Preparation of a cellulose-based organotin polymer and its application in organic field effect transistors

Abstract

The application belongs to the technical field of organic field effect transistors, and particularly relates to preparation of a cellulose-based organotin polymer and application of the cellulose-based organotin polymer in organic field effect transistors. The application effectively breaks the dense hydrogen bond network in a crystal region by covalently grafting bulky and strong-polar organotin polyester side chains on a CNC skeleton, so that the intrinsic dielectric constant is increased from 6.0 to 15, and the dielectric loss is kept extremely low in a wide temperature range. An ultrathin amorphous SiO2 passivation layer is constructed on the surface of the modified CNC by a PHPS in-situ ultraviolet curing technology, so that the bottom layer of the polar trap is effectively isolated, and the pentacene semiconductor layer is induced to grow into a micron-sized and high-crystallinity large-size crystal grain. A high-performance and low-voltage-driven bio-based OFETs device is successfully prepared. In an extremely low driving working voltage, high carrier mobility, extremely low subthreshold swing and a high on-off ratio of up to 10 5 are achieved, and the practical application potential of the bio-based high-dielectric material in low-power-consumption OFETs is expanded.

Description

Technical Field

[0001] This invention belongs to the field of organic field-effect transistor technology, specifically relating to the preparation of a cellulose-based organotin polymer and its application in organic field-effect transistors. Background Technology

[0002] To address the increasingly serious problem of electronic waste and meet the needs of the electronics industry's sustainable transformation, the development of low-voltage driven organic field-effect transistors (OFETs) based on bio-based materials has become a cutting-edge research topic in the field. According to the device's operating principle, the key to reducing the driving voltage lies in significantly increasing the capacitance per unit area of ​​the gate dielectric layer.

[0003] Cellulose, as an abundant and inexpensive renewable polymer, possesses biodegradability and excellent film-forming properties and mechanical strength, making it one of the most promising next-generation bio-based dielectric materials with significant application potential in sustainable electronics. However, although the backbone of cellulose materials is rich in polar hydroxyl groups, its molecular chains form a dense and rigid network of hydrogen bonds, which restricts the orientation and polarization response of dipoles under an external electric field, resulting in its intrinsic dielectric constant typically remaining at a low level (k≈6). To improve the dielectric constant, traditional modification strategies often employ grafting strongly polar groups; however, this usually leads to extremely high dielectric losses.

[0004] Furthermore, applying cellulose to the gate dielectric layer of OFETs often presents interface challenges. On one hand, cellulose is typically rich in strongly polar hydroxyl groups, and their disordered arrangement at the dielectric / semiconductor interface leads to broadening of the energy state density at the semiconductor channel, inducing carrier localization and hindering charge transport. On the other hand, cellulose readily generates significant surface roughness during self-assembly, increasing interfacial scattering while disrupting the ordered crystallization of the overlying organic semiconductor film. These dual disadvantages result in devices fabricated using pure high-dielectric cellulose-based materials facing a dilemma where low threshold voltage and high carrier mobility are difficult to achieve simultaneously. To overcome these interface compatibility challenges, traditional interface modification methods (spin-coating a thicker low-dielectric polymer layer) often sacrifice capacitance, thereby weakening the low-voltage advantage of the underlying high-dielectric material.

[0005] Therefore, the technical problems to be solved by this invention are to develop a gate dielectric layer with both low leakage current and high dielectric constant, and to construct OFETs with low operating voltage, high carrier mobility and low hysteresis characteristics. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing a cellulose-based organotin polymer and its application in organic field-effect transistors (OFETs). This invention covalently grafts organotin polyester side chains with large steric hindrance and strong electronegativity differences onto a CNC backbone. By introducing metallic tin atoms, the molecular side chains construct local electric dipole centers. Simultaneously, the significant steric hindrance effect of the organotin polyester side chains weakens and breaks the originally rigid hydrogen bond network, giving the dipoles better orientation freedom without compromising the material's insulation properties, thereby achieving a leap in dielectric performance. Furthermore, this invention introduces an ultrathin, dense, all-hydrogenated polysilazane (PHPS) onto the modified CNC surface, followed by in-situ UV curing to generate an ultrathin, dense amorphous SiO2 passivation layer. Without reducing the capacitance of the insulating layer, this method achieves physical planarization of the cellulose rough interface and shielding against surface strong polar traps in one step, constructing OFETs with low operating voltage, high carrier mobility, and low hysteresis.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a cellulose-based organotin polymer, comprising the following steps: Step X1: Prepare CNC aqueous suspension by adding organic dicarboxylic acid monomer and dissolving it, then adding sodium hydroxide solution to neutralize carboxyl groups and activate reaction sites to form an aqueous phase system; Step X2: Prepare a tetrahydrofuran solution of dimethyltin dichloride as the organic phase system; Step X3: Under stirring conditions, the organic phase system is injected into the aqueous phase system to induce a condensation reaction at the oil-water interface. After the reaction is completed, the mixture is dialyzed with ultrapure water in a dialysis bag to obtain a modified CNC suspension. Step X4: Filter the modified CNC suspension through a microporous membrane and dry it to obtain the cellulose-based organotin polymer.

[0008] Furthermore, the organic dicarboxylic acid monomer is at least one of glutaric acid, 2-hydroxysuccinic acid, and 2,2-dimethylsuccinic acid.

[0009] Furthermore, in step X1, the mass fraction of the CNC aqueous suspension is 0.5-5%.

[0010] Furthermore, in step X3, the molecular weight cutoff of the dialysis bag is 14000 Da.

[0011] A second aspect of the present invention provides a cellulose-based organotin polymer prepared by the above-described preparation method.

[0012] A third aspect of the present invention provides an organic field-effect transistor, wherein the organic field-effect transistor utilizes the above-mentioned cellulose-based organotin polymer as a dielectric layer material.

[0013] A fourth aspect of the present invention provides a method for fabricating the above-described organic field-effect transistor, comprising the following steps: Step Y1, Substrate cleaning: The ITO conductive glass is ultrasonically cleaned in acetone, isopropanol and deionized water in sequence, then dried with nitrogen, baked and dried, and finally treated with oxygen plasma to obtain the treated ITO substrate. Step Y2, Preparation of dielectric layer: Disperse cellulose-based organotin polymer in deionized water to form a solution, then drop-coat it onto the treated ITO substrate, and vacuum dry it to form a dielectric layer film; Step Y3, preparation of passivation layer: prepare all-hydrogen polysilazane solution, coat it on the surface of dielectric layer film by spin coating, and then irradiate it under ultraviolet light source to form SiO2 film, which is the passivation layer film; Step Y4, Preparation of organic semiconductor pentacene: Deposit pentacene semiconductor on the surface of passivation layer thin film using chemical vapor deposition; Step Y5, Preparation of source and drain electrodes: The source and drain electrodes are prepared by vacuum evaporation.

[0014] Furthermore, in step Y2, the mass fraction of the solution is 0.5-5%.

[0015] Furthermore, in step Y2, the vacuum drying temperature is 25-80 ℃ and the time is 2-24 h.

[0016] Furthermore, in step Y3, the wavelength of the ultraviolet light source is 254 nm, the irradiation time is 1-48 h, and the distance from the light source is 1-20 cm.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention achieves a significant increase in dielectric constant and exhibits excellent temperature and frequency stability by covalently grafting organotin polyester side chains onto a CNC backbone. Experimental measurements show that although the grafted homopolymer itself is a low-dielectric material, the dielectric constant of the modified CNC film is significantly increased compared to CNC. Among them, the dielectric constant of CNC-gP (MDT Glu) is the highest, reaching 15. In addition, the modified sample exhibits excellent dielectric stability over a wide temperature range of 40 ℃ to 160 ℃, and loss peaks corresponding to α-relaxation of the side chains are observed in the 120 ℃ to 150 ℃ range.

[0018] (2) The grafted side chains of this invention form an effective molecular shielding layer on the CNC surface, which not only shields the hydrophilic hydroxyl groups but also cuts off the proton transport channels formed by hydrogen bond self-assembly. The desorption peak of bound water in the modified sample shifts to a lower temperature, and the desorption activation energy is significantly reduced from 83.26 kJ / mol in pure CNC to 42.82~72.49 kJ / mol. This indicates that the modification effectively weakens the strong hydrogen bond binding between cellulose and water molecules, and greatly suppresses the low-frequency conductivity loss caused by water.

[0019] (3) In this invention, a SiO2 passivation layer is generated on the cellulose surface by spin-coating and UV curing of the PHPS precursor. After interface passivation, the surface roughness Rq of the bilayer dielectric structure is significantly reduced to the range of 1.45-6.47 nm, while the surface changes from hydrophilic to hydrophobic, the water contact angle is greatly increased to 96°~103°, and the surface energy is reduced to 16~22 mN / m. This smooth and low surface energy interface promotes the growth of pentacene into highly ordered island-like grains with high density and micron-sized size, reducing the scattering and trapping of charge carriers by the grain boundaries.

[0020] (4) The leakage current density of the double-layer dielectric capacitor prepared by this invention is controlled at ±5 V voltage within 10. -7 A / cm 2 The following describes how, while effectively suppressing hysteresis and charge trapping, the bilayer device achieves 10 4 -10 5 With a high current on / off ratio, the overall carrier mobility jumps to 0.19-0.92 cm⁻¹. 2 ·V -1 ·s -1 .

[0021] (5) The chemical structure of the underlying cellulose in this invention plays a decisive role in the device performance. Specifically, the large nonpolar alkyl groups in the CNC-gP (MDT2.2-Dim) side chain provide significant steric hindrance, isolating the strongly polar hydroxyl groups on the cellulose backbone below the interface. This eliminates dipole disorder and charge traps at the interface, exhibiting optimal overall OFET performance, namely low subthreshold swing (1.21 V / dec), low drive voltage (-5.75 V), and high carrier mobility (0.921 cm⁻¹). 2 ·V -1 ·s -1 And an excellent on / off ratio (~10) 5 ). Attached Figure Description

[0022] Figure 1XPS C 1s, O 1s and Sn 3d high-resolution fitted spectra (a) and solid 13C CP / MAS NMR spectra (b) of the CNC-gP (MDT Glu) thin film prepared in Example 1, the CNC-gP (MDT2-Hyd) thin film prepared in Example 2 and the CNC-gP (MDT 2,2-Dim) thin film prepared in Example 3 (inset shows the chemical structure of the side chain groups and carbon atom numbering).

[0023] Figure 2 The polarizing microscope (POM) image (a), scanning electron microscope (SEM) image (b), and energy dispersive spectroscopy (EDS) image (c) of the CNC film prepared in Comparative Example 1, the CNC-gP(MDT Glu) film prepared in Example 1, the CNC-gP(MDT 2-Hyd) film prepared in Example 2, and the CNC-gP(MDT 2,2-Dim) film prepared in Example 3 are shown.

[0024] Figure 3 The thermogravimetric (TGA) weight loss curves (a) of the CNC film in Comparative Example 1, the CNC-gP(MDT Glu) film prepared in Example 1, the CNC-gP(MDT 2-Hyd) film prepared in Example 2, and the CNC-gP(MDT 2,2-Dim) film prepared in Example 3 are shown. The differential thermogravimetric (DTG) peak curve fitted by the Gaussian distribution function of the CNC film in Comparative Example 1 is shown in (b). The differential thermogravimetric (DTG) peak curve fitted by the Gaussian distribution function of the CNC-gP(MDT Glu) film prepared in Example 1 is shown in (c). The differential thermogravimetric (DTG) peak curve fitted by the Gaussian distribution function of the CNC-gP(MDT 2-Hyd) film prepared in Example 2 is shown in (d). The differential thermogravimetric (DTG) peak curve fitted by the Gaussian distribution function of the CNC-gP(MDT 2,2-Dim) film prepared in Example 3 is shown in (e).

[0025] Figure 4The dielectric constant as a function of frequency (a) and the dielectric loss tangent as a function of frequency (b) are shown for the CNC film prepared in Comparative Example 1, the Poly(MDT Glu) film prepared in Comparative Example 2, the Poly(MDT 2-Hyd) film prepared in Comparative Example 3, and the Poly(MDT 2,2-Dim) film prepared in Comparative Example 4. The dielectric constant as a function of frequency (c) and the dielectric loss tangent as a function of frequency (d) are also shown for the CNC film prepared in Comparative Example 1, the CNC-gP(MDT Glu) film prepared in Example 1, the CNC-gP(MDT 2-Hyd) film prepared in Example 2, and the CNC-gP(MDT 2,2-Dim) film prepared in Example 3 at room temperature. 5 The dielectric constant as a function of temperature at Hz (e) and 10 5 The spectrum of dielectric loss tangent at Hz as a function of temperature (f).

[0026] Figure 5 The image shows the double dielectric layer pentane OFETs device prepared in Example 4.

[0027] Figure 6 The diagram shows the structure of the double dielectric layer pentacene OFETs in Comparative Example 5, Example 4, Example 5 and Example 6 (a), the process of PHPS conversion to silicon dioxide and the molecular structure of Pentacene (b), the schematic diagram of charge traps at the unpassivated interface (c), and the smooth interface and mechanism after PHPS passivation (d).

[0028] Figure 7 Photographs (a) and (b) of the deionized water contact angle and ethylene glycol contact angle of the bilayer dielectric films in Comparative Examples 5, 4, 5 and 6.

[0029] Figure 8 AFM morphology (a) of the surface of the bilayer dielectric film in Comparative Example 5, Example 4, Example 5 and Example 6, AFM morphology (b) and X-ray diffraction pattern (c) of the Pentacene film grown on the PHPS passivation layer.

[0030] Figure 9 The electrical performance curves of SiO2 OFETs devices are shown in (a) and (b), and the electrical performance curves of SiO2 / OTS-based OFETs devices are shown in (c) and (d).

[0031] Figure 10The curves showing the relative permittivity of the bilayer dielectric film at different frequencies in Comparative Examples 5, 4, 5 and 6 are shown in (a), the capacitance per unit area as a function of frequency (b), the leakage current density as a function of applied voltage (JV) (c), and the capacitance per unit area as a function of bias voltage (CV) (d).

[0032] Figure 11 The transfer characteristic curves of the double-dielectric-layer pentacene OFETs device prepared in Comparative Example 5 (a), the transfer characteristic curve of the double-dielectric-layer pentacene OFETs device prepared in Example 4 (b), the transfer characteristic curve of the double-dielectric-layer pentacene OFETs device prepared in Example 5 (c), and the transfer characteristic curve of the double-dielectric-layer pentacene OFETs device prepared in Example 6 (d) are shown.

[0033] Figure 12 Output characteristic curves of the double-dielectric-layer pentacene OFETs device prepared in Comparative Example 5 (a), the double-dielectric-layer pentacene OFETs device prepared in Example 4 (b), the double-dielectric-layer pentacene OFETs device prepared in Example 5 (c), and the double-dielectric-layer pentacene OFETs device prepared in Example 6 (d).

[0034] Figure 13 The graphs show a comparison of mobility (a), on / off ratio (b), threshold voltage (c), and subthreshold swing (d) of the double-dielectric-layer pentane OFETs devices and SiO2 / OTS-based OFETs devices prepared in Comparative Examples 5, 4, 5, and 6.

[0035] Figure 14 The graph (a) shows the mobility and absolute value distribution of threshold voltage of the double dielectric layer pentacene OFETs devices prepared in Comparative Examples 5, 4, 5, and 6, and the graph (b) shows the evolution trend of working voltage and dielectric constant of the dielectric layer material of the field-effect transistor.

[0036] Figure 15 The curves showing the dielectric constant of the dielectric layer versus frequency, the capacitance per unit area versus frequency, the leakage current density of the dielectric layer versus bias voltage, and the capacitance per unit area versus bias voltage for the single dielectric layer pentacene OFETs devices of Comparative Examples 6, 7, 8, and 9 are shown in Figure 1.

[0037] Figure 16The transfer characteristic curves of the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 6 (a), the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 7 (b), the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 8 (c), and the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 9 (d) are shown.

[0038] Figure 17 Output characteristic curves of the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 6 (a), the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 7 (b), the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 8 (c), and the single-dielectric-layer pentacene OFETs device prepared for Comparative Example 9 (d). Detailed Implementation

[0039] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0041] Example 1: Preparation of CNC-gP (MDT Glu) Thin Film First, 10 mL of a 4 wt% CNC aqueous suspension was taken and diluted with an appropriate amount of deionized water to adjust the mass fraction to 2.5%. The suspension was then magnetically stirred to ensure uniform dispersion. Subsequently, approximately 2 mmol of glutaric acid was added to the suspension. After the monomers were fully dissolved, 4 mmol of NaOH solution was added dropwise to neutralize the carboxyl groups and activate the reaction sites, forming an aqueous phase system. Simultaneously, a tetrahydrofuran solution containing 0.439 g of dimethyltin dichloride was prepared as the organic phase. Under high-speed magnetic stirring, the organic phase solution was rapidly injected into the aqueous phase system to induce a condensation reaction at the oil-water interface. After the reaction stabilized, the resulting emulsion was transferred to a dialysis bag with a molecular weight cutoff of 14000 Da and dialyzed in ultrapure water for 5 days, with the water changed periodically to remove unreacted monomers, byproduct salts, and residual organic solvents. The obtained modified CNC suspension was then sealed and stored at 4 °C. A quantitative amount of modified CNC suspension was filtered through a microporous membrane, and then the wet membrane was carefully peeled off and air-dried at room temperature for 24 h to obtain a nanocomposite film sample with a smooth surface and uniform thickness, which is the CNC-gP(MDT Glu) film.

[0042] Example 2: Preparation of CNC-gP (MDT 2-Hyd) thin films Example 2 is based on Example 1, but glutaric acid is replaced with 2-hydroxysuccinic acid, and the rest is the same as in Example 1, to prepare CNC-gP (MDT 2-Hyd) film.

[0043] Example 3: Preparation of CNC-gP (MDT 2,2-Dim) thin films Example 3 is based on Example 1, but glutaric acid is replaced with 2,2-dimethylsuccinic acid, and the rest is the same as in Example 1, to prepare CNC-gP (MDT 2,2-Dim) film.

[0044] Comparative Example 1: Preparation of CNC Thin Films First, take 10 mL of a 4 wt% CNC aqueous suspension, add an appropriate amount of deionized water to dilute it to 2.5%, and use magnetic stirring to disperse it evenly. Then, filter it through a microporous membrane, and then carefully peel off the wet membrane and air dry it at room temperature for 24 h to obtain a nanocomposite film sample with a smooth surface and uniform thickness, which is the CNC film.

[0045] Comparative Example 2: Preparation of Poly(MDT Glu) Thin Films First, 2 mmol of glutaric acid and 4.2 mmol of sodium hydroxide were dissolved in 15 mL of deionized water to prepare a sodium salt solution of glutaric acid through an acid-base neutralization reaction. Then, under vigorous stirring with a magnetic stirrer, 10 mL of an aqueous solution containing 0.439 g of dimethyltin dichloride was rapidly poured into the above alkaline solution. A white flocculent precipitate formed instantly in the reaction system. High-speed stirring was continued for approximately 30 minutes to ensure complete polymerization. After the reaction, the solid product was collected by vacuum filtration through a Buchner funnel. To completely remove the byproduct sodium chloride and residual monomer, the mixture was washed alternately with large amounts of deionized water and anhydrous ethanol until the filtrate was neutral. The resulting white powder was transferred to a vacuum oven and dried continuously at 80 °C for 24 hours. 0.5 g of the dried polymer powder was weighed and dissolved in 9.2 mL of m-cresol solvent at a mass fraction of 5 wt%. The solution was stirred continuously at 60 °C for 12 hours to ensure dissolution until a homogeneous and transparent solution was formed. The solution was filtered using a 0.45 μm polytetrafluoroethylene syringe and then uniformly coated onto a stainless steel substrate using a drop casting method. Finally, the substrate was vacuum dried in a 100 °C vacuum oven for 12 h. After the substrate cooled naturally to room temperature, the film was peeled off to obtain a dielectric film of uniform thickness, which is the Poly(MDT Glu) film.

[0046] Comparative Example 3: Preparation of Poly(MDT 2-Hyd) Thin Films Comparative Example 3 was prepared by replacing glutaric acid with 2-hydroxysuccinic acid, while keeping the rest the same as Comparative Example 2, to obtain a Poly(MDT 2-Hyd) film.

[0047] Comparative Example 4: Preparation of Poly(MDT 2,2-Dim) Thin Films Comparative Example 4 was prepared by replacing glutaric acid with 2,2-dimethylsuccinic acid, while keeping the rest the same as Comparative Example 2, and obtaining Poly(MDT 2,2-Dim) film.

[0048] Test Example 1: Structure and Morphology Characterization To investigate the covalent grafting of organotin side chains onto CNC surfaces, solid-state NMR and XPS characterization were performed. The XPS C 1s, O 1s, and Sn 3d high-resolution fitted spectra of the CNC-gP (MDT Glu) film prepared in Example 1, the CNC-gP (MDT 2-Hyd) film prepared in Example 2, and the CNC-gP (MDT 2,2-Dim) film prepared in Example 3 are shown below. Figure 1 As shown in (a), after graft modification, CNC exhibits a clear Sn 3d characteristic double peak in the 485–500 eV region. Peak fitting of the C 1s high-resolution spectrum reveals a significant increase in peak intensity at 288.432 eV compared to pure CNC in the modified sample; this peak is attributed to the carbonyl carbon (OC=O) in the ester group. Correspondingly, in the O 1s high-resolution spectrum, besides the CO signal (532.903 eV) attributed to the cellulose matrix, a distinct carbonyl oxygen (O=C) characteristic peak appears at 531.830 eV. In the Sn high-resolution spectrum, all three materials exhibit highly symmetrical spin-orbit splitting double peaks, with binding energies at 486.99 eV and 495.45 eV, respectively. This indicates that Sn exists primarily in the +4 oxidation state, corresponding to the Sn-O bond. These results demonstrate that Poly(MDT(Glu, 2-Hyd, 2,2-Dim)) has been successfully covalently bonded to the cellulose backbone via esterification, forming a stable ester bond. The solid-state 13C CP / MAS NMR spectrum is shown below. Figure 1As shown in (b), it can be seen that in the three modified samples, not only were the characteristic signals of the cellulose skeleton clearly preserved at 105 ppm (C1), 84-89 ppm (C4), 71-75 ppm (C2, C3, C5), and 62-65 ppm (C6), but significant ester carboxyl carbon (C9, C=O) signal peaks were also observed in the 170-185 ppm region. This is consistent with the XPS conclusions, indicating that the linking group successfully constructed a covalent segment connecting the cellulose skeleton and the dimethyltin unit through esterification. The CNC-gP (MDT 2-Hyd) fraction exhibits a distinctive methylene carbon signal (C12) around 45-50 ppm, while the CNC-gP (MDT 2,2-dim) fraction shows an extremely strong side methyl signal at 20-30 ppm. In addition, the Sn-CH3 signal appearing around 0-15 ppm confirms that the tin-based complex maintained structural integrity during the grafting process.

[0049] To investigate the grafting effect of side chains and the film quality, the microstructure and EDS elemental analysis of organotin ester-grafted CNC films were performed. Polarizing microscope (POM) images of the CNC film prepared in Comparative Example 1, the CNC-gP (MDT Glu) film prepared in Example 1, the CNC-gP (MDT 2-Hyd) film prepared in Example 2, and the CNC-gP (MDT 2,2-Dim) film prepared in Example 3 are shown below. Figure 2 As shown in (a), the 20x polarized light microscope (POM) image clearly reflects the macroscopic crystallization behavior and transparency of the modified film. Pure CNC exhibits a unique chiral nematic phase colored birefringent texture. The CNC-gP (MDT 2-Hyd) film shows the clearest and most uniform field of view under POM, with no obvious grain aggregation or light scattering points, forming a uniform amorphous structure, which may be due to the effective suppression of the ordered arrangement of chain segments by the chiral centers in its molecular structure. The CNC-gP (MDT Glu) and CNC-gP (MDT 2,2-Dim) images show obvious graininess and disordered texture. The former may be attributed to its relatively symmetrical molecular structure, which is more likely to induce the formation of microcrystalline regions, thus causing light scattering, while the latter may be due to the huge steric hindrance leading to disordered chain segment stacking, forming larger aggregates. Scanning electron microscope (SEM) images are shown below. Figure 2As shown in (b), SEM images reveal the effect of grafting modification on the nanoscale morphology of CNC. Pure CNC exhibits a typical rod-shaped nanocrystal interleaved structure. CNC-gP (MDT 2-Hyd) retains the original rod-shaped morphology of CNC while filling the gaps between the rod-shaped CNCs. In contrast, CNC-gP (MDT 2,2-Dim) shows obvious irregular aggregates on its surface, and the original nanocrystal outline becomes blurred and thickened. The large steric hindrance of the material may hinder the regular arrangement of the grafted segments, thus manifesting as irregular segment aggregation at the nanoscale. Energy dispersive spectroscopy (EDS) images are shown below. Figure 2 As shown in (c), the comparison of EDS spectra shows that pure CNC only exhibits characteristic peaks of C, O elements and a small amount of S and Na elements remaining after hydrolysis. In all three modified materials—CNC-gP(MDT Glu), CNC-gP(MDT 2-Hyd), and CNC-gP(MDT 2,2-Dim)—a characteristic peak of tin was clearly observed at approximately 3.4 keV. EDS elemental analysis revealed that the atomic percentage of Sn in the modified materials was concentrated between 0.2 at% and 0.35 at%. The Sn atomic percentage exhibited a trend of CNC-gP(MDT 2,2-Dim) > CNC-gP(MDTGlu) > CNC-gP(MDT 2-Hyd). Poly(MDT 2-Hyd), due to its polar hydroxyl groups, readily undergoes intermolecular self-condensation side reactions, and its strong water solubility leads to a decrease in effective concentration at the water-tetrahydrofuran interface, resulting in the lowest Sn percentage. Poly(MDT Glu)... 2,2-Dim (2,2-Dim) achieves a relatively high grafting rate due to the strong hydrophobicity of its dimethyl group, its high effective concentration at the water-tetrahydrofuran interface, and its steric hindrance effect which effectively inhibits the hydrolysis of the intermediate.

[0050] Test Example 2: Thermal Stability and Dehydration Kinetics Analysis The thermogravimetric (TGA) weight loss curves of the CNC film in Comparative Example 1, the CNC-gP (MDT Glu) film prepared in Example 1, the CNC-gP (MDT 2-Hyd) film prepared in Example 2, and the CNC-gP (MDT 2,2-Dim) film prepared in Example 3, obtained by thermogravimetric analysis, are shown below. Figure 3 As shown in (a), the differential thermogravimetric (DTG) peak profile of the CNC thin film fitted with the Gaussian distribution function in Comparative Example 1 is as follows: Figure 3 As shown in (b), the differential thermogravimetric (DTG) peak profile of the CNC-gP (MDT Glu) thin film prepared in Example 1, fitted with the Gaussian distribution function, is as follows: Figure 3As shown in (c), the differential thermogravimetric (DTG) peak profile of the CNC-gP (MDT 2-Hyd) thin film prepared in Example 2, fitted with the Gaussian distribution function, is as follows: Figure 3 As shown in (d), the differential thermogravimetric (DTG) peak profile of the CNC-gP(MDT 2,2-Dim) thin film prepared in Example 3, fitted with the Gaussian distribution function, is as follows: Figure 3 As shown in (e), thermogravimetric analysis (TGA) reveals that the mass loss can be divided into three stages: stage f1 corresponds to the evaporation of physically adsorbed water, the second peak f2 corresponds to the desorption of bound water interacting with cellulose, and the third peak f3 is attributed to the initial thermal oxidative degradation of the sample. To further quantitatively analyze the interaction between water and cellulose, this study used the Ozawa-Flynn-Wall (OFW) method to calculate the activation energy of strong bound water desorption. Physically, the activation energy of bound water desorption is defined as the energy barrier that water molecules must overcome to detach from specific sites (hydroxyl groups / pores) in the cellulose skeleton. The high activation energy of CNC desorption (83.26 kJ / mol) reflects the strong hydrogen bond interaction between water molecules and cellulose hydroxyl groups, which not only firmly binds the conformation of the cellulose chain and restricts its movement but also provides a conductive channel for long-range proton transitions. However, after grafting CNC with organotin esters, the desorption peak of bound water in the DTG curve... A leftward shift occurred, indicating a decrease in desorption temperature, and the desorption activation energy calculated by the OFW method decreased significantly. Specifically, the desorption activation energy of CNC-gP(MDT Glu) was 72.49 kJ / mol, that of CNC-gP(MDT 2-Hyd) was 59.48 kJ / mol, and that of CNC-gP(MDT 2,2-Dim) was 42.82 kJ / mol. This reflects that the side chains introduced by grafting weakened the strong hydrogen bond network between cellulose and water.

[0051] Test Example 3: Dielectric Response Test To further investigate the effect of the introduction of organotin ester side chains on the dielectric properties of CNC films, the dielectric response of each film was tested under broadband electric field and varying temperature conditions. The dielectric constants of the CNC film prepared in Comparative Example 1, the Poly(MDTGlu) film prepared in Comparative Example 2, the Poly(MDT 2-Hyd) film prepared in Comparative Example 3, and the Poly(MDT 2,2-Dim) film prepared in Comparative Example 4 as a function of frequency are shown in the following figures. Figure 4 As shown in (a), the dielectric constant of CNC is approximately 6 at room temperature, while the dielectric constants of the three homopolymers (Poly(MDT Glu / 2-Hyd / 2,2-Dim)) are all around 2-4, reflecting that these polymers are typical low-dielectric materials. The dielectric loss tangent obtained from the test is shown in the spectrum as follows. Figure 4As shown in (b), CNC has a rigid rod-like structure with a high aspect ratio and a surface rich in hydroxyl groups. It readily self-assembles through hydrogen bonds to form proton transport channels that penetrate the film, resulting in significant conductivity loss. In contrast, Poly(MDT 2-Hyd) exhibits strong hygroscopicity due to its hydroxyl-rich molecular chains, easily inducing space charge polarization at low frequencies, leading to higher dielectric loss. Conversely, the homopolymers Poly(MDT Glu) and Poly(MDT 2,2-Dim) show extremely low dielectric loss, mainly attributed to the absence of hydrophilic hydroxyl groups in their side chains, making them less prone to space charge polarization under alternating electric fields and exhibiting low-loss characteristics. The dielectric constants of the CNC film prepared in Comparative Example 1, the CNC-gP(MDT Glu) film prepared in Example 1, the CNC-gP(MDT 2-Hyd) film prepared in Example 2, and the CNC-gP(MDT 2,2-Dim) film prepared in Example 3 at room temperature are shown in the following spectra. Figure 4 As shown in (c), the dielectric constant of CNC remains around 6 across the entire frequency range. However, the dielectric constant of CNC derivative films shows a significant jump, with CNC-gP (MDT Glu) exhibiting a dielectric constant jump to 15. Although the dielectric constant of the homopolymer itself is not high, grafting onto the CNC backbone achieves a 1+1>2 effect. This is mainly attributed to the fact that the grafted side chains not only introduce strongly polar Sn-O dipoles but also break the tight hydrogen bond network of cellulose through steric hindrance, increasing its free volume. This makes it easier for the polar groups and side chain dipoles on the cellulose backbone to undergo orientation polarization under an alternating electric field, thereby enhancing the dielectric. The dielectric loss tangent versus frequency spectrum at room temperature is shown in the figure. Figure 4 As shown in (d), it can be seen that the dielectric loss of CNC-gP (MDT Glu) at room temperature is higher than that of other modified samples. A larger MSD slope reflects more flexible cellulose chains and stronger mobility, resulting in more frequent orientation relaxation of the dipoles under an alternating electric field, thus exhibiting a larger dielectric loss value macroscopically. 10 5 The dielectric constant as a function of temperature at Hz is shown in the following graph. Figure 4As shown in (e), the dielectric constant of CNC increases with increasing temperature, mainly due to the increased polarization caused by higher temperatures, leading to higher polarizability. The dielectric constant of CNC increases significantly above 100 °C, primarily due to increased migration of residual ionic impurities (such as sulfate) on its surface, resulting in leakage losses. In contrast, the dielectric constant of the modified CNC does not change significantly with temperature within the test temperature range of 40-160 °C, exhibiting excellent thermal stability. This is attributed to the molecular shielding layer formed by the organotin ester side chains on the CNC surface. This structure not only protects the cellulose backbone and imparts good stability to the material, but also ensures that the polarization is mainly provided by the grafted side chains, avoiding dielectric abrupt changes caused by high-temperature carbonization. Specifically, the increase in dielectric constant of CNC-gP (MDT 2-Hyd) is limited because its side chains contain hydroxyl groups that can form internal hydrogen bonds, thus restricting dipole polarization. 5 The spectrum of dielectric loss tangent at Hz as a function of temperature is shown below. Figure 4 As shown in (f), the modified samples CNC-gP (MDTGlu) and CNC-gP (MDT 2-Hyd) exhibit lower dielectric loss than CNC at temperatures below 100 °C. The higher dielectric loss of CNC is attributed to the relaxation of the water dipoles. The grafted side chains replace and shield the hydrophilic hydroxyl groups on the cellulose surface, reducing water molecule adsorption and weakening the strong hydrogen bond between cellulose and water. Although the increased movement of water molecules at higher temperatures leads to shorter relaxation times, the modification significantly reduces the bound water content, thus suppressing the conductivity loss caused by water molecule relaxation and water molecules in the low-temperature region. When the temperature rises to 120-150 °C, all CNC derivatives show obvious dielectric loss peaks, corresponding to the α-relaxation behavior caused by the transition from the glassy state to the elastic state. Among them, CNC-gP (MDT 2,2-Dim) has the highest peak temperature, mainly due to the large steric hindrance generated by its dimethyl structure, which raises the activation energy barrier required to overcome intra-chain friction, thus causing the loss peak to shift to higher temperatures. In contrast, CNC-gP (MDT Glu) side chains exhibit greater flexibility and larger free volume, resulting in the lowest relaxation peak temperature. Furthermore, due to the dense internal hydrogen bond network restricting chain segment movement, the loss peak of CNC only shows a decreasing trend at approximately 180 °C, indicating a higher relaxation response temperature than cellulose derivatives.

[0052] Example 4: Fabrication of CNC-gP (MDT Glu) / PHPS double-dielectric-layer pentane-phenyl OFETs (1) Cleaning of the substrate Using tweezers, the edge of the ITO conductive glass was held and placed into a clean beaker. The substrate cleaning followed a step-by-step cyclic procedure: ultrasonic treatment was performed sequentially in acetone, isopropanol, and deionized water (resistivity 18.2 MΩ·cm), with each solvent cycled twice for 10 minutes each time to thoroughly remove surface contaminants. Subsequently, the substrate surface was dried using a high-purity nitrogen stream and baked on a 100 °C heating stage for 5 minutes. Finally, the sample surface was subjected to 20 minutes of ultraviolet treatment using an oxygen plasma cleaning system.

[0053] (2) Fabrication of dielectric layer The CNC-gP (MDT Glu) polymer prepared in Example 1 was dispersed in deionized water to prepare a 2.5 wt% solution. 100 μL of this solution was drop-coated onto the treated ITO substrate and then transferred to a vacuum drying oven and allowed to stand at 30 °C for 12 h until the solvent evaporated completely, forming a CNC film with uniform morphology.

[0054] (3) Preparation of passivation layer Using PHPS as the silicon source precursor, a 5% concentration solution was prepared: First, 50 μL of the 40% precursor stock solution was injected into a small sample vial, and 350 μL of ultra-dry dibutyl ether was added as a diluent. To prevent solvent evaporation, the vial opening was sealed with a sealing film, and the solution was continuously treated by shaking or using a magnetic stirrer for 15–30 min to ensure uniform solute distribution. Before use, the mixture was filtered through a 0.45 μm needle filter to remove minute impurities, ultimately yielding 400 μL of the target concentration solution. PHPS film formation was performed using a spin-coating method. The above solution was continuously spin-coated at 2000 rpm for 30 s, and the spin-coated film was then irradiated with a 254 nm ultraviolet light source (1 kW power) for 1 h at a fixed distance of 5 cm. Under this photochemical action, the Si-N and Si-H bonds in the PHPS molecule were converted into a SiO2 film through oxidation, hydrolysis, and condensation reactions.

[0055] (4) Preparation of organic semiconductor pentacene First, 15 mg of high-purity (99.999%) pentazocine powder was weighed and loaded into a thoroughly cleaned quartz evaporation boat. A substrate with a double dielectric layer was fixed onto the vacuum chamber frame. The vacuum was then pre-evacuated to 50 Pa using a mechanical pump, then switched to a gate valve to reduce the pressure to below 10 Pa. Finally, a molecular pump was used to further optimize the vacuum environment to 6.0 × 10⁻⁶ Pa. -4Below Pa. Turn on the substrate heating device and maintain a constant temperature of 50 °C for 10 min for degassing pretreatment. Once the organic source has reached steady-state evaporation, monitor the quartz crystal microbalance in real time, lock the deposition rate at 0.2 Å / s, and stop evaporation when the film thickness reaches 30 nm. After the evaporation source cools to room temperature, purge the chamber with nitrogen and remove the sample for later use.

[0056] (5) Fabrication of source and drain electrodes The prepared sample was transferred to the evaporation chamber, and the substrate was covered with a metal shadow mask (channel size 200 μm × 110 μm). The vacuum level was then reduced back to 6.0 × 10⁻⁶. -4 Metal deposition begins below Pa. Based on real-time readings from a quartz crystal microbalance, the deposition rate is controlled within the range of 0.5–0.7 Å / s until the film thickness reaches 30 nm. After deposition, the sample is cooled and allowed to stand in situ inside the chamber for 20 min to ensure the electrical stability of the electrode interface. The fabricated CNC-gP(MDT Glu) / PHPS double-dielectric-layer pentane-phenyl OFETs device is shown below. Figure 5 As shown.

[0057] Example 5: Fabrication of CNC-gP(MDT 2-Hyd) / PHPS double-dielectric-layer pentane-phenyl OFETs Example 5 is based on Example 4, but the material of the dielectric layer in step (2) is changed to the CNC-gP (MDT 2-Hyd) polymer prepared in Example 2. The rest is the same as in Example 4, and a CNC-gP (MDT 2-Hyd) / PHPS double dielectric layer pentacene OFETs device is prepared.

[0058] Example 6: Fabrication of CNC-gP (MDT 2,2-Dim) / PHPS double-dielectric-layer pentane-phenyl OFETs devices Example 6 is based on Example 4, but the material of the dielectric layer in step (2) is changed to the CNC-gP (MDT 2,2-Dim) polymer prepared in Example 3. The rest is the same as in Example 4, and a CNC-gP (MDT 2,2-Dim) / PHPS double dielectric layer pentacene OFETs device is prepared.

[0059] Comparative Example 5: Fabrication of CNC / PHPS double-dielectric-layer pentacene OFETs devices Comparative Example 5 is based on Example 4, but the material of the dielectric layer in step (2) is changed to pure CNC as in Comparative Example 1, and the rest is the same as in Example 4, to prepare a CNC / PHPS double dielectric layer pentacene OFETs device.

[0060] The device structure diagrams of the double dielectric layer pentacene OFETs in Comparative Example 5, Example 4, Example 5, and Example 6 are shown below. Figure 6 As shown in (a), the process of PHPS converting to silicon dioxide and the molecular structure of Pentacene are as follows: Figure 6 As shown in (b), a schematic diagram of charge traps at the unpassivated interface is as follows. Figure 6 As shown in (c), the smooth interface and mechanism of PHPS after passivation are as follows: Figure 6 As shown in (d), PHPS thin films were irradiated with 254 nm ultraviolet light at room temperature for 1 hour. The ultraviolet light broke the Si-N and Si-H bonds and excited the surrounding oxygen to generate O3 and O, initiating oxidative condensation and forming stable Si-O-Si bonds. This photochemical method transforms PHPS into a dense amorphous silicon dioxide layer. This passivation layer not only shields the polar traps of the underlying layer but also promotes the highly ordered growth of the upper pentacene layer.

[0061] Test Example 4: Test of Interface Characteristics of Double Dielectric Layer To further investigate the interface characteristics after passivation of the dielectric layer, contact angle measurements were performed on water and ethylene glycol. The deionized water contact angle photographs of the bilayer dielectric films in Comparative Example 5, Example 4, Example 5, and Example 6 are shown below. Figure 7 As shown in (a), the contact angle photograph of ethylene glycol is as follows: Figure 7 As shown in (b), the surface energy (γ) and its dispersion component (γᴰ) and polar component (γᴾ) of four CNC derivative / PHPS films were calculated using the Owens-Wendt method. The contact angle and surface energy of the four bilayer dielectric films are shown in Table 1 below.

[0062] Table 1. Contact angle and surface energy of four types of bilayer dielectric films After PHPS passivation, all four bilayer films exhibited hydrophobicity, with water contact angles ranging from 96° to 103°. Simultaneously, the calculated total surface energy of all four films was as low as 16-22 mN / m. This indicates that the PHPS passivation treatment enabled the cellulose dielectric layers with different functional groups to exhibit a unified physical interface, while simultaneously providing a low-surface-energy physical interface for the growth of the pentacene semiconductor. Specifically, according to Young's equation... (in , , These represent the surface energy of the dielectric layer, the surface energy of the semiconductor layer, and the interface energy, respectively. The interface energy is minimized when the surface energies of the two layers are close. The surface energy of pentacene is approximately 38 mN / m, with γᴰ being 37 mN / m and γᴾ being 1 mN / m. The surface energy of the bilayer dielectric layer is close to that of pentacene, which reduces the interface energy between pentacene and the dielectric layer, thereby promoting the crystallization and growth of the pentacene semiconductor layer.

[0063] To overcome the high surface roughness of monolayer cellulose derivative films, a PHPS layer was used to physically planarize the dielectric layer. AFM morphology images of the surfaces of the bilayer dielectric films in Comparative Example 5, Example 4, Example 5, and Example 6 are shown below. Figure 8 As shown in (a), the introduction of the PHPS layer significantly reduces the Rq of the bilayer dielectric structure to the range of 1.45-6.47 nm. The AFM morphology of the Pentacene film grown on the PHPS passivation layer is shown in Figure (a). Figure 8 As shown in (b), the image reveals that Pentacene exhibits an island-like growth pattern on the PHPS surface, forming a thin film composed of large, closely packed grains. The average size of the Pentacene reaches the micrometer scale, and the grain boundaries are tightly bound, meaning that the number of grain boundaries that charge carriers need to cross along the channel length is significantly reduced, providing a continuous, low-impedance channel for efficient hole carrier transport. The X-ray diffraction pattern of the Pentacene film grown on the PHPS passivation layer is shown below. Figure 8 As shown in (c), a set of extremely strong and sharp diffraction peaks are observed, located near 2θ~5.73°, 11.5°, and 17.3°, respectively, corresponding to the (001), (002), and (003) crystal plane diffraction of Pentacene crystals. This indicates that Pentacene adopts a highly oriented, upright arrangement on the PHPS surface, i.e., the long axis of the molecules is almost perpendicular to the substrate surface. The (001) peak has an extremely high intensity (~7500 au) and a very narrow full width at half maximum (FWHM), indicating that the Pentacene film deposited on the PHPS surface has extremely high crystallinity and long-range order. According to the Bragg equation 2dsinθ=nλ, the interlayer spacing corresponding to the (001) main peak is approximately 15.4 Å, a value that precisely matches the phase characteristics of the Pentacene film.

[123] Better intralayer π-π orbital overlap is beneficial for charge transport. Since the four bilayer dielectric films have similar low surface energies, pentacene can form high-quality, large-grain morphologies on its dielectric layer.

[0064] Test Example 5: Electrical Characteristic Testing of Double Dielectric Layer Pentylene OFETs Devices To objectively evaluate device performance, a mature silicon-based device was introduced as a control group to avoid interference from the instability of organic semiconductor film deposition processes on performance evaluation. Figure 9The transfer and output characteristics of devices with untreated SiO2 and OTS-modified SiO2 insulating layers are shown. The figures reveal that while the untreated SiO2 device exhibits a clear saturation region, its conductive channel is significantly suppressed by interface states. This is because the SiO2 surface originally contains a large number of polar silanol groups (Si-OH). These polar groups not only make the surface hydrophilic but also act as charge traps to capture charge carriers, limiting the on-state current of the device to 2.2 × 10⁻⁶. -6 The output current is around A, and the output curve exhibits certain contact resistance characteristics in the low VDS region. In contrast, after modification with an OTS self-assembled monolayer, the transfer characteristic curve becomes steeper, and the on-state current increases to 1.2 × 10⁻⁶. -5 The performance improved by nearly six times. Simultaneously, the output characteristic curves exhibited saturation characteristics and low ohmic contact resistance. This significant improvement is attributed to the hydrophobic interface formed by the long-chain alkyl groups of OTS, which not only effectively shields the underlying Si-OH traps but also induces high-quality vertical growth of Pentacene through surface energy matching. The fabrication of the OTS-SiO2 device demonstrates the reliability and high quality of the Pentacene vacuum evaporation process in this experiment, providing a reliable foundation for devices using bio-based cellulose as the dielectric material.

[0065] The relative permittivity variation curves of the bilayer dielectric films in Comparative Examples 5, 4, 5, and 6 at different frequencies are shown below. Figure 10 As shown in (a), each bilayer dielectric film maintains a high relative permittivity over a wide frequency range. Although the top PHPS is converted to SiO2 (ε... r (≈3.9), due to its extremely thin thickness, the high ε of the bottom modified fiber cords r Contributions (e.g., CNC-gP(MDT Glu) / PHPS≈18) are effectively preserved. The relationship between capacitance per unit area and frequency is shown in the curve. Figure 10 As shown in (b), the high ε r This value directly translates into high capacitance per unit area, providing a solid foundation for OFETs to achieve low operating voltage drive. The leakage current density versus applied voltage (JV) curve is shown below. Figure 10 As shown in (c), each double-layer structure sample exhibits excellent insulation performance, with a leakage current density stable at 10 Ω within a voltage range of ±5V. -7 A / cm 2 The following levels. Compared to the unpassivated dielectric layer, the transformation of PHPS into a dense inorganic SiO2 network effectively shields and isolates the residual strongly polar hydroxyl traps and physical defects on the surface of the underlying modified fiber strands, greatly improving the insulating integrity of the film. The relationship between areal capacitance and bias voltage (CV) is shown in the curve. Figure 10As shown in (d), the capacitance values ​​of each sample remained stable in the range of 1.0 V to 2.0 V, and no obvious voltage dependence was observed. When a voltage is applied to the gate, charge trapping or injection phenomena inside and at the interface of the cellulose composite dielectric layer are effectively suppressed, eliminating the hysteresis and threshold voltage drift phenomena commonly found in OFETs devices.

[0066] The transfer characteristic curves of the double-dielectric-layer pentacene OFETs device prepared in Comparative Example 5 are shown below. Figure 11 As shown in (a), the transfer characteristic curves of the double dielectric layer pentacene OFETs device prepared in Example 4 are as follows. Figure 11 As shown in (b), the transfer characteristic curves of the double dielectric layer pentacene OFETs device prepared in Example 5 are as follows. Figure 11 As shown in (c), the transfer characteristic curves of the double dielectric layer pentacene OFETs device prepared in Example 6 are as follows. Figure 11 As shown in (d), the on-state current of the devices all reaches 10. -6 A to 10 -5 Its magnitude is on the order of A, while its off-state current is stable at 10. -10 A to 10 -9 The extremely low level of A allows the current switching ratio of the device to reach 10. 4 -10 5 The order of magnitude of [value missing] achieves a high on / off ratio. The gate leakage current is significantly lower than the source leakage current across the entire operating voltage range, indicating that the double-layer dielectric structure of this invention possesses excellent insulation properties. The blue line in the figure (-I [value missing]) DS ) 1 / 2 As shown, the device exhibits good linearity in the saturation region, and the calculated carrier mobility increases to 0.19–0.92 cm⁻¹. 2 ·V -1 ·s -1 These results demonstrate that the top-layer PHPS (SiO2) passivation layer solves the problems of poor interface quality and severe leakage current in monolayer cellulose devices, thereby achieving high mobility and high on / off ratio.

[0067] The output characteristic curves of the double-dielectric-layer pentacene OFETs device prepared in Comparative Example 5 are shown below. Figure 12 As shown in (a), the output characteristic curve of the double dielectric layer pentacene OFETs device prepared in Example 4 is as follows. Figure 12 As shown in (b), the output characteristic curve of the double dielectric layer pentacene OFETs device prepared in Example 5 is as follows. Figure 12 As shown in (c), the output characteristic curve of the double dielectric layer pentacene OFETs device prepared in Example 6 is as follows. Figure 12 As shown in (d), after introducing the PHPS interface passivation layer, the curve at low V DSThe region exhibits a good linear relationship, indicating a low carrier injection barrier between the Au source / drain electrodes and the pentacene semiconductor layer, forming a high-quality ohmic contact. As V... DS With the increase of the saturation current, the current of the device can quickly enter the saturation region, and the curve is flat, with no signs of leakage current breaking down through the dielectric layer. This proves that the top-layer PHPS constructs a dense and trap-free semiconductor / dielectric layer interface, effectively suppressing the scattering and trapping of carriers by the polar groups at the interface. Compared with pure CNC / PHPS devices, devices based on CNC-gP(MDT2,2-Dim) / PHPS and CNC-gP(MDT 2-Hyd) / PHPS exhibit higher saturation current (IL) at the same gate voltage. DS (≈40 uA), which is attributed to the higher dielectric constant of the modified cellulose substrate enhancing the gate capacitive coupling capability, thereby inducing a high concentration of charge carriers in the channel.

[0068] The mobility comparison chart of the double-dielectric-layer pentane OFETs devices and SiO2 / OTS-based OFETs devices prepared in Comparative Examples 5, 4, 5, and 6 is shown in Figure 6. Figure 13 As shown in (a), the switching ratio comparison graph is as follows: Figure 13 As shown in (b), the threshold voltage comparison graph is as follows. Figure 13 As shown in (c), the subthreshold swing comparison diagram is as follows: Figure 13 As shown in (d), the fine-tuning effect of the underlying cellulose side chain chemical structure on device performance is illustrated. Figure 13 (a) and Figure 13 As shown in (c), the nonpolar side-chain modified samples, represented by CNC-gP(MDT2,2-Dim) and CNC-gP(MDT Glu), not only achieved high mobility (u≈0.89~0.92 cm⁻¹), but also... 2 ·V -1 ·s -1 Furthermore, its threshold voltage is as low as 5.8~8.3 V. This is mainly attributed to the large nonpolar alkyl groups in its side chain providing significant steric hindrance, effectively isolating the strongly polar hydroxyl groups on the cellulose backbone below the interface, thereby eliminating dipole disorder and charge traps at the interface. Figure 13 (d) The subthreshold swing (SS) data further confirmed this, with the CNC-gP(MDT 2,2-Dim) SS value as low as 1.21 V / dec, further confirming the reduced interfacial trap state density and significantly decreased carrier trapping effect during transport. In contrast, the strongly polar CNC-gP(MDT 2-Hyd) sample, due to the introduction of hydrophilic -OH groups into its side chains, while facilitating the formation of dense PHPS films, exhibits a large built-in electric field generated by the strong fixed dipole layer at the bottom, leading to a severe positive shift in the threshold voltage (V). th(≈30.7 V), its mobility is low (≈0.19 cm⁻¹). 2 ·V -1 ·s -1 However, as Figure 13 As shown in (b), it is precisely because the low dielectric constant of this material limits the off-state leakage current that CNC-gP (MDT 2-Hyd) achieves the highest on / off ratio (Ion / Ioff≈1.8×10⁻⁶). 5 ).

[0069] To comprehensively evaluate the overall performance of the cellulose-based bilayer dielectric layer of the present invention, its parameters were systematically summarized and compared with those of conventional dielectric materials and other cellulose-based dielectric layers in the prior art, as shown in Table 2 below.

[0070] Table 2. Performance comparison of OFETs between cellulose-based bilayer dielectric materials and conventional dielectric materials. Traditional nonpolar polymers (such as polymethyl methacrylate and polystyrene) can provide a good interface, maintaining carrier mobility in the range of 0.2–0.63 cm⁻¹. 2 ·V -1 ·s -1 However, due to its low dielectric constant, its areal capacitance is small, resulting in a generally high threshold voltage (8.5~15 V). On the other hand, unmodified pure CNC thin films in the prior art have a slightly higher ε... r The value is 6.0, but due to its rough surface and abundance of polar traps, the mobility of its monolayer device is extremely low (0.000152 cm⁻¹). 2 ·V -1 ·s -1 In contrast, by introducing a PHPS modification layer, the mobility of the unmodified CNC / PHPS device was improved to 0.759 cm⁻¹. 2 ·V -1 ·s -1 This effectively improved the surface defect problem of cellulose. Furthermore, the chemically modified CNC-gP(MDT Glu) / PHPS and CNC-gP(MDT 2,2-Dim) / PHPS exhibited dielectric constants of 14.0 and 12.0, respectively, and areal capacitances approaching 50 nF / cm². 2 Under the synergistic effect of the double-layer dielectric structure, the CNC-gP(MDT2,2-Dim) / PHPS dielectric layer device not only achieved a 0.921 cm⁻¹ dielectric layer, but also achieved a dielectric thickness of 0.921 cm⁻¹. 2 ·V -1 ·s -1The high mobility also reduces the threshold voltage to 5.75 V, which better balances the low voltage driving characteristics brought by high dielectric with the high mobility of charge carriers.

[0071] To more intuitively demonstrate the comparison between the device data of this invention and the prior art, the aforementioned core parameters are plotted as follows: Figure 14 The scatter plot shown illustrates the distribution and evolution trend of the points. (See attached image.) Figure 14 As shown in (a), the performance of the modified cellulose dielectric layers in Comparative Examples 5, 4, 5, and 6 of this invention was compared with similar materials reported in the prior art. The red circles represent the devices of this invention, which are mainly distributed in the upper left area of ​​the graph, indicating that the devices achieve both low threshold voltage and high carrier mobility, demonstrating superior overall performance compared to most reported cellulose-based dielectric layers. Furthermore, Figure 14 (b) Demonstrates the development trend of dielectric materials. The material of this invention successfully reduces the operating voltage of the device by increasing the dielectric constant, which is in line with the technical route of OFETs towards low voltage and low power consumption.

[0072] Comparative Example 6: Fabrication of CNC Single Dielectric Layer Pentylene OFETs Devices Comparative Example 6, based on Comparative Example 5, does not fabricate a PHPS passivation layer, thus forming a CNC single dielectric layer pentacene OFETs device.

[0073] Comparative Example 7: Fabrication of CNC-gP (MDT Glu) single-dielectric-layer pentaphenyl OFETs Comparative Example 7, based on Example 4, does not prepare a PHPS passivation layer, thus forming a CNC-gP (MDT Glu) single dielectric layer pentacene OFETs device.

[0074] Comparative Example 8: Fabrication of CNC-gP (MDT 2-Hyd) single-dielectric-layer pentaphenyl OFETs Comparative Example 8, based on Example 5, does not prepare a PHPS passivation layer, thus forming a CNC-gP (MDT 2-Hyd) single dielectric layer pentacene OFETs device.

[0075] Comparative Example 9: Fabrication of CNC-gP (MDT 2,2-Dim) single-dielectric-layer pentaphenyl OFETs Comparative Example 8, based on Example 6, does not prepare a PHPS passivation layer, thus forming a CNC-gP (MDT 2,2-Dim) single dielectric layer pentacene OFETs device.

[0076] Test Example 6: Electrical Characteristics Testing of Single-Dielectric-Layer Pentylene OFETs The dielectric constant of the dielectric layer as a function of frequency for the single-dielectric-layer pentacene OFETs devices of Comparative Examples 6, 7, 8, and 9 are shown in the figure below. Figure 15 As shown in (a), the capacitance per unit area varies with frequency as follows: Figure 15 As shown in (b), the dielectric layer leakage current density varies with the bias voltage as follows: Figure 15 As shown in (c), the curve of capacitance per unit area as a function of bias voltage is as follows: Figure 15 As shown in (d), the introduction of Sn-O bond side chains significantly increases the dielectric constant of CNC from 6 to 13–15, and the film capacitance per unit area increases from 2 nF cm⁻¹ of CNC. -2 Increased to 5~7 nF cm -2 For high-performance OFETs, the dielectric leakage current density is less than 10. -8 Up to 10 -7 A cm -2 This is a prerequisite for achieving a high switching ratio in the device. Although the sidechain reduces leakage current from 10% of the CNC... -5 Dropped to about 10 -7 A cm -2 However, it is still at the critical point for high-performance devices, and exhibits a trend of increased leakage current with increasing electric field. Furthermore, although the CV curve is at 10... 5 While the performance is stable at certain frequencies, the frequency dependence indicates that monolayer thin films still face issues of charge accumulation and polarization instability.

[0077] The transfer characteristic curves of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 6 are shown below. Figure 16 As shown in (a), the transfer characteristic curves of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 7 are as follows: Figure 16 As shown in (b), the transfer characteristic curves of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 8 are as follows: Figure 16 As shown in (c), the transfer characteristic curves of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 9 are as follows: Figure 16 As shown in (d), at the gate voltage V GS From 0 V to -10 V, the source and drain currents of each monolayer sample are only 10 V. -10 Up to 10 -8 Fluctuations between A and B. The switching modulation capability is extremely weak. (-I) DS ) 1 / 2 - V GSThe current curve not only lacks good linearity but also exhibits significant hysteresis. The difficulty in effectively increasing the current with the gate voltage is mainly attributed to the charge trapping effect caused by the polar hydroxyl groups on the dielectric layer surface. During gate voltage application, the polar hydroxyl groups at the interface not only act as dipoles interfering with carrier movement but also serve as deep traps for holes, causing some induced charges to be bound and unable to participate in conduction. This severe charge trapping effect directly leads to a weak on-state current, resulting in a significant reduction in the on / off ratio.

[0078] The output characteristic curves of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 6 are shown below. Figure 17 As shown in (a), the output characteristic curve of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 7 is as follows: Figure 17 As shown in (b), the output characteristic curve of the single-dielectric-layer pentacene OFETs device prepared in Comparative Example 8 is as follows: Figure 17 As shown in (c), the output characteristic curve of the single dielectric layer pentacene OFETs device prepared in Comparative Example 9 is as follows: Figure 17 As shown in (d), OFETs do not exhibit the standard current saturation region, I DS Only at 10 -9 The extremely low order of magnitude of A is likely due to the severe surface energy mismatch between the monolayer hydrophilic cellulose and pentacene. Pentacene, as a low surface energy (~38 mN / m) nonpolar semiconductor, easily forms island clusters on the relatively high surface energy and hydrophilic monolayer CNC surface, leading to discontinuous pentacene film grains and numerous grain boundaries that hinder hole carrier transport. Furthermore, the unshielded polar hydroxyl groups on the surface of the monolayer hydrophilic cellulose act as charge traps for hole carriers within the channel, weakening the dielectric layer's insulation withstand voltage capability. During device testing, the gate leakage current increased sharply and masked the channel field-effect current, causing the device to lose its field-effect amplification function.

[0079] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a cellulose-based organotin polymer, characterized in that, Includes the following steps: Step X1: Prepare CNC aqueous suspension by adding organic dicarboxylic acid monomer and dissolving it, then adding sodium hydroxide solution to neutralize carboxyl groups and activate reaction sites to form an aqueous phase system; Step X2: Prepare a tetrahydrofuran solution of dimethyltin dichloride as the organic phase system; Step X3: Under stirring conditions, the organic phase system is injected into the aqueous phase system to induce a condensation reaction at the oil-water interface. After the reaction is completed, the mixture is dialyzed with ultrapure water in a dialysis bag to obtain a modified CNC suspension. Step X4: Filter the modified CNC suspension through a microporous membrane and dry it to obtain the cellulose-based organotin polymer.

2. The preparation method according to claim 1, characterized in that, The organic dicarboxylic acid monomer is at least one of glutaric acid, 2-hydroxysuccinic acid, and 2,2-dimethylsuccinic acid.

3. The preparation method according to claim 1, characterized in that, In step X1, the mass fraction of the CNC aqueous suspension is 0.5-5%.

4. The preparation method according to claim 1, characterized in that, In step X3, the molecular weight cutoff of the dialysis bag is 14,000 Da.

5. A cellulose-based organotin polymer prepared by the preparation method according to any one of claims 1-4.

6. An organic field-effect transistor, characterized in that, The organic field-effect transistor uses the cellulose-based organotin polymer of claim 5 as the dielectric layer material.

7. A method for fabricating an organic field-effect transistor as described in claim 6, characterized in that, Includes the following steps: Step Y1, Substrate cleaning: The ITO conductive glass is ultrasonically cleaned in acetone, isopropanol and deionized water in sequence, then dried with nitrogen, baked and dried, and finally treated with oxygen plasma to obtain the treated ITO substrate. Step Y2, Preparation of dielectric layer: Disperse cellulose-based organotin polymer in deionized water to form a solution, then drop-coat it onto the treated ITO substrate, and vacuum dry it to form a dielectric layer film; Step Y3, preparation of passivation layer: prepare all-hydrogen polysilazane solution, coat it on the surface of dielectric layer film by spin coating, and then irradiate it under ultraviolet light source to form SiO2 film, which is the passivation layer film; Step Y4, Preparation of organic semiconductor pentacene: Deposit pentacene semiconductor on the surface of passivation layer thin film using chemical vapor deposition; Step Y5, Preparation of source and drain electrodes: The source and drain electrodes are prepared by vacuum evaporation.

8. The preparation method according to claim 7, characterized in that, In step Y2, the mass fraction of the solution is 0.5-5%.

9. The preparation method according to claim 7, characterized in that, In step Y2, the vacuum drying temperature is 25-80 ℃ and the time is 2-24 h.

10. The preparation method according to claim 7, characterized in that, In step Y3, the wavelength of the ultraviolet light source is 254 nm, the irradiation time is 1-48 h, and the distance from the light source is 1-20 cm.

Images