Gateless organic thin-film transistors regulated by piezoelectric electrets and their fabrication methods

Abstract

This invention discloses a gateless organic thin-film transistor controlled by a piezoelectric electret and its fabrication method, relating to the field of organic electronics technology. The method includes: obtaining a polypropylene film; treating the polypropylene film by thermal expansion and then subjecting the thermally expanded polypropylene film to corona polarization to obtain a porous polypropylene piezoelectric electret film; depositing a pentaphenyl semiconductor layer on the surface of the porous polypropylene piezoelectric electret film to form an organic semiconductor layer; depositing source and drain electrodes on the organic semiconductor layer using a photomask; depositing an encapsulation layer on at least a portion of the surface of the source electrode, at least a portion of the surface of the drain electrode, at least a portion of the surface of the organic semiconductor layer, and between the source and drain electrodes; and leading out the source and drain electrodes using wires. This invention integrates the advantages of passive piezoelectric tactile sensing with transistor signal amplification through the coupling of piezoelectric effect, field effect, and semiconductor properties, realizing a direct, active human-machine interaction mode.

Description

Technical Field

[0001] This invention belongs to the field of organic electronics technology, specifically relating to a gateless organic thin-film transistor controlled by a piezoelectric electret and its fabrication method. Background Technology

[0002] Organic thin-film transistors (OTFTs) utilize widely available semiconductor materials, employ simple and diverse film-forming techniques, and undergo low-temperature processing, enabling large-area, low-cost production. They have already achieved successful commercial applications in active driving circuits for LCD and OLED displays, organic RFID tags, and chemical / biological sensors. Compared to inorganic field-effect transistors, OTFTs offer unique advantages such as lightweight, flexibility, biocompatibility, and highly flexible material and device structure design. This has led to increasing attention from academia and industry regarding the broader market prospects of OTFTs in wearable devices, electronic skin, robotics, mobile and telemedicine, and other artificial intelligence fields.

[0003] In the development of artificial intelligence, the ability to sense the mechanical movements of living organisms, construct active human-computer interaction interfaces, and directly control electronic devices with biosignals is of great significance for the intelligent development of flexible electronic devices. In existing technologies, organic thin-film transistors (OTFTs) have good signal amplification capabilities and can be directly applied to flexible electronic devices. The most common approach in traditional flexible electronic devices is to integrate a pressure sensor array with the OTFT on the same flexible chip platform. However, the pressure sensor is not directly integrated onto the OTFT, preventing direct interaction with human movements. Although novel OTFT pressure sensors have been developed in recent years, employing a dielectric layer with a microstructure, the capacitance changes due to the change in contact area between the dielectric layer and the gate when a voltage is applied, thus affecting the effective gate voltage at the interface between the dielectric layer and the semiconductor. This allows for direct pressure-driven regulation of carrier transport and the integration of pressure sensing and signal amplification. Regardless of the method used, the OTFT still requires an electrical signal to be received through a gate electrode. However, the threshold voltage of OTFTs is generally high, making it difficult to meet the further low-power requirements of future flexible electronic devices. Furthermore, frequent bending during operation can easily damage the gate electrode, making it difficult to guarantee the overall stability and durability of the device.

[0004] Therefore, it is urgent to improve the shortcomings of existing OTFT devices, such as high power consumption and difficulty in direct active interaction with the external environment. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a gateless organic thin-film transistor controlled by a piezoelectric electret and a method for fabricating the same. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for fabricating a gateless organic thin-film transistor controlled by a piezoelectric electret, comprising:

[0007] Obtain polypropylene film;

[0008] Polypropylene film was treated by thermal expansion, and then corona polarization was performed on the thermally expanded polypropylene film to obtain a porous polypropylene piezoelectric electret film.

[0009] An organic semiconductor layer is formed by vapor deposition of a pentabenzene semiconductor layer on the surface of a porous polypropylene piezoelectric electret film.

[0010] Sources and drains are deposited at intervals on an organic semiconductor layer using a photomask;

[0011] An encapsulation layer is deposited on the surface of at least a portion of the source, at least a portion of the drain, at least a portion of the organic semiconductor layer, and between the source and drain, and the source and drain are led out using wires.

[0012] In a second aspect, the present invention provides a gateless organic thin-film transistor controlled by a piezoelectric electret, comprising: fabrication using the piezoelectric electret controlled gateless organic thin-film transistor fabrication method provided in the above embodiments of the present application.

[0013] The beneficial effects of this invention are:

[0014] (1) The present invention provides a method for fabricating a gateless organic thin film transistor controlled by a piezoelectric electret. The piezoelectric material is a polymer piezoelectric electret film, which has strong controllability in the shape, size and porosity of its internal pores. The giant electric dipole formed by the directional arrangement of space charges gives the piezoelectric electret a strong piezoelectric effect comparable to that of ceramic materials. Furthermore, the organic electret formed is thin, flexible, widely available, easy to form films over large areas, low in cost and environmentally friendly, and perfectly compatible with the manufacturing process and flexible characteristics of OTFT.

[0015] (2) The present invention provides a method for fabricating a gateless organic thin-film transistor controlled by a piezoelectric electret. The polymer piezoelectric electret has high electromechanical conversion efficiency and short response time, and can convert mechanical signals into piezoelectric potential in real time. The piezoelectric electret film is also the dielectric layer of the OTFT device in the present invention, so that the piezoelectric potential on the surface of the piezoelectric electret film is directly applied to the contact interface between it and the organic semiconductor layer, thereby controlling the carrier concentration on the surface of the organic semiconductor. In this way, the dielectric layer of the piezoelectric electret film can actively sense tactile stress, and the generated piezoelectric potential is directly used as the input electrical signal of the transistor to modulate the output current of the device.

[0016] (3) The present invention provides a method for fabricating a gateless organic thin film transistor controlled by a piezoelectric electret. Based on the positive and negative charge of the bound charge on the surface of the piezoelectric electret film, the working mode of the OTFT device can be designed as either enhancement mode or depletion mode. In addition, the OTFT tactile sensor based on the piezoelectric electret control of the present invention does not require a gate, which can not only greatly reduce the power consumption of flexible electronic integrated devices such as electronic skin, but also improve the overall reliability and durability of flexible electronic devices. More importantly, by coupling the piezoelectric effect, field effect and semiconductor properties, the advantages of piezoelectric passive tactile sensing and transistor signal amplification function are integrated, realizing a direct and active human-machine interaction mode.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for fabricating a gateless organic thin-film transistor controlled by a piezoelectric electret, provided in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a gateless organic thin-film transistor provided in an embodiment of the present invention;

[0020] Figure 3 (a) is a schematic diagram of a commercially available polypropylene film provided in an embodiment of the present invention;

[0021] Figure 3 (b) is a schematic diagram of another structure of the commercially available polypropylene film provided in an embodiment of the present invention;

[0022] Figure 3 (c) is a schematic diagram of a porous polypropylene film after thermal expansion provided in an embodiment of the present invention;

[0023] Figure 3 (d) is another structural schematic diagram of the porous polypropylene film after thermal expansion provided in the embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram showing the relationship between the piezoelectric coefficients of commercially available polypropylene film and polypropylene piezoelectric electret film provided in an embodiment of the present invention.

[0025] Figure 5 This is a SEM schematic diagram of an organic semiconductor provided in an embodiment of the present invention;

[0026] Figure 6 This is an optical microscopic schematic diagram of a channel provided in an embodiment of the present invention;

[0027] Figure 7(a) is a response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to the dynamic current of a stepped mechanical signal;

[0028] Figure 7 (b) is an IV output characteristic curve of the gateless organic thin film transistor provided in the embodiment of the present invention under different pressures;

[0029] Figure 7 (c) is a potential diagram of the surface of a commercially available polypropylene film in Comparative Example 1 device measured by a scanning Kelvin probe microscope according to an embodiment of the present invention.

[0030] Figure 8 (a) is a dynamic current response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to a stepped mechanical signal;

[0031] Figure 8 (b) is a dynamic current response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to a periodic mechanical signal;

[0032] Figure 8 (c) is a graph showing the IV output characteristics of the gateless organic thin-film transistor provided in the embodiment of the present invention under different pressures;

[0033] Figure 9 (a) is a schematic diagram of a gateless depletion type OTFT regulated by a polypropylene piezoelectric electret film according to an embodiment of the present invention.

[0034] Figure 9 (b) is a dynamic current response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to step-type mechanical signal stimulation;

[0035] Figure 9 (c) is a schematic diagram of the IV output characteristic curves of the gateless organic thin film transistor under different pressures provided in the embodiment of the present invention;

[0036] Figure 9 (d) is a schematic diagram of the dynamic current response curve during the palm opening and closing test provided in the embodiment of the present invention;

[0037] Figure 10 (a) is a schematic diagram of the dynamic current response curve of the piezoelectric electret-controlled gateless enhancement-mode OTFT stress sensor device to a stepped mechanical signal provided in an embodiment of the present invention.

[0038] Figure 10 (b) is a schematic diagram of the dynamic current response curve of the piezoelectric electret-controlled gateless enhancement-mode OTFT stress sensor device to a periodic mechanical signal provided in the embodiment of the present invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0040] In existing technologies, on the one hand, the most common approach for traditional flexible electronic devices is to integrate a pressure sensor array with an OTFT on the same flexible chip platform. However, the pressure sensor is not directly integrated onto the OTFT, preventing the OTFT from directly interacting with human movements. Although new OTFT pressure sensors have been developed in recent years, employing a dielectric layer with a microstructure, the capacitance changes due to the change in contact area between the dielectric layer and the gate when a voltage is applied, thereby affecting the effective gate voltage at the interface between the dielectric layer and the semiconductor. This achieves the goal of directly controlling carrier transport under pressure and integrating the pressure sensor with signal amplification. However, the OTFT requires an electrical signal to be connected through a gate electrode, and the threshold voltage of OTFTs is generally high, making it difficult to meet the further requirements of low power consumption in future flexible electronic devices. On the other hand, replacing the gate potential with piezoelectric potential—that is, the piezoelectric material generates a potential difference when the stress changes—can directly and actively control the device's operation by utilizing the coupling of the piezoelectric effect, field effect, and semiconductor properties. Typically, piezoelectrically active ceramic materials are the most widely researched and applied piezoelectric materials, but their brittleness makes them unsuitable for large-area integration of flexible electronic devices. Polyvinylidene fluoride (PVDF) and its derivatives containing the β-crystal form are the most important organic piezoelectric materials; although polymer films have good flexibility, their piezoelectric coefficient is relatively low. Therefore, there is an urgent need to find organic flexible materials with strong piezoelectric properties that can be formed into large-area films, and to design gateless structures for traditional OTFT devices, integrating the advantages of piezoelectric passive tactile sensing with transistor signal amplification. Furthermore, it is crucial to study the direct impact of mechanical signals on carrier transport characteristics and develop low-power, active flexible electronic devices.

[0041] In view of this, the present invention provides a gateless organic thin-film transistor controlled by a piezoelectric electret and a method for fabricating the same. The resulting polymer piezoelectric electret has high electromechanical conversion efficiency and short response time, and can convert mechanical signals into piezoelectric potential in real time.

[0042] Please see Figure 1 and Figure 2 As shown, Figure 1 This is a flowchart of a method for fabricating a gateless organic thin-film transistor controlled by a piezoelectric electret, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of a gateless organic thin-film transistor provided in an embodiment of the present invention. The present invention provides a method for fabricating a gateless organic thin-film transistor controlled by a piezoelectric electret, comprising:

[0043] S101. Obtain polypropylene film.

[0044] Specifically, in this embodiment, the polypropylene film is obtained through commercial purchase.

[0045] S102. The polypropylene film is treated by thermal expansion, and the thermally expanded polypropylene film is subjected to corona polarization treatment to obtain a porous polypropylene piezoelectric electret film.

[0046] Specifically, in this embodiment, a polypropylene film is placed inside an autoclave; nitrogen gas is introduced into the sealed chamber of the autoclave at room temperature and allowed to stand for 0 to 8 hours; wherein the pressure of the introduced nitrogen gas is 1 MPa to 5 MPa; the autoclave is heated to 70°C to 200°C and held at that temperature for 0.5 to 6 hours; wherein, during the holding process, the pressure in the sealed chamber of the autoclave is maintained at 1.2 MPa to 7.5 MPa; the nitrogen gas in the sealed chamber of the autoclave is rapidly released within 1 to 10 seconds to complete the thermal expansion treatment of the polypropylene film; wherein, the resulting polypropylene film has highly controllable internal pore shape, size, and porosity, and the giant electric dipoles formed by the directional arrangement of space charges give the piezoelectric electret a strong piezoelectric effect comparable to that of ceramic materials.

[0047] A thermally expanded polypropylene film is placed under the corona needle tip of a corona polarization device, with a distance of 1 cm to 5 cm between the thermally expanded polypropylene film and the corona needle tip, and a polarization time of 1 min to 10 min, to obtain a porous polypropylene piezoelectric electret film. The corona voltage is +15kV to +30kV or -30kV to -15kV. The resulting porous polypropylene piezoelectric electret film is thin, flexible, and easy to form in large areas, perfectly matching the manufacturing process and flexible characteristics of OTFT. Furthermore, the polymer piezoelectric electret has high electromechanical conversion efficiency and short response time, enabling it to convert mechanical signals into piezoelectric potentials in real time.

[0048] It should be noted that the thickness of the polypropylene film after thermal expansion is 0.5 to 3 times the thickness of the polypropylene film; wherein, both the thickness of the polypropylene film after thermal expansion and the thickness of the polypropylene film are thicknesses along the first direction.

[0049] It should also be noted that the polypropylene film after thermal expansion treatment includes multiple pores, the length of which is 1μm to 100μm and the height is 0.1μm to 10μm, and adjacent pores are independent and non-connected; wherein, the length of the pore is the dimension along the second direction, the height of the pore is the dimension along the first direction, the first direction and the second direction intersect, and optionally, the first direction is perpendicular to the second direction.

[0050] S103. A pentene semiconductor layer is deposited on the surface of a porous polypropylene piezoelectric electret film to form an organic semiconductor layer.

[0051] Specifically, in this embodiment, the thickness of the formed organic semiconductor along the first direction is 20nm to 100nm.

[0052] S104. Deposit source and drain electrodes spaced apart on an organic semiconductor layer using a photomask.

[0053] Specifically, in this embodiment, the thickness of both the source and drain is 20nm to 100nm; the length of the channel formed between the source and drain is 10μm to 100μm, and the width of the channel is 50μm to 1000μm.

[0054] S105. Deposit an encapsulation layer on the surface of at least a portion of the source, the surface of at least a portion of the drain, the surface of at least a portion of the organic semiconductor layer, and between the source and drain, and lead out the source and drain using wires.

[0055] Specifically, in this embodiment, the thickness of the encapsulation layer along the first direction is 100nm to 500nm, and the material of the encapsulation layer is tetradecane.

[0056] In summary, the piezoelectric electret-controlled gateless organic thin-film transistor fabrication method provided in this embodiment features a polymer piezoelectric electret with high electromechanical conversion efficiency and short response time, capable of converting mechanical signals into piezoelectric potentials in real time. The piezoelectric electret film also serves as the dielectric layer of the OTFT device in this invention, allowing the piezoelectric potential on the surface of the piezoelectric electret film to be directly applied at its interface with the organic semiconductor layer, thereby controlling the carrier concentration on the organic semiconductor surface. This enables the piezoelectric electret film dielectric layer to actively sense tactile stress, and the generated piezoelectric potential directly serves as the input electrical signal of the transistor, modulating the output current of the device.

[0057] It should be noted that, Figure 2 The illustrated embodiment is merely a schematic diagram showing the positional relationship of the polypropylene piezoelectric electret film, organic semiconductor layer, source, drain, and encapsulation layer, and does not represent actual dimensions. Figure 2 The embodiment shown is a polypropylene piezoelectric electret film with the surface near the corona needle during polarization treatment.

[0058] Example 1: The piezoelectric electret-controlled gateless enhancement organic thin-film transistor was fabricated using the following method.

[0059] S101, Commercially available polypropylene film.

[0060] S102. Place the purchased polypropylene film into an autoclave. At room temperature, purge nitrogen into the sealed chamber of the autoclave. When the pressure in the sealed chamber reaches 1 MPa, shut off the gas source and stop purging nitrogen into the sealed chamber. Immediately heat the autoclave to 70°C and maintain the temperature for 6 hours. During the heat maintenance, the pressure in the sealed chamber of the autoclave should be maintained at approximately 1.2 MPa. Finally, rapidly release the nitrogen from the autoclave within 1 second to obtain a porous polypropylene film. Place the porous polypropylene film under a corona polarization device with a corona voltage of +15 kV, a distance of 1 cm from the porous polypropylene film to the corona needle tip, and a polarization time of 10 minutes. After corona polarization treatment, a porous polypropylene piezoelectric electret film is obtained.

[0061] S103. A 100 nm thick pentacene semiconductor layer is deposited on the surface of the porous polypropylene piezoelectric electret film obtained in step S102.

[0062] S104. Deposit 100nm thick, spaced-apart source and drain electrodes on an organic semiconductor layer using a mask to form a channel with a length of 100μm and a width of 1000μm. Optionally, the source and drain electrodes are made of gold.

[0063] S105. A 300 nm thick tetradecane encapsulation layer is deposited on the source and drain, and the source and drain are led out by wires to complete the piezoelectric electret-controlled enhancement-mode gateless organic thin film transistor; wherein the encapsulation layer covers at least part of the organic semiconductor layer, and the encapsulation layer covers the space between the source and drain.

[0064] In summary, the gateless organic thin-film transistor controlled by the piezoelectric electret fabricated in this embodiment can be used as an active flexible tactile sensing element in the field of human-computer direct interaction in low-power organic electronic integrated devices.

[0065] Example 2: The piezoelectric electret-controlled gateless enhancement organic thin-film transistor was fabricated using the following method.

[0066] S101, Commercially available polypropylene film.

[0067] S102. Place the purchased polypropylene film into an autoclave. At room temperature, purge nitrogen into the sealed chamber of the autoclave. When the pressure in the sealed chamber reaches 2 MPa, shut off the gas source and stop purging nitrogen into the sealed chamber. After standing for 2 hours, heat the autoclave to 120°C and hold for 3 hours. During the holding period, maintain the pressure in the sealed chamber of the autoclave at approximately 2.8 MPa. Finally, rapidly release the nitrogen from the autoclave within 3 seconds to obtain a porous polypropylene film. Place the porous polypropylene film under a corona polarization device with a corona voltage of +22 kV, a distance of 3 cm from the porous polypropylene film to the corona needle tip, and a polarization time of 5 minutes. After corona polarization treatment, a porous polypropylene piezoelectric electret film is obtained.

[0068] S103. A 70 nm thick pentacene semiconductor layer is deposited on the surface of the porous polypropylene piezoelectric electret film obtained in step S102.

[0069] S104. Deposit 80nm thick, spaced-apart source and drain electrodes on an organic semiconductor layer using a photomask to form a channel with a length of 50μm and a width of 250μm. Optionally, the source and drain electrodes are made of gold.

[0070] S105. A 200 nm thick tetradecane encapsulation layer is deposited on the source and drain, and the source and drain are led out by wires to complete the piezoelectric electret-controlled enhancement-mode gateless organic thin-film transistor; wherein the encapsulation layer covers at least part of the organic semiconductor layer, and the encapsulation layer covers the space between the source and drain.

[0071] In summary, the gateless organic thin-film transistor controlled by the piezoelectric electret fabricated in this embodiment can be used as an active flexible tactile sensing element in the field of human-computer direct interaction in low-power organic electronic integrated devices.

[0072] Example 3: The piezoelectric electret-controlled gateless enhancement organic thin-film transistor was fabricated using the following method.

[0073] S101, Commercially available polypropylene film.

[0074] S102. Place the purchased polypropylene film into an autoclave. At room temperature, purge nitrogen into the sealed chamber of the autoclave. When the pressure in the sealed chamber reaches 3.5 MPa, turn off the gas source and stop purging nitrogen into the sealed chamber. After standing for 8 hours, heat the autoclave to 170°C and hold for 5 hours. During the holding period, maintain the pressure in the sealed chamber of the autoclave at around 5 MPa. Finally, quickly release the nitrogen from the autoclave within 5 seconds to obtain a porous polypropylene film. Place the porous polypropylene film under a corona polarization device with a corona voltage of +28 kV, a distance of 4.5 cm from the porous polypropylene film to the corona needle tip, and a polarization time of 5 minutes. After corona polarization treatment, a porous polypropylene piezoelectric electret film is obtained.

[0075] S103. A 40 nm thick pentacene semiconductor layer is deposited on the surface of the porous polypropylene piezoelectric electret film obtained in step S102.

[0076] S104. Deposit 60nm thick, spaced-apart source and drain electrodes on an organic semiconductor layer using a photomask to form a channel with a length of 20μm and a width of 100μm. Optionally, the source and drain electrodes are made of gold.

[0077] S105. A 150 nm thick tetradecane encapsulation layer is deposited on the source and drain, and the source and drain are led out using wires to complete the piezoelectric electret-controlled enhancement-mode gateless organic thin-film transistor; wherein the encapsulation layer covers at least part of the organic semiconductor layer, and the encapsulation layer covers the space between the source and drain.

[0078] Please see Figure 3 (a)~ Figure 3 As shown in (d), Figure 3 (a) is a schematic diagram of a commercially available polypropylene film provided in an embodiment of the present invention. Figure 3 (b) is a schematic diagram of another structure of the commercially available polypropylene film provided in an embodiment of the present invention. Figure 3 (c) is a schematic diagram of a porous polypropylene film after thermal expansion provided in an embodiment of the present invention. Figure 3 (d) is another structural schematic diagram of the porous polypropylene film after thermal expansion provided in the embodiment of the present invention; as an optional comparative example 1, a 40 nm thick pentacene semiconductor layer is directly thermally deposited on the surface of a commercially available polypropylene film, and a 60 nm thick gold source and drain electrode is deposited on the pentacene semiconductor layer through a mask, forming a channel with a length of 20 μm and a channel width of 100 μm; a 150 nm thick tetratetradecane encapsulation layer is thermally deposited on the source and drain electrodes; finally, the source and drain electrodes are led out with wires to obtain a gateless organic thin film transistor based on a polypropylene film.

[0079] The piezoelectric electret-controlled enhanced gateless organic thin-film transistor obtained in Example 3 is compared with a gateless organic thin-film transistor formed directly using commercially available polypropylene film. Please refer to [link to example]. Figure 3 (a)~ Figure 3 As shown in (d), the initial commercially available polypropylene film has a thickness of 25 μm, a dense and non-porous surface, and internal polypropylene sheets and flat slit-type air channels are stacked layer by layer. The pores are closed cavities, and the pores are independent and non-interconnected. After thermal expansion, the internal pore size of the polypropylene piezoelectric electret film is significantly increased, with a pore length of 1 μm to 4 μm and a height of 0.5 μm to 2 μm, and the film thickness increases to 53 μm. However, the degree of thermal expansion in Example 3 did not destroy the polypropylene sheet structure. The film surface is still dense and non-porous, the pores are still closed cavities, and the pores remain independent and non-interconnected.

[0080] Please see Figure 4 As shown, Figure 4 This is a schematic diagram illustrating the relationship between the piezoelectric coefficients of commercially available polypropylene film and polypropylene piezoelectric electret film provided in this embodiment of the invention. Figure 4 It can be seen that the initial commercially purchased polypropylene film d 33 The value is very low, only 2.27 pmV -1 ; while the polypropylene piezoelectric electret film, after undergoing thermal expansion and corona polarization treatment, d 33 The value is 238pmV -1 It exhibits a strong piezoelectric effect comparable to that of ceramic materials.

[0081] Please see Figure 5 As shown, Figure 5 This is a SEM schematic diagram of an organic semiconductor provided in an embodiment of the present invention. Figure 5 As can be seen, a large area of ​​dense pentacene semiconductor film was deposited on the surface of polypropylene piezoelectric electret film through thermal evaporation process, and the pentacene particles were uniformly distributed in size.

[0082] Please see Figure 6 As shown, Figure 6 This is an optical microscopic schematic diagram of a channel provided in an embodiment of the present invention, consisting of... Figure 6 It can be seen that the channel formed by the source and drain electrodes has a length of 20 μm and a width of 100 μm.

[0083] Example 4: The piezoelectric electret-controlled gateless enhancement organic thin-film transistor was fabricated using the following method.

[0084] S101, Commercially available polypropylene film.

[0085] S102. Place the purchased polypropylene film into an autoclave. At room temperature, purge nitrogen into the sealed chamber of the autoclave. When the pressure in the sealed chamber reaches 3.5 MPa, turn off the gas source and stop purging nitrogen into the sealed chamber. After standing for 8 hours, heat the autoclave to 170°C and hold for 5 hours. During the holding period, maintain the pressure in the sealed chamber of the autoclave at around 5 MPa. Finally, quickly release the nitrogen from the autoclave within 5 seconds to obtain a porous polypropylene film. Place the porous polypropylene film under a corona polarization device with a corona voltage of +28 kV, a distance of 4.5 cm from the porous polypropylene film to the corona needle tip, and a polarization time of 5 minutes. After corona polarization treatment, a porous polypropylene piezoelectric electret film is obtained.

[0086] S103. A 40 nm thick pentacene semiconductor layer is deposited on the surface of the porous polypropylene piezoelectric electret film obtained in step S102.

[0087] S104. Deposit 60nm thick, spaced-apart source and drain electrodes on an organic semiconductor layer using a photomask to form a channel with a length of 20μm and a width of 100μm. Optionally, the source and drain electrodes are made of gold.

[0088] S105. A 150 nm thick tetradecane encapsulation layer is deposited on the source and drain, and the source and drain are led out using wires to complete the piezoelectric electret-controlled enhancement-mode gateless organic thin-film transistor; wherein the encapsulation layer covers at least part of the organic semiconductor layer, and the encapsulation layer covers the space between the source and drain.

[0089] In summary, the gateless organic thin-film transistor controlled by the piezoelectric electret fabricated in this embodiment can be used as an active flexible tactile sensing element in the field of human-computer direct interaction in low-power organic electronic integrated devices.

[0090] Example 5: The piezoelectric electret-controlled gateless enhancement organic thin-film transistor was fabricated using the following method.

[0091] S101, Commercially available polypropylene film.

[0092] S102. Place the purchased polypropylene film into an autoclave. At room temperature, purge nitrogen into the sealed chamber of the autoclave. When the pressure in the sealed chamber reaches 5 MPa, shut off the gas source and stop purging nitrogen into the sealed chamber. After standing for 8 hours, heat the autoclave to 200℃ and hold for 0.5 hours. During the holding period, maintain the pressure in the sealed chamber of the autoclave at approximately 7.5 MPa. Finally, rapidly release the nitrogen from the autoclave within 10 seconds to obtain a porous polypropylene film. Place the porous polypropylene film under a corona polarization device with a corona voltage of +30 kV, a distance of 5 cm from the porous polypropylene film to the corona needle tip, and a polarization time of 1 minute. After corona polarization treatment, a porous polypropylene piezoelectric electret film is obtained.

[0093] S103. A 20 nm thick pentacene semiconductor layer is deposited on the surface of the porous polypropylene piezoelectric electret film obtained in step S102.

[0094] S104. Deposit 20nm thick, spaced-apart source and drain electrodes on an organic semiconductor layer using a photomask to form a channel with a length of 10μm and a width of 100μm. Optionally, the source and drain electrodes are made of gold.

[0095] S105. A 100 nm thick tetradecane encapsulation layer is deposited on the source and drain, and the source and drain are led out by wires to complete the piezoelectric electret-controlled enhancement-mode gateless organic thin-film transistor; wherein the encapsulation layer covers at least part of the organic semiconductor layer, and the encapsulation layer covers the space between the source and drain.

[0096] In summary, the gateless organic thin-film transistor controlled by the piezoelectric electret fabricated in this embodiment can be used as an active flexible tactile sensing element in the field of human-computer direct interaction in low-power organic electronic integrated devices.

[0097] Example 6: The fabrication of a gateless enhancement organic thin-film transistor regulated by piezoelectric electret was achieved by the following method.

[0098] S101, Commercially available polypropylene film.

[0099] S102. Place the purchased polypropylene film into an autoclave. At room temperature, purge nitrogen into the sealed chamber of the autoclave. When the pressure in the sealed chamber reaches 3.5 MPa, turn off the gas source and stop purging nitrogen into the sealed chamber. After standing for 8 hours, heat the autoclave to 170°C and hold for 5 hours. During the holding period, maintain the pressure in the sealed chamber of the autoclave at around 5 MPa. Finally, quickly release the nitrogen from the autoclave within 5 seconds to obtain a porous polypropylene film. Place the porous polypropylene film under a corona polarization device with a corona voltage of -28 kV, a distance of 4.5 cm from the porous polypropylene film to the corona needle tip, and a polarization time of 5 minutes. After corona polarization treatment, a porous polypropylene piezoelectric electret film is obtained.

[0100] S103. A 40 nm thick pentacene semiconductor layer is deposited on the surface of the porous polypropylene piezoelectric electret film obtained in step S102.

[0101] S104. Deposit 60nm thick, spaced-apart source and drain electrodes on an organic semiconductor layer using a photomask to form a channel with a length of 20μm and a width of 100μm. Optionally, the source and drain electrodes are made of gold.

[0102] S105. A 150 nm thick tetradecane encapsulation layer is deposited on the source and drain, and the source and drain are led out using wires to complete the piezoelectric electret-controlled enhancement-mode gateless organic thin-film transistor; wherein the encapsulation layer covers at least part of the organic semiconductor layer, and the encapsulation layer covers the space between the source and drain.

[0103] In summary, the gateless organic thin-film transistor controlled by the piezoelectric electret fabricated in this embodiment can be used as an active flexible tactile sensing element in the field of human-computer direct interaction in low-power organic electronic integrated devices.

[0104] Please see Figure 7 As shown in (a) to 7(c) Figure 7 (a) is a response curve of the gateless organic thin-film transistor provided in an embodiment of the present invention to the dynamic current of a stepped mechanical signal. Figure 7 (b) is an IV output characteristic curve of the gateless organic thin-film transistor provided in the embodiment of the present invention under different pressures. Figure 7 (c) is a potential diagram of the surface of a commercially available polypropylene film in Comparative Example 1 measured by a scanning Kelvin probe microscope according to an embodiment of the present invention. The gateless organic thin-film transistor provided in this embodiment has an ohmic contact between its source / drain electrode and the pentacene semiconductor. As the pressure increases, the source / drain current I of the organic thin-film transistor in Comparative Example 1 increases. DSIt exhibits a very slight increasing trend. The surface potential of the commercially available polypropylene film, measured by scanning Kelvin probe microscopy, is approximately +2V. This indicates that the surface of the commercially available polypropylene film used in the organic thin-film transistor of Comparative Example 1 carries a trace amount of positive charge, thereby inducing a trace amount of negative charge on the pentacene semiconductor surface, forming an extremely thin hole depletion layer. Please continue to see Figure 4, where the commercially available polypropylene film d... 33 The value is 2.27pmV -1 It still exhibits weak piezoelectric properties; when the organic thin-film transistor is subjected to compressive stress, the air pores inside the commercially available polypropylene film are compressed, the dipole moment decreases, and the induced negative charge on the surface of the pentene semiconductor also decreases accordingly, resulting in a thinner hole depletion layer. The channel current increases with increasing stress. Thus, the gateless organic thin-film transistor based on the commercially available polypropylene film obtained in Comparative Example 1 essentially operates in enhancement mode; however, due to the d-... 33 When the piezoelectric value is too small and the amount of charge on the surface of the thin film is extremely limited, the weak piezoelectric potential has a negligible effect on the regulation of channel carrier electric transport.

[0105] Please see Figure 8 (a)~ Figure 8 As shown in (c) Figure 8 (a) is a dynamic current response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to a stepped mechanical signal. Figure 8 (b) is a dynamic current response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to a periodic mechanical signal. Figure 8 (c) is a graph showing the IV output characteristics of the gateless organic thin-film transistor provided in this embodiment of the invention under different pressures. As the pressure increases, I... DS With synchronous increase, the gateless organic thin-film transistor exhibits a significant current response, operating in enhancement mode. Given the +28kV positive high voltage applied to the corona needle, corona discharge generates positive ions in the air, which are then injected into the material surface under the drive of the electric field. This results in a large amount of positive charge on the side of the porous polypropylene piezoelectric electret film closest to the corona needle, inducing a large amount of negative charge on the pentacene semiconductor surface, forming a hole depletion layer. When the device is subjected to compressive stress, the air pores inside the polypropylene piezoelectric electret film are compressed, the dipole moment decreases, and the induced negative charge on the pentacene semiconductor surface also decreases accordingly. The thickness of the hole depletion layer thins, and the channel current increases with increasing stress. At the instant compressive stress is applied to the device, I... DS The speed increases rapidly, and the device response time is 63ms; during the 10s duration of stress maintenance, I... DS The numerical value remains unchanged, giving the organic thin-film transistor provided in this embodiment good stability; when the compressive stress on the device is removed, I DSThe rapid decrease to the initial value indicates that the mechanical control is reversible.

[0106] Please see Figure 9 As shown in (a) to 9(d) Figure 9 (a) is a schematic diagram of a gateless depletion type OTFT regulated by a polypropylene piezoelectric electret thin film according to an embodiment of the present invention. Figure 9 (b) is a dynamic current response curve of the gateless organic thin-film transistor provided in the embodiment of the present invention to a stepped mechanical signal stimulus. Figure 9 (c) is a schematic diagram of the IV output characteristic curves of the gateless organic thin-film transistor under different pressures provided in the embodiment of the present invention. Figure 9 (d) is a schematic diagram of the dynamic current response curve during the palm opening and closing test provided in an embodiment of the present invention. The gateless thin-film transistor includes, from bottom to top, a porous polypropylene piezoelectric electret film (optionally, ...). Figure 9 (a) The upper surface shown is the surface away from the corona needle during polarization treatment), pentacene semiconductor layer, source and drain electrodes, tetratetradecane encapsulation layer; The difference between the device manufacturing method of Embodiment 4 and Embodiment 3 is that the device of Embodiment 4 is constructed on the surface of the porous polypropylene piezoelectric electret film away from the corona needle, and as the pressure increases, I DS The current response decreases synchronously and is relatively significant, indicating that the device operates in depletion mode. In the device manufacturing method of Example 4, a +28kV positive high voltage is applied to the corona needle. The polypropylene piezoelectric electret has bipolar characteristics, causing the surface of the porous polypropylene piezoelectric electret film away from the corona needle to carry a large number of negative charges, thereby inducing hole carriers on the pentacene semiconductor surface to form a conductive channel. When the device is subjected to compressive stress, the air pores inside the polypropylene piezoelectric electret film are compressed, the dipole moment decreases, and the number of induced holes on the pentacene semiconductor surface also decreases accordingly. The channel current decreases with increasing stress. Figure 9 As shown in (d), when the device is attached to the knuckle joint, it exhibits a rapid, reversible, and stable electrical response to repeated opening and closing movements of the palm, fist clenching force, and fist holding time. This indicates that the device possesses excellent flexibility, fully meeting the flexibility requirements of wearable devices, electronic skin, and other artificial intelligence fields. The passive flexible organic thin-film transistor based on piezoelectric electret control obtained in this embodiment can quickly sense stress magnitude and stress dwell time without a gate. Integrating it as a tactile sensor component into flexible electronic devices not only significantly reduces product power consumption and improves reliability and durability but also enables a direct, proactive human-machine interaction mode.

[0107] Please refer to Figure 10 As shown, Figure 10(a) is a schematic diagram of the dynamic current response curve of the piezoelectric electret-controlled gateless enhancement-mode OTFT stress sensor device to a stepped mechanical signal provided in an embodiment of the present invention. Figure 10 (b) is a schematic diagram of the dynamic current response curve of the piezoelectric electret-controlled gateless enhancement-mode OTFT stress sensor device provided in this embodiment of the invention to a periodic mechanical signal. The difference between the device manufacturing method of Embodiment Six and Embodiment Four is that the corona polarization direction of the porous polypropylene film is reversed: the porous polypropylene piezoelectric electret film used in Embodiment Four is obtained by +28kV corona polarization; while the porous polypropylene piezoelectric electret film used in Embodiment Six is ​​obtained by -28kV corona polarization, thus carrying a large amount of positive charge on the surface away from the corona needle. Figure 10 From (a), we can see that as the pressure increases, I DS The current response increases synchronously and is significant, indicating that the device operates in an enhanced mode. As shown in Figure 10(b), the device responds rapidly and accurately to stress application, stress holding, and stress release, and the mechanical control is reversible. The results further confirm the flexibility in the design and manufacture of the device of this invention, namely, the device's operating mode can be quickly switched by adjusting the positive and negative charges bound on the surface of the piezoelectric electret film in real time according to the specific application scenario requirements.

[0108] In summary, based on the positive and negative charges bound to the surface of the piezoelectric electret film, the operating mode of the piezoelectric electret-controlled OTFT device can be designed as either enhancement-mode or depletion-mode. This invention's piezoelectric electret-controlled OTFT tactile sensor eliminates the need for a gate, significantly reducing power consumption in flexible electronic integrated devices such as electronic skin and improving the overall reliability and durability of flexible electronic devices. More importantly, by coupling the piezoelectric effect, field effect, and semiconductor properties, it integrates the advantages of passive piezoelectric tactile sensing with transistor signal amplification, achieving a direct, active human-machine interaction mode.

[0109] Based on the same inventive concept, please continue to see Figure 2 As shown, the present invention also provides a gateless organic thin-film transistor controlled by a piezoelectric electret, which is fabricated using the piezoelectric electret controlled gateless organic thin-film transistor fabrication method provided in the above embodiments of the present invention.

[0110] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0111] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0112] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a gateless organic thin-film transistor controlled by a piezoelectric electret, characterized in that, The application relates to a method for manufacturing a piezoelectric electret thin-film transistor. The method comprises the following steps: acquiring a polypropylene film; processing the polypropylene film by adopting thermal expansion, and performing corona polarization treatment on the polypropylene film after the thermal expansion treatment, so as to obtain a porous polypropylene piezoelectric electret thin film; evaporating a pentacene semiconductor layer on the surface of the porous polypropylene piezoelectric electret thin film, so as to form an organic semiconductor layer; depositing a source electrode and a drain electrode which are arranged at intervals on the organic semiconductor layer through a mask plate; 2. The piezoelectret-gated organic thin film transistor fabrication method according to claim 1, wherein evaporating an encapsulation layer on the surface of at least part of the source electrode, the surface of at least part of the drain electrode, the surface of at least part of the organic semiconductor layer, and between the source electrode and the drain electrode, and leading out the source electrode and the drain electrode by adopting a wire. The processing of the polypropylene film by adopting thermal expansion comprises the following steps: placing the polypropylene film in an autoclave; at room temperature, flushing nitrogen into the closed cavity of the autoclave, and standing for 0h-8h; wherein the gas pressure value of the flushed nitrogen is 1MPa-5MPa; heating the autoclave to 70 DEG C-200 DEG C, and keeping the temperature for 0.5h-6h; wherein the gas pressure value in the closed cavity of the autoclave is kept at 1.2MPa-7.5MPa during the temperature keeping process; 3. The piezoelectret-gated organic thin film transistor fabrication method according to claim 1, wherein quickly releasing the nitrogen in the closed cavity of the autoclave within 1s-10s.

4. The piezoelectret-gated organic thin film transistor according to claim 3, wherein The thickness of the polypropylene film after the thermal expansion treatment is 0.5-3 times the thickness of the polypropylene film; wherein the thickness of the polypropylene film after the thermal expansion treatment and the thickness of the polypropylene film are both the thickness along a first direction.

5. The piezoelectret-gated organic thin film transistor fabrication method according to claim 1, wherein The polypropylene film after the thermal expansion treatment comprises a plurality of holes, the length of the holes is 1um-100um, the height of the holes is 0.1um-10um, and adjacent holes are independently non-through; wherein the length of the holes is the size along a second direction, the height of the holes is the size along the first direction, and the first direction intersects with the second direction. The corona polarization treatment of the polypropylene film after the thermal expansion treatment comprises the following steps:

6. The piezoelectret-gated organic thin film transistor fabrication method of claim 1, wherein, The piezoelectric coefficient value d 33 is 200 pmV -1 ~ 350 pmV -1 .

7. The piezoelectret-gated organic thin-film transistor fabrication method of claim 1, wherein the piezoelectret-gated organic thin-film transistor fabrication method is characterized by: placing the polypropylene film after the thermal expansion treatment under the corona needle tip of a corona polarization device, and the distance between the polypropylene film after the thermal expansion treatment and the corona needle tip is 1cm-5cm, and the polarization time is 1min-10min; wherein the corona voltage is +15kV-+30kV or -30kV--15kV.

8. The piezoelectret-gated organic thin film transistor fabrication method of claim 1, wherein, The thickness of the organic semiconductor along the first direction is 20nm-100nm.

9. The piezoelectret-gated organic thin-film transistor fabrication method of claim 1, wherein, The thickness of the source electrode and the drain electrode is both 20nm-100nm; the length of the channel formed between the source electrode and the drain electrode is 10um-100um, and the width of the channel is 50um-1000um.

10. A piezoelectret-gated organic thin-film transistor, characterized by, The thickness of the encapsulation layer along the first direction is 100nm-500nm, and the material of the encapsulation layer is tetracontane. The piezoelectric electret thin-film transistor is manufactured by using the method for manufacturing a piezoelectric electret thin-film transistor.

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