sol on the surface of the rutile titanium dioxide film. Pressurize the composite layer under normal pressure with a unidirectional pressure of 300 MPa and a holding time of 4.5 minutes, and transfer the composite layer to a muffle furnace and anneal at 650°C for 2 hours to obtain a CuWO4-TiO2 dielectric layer.

[0039] (3) Assembly: Cut the transparent organic glass plate, the metal aluminum film layer, the CuWO4-TiO2 dielectric layer, the metal silver film layer and the transparent organic glass plate into a 3 cm × 4 cm rectangle and stack them in sequence. During the stacking process, insert two wires between the transparent organic glass plate and the metal aluminum film layer, and between the metal silver film layer and the transparent organic glass plate, respectively. Then, apply a unidirectional pressure of 300 MPa and maintain the pressure for 4.5 minutes to make a photosensitive capacitor.

[0040] Example 4

[0041] A method for preparing a photosensitive capacitor is as follows:

[0042] (1) Add 6.9g of Cu(NO3)2 to 16.1g of acetic acid to form solution A, dissolve 3g of tungsten powder in 18g of 20% hydrogen peroxide solution, and stir in an ice bath. Then add solution A and continue stirring to react into a sol state to obtain a CuWO4 precursor sol;

[0043] (2) Pour half of the CuWO4 precursor sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread a 100 nm thick rutile titanium dioxide film on the surface of the CuWO4 sol, and then evenly coat the remaining CuWO4 sol on the surface of the rutile titanium dioxide film. Pressurize the mixture into a composite layer under normal pressure with a unidirectional pressure of 350 MPa and maintain the pressure for 3 minutes. Transfer the composite layer to a muffle furnace and anneal at 620°C for 2 hours to obtain a CuWO4-TiO2 dielectric layer.

[0044] (3) Assembly: Cut the transparent organic glass plate, the metal aluminum film layer, the CuWO4-TiO2 dielectric layer, the metal silver film layer and the transparent organic glass plate into a 3 cm × 4 cm rectangle and stack them in sequence. During the stacking process, insert two wires between the transparent organic glass plate and the metal aluminum film layer, and between the metal silver film layer and the transparent organic glass plate, respectively. Then, apply a unidirectional pressure of 300 MPa and maintain the pressure for 3 minutes to make a photosensitive capacitor.

[0045] Comparative Example 1

[0046] A method for preparing a photosensitive capacitor is as follows:

[0047] (1) Dissolve 2 g of tungsten powder in 10 g of 20% hydrogen peroxide solution and stir in an ice bath to form a sol state to obtain a precursor sol;

[0048] (2) Pour half of the precursor sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread a 100 nm thick rutile titanium dioxide film on the surface of the sol, and then evenly coat the remaining sol on the surface of the rutile titanium dioxide film. Pressurize the composite layer under normal pressure with a unidirectional pressure of 250 MPa and a holding time of 5 minutes, and transfer the composite layer to a muffle furnace and anneal at 550°C for 2 hours to obtain a dielectric layer.

[0049] (3) Assembly: Cut the transparent organic glass plate, the metal aluminum film layer, the dielectric layer, the metal silver film layer and the transparent organic glass plate into rectangles of 3 cm × 4 cm and stack them in sequence. During the stacking process, insert two wires between the transparent organic glass plate and the metal aluminum film layer, and between the metal silver film layer and the transparent organic glass plate, respectively. Then, apply unidirectional pressure of 200 MPa and hold the pressure for 5 minutes to make a photosensitive capacitor.

[0050] Comparative Example 2

[0051] A method for preparing a titanium dioxide photosensitive capacitor is as follows:

[0052] (1) Add 6.9 g of Cu(NO3)2 to 16.1 g of acetic acid to form solution A;

[0053] (2) Lay a 100 nm thick anatase titanium dioxide film flat, take half of the solution A prepared in step (1) and spray it on the front side of the anatase titanium dioxide film, dry it in an oven at 80°C for 10 min, then spray the remaining solution A on the back side of the anatase titanium dioxide film, dry it in an oven at 80°C for 10 min, transfer it to a muffle furnace and anneal it at 550°C for 2 h to obtain a dielectric layer;

[0054] (3) Assembly: Cut the transparent organic glass plate, the metal aluminum film layer, the dielectric layer, the metal silver film layer and the transparent organic glass plate into rectangles of 3 cm × 4 cm and stack them in sequence. During the stacking process, insert two wires between the transparent organic glass plate and the metal aluminum film layer, and between the metal silver film layer and the transparent organic glass plate, respectively. Then, apply unidirectional pressure of 200 MPa and hold the pressure for 5 minutes to make a photosensitive capacitor.

[0055] 1) Dielectric constant and dielectric loss test: Under a light intensity of 40mW / cm 2 Under white light irradiation, the test bias voltage is 15V, and the dielectric constant and capacitance loss tangent of the photosensitive capacitors obtained in Examples 1-4 and Comparative Examples 1-2 are measured using an LCR meter. The frequency is set to 1MHz. The test results are shown in Table 1.

[0056] Table 1:

[0057] project Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Dielectric constant 153.2 153.5 152.9 153.2 122.3 82.5 Capacitor loss tangent 0.0013 0.0014 0.0015 0.0013 0.0043 0.0052

[0058] 2) With a test bias of 15 V and different light intensities, the dielectric constant and capacitance loss tangent of the photosensitive capacitors obtained in Examples 1-4 and Comparative Examples 1-2 were measured using an LCR meter. The frequency was set to 1 MHz. The test results are shown in Table 2.

[0059] Table 2:

[0060]

[0061] In summary, according to the above table, the dielectric constants of the photosensitive capacitors prepared in the examples and comparative examples are improved with the increase of white light irradiation intensity, and their capacitance loss tangent values ​​also increase with the increase of white light irradiation intensity. However, the increase in the dielectric constant of Examples 1-4 is greater than that of the comparative example, and the increase in the capacitance loss tangent values ​​of Examples 1-4 is much smaller than that of the comparative example. The dielectric layer of the photosensitive capacitor in Comparative Example 2 is modified only with copper ions to modify anatase titanium dioxide, and its dielectric constant and capacitance loss tangent values ​​are the worst. The dielectric layer of the photosensitive capacitor in Comparative Example 1 is modified only with tungsten oxide to modify titanium dioxide, and its dielectric properties are between Examples 1-4 and Comparative Example 2, indicating that the photosensitive capacitor provided by the present invention and its preparation method have great prospects for use in sunlight.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the claims of the present invention.

Claims

1. A photosensitive capacitor, characterized in that: The device comprises an upper plate, an upper electrode, a CuWO4-TiO2 dielectric layer, a lower electrode, a lower plate and a conductive wire, wherein the lower plate is arranged below the lower electrode, the upper plate is arranged above the upper electrode, the CuWO4-TiO2 dielectric layer is located between the upper electrode and the lower electrode, two conductive wires are provided, connecting the upper electrode and the lower electrode respectively, and the CuWO4-TiO2 dielectric layer is obtained by sintering CuWO4 on both sides of the titanium dioxide film; The method for preparing the photosensitive capacitor comprises the following steps: (1) Cu(NO3)2 is added to acetic acid to form solution A, tungsten powder is dissolved in concentrated hydrogen peroxide solution, and stirred in an ice bath. Then, solution A is added and stirred continuously to react into a sol state to obtain a CuWO4 precursor sol; (2) Pour half of the CuWO4 sol prepared in step (1) into a flat-bottom mold and evenly spread it, then spread the rutile titanium dioxide film on the surface of the CuWO4 sol, and then evenly coat the remaining CuWO4 sol on the surface of the rutile titanium dioxide film, and pressurize it unidirectionally under normal pressure to form a composite layer, and transfer the composite layer to a muffle furnace for annealing to obtain a CuWO4-TiO2 dielectric layer; (3) Assembly: Cut the upper plate, metal aluminum film layer, CuWO4-TiO2 dielectric layer, metal silver film layer and lower plate into the same length and width, and stack them in sequence. During the stacking process, insert two conductive wires between the upper plate and the metal aluminum film layer, and between the metal silver film layer and the lower plate, respectively, and then apply unidirectional pressure to form a photosensitive capacitor.

2. A photosensitive capacitor according to claim 1, characterized in that: The thickness of the upper plate and the lower plate is 200-300 μm, and they are transparent organic glass plates.

3. The photosensitive capacitor according to claim 1, characterized in that: The upper electrode is a columnar metal aluminum thin film layer with a thickness of 80-130 nm and a diameter of 2-4 mm.

4. The photosensitive capacitor according to claim 1, wherein: The lower electrode is a metallic silver thin film layer with a thickness of 80-130 nm.

5. The photosensitive capacitor according to claim 1, characterized in that: The titanium dioxide film is a rutile titanium dioxide film with a thickness of 100±10 nm.

6. The photosensitive capacitor according to claim 1, characterized in that: The mass fraction of Cu(NO3)2 in acetic acid in solution A of step (1) is 30%, the mass ratio of Cu(NO3)2, tungsten powder and concentrated hydrogen peroxide is 4.5-4.8:2:10-12, and the concentration of hydrogen peroxide is 20%.

7. The photosensitive capacitor according to claim 1, characterized in that: In the step (2), the pressurizing pressure is 250-350 MPa, the holding time is 3-5 min, the annealing temperature is 600-650° C., and the annealing time is 2-4 h.

8. The photosensitive capacitor according to claim 1, characterized in that: In step (3), the pressurization pressure is 200-300 MPa, and the pressure holding time is 3-5 minutes.

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