Conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes

Abstract

The present invention belongs to the field of conductive inks and discloses a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes. The conductive ink is prepared from PEDOT:PSS, carboxylated carbon nanotubes, [EMIM][TCB], polyacrylate, salicylic acid, and DMSO. The conductive ink provided by the present invention, which is based on PEDOT:PSS, introduces [EMIM][TCB], carboxylated carbon nanotubes, salicylic acid, and DMSO to improve ink performance. The resulting conductive ink has high electrical conductivity, strong antioxidant properties, and good printing properties. Furthermore, the flexible transparent electrode prepared from the conductive ink has high electrical conductivity and high light transmittance, making it well-suited for applications such as wearable devices for the human body and electronic skin for robots.

Description

Technical Field

[0001] The present invention belongs to the field of conductive inks, and in particular relates to a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes. Background Art

[0002] Flexible transparent electrodes (TCEs) have attracted significant attention in a variety of applications, including touch interfaces, organic light-emitting diodes (OLEDs), interactive displays, energy storage, and energy harvesting. To date, indium tin oxide (ITO) has been the most commonly used TCE material due to its outstanding optoelectronic properties, including high transparency (>85%) and low sheet resistance (10–100 Ω / sq). However, ITO suffers from several significant drawbacks, hindering its ability to meet the demands of new flexible electronics. It requires high-temperature and vacuum processing, but the plastic substrates are not heat-resistant, limiting its optoelectronic performance. It is brittle and prone to cracking or peeling when bent, making it unsuitable for dynamic deformations such as foldable displays and wearable devices. Circuit etching on flexible substrates is prone to damage, resulting in high processing costs and low yield for large-area fabrication. These limitations have driven the development of new transparent conductive materials that combine the excellent optoelectronic properties of ITO with the flexibility and reliability of ITO. Metals (nanoparticles or nanowires), carbon nanotubes, graphene and its derivatives, and conductive polymers have been explored in this area.

[0003] Patent CN119092180A proposes a method for preparing a UV- and ozone-resistant silver nanowire composite transparent electrode. This method utilizes a three-layer structure to enhance the stability of the silver nanowire electrode. First, silver nanowires are spin-coated onto a transparent substrate to form a conductive network. Then, an aluminum-doped zinc oxide (AZO) protective layer is deposited onto the silver nanowires using electrochemical deposition. Finally, a tin dioxide (SnO2) nanocrystalline protective layer is spin-coated using a sol-gel method. The AZO / SnO2 double-layer oxide provides synergistic protection, leveraging the high carrier mobility of AZO to maintain conductivity while the dense structure of SnO2 blocks oxidative corrosion. This allows the electrode to maintain a low sheet resistance even after 15 minutes of UV- and ozone treatment, significantly improving its oxidation resistance compared to unprotected silver nanowires. However, this approach suffers from a loss of photoelectric performance, with transmittance dropping from 83.73% for pure silver nanowires to 70.26%. Furthermore, the strict temperature, concentration, and voltage control required for the electrodeposition process, coupled with the double-layer spin-coating heat treatment, increases process complexity and may affect mass production stability.

[0004] Patent CN119305286A proposes a method for preparing a multi-layer composite electrode. Its core innovation lies in the use of multi-walled carbon nanotube film as a heating layer. First, the base layer is preheated, and a dispensing machine is used to spray moisture-curing polyurethane adhesive (PUR) in a specific path. The lower waterproof layer, carbon nanotube film / electrode layer, upper waterproof layer and antibacterial layer are bonded in sequence through a hot pressing process, ultimately forming a five-layer composite structure. By aligning the multi-walled carbon nanotubes in the same direction, a longitudinal conductivity (>0.8×10 5 The S / m ratio is significantly higher than that of directional conductive films in the transverse direction. Combined with flexible copper electrodes arranged in a warp and weft pattern, this achieves uniform heating with low power consumption while maintaining ultra-thin thickness and bendable flexibility. While the conductive anisotropy of carbon nanotube films improves longitudinal current efficiency, insufficient transverse conductivity can cause localized heat accumulation, particularly in directions not parallel to the electrodes. Furthermore, the carbon nanotube material's approximately 80% visible light absorption results in a transmittance of less than 40%, limiting its application in transparent or semi-transparent electrodes.

[0005] Patent CN117860255A proposes a method for screen-printing flexible electrodes based on flash graphene. The core process involves ball-milling flash graphene prepared by Joule heating flash evaporation with a specific binder in a specific proportion to form a conductive paste with a nanochannel structure. This paste is then screen-printed onto a flexible fiber fabric and then dried at low temperature to form the final product. The high-surface-area flash graphene creates a three-dimensional conductive network, achieving a low square resistance of 125Ω / sq while maintaining 98% of the fabric's original air permeability. The mechanical interlocking structure between the fiber fabric substrate and the paste enhances wear resistance, with resistance fluctuations of less than 5% after 10,000 friction cycles. While the initial conductivity of this electrode is superior to that of traditional gel electrodes, its low transmittance limits its application in transparent wearables. This lack of transmittance makes it difficult to achieve both optical transparency and conductivity, limiting its application in medical applications requiring visual monitoring of skin condition. Furthermore, while a high binder content ensures adhesion, it hinders the close packing of the graphene, making it difficult to further increase the conductivity to the level of metal electrodes.

[0006] Conductive polymers have gradually attracted the attention of researchers due to their inherent flexibility, tunable optoelectronic properties, simple synthesis, and low-temperature processing. Among them, poly(3,4-ethylenedioxythiophene):styrene (PEDOT:PSS) has become the most commonly used conductive polymer for flexible transparent electrodes due to its high conductivity, biocompatibility, non-toxicity, and low cost. Its conductivity and transmittance are comparable to those of traditional electrode materials.

[0007] Patent CN119371642A provides a method for preparing PEDOT:PSS dispersions by adding different emulsifiers to manipulate their properties. The core process involves introducing an amphiphilic emulsifier during the oxidative polymerization of EDOT monomers and polystyrene sulfonic acid (PSS) to manipulate the PEDOT molecular structure. The emulsifier reduces surface tension, forming microdroplets that provide an optimal environment for chain growth, allowing the PEDOT molecules to form a more ordered linear structure. Ultimately, the film conductivity reaches 377-387 S / cm, a significant improvement over traditional methods. However, the conductivity of the dispersion obtained in this patent still lags significantly behind that of commercial products.

[0008] Patent CN119530995A proposes a method for preparing PEDOT:PSS-based composite fibers loaded with silver nanoparticles. The method involves mixing a silver nanowire solution with a PEDOT:PSS solution to form a spinning dope. Solvent evaporation induces a synergistic effect with Ag-S bonds, resulting in the in-situ generation of a high-density of silver nanoparticles on the fiber surface. The silver nanowires within the fiber form a conductive network (conductivity 1019 S / cm). While high concentrations of silver nanowires increase conductivity to metallic levels, excessive metal content can significantly reduce light transmittance, limiting its potential for use in transparent flexible devices. Furthermore, dense silver particles on the surface can exacerbate light scattering, further reducing optical transparency and making it difficult to meet the requirements of transmissive optical sensing.

[0009] Patent CN104212243A discloses a method for preparing a neutralized PEDOT:PSS conductive ink. Following the polymerization of EDOT and PSS, an alkaline modifier is directly added to adjust the pH of the system to 5.0-9.0. An aging phase allows the system to naturally develop a viscosity of 1,000-50,000 mPa·s. Inorganic salts are then removed through an ion exchange resin, resulting in a neutral dispersion without a thickener. This process combines neutralization with viscosity adjustment, avoiding the performance impairment associated with non-conductive additives in traditional post-thickening processes. By adding a guanosine-formaldehyde condensate and a non-water-soluble polyester adhesive, the coating significantly improves adhesion and solvent resistance while maintaining conductivity (sheet resistance as low as 537 Ω / sq). However, this conductive ink still faces the challenge of balancing conductivity and transmittance: when the adhesive addition exceeds 2wt%, the sheet resistance rises to over 800 Ω / sq, while transmittance decreases by approximately 3%. In addition, the pH control accuracy during the neutralization process directly affects the stability of the dispersion. If it exceeds the preferred range of 6.5-7.2, the conductivity will decrease by 10-15%.

[0010] Although great progress has been made in the research of PEDOT:PSS conductive inks, the following problems still exist:

[0011] 1. The conductivity of PEDOT:PSS is primarily determined by PEDOT. PSS is the component that dissolves, stabilizes, and disperses PEDOT, but it itself is not conductive. Excessive PSS restricts charge flow, thereby reducing the conductivity of the film. Reducing the impact of PSS or optimizing its distribution is key to improving conductivity. The conductivity of PEDOT:PSS conductive films depends not only on the material's composition but also on its molecular structure and chain stacking. If the PEDOT chains are not tightly packed, the charge transfer path becomes discontinuous, resulting in reduced conductivity.

[0012] 2. Due to its rigid conjugated main chain and strong interchain interactions, the films prepared from PEDOT:PSS have poor inherent stretchability, low elongation at break, low ductility, and are prone to brittle fracture under external forces. PSS has strong hydrophilicity and ionicity, which limits the mechanical properties of the film under external forces. In order to improve the mechanical properties of PEDOT:PSS, it is usually necessary to enhance its elasticity and ductility by introducing mechanical modification agents. However, these mechanical modification agents often introduce additional interfacial impedance or hydrophobicity, hindering the flow of electrons or ions, and also leading to excessive cross-linking or aggregation of PEDOT:PSS chains, which reduces the freedom of the PEDOT chain segments and reduces the electrical conductivity of PEDOT:PSS.

[0013] 3. The conductive properties of PEDOT:PSS are very sensitive to environmental humidity. In a high humidity environment, the conductivity of the PEDOT:PSS film will be affected, resulting in unstable performance. When the humidity increases, water and oxygen in the air will promote the oxidation reaction of the PEDOT chain, forming an oxidized form of PEDOT with poor conductivity. The oxidation process reduces the conductivity of the PEDOT chain, thereby reducing the overall conductivity of the film. In addition, oxidation causes structural changes in the PEDOT chain, further affecting the conductive path. The conductive mechanism of PEDOT:PSS includes both electronic conduction and ionic conduction. When the humidity is too high, hydration enhances ionic conductivity, but at the same time, electronic conduction may be limited by the influence of oxidation and structural changes, resulting in a competition between the conduction efficiency of the two, which in turn affects the conductive properties of the flexible transparent electrode prepared with PEDOT:PSS conductive ink.

[0014] 4. PEDOT:PSS is formed through the copolymerization of PEDOT and PSS. In alkaline environments, PEDOT degrades (e.g., through deprotonation or oxidation), resulting in decreased conductivity. Alkaline environments also weaken the interaction between PSS and PEDOT, affecting ink stability. In overly acidic environments (pH < 4), PEDOT molecules degrade or chemically react, reducing their conductivity. Excessive dissociation of PSS can also negatively impact the conductive network.

[0015] 5. For different printing methods, the rheological properties of the ink are key factors in ensuring printability and film uniformity. PEDOT:PSS, as a readily solution-processable formulation, has become an ideal material for digital printing technologies. However, the inherent rheological properties of pristine PEDOT:PSS suspensions, characterized by low viscosity and high surface tension, make them less than ideal inks for printing applications. Summary of the Invention

[0016] In response to the shortcomings of the above-mentioned existing technologies, the present invention provides a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes, aiming to effectively improve the problems of low conductivity, poor printability, and poor humidity sensitivity existing in conductive inks based on PEDOT:PSS, so that the prepared conductive ink can be widely used in the fields of wearable electronics and electronic skin.

[0017] In order to solve the above problems, the present invention adopts the following technical solutions:

[0018] The conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes has the following components by mass percentage: PEDOT:PSS 55-65%, carboxylated carbon nanotubes 7.5%, 1-ethyl-3-methylimidazolium tetracyanoborate [EMIM][TCB] 15-25%, polyacrylate 5%, salicylic acid 2.5%, and DMSO 5%.

[0019] Most preferably, the components of the conductive ink are composed of: PEDOT:PSS 60%, carboxylated carbon nanotubes 7.5%, [EMIM][TCB] 20%, polyacrylate 5%, salicylic acid 2.5%, and DMSO 5% in percentage by mass.

[0020] The conductive ink based on PEDOT:PSS provided by the present invention incorporates [EMIM][TCB], carboxylated carbon nanotubes, salicylic acid, and DMSO to improve ink performance. [EMIM][TCB] induces efficient ion exchange within the PEDOT:PSS; the carboxylated carbon nanotubes promote electron transport within the PEDOT:PSS network through π-π stacking interactions between their carboxyl functional groups and PEDOT chains; and salicylic acid interacts with the sulfonic acid groups in PSS through hydrogen bonding, π-π bonding, and electrostatic interactions, optimizing the interaction between PEDOT and PSS and helping to form a more uniform and stable conductive network. This improves the overall conductivity of the ink, while also reducing the surface tension of the ink and improving its wettability and spreadability on various substrates. The abundant ions provided by [EMIM][TCB] enhance hydration, increase the diffusivity of ions in the ionic liquid within the film, improve the cooperative conduction of ions and electrons, and reduce the degree of PEDOT oxidation, thereby enhancing the antioxidant properties of the conductive ink. Using DMSO as a solvent can, on the one hand, improve the conductivity of the ink, and on the other hand, reinforce the mechanical properties of the ink.

[0021] Furthermore, the mass ratio of PSS to PEDOT in the PEDOT:PSS is 2.5:1. This ratio allows PSS to form a moderate steric hindrance effect, which not only ensures the full dispersion of PEDOT, but also reduces the inhibition of the insulating layer on conductivity. Secondly, the synergistic effect of carboxylated carbon nanotubes and salicylic acid can partially replace the dispersing function of PSS. The interaction between its carboxyl group and the sulfonic acid group of PSS can weaken the strong Coulomb attraction between PEDOT and PSS, so that the stability of the system can be maintained when the proportion of PSS is reduced. In addition, the electrostatic interaction between the cations in the [EMIM][TCB] ionic liquid and PSS can further promote the phase separation of the PEDOT chain. The size and density of the PEDOT conductive domains formed at this ratio are balanced, maximizing the proportion of quinone structure, so that the conductivity can be further improved.

[0022] The present invention further provides a method for preparing a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes, comprising the following steps:

[0023] Step 1: At a concentration of 5 mg mL -1To an ethanol dispersion of carboxylated carbon nanotubes, [EMIM][TCB] and salicylic acid were added sequentially while stirring. The mixture was then ultrasonically dispersed and stirred continuously for 1-3 hours at room temperature to obtain a mixed solution A. Ultrasonic treatment utilizes the cavitation effect of ultrasound to thoroughly mix [EMIM][TCB], salicylic acid, and carboxylated carbon nanotubes, breaking up particle agglomerates and improving the uniformity and stability of the solution. Continuous stirring further promotes interaction between the components, allowing the additives to be better coated on the surface of the carboxylated carbon nanotubes, forming a stable mixed system.

[0024] Step 2: Filter a 1-2% PEDOT:PSS dispersion in ethanol through a syringe filter. Add the filtered PEDOT:PSS dispersion in ethanol, polyacrylate, and DMSO to the mixed solution A and stir at room temperature for 1-3 hours to obtain a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes. Filtration removes impurities, aggregates, and large particles in the PEDOT:PSS dispersion in ethanol, ensuring the purity and uniformity of the PEDOT:PSS solution, thereby improving the performance of the final conductive ink. During room-temperature stirring, the PEDOT:PSS, polyacrylate, and DMSO are thoroughly mixed with the mixed solution A, allowing the components to interact with each other.

[0025] Compared with existing technologies, the conductive ink based on PEDOT:PSS provided by the present invention introduces [EMIM][TCB], carboxylated carbon nanotubes, salicylic acid, and DMSO to improve ink performance. The resulting conductive ink has high conductivity, strong antioxidant properties, and good printing performance. The flexible transparent electrode prepared from the conductive ink also has high light transmittance. The beneficial effects of the present invention are specifically reflected in:

[0026] 1. The conductivity of the conductive ink provided by the present invention is not less than 500 S / cm, and the conductivity of the flexible transparent electrode with a thickness of not more than 10 μm prepared from the conductive ink is not less than 1500 S / cm. The excellent conductive performance mainly comes from the following aspects: (1) Strong interactions between the hydrophilic cations of [EMIM][TCB] and the hydrophilic PSS, and between the hydrophobic anions and the hydrophobic PEDOT clusters, respectively, induce efficient ion exchange within PEDOT:PSS. This spontaneous ion exchange triggers the separation of PEDOT and PSS, and at the same time, the π stacking order in the PEDOT domain is also improved. On the one hand, the hydrophobic anions covering the surface of the PEDOT polymer are expected to hinder the attachment of PSS anions to the PEDOT surface. The hydrophilic, non-planar cations remain in the aqueous phase and will not embed with the hydrophobic anions within the π-stacked PEDOT clusters, thereby promoting the production of more crystalline and interconnected PEDOT nanofiber structures. The induced structural change of the PEDOT chain, from a benzene structure to a quinone structure with a flatter chain conformation, contributes to denser molecular stacking. These microscopic changes promote carrier transport by enhancing charge carrier mobility and density, ultimately improving conductivity. (2) The introduction of carboxylated carbon nanotubes can promote the transport of electrons in the PEDOT:PSS network through the π-π stacking interaction between its carboxyl functional groups and the PEDOT chains, thereby enhancing the conductive properties of PEDOT. The functional groups on the carboxylated carbon nanotubes weaken the Coulomb attraction between PEDOT and PSS, and the conductive network of the carboxylated carbon nanotubes forms an electron migration channel with the conductive chains of PEDOT:PSS. This composite structure forms a denser conductive network through the connection of the carboxylated carbon nanotubes, providing additional electron migration paths, thereby improving the conductivity of the conductive ink. (3) Salicylic acid further optimizes the interaction between PEDOT and PSS by forming hydrogen bonds or other weak interactions with the sulfonic acid groups of PSS, forming a more uniform and stable conductive network, thereby improving the overall conductivity of the ink.

[0027] 2. The elongation at break of the flexible transparent electrode with a thickness of no more than 10 μm prepared from the conductive ink provided by the present invention is no more than 10%. The excellent mechanical properties mainly come from the following aspects: (1) The introduction of salicylic acid forms an interaction with the sulfonic acid groups in PSS through hydrogen bonds, π-π bonds and electrostatic interactions. This interaction enhances the structural stability of PEDOT:PSS and also improves the microscopic arrangement of the film. The hydrophilicity and dispersibility of salicylic acid improve the uniform dispersion of PEDOT:PSS molecules in the solution, thereby forming a more uniform film, effectively reducing the pores and defects in the film, and improving the mechanical strength and durability of the film. (2) The introduction of DMSO can effectively improve the rheological properties of the ink, so that the ink forms a uniform and strong network structure during the curing process. Since PEDOT:PSS will generate stress during the curing process, the presence of DMSO can effectively reduce this stress, thereby improving the crack resistance and flexibility of the ink.

[0028] 3. A flexible transparent electrode with a thickness of no more than 10 μm, prepared from the conductive ink provided by the present invention, maintained conductivity above 90% of its initial value after testing in an oxidizing environment, with oxidation loss of less than 10%. The introduction of [EMIM][TCB] stabilizes the conductivity of PEDOT and reduces oxidation of PEDOT chains. The cations and anions in [EMIM][TCB] interact with the PEDOT chains, optimizing the electronic conduction pathways of the PEDOT chains, reducing the degree of PEDOT oxidation, and increasing the efficiency of electron migration within the PEDOT chains, thereby enhancing the conductivity of the film. The abundant ions in [EMIM][TCB] enhance the hydration of the film, making it easier for the PSS chains in the PEDOT:PSS film to exchange ions with [EMIM][TCB]. This enhanced hydration increases the diffusivity of ions in the ionic liquid within the film, improving the cooperative conduction of ions and electrons. [EMIM][TCB] not only improves the conductivity of the film through ionic conduction but also further optimizes its electronic transport properties by improving the hydration of PEDOT:PSS.

[0029] 4. The pH value of the conductive ink provided by the present invention is about 5.5. By introducing salicylic acid to neutralize alkalinity, the pH of the ink system is adjusted to a milder value, making the PEDOT:PSS system in the ink more stable and avoiding the negative impact of excessive acidity on the viscosity and fluidity of the ink. A suitable acidic environment helps PEDOT ionization and promotes its conductivity, while avoiding excessive acidity that causes damage to the PEDOT polymer chain structure or excessive degradation. The interaction between salicylic acid and the sulfonic acid groups of PSS further enhances the stability of the ink, avoids uneven film formation or ink precipitation due to changes in pH value, thereby ensuring the uniformity and stability of the final printed pattern or film layer.

[0030] 5. The conductive ink provided by this invention has a viscosity of 2000-3000 mPa·s, making it suitable for inkjet printing, screen printing, and other applications. As an ionic liquid, [EMIM][TCB] exhibits strong ionic interactions and good solubility, interacting with PEDOT and PSS molecules in the ink, thereby effectively improving the dispersion of the PEDOT:PSS mixture. This improved dispersion reduces aggregation between polymer molecules, resulting in a more uniform ink. Ionic liquids inherently have low volatility and moderate viscosity, and their addition effectively reduces the overall viscosity of the ink and regulates its fluidity. This improves the fluidity and printability of the ink during printing. [EMIM] + and [TCB] - It can form hydrogen bonds or ion-dipole interactions with PSS or PEDOT molecules in the ink, reducing the surface tension of the ink, thereby improving the wettability and spreadability of the ink on various substrates. This improved wettability not only prevents ink splashing or shedding during the printing process, but also ensures uniform ink coating, improving printing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a graph showing the contact angle change of the conductive ink provided in an embodiment of the present invention compared to the PEDOT:PSS dispersion.

[0032] Figure 2 Schematic diagram of the reaction mechanism of PEDOT:PSS and [EMIM][TCB] in an embodiment of the present invention.

[0033] Figure 3 Graph showing the change in resistance of the flexible transparent electrode prepared from the conductive ink of an embodiment of the present invention as a function of the mass percentage of [EMIM][TCB].

[0034] Figure 4 Graph showing the change in conductivity of the flexible transparent electrode prepared from the conductive ink of an embodiment of the present invention as a function of the mass percentage of [EMIM][TCB].

[0035] Figure 5 Graph showing the variation of light transmittance of a flexible transparent electrode prepared from the conductive ink of an embodiment of the present invention with the mass percentage of [EMIM][TCB].

[0036] Figure 6 Graph showing the stress-strain curve of a flexible transparent electrode prepared using the conductive ink of an embodiment of the present invention.

[0037] Figure 7 The conductivity change curve of the flexible transparent electrode prepared by the conductive ink of the embodiment of the present invention is placed under the accelerated aging conditions of 85% RH (relative humidity) / 60° C. for 24 hours. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

[0039] Example 1

[0040] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

[0041] The conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes provided in this embodiment has the following components by mass percentage: 60% PEDOT:PSS, 7.5% carboxylated carbon nanotubes, 20% 1-ethyl-3-methylimidazolium tetracyanoborate [EMIM][TCB], 5% polyacrylate, 2.5% salicylic acid, and 5% DMSO. The specific preparation steps are as follows:

[0042] Step 1: In 30mL, the concentration is 5mg·mL -1 To an ethanol dispersion of carboxylated carbon nanotubes (containing 0.15 g of carboxylated carbon nanotubes) were added 0.4 g of [EMIM][TCB] and 0.05 g of salicylic acid in sequence while stirring, and then ultrasonically dispersed uniformly. The mixture was then stirred at room temperature for 2 hours to obtain a mixed solution A.

[0043] Step 2: Filter a 1.5% PEDOT:PSS dispersion (with a PSS:PEDOT mass ratio of 2.5:1) in ethanol through a syringe filter. Add the filtered PEDOT:PSS dispersion (containing 1.2 g of PEDOT:PSS), 0.1 g of polyacrylate, and 0.1 g of DMSO to Mixed Solution A and stir at room temperature for 2 hours to obtain a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes. Testing showed that the ink obtained in this example had a room-temperature conductivity of 531 S / cm, a pH of approximately 5.5, and a viscosity of 2650 mPa·s.

[0044] Figure 1 This graph shows the contact angle change of the conductive ink provided in this example compared to a PEDOT:PSS dispersion. As can be seen, the conductive ink has a lower contact angle than the PEDOT:PSS dispersion, allowing for better spreadability on the substrate surface, resulting in a more uniform film. This reduces pinholes and cracks after printing, thereby reducing local resistance variations and improving overall film uniformity.

[0045] Figure 2 Schematic diagram of the reaction mechanism between PEDOT:PSS and [EMIM][TCB] in this example. Strong interactions between the hydrophilic cations of [EMIM][TCB] and the hydrophilic PSS, and between the hydrophobic anions and the hydrophobic PEDOT clusters, respectively, induce efficient ion exchange within the PEDOT:PSS. This induced structural change in the PEDOT chains, from a benzene-like structure to a quinone-like structure with a flatter chain conformation, promotes denser molecular packing. These microscopic changes promote carrier transport by enhancing charge carrier mobility and density, ultimately improving electrical conductivity.

[0046] By maintaining the same amounts of carboxylated carbon nanotubes, polyacrylate, salicylic acid, and DMSO, and the total amount of PEDOT:PSS and [EMIM][TCB], the amounts of PEDOT:PSS and [EMIM][TCB] were adjusted, thereby adjusting the mass percentages of PEDOT:PSS and [EMIM][TCB] in the ink. Conductive inks with varying mass percentages were spin-coated onto plasma-treated PI film. Pre-spinning at 500 rpm for 10 seconds spread the ink, followed by a main spin at 800 rpm for 30 seconds. Annealing at 80°C for 10 minutes evaporated the solvent, resulting in a uniform film layer and a flexible transparent electrode approximately 7.5 μm thick.

[0047] Figure 3 and Figure 4The following are graphs showing the resistance and conductivity of the flexible transparent electrode prepared by the conductive ink of this embodiment as a function of the mass percentage of [EMIM][TCB]. It can be seen that when the mass percentages of PEDOT:PSS and [EMIM][TCB] in the ink are 60% and 20%, respectively, the resistance of the ink is the smallest (843Ω) and the conductivity is the largest (1530S / cm).

[0048] Figure 5 This is a graph showing the change in the transmittance of the flexible transparent electrode prepared by the conductive ink of this embodiment with the mass percentage of [EMIM][TCB]. It can be seen that when the mass percentages of PEDOT:PSS and [EMIM][TCB] in the ink are 40% and 40%, the transmittance of the ink is the highest (86.2%).

[0049] Figure 6 3 is a stress-strain curve of a flexible transparent electrode prepared from the conductive ink of this embodiment, wherein the mass percentages of PEDOT:PSS and [EMIM][TCB] in the ink are 60% and 20% respectively. Figure 6 The tensile properties of the flexible transparent electrode prepared with conductive ink are shown: when the stretching rate reaches 7.5%, the stress peak is about 400 kPa (corresponding to the elongation at break), and then the stress drops slowly, indicating that the material maintains strong toughness within 7.5% deformation.

[0050] Figure 7 This graph shows the conductivity change of a flexible transparent electrode made with the conductive ink of this example after 24 hours of accelerated aging at 85% RH (relative humidity) and 60°C. The mass percentages of PEDOT:PSS and [EMIM][TCB] in the ink were 60% and 20% respectively. The initial conductivity was 1530 S / cm, and the values recorded every 6 hours were 1528.5 S / cm, 1525.4 S / cm, 1523.8 S / cm, and 1520.8 S / cm, respectively (a total decrease of only 0.6%).

[0051] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. Conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes, characterized in that: The conductive ink comprises the following components by mass percentage: 55-65% PEDOT:PSS, 7.5% carboxylated carbon nanotubes, 15-25% 1-ethyl-3-methylimidazolium tetracyanoborate [EMIM][TCB], 5% polyacrylate, 2.5% salicylic acid, and 5% DMSO. The conductive ink has a viscosity of 2000-3000 mPa·s.

2. The conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes according to claim 1, characterized in that: The components of the conductive ink are composed of 60% PEDOT:PSS, 7.5% carboxylated carbon nanotubes, 20% [EMIM][TCB], 5% polyacrylate, 2.5% salicylic acid, and 5% DMSO by mass.

3. The conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes according to claim 1, characterized in that: The mass ratio of PSS to PEDOT in the PEDOT:PSS is 2.5:

1.

4. A method for preparing a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: At a concentration of 5 mg mL -1 [EMIM] [TCB] and salicylic acid were added to the ethanol dispersion of carboxylated carbon nanotubes in sequence while stirring, and then ultrasonically dispersed uniformly, and then stirred at room temperature for 1 to 3 hours to obtain a mixed solution A; Step 2: Filter the ethanol dispersion of PEDOT:PSS with a mass concentration of 1-2% through a syringe filter; add the filtered ethanol dispersion of PEDOT:PSS, polyacrylate, and DMSO to the mixed solution A, and stir at room temperature for 1-3 hours to obtain a conductive ink based on PEDOT:PSS and carboxylated carbon nanotubes.

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