An organic field-effect transistor

Abstract

The present invention relates to the field of organic semiconductor technology and discloses an organic field effect transistor, which includes a gate electrode, a source electrode, a drain electrode, a dielectric layer and an organic semiconductor layer; wherein, the organic semiconductor layer includes nanoparticles, the nanoparticles are uniformly and discontinuously distributed in the organic semiconductor layer, and the volume of the nanoparticles accounts for 0.1-3% of the volume of the organic semiconductor layer. In the present invention, a small amount of nanoparticles are introduced on the surface or inside of the organic semiconductor thin film of the organic semiconductor layer. The nanoparticles are uniform and discontinuous, and will not affect the electrical properties of the organic semiconductor thin film itself. The grain boundaries, dislocations, stacking faults and surfaces of the organic semiconductor thin film are pinned by the nanoparticles, resulting in an increase in the barrier for changes in the aggregated structure of the organic semiconductor thin film, thereby enhancing its aggregated stability, and further greatly increasing the maximum operating temperature and storage life of the organic field effect transistor.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of September 23, 2021, an application number of 202111110113.3, and an invention title of "A Method for Enhancing the Aggregation State Stability of Organic Semiconductor Films". Technical Field

[0002] The present invention relates to the field of organic semiconductor technology, and particularly to an organic field effect transistor. Background Art

[0003] Due to its inherent mechanical flexibility, organic semiconductor films have opened up a series of new application scenarios in the electronic field, such as flexible displays, sensors, radio frequency tags, and wearable electronic devices, etc., and are the core materials for the next generation of flexible electronic technologies. After more than thirty years of development, the mobility of organic field effect transistors prepared from organic semiconductor films has now exceeded that of amorphous silicon field effect transistors. However, commercial products based on organic field effect transistors have not been realized yet, and the main bottleneck problem lies in the poor stability of the aggregation state structure of organic semiconductor films. Under long-term storage and high-temperature conditions, the morphology of organic semiconductor films will undergo dewetting changes, resulting in an unstable aggregation state structure of the organic semiconductor films, and further leading to a decline or even complete failure of the electrical properties of organic field effect transistors. The main instability forms are manifested as a decrease in the on-state current, a drift in the threshold voltage, and a decrease in the mobility. Therefore, it is necessary to improve the stability of the aggregation state structure of organic semiconductor films to endow organic transistors with commercial potential.

[0004] The organic semiconductor films prepared by traditional methods such as vacuum thermal deposition or solution method are usually polycrystals, which themselves have a large number of defects such as grain boundaries, dislocations, and stacking faults. The organic molecules at the defect sites are arranged irregularly and have high energy, and are more likely to undergo morphological changes compared to the interior of a complete crystal, increasing additional residual stress in the film and directly affecting the stability of the aggregation state structure of the film. Organic semiconductor films are bound by weak van der Waals forces, and their binding force is weak. Compared with inorganic semiconductors bound by covalent bonds, it is easier to release the additional internal energy stored in the film under the drive of stress, thereby causing a change in the aggregation state structure of the film. Even at room temperature, the aggregation state structure of organic semiconductor films will change, showing intrinsic instability of the aggregation state structure. Therefore, it is necessary to explore the instability mechanism of the aggregation state structure of organic semiconductor films and then develop effective methods to enhance the stability of the aggregation state structure of organic semiconductor films for designing stable and commercially available organic field effect transistors. Currently, methods for improving the stability of semiconductor films include molecular design, encapsulation, low-temperature storage, increasing film thickness, etc. Although these methods slow down the morphological changes caused by aggregation state instability, they cannot effectively change the intrinsic instability characteristics of organic semiconductor films and cannot fundamentally solve the problem of failure of organic semiconductor devices. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an organic field-effect transistor. The present invention adopts a dispersion strengthening strategy. By suppressing the molecular diffusion at defects, the barrier for the change of the aggregated structure of the organic semiconductor thin film is increased, thereby improving the operating temperature and storage life of the electronic device constructed with the organic semiconductor thin film.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] The present invention provides an organic field-effect transistor, including a gate electrode, a source electrode, a drain electrode, a dielectric layer, and an organic semiconductor layer; wherein, the organic semiconductor layer includes nanoparticles, the nanoparticles are uniformly and discontinuously distributed in the organic semiconductor layer, and the volume of the nanoparticles accounts for 0.1%-3% of the volume of the organic semiconductor layer.

[0008] For the organic semiconductor layer, an organic semiconductor thin film is constructed on the surface of an insulating substrate, and then nanoparticles are introduced on the surface or inside the constructed organic semiconductor thin film. The nanoparticles are uniform and discontinuous, and the introduced nanoparticles are trace amounts. The volume fraction of the nanoparticles accounts for 0.1%-3% of the volume of the organic semiconductor thin film. The nanoparticles can be introduced on the surface of the organic semiconductor thin film or inside the organic semiconductor thin film. The specific doping upper limit depends on the volume fraction of different nanoparticles affecting the intrinsic electrical properties, as long as the electrical properties of the organic semiconductor itself are not affected.

[0009] The method for introducing nanoparticles is thermal evaporation. By heating the evaporation source, the nanoparticles reach the atomic-level gas state, and then re-nucleate on the surface of the sample with a certain rotation speed, with a size in the nanometer range, thereby realizing the introduction of nanoparticles. The aggregated structure of the organic semiconductor thin film itself is unstable. The nanoparticles introduced through this process are uniformly and discontinuously distributed on the surface or inside the organic semiconductor thin film, and will not aggregate by themselves, and will not affect the electrical properties of the organic semiconductor thin film itself. They are used to pin dislocations, grain boundaries, stacking faults, surfaces, etc. in the organic semiconductor thin film, thereby stabilizing the aggregated structure of the organic semiconductor thin film, so that the organic electronic device can withstand a higher operating temperature and be stored for a longer time.

[0010] Further, the rate of thermal evaporation is

[0011] Further, the rotation speed of the substrate during the thermal evaporation of nanoparticles is 5 revolutions per minute.

[0012] The gate further includes preparing a gate conductive electrode before constructing the organic semiconductor thin film. Any commercially available or reported substrate and insulating layer in the literature can be used. Preferably, a flexible or rigid substrate and insulating layer are used to prepare the gate conductive electrode, as long as the gate electrode is conductive. Commonly used Si++ / SiO 2 wafer is composed of heavily doped silicon (Si++) and SiO 2 insulating layer composite. This wafer itself has constructed an insulating layer and a gate, and it may not be necessary to prepare a gate, and it can directly serve as a substrate (the substrate only plays a role of supporting and carrying materials). It is also possible to select a substrate and re-prepare the gate electrode and the insulating layer.

[0013] For the source and drain electrodes, there are no requirements for the shapes of the source and drain electrodes and the distance between the two. The source and drain electrodes can be electrodes prepared by methods such as thermal evaporation, atomic layer deposition, electron beam evaporation, magnetron sputtering, electroplating, electrode transfer, etc. The electrode is a conductor, for example, it can be a metal electrode, and a conductive polymer or other conductors can also be used as electrodes.

[0014] Furthermore, the construction methods of the polycrystalline organic semiconductor thin film include but are not limited to thermal evaporation, atomic layer deposition, electron beam evaporation, magnetron sputtering, hydrogen arc plasma method, laser evaporation method, electroplating method, spin coating method, sol-gel method, dip coating method or drop casting method, etc.

[0015] Furthermore, the organic semiconductor layer is an organic semiconductor thin film, specifically a polycrystalline thin film, with a thickness between 1 nm and 1 μm, preferably a thickness of 5 nm to 200 nm.

[0016] Furthermore, the organic semiconductor layer is an organic small molecule semiconductor layer or an organic polymer semiconductor layer.

[0017] Furthermore, the organic semiconductor includes but is not limited to small molecule semiconductors: DNTT, DPA, PTCPI-CH 2 C 3 H 7 , pentacene, N1100, PTCDA, N1200;

[0018] The organic polymer semiconductor includes but is not limited to one of P3HT, N2200, and PBTTT-C14.

[0019] Furthermore, the nanoparticles are located on the surface or inside the organic semiconductor layer.

[0020] Furthermore, the diameter of the nanoparticles is between 0.01 nm and 100 nm, preferably about 1 - 10 nm, and its thermal stability is better than that of the organic semiconductor thin film.

[0021] Further, the nanoparticles include one of metal conductor particles, organic and inorganic semiconductor particles, or insulator particles. The introduction method of the nanoparticles includes, but is not limited to, thermal evaporation deposition. The nanoparticles include, but are not limited to, metal conductor particles such as Au, Ag, Al, Cu, Cr, etc.; semiconductor particles C 60 ; insulator particles MoO 3 、WO 3 、Al 2 O 3 。

[0022] The present invention also provides an electronic device comprising the above-mentioned organic field effect transistor.

[0023] The organic field effect transistor of the present invention is suitable for enhancing the stability of the aggregated state structure of all devices prepared using an organic semiconductor layer, including but not limited to organic thin film transistors, organic heterojunction transistors, organic field effect transistors, organic light emitting diodes, organic solar cells, etc.

[0024] The present invention discloses the following technical effects:

[0025] The obtained DNTT field effect transistor of the present invention has a higher operating temperature and a longer service life compared to the untreated DNTT field effect transistor, specifically: it can be heated at 210 °C for 30 minutes, 240 °C for 5 minutes, and can continuously operate for 17 days in an environment of 150 °C. According to the accelerated aging tests at different temperatures, an Arrhenius life prediction model for the aging law of organic field effect transistors is proposed, and the theoretical life at room temperature can reach millions of years, far exceeding the reported results, ensuring the stability of the performance of organic field effect transistors under high temperature conditions or after being placed for several years.

[0026] By introducing nanoparticles on the surface or inside of the organic semiconductor thin film in the organic field effect transistor of the present invention, the grain boundaries, dislocations, stacking faults, surfaces, etc. of the organic semiconductor thin film are pinned, so that the aggregated state structure is stabilized by the nanoparticles, and the barrier for the change of the aggregated state structure increases, suppressing the instability of the intrinsic aggregated state structure of the organic semiconductor from the source, thereby greatly increasing the operating temperature and storage life of organic electronic devices. Currently, the existing methods can only slow down the instability of the aggregated state structure of the organic semiconductor, while the organic semiconductor thin film with nanoparticles introduced in the present invention has improved stability of the aggregated state structure compared to the organic semiconductor thin film without nanoparticles introduced, specifically manifested as: (1) the tolerable operating temperatures of different semiconductors are increased by 20 °C to 120 °C; (2) the morphology and electrical properties of the organic semiconductor thin film device with nanoparticles introduced have no obvious change after being stored at room temperature for 6 years. It ensures the stability of the electrical properties of organic electronic devices prepared with organic semiconductor thin films under high temperature and actual environments. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 Schematic diagram of the aggregated state structure stability of the nanoparticle-enhanced organic semiconductor layer of the present invention;

[0029] Figure 2 Schematic diagram of the organic field effect transistor structure, where (a) bottom gate top contact organic field effect transistor, (b) bottom gate bottom contact organic field effect transistor, (c) top gate top contact organic field effect transistor, (d) top gate bottom contact organic field effect transistor;

[0030] Figure 3 Morphology diagrams of the organic semiconductor thin film before and after annealing, where (a) DNTT thin film at room temperature, (b) DNTT thin film after annealing at 210 °C for 30 minutes, (c) DNTT thin film doped with Au nanoparticles at room temperature, (d) DNTT thin film doped with Au nanoparticles after annealing at 210 °C for 30 minutes, (e) bulk-doped Au nanoparticle DNTT thin film at room temperature, (f) bulk-doped Au nanoparticle DNTT thin film after annealing at 210 °C for 30 minutes, and the scale bar is 2 μm;

[0031] Figure 4 Normalized mobility comparison diagram of Au-DNTT with different doping volume fractions at different temperatures;

[0032] Figure 5 Mobility change diagram of the organic semiconductor field effect transistor prepared from the pure DNTT thin film and the organic semiconductor field effect transistor prepared from the thin film of Example 1 when placed at room temperature for different times;

[0033] Figure 6 Morphology diagrams of the P3HT thin film before and after annealing, where (a) P3HT thin film at room temperature, (b) P3HT thin film after annealing at 300 °C for 1 hour, (c) P3HT thin film doped with Au nanoparticles at room temperature, (d) P3HT thin film doped with Au nanoparticles after annealing at 300 °C for 1 hour, and the scale bar is 15 μm;

[0034] Figure 7Morphology diagrams of the organic semiconductor thin film before and after annealing, where (a) is the DNTT thin film at room temperature, (b) is the DNTT thin film annealed at 210 °C for 30 minutes, (c) is the bulk-doped Au nanoparticle DNTT thin film at room temperature, (d) is the state of the bulk-doped Au nanoparticle DNTT thin film after annealing at 210 °C for 30 minutes, and the scale bar is 15 μm;

[0035] Figure 8 Statistical comparison chart of the thermal stability temperatures of the pure phase films and Au nanoparticle-enhanced dispersion films of different semiconductors;

[0036] Figure 9 Morphology diagrams of the DNTT organic semiconductor thin film doped with different nanoparticles before and after annealing, where (a) is the state at room temperature, (b) is the state after annealing at 220 °C for 30 minutes, and the scale bar is 15 μm;

[0037] Figure 10 Transmission electron microscope images of the DNTT organic semiconductor thin film doped with different volume fractions of nanoparticles, where (a) the volume fraction is 0.1%, the scale bar is 20 nm; (b) the volume fraction is 0.5%, the scale bar is 20 nm; (c) the volume fraction is 1.5%, the scale bar is 20 nm; (d) the volume fraction is 3%, the scale bar is 20 nm. Detailed implementation manners

[0038] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0039] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0040] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0041] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the specification of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the specification of the present invention will be apparent to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0042] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0043] The sources of the drugs in the following examples are as follows:

[0044] Organic semiconductor molecule: DNTT

[0045]

[0046] Purity: 99%,

[0047] Source: Shanghai Daran Chemical Co., Ltd.;

[0048] DPA (2,6-diphenylanthracene):

[0049]

[0050] Purity: 99%,

[0051] Source: Shanghai Daran Chemical Co., Ltd.;

[0052] PTCDA:

[0053]

[0054] Purity: 99%

[0055] Source: Shanghai Daran Chemical Co., Ltd.

[0056] PTCPI-CH 2 C 3 H 7 :

[0057]

[0058] Purity: 99%,

[0059] Source: Shanghai Daran Chemical Co., Ltd.

[0060] Pentacene:

[0061]

[0062] Purity: 99%, Source: Shanghai Daran Chemical Co., Ltd.

[0063] N1100:

[0064]

[0065] Purity: 99%.

[0066] N1200:

[0067]

[0068] Polymer semiconductor:

[0069] Poly(3-hexylthiophene-2,5-diyl) (P3HT)

[0070]

[0071] Average molecular weight: 40,000 - 100,000, Source: Sigma-Aldrich (Shanghai) Trading Co., Ltd.

[0072] N2200:

[0073] Average molecular weight ≥ 30,000.

[0074] PBTTT-C14:

[0075] Average molecular weight > 20000.

[0076] Nanoparticles:

[0077] Metal:

[0078] Gold (Au), Purity: 99.999%;

[0079] Silver (Ag), Purity: 99.999%;

[0080] Aluminum (Al), Purity: 99.999%;

[0081] Chromium (Cr), Purity: 99.99%.

[0082] Semiconductor:

[0083] Fullerene (C 60 ), Purity: 99%, Source: Shanghai Darun Chemical Co., Ltd.;

[0084] Insulator:

[0085] Molybdenum trioxide (MoO 3 ), Purity: 99.998%, Source: Alfa Aesar (China) Chemical Co., Ltd.;

[0086] The schematic diagram of the aggregation state structure stability of the organic semiconductor layer enhanced by the nanoparticles of the present invention is shown in Figure 1 .

[0087] Taking the organic semiconductor thin film with introduced nanoparticles prepared into an organic field effect transistor as an example in the embodiment of the present invention, the stability of the electrical properties of the transistor is quantitatively characterized. For other electronic devices such as OLEDs that are prepared from the organic semiconductor thin film with introduced nanoparticles as long as they include an organic semiconductor layer, the working temperature or storage life can be improved.

[0088] Example 1

[0089] (1) A silicon wafer containing 300 nm of silicon dioxide and 500 μm of heavily doped silicon, with a size of 1 cm × 1 cm, is selected. Using 500 μm of heavily doped silicon as the gate, octadecyltrichlorosilane (OTS) is modified on the 300 nm of silicon dioxide by the vacuum vapor phase method at 120 °C for 1 hour to obtain a silicon dioxide insulating layer modified with OTS;

[0090] (2) The metal source and drain electrodes are evaporated on the surface of the silicon dioxide insulating layer modified with OTS by the thermal evaporation method, and the evaporation rate is with a thickness of 20 nm;

[0091] (3) A 20 nm thick DNTT thin film is thermally evaporated on the insulating layer with source and drain electrodes, and the evaporation rate is

[0092]

[0093] (4) Au nanoparticles are thermally evaporated on the surface of the DNTT thin film, and thermally evaporated for 60 seconds at a evaporation rate, and 1.5% by volume of Au is doped in the DNTT thin film. During the process of introducing nanoparticles, the substrate plate needs to rotate at a rotation rate of 5 revolutions per minute to obtain a bottom-gate bottom-contact organic field effect transistor (Au-DNTT organic field effect transistor, Figure 2 b) in).

[0094] Example 2

[0095] (1) A silicon wafer containing 300 nm of silicon dioxide and 500 μm of heavily doped silicon, with a size of 1 cm × 1 cm, is selected. Using 500 μm of heavily doped silicon as the gate, octadecyltrichlorosilane (OTS) is modified on the 300 nm of silicon dioxide by the vacuum vapor phase method at 120 °C for 1 hour to obtain a silicon dioxide insulating layer modified with OTS;

[0096] (2) The metal source and drain electrodes are evaporated on the surface of the silicon dioxide insulating layer modified with OTS by the thermal evaporation method, and the evaporation rate is with a thickness of 20 nm; A 30 nm thick DNTT thin film is thermally evaporated on the substrate, and at the same time The evaporation rate of thermal evaporation is 120 seconds. When doping 2% volume fraction of Au into the DNTT film and introducing nanoparticles, rotate the substrate holder at a rotation rate of 5 revolutions per minute to uniformly incorporate Au nanoparticles into the bulk of the film;

[0097] (3) Thermally evaporate the source and drain electrodes on the surface of the DNTT film. The evaporation rate is The electrode thickness is 30 nm to obtain an organic field-effect transistor.

[0098] To verify the stability of the morphology of the organic semiconductor film, use an atomic force microscope to observe the morphology of the organic field-effect transistor of doped gold nanoparticles DNTT (Au-DNTT) before and after annealing at 210 °C for 30 minutes ( Figure 3 in c, d). After fabricating the transistor, the channel part, i.e., the organic film part, was found to have no obvious change in its morphology under the condition of annealing at 210 °C for 30 minutes, indicating that the aggregated state structure of the organic film can withstand higher temperatures. Further, the electrical properties of the Au-DNTT organic field-effect transistor were tested. The highest working temperature of the Au-DNTT organic field-effect transistor prepared by doping Au nanoparticles with different volume fractions was judged by testing its mobility at different temperatures ( Figure 4 ). The test results show that the performance of the organic semiconductor device without introducing nanoparticles gradually decreases with the increase of the test temperature, while Au-DNTT with different volume fractions has the characteristic of high-temperature stability and has stable electrical properties under high-temperature conditions below 210 °C, broadening the working temperature range of the organic transistor. The devices with introduced nanoparticles and the devices without introduced nanoparticles were tracked and tested for up to 6 years. The failure degree was quantitatively characterized by testing the electrical properties. The results show that the performance of the organic semiconductor field-effect transistor without introducing nanoparticles gradually decreases at room temperature and almost completely fails after 6 years, while the electrical properties of the organic semiconductor field-effect transistor with introduced nanoparticles remain stable after being stored at room temperature for 6 years ( Figure 5 ), which means that under room-temperature storage conditions, the morphology of the organic semiconductor film with introduced nanoparticles is difficult to change, ensuring the stability of the electrical properties of the organic field-effect transistor device prepared with the organic semiconductor film at high temperatures and in practical environments.

[0099] Nanoparticles can not only be introduced onto the surface of the organic semiconductor film but also into its bulk phase, and can also play a stabilizing role. Specifically, refer to Example 3. The preparation methods of nanoparticles and the organic semiconductor film include but are not limited to thermal evaporation method, atomic layer deposition method, electron beam evaporation method, magnetron sputtering method, hydrogen arc plasma method, laser evaporation method, electroplating method, spin coating method, sol-gel method, dip coating method or drop casting method, etc.

[0100] Example 3

[0101] (1) Select a silicon wafer containing 300 nm silicon dioxide and 500 μm heavily doped silicon, with a size of 1 cm × 1 cm. Use 500 μm heavily doped silicon as the gate, and modify octadecyltrichlorosilane (OTS) on 300 nm silicon dioxide by vacuum vapor deposition method at 120 °C for 1 hour to obtain a silicon dioxide insulating layer modified with OTS;

[0102] (2) Evaporate metal source and drain electrodes on the surface of the silicon dioxide insulating layer modified with OTS by thermal evaporation method, with an evaporation rate of a thickness of 20 nm; thermally evaporate a 30 nm DNTT thin film on the substrate, and simultaneously thermally evaporate for 60 seconds at a evaporation rate to dope 1.5% by volume of Au in the DNTT thin film. When introducing nanoparticles, it is necessary to rotate the substrate disk at a rotation rate of 5 revolutions per minute to uniformly incorporate Au nanoparticles into the bulk of the thin film;

[0103] (3) Thermally evaporate metal source and drain electrodes on the surface of the DNTT thin film, with an evaporation rate of the electrode thickness is 30 nm to obtain an organic field effect transistor.

[0104] In order to verify the stability of the morphology of the semiconductor thin film obtained by doping Au nanoparticles into the bulk of DNTT, the morphology of the organic field effect transistor of DNTT doped with gold nanoparticles in the bulk (bulk Au-DNTT) prepared in this example before and after annealing at 210 °C for 30 minutes was observed ( Figure 7 c, d in), and it was found that its morphology did not change significantly under the condition of annealing at 210 °C for 30 min, indicating that its morphology can withstand higher temperatures. The comparative example is Example 5 ( Figure 3 a, b in).

[0105] In order to verify the stability of the morphology of the organic semiconductor thin film, the local morphology of the DNTT organic field effect transistor before and after annealing at 210 °C for 30 minutes was observed by atomic force microscope ( Figure 3 e, f in), and it was found that its morphology changed significantly under the condition of annealing at 210 °C for 30 minutes, and the continuity of the semiconductor thin film decreased at high temperatures. In addition, the morphology of the annealed thin film was further characterized by a 3D confocal microscope, and it was found that compared with the continuous and uniform morphology of the thin film before and after annealing ( Figure 7 c, d in), the aggregated state structure was very stable, and the semiconductor thin film with stable introduced nanoparticles had good thermal stability.

[0106] The organic field effect transistor of the present invention is not only applicable to organic small molecule semiconductor thin films, but also applicable to organic polymer semiconductor thin films, and it has a significant effect of enhancing the stability of the aggregated state structure.

[0107] Example 4

[0108] (1) A silicon wafer containing 300 nm of silicon dioxide and 500 μm of heavily doped silicon with a size of 1 cm × 1 cm was selected. Using 500 μm of heavily doped silicon as the gate, octadecyltrichlorosilane (OTS) was modified on 300 nm of silicon dioxide by vacuum vapor deposition at 120 °C for 1 hour to obtain a silicon dioxide insulating layer modified with OTS;

[0109] (2) Metal source and drain electrodes were evaporated on the surface of the silicon dioxide insulating layer modified with OTS by thermal evaporation, and the evaporation rate was with a thickness of 20 nm;

[0110] (3) A P3HT thin film was spin-coated on the substrate containing source and drain electrodes. The concentration of P3HT was 8 mg / mL, and toluene was used as the solvent; 30 μL was dropped on SiO 2 and spun at 3000 revolutions per second for 50 seconds, and then heated at 100 °C for 5 minutes to volatilize the excess solvent to obtain a P3HT polymer thin film;

[0111] (4) On the surface of the P3HT thin film, DNTT thin film was thermally evaporated at a rate of for 60 seconds, and 1.5% by volume of Au was doped in the DNTT thin film. When introducing nanoparticles, the substrate disk needs to be rotated at a rotation rate of 5 revolutions per minute to obtain a bottom-gate bottom-contact organic field-effect transistor.

[0112] To verify the stability of the morphology of the P3HT polymer semiconductor, the morphology of the organic field-effect transistor of P3HT doped with gold nanoparticles (Au-P3HT) before and after annealing at 300 °C for 1 hour was observed using a 3D confocal microscope ( Figure 6 c, d in), and it was found that there was no obvious change in its morphology after annealing at 300 °C for 1 hour, indicating that its morphology can withstand higher temperatures.

[0113] To prove that the method of the present invention has excellent effects, Examples 5 and 6 were set as comparisons, and the specific implementation methods are as follows:

[0114] Example 5

[0115] (1) A silicon wafer containing 300 nm of silicon dioxide and 500 μm of heavily doped silicon with a size of 1 cm × 1 cm was selected. Using 500 μm of heavily doped silicon as the gate, octadecyltrichlorosilane (OTS) was modified on 300 nm of silicon dioxide by vacuum vapor deposition at 120 °C for 1 hour to obtain a silicon dioxide insulating layer modified with OTS;

[0116] (2) Metal source and drain electrodes were evaporated on the surface of the silicon dioxide insulating layer modified with OTS by thermal evaporation, and the evaporation rate was with a thickness of 20 nm;

[0117] (3) Thermally evaporate a 30-nm DNTT thin film on the insulating layer containing source and drain electrodes, with an evaporation rate of

[0118] To verify the stability of the morphology of the organic semiconductor, the local morphology of the DNTT organic field-effect transistor before and after annealing at 210 °C for 30 minutes was observed using an atomic force microscope ( Figure 3 as shown in a, b)), and it was found that the morphology changed significantly after annealing at 210 °C for 30 minutes, and the continuity of the semiconductor thin film decreased under high-temperature conditions. In addition, the morphology of the annealed thin film was further characterized using a 3D confocal microscope, and it was found that compared with the continuous and uniform morphology of the thin film before annealing ( Figure 7 a)), the entire thin film was no longer continuous ( Figure 7 b)), and the aggregated structure became unstable. Further tests were conducted on the electrical properties of the DNTT organic field-effect transistor. By testing its transfer curves at different temperatures to determine its maximum operating temperature and testing its lifetime at an annealing temperature of 150 °C to characterize its high-temperature lifetime, it was found that the transfer curves under both test conditions showed unstable electrical properties under high-temperature conditions. From the comparison of the threshold voltage drift value and the change ratio of the on / off ratio between Example 4 and Example 1, it can be seen that Example 4 specifically showed a drift in the threshold voltage and a decrease in the on / off ratio, while Example 1 showed a stable threshold voltage and on / off ratio. Figure 4 The normalized mobility comparison chart of Example 1 and Example 4 is given, and it can be found that the mobility of the semiconductor thin film stabilized by introducing nanoparticles (Example 1) is very stable, while the mobility of Example 4 is decreasing.

[0119] Example 6

[0120] (1) Select a silicon wafer containing 300 nm of silicon dioxide and 500 μm of heavily doped silicon, with a size of 1 cm × 1 cm. Using the 500-μm heavily doped silicon as the gate, modify octadecyltrichlorosilane (OTS) on the 300-nm silicon dioxide by vacuum vapor deposition at 120 °C for 1 hour to obtain a silicon dioxide insulating layer modified with OTS;

[0121] (2) Evaporate metal source and drain electrodes on the surface of the silicon dioxide insulating layer modified with OTS by thermal evaporation, with an evaporation rate of and a thickness of 20 nm;

[0122] (3) Spin-coat a P3HT thin film on the substrate containing source and drain electrodes, with a P3HT concentration of 8 mg / mL and toluene as the solvent; drop 30 μL on SiO 2 and spin at 3000 revolutions per second for 50 seconds, then heat at 100 °C for 5 minutes to volatilize the excess solvent to obtain a bottom-gate bottom-contact P3HT polymer thin film organic field-effect transistor.

[0123] To verify the stability of the morphology of the P3HT polymer semiconductor, a 3D confocal microscope was used to observe the morphology of an organic field-effect transistor doped with gold nanoparticles (Au-P3HT) before and after annealing at 300 °C for 1 hour ( Figure 6 as shown in a, b in

[0124] ). It was found that under the condition of annealing at 300 °C for 1 hour, dewetting occurred in the organic semiconductor thin film, specifically manifested as the film becoming non-uniform, the substrate coverage decreasing, and the continuity decreasing, indicating that its morphology is prone to change at high temperatures. Examples 1-4 are the organic semiconductor thin films with high working temperature and long lifespan and the corresponding organic field-effect transistors of the present invention, and Examples 5 and 6 are used for comparison with the organic field-effect transistors with high working temperature and long lifespan of the present invention. In Examples 1-4, by introducing nanoparticles, the morphology and electrical properties of the organic field-effect transistors are maintained stable under high-temperature conditions and continuous thermal stress conditions; the electrical properties of the organic field-effect transistors in Examples 5 and 6 show thermal instability in terms of morphology under high-temperature and continuous thermal stress conditions.

[0125] The Au nanoparticles in the DNTT thin film were replaced with other dispersed-phase nanoparticles (Ag, Al, Cr, C60, MoO 3 ) to verify the universality of the dispersed-phase particles. Ag NP-DNTT thin film, Al NP-DNTT thin film, CrNP-DNTT thin film, C60 NP-DNTT thin film, and MoO 3 NP-DNTT thin film were respectively prepared, and the pure DNTT thin film was used as a comparison. The statistical chart of the thermal stability temperature comparison between the pure-phase films of different semiconductors and the dispersed films enhanced with Au nanoparticles is shown in Figure 8 . The morphological changes of the thin films before and after annealing at 220 °C were observed by a 3D confocal microscope ( Figure 9 a, b), Figure 9 where a is the morphological diagram at room temperature before annealing. It can be found that the thin films are all uniform and continuous. Figure 9 b is the morphological diagram after annealing at 220 °C. It was found that the pure DNTT thin film of the comparison sample was no longer continuous, while the continuity of the other dispersed films was better than that of the pure DNTT thin film, proving that the replacement with other dispersed particles is still applicable.

[0126] According to the same method as in Example 1, different fractions of Au nanoparticles were doped. The transmission electron microscope images of the DNTT organic semiconductor thin film doped with different volume fractions of nanoparticles are shown in Figure 10 , where (a) the volume fraction is 0.1%, the scale bar is 20 nm; (b) the volume fraction is 0.5%, the scale bar is 20 nm; (c) the volume fraction is 1.5%, the scale bar is 20 nm; (d) the volume fraction is 3%, the scale bar is 20 nm. Figure 10It can be seen that different volume fractions will cause slightly different diameters of the nanoparticles, but they are all in the nanometer range, uniform and discontinuous, and the action effects have no obvious difference. When the volume fraction of the nanoparticles is not less than 3%, the nanoparticles will attract each other due to interaction, resulting in clustering, and the uniformity will decrease to a certain extent. Therefore, by controlling the volume fraction, the uniformity of the nanoparticles in the organic film can be improved, and it is also ensured that the nanoparticles will not affect the electrical properties of the organic semiconductor film itself.

[0127] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An organic field-effect transistor, characterized in that, it includes a gate, a source, a drain, a dielectric layer, and an organic semiconductor layer; wherein, the organic semiconductor layer includes nanoparticles, the nanoparticles are evenly distributed and discontinuous in the organic semiconductor layer, and the volume of the nanoparticles accounts for 0.1-3% of the volume of the organic semiconductor layer; the organic semiconductor layer is an organic semiconductor thin film, specifically a polycrystalline thin film; the diameter of the nanoparticles is 0.01 nm - 100 nm, and its thermal stability is better than that of the organic semiconductor thin film.

2. The organic field-effect transistor according to claim 1, characterized in that, the organic semiconductor layer is an organic small molecule semiconductor layer or an organic polymer semiconductor layer.

3. The organic field-effect transistor according to claim 1, characterized in that, the nanoparticles are located on the surface or inside the organic semiconductor layer.

4. The organic field-effect transistor according to claim 1, characterized in that, the nanoparticles include one of metal conductor particles, organic and inorganic semiconductor particles, or insulator particles.

5. An electronic device, characterized in that, it includes the organic field-effect transistor according to any one of claims 1-4.

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