CN105679937A - Double-gate structured photosensitive organic field-effect transistor and preparation method therefor - Google Patents

Abstract

The invention provides a double-gate structured photosensitive organic field-effect transistor and a preparation method therefor. The structure of the photosensitive organic field-effect transistor, as shown in the figure 1, comprises a top gate electrode (1), a top gate insulating layer (2), an organic semiconductor layer (3), a source electrode (4), a drain electrode (5), a bottom gate insulating layer (6) and a bottom gate electrode (7). According to the double-gate structured photosensitive organic field-effect transistor, the top gate electrode and the bottom gate electrode can be used for controlling the on and off of the transistor respectively as well as can be used fro controlling the on and off of the transistor synchronously; the bottom gate is covered with the bottom gate insulating layer; the two sides of the bottom gate insulating layer are covered with the source electrode and the drain electrode, and a channel is formed in the middle part; the channel and the electrode are covered with the organic semiconductor layer; the organic semiconductor layer is covered with the top gate insulating layer; the top gate insulating layer is covered with the top gate; the bottom gate electrode and the top gate electrode are made from the same material; and the bottom gate insulating layer and the top gate insulating layer are made from the same material having symmetrical material structures.

Description

Photosensitive organic field-effect transistor with double gate structure and preparation method thereof

technical field

The invention belongs to the field of organic thin film devices, in particular to a photosensitive organic field effect transistor with double gate structure.

Background technique

With the development of semiconductor technology, the current electronic information industry with integrated circuits as its core has surpassed the traditional petroleum, steel, and automobile industries, becoming the world's largest industry, driving the development of all walks of life and economic progress. According to Moore's Law, the number of components that can be accommodated on an integrated circuit will double every 18-24 months, and the performance will also double. At present, in the latest integrated circuit manufacturing process, the feature size of transistors has reached 14nm, but as the integration of integrated circuits becomes higher and higher, the feature size becomes smaller and smaller, and some problems appear, such as quantum tunneling. These problems will limit the development of traditional inorganic semiconductors. Scientists have also proposed to improve the device structure and use high dielectric constant materials as the dielectric layer to solve the current problems, but in the long run, they must be solved fundamentally. The problem must employ new materials and methods. Since it was discovered that doped polyacetylene can conduct electricity, replacing traditional inorganic semiconductor materials with organic substances has become a hot topic in research, and a new discipline has emerged—organic electronics. Organic substances as semiconductor materials have more There are many advantages, such as countless materials, which can be chemically synthesized and modified to meet various needs. The most important thing is that organic materials are flexible, can be prepared in large areas, and are suitable for low-cost production processes such as printing, printing, and spin coating. Compared with photosensitive non-field-effect transistors, photosensitive organic field-effect transistors (photosenitive organic field-effect transistors, photoOFETs) have the advantages of high photoresponsivity, large-area and low-cost manufacturing, and environmentally friendly manufacturing processes. Generally, a photosensitive organic field effect transistor is composed of a substrate, a gate, a gate dielectric, an organic photosensitive layer, a source and a drain. In order to obtain more practical applications, the performance of OTFTs needs to be further improved and improved. In the article, lead phthalocyanine (PbPc) was used as the organic semiconductor material to prepare an organic photosensitive field effect transistor with double gate structure. This paper presents an organic photoFET fabricated with a dual-gate structure, a device with two gates, better control over the conduction channel, and a larger operating voltage at a lower operating voltage. Output current, compared with single-gate organic thin film transistors, field effect mobility and current switching ratio are higher. Organic photosensitive organic field-effect transistors are more and more popular due to their low cost, good flexibility, and easy processing, and have been widely used in low-end devices.

Contents of the invention

The object of the present invention is to provide a photosensitive organic field effect transistor with a double gate structure and a preparation method thereof.

A photosensitive organic field effect transistor with a double gate structure provided by the present invention has a structure as shown in Figure 1, comprising a top gate electrode (1), a top gate insulating layer (2), an organic semiconductor layer (3), a source electrode (4), a drain electrode (5), a bottom gate insulating layer (6), and a bottom gate electrode (7). The bottom gate insulating layer is covered on the bottom gate electrode, the source electrode and the drain electrode are respectively covered on both sides of the bottom gate insulating layer, the middle part forms a channel, and the organic semiconductor layer is covered on the channel and the source electrode and the drain electrode. The top gate insulating layer is covered on the organic semiconductor layer, and the top gate electrode is covered on the top gate insulating layer; in this transistor, the material constituting the bottom gate electrode and the top gate electrode is ITO, which constitutes the bottom gate insulating layer and the top gate electrode. The material of the insulating layer is PVP, the material of the source electrode and the drain electrode is gold, and the material of the organic semiconductor layer is lead phthalocyanine; the transistor adopts a completely symmetrical structure, and the thickness of the top gate insulating layer and the bottom gate insulating layer are exactly the same.

When irradiated by near-infrared light with a wavelength of 780-980nm, the output current increases obviously.

Applying the top gate electrode voltage or the bottom gate electrode voltage respectively can control the opening and closing of the transistor, and applying voltage to the top gate electrode and the bottom gate electrode at the same time can increase the carrier mobility of the organic field effect transistor; A photosensitive organic field effect transistor with double gate structure has three working modes:

1. When the bottom gate electrode voltage is applied, the channel is turned on, and the source electrode and drain electrode of the organic field effect transistor are turned on;

2. When the top gate electrode voltage is applied, the channel is turned on, and the source electrode and drain electrode of the organic field effect transistor are turned on;

3. When the top gate voltage and the bottom gate voltage are applied at the same time, the output current of the source electrode and the drain electrode of the organic field effect transistor increases relative to the above two operating modes;

The method for preparing the photosensitive organic field-effect transistor of above-mentioned double-gate structure provided by the present invention comprises the following steps:

1) preparing a bottom gate electrode on the cleaned glass substrate;

2) preparing a bottom gate insulating layer on the bottom gate electrode obtained in step 1);

3) preparing a source electrode and a drain electrode on the substrate with a bottom gate insulating layer obtained in step 2);

4) preparing an organic semiconductor layer on the basis obtained in the step 3);

5) preparing a top gate insulating layer on the semiconductor layer obtained in step 4);

6) preparing a top gate electrode on the top gate insulating layer obtained in step 5);

In step 1) of the above-mentioned preparation method, the material of the bottom grid electrode is ITO, and the glass substrate is respectively ultrasonically cleaned with acetone, ethanol, and deionized water for 15 minutes; the method for preparing the bottom grid electrode is magnetron sputtering, magnetron sputtering The working pressure of sputtering is 2.5Pa, the vacuum degree is below 3.0×10 ^-3 Pascal, the sputtering power is 140W, the deposition rate is 5 angstroms/second, and the deposition time is 20 minutes;

The method for preparing the bottom gate insulating layer in step 2) is vacuum thermal evaporation, the vacuum degree is below 1.5×10 ^-3 Pascal, and the evaporation rate is 0.1 angstroms/second;

In step 3), a sacrificial layer is first prepared by photolithography, a layer of negative resist is applied on the bottom gate insulating layer, and a mask is used to cover it. After exposure and hardening, a strong acid is used to remove the part covered by the mask. The exposed area is used to prepare the source electrode and the drain electrode; the method for preparing the source electrode and the drain electrode is vacuum thermal evaporation, the vacuum degree is below 1.5×10 ^-3 Pascal, and the evaporation rate is 1 angstrom/second;

The preparation method of the organic semiconductor layer in step 4) is vacuum thermal evaporation, the vacuum degree is below 3×10 ^-4 Pascal, and the evaporation rate is 0.5 angstroms/second;

The method for preparing the top gate insulating layer in step 5) is vacuum thermal evaporation, the vacuum degree is below 1.5×10 ^-3 Pascal, and the evaporation rate is 0.1 Å/s;

The material for preparing the top gate electrode in step 6) is ITO conductive glass, the method is magnetron sputtering, the working pressure is 2.5 Pascals, the vacuum degree is below 3.0×10 ^-3 Pascals, the sputtering power is 140 watts, and the deposition rate is 5 Angstroms/sec, and the deposition time was 20 minutes.

Technical analysis of the present invention:

The organic semiconductor layer of the double-gate photosensitive organic transistor is lead phthalocyanine (PbPc), which is a small molecule photosensitive organic material and is very sensitive to near-infrared light with a wavelength range of 780-980nm. In addition, the double-gate transistor has three working modes, which are top-gate mode, bottom-gate mode, and double-gate mode. When the double-gate transistor works in the top-gate mode or the bottom-gate mode, the transistor is turned on; when it works in the double-gate mode, compared with the first two working modes, the output current, switch current ratio and carrier mobility significantly increased, the threshold voltage is significantly reduced, and the performance of the double-gate photosensitive organic transistor is more advantageous.

Description of drawings

FIG. 1 is a schematic structural diagram of a photosensitive organic field effect transistor with a double gate structure. In Figure 1: 1 is the top gate electrode, 2 is the top gate insulating layer, 3 is the organic semiconductor layer, 4 is the source electrode, 5 is the drain electrode, 6 is the bottom gate insulating layer, and 7 is the bottom gate electrode.

detailed description

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

In the present invention, light with a wavelength of 808nm is applied to the organic photosensitive transistor, and its output current in different modes is tested:

1) Transistor works in top gate mode

2) The transistor works in bottom gate mode

3) The transistor works in double gate mode

In the above different working modes, the performance of the device is the same in mode 1) and mode 2). In mode 3), when the same source-drain voltage as mode 1) and mode 2) is applied, the output current is mode 1), mode 2 ) more than twice; the analysis results show that the dual-gate working mode can effectively improve the mobility of the device.

Example 1

In this embodiment, a photosensitive organic field-effect transistor with a double gate structure is prepared according to the following steps:

1) The cleaned ITO conductive glass is used as the substrate of the device and the bottom gate electrode. The method of preparing the bottom gate electrode is magnetron sputtering, and the ITO ceramic target material In ₂ O ₃ : SnO ₂ =90:10wt. %, the purity is 99%, the working pressure of magnetron sputtering is 2.5 Pa, the vacuum degree is below 3.0×10 ^-3 Pascal, the sputtering power is 140 watts, the deposition rate is 5 angstroms/second, and the deposition time is 20 minutes .

2) The bottom gate insulating layer PVP is prepared by vacuum thermal evaporation, the vacuum thermal evaporation pressure is 1.5×10 ⁻³ Pa, and the deposition rate is 0.1 angstroms/second.

3) The source and drain electrodes are first prepared with a photolithography process to prepare a sacrificial layer, and a layer of negative glue is coated on the bottom gate insulating layer, and a mask is used to cover it. After exposure and hardening, a strong acid is used to remove the part covered by the mask. The exposed area is used to prepare the source electrode and the drain electrode; the method for preparing the source electrode and the drain electrode is vacuum thermal evaporation, the vacuum degree is below 1.5×10-3 Pascal, the evaporation rate is 1 angstrom/second, and the evaporation source Drain electrode Au;

4) The preparation method of the organic semiconductor layer is vacuum thermal evaporation, the vacuum degree is 3×10 ^-5 Pa, and the deposition rate is 0.5 angstroms/second;

5) The method of the top gate insulating layer is vacuum thermal evaporation, the pressure of vacuum thermal evaporation is 1.5×10 ^-3 Pa, and the deposition rate is 0.1 Angstroms/second;

6) The material of the top gate electrode is ITO conductive glass, and the method is magnetron sputtering. The working pressure of magnetron sputtering is 2.5Pa, the vacuum degree is below 3.0×10 ^-3 Pascal, the sputtering power is 140W, and the deposition rate is was 5 angstroms/sec, and the deposition time was 20 minutes.

Claims (10)

1. A photosensitive organic field-effect transistor with a double gate structure, characterized in that it comprises a top gate electrode (1), a top gate insulating layer (2), an organic semiconductor layer (3), a source electrode (4), and a drain electrode (5), bottom gate insulating layer (6), bottom gate electrode (7); Among them; applying the voltage of the top gate electrode or the bottom gate electrode can control the opening and closing of the transistor, and applying a voltage to the top gate electrode and the bottom gate electrode at the same time can increase the carrier mobility of the organic field effect transistor; the bottom gate The insulating layer is covered on the bottom gate electrode, the source electrode and the drain electrode are respectively covered on both sides of the bottom gate insulating layer, the middle part forms a channel, the organic semiconductor layer is covered on the channel and the source electrode, the drain electrode, and the top gate The insulating layer covers the organic semiconductor layer, and the top gate electrode covers the top gate insulating layer. 2. The photosensitive organic field-effect transistor with double gate structure according to claim 1, characterized in that, when irradiated with near-infrared light with a wavelength of 780-980nm, the output current increases significantly. 3 . The photosensitive organic field effect transistor with double gate structure according to claim 1 , wherein the transistor adopts a completely symmetrical structure. 4 . 4 . The photosensitive organic field-effect transistor with double gate structure according to claim 1 , wherein the material constituting the bottom gate electrode and the top gate electrode is ITO. 5 . The photosensitive organic field-effect transistor with double gate structure according to claim 1 , wherein the material constituting the bottom gate insulating layer and the top gate insulating layer is PVP. 6 . The photosensitive organic field effect transistor with double gate structure according to claim 1 , wherein the material constituting the source electrode and the drain electrode is gold. 7. The photosensitive organic field-effect transistor with double gate structure according to claim 1, characterized in that the material constituting the organic semiconductor layer is lead phthalocyanine. 8. A method for making a photosensitive organic field-effect transistor of double gate structure, is characterized in that, comprises the steps: 1) preparing a bottom gate electrode on the cleaned glass substrate; 2) preparing a bottom gate insulating layer on the bottom gate electrode obtained in step 1); 3) preparing a source electrode and a drain electrode on the substrate with a bottom gate insulating layer obtained in step 2); 4) preparing an organic semiconductor layer on the basis obtained in the step 3); 5) preparing a top gate insulating layer on the semiconductor layer obtained in step 4); 6) Prepare a top gate electrode on the top gate insulating layer obtained in step 5). 9. The method according to claim 8, characterized in that, in the step 3), first, a sacrificial layer is prepared by a photolithography process, and a layer of negative glue is coated on the bottom gate insulating layer, and a mask is used to block, After exposure and hardening, strong acid is used to remove the part covered by the mask, and the exposed area is used to prepare the source electrode and the drain electrode. 10. The method according to claim 8, characterized in that, in the step 1), the method for preparing the bottom gate electrode is magnetron sputtering, the working pressure is 2.5 Pascals, and the vacuum degree is 3.0×10 ^-3 Pascals Below, the sputtering power is 140 watts, the deposition rate is 5 Angstroms/second, and the deposition time is 20 minutes; In the step 2), the method of preparing the bottom gate insulating layer is vacuum thermal evaporation, the vacuum degree is below 1.5×10 ^-3 Pascal, and the evaporation rate is 0.1 angstroms/second; In the step 3), the method of preparing the source electrode and the drain electrode is vacuum thermal evaporation, the vacuum degree is below 1.5×10 ^-3 Pascal, and the evaporation rate is 1 angstrom/second; In the step 4), the method for preparing the organic semiconductor layer is vacuum thermal evaporation, the vacuum degree is below 3×10 ^-4 Pascal, and the evaporation rate is 0.5 angstroms/second; In the step 5), the method for preparing the top gate insulating layer is vacuum thermal evaporation, the vacuum degree is below 1.5×10 ^-3 Pascal, and the evaporation rate is 0.1 angstroms/second; In the step 6), the method for preparing the top gate electrode is magnetron sputtering, the working pressure is 2.5 Pascals, the degree of vacuum is below 3.0×10 ^-3 Pascals, the sputtering power is 140 watts, and the deposition rate is 5 Angstroms /sec, and the deposition time is 20 minutes.