CN105510389A - Humidity sensor based on organic field-effect transistor and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of humidity sensors, and discloses a humidity sensor based on an organic field effect transistor and a preparation method thereof. It is used to solve the shortcomings of traditional resistive and capacitive humidity sensors with low sensitivity, high detection limit, difficulty in miniaturization and integration, and single detection parameter. The present invention includes a substrate, a gate electrode, a gate insulating layer and an organic semiconductor layer arranged in sequence from bottom to top, an active electrode and a drain electrode are connected above the organic semiconductor layer, and the organic semiconductor layer is made of a soluble organic semiconductor In this way, gelatin is added to the soluble organic semiconductor, and the volume ratio of the soluble semiconductor to gelatin is 4:1-? 9:1.

Description

A kind of humidity sensor based on organic field effect transistor and preparation method thereof

technical field

The invention belongs to the technical field of humidity sensors, and discloses a humidity sensor based on an organic field effect transistor and a preparation method thereof.

Background technique

Humidity is a physical quantity that indicates the dryness of the atmosphere. Accurate measurement of humidity has important uses in many aspects, such as medicine, meteorology, hydrology, and all aspects of industrial and agricultural production. The humidity sensor is an instrument that can accurately measure humidity, and it is at the core of the entire humidity detection equipment.

There are many types of humidity sensors, mainly including resistive humidity sensors, capacitive humidity sensors, electrolyte ion humidity sensors and weight humidity sensors. At present, the research hotspots at home and abroad are mainly resistive humidity sensor and capacitive humidity sensor. When water vapor is adsorbed on the surface of the material, the resistivity and permittivity of the device will change, so as to realize the effective detection of humidity. However, traditional resistive and capacitive humidity sensors have the disadvantages of low sensitivity, high detection limit, difficulty in miniaturization and integration, and single detection parameters; in contrast, organic field-effect transistors based on organic semiconductors (Organic Field-Effect Transistor, OFET) humidity sensor, as a new type of humidity sensor, compared with the traditional resistive humidity sensor and capacitive humidity sensor, in addition to having a wide range of material sources, simple process, long service life and the achievability of flexible substrates, etc. In addition, it has the advantages of fast response, high integration and multi-parameter detection. At the same time, the OFET humidity sensor meets the requirements of high intelligence and high sensitivity of market-oriented sensors, and has become a hot spot in the research field of new humidity sensors in recent years.

Contents of the invention

In order to solve the disadvantages of low sensitivity, high detection limit, difficulty in miniaturization and integration, and single detection parameters of traditional resistive and capacitive humidity sensors, the present invention provides a humidity sensor based on an organic field effect transistor and its The preparation method, by introducing a certain amount of gelatin into the organic semiconductor, enhances the adsorption of moisture by the OFET humidity sensor, and solves the problems of low sensitivity, few characteristic parameters, and low integration degree of the existing humidity sensor.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A humidity sensor based on an organic field-effect transistor, comprising a substrate, a gate electrode, a gate insulating layer, and an organic semiconductor layer arranged in sequence from bottom to top, and an active electrode and a drain electrode are connected above the organic semiconductor layer, which It is characterized in that the organic semiconductor layer is made of soluble organic semiconductor, gelatin is added to the soluble organic semiconductor, and the volume ratio of the soluble semiconductor to gelatin is 4:1-9:1.

The substrate is made of silicon wafer, glass, polymer film or metal foil.

The material of the gate insulating layer is an inorganic insulating material or an organic insulating material; the inorganic insulating material is silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), titanium dioxide (TiO ₂ ); the organic insulating material is polyvinyl alcohol (PVA), polyimide (PI), polystyrene (PS), polymethacrylate A combination of one or more of ester (PMMA) and polyethylene (PE); the thickness of the gate insulating layer is 20-520nm.

The soluble organic semiconductor is one or a combination of poly-3-hexylthiophene (P3HT) or Tips-Pentacene (Tips-Pentacene); the thickness of the organic semiconductor layer is 25-400 nm.

The material of the gate electrode, source electrode and drain electrode is one or more of gold, silver and copper; or the material of the gate electrode, source electrode and drain electrode is indium tin oxide conductive film or zinc tin oxide conductive film One or a combination of two; or the material of the gate electrode, source electrode and drain electrode is a conductive composite material, the conductive composite material is gold glue, silver glue or carbon glue, and the gate electrode, source electrode and drain electrode The thickness of the pole is 10 to 100 nm.

A method for preparing a humidity sensor based on an organic field effect transistor, comprising the following steps:

(1) cleaning the substrate, drying after cleaning; cleaning the substrate with detergent, acetone solution, deionized water and isopropanol solution;

(2) preparing a gate electrode on the surface of the substrate to form a pattern of the gate electrode;

(3) preparing a gate insulating layer on the gate electrode;

(4) Prepare an organic semiconductor layer on the gate insulating layer, perform miscibility according to the volume ratio of the soluble semiconductor solution and the gelatin solution at a ratio of 4:1-9:1, prepare a gelatin-organic semiconductor layer, and perform annealing treatment;

(5) preparing a source electrode and a drain electrode on the organic semiconductor layer;

(6) Packaging the organic field effect transistor obtained in step (5).

In the steps (2) and (5), the gate electrode, the source electrode and the drain electrode are formed by one of vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition, screen printing, printing or spin coating prepared by a method.

In the step (3), the gate insulating layer is prepared by one of plasma enhanced chemical vapor deposition, thermal oxidation, spin coating or vacuum evaporation.

In the step (4), the gelatin-organic semiconductor layer is a method of plasma enhanced chemical vapor deposition, thermal oxidation, spin coating, vacuum evaporation, roll coating, drop film, embossing, printing or air spray preparation.

The present invention introduces a certain amount of gelatin into the organic semiconductor layer, utilizes the unique material properties of gelatin, precisely regulates the morphology of the organic semiconductor layer film, controls the size of the semiconductor material crystal grains in the organic semiconductor, and controls the size of the semiconductor material grains in the organic semiconductor layer. Adjusted, the organic semiconductor layer will tend to form a morphology with smaller grains. When the grains are smaller, it means that there are more grain gaps in the organic semiconductor, which will help water molecules to diffuse into the carrier channel more quickly, so as to achieve better and faster humidity detection. .

At the same time, because gelatin has excellent water absorption properties, after mixing gelatin in the organic semiconductor layer, the adsorption of water molecules by the semi-organic semiconductor layer will be significantly improved, the lower limit of humidity detection can be significantly improved, and the purpose of rapid detection can be achieved at the same time.

Therefore compared with prior art, the present invention has following beneficial effect:

1. After introducing a certain amount of gelatin into the organic semiconductor layer, the response rate of humidity is significantly improved, and the lower limit of detection concentration is lower;

2. Compared with the existing resistive humidity sensor and capacitive humidity sensor, the humidity sensor based on field effect transistor has the advantages of multi-parameter detection, and can achieve the purpose of accurate detection through the monitoring of more parameters;

3. After a certain amount of gelatin is introduced into the organic semiconductor layer, the humidity sensor based on the organic field effect transistor will have a faster response speed and can realize rapid gas detection;

4. Gelatin is a kind of animal protein with wide sources, environment-friendly, low cost, simple preparation process, and easy industrialized large-scale production.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the change of device performance under different humidity conditions of the device prepared in embodiment 7; Wherein, _ION is saturation current, μ is carrier mobility, V _TH is threshold voltage, it can be seen that device is under different humidity conditions Under this condition, the performance parameters of the device have changed greatly, which has achieved the effect of accurate detection.

Marks in the figure: 1. substrate, 2. gate electrode, 3. gate insulating layer, 4. organic semiconductor layer, 5. source electrode, 6. drain electrode.

detailed description

The present invention will be further described below in conjunction with the embodiments, and the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other used embodiments obtained by persons of ordinary skill in the art without creative efforts all belong to the protection scope of the present invention.

With reference to the accompanying drawings, the humidity sensor based on the organic field effect transistor of the present invention includes a substrate 1, a gate electrode 2, a gate insulating layer 3 and an organic semiconductor layer 4 arranged sequentially from bottom to top, and the organic semiconductor layer 4 The active electrode 5 and the drain electrode 6 are connected above, the organic semiconductor layer 4 is made of a soluble organic semiconductor, gelatin is added to the soluble organic semiconductor, and the volume ratio of the soluble semiconductor to gelatin is 4:1-9: 1.

The substrate 1 can be a rigid substrate or a flexible substrate, such as one of silicon wafer, glass, polymer film and metal foil, which has a certain ability of waterproofing and oxygen penetration, and has better surface smoothness.

Gate electrode 2, source electrode 5 and drain electrode 6 are made of materials with low resistance, such as gold (Au), silver (Ag), magnesium (Mg), aluminum (Al), copper (Cu), calcium (Ca), Barium (Ba), nickel (Ni) and other metals and their alloy materials, the gate electrode, source electrode and drain electrode can use indium tin oxide (ITO), zinc tin oxide (IZO) conductive film and conductive composite materials, such as gold glue, Silver glue, carbon glue, etc., can be prepared by various deposition methods such as vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition, screen printing, printing, and spin coating. The thickness of the source electrode and the drain electrode is 10-100 nm.

The material of the gate insulating layer 3 is an inorganic insulating material or an organic insulating material; the inorganic insulating material is silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), a combination of one or more of titanium dioxide (TiO ₂ ); the organic insulating material is polyvinyl alcohol (PVA), polyimide (PI), polystyrene (PS), polymethacrylic acid A combination of one or more of methyl ester (PMMA) and polyethylene (PE); the thickness of the gate insulating layer is 20-520nm; the gate insulating layer is made by plasma enhanced chemical vapor deposition, thermal oxidation, spin It is prepared by one of the methods of coating or vacuum evaporation.

Soluble organic semiconductors are tetracene, pentacene and their derivatives with substituents, such as 6,13-ditriisopropyl silylacetylene pentacene, oligothiophene, which contains the second And four to eight thiophenes at the 5 position, perylene tetracarboxylic dianhydride (PTCDA), naphthalene tetracarboxylic dianhydride (NTCDA), copper phthalocyanine, zinc phthalocyanine, cobalt phthalocyanine, metallized phthalocyanine and its halogenated derivatives fluorinatedcopperphthalocyanine (F ₁₆ CuPc), copper phthalocyanine (CuPc), low copolymers and copolymers of thienylene and 1,2-vinylene, fullerene C60 and its derivatives, perylene and its derivatives, Alpha- Hexathiophene, rubrene (Rubrene), polythiophene Polythiophene or poly 3-hexylnaphene poly(3-hexythiophene), etc., the preparation method can be plasma enhanced chemical vapor deposition, thermal oxidation, spin coating, vacuum evaporation, drop film, embossing, printing or air jet, etc. The thickness of the organic semiconductor layer is 25-400nm.

The invention will be further described below in conjunction with specific embodiments.

Embodiment one

① Thoroughly clean the glass substrate on which the gate electrode ITO has been sputtered, and dry it with dry nitrogen after cleaning;

② Prepare a PS film on ITO by spin coating to form a gate insulating layer of 100nm;

③The spin-coated PS film is heated and baked;

④ Spin-coat P3HT on the gate insulating layer: 100nm of an organic semiconductor layer with a gelatin volume ratio of 90:10;

⑤ Copper source electrode and drain electrode 100nm were prepared by vacuum evaporation.

The humidity response characteristics of the device were tested, and the saturation current I _SD of the device was measured = 5 μA, the carrier mobility μ = 0.01×10 ^-3 cm ² /Vs, the threshold voltage V _TH = -4V, and there was no response to humidity at room temperature. response.

Embodiment two

① Thoroughly clean the glass substrate 1 on which the gate electrode ITO has been sputtered, and dry it with dry nitrogen after cleaning;

② Prepare a PMMA film on ITO by spin coating to form a gate insulating layer of 520nm;

③Heating and baking the spin-coated PMMA film;

4. Spin-coat P3HT on the gate insulating layer: the organic semiconductor layer 150nm of gelatin volume ratio is 85:15;

⑤ Vacuum evaporation is used to prepare silver source electrode and drain electrode 10nm.

The humidity response characteristics of the device were tested, and the measured saturation current I _SD = 7μA, carrier mobility μ = 0.008×10 ^-3 cm ² /Vs, threshold voltage V _TH = -9V, and the response to humidity at room temperature Difference.

Embodiment three

① Thoroughly clean the glass substrate 1 on which the gate electrode ITO has been sputtered, and dry it with dry nitrogen after cleaning;

② Prepare a PVA film on ITO by spin coating method to form a 20nm gate insulating layer;

③The spin-coated PVA film is heated and baked;

④ Spin-coat P3HT on the gate insulating layer: 200nm of an organic semiconductor layer with a gelatin volume ratio of 80:20;

⑤ Prepare gold source electrode and drain electrode 40nm by vacuum evaporation.

The humidity response characteristics of the device were tested, and the saturation current I _SD = 9μA, the carrier mobility μ = 0.02×10 ^-3 cm ² /Vs, the threshold voltage V _TH = -8V, and the response to humidity at room temperature were measured. it is good.

Embodiment Four

① Thoroughly clean the substrate with silicon as the gate electrode, and dry it with dry nitrogen after cleaning;

② A layer of 20nm SiO ₂ is formed as a gate insulating layer by thermal oxidation or vapor deposition;

3. Prepare Tips-Pentacene by spin coating on the gate insulating layer: the organic semiconductor layer 25nm of gelatin volume ratio is 88:12;

④ Vacuum evaporation is used to prepare gold source electrode and drain electrode 60nm.

The humidity response characteristics of the device were tested, and the measured saturation current I _SD = 15μA, carrier mobility μ = 0.05×10 ^-3 cm ² /Vs, threshold voltage V _TH = -6V, corresponding to humidity at room temperature poor.

Embodiment five

① Thoroughly clean the substrate with silicon as the gate electrode, and dry it with dry nitrogen after cleaning;

② Prepare a 300nm polyvinylpyrrolidone film on ITO by spin coating to form a gate insulating layer;

③The spin-coated polyvinylpyrrolidone film is heated and baked;

④ Spin coating on the gate insulating layer to prepare Tips-Pentacene: gelatin volume ratio of 84:16 organic semiconductor layer 300nm;

⑤ Vacuum evaporation is used to prepare silver source electrode and drain electrode 70nm.

The humidity response characteristics of the device were tested, and the saturation current I _SD of the device was measured to be 17μA, the carrier mobility μ=0.06×10 ^-3 cm ² /Vs threshold voltage V _TH =-8V, and the corresponding humidity was moderate at room temperature .

Embodiment six

① Thoroughly clean the glass substrate on which the gate electrode ITO has been sputtered, and dry it with dry nitrogen after cleaning;

②Using reactive magnetron sputtering to prepare a 50nm aluminum oxide film on ITO to form a gate insulating layer;

③ Prepare Tips-Pentacene by spin coating on the gate insulating layer: an organic semiconductor layer 350nm with a gelatin volume ratio of 82:18;

④ Vacuum evaporation is used to prepare 80nm copper source and drain electrodes.

The humidity response characteristics of the device were tested, and the measured saturation current I _SD = 25μA, carrier mobility μ = 0.04×10 ^-3 cm ² /Vs, threshold voltage V _TH = -5V, corresponding to humidity at room temperature it is good.

Embodiment seven

① Thoroughly clean the glass substrate 1 on which the gate electrode ITO has been sputtered, and dry it with dry nitrogen after cleaning;

②Using reactive magnetron sputtering to prepare a 50nm silicon nitride film on ITO to form a gate insulating layer;

③ Prepare Tips-Pentacene by spin coating on the gate insulating layer: an organic semiconductor layer 400nm with a gelatin volume ratio of 80:20;

④ Vacuum evaporation is used to prepare gold source electrode and drain electrode 80nm.

The humidity response characteristics of the device were tested, and the measured saturation current I _SD = 20μA, carrier mobility μ = 0.01×10 ^-3 cm ² /Vs, threshold voltage V _TH = -6V, corresponding to humidity at room temperature very good.

Table 1: Adding different proportions of gelatin device performance parameters table

Organic semiconductor material and gelatin ratio I _SD (μA) Response to Humidity at Room Temperature P3HT: Gelatin 90:10 5 No response P3HT: Gelatin 85:15 7 Difference P3HT: Gelatin 80:20 9 it is good TIPs-Pentacene: Gelatin 88:12 15 Difference TIPs-Pentacene: Gelatin 84:16 17 medium TIPs-Pentacene: Gelatin 82:18 25 it is good TIPs-Pentacene: Gelatin 80:20 20 very good

Claims (9)

1. A humidity sensor based on an organic field effect transistor, comprising a substrate, a gate electrode, a gate insulating layer and an organic semiconductor layer arranged in sequence from bottom to top, and the top of the organic semiconductor layer is connected with a source electrode and a drain electrode , wherein the organic semiconductor layer is made of a soluble organic semiconductor, gelatin is added to the soluble organic semiconductor, and the volume ratio of the soluble semiconductor to gelatin is 4:1-9:1. 2. The humidity sensor based on an organic field effect transistor according to claim 1, wherein the substrate is made of silicon wafer, glass, polymer film or metal foil. 3. the humidity sensor based on organic field effect transistor according to claim 1, is characterized in that, the material of described grid insulating layer is inorganic insulating material or organic insulating material; Described inorganic insulating material is silicon dioxide, three A combination of one or more of aluminum oxide, silicon nitride or titanium dioxide; the organic insulating material is one of polyvinyl alcohol, polyimide, polystyrene, polymethyl methacrylate or polyethylene combination of one or more; the thickness of the gate insulating layer is 20-520nm. 4. the humidity sensor based on organic field effect transistor according to claim 1, is characterized in that, described soluble organic semiconductor is the combination of one or both in poly-3-hexylthiophene or Tips-pentacene; The thickness of the organic semiconductor layer is 25-400 nm. 5. The humidity sensor based on an organic field effect transistor according to claim 1, wherein the material of the gate electrode, the source electrode and the drain electrode is one or more of gold, silver, copper; The material of the electrode, the source electrode and the drain electrode is one or a combination of indium tin oxide conductive film or zinc tin oxide conductive film; the thickness of the gate electrode, source electrode and drain electrode is 10-100 nm. 6. A method for preparing a humidity sensor based on an organic field effect transistor, comprising the following steps: (1) The substrate is cleaned and dried after cleaning; (2) preparing a gate electrode on the surface of the substrate to form a pattern of the gate electrode; (3) preparing a gate insulating layer on the gate electrode; (4) Prepare an organic semiconductor layer on the gate insulating layer, perform miscibility according to the volume ratio of the soluble semiconductor solution and the gelatin solution at a ratio of 4:1-9:1, prepare a gelatin-organic semiconductor layer, and perform annealing treatment; (5) preparing a source electrode and a drain electrode on the organic semiconductor layer; (6) Packaging the organic field effect transistor obtained in step (5). 7. the preparation method of the humidity sensor based on organic field effect transistor according to claim 6 is characterized in that, in described step (2) and (5), gate electrode, source electrode, drain electrode are by vacuum thermal evaporation Plating, magnetron sputtering, plasma enhanced chemical vapor deposition, screen printing, printing or spin coating. 8. the preparation method of the humidity sensor based on organic field effect transistor according to claim 6 is characterized in that, in described step (3), grid insulating layer is by plasma enhanced chemical vapor deposition, thermal oxidation, spin It is prepared by one of the methods of coating or vacuum evaporation. 9. the preparation method of the humidity sensor based on organic field effect transistor according to claim 6, is characterized in that, in described step (4), gelatin-organic semiconductor layer is by plasma enhanced chemical vapor deposition, thermal oxidation, Prepared by one of spin coating, vacuum evaporation, roll coating, drop film, embossing, printing or air spraying.