An array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes, its fabrication method and application.

Abstract

This invention provides an array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes, its fabrication method, and its application, relating to the field of electromagnetic functional devices. It includes an organic thin-film transistor based on pentacene, with a PEDOT:PSS transparent electrode layer disposed on the organic thin-film transistor. This invention utilizes the aforementioned array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes, its fabrication method, and its application, optimizing the array structure formed by combining modified PEDOT:PSS transparent electrodes with organic thin-film transistors for use as a terahertz-band liquid crystal phased array electrode layer, ensuring high terahertz transmittance.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic functional devices, and in particular to an array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes, its fabrication method, and its application. Background Technology

[0002] As an important branch of optical phased array technology, liquid crystal phased array technology uses electro-optic materials with electrically controlled birefringence to fabricate adjacent phased array units. By applying different voltages to the two ends of each liquid crystal phased array unit, a coherent laser beam superposition effect is generated, causing the laser beams to have different time delays along their propagation paths, thereby achieving precise electrically controlled scanning of the beam. Designing the structure and fabricating the device of the driving unit electrode of the liquid crystal phased array unit is crucial for exploring the design and fabrication of key components for phased array electro-drive. In the visible light field, ITO (indium tin oxide) is currently the most widely used transparent conductive material in liquid crystal phase arrays and almost all flat panel displays (LCD, OLED) and touch screens. However, the transmittance of ITO in the terahertz band is less than 10%, which cannot be used for terahertz band modulation. Therefore, materials with high transmittance in the terahertz band are needed as new transparent electrodes. PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)) is used as the electrode material, which has a high transmittance of more than 80% in the terahertz band. Patterned transparent electrodes made of PEDOT:PSS can be used for terahertz band modulation. In the driving of phased arrays, thin-film transistors are currently the mainstream approach. Therefore, it is necessary to design a suitable organic thin-film transistor (OTFT) and combine it with transparent electrodes made of PEDOT:PSS to form an array as the electrode layer of the phased array. Then, it is connected to the wave control system through FPC (flexible printed circuit board) cables. The organic thin-film transistor can then independently and precisely control each PEDOT:PSS transparent electrode pixel, thereby enabling visible light liquid crystal modulation technology to be applied to the terahertz band. Summary of the Invention

[0003] The purpose of this invention is to provide an array formed by combining organic thin-film transistors and PEDOT:PSS transparent electrodes, its preparation method, and its application. The array structure formed by combining the optimized and modified PEDOT:PSS transparent electrodes and organic thin-film transistors is used in the terahertz liquid crystal phased array electrode layer to ensure high terahertz transmittance.

[0004] To achieve the above objectives, the present invention provides an array of organic thin-film transistors and PEDOT:PSS transparent electrodes, comprising an organic thin-film transistor based on pentacene and a PEDOT:PSS transparent electrode layer disposed on the organic thin-film transistor.

[0005] Preferably, the PEDOT:PSS transparent electrode layer is disposed between the drain and the dielectric layer on the organic thin-film transistor.

[0006] Preferably, the organic thin-film transistor further includes a transparent substrate, a gate disposed on the substrate, a dielectric layer disposed on the gate and the transparent substrate, and a source and a drain disposed above the dielectric layer, wherein a conductive channel portion between the source and the drain is provided with pentacene.

[0007] A method for fabricating an array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes includes the following steps: A gate layer is formed on a transparent substrate; A dielectric layer is formed on the gate layer and the transparent substrate; A PEDOT:PSS transparent electrode layer is formed on the dielectric layer; Active and drain electrodes are also formed on the dielectric layer; A portion of the drain electrode is also embedded in the PEDOT:PSS transparent electrode layer; An organic semiconductor layer is formed between the source and drain.

[0008] Preferably, the PEDOT:PSS solution is used to prepare a PEDOT:PSS transparent electrode layer, wherein the preparation of the PEDOT:PSS solution includes the following steps: Doping: PEDOT:PSS solution was doped with dimethyl sulfoxide (DMSO) solution and then filtered; Prepare a polyvinyl alcohol (PVA) solution: Weigh out the prepared PVA solid and deionized water while stirring. Secondary doping: The prepared PVA solution is subjected to secondary doping with the PEDOT:PSS solution doped with DMSO to obtain the secondary doped PEDOT:PSS solution.

[0009] Preferably, the volume ratio of PEDOT:PSS solution to dimethyl sulfoxide (DMSO) solution is 100:15-100:20; The mass fraction of the PVA solution is 8%-10%; The volume ratio of DMSO-doped PEDOT:PSS solution to PVA solution is 8:1-10:1.

[0010] Preferably, the fabrication of the PEDOT:PSS transparent electrode layer includes: spin-coating a PEDOT:PSS solution onto the surface of the photoresist layer, heating it, and finally removing the photoresist.

[0011] Preferably, the PEDOT:PSS solution is spin-coated onto the surface with photoresist and then heated, wherein... Set the speed to 3000-3500 rpm and the time to 40-50 seconds; The heating temperature is 90-100℃, and the heating time is 10-15 minutes.

[0012] Application of an array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes in the fabrication of terahertz phased array electrode layers.

[0013] Therefore, the present invention employs the above-mentioned array formed by combining an organic thin-film transistor with a PEDOT:PSS transparent electrode, its fabrication method, and its application, with the following technical effects: Using PEDOT:PSS as the electrode material ensures a transmittance of over 80% in the terahertz band, breaking through the transmittance limitations of traditional transparent electrode ITO.

[0014] A two-dimensional array pixel electrode driving scheme based on organic thin film transistors is proposed and applied to terahertz liquid crystal phased arrays, which helps to realize array-based modulation and coding of high-frequency terahertz wavefronts.

[0015] Using pentacene as the organic semiconductor layer has the advantages of high carrier mobility, good crystallinity, suitability for flexible electronics, and convenient vapor deposition. Attached Figure Description

[0016] Figure 1 This is a diagram of the device structure. Figure 2 This is the pattern of the gate layer on the metal mask in Example 1 of the present invention; Figure 3 The pattern of the PEDOT:PSS transparent electrode layer on the photomask in Example 1 of this invention; Figure 4 The pattern of the source and drain layers on the metal mask in Example 1 of this invention (channel spacing is 100). ); Figure 5 This is the pattern of the array circuit in Example 1 of the present invention; Figure 6 The 8×8 organic thin-film transistor array prepared in Example 1 of this invention; Figure 7 The structure of the 8×8 organic thin-film transistor array prepared in Example 1 of this invention is shown under a microscope; Figure 8 The output characteristic curve of the organic thin-film transistor in Example 1 of this invention; Figure 9 The image shows the transfer characteristic curve of the organic thin-film transistor in Example 1 of this invention. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0019] like Figure 1 As shown, an array of organic thin-film transistors (TFTs) combined with PEDOT:PSS transparent electrodes includes a pentacene-based TFT and a PEDOT:PSS transparent electrode layer disposed on the TFT. The PEDOT:PSS transparent electrode layer is disposed between the drain and a dielectric layer on the TFT. The TFT also includes a transparent quartz substrate, a gate disposed on the substrate, a dielectric layer disposed on the gate and the transparent substrate, and a source and a drain disposed above the dielectric layer. A conductive channel portion between the source and the drain is provided with pentacene.

[0020] Example 1 A method for fabricating an array of organic thin-film transistors combined with PEDOT:PSS transparent electrodes includes the following steps: S1. Fabrication of the gate layer: S11. Cleaning the substrate: Clean the transparent quartz substrate with an ultrasonic cleaner (using deionized water, ethanol, and isopropanol in sequence, ultrasonically vibrating for 10 minutes each), and then dry it with nitrogen. S12, Gold Plating: A metal mask is placed on a quartz plate, and a magnetron sputtering apparatus is used for plating. The pattern on the metal mask is as follows: Figure 2 As shown; S2. Fabrication of the dielectric layer: S21. Spin coat the PI (polyimide) solution onto the substrate with the completed gate fabrication using a spin coater, with the spin speed set to 1500 rpm and the time to 40 seconds. S22. Place the quartz plate from S21 into an oven and heat at 100°C for 30 minutes, then maintain the temperature at 250°C for 1 hour. Preparation of S3, PEDOT:PSS solution: S31. Doping: PEDOT:PSS solution and DMSO (dimethyl sulfoxide) solution are mixed at a volume ratio of 100:15 and then filtered. PEDOT:PSS accounts for a large proportion. S32. Prepare PVA (polyvinyl alcohol) solution: Weigh PVA solid and deionized water to ensure the mass fraction of the PVA solution is 8%. Set the magnetic stirrer temperature to 95℃ and stir for 30 minutes; S33, Secondary doping: The prepared PVA solution is doped with the PEDOT:PSS solution doped with DMSO in step S31 at a volume ratio of 10:1, with the PVA solution accounting for a small proportion. Fabrication of S4, PEDOT:PSS transparent electrode layer: S41, Spin coating: Use a spin coater to spin-coat photoresist onto the quartz substrate with the dielectric layer completed. The spin speed is set to 2500 rpm and the time is 40 seconds. S42, Pre-baking: Place the substrate with a layer of photoresist spin-coated onto the baking table at 100°C for 90 seconds; S43. Exposure: Place the pre-baked substrate on the photomask (with the photoresist-coated side in close contact with the mask). Set the exposure time to 20 seconds. The pattern of the photomask is as follows: Figure 3 As shown; S44. Post-baking: Place the exposed substrate onto the baking table at 100°C for 90 seconds. S45. Development: Immerse the post-baked substrate in the developing solution for 40 seconds. S46 Cleaning: Take out the substrate from S45, put it into deionized water, soak it to remove excess photoresist, and finally use nitrogen to dry the substrate. S47. Spin-coating PEDOT:PSS: Use a spin coater to spin-coat the prepared PEDOT:PSS solution onto the quartz substrate with the photoresist side. The spin speed is set to 3000 rpm and the time is 40 seconds. S48. Heating: Place the substrate from S47 onto the drying rack at 90°C for 10 minutes. S49. Removing photoresist: Immerse the substrate in ethanol for at least 10 minutes. Then, use a low-power ultrasonic cleaner to repeatedly agitate the beaker containing ethanol and substrate for 8-10 seconds each time, until the pattern is clear and distinct. Remove the substrate and dry it with nitrogen gas. S5, Fabrication of source and drain layers: Gold plating: A metal mask is placed on a quartz plate, and a magnetron sputtering device is used for coating. The pattern on the metal mask is as follows: Figure 4 As shown, the completed overall array circuit pattern is as follows: Figure 5 As shown; S6. Fabrication of the organic semiconductor layer: Using a vacuum evaporation machine, a quartz wafer with fabricated source and drain electrodes is vacuum-deposited to deposit pentacene onto the conductive channel between the source and drain electrodes, resulting in a device such as... Figure 6 As shown, from Figure 7 The device structure can be seen under an electron microscope, and the cross-comb structure formed by the source and drain can be clearly seen.

[0021] The electrical characteristics of the fabricated organic thin-film transistor device were characterized using a KEYSIGHT B1500A semiconductor parameter analyzer. During testing, the three probes of the probe station were connected to the source, drain, and gate, respectively. The output characteristic curve and transfer characteristic curve were measured using the semiconductor analyzer. The output characteristic curve is shown below. Figure 8 As shown, the transfer characteristic curve is as follows: Figure 9 As shown.

[0022] Therefore, the present invention adopts the above-mentioned array formed by combining organic thin film transistors and PEDOT:PSS transparent electrodes, the preparation method, and the application in terahertz control devices, and optimizes the array structure formed by combining modified PEDOT:PSS transparent electrodes and organic thin film transistors for use in terahertz liquid crystal phased array electrode layers to ensure high terahertz transmittance.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An array of organic thin film transistors combined with PEDOT:PSS transparent electrodes, characterized in that, Including an organic thin-film transistor based on pentacene, and a PEDOT:PSS transparent electrode layer disposed on the organic thin-film transistor.

2. The array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 1, characterized in that, PEDOT: The PSS transparent electrode layer is disposed between the drain and the dielectric layer on the organic thin-film transistor.

3. The array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 1, characterized in that, The organic thin-film transistor also includes a transparent substrate, a gate disposed on the substrate, a dielectric layer disposed on the gate and the transparent substrate, and a source and a drain disposed above the dielectric layer, wherein a conductive channel portion between the source and the drain is provided with pentacene.

4. The method for fabricating an array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 1, characterized in that, Includes the following steps: A gate layer is formed on a transparent substrate; A dielectric layer is formed on the gate layer and the transparent substrate; A PEDOT:PSS transparent electrode layer is formed on the dielectric layer; Active and drain electrodes are also formed on the dielectric layer; A portion of the drain electrode is also embedded in the PEDOT:PSS transparent electrode layer; An organic semiconductor layer is formed between the source and drain.

5. The method for fabricating an array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 4, characterized in that, The PEDOT:PSS solution is used to prepare a transparent PEDOT:PSS electrode layer, and the preparation of the PEDOT:PSS solution includes the following steps: Doping: PEDOT:PSS solution was doped with dimethyl sulfoxide (DMSO) solution and then filtered; Prepare a polyvinyl alcohol (PVA) solution: Weigh out the prepared PVA solid and deionized water while stirring. Secondary doping: The prepared PVA solution is subjected to secondary doping with the PEDOT:PSS solution doped with DMSO to obtain the secondary doped PEDOT:PSS solution.

6. The method for fabricating an array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 5, characterized in that, The volume ratio of PEDOT:PSS solution to dimethyl sulfoxide (DMSO) solution is (100~15):(100~20). The mass fraction of the PVA solution is 8%-10%; The volume ratio of DMSO-doped PEDOT:PSS solution to PVA solution is (8~1):(10~1).

7. The method for fabricating an array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 4, characterized in that, The fabrication of the PEDOT:PSS transparent electrode layer includes: spin-coating a PEDOT:PSS solution onto the surface of the photoresist layer, heating it, and finally removing the photoresist.

8. The method for fabricating an array of organic thin-film transistors and PEDOT:PSS transparent electrodes according to claim 4, characterized in that, The PEDOT:PSS solution was spin-coated onto the surface with photoresist and then heated. Set the speed to 3000-3500 rpm and the time to 40-50 seconds; The heating temperature is 90-100℃, and the heating time is 10-15 minutes.

9. The application of the array of organic thin-film transistors and PEDOT:PSS transparent electrodes as described in claim 1 in the fabrication of terahertz phased array electrode layers.

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