Polymer / inorganic heterostructure composite film and preparation method and application thereof

Abstract

The application belongs to the field of organic-inorganic heterostructure thin films, and relates to a polymer / inorganic heterostructure composite thin film and a preparation method and application thereof. The composite thin film is formed by compounding PEDOT:PSS and ITO nanocrystals, PEDOT:PSS forms a flexible network skeleton, the growth orientation of ITO nanocrystals is a (222) crystal face, a (400) crystal face or a (211) crystal face, and the ITO nanocrystals are uniformly dispersed and bonded in the PEDOT:PSS network. The flexible organic polymer PEDOT:PSS and the brittle ceramic material ITO are compounded, the surface state and the work function of the two-phase materials are regulated, the heterostructure composite thin film with a molecular-level interface combination is constructed, and the critical mechanical properties, the interface toughness and the electron mobility of the thin film are simultaneously improved, so that the demand of the flexible electronic device for the high-performance and high-reliability thin film material is met.

Description

Technical Field

[0001] This invention belongs to the field of organic-inorganic heterostructure thin films, and relates to a polymer / inorganic heterostructure composite thin film, its preparation method and application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the rapid development of modern information technology, especially the ever-increasing demand for flexible electronic devices with aesthetic appeal and multifunctionality, flexible display materials have become a research hotspot. Flexible display devices not only need excellent optoelectronic properties but also superior mechanical flexibility and stability, which places higher demands on the material system. Currently, oxide thin film materials, represented by indium tin oxide (ITO), are widely used in electronic display devices. However, ITO thin films are inherently brittle ceramic materials, prone to cracking or even fracture under bending or stretching conditions, leading to device failure. This defect severely limits its application in flexible display devices. To overcome these shortcomings, researchers have attempted to composite conductive polymer materials with conjugated π bonds with oxide thin film materials to construct organic-inorganic heterostructure composite thin films, aiming to simultaneously solve the problems of poor mechanical brittleness and low electron mobility of the thin films. Poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS) is a cross-linked network structure conductive polymer material composed of a hydrophobic conductive PEDOT core region and a hydrophilic insulating PSS shell. It has high flexibility and good water solubility, which can effectively improve the flexibility of the device and provide a certain number of charge carriers to maintain the conductivity of the thin film.

[0004] However, existing single-material systems struggle to simultaneously meet the requirements of high conductivity and high flexibility. Traditional ITO films lack flexibility and are prone to brittle fracture; while PEDOT:PSS films offer good flexibility, their conductivity stability is poor, leading to performance degradation over long-term use. Furthermore, during the composite process, differences in surface energy, work function, and other physical properties can easily result in poor interfacial bonding and low carrier mobility, hindering the achievement of an ideal molecular-level heterogeneous interface structure and thus limiting the improvement of the overall mechanical and electrical properties of the composite film. Existing technologies include modifying the surface of the ITO transparent conductive substrate to improve its interfacial performance with the organic functional layer. For example, in electrochromic devices, materials such as octadecyltrichlorosilane (OTS) are used to form a self-assembled monolayer on the ITO electrode surface to block spontaneous electron transfer between the organic functional layer and ITO, thereby suppressing self-decolorization. However, these surface modification strategies only affect the macroscopic interface between the substrate and the functional layer, failing to address the inherent brittle fracture problem of the ITO film itself, and also failing to construct a continuous mechanical toughening network within the film. When a device undergoes bending deformation, the ITO film can still develop and propagate cracks due to stress concentration, leading to device failure. Therefore, for flexible transparent electrode applications, solving the brittleness problem of ITO at the material bulk level while maintaining its high conductivity remains a critical technical bottleneck that urgently needs to be overcome.

[0005] Therefore, how to significantly improve the flexibility and interfacial mechanical properties of thin films while maintaining good conductivity has become a pressing technical problem in the field of flexible display materials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polymer / inorganic heterostructure composite thin film, its preparation method, and its application. The present invention combines the flexible organic polymer PEDOT:PSS with the brittle ceramic material ITO. By controlling the surface states and work functions of the two phases, a heterostructure composite thin film with molecular-level interfacial bonding is constructed. The aim is to simultaneously improve the critical mechanical properties, interfacial toughness, and electron mobility of the thin film, thereby meeting the requirements of flexible electronic devices for high-performance and high-reliability thin film materials.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In the first aspect, a polymer / inorganic heterostructure composite film is formed by combining PEDOT:PSS and ITO nanocrystals. PEDOT:PSS forms a flexible mesh framework, and the growth orientation of ITO nanocrystals is (222), (400), or (211) crystal planes. The ITO nanocrystals are uniformly dispersed and bonded to the PEDOT:PSS network.

[0008] This invention regulates the growth orientation of ITO nanocrystals to a (222), (400), or (211) crystal plane. First, it reduces surface energy differences, promoting interfacial wetting and bonding. Specifically, regulating the crystal plane orientation to match the surface energy of PEDOT:PSS significantly improves the wettability of the two-phase interface, reduces interfacial defects, and increases bonding strength. Second, it optimizes work function matching, reducing the heterojunction barrier. Adjusting the crystal plane makes the work function of ITO nanocrystals close to that of PEDOT:PSS, lowering the interfacial barrier when they come into contact, which is beneficial for carrier transport across the interface, reducing contact resistance, and improving the overall conductivity of the thin film. Furthermore, it can expose specific chemical bonding sites, promoting interfacial chemical bridging; for example, (222) crystal faces are rich in In-O dangling bonds and oxygen vacancies, and (211) crystal faces have a high density of Lewis acid sites, which are conducive to forming hydrogen bonds or coordination bonds with the sulfonic acid groups of the PSS chain segments in PEDOT:PSS or the oxygen / sulfur atoms on the PEDOT thiophene ring, thus achieving molecular-level interfacial bridging. If the crystal face orientation is not controlled (such as the random orientation of commercial ITO nanopowder), the surface energy distribution will be uneven, and some low surface energy crystal faces will be difficult to effectively combine with PEDOT:PSS, resulting in high interfacial defect density, enhanced carrier scattering, and decreased mechanical and electrical properties of the thin film.

[0009] This invention solves the problems of poor interfacial bonding and low carrier mobility by combining ITO nanocrystals with PEDOT:PSS, thereby significantly improving the flexibility and interfacial mechanical properties of the film while maintaining good conductivity.

[0010] In a second aspect, a method for preparing the composite thin film according to the first aspect of the present invention includes the following steps: A PEDOT:PSS aqueous solution is provided, and a modifier is added to the PEDOT:PSS aqueous solution and mixed evenly to obtain a modified PEDOT:PSS aqueous solution; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C. Using physical vapor deposition or chemical synthesis according to Sn 4+ ITO nanocrystals were prepared with an ion doping ratio of 8-12 wt%. ITO nanocrystals were added to a modified PEDOT:PSS aqueous solution, mixed evenly, and then ultrasonically dispersed to obtain a composite slurry. The composite slurry is coated into a film precursor; The membrane precursor was heat-treated at a temperature below 180°C.

[0011] During the preparation process, the surface tension of the PEDOT:PSS aqueous solution can be reduced by adding a modifier, thereby significantly improving the wettability and spreadability of the solution on the substrate. Meanwhile, the modifier does not contain Na. + K + Metal ions are used to avoid adverse effects on the conductivity of the thin film.

[0012] During the preparation process, by adjusting Sn 4+ The ion doping ratio is 8~12 wt%, which makes the preferred growth orientation of ITO nanocrystals (222), (400) or (211) crystal planes, thus facilitating effective bonding with PEDOT:PSS.

[0013] Furthermore, heat treatment at temperatures below 180°C can disrupt the composite film structure, thus preserving its mechanical and electrical properties. Using a polar organic solvent with a boiling point not lower than 180°C as a modifier can also prevent evaporation during heat treatment.

[0014] Thirdly, a method for preparing the composite thin film according to the first aspect of the present invention includes the following steps: A PEDOT:PSS aqueous solution is provided, and a modifier is added to the PEDOT:PSS aqueous solution and mixed evenly to obtain a modified PEDOT:PSS aqueous solution; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C. The modified PEDOT:PSS aqueous solution is prepared according to Sn 4+ ITO nanocrystals were prepared in situ with an ion doping ratio of 8-12 wt% to obtain a composite slurry; The composite slurry is coated into a film precursor; The membrane precursor was heat-treated at a temperature below 180°C.

[0015] Fourthly, the application of the composite thin film described in the first aspect of the present invention in flexible electronic devices.

[0016] The beneficial effects of this invention are as follows: 1. In this invention, ITO is made into nanocrystalline particles and combined with PEDOT:PSS in the bulk phase of the film to form a three-dimensional interpenetrating network structure that runs through the entire thickness direction of the film. The advantages of this structure are: (1) Bulk toughening mechanism: When the film is subjected to bending stress, the PEDOT:PSS flexible network absorbs strain energy through plastic deformation, and the ITO nanocrystals act as rigid nodes to transfer the load. The crack deflection and bridging effect at the heterogeneous interface can effectively suppress crack propagation. This toughening mechanism applies to the entire film, rather than just the substrate interface. (2) Conductive network synergy: The ITO nanocrystals form a continuous conductive path in the three-dimensional network, providing a high concentration of free electrons; the PEDOT:PSS network provides additional delocalized π-π* transport channels. The synergistic effect of the two makes the film have both high conductivity and high flexibility.

[0017] 2. The composite film provided by this invention has significantly improved flexibility and fracture resistance compared with pure ITO; Compared to pure PEDOT:PSS, the conductivity is significantly improved; compared to composite films with simple physical mixing and uncontrolled interfaces, the interfacial bonding strength, bending stability, and carrier mobility are all reproducibly improved. Therefore, this composite film has excellent comprehensive performance advantages in flexible electronic devices such as flexible transparent electrodes and flexible optoelectronic devices. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a schematic diagram of the microstructure of the PEDOT-PSS / ITO heterostructure composite film prepared in Example 1B of the present invention. Figure 2 This is a schematic diagram of the process for preparing the PEDOT-PSS / ITO heterostructure composite film in Example 1B of the present invention. Figure 3 This is a SEM image of the PEDOT:PSS modified material in Example 1B of the present invention; Figure 4 This is a SEM image of ITO nanocrystals in Example 1B of the present invention; Figure 5 This is a SEM image of the PEDOT-PSS / ITO heterostructure composite film prepared in Example 1B of the present invention.

[0020] Figure 6 The XRD pattern of the ITO nanocrystals prepared in Example 1B of this invention is compared with that of randomly oriented ITO nanopowder.

[0021] Figure 7 The following are the XPS fine spectra and peak fitting results of the composite thin film prepared in Example 1B of the present invention: (a) Summary of element binding energy data, (b) C 1s, (c) O 1s, (d) S 2p, (e) In 3d, (f) Sn 3d.

[0022] Figure 8 XPS peak shift diagrams comparing the composite film prepared in Example 1B of this invention with the pure component: (a) Sn3d, (b) S2p. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Given that existing technologies struggle to simultaneously achieve the conductivity, flexibility, and interfacial mechanical properties of thin film materials, this invention proposes a polymer / inorganic heterostructure composite thin film, its preparation method, and its applications.

[0026] A typical embodiment of the present invention provides a polymer / inorganic heterostructure composite film, which is formed by combining PEDOT:PSS and ITO nanocrystals. PEDOT:PSS forms a flexible network framework, and the growth orientation of ITO nanocrystals is (222), (400) or (211) crystal planes. The ITO nanocrystals are uniformly dispersed and bonded to the PEDOT:PSS network.

[0027] In this invention, PEDOT:PSS forms a flexible mesh framework. This flexible mesh framework is a cross-linked network structure formed by a hydrophobic and conductive PEDOT core region surrounded by a hydrophilic and insulating PSS shell. ITO nanocrystals are uniformly dispersed and bonded within the PEDOT:PSS mesh framework. The band structure at the two-phase interface is quasi-continuous, and its surface energy and work function can match the matched PEDOT:PSS, realizing molecular-level interfacial composite and forming an organic-inorganic heterostructure composite film.

[0028] In some embodiments, the PEDOT:PSS is modified PEDOT:PSS, obtained by mixing a modifier with PEDOT:PSS, thereby modifying the surface properties of PEDOT:PSS. The modifier is a nonionic fluorocarbon surfactant, a nonionic silicone surfactant, or a polar organic solvent with a boiling point not lower than 180°C. Specifically, the nonionic fluorocarbon surfactant can be Zonyl FS-300, Zonyl FSN-100, Capstone FS-30, Capstone FS-31, Futacare 2020, etc. Specifically, the nonionic silicone surfactant can be BYK-307, BYK-333, Silwet L-77, etc. Specifically, the polar organic solvent can be ethylene glycol, glycerol, sorbitol, N-methylpyrrolidone, etc. The modifier improves the surface states and work function of PEDOT:PSS, thereby better matching it with ITO. When nonionic fluorocarbon surfactants are used as modifiers, their hydrophobic fluorocarbon segments tend to interact with the hydrophobic thiophene skeleton of PEDOT, promoting the partial detachment of the PSS shell and enhancing the continuity of the PEDOT enriched phase; the fluorocarbon segments have a certain affinity for the surface of inorganic oxides, which is beneficial to the uniform dispersion of ITO nanocrystals.

[0029] In some embodiments, the particle size of ITO nanocrystals is 10~100 nm.

[0030] Another embodiment of the present invention provides a method for preparing the above-mentioned composite film, comprising the following steps: A PEDOT:PSS aqueous solution is provided, and a modifier is added to the PEDOT:PSS aqueous solution and mixed evenly to obtain a modified PEDOT:PSS aqueous solution; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C. Using physical vapor deposition or chemical synthesis according to Sn 4+ ITO nanocrystals were prepared with an ion doping ratio of 8-12 wt%. ITO nanocrystals were added to a modified PEDOT:PSS aqueous solution, mixed evenly, and then ultrasonically dispersed to obtain a composite slurry. The composite slurry is coated into a film precursor; The membrane precursor was heat-treated at a temperature below 180°C.

[0031] In some embodiments, the mass ratio of PEDOT:PSS to the modifier is 10~13:1~15.

[0032] In some embodiments, dimethyl sulfoxide is added during the preparation of the modified PEDOT:PSS aqueous solution. Specifically, the mass ratio of PEDOT:PSS to dimethyl sulfoxide in the modified PEDOT:PSS aqueous solution is 10~13:10~90.

[0033] In some embodiments, the mass ratio of ITO nanocrystals to PEDOT:PSS in the composite slurry is 1:2~8.

[0034] A third embodiment of the present invention provides a method for preparing the above-mentioned composite film, comprising the following steps: A PEDOT:PSS aqueous solution is provided, and a modifier is added to the PEDOT:PSS aqueous solution and mixed evenly to obtain a modified PEDOT:PSS aqueous solution; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C. The modified PEDOT:PSS aqueous solution is prepared according to Sn 4+ ITO nanocrystals were prepared in situ with an ion doping ratio of 8-12 wt% to obtain a composite slurry; The composite slurry is coated into a film precursor; The membrane precursor was heat-treated at a temperature below 180°C.

[0035] In some embodiments, the mass ratio of PEDOT:PSS to the modifier is 10~13:1~15.

[0036] In some embodiments, dimethyl sulfoxide is added during the preparation of the modified PEDOT:PSS aqueous solution. Specifically, the mass ratio of PEDOT:PSS to dimethyl sulfoxide in the modified PEDOT:PSS aqueous solution is 10~13:10~90.

[0037] In some embodiments, indium salt, tin salt, and urea are added to the modified PEDOT:PSS aqueous solution, the pH is adjusted to 2.8-3.2 with acid, and a hydrothermal reaction is carried out at 160-200°C to allow ITO nanocrystals to nucleate and grow in situ in PEDOT:PSS. Specifically, the indium salt refers to a compound whose cation is indium ion, such as indium chloride. Specifically, the tin salt refers to a compound whose cation is tin ion, such as tin chloride.

[0038] A fourth embodiment of the present invention provides an application of the above-described composite film in flexible electronic devices.

[0039] Specifically, the flexible electronic device can be a flexible transparent electrode or a bendable optoelectronic device, etc.

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0041] Example 1: Preparation of composite thin films by ultrasonic dispersion and spin coating Example 1A (1) PEDOT:PSS modification treatment: Take commercially available PEDOT:PSS aqueous dispersion (Clevios) TM Add 2.2 vol% DMSO and 0.12 vol% Zonyl FS-300 surfactant to pH 1000, and sonicate for 12 min.

[0042] (2) Preparation of ITO nanocrystals: In2O3 and SnO2 with a purity of 4N were used as targets, with a Sn doping ratio of 8.3 wt%. Electron beam evaporation combined with vapor deposition was used. The substrate temperature was 355℃, the deposition time was 22 min, and the vacuum degree was 10. -4 Pa yielded ITO nanocrystals with an average particle size of 38 nm.

[0043] (3) Mixing and dispersing: The ITO nanocrystals from step (2) and the modified PEDOT:PSS solution from step (1) are mixed at a mass ratio of 1:2.2 and ultrasonically dispersed for 16 min to obtain a uniform composite suspension.

[0044] (4) Spin coating: Spin coat the composite suspension from step (3) onto the cleaned glass at a spin speed of 1050 rpm for 22 s.

[0045] (5) Curing treatment: Place the film from step (4) on a hot plate and anneal and cure at 105°C for 11 min to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0046] (6) Post-processing: Allow the cured film to cool naturally to room temperature.

[0047] Example 1B (1) PEDOT:PSS modification treatment: Take commercially available PEDOT:PSS aqueous dispersion (CleviosTM PH1000), add 4.0 vol% DMSO and 0.3 vol% Zonyl FS-300 surfactant, and sonicate for 30 min.

[0048] (2) Preparation of ITO nanocrystals: In2O3 and SnO2 with a purity of 4N were used as targets, with a Sn doping ratio of 10.0 wt%. Electron beam evaporation combined with vapor deposition was used. The substrate temperature was 400℃, the deposition time was about 30 min, and the vacuum degree was 10. -4Pa yielded ITO nanocrystals with an average particle size of 42 nm.

[0049] (3) Mixing and dispersing: The ITO nanocrystals from step (2) and the modified PEDOT:PSS solution from step (1) are mixed at a mass ratio of 1:4.0 and ultrasonically dispersed for 20 min to obtain a uniform composite suspension.

[0050] (4) Spin coating: Spin coat the composite suspension from step (3) onto the cleaned glass at a spin speed of 1500 rpm for 40 s.

[0051] (5) Curing treatment: Place the film from step (4) on a hot plate and anneal and cure at 130°C for 15 min to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0052] (6) Post-processing: Allow the cured film to cool naturally to room temperature.

[0053] The microstructure of the prepared composite film is as follows Figure 1 As shown, the preparation process is as follows: Figure 2 As shown in the figure. During the preparation process, the SEM images of the PEDOT:PSS modified product are shown in the figure. Figure 3 As shown, the SEM image of ITO nanocrystals is as follows. Figure 4 As shown, the SEM image of the PEDOT-PSS / ITO heterostructure composite film is as follows. Figure 5 As shown.

[0054] The composite film prepared in this embodiment was structurally characterized. Figure 6 The XRD pattern of ITO nanocrystals shows obvious (222), (400), and (211) preferred orientations. Figure 7 The XPS fine spectrum and peak fitting results of the composite thin film show that the binding energies of each element (C 1s, O 1s, S 2p, In 3d, Sn 3d) are in good agreement with the theoretical values, confirming the successful composite of PEDOT:PSS and ITO. Figure 8 The peak positions of Sn 3d and S 2p in the pure component and composite film were further compared, among which Sn 3d 5 / 2 The shift from 486.5 eV to 486.1 eV and the shift of S 2p from 168.0 eV to 168.5 eV indicate the presence of electronic interactions or weak chemical bonding at the interface between the two phases.

[0055] Performance characterization results To verify the improved flexibility, mechanical properties, and conductivity of the PEDOT:PSS / ITO heterostructure composite film prepared in this invention, a film sample (approximately 100 nm thick) prepared in Example 1B was characterized and compared with pure ITO films and pure PEDOT:PSS films of the same thickness. Specific test data are as follows: Flexible bending performance Dynamic bending cycle testing was used, with a curvature radius of 5 mm. The change rate of sheet resistance of the thin film was measured after every 1000 cycles. The results are shown in the table below:

[0056] Among them, the pure ITO film develops macroscopic cracks on its surface after about 6,000 bending cycles, and its resistance increases sharply; the composite film of the present invention has no visible cracks on its surface after 10,000 bending cycles, and its resistance change rate remains within 10%.

[0057] Mechanical properties (fracture resistance and interfacial toughness) The evolution of crack density with strain was observed by uniaxial tensile testing combined with in-situ optical microscopy. The critical fracture strain and interfacial shear strength of the thin film were estimated based on the crack spacing method. The results are as follows:

[0058] The composite film of this invention provides a flexible mesh framework due to the PEDOT:PSS phase and a rigid reinforcing unit due to the ITO nanocrystalline phase. The interface between the two phases achieves crack deflection and bridging toughening, and the overall fracture toughness is improved by more than an order of magnitude compared with pure ITO film.

[0059] Electrical conductivity The sheet resistance of the thin film was determined using the four-probe method, and the carrier concentration and mobility were measured using the Hall effect. The results are as follows:

[0060] Example 1 shows that the sheet resistance of the composite thin film is reduced by about 74% compared with that of the pure PEDOT:PSS thin film, and the carrier mobility is increased by about 10 times, achieving a good balance between conductivity and flexibility.

[0061] Example 1C (1) PEDOT:PSS modification treatment: Take commercially available PEDOT:PSS aqueous dispersion (CleviosTM PH1000), add 7.5 vol% DMSO and 0.9 vol% Zonyl FS-300 surfactant, and sonicate for 55 min.

[0062] (2) Preparation of ITO nanocrystals: In2O3 and SnO2 with a purity of 4N were used as targets, with a Sn doping ratio of 11.7 wt%. Electron beam evaporation combined with vapor deposition was used. The substrate temperature was 445℃, the deposition time was 38 min, and the vacuum degree was 10. -4 Pa yielded ITO nanocrystals with an average particle size of 45 nm.

[0063] (3) Mixing and dispersing: The ITO nanocrystals from step (2) and the modified PEDOT:PSS solution from step (1) are mixed at a mass ratio of 1:7.5 and ultrasonically dispersed for 28 min to obtain a uniform composite suspension.

[0064] (4) Spin coating: The composite suspension from step (3) is spin coated onto the cleaned glass at a spin speed of 1950 rpm for 58 s.

[0065] (5) Curing treatment: Place the film from step (4) on a hot plate and anneal and cure at 165°C for 19 min to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0066] (6) Post-processing: Allow the cured film to cool naturally to room temperature.

[0067] Example 2: Preparation of composite thin films by in-situ growth and casting method Example 2A (1) PEDOT:PSS modification treatment: Same as step (1) in Example 1A.

[0068] (2) In situ growth of ITO: 0.052 M InCl3·4H2O, 0.0052 M SnCl4·5H2O and 0.11 M urea were added to the modified PEDOT:PSS solution (concentration of 0.52 wt%) in step (1), stirred evenly, and the pH was adjusted to 2.85 with dilute hydrochloric acid.

[0069] (3) Hydrothermal reaction: The mixture from step (2) was transferred into a hydrothermal reactor and reacted at 163°C for 8.5 h to allow ITO nanocrystals to nucleate and grow in situ in PEDOT:PSS with an average particle size of 18 nm.

[0070] (4) Casting film: Cast the composite slurry from step (3) onto the cleaned glass and spread it evenly.

[0071] (5) Curing treatment: The film from step (4) was dried at 62°C for 6.5 h and then annealed at 132°C for 1.1 h to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0072] (6) Post-processing: Same as step (6) in Example 1A.

[0073] Example 2B (1) PEDOT:PSS modification treatment: Same as step (1) in Example 1A.

[0074] (2) In situ growth of ITO: 0.10 M InCl3·4H2O, 0.010 M SnCl4·5H2O and 0.15 M urea were added to the modified PEDOT:PSS solution (concentration of 0.80 wt%) in step (1), stirred evenly, and the pH was adjusted to 3.00 with dilute hydrochloric acid.

[0075] (3) Hydrothermal reaction: The mixture from step (2) is transferred into a hydrothermal reactor and reacted at 180°C for 12 h to allow ITO nanocrystals to nucleate and grow in situ in PEDOT:PSS with an average particle size of 21 nm.

[0076] (4) Casting film: Cast the composite slurry from step (3) onto the cleaned glass and spread it evenly.

[0077] (5) Curing treatment: The film from step (4) is dried at 80°C for 8 h and then annealed at 150°C for 1.5 h to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0078] (6) Post-processing: Same as step (6) in Example 1A.

[0079] Example 2C (1) PEDOT:PSS modification treatment: Same as step (1) in Example 1A.

[0080] (2) In situ growth of ITO: 0.19 M InCl3·4H2O, 0.019 M SnCl4·5H2O and 0.29 M urea were added to the modified PEDOT:PSS solution (concentration of 0.97 wt%) in step (1), stirred evenly, and the pH was adjusted to 3.18 with dilute hydrochloric acid.

[0081] (3) Hydrothermal reaction: The mixture from step (2) is transferred into a hydrothermal reactor and reacted at 198°C for 15.5 h to allow ITO nanocrystals to nucleate and grow in situ in PEDOT:PSS with an average particle size of 24 nm.

[0082] (4) Casting film: Cast the composite slurry from step (3) onto the cleaned glass and spread it evenly.

[0083] (5) Curing treatment: The film from step (4) was dried at 97°C for 9.5 h and then annealed at 168°C for 1.9 h to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0084] (6) Post-processing: Same as step (6) in Example 1A.

[0085] Example 3: Preparation of composite thin films by plasma treatment to enhance interfacial bonding Example 3A (1) PEDOT:PSS modification treatment: Same as step (1) in Example 1A.

[0086] (2) Preparation of ITO nanocrystals: Same as step (2) in Example 1A.

[0087] (3) Mixing and dispersing: The ITO nanocrystals from step (2) and the modified PEDOT:PSS solution from step (1) are mixed at a mass ratio of 1:2.3 and ultrasonically dispersed for 16 min to obtain a uniform composite suspension.

[0088] (4) Spin coating: The composite suspension from step (3) is spin coated onto the cleaned PET substrate at a spin speed of 1050 rpm for 22 s.

[0089] (5) Plasma treatment: The wet film from step (4) is placed in an Ar plasma treatment device with a power of 32 W, a treatment time of 1.1 min, a gas flow rate of 22 sccm, and a working pressure of 12 Pa.

[0090] (6) Curing treatment: The film from step (5) was annealed and cured at 105°C for 11 min to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0091] (7) Post-processing: Same as step (6) in Example 1A.

[0092] Example 3B (1) PEDOT:PSS modification treatment: Same as step (1) in Example 1A.

[0093] (2) Preparation of ITO nanocrystals: Same as step (2) in Example 1A.

[0094] (3) Mixing and dispersing: The ITO nanocrystals from step (2) and the modified PEDOT:PSS solution from step (1) are mixed at a mass ratio of 1:4.0 and ultrasonically dispersed for 25 min to obtain a uniform composite suspension.

[0095] (4) Spin coating: The composite suspension from step (3) is spin coated onto the cleaned PET substrate at a spin speed of 2000 rpm for 45 s.

[0096] (5) Plasma treatment: The wet film from step (4) is placed in an Ar plasma treatment device with a power of 50 W, a treatment time of 2.0 min, a gas flow rate of 30 sccm, and a working pressure of 20 Pa.

[0097] (6) Curing treatment: The film from step (5) is annealed and cured at 130°C for 15 min to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0098] (7) Post-processing: Same as step (6) in Example 1A.

[0099] Example 3C (1) PEDOT:PSS modification treatment: Same as step (1) in Example 1A.

[0100] (2) Preparation of ITO nanocrystals: Same as step (2) in Example 1A.

[0101] (3) Mixing and dispersing: The ITO nanocrystals from step (2) and the modified PEDOT:PSS solution from step (1) are mixed at a mass ratio of 1:7.3 and ultrasonically dispersed for 28 min to obtain a uniform composite suspension.

[0102] (4) Spin coating: The composite suspension from step (3) is spin coated onto the cleaned PET substrate at a spin speed of 1950 rpm for 58 s.

[0103] (5) Plasma treatment: The wet film from step (4) is placed in an Ar plasma treatment device with a power of 68 W, a treatment time of 2.9 min, a gas flow rate of 38 sccm, and a working pressure of 28 Pa.

[0104] (6) Curing treatment: The film from step (5) was annealed and cured at 165°C for 19 min to obtain a PEDOT:PSS / ITO heterostructure composite film.

[0105] (7) Post-processing: Same as step (6) in Example 1A.

[0106] Comparative Example 1: Fullerene-doped PEDOT:PSS pure organic composite film Water-soluble fullerene derivative C 60 (OH) 24 The solution was mixed with a PEDOT:PSS aqueous solution at a mass ratio of 1:100, ultrasonically dispersed, and then spin-coated into a film, which was then cured under the same conditions.

[0107] Performance characterization results: The sheet resistance (approximately 360 Ω / □) is significantly higher than that of the embodiment of the present invention. After 5000 bending cycles, the sheet resistance increases by more than 200%. SEM shows that the fullerenes aggregate and cannot form interpenetrating networks and heterogeneous interface coupling effects.

[0108] Comparative Example 2: Using an ionic surfactant to replace Zonyl FS-300 Replace Zonyl FS-300 in step (1) of Example 1B with an equal volume of sodium dodecyl sulfate (SDS, an anionic surfactant), and keep the other steps unchanged.

[0109] Test results: The sheet resistance of the obtained composite film was 220 Ω / □, which was significantly higher than that of the sample using Zonyl FS-300 (65 Ω / □); after 5000 bending cycles, the resistance change rate reached 35%, and the stability decreased significantly.

[0110] Cause analysis: SDS ionizes into Na in solution. + Na + The binding of sulfonate groups on the PSS chain weakens the phase separation driving force between PEDOT and PSS, reducing the continuity of the PEDOT conductive network; simultaneously, Na... + Residual surfactants in the film migrate under the influence of an electric field, leading to decreased conductivity and stability. Therefore, ionic surfactants are not recommended for use in this invention.

[0111] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polymer / inorganic heterostructure composite film, characterized in that, It is formed by combining PEDOT:PSS and ITO nanocrystals. PEDOT:PSS forms a flexible network framework, and the growth orientation of ITO nanocrystals is (222), (400) or (211) crystal planes. The ITO nanocrystals are uniformly dispersed and bonded to the PEDOT:PSS network.

2. The composite film as described in claim 1, characterized in that, The PEDOT:PSS is a modified PEDOT:PSS, which is obtained by mixing a modifier with PEDOT:PSS, thereby modifying the surface properties of PEDOT:PSS by the modifier; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C.

3. The composite film as described in claim 1, characterized in that, The particle size of ITO nanocrystals is 10~100nm.

4. A method for preparing the composite thin film according to claim 1, characterized in that, Includes the following steps: A PEDOT:PSS aqueous solution is provided, and a modifier is added to the PEDOT:PSS aqueous solution and mixed evenly to obtain a modified PEDOT:PSS aqueous solution; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C. The ITO nanocrystals are prepared by physical vapor deposition or chemical synthesis method according to Sn 4+ The ITO nanocrystals are prepared by physical vapor deposition or chemical synthesis method according to Sn ITO nanocrystals were added to a modified PEDOT:PSS aqueous solution, mixed evenly, and then ultrasonically dispersed to obtain a composite slurry. The composite slurry is coated into a film precursor; The membrane precursor was heat-treated at a temperature below 180°C.

5. The preparation method according to claim 4, characterized in that, In the composite slurry, the mass ratio of ITO nanocrystals to PEDOT:PSS is 1:2~8.

6. A method for preparing the composite thin film according to claim 1, characterized in that, Includes the following steps: A PEDOT:PSS aqueous solution is provided, and a modifier is added to the PEDOT:PSS aqueous solution and mixed evenly to obtain a modified PEDOT:PSS aqueous solution; the modifier is a nonionic fluorocarbon surfactant, a nonionic organosilicon surfactant, or a polar organic solvent with a boiling point of not less than 180°C. The modified PEDOT:PSS aqueous solution is prepared according to Sn 4+ ITO nanocrystals were prepared in situ with an ion doping ratio of 8-12 wt% to obtain a composite slurry; The composite slurry is coated into a film precursor; The membrane precursor was heat-treated at a temperature below 180°C.

7. The preparation method according to claim 5 or 6, characterized in that, The mass ratio of PEDOT:PSS to modifier is 10~13:1~15; Alternatively, dimethyl sulfoxide may be added during the preparation of the modified PEDOT:PSS aqueous solution; or, in the modified PEDOT:PSS aqueous solution, the mass ratio of PEDOT:PSS to dimethyl sulfoxide is 10~13:10~90.

8. The preparation method according to claim 6, characterized in that, Indium salt, tin salt and urea are added to the modified PEDOT:PSS aqueous solution, the pH is adjusted to 2.8~3.2 with acid, and hydrothermal reaction is carried out at 160~200℃ to enable ITO nanocrystals to nucleate and grow in situ in PEDOT:PSS.

9. The application of the composite thin film according to any one of claims 1 to 3 in flexible electronic devices.

10. The application as described in claim 9, characterized in that, The flexible electronic device can be a flexible transparent electrode or a bendable optoelectronic device.

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