Two-dimensional organic thin film doped with organic salt, transistor and preparation method of two-dimensional organic thin film

Abstract

The invention discloses a two-dimensional organic thin film doped with organic salt, a transistor and a preparation method of the two-dimensional organic thin film. The two-dimensional organic thin film doped with the organic salt comprises an organic semiconductor thin film and a doped thin film, wherein the doped thin film is arranged on the organic semiconductor thin film; the organic semiconductor material is a conjugated organic small molecule with an alkyl side chain, and the dopant material is an organic salt. The transistor comprises a substrate, an insulating layer, a two-dimensional organic film doped with organic salt and a source / drain electrode. The organic salt liquid phase doped two-dimensional organic thin film transistor prepared by the invention is doped on the basis of an organic small molecule material with intrinsic high mobility, so that a precondition is provided for preparing a high-performance doped organic thin film transistor; according to the preparation method, the source / drain metal is prepared through the transfer electrode method, damage to the ultrathin organic semiconductor film caused by metal ion bombardment in the traditional metal evaporation process is avoided, and the high performance of the transistor is guaranteed.

Description

Technical Field

[0001] The present invention relates to semiconductors, and particularly to a two-dimensional organic thin film doped with an organic salt, a transistor and a preparation method thereof. Background Art

[0002] Due to their excellent mobility and current driving ability, solution-processed small molecule organic thin film transistors are becoming key components for flexible electronics and the Internet of Things.

[0003] However, there are grain boundaries in the organic conjugated small molecule semiconductor thin film, which will introduce structural defects. These defects will seriously hinder the charge transport and reduce the uniformity between devices. It is necessary to develop effective passivation strategies to suppress the influence of grain boundaries on device performance. Summary of the Invention

[0004] Object of the Invention: The first object of the present invention is to provide a two-dimensional organic thin film doped with an organic salt with significantly improved performance; the second object of the present invention is to provide a transistor including the two-dimensional organic thin film doped with the organic salt; the third object of the present invention is to provide a preparation method for the two-dimensional organic thin film doped with the organic salt and the transistor.

[0005] Technical Solution: The two-dimensional organic thin film doped with an organic salt according to the present invention includes an organic semiconductor thin film and a doped thin film, and the doped thin film is on the organic semiconductor thin film; the organic semiconductor material is a conjugated organic small molecule with an alkyl side chain, and the dopant material is an organic salt.

[0006] Preferably, the conjugated organic small molecule includes 2,9-didecyl dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene, 2,9-dihexyl naphtho[2,3-b]naphtho[2',3':4,5]thieno[3,2-d]dithiophene or 2,9-ditetradecyl naphtho[2,3-b]naphtho[2',3':4,5]thieno[3,2-d]dithiophene. The conjugated organic small molecule with an alkyl side chain has good solubility in many organic solvents.

[0007] Preferably, the dopant material is triphenylcarbenium tetrakis(pentafluorophenyl)borate (hereinafter referred to as TrTPFB). Doping with an organic salt circumvents the limitations of the electron affinity and ionization energy matching, which is beneficial to improving the doping efficiency and the universality of the doping method.

[0008] The two-dimensional organic thin film transistor doped with an organic salt according to the present invention includes a substrate, an insulating layer, a two-dimensional organic thin film doped with an organic salt and source / drain electrodes; the insulating layer is an oxide.

[0009] Preferably, the substrate is silicon.

[0010] Preferably, the insulating layer is hafnium oxide, aluminum oxide or zirconium oxide. The oxide obtained by atomic layer deposition is very beneficial to the growth of the organic semiconductor thin film due to its extremely low surface roughness and good wettability.

[0011] The method for preparing the two-dimensional organic thin film doped with an organic salt according to the present invention includes the following steps:

[0012] (1) Growing an oxide on a substrate as an insulating layer;

[0013] (2) Growing a two-dimensional organic semiconductor thin film on the surface of the oxide as a semiconductor channel layer;

[0014] (3) Preparing a doped thin film on the organic semiconductor thin film to obtain a two-dimensional organic thin film doped with an organic salt;

[0015] Preferably, in step (1), the oxide is grown by atomic layer deposition, and the thickness of the oxide is 20 - 30 nm.

[0016] Preferably, in step (1), the method for growing the insulating layer is: placing a silicon substrate in an atomic layer deposition chamber, evacuating, raising the temperature of the chamber, and then introducing a metal source and an oxidation source to in-situ deposit a uniform oxide thin film on the surface of the substrate.

[0017] Preferably, in step (2), the two-dimensional organic semiconductor thin film is grown by a solution shearing method. The prepared organic semiconductor solution is injected into the gap between the substrate and the upper plate, and the upper plate is controlled to continuously move in one direction to obtain a large-area two-dimensional organic semiconductor thin film. The thickness of the organic semiconductor thin film is 3.5 - 3.7 nm.

[0018] Preferably, in step (2), the solvent of the solution for growing the two-dimensional organic semiconductor thin film is at least one of toluene, chlorobenzene, and 1,2,3,4-tetrahydronaphthalene. An organic small molecule powder is added to the solvent to prepare an organic semiconductor solution. The concentration of the organic semiconductor solution is 0.5 - 0.7 mg / mL. The organic small molecules can precipitate quickly and form an ordered arrangement under this saturated solution to obtain a single crystal thin film with consistent orientation. Preferably, the organic semiconductor solution is continuously heated at 80 - 85 °C to ensure that the organic molecules are fully dissolved and do not degrade quickly.

[0019] Preferably, in step (2), the two-dimensional organic semiconductor single crystal film is grown by the semi-circular solution shearing method. The distance between the substrate and the upper plate is set to 80-100 μm, and the inclination angle of the upper plate is 10-15°. The appropriate distance and angle facilitate the evaporation of the solvent at the solution meniscus, thereby forming a film of organic small molecule semiconductors. The growth temperature is 64-68 °C. The growth solution is injected into the gap between the metal substrate and the upper plate. At the corresponding temperature, the upper plate is controlled to continuously move in one direction at a speed of 2.5-3.5 μm / s, which is conducive to the formation of an ultrathin and uniform monolayer film of organic small molecules in the evaporation zone, completing the growth of the organic semiconductor film.

[0020] Preferably, in step (3), the organic salt powder is added to an organic solvent to prepare a dopant solution, and the doped film is prepared by the solution method. Preferably, the preparation method is selected from one of dip coating, spin coating or miscible method. Preferably, the solvent of the solution for preparing the doped film is at least one of hexane, chloroform, dichloromethane, and acetonitrile. Selecting a solvent that has little damage to the organic semiconductor layer as the solvent of the dopant is conducive to realizing a high-performance doped organic thin film transistor. The organic salt powder is added to the solvent to prepare a dopant solution, and the mass percentage concentration of the dopant solution is 0.1-0.5 wt%. An appropriate dopant concentration can achieve efficient doping and excellent transistor performance. An excessively high dopant concentration will damage the crystallinity and uniformity of the ultrathin organic semiconductor, thereby reducing the performance of the doped organic thin film transistor.

[0021] The preparation method of the doped organic salt two-dimensional organic thin film transistor of the present invention includes the following steps:

[0022] (1) Grow an oxide on the substrate as an insulating layer;

[0023] (2) Grow a two-dimensional organic semiconductor film on the surface of the oxide as a semiconductor channel layer;

[0024] (3) Prepare a doped film on the organic semiconductor film;

[0025] (4) Another substrate is taken to prepare source / drain electrodes, and the source / drain electrodes are transferred onto the doped film to obtain the doped two-dimensional organic thin film transistor.

[0026] Preferably, the source / drain electrodes in step (4) are silver, aluminum, palladium, gold or platinum. By selecting appropriate source / drain electrodes, the prepared two-dimensional organic thin film transistor with a liquid-phase doped organic salt can achieve excellent metal-semiconductor ohmic contact and realize a high-performance doped organic thin film transistor.

[0027] Preferably, in the step (4), the source / drain electrode transfer method is the van der Waals transfer method. By using this method to transfer the electrodes onto the doped thin film, the thin film will not be damaged, and the ultra-thin organic semiconductor thin film and the doped thin film can be protected from the impact or thermal damage caused by high-energy metal particles during the metal deposition process.

[0028] Preferably, in the step (4), the source / drain electrode patterning method uses electron beam lithography, and the metal preparation method uses electron beam evaporation.

[0029] Principle of the invention: Organic salt doping is a superior alternative to traditional charge transfer methods because it circumvents the limitations of electron affinity and ionization energy matching. Secondly, a two-dimensional organic semiconductor thin film can be used as the channel layer of the transistor. Due to its highly ordered arrangement, extremely low defect concentration, and negligible interlayer screening effect, the ultra-thin two-dimensional organic semiconductor thin film can directly detect the charge transport behavior in grain boundaries; and in the monolayer limit, the electrophilic or nucleophilic attack of organic salts on the organic semiconductor thin film becomes more sensitive, thus promoting more effective doping and having great potential for repairing grain boundary effects through doping. Therefore, eliminating the adverse effects brought by grain boundary effects through the single-layer semiconductor thin film structure and organic salt doping is of great significance for restoring the quasi-band transport characteristics in organic thin film transistors and improving the electrical characteristics such as current, mobility, and threshold voltage of organic thin film transistors. In the two-dimensional organic thin film transistor with liquid-phase doped organic salts of the present invention, an oxide with low surface roughness is used as the growth substrate, and the organic solvent has good wettability on the oxide, providing good prerequisites for preparing high-quality thin films; combined with the good solubility and self-assembly behavior of organic conjugated small molecules containing alkyl chains such as 2,9-didecyl dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene in organic solvents, a large-area two-dimensional organic semiconductor thin film is prepared; the performance of the doped two-dimensional organic thin film transistor is significantly improved by liquid-phase doping of organic salts such as triphenylcarbenium tetrakis(pentafluorophenyl)borate that break through the limitations of electron affinity and ionization energy matching.

[0030] Advantages: Compared with the prior art, the present invention has the following remarkable advantages: (1) The method of liquid-phase doping of organic salts is based on two-dimensional organic semiconductor thin films, providing a feasible idea for significantly improving the performance of two-dimensional organic semiconductor thin film devices; (2) The two-dimensional organic thin film transistor doped with liquid-phase organic salts is doped based on organic small molecule materials with intrinsic high mobility, and its performance has been significantly improved. The current and mobility of two-dimensional single-crystal and polycrystalline organic thin film transistors have increased by about 26% and 11% respectively at room temperature, and the threshold voltages of single-crystal / polycrystalline organic thin film transistors after doping have shifted from -0.08 / -0.24 V before doping to 0.36 / 0.21 V in the positive voltage direction; in addition, the charge transport of single-crystal organic thin film transistors maintains a strip-like transport characteristic before and after doping, while the charge transport of polycrystalline organic thin film transistors changes from multiple trap capture and release transport before doping to strip-like transport after doping, demonstrating that the two-dimensional organic thin film transistor doped with liquid-phase organic salts can eliminate the adverse effects brought by grain boundary effects through doping and improve the electrical properties of two-dimensional organic thin film transistors; (3) The two-dimensional organic thin film transistor doped with liquid-phase organic salts combines highly efficient and universal liquid-phase organic salt doping, which can simplify the device preparation process, reduce the preparation cost, expand the application fields, and has great potential for realizing large-area organic circuits or organic integrated applications; (4) The preparation method prepares the source / drain metal by the transfer electrode method, avoiding the damage to the ultra-thin organic semiconductor thin film caused by metal ion bombardment during the traditional metal evaporation process, and ensuring the high performance of the transistor. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the molecular structure of the organic salt dopant TrTPFB used in Example 1 of the present invention;

[0032] Figure 2 It is an atomic force microscope (AFM) image of the C 10 -DNTT single-crystal organic thin film doped with TrTPFB before and after on hafnium oxide in Example 1 of the present invention; where a is the thickness and roughness of the single-layer C 10 -DNTT single-crystal organic thin film before doping, and b is the thickness and roughness of the single-layer C 10 -DNTT single-crystal organic thin film after doping with 0.5 wt% TrTPFB;

[0033] Figure 3 It is the curves of current density, mobility and threshold voltage of the C 10 -DNTT single-crystal organic thin film transistor doped with 0.5 wt% TrTPFB before and after on hafnium oxide in Example 1 of the present invention changing with voltage and temperature; where a is the single-layer C 10-DNTT single-crystalline organic thin-film transistor current density versus voltage curve, b is for monolayer C before and after doping with 0.5 wt% TrTPFB 10 -DNTT single-crystalline organic thin-film transistor mobility and threshold voltage versus temperature curve;

[0034] Figure 4 For the C before and after doping with 0.1 wt% TrTPFB on hafnium oxide prepared in Example 2 of the present invention 10 -DNTT polycrystalline organic thin-film ultraviolet-visible-near-infrared spectrum;

[0035] Figure 5 For the C before and after doping with TrTPFB prepared in Example 2 of the present invention 10 -DNTT polycrystalline organic thin-film energy level schematic diagram;

[0036] Figure 6 For the C before and after doping with 0.5 wt% TrTPFB on hafnium oxide prepared in Example 2 of the present invention 10 -DNTT polycrystalline organic thin-film transistor current density, mobility and threshold voltage versus voltage and temperature curves; where a is for monolayer C before and after doping with 0.5 wt% TrTPFB 10 -DNTT polycrystalline organic thin-film transistor current density versus voltage curve, b is for monolayer C before and after doping with 0.5 wt% TrTPFB 10 -DNTT polycrystalline organic thin-film transistor mobility and threshold voltage versus temperature curve;

[0037] Figure 7 For the C after doping with 1 wt% TrTPFB on hafnium oxide prepared in Comparative Example 1 of the present invention 10 AFM image of -DNTT single-crystalline organic thin-film. Detailed implementation mode

[0038] The technical solution of the present invention will be further described below in conjunction with the drawings and embodiments.

[0039] Example 1

[0040] The two-dimensional organic thin-film transistor of the liquid-phase doped organic salt of the present invention, a single-crystalline organic thin-film transistor based on 2,9-didecyl dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C 10 -DNTT) doped with triphenylcarbenium tetrakis(pentafluorophenyl)borate (TrTPFB) on hafnium oxide, the preparation method thereof comprises the following steps:

[0041] (1) After cleaning the silicon substrate, place it into the atomic layer deposition chamber, evacuate the chamber, set the temperature to 150 °C, and after the temperature stabilizes for 1 h, use hafnium tetrakis(dimethylamido) as the metal source and water as the oxygen source. The pulse time for the hafnium source and the oxygen source is 300 ms and 20 ms respectively, the cleaning time between two pulses is 30 s, set 180 cycles, and grow a 30 nm hafnium oxide thin film;

[0042] (2) Grow a single-layer organic semiconductor thin film on the hafnium oxide substrate using the solution shearing method: First, prepare the solution for growing the organic semiconductor thin film, use the solvent 1,2,3,4-tetrahydronaphthalene to dissolve C 10 -DNTT, and prepare it to a saturated concentration of 0.5 - 0.7 mg / mL; Then, inject the organic semiconductor solution into the gap between the oxide substrate and the upper plate. The distance between the substrate and the upper plate of the device is set to 80 - 120 μm, the tilt angle of the upper plate is fixed at 10 - 15°, the temperatures of the upper plate and the lower plate are set to 64 - 68 °C, the moving speed of the upper plate is set to 2.5 - 3.5 μm / s, and through the electric displacement stage, control the upper plate to continuously move in one direction to complete the growth of the single-layer organic thin film, and the thickness of the obtained single-layer C 10 -DNTT single crystal thin film is about 3.7 nm;

[0043] (3) Add the organic salt powder TrTPFB into the organic solvent acetonitrile to prepare a dopant solution, and the mass percentage concentration of the dopant solution is 0.1 - 0.5 wt%, immerse the organic semiconductor thin film into the dopant solution to prepare a doped thin film, and the film thickness is 4 nm; The acetonitrile solvent has less damage to the single-layer C 10 -DNTT, and the 0.1 - 0.5 wt% TrTPFB solution has efficient doping characteristics for the single-layer C 10 -DNTT thin film, and the electrical properties of the doped organic single crystal thin film transistor have been significantly improved, and the charge transport characteristics remain strip-shaped transport;

[0044] (4) Individually write the source / drain electrode pattern of the transistor on the silicon wafer substrate using electron beam lithography, and the width of the source / drain electrode is about 80 μm; Then deposit 10 nm platinum / 190 nm gold by electron beam evaporation, and obtain the source / drain electrode after removing the photoresist. The contact layer of the source / drain electrode is platinum, and the support layer is gold; Then, transfer the source / drain electrode metal to the prepared doped layer by the van der Waals transfer method, so that the doped thin film and the organic semiconductor thin film are protected from the impact or thermal damage caused by high-energy metal particles during the metal deposition process.

[0045] Figure 1Schematic diagram of the molecular structure of the organic salt dopant TrTPFB used in Example 1; TrTPFB has an effective electrophile, where the triphenylmethyl cation (Trytl+) can easily perform electrophilic attacks on electron-rich conjugated systems (such as thiophene, benzene, and thiazole), thus promoting p-type doping.

[0046] Figure 2 AFM images of the C 10 -DNTT single-crystal organic thin film on hafnium oxide before and after doping with TrTPFB prepared in Example 1; where a is the thickness and roughness of the single-layer C 10 -DNTT single-crystal organic thin film before doping, and b is the thickness and roughness of the single-layer C 10 -DNTT single-crystal organic thin film after doping with 0.5 wt% TrTPFB; the comparison results show that compared with the undoped single-layer crystal, when doped with 0.5 wt% TrTPFB, the thickness and surface roughness of the single-layer C10-DNTT crystal increase by about 10% and 150% respectively, and TrTPFB is adsorbed on the C 10 -DNTT surface.

[0047] Figure 3 Curves of the current density, mobility, and threshold voltage of the C 10 -DNTT single-crystal organic thin film transistor on hafnium oxide before and after doping with 0.5 wt% TrTPFB prepared in Example 1 as a function of voltage and temperature; where a is the curve of the current density of the single-layer C 10 -DNTT single-crystal organic thin film transistor before and after doping with 0.5 wt% TrTPFB as a function of voltage, and b is the curves of the mobility and threshold voltage of the single-layer C 10 -DNTT single-crystal organic thin film transistor before and after doping with 0.5 wt% TrTPFB as a function of temperature; after doping, both the current and mobility of the C 10 -DNTT single-crystal organic thin film transistor device are significantly enhanced, increasing by about 26% and 11% respectively at room temperature. The threshold voltage of the single-crystal organic thin film transistor also changes from -0.08 before doping to 0.36 after doping, shifting significantly towards the positive voltage, demonstrating the efficient p-type doping of 0.5 wt% TrTPFB to the C 10 -DNTT single-crystal organic thin film. In addition, during the process of cooling from 293K to 230K, both the single-layer C 10 -DNTT single-crystal organic thin film transistors before and after doping with 0.5 wt% TrTPFB exhibit the characteristics of band-like transport.

[0048] Example 2

[0049] The two-dimensional organic thin-film transistor with liquid-phase doped organic salt is a polycrystalline organic thin-film transistor based on 2,9-didecylnaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C 10 -DNTT) doped with trityl tetrakis(pentafluorophenyl)borate (TrTPFB) on hafnium oxide. Its manufacturing method includes the following steps:

[0050] (1) After cleaning the silicon substrate, place it in the atomic layer deposition chamber, evacuate the chamber, set the temperature to 150 °C, and after the temperature stabilizes for 1 h, use tetrakis(dimethylamino)hafnium as the metal source and water as the oxidation source. The pulse time for each hafnium source and oxidation source is 300 ms and 20 ms respectively, and the cleaning time between two pulses is 30 s. Set 180 cycles to grow a 30-nm hafnium oxide thin film;

[0051] (2) Grow a single-layer organic semiconductor thin film on the hafnium oxide substrate using the solution shearing method: First, prepare the solution for growing the organic semiconductor thin film, dissolve C 10 -DNTT with the solvent 1,2,3,4-tetrahydronaphthalene and prepare it to a saturated concentration of 0.5 - 0.7 mg / mL; then, inject the organic semiconductor solution into the gap between the oxide substrate and the upper plate. The distance between the substrate and the upper plate of the device is set to 80 - 120 μm, the tilt angle of the upper plate is fixed at 10 - 15°, the temperatures of the upper plate and the lower plate are set to 64 - 68 °C, and the moving speed of the upper plate is set to 2.5 - 3.5 μm / s. Control the upper plate to move continuously in one direction through the electric displacement stage to complete the growth of the single-layer organic thin film and obtain a single-layer C 10 -DNTT polycrystalline thin film;

[0052] (3) Add the organic salt powder TrTPFB to the organic solvent acetonitrile to prepare a dopant solution. The mass percentage concentration of the dopant solution is 0.1 - 0.5 wt%. The 0.1 - 0.5 wt% TrTPFB solution has efficient doping characteristics for the single-layer C 10 -DNTT thin film. Immerse the organic semiconductor thin film in the dopant solution to prepare a doped thin film; the acetonitrile solvent has less damage to the single-layer C 10 -DNTT, and the electrical properties of the doped organic polycrystalline thin-film transistor have been significantly improved, and the charge transport characteristics have also been restored from multiple trap capture and release transport to quasi-band transport;

[0053] (4) The source / drain electrode patterns of the transistor are separately written on the silicon wafer substrate by electron beam lithography, and the width of the source / drain electrode is about 80 μm. Then, 10 nm of platinum / 190 nm of gold is deposited by electron beam evaporation, and after removing the photoresist, the source / drain electrodes are obtained. The contact layer of the source / drain electrode is platinum, and the support layer is gold. Then, the source / drain electrode metal is transferred to the prepared doped layer by the van der Waals transfer method, so that the doped thin film and the organic semiconductor thin film are protected from the impact or thermal damage caused by high-energy metal particles during the metal deposition process.

[0054] Figure 4 The UV-Vis-NIR spectra of the C 10 -DNTT polycrystalline organic thin film doped with 0.1 wt% TrTPFB before and after preparation in Example 2; the results show that the single-layer C 10 -DNTT polycrystalline thin film has new π-π absorption and absorption between band gaps at 1420 nm after doping with 0.1 wt% TrTPFB, indicating the appearance of polarons, which proves that free carriers are generated in the single-layer C 10 -DNTT polycrystalline thin film doped with 0.1 wt% TrTPFB.

[0055] Figure 5 The energy level schematic diagrams of the C 10 -DNTT polycrystalline organic thin film doped with TrTPFB before and after preparation in Example 2; this energy level schematic diagram is drawn according to the results of ultraviolet photoelectron spectroscopy, comparing the energy level schematic diagrams of the single-layer C 10 -DNTT polycrystalline thin film before doping, after doping with 0.1 wt% TrTPFB and 0.5 wt% TrTPFB, which proves that the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital and the vacuum energy level of the single-layer C 10 -DNTT polycrystalline thin film doped with 0.1 wt% TrTPFB and 0.5 wt% TrTPFB all move upward, and the Fermi energy level moves towards the HOMO, indicating the p-type doping effect, and the doping effect can be adjusted by changing the dopant concentration. The results show that the organic salt can perform an electrophilic attack on the C 10 -DNTT polycrystalline thin film, induce a redistribution of the electronic state, and make the Fermi energy level move towards the HOMO energy level. This effect will greatly improve the charge transport at the polycrystalline grain boundaries, is expected to passivate the traps induced by the grain boundaries, and significantly improve the electrical performance of the device.

[0056] Figure 6 The curves of the current density, mobility and threshold voltage of the C 10 -DNTT polycrystalline organic thin film transistor prepared in Example 2 doped with 0.5 wt% TrTPFB before and after changing with voltage and temperature; where a is the single-layer C 10- The variation curve of the current density of the C-DNTT polycrystalline organic thin-film transistor with voltage, and b is the single-layer C before and after doping with 0.5 wt% TrTPFB 10 - The variation curves of the mobility and threshold voltage of the C-DNTT polycrystalline organic thin-film transistor with temperature; The results show that after doping, both the current and mobility of the C-DNTT polycrystalline organic thin-film transistor device are significantly enhanced, increasing by about 26% and 11% respectively at room temperature. The threshold voltage of the polycrystalline organic thin-film transistor also changes from -0.24 before doping to 0.21 after doping, shifting significantly towards the positive voltage, demonstrating the efficient p-type doping of 0.5 wt% TrTPFB to C 10 -DNTT. In addition, during the process of cooling from 293K to 230K, the charge transport characteristics of the single-layer C-DNTT polycrystalline organic thin-film transistor before and after doping with 0.5 wt% TrTPFB are restored from multiple trap capture and release transport to quasi-band transport similar to that of single-crystalline organic thin-film transistors, demonstrating that the organic salt TrTPFB doping of C 10 -DNTT polycrystalline thin films greatly improve C 10 - The charge transport at the grain boundaries of the C-DNTT polycrystalline film, eliminating the adverse effects brought by the grain boundary effect, and significantly improving the electrical properties such as the current density, mobility, and threshold voltage of the device. 10 -DNTT polycrystalline thin films greatly improve C 10 - The charge transport at the grain boundaries of the C-DNTT polycrystalline film, eliminating the adverse effects brought by the grain boundary effect, and significantly improving the electrical properties such as the current density, mobility, and threshold voltage of the device.

[0057] Comparative Example 1

[0058] The two-dimensional organic thin-film transistor of the liquid-phase doped organic salt of the present invention is based on a 2,9-didecylnaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C 10 -DNTT) single-crystalline organic thin-film transistor doped with tris(pentafluorophenyl)borate (TrTPFB) on hafnium oxide, and its manufacturing method includes the following steps:

[0059] (1) After cleaning the silicon substrate, place it in the atomic layer deposition chamber, evacuate the chamber, set the temperature to 150 °C, and after the temperature is stable for 1 h, use tetrakis(dimethylamino)hafnium as the metal source and water as the oxidation source. The pulse time of the hafnium source and the oxidation source is 300 ms and 20 ms respectively, and the cleaning time between two pulses is 30 s. Set 180 cycles to grow a 30 nm hafnium oxide thin film;

[0060] (2) Grow a single-layer organic semiconductor thin film on the hafnium oxide substrate using the solution shearing method: First, prepare the solution for growing the organic semiconductor thin film, and use solvent 1,2,3,4-tetrahydronaphthalene to dissolve C 10-DNTT, prepared to a saturation concentration of 0.5-0.7 mg / mL; then, the organic semiconductor solution is injected into the gap between the oxide substrate and the upper plate, the distance between the substrate and the upper plate of the device is set to 80-120 μm, the inclination angle of the upper plate is fixed to 10-15°, the temperature of the upper plate and the lower plate is set to 64-68°C, the moving speed of the upper plate is set to 2.5-3.5 μm / s, and the upper plate is controlled to move continuously in one direction through an electric displacement stage to complete the growth of a single-layer organic thin film. The obtained single-layer C 10 -The thickness of the DNTT single crystal film is about 3.7nm;

[0061] (3) adding organic salt powder TrTPFB into organic solvent acetonitrile to prepare a dopant solution, wherein the mass percentage concentration of the dopant solution is 1 to 2 wt %, and immersing the organic semiconductor film in the dopant solution to prepare a doped film; the acetonitrile solvent has an effect on the monolayer C 10 -DNTT is less damaged, and the dopant concentration above 0.5wt% has little effect on the monolayer C 10 -The crystallinity and roughness of DNTT films have a significant impact, which will reduce the performance of doped organic thin film transistors;

[0062] (4) The source / drain electrode pattern of the transistor is written on the silicon wafer substrate by electron beam lithography, and the width of the source / drain electrode is about 80 μm; then 10 nm platinum / 190 nm gold is deposited by electron beam evaporation, and the source / drain electrode is obtained after removing the photoresist. The contact layer of the source / drain electrode is platinum and the supporting layer is gold; then, the source / drain electrode metal is transferred to the prepared doping layer by van der Waals transfer method, so that the doped film and the organic semiconductor film are protected from impact or thermal damage caused by high-energy metal particles during the metal deposition process.

[0063] Figure 7 The C prepared in Comparative Example 1 is based on hafnium oxide doped with 1 wt% TrTPFB. 10 -AFM image of DNTT single crystal organic film; it is found that C 10 -DNTT single crystal organic film surface holes, indicating that excessive doping concentration will destroy the crystallinity and uniformity of the C10-DNTT film, thus leading to the performance degradation of the transistor device.

Claims

1. A two-dimensional organic thin film doped with an organic salt, characterized in that, It includes an organic semiconductor thin film and a doped thin film, and the doped thin film is on the organic semiconductor thin film; the organic semiconductor material is a conjugated organic small molecule with an alkyl side chain, and the dopant material is an organic salt.

2. The two-dimensional organic film doped with an organic salt according to claim 1, characterized in that, The conjugated organic small molecule includes 2,9-didecyl dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene, 2,9-dihexyl naphtho[2,3-b]naphtho[2',3':4,5]thieno[3,2-d]dithiophene or 2,9-ditetradecyl naphtho[2,3-b]naphtho[2',3':4,5]thieno[3,2-d]dithiophene.

3. The two-dimensional organic film doped with an organic salt according to claim 1, characterized in that, The dopant material is triphenylcarbenium tetrakis(pentafluorophenyl)borate.

4. A two-dimensional organic thin film transistor doped with an organic salt, characterized in that, It includes a substrate, an insulating layer, a two-dimensional organic thin film doped with an organic salt, and source / drain electrodes; the insulating layer is an oxide.

5. The two-dimensional organic thin-film transistor doped with an organic salt according to claim 4, wherein The insulating layer is hafnium oxide, aluminum oxide or zirconium oxide.

6. A method for preparing a doped organic salt two-dimensional organic thin film according to claim 1, characterized in that, It includes the following steps: (1) Grow an oxide on the substrate as the insulating layer; (2) Grow a two-dimensional organic semiconductor thin film on the surface of the oxide as the semiconductor channel layer; (3) Prepare a doped thin film on the organic semiconductor thin film to obtain a two-dimensional organic thin film doped with an organic salt.

7. The preparation method of the two-dimensional organic thin film transistor doped with a liquid-phase organic salt according to claim 6, characterized in that, In step (2), the solvent of the solution for growing the two-dimensional organic semiconductor thin film is at least one of toluene, chlorobenzene, and 1,2,3,4-tetrahydronaphthalene. An organic small molecule powder is added to the solvent to prepare an organic semiconductor solution, and the concentration of the organic semiconductor solution is 0.5 - 0.7 mg / mL.

8. The preparation method of the two-dimensional organic thin film transistor with liquid-phase doped organic salt according to claim 6, characterized in that, In step (2), the semi-circular solution shearing method is used to grow the two-dimensional organic semiconductor single crystal thin film. The distance between the substrate and the upper plate is set to 80 - 100 μm, the tilt angle of the upper plate is 10 - 15°, the growth temperature is 64 - 68 °C. The growth solution is injected into the gap between the metal substrate and the upper plate. At the corresponding temperature, the upper plate is controlled to continuously move in one direction at a speed of 2.5 - 3.5 μm / s to complete the growth of the organic semiconductor thin film.

9. The preparation method of the two-dimensional organic thin film transistor doped with a liquid-phase organic salt according to claim 6, wherein, In step (3), the solvent of the solution for preparing the doped thin film is at least one of hexane, chloroform, dichloromethane, and acetonitrile. An organic salt powder is added to the solvent to prepare a dopant solution, and the mass percentage concentration of the dopant solution is 0.1 - 0.5 wt%.

10. A method for preparing a two-dimensional organic thin-film transistor of the doped organic salt according to claim 4, characterized in that, It includes the following steps: (1) Grow an oxide on the substrate as the insulating layer; (2) Grow a two-dimensional organic semiconductor thin film on the surface of the oxide as the semiconductor channel layer; (3) Prepare a doped thin film on the organic semiconductor thin film; (4) Take another substrate to prepare source / drain electrodes, and transfer the source / drain electrodes to the doped thin film to obtain the doped two-dimensional organic thin film transistor.

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