A method for high-precision patterning of polymer semiconductors and its application in the fabrication of optoelectronic devices

Abstract

The application provides a high-precision polymer patterning technology with universality and its application in photoelectric device manufacturing, which is characterized by patterning a polymer semiconductor layer on a substrate by using 172nm excimer ultraviolet light. ‑8 A is reduced to 10 ‑10 A, and finally realizes the manufacturing of high-quality polymer thin film transistors; meanwhile, the technology can also be applied to other photoelectric devices, so as to realize low-energy-consumption and high-quality photoelectric devices and promote the application of polymer semiconductor materials in the fields of information technology and biomedicine.

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic materials and devices, specifically relating to a universally applicable high-precision polymer patterning technology and its application in the fabrication of optoelectronic devices. Background Technology

[0002] The discovery of conductive polymers in the 1970s changed people's traditional understanding of polymers as insulating materials and ushered in a new era of plastic-based electronics (Heeger A J. Angew Chem Int Ed 2001, 40, 2591-2611). Currently, polymer semiconductor materials have become a cutting-edge research direction in materials science due to the designability of their structure and optoelectronic properties. With the continuous development of material systems, organic circuits constructed from them have shown great application potential in fields such as flexible displays, bionic electronic skin, bionic visual systems, and bionic nervous systems. (a) Liu J.;Wang JC;Zhang Z.T.;Nature Communications 2020,11,3362.(b) Ge F.;Liu Z.;Lee SB;et al.AcsApplied Materials&Interfaces 2018,10,21510.(c) Fang Y.;Wu XM;Lan SQ;et al.Acs Applied Materials&Interfaces 2018,10,30587.(d) Wang HL;,Zhao Q.;Ni Z.J.;et al.Advanced Materials (2018,30,1803961.) is gradually becoming one of the important functional systems for building flexible electronic devices, bringing new opportunities for the development of electronics.

[0003] Currently, the optoelectronic device industry based on polymer semiconductor materials still faces many challenges, among which the core issues include the precision fabrication technology of micro and nano structures. Consequently, a large amount of research work has been invested in this area, actively developing efficient and universal polymer patterning integration technology to achieve low-energy, high-quality optoelectronic devices and promote the application of polymer semiconductor materials in information technology, biomedicine and other fields. In recent years, patterning technologies developed include photolithography, inkjet printing, mold induction, and wettability control assembly. ((a) Tang CB; Lennon EM; Fredrickson GH; et al. Science 2008, 322, 429-432. (b) Kuang MX; Wang LB; Song YL; Advanced Materials 2014, 26, 6950-6958. (c) Park S.; Yang G.; Madduri N.; et al. Advanced Materials 2014, 26, 2782-2787. (d) Feng JG; Wen W.; Wei X.; et al. (al.Advanced Materials 2019, 31, 1807880.) Among these technologies, photolithography and printing are relatively mature. Although photolithography has the advantage of high precision, the patterning process requires coating a layer of liquid photoresist. The biggest problem is that the removal of the photoresist can cause irreparable damage to the polymer semiconductor. Inkjet printing technology not only has high requirements for ink, but its precision can only reach tens of micrometers ((a)Molina-Lopez F.;Gao TZ;Kraft U.;et al.Nature Communications 2019, 10, 2676.(b)Conti S.;Pimpolari L.;Calabrese G.;et al.Nature Communications 2020, 11, 3566). Therefore, combining the current advantages of patterning technology, it is imperative to develop a universal, non-destructive, high-precision patterning technology. Summary of the Invention

[0004] The purpose of this invention is to provide a universally applicable high-precision polymer semiconductor patterning technology.

[0005] The polymer semiconductor patterning technology provided by this invention is: applying 172nm excimer ultraviolet lithography to pattern a polymer semiconductor layer located on a substrate;

[0006] The substrate may be a PET, PEN, or PI substrate;

[0007] The polymer semiconductor layer is made of a polymer semiconductor material;

[0008] The polymer semiconductor material is selected from PDVT-10 (poly-3,6-dithiophene-2-yl-2,5-bis(2-decyltetradecyl)-pyrrolo[3,4-c]pyrrolo-1,4-dione-alt-thiophenevinylthiophene-2,5-diyl), IDT-BT (polyindothiophene-benzothiadiazole), N2200 (poly(2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline 1,3,6,8(2H,7)-tetraone-4,9-diyl)([2,2']dithio-5,5'-diyl)), Poly-TPD (poly[N,N'-bis(4 (-Butylphenyl)-N,N'-bis(phenyl)-benzidine]), PVK (poly(9-vinylcarbazole)), F8BT (poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazole-4,7-diyl)]), F8T2 (poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-2,2'-bithiophene-5,5'-diyl]), MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]); specifically, it can be PDVT-10, F8BT or Poly-TPD;

[0009] The thickness of the polymer semiconductor layer can be 20–40 nm; specifically, it can be 20–30 nm.

[0010] The polymer semiconductor material is soluble in at least one of toluene, chlorobenzene, chloroform, and xylene; the concentration of the polymer semiconductor material can be 5–15 mg / mL; specifically, it can be 10 mg / mL.

[0011] In the 172nm excimer ultraviolet lithography patterning operation, the 172nm excimer ultraviolet photon energy is as high as 7.2 eV, which is sufficient to open most molecular bonds; the main parameter is an output intensity greater than 10 mW / cm². 2 The full width at half maximum (FWHM) is 8–10 nm, the nitrogen flow rate is 0.5–1 SCFM, and the 172 nm ultraviolet light irradiation time is 10–30 min, specifically 15–25 min.

[0012] A schematic diagram illustrating the working principle of 172nm excimer ultraviolet lithography patterning, an optical microscope image of a patterned thin film based on polymer semiconductor PDVT-C10, and a corresponding 7μm resolution tapping mode atomic force microscope height image are shown below. Figure 1 As shown.

[0013] The application of the aforementioned high-precision polymer patterning technology in the fabrication of organic optoelectronic devices also falls within the scope of protection of this invention.

[0014] The organic optoelectronic device may specifically be a polymer thin-film transistor.

[0015] The present invention also provides a method for fabricating polymer thin-film transistors based on the above-mentioned polymer semiconductor patterning technology.

[0016] The method for fabricating polymer thin-film transistors based on the above-mentioned polymer semiconductor patterning technology includes the following operations:

[0017] 1) Fabricate source and drain electrodes on the substrate;

[0018] 2) Modify the source / drain electrodes prepared in step 1) with OTS;

[0019] 3) Prepare a polymer semiconductor layer on the OTS-modified layer prepared in step 2);

[0020] 4) Patterning is performed on the polymer semiconductor layer prepared in step 3) using 172nm excimer ultraviolet light;

[0021] 5) Prepare a dielectric layer after the patterning technique in step 4);

[0022] 6) A gate electrode is fabricated on the dielectric layer prepared in step 5) to obtain a polymer thin film transistor device.

[0023] In the above method, the device has a top-gate bottom-electrode structure;

[0024] In step 1) above, the substrate can be a PET, PI, or PEN substrate;

[0025] Before use, the substrate was ultrasonically cleaned in sequence with detergent solution, deionized water, ethanol and acetone.

[0026] Both the source electrode and the drain electrode are selected from gold;

[0027] The source electrode and drain electrode are prepared by vacuum evaporation; the specific vacuum evaporation conditions are: a vacuum degree of 10... -4 ~10 -7 Pa, preferably 4 to 8 × 10 -5 Pa; more specifically 6 × 10 -6 Tor or less; evaporation rate is Preferred The thickness of the source and drain electrodes is 27–35 nm; specifically 30–35 nm.

[0028] In step 2), an OTS (octadecyltrichlorosilane) modified layer is prepared by a vapor phase modification method; specifically, a vacuum oven is used with a vacuum degree of 0.01 Pa and heating at 120°C for 3 hours.

[0029] In step 3), the method for preparing the polymer semiconductor layer is spin coating; specifically, in the spin coating, the spin coating speed is 2000-3000 rad / min, and the spin coating time is 40-60 s, preferably 2000-2500 rad / min and 40-50 s; in the spin coating, the spin coating solution used can be a 6 mg / mL PDVT-10 solution, the solvent can be o-xylene, the spin coating speed can be 3000 rad / min, the spin coating time can be 50 min, and the annealing conditions after spin coating can be 10 min at 120℃; the thickness of the polymer semiconductor layer is 20-40 nm, specifically 20-30 nm;

[0030] In step 4), 172nm excimer ultraviolet lithography patterning technology is applied to the prepared polymer semiconductor; the main parameter is an output intensity greater than 10mW / cm². 2 The full width at half maximum (FWHM) is 8–10 nm, the nitrogen flow rate is 0.5–1 SCFM, and the illumination time can be 10–30 min, preferably 15–25 min.

[0031] In step 5), the preparation method is spin coating; specifically, the PMMA molecular weight is 12-100W, the solvent can be n-butyl acetate, the solution concentration can be 50-70 mg / mL, the spin coating speed can be 2000-3000 rad / min, and the spin coating time can be 40-60 s, preferably 2500-3000 rad / min and 50-60 s; the spin coating speed can be 3000 rad / min and the spin coating time can be 50 s, and annealing is performed after spin coating, specifically 30 min at 90℃; the thickness of the dielectric layer can be 250-500 nm, specifically 400-500 nm;

[0032] In step 6), the gate electrode is made of aluminum; the gate electrode is prepared by vacuum evaporation; the specific evaporation conditions are: a vacuum degree of 10... -4 ~10 -7 Pa, preferably 4 to 8 × 10 -5 Pa; more specifically 8 × 10 -6 Tor or less; evaporation rate is Preferred

[0033] This invention discloses a universally applicable high-precision polymer patterning technique and its application in the fabrication of organic optoelectronic devices. This invention utilizes 172nm excimer ultraviolet light to achieve high-precision, non-destructive patterning of polymer semiconductors, reducing the device's off-state current from 10... -8 A decreased to 10 -10A. Ultimately, this technology enables the fabrication of high-quality polymer thin-film transistors. Furthermore, it can be applied to other optoelectronic devices, thereby achieving low-energy, high-quality optoelectronic devices and advancing the application of polymer semiconductor materials in information technology, biomedicine, and other fields. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the working principle of the 172nm excimer ultraviolet lithography patterning provided by the present invention, an optical microscope image of the patterned thin film based on the polymer semiconductor PDVT-C10, and a corresponding 7μm resolution tapping mode atomic force microscope height image.

[0035] Figure 2 The diagram shows the device structure and the transfer characteristic curves of the polymer thin-film transistors prepared in Example 1 and Comparative Example 1 of this invention.

[0036] Figure 3 Microscopic images of the polymer semiconductor F8BT patterned under white and blue light excitation conditions prepared for Example 2 of the present invention.

[0037] Figure 4 Microscopic images of the polymer semiconductor Poly-TPD patterned under white light and ultraviolet light excitation conditions were prepared for Example 3 of the present invention. Detailed Implementation

[0038] The present invention will be described below through specific embodiments, but the present invention is not limited thereto.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0040] In this invention, the electrical performance of the polymer thin-film transistor is identical when tested in atmospheric and nitrogen atmospheres.

[0041] The synthetic route of polymer PDVT-10 is described in the reference (Chen HJ; Guo YL; Yu G.; et al. Advanced Materials 2012, 24, 4589-4589.).

[0042] Synthetic route of polymer PDVT-10: 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrolo-1,4-dione (305 mg, 0.3 mmol), 1,2-(E)-bis(5'-trimethylstan-2'-C-thiophenyl)ethylene (155 mg, 0.3 mmol), Pd2(dba)3 (9 mg), P(o-tol)3 (15 mg), and 5 mL of chlorobenzene were added sequentially to a 50 mL three-necked flask. The reaction was stopped after reflux and stirring at 120 °C for 1 h under nitrogen protection. The cooled reaction mixture was poured into 200 mL of methanol solution containing 15 mL of concentrated hydrochloric acid for precipitation, and filtered to obtain the crude polymer product. The polymer was then extracted with methanol, acetone, n-hexane, dichloromethane, and chlorobenzene solvents, respectively. Finally, the obtained chlorobenzene solution was evaporated to dryness to obtain 0.29 g of black solid polymer product, with a yield of 93% and a molecular weight (M). n =38.2kDa, Molecular weight distribution index (PDI) =1.67.

[0043] Example 1

[0044] This embodiment prepares a polymer thin-film transistor based on high-precision polymer patterning technology according to the following steps.

[0045] 1) Using PI as a substrate, ultrasonically clean it once with tap water, recycled water, ethanol, and acetone, then dry it with a nitrogen gun and set it aside for use.

[0046] 2) Source and drain electrodes were fabricated using vacuum thermal evaporation with 30nm gold, and the vacuum evaporation pressure was controlled at 6×10⁻⁶. -6 Below Tor, the evaporation rate is The prepared channels have a length and width of 50 μm and 4500 μm, respectively;

[0047] 3) The OTS modified layer was prepared by vapor phase modification method, with a vacuum degree of 0.01 Pa and heating at 120℃ for 3 h;

[0048] 4) The polymer semiconductor layer was prepared by spin coating. The conditions for preparing the polymer semiconductor layer were: PDVT-10 solution concentration 6 mg / mL, o-xylene as solvent, spin coating speed 3000 rad / min, and spin coating time 1 min. The prepared polymer semiconductor film was annealed at 120℃ for 10 min to obtain a polymer semiconductor layer with a thickness of 28 nm.

[0049] 5) After the polymer semiconductor layer is fabricated, the substrate is transferred to a 172nm excimer ultraviolet lithography cavity and exposed to light for 20 minutes; the main parameter is an output intensity of 10.5 mW / cm². 2 The full width at half maximum (FWHM) was 8.9 nm, and the nitrogen flow rate was 0.75 SCFM.

[0050] 6) Prepare the dielectric layer by spin coating. The spin coating solution can be a 65 mg / mL PMMA (molecular weight 35 W) solution, the solvent is n-butyl acetate, the spin coating speed is 3000 rad / min, the spin coating time is 50 min, and after preparation, it is annealed at 90℃ for 30 min to obtain a dielectric layer with a thickness of 500 nm.

[0051] 7) A 100nm thick aluminum electrode is used as the gate electrode; the vacuum degree is 6×10⁻⁶. -6 Tor; Evaporation rate is

[0052] The polymer thin-film transistor structure obtained in this embodiment is as follows, which includes a substrate, source / drain electrodes 1 located on the substrate, and...

[0053] OTS modification layer 2 located on the source electrode and drain electrode

[0054] Polymer semiconductor layer 3 located on the OTS modified layer

[0055] 4. Patterning is performed on the polymer semiconductor layer using 172nm excimer ultraviolet light.

[0056] Dielectric layer 5 located on the polymer semiconductor layer after the patterning technique

[0057] Gate electrode 6 located on the dielectric layer

[0058] The above-described device is a top-gate bottom-electrode device structure, as shown in the schematic diagram below. Figure 2 As shown.

[0059] Comparative Example 1

[0060] Following the same preparation method as in Example 1, except that the patterning technique in step 5) was removed, a polymer thin-film transistor with a top-gate bottom contact structure was obtained.

[0061] By comparing the transfer characteristic curves of the polymer thin-film transistors in Example 1 and Comparative Example 1, it can be seen that the patterned device has a lower off-state current compared to the unpatterned device. Figure 2 A comparison of the transfer characteristic curves shows that its mobility remains between 0.10 and 0.12 cm⁻¹. 2 V -1 s -1 The off-state current is from 10 -8 A decreased to 10 -10 A indicates that polymer semiconductors can improve leakage current and enhance the quality of polymer thin-film transistors by using 172nm quasi-ultraviolet lithography patterning.

[0062] Example 2

[0063] Following steps 1), 4), and 5) of Example 1, an F8BT (purchased from Sigma) based polymer film was prepared on a PI substrate. The substrate was then patterned (transferring it into a 172nm excimer ultraviolet lithography cavity with an output intensity of 10.5 mW / cm²). 2 A specific pattern was obtained (with a full width at half maximum (FWHM) of 8.9 nm, a nitrogen flow rate of 0.75 SCFM, and an illumination time of 20 min). This pattern was then observed under a microscope in white light mode. Figure 3 Left image. Observe under a microscope in blue light mode, as shown. Figure 3 Right image. The F8BT polymer emits yellow-green light under blue light excitation mode, which is... Figure 3 The etching effect can be observed by comparing the two images.

[0064] Example 3

[0065] Following steps 1), 4), and 5) of Example 1, a polymer thin film based on Poly-TPD (purchased from Xi'an Baolai Optoelectronics Technology Co., Ltd.) was prepared on a PI substrate. The substrate was then patterned (transferring it into a 172nm excimer ultraviolet lithography cavity, with an output intensity of 10.5 mW / cm²). 2 A specific pattern was obtained (with a full width at half maximum (FWHM) of 8.9 nm, a nitrogen flow rate of 0.75 SCFM, and an illumination time of 20 min). This pattern was then observed under a microscope in white light mode. Figure 4 Left image. Observe under a microscope in ultraviolet light mode, as shown. Figure 4 The right image shows that the Poly-TPD polymer emits blue light under ultraviolet light excitation mode. Figure 4 The etching effect can be observed by comparing the two images.

Claims

1. A method for fabricating polymer thin-film transistors based on polymer semiconductor patterning, comprising the following operations: 1) Fabricate source and drain electrodes on the substrate; 2) Modify the source / drain electrodes prepared in step 1) with OTS; 3) Prepare a polymer semiconductor layer on the OTS-modified layer prepared in step 2); 4) Patterning is performed on the polymer semiconductor layer prepared in step 3) using 172nm excimer ultraviolet light; 5) Prepare a dielectric layer after the patterning technique in step 4); 6) A gate electrode is fabricated on the dielectric layer prepared in step 5) to obtain a polymer thin-film transistor device; In step 4), 172nm excimer ultraviolet lithography patterning technology is applied to the prepared polymer semiconductor; the main parameter is an output intensity greater than 10mW / cm². 2 The full width at half maximum (FWHM) was 8–10 nm, the nitrogen flow rate was 0.5–1 SCFM, and the illumination time was 10–30 min.

2. The method according to claim 1, characterized in that: The device has a top-gate bottom-electrode structure; In step 1), the substrate is a PET, PI, or PEN substrate; Both the source electrode and the drain electrode are selected from gold; The source electrode and drain electrode are prepared by vacuum evaporation; the vacuum evaporation conditions are: a vacuum degree of 10... -4 ~10 - 7 Pa; evaporation rate is 0.1~0.2 Å / s; thickness of source and drain electrodes is 27~35 nm; In step 2), the OTS modified layer is prepared by vapor phase modification; vacuum oven, vacuum degree is 0.01 Pa, heat at 120℃ for 3 h.

3. The method according to claim 1, characterized in that: In step 3), the method for preparing the polymer semiconductor layer is spin coating; In the spin coating process, the spin coating speed is 2000~3000 rad / min, and the spin coating time is 40~60s; After spin coating, annealing is performed at 120℃ for 10 minutes. The thickness of the polymer semiconductor layer is 20~35nm.

4. The method according to claim 1, characterized in that: In step 5), the preparation method is spin coating; The spin coating speed is 2000~3000 rad / min, and the spin coating time is 40~60 s; After spin coating, annealing is performed at 90°C for 30 minutes. The thickness of the dielectric layer is 250~500nm; In step 6), the gate electrode is made of aluminum; the gate electrode is prepared by vacuum evaporation; the evaporation conditions are: vacuum degree of 10... -4 ~10 -7 Pa; the vapor deposition rate is 1~5 Å / s.

5. A polymer thin-film transistor device prepared by any one of claims 1-4.

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