A photoresponsive triboelectric nanogenerator with an introduced charge transport confinement layer and its fabrication method

Abstract

This invention provides a photoresponsive triboelectric nanogenerator (TENG) with an introduced charge transport confinement layer and its fabrication method. The TENG includes a first substrate, a positive triboelectric layer, a negative triboelectric layer, an electrode layer, and a second substrate. A charge transport confinement layer, a mixed nanolayer of reduced graphene oxide and silver, is disposed between the negative triboelectric layer and the electrode layer to capture and confine interfacial charges. The positive triboelectric layer is an organic-inorganic perovskite film doped with a mixture of bismuth oxyiodide and carbon fluoride nanotubes; the negative triboelectric layer is a composite film of multi-walled carbon nanotubes / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide; and the charge transport confinement layer is a hybrid film of reduced graphene oxide / silver nanoparticles. This invention further broadens the triboelectric polarity and improves the electrical output characteristics of the TENG by controlling the interfacial charge.

Description

Technical Field

[0001] This invention belongs to the field of triboelectric nanogenerator technology, and specifically relates to a photoresponsive triboelectric nanogenerator with an introduced charge transport confinement layer and its preparation method. Background Technology

[0002] Triboelectric nanogenerators (TENGs) have advantages such as low cost, simple manufacturing process, and high conversion efficiency from mechanical energy to electrical energy. Their function is to convert low-frequency, low-amplitude mechanical energy in the environment, which is related to mechanics, electricity, optics, acoustics, and fluid dynamics, into electrical energy.

[0003] The basic working principle of TENG is as follows: When the positive and negative electrodes come into contact, the two thin films with significantly different electronegativity rub against each other. When the electrodes separate, they carry opposite charges, thus creating a potential difference. The back electrodes of these two materials are connected through a load, and the potential difference causes electrons to flow between the two electrodes to balance the electrostatic potential difference between the thin films. When the positive and negative electrodes re-appear, the potential difference generated by the frictional charge disappears, causing electrons to flow in the opposite direction. Through repeated contact and separation, an alternating current pulse signal is output from the output terminal, thereby generating output electrical energy.

[0004] Currently, innovative nanomaterials are widely used in TENG research. Due to their larger surface-to-volume ratio, innovative nanomaterials offer greater charge trapping capabilities. Charge trapping capability typically increases with increasing dielectric constant. Therefore, selecting nanocomposites with high dielectric constants is an ideal method to enhance the output electrical properties of TENGs. Among negative triboelectric electrode materials, polydimethylsiloxane (PDMS) is an excellent candidate for negative triboelectric layers due to its high negativeness, availability, high flexibility, and non-toxicity; polyvinylidene fluoride (PVDF) is often used to construct high-performance TENGs due to its easy formability, excellent dielectric properties, and significant ability to gain electrons. Among positive triboelectric electrode material candidates, perovskites are excellent dielectric materials due to their unique dielectric properties, excellent and stable electrical output performance, and adaptability to environmental changes, and are widely used in nanogenerators and light-emitting diode sensors.

[0005] Existing technologies related to TENG still have the following main problems:

[0006] 1. Due to the relatively small difference in electronegativity between the positive and negative triboelectric electrode materials of existing TENGs.

[0007] 2. The output electrical performance of a TENG primarily depends on the surface charge density of the triboelectric material. However, for existing TENGs, the triboelectric charge may decay on the surface of the triboelectric material and transfer to the interface between the triboelectric layer and the electrode, leading to a decrease in the triboelectric charge density and thus affecting the output electrical performance of the TENG. Summary of the Invention

[0008] In order to overcome the shortcomings of the prior art, the present invention aims to provide a photoresponsive triboelectric nanogenerator with an introduced charge transport confinement layer and its preparation method, so as to control the interface charge, further broaden the triboelectric polarity, and improve the electrical output characteristics of the TENG.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A photoresponsive triboelectric nanogenerator with an introduced charge transport confinement layer includes a first substrate, a positive triboelectric layer, a negative triboelectric layer, an electrode layer, and a second substrate. A charge transport confinement layer is disposed between the negative triboelectric layer and the electrode layer. The charge transport confinement layer is a mixed nanolayer of reduced graphene oxide and silver, used to capture and confine interfacial charges.

[0011] In one embodiment, the positive friction layer is an organic-inorganic perovskite film doped with a mixture of bismuth oxyiodide and fluorinated carbon nanotubes; the negative friction layer is a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite film; and the charge transport confinement layer is a reduced graphene oxide / silver nanoparticle hybrid film.

[0012] In one embodiment, in the positive friction layer, the doping ratio of fluorinated carbon nanotubes is 1.8-2.3 wt%; the doping ratio of bismuth oxyiodide nanoparticles is 4.8-5.3 wt%; in the negative friction layer, the doping ratios of polyvinylidene fluoride and titanium dioxide are both 1.8-2.3 wt%; the doping ratio of multi-walled carbon nanotubes is 14.5-15.5 wt%; and in the charge transport confinement layer, the mass percentage of reduced graphene oxide is 25%, and the mass percentage of silver nanoparticles is 75%.

[0013] In one embodiment, the multi-walled carbon nanotubes have an outer diameter of 20 nm and a length of 20 μm; the reduced graphene oxide has an average particle size range of 10-15 nm, and the silver nanoparticles have an outer diameter range of 20-30 nm.

[0014] In one embodiment, the thickness of the positive friction layer is 155-170 μm; the thickness of the negative friction layer is 135-155 μm; and the thickness of the charge transport confinement layer is 2.7-3.2 μm.

[0015] In one embodiment, the first substrate is an FTO glass plate, the electrode layer is a copper electrode, one side of the copper electrode is attached to the charge transport confinement layer, and the other side is set on a second substrate by foam tape, the second substrate is an acrylic plate; the first substrate and the second substrate are respectively fixed on the stator and mover of the linear motor.

[0016] The present invention also provides a method for fabricating the photoresponsive triboelectric nanogenerator with the introduced charge transport confinement layer, comprising the following steps:

[0017] Step 1: Prepare the positive friction layer and the negative friction layer;

[0018] Step 2, prepare the charge transport confinement layer, as follows:

[0019] Silver was cut to the nanoscale using a nanoframework, mixed and stirred with reduced graphene oxide, filtered and collected, and exfoliated to obtain a mixed nanolayer of reduced graphene oxide and silver.

[0020] Step 3, component assembly, as follows:

[0021] A charge transport confinement layer is attached between one side of the electrode layer and the negative friction layer; the positive friction layer and the other side of the negative friction layer are spaced apart; the first substrate and the second substrate are respectively fixed on the stator and the mover of the linear motor.

[0022] In one embodiment, the positive friction layer is an organic-inorganic perovskite thin film doped with a mixture of bismuth oxyiodide and carbon fluoride nanotubes, and its preparation process is as follows:

[0023] First, bismuth iodide nanoparticles were prepared.

[0024] Then, cesium iodide, lead chloride, and lead iodide were dissolved in dimethylformamide, and fluorinated carbon nanotube nanoparticles were added and stirred to obtain solution I; formamidinium hydroiodate and methyl iodide were dissolved in a mixture of isopropanol and dimethylformamide, and bismuth oxyiodide nanoparticles were added and stirred to obtain solution II;

[0025] Finally, solutions I and II were spin-coated onto the first substrate and annealed to obtain an organic-inorganic hybrid perovskite film doped with bismuth iodide and carbon fluoride nanotubes.

[0026] The negative friction layer is a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite film, and its preparation process is as follows:

[0027] First, multi-walled carbon nanotube particles, polyvinylidene fluoride nanoparticles, and titanium dioxide nanoparticles are added to a chloroform solution and stirred at low speed to disperse them evenly. Then, polydimethylsiloxane is added and stirred continuously until fully mixed. The chloroform is evaporated by ultrasonic treatment, and a curing agent is added. The mixture of multi-walled carbon nanotube particles, polyvinylidene fluoride nanoparticles, titanium dioxide nanoparticles, and polydimethylsiloxane is ultrasonically treated to remove air bubbles. Then, it is poured into the cavity formed by the polytetrafluoroethylene membrane and cured sequentially at 780℃~830℃ and room temperature to obtain a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite membrane.

[0028] In one embodiment, in solution I, the ratio of cesium iodide, lead chloride, lead iodide, and dimethylformamide is 20.2-20.7 mg: 66.8-67.2 mg: 626.5-627 mg: 1 mL; the mass percentage of fluorinated carbon nanotube nanoparticles is 1.8-2.3%. In solution II, the ratio of formamidinium hydroiodate, methyl iodide, isopropanol, and dimethylformamide is 89.2-90 mg: 200.2-200.7 mg: 3 mL: 30 μL; the mass percentage of bismuth oxyiodide nanoparticles is 4.8-5.3%.

[0029] In one embodiment, the charge transport confinement layer is fabricated as follows:

[0030] L-ascorbic acid was selected as the reducing agent. The L-ascorbic acid was added to the dispersion of graphene oxide and stirred vigorously. Then, the reduced graphene oxide was filtered and dried using PTFE to obtain reduced graphene oxide sheets on the PTFE membrane. The sheets were then cut using a nanoframework to control the average particle size range to 10-15 nm.

[0031] Sodium borohydride solution was added to silver nitrate powder to reduce silver ions to silver. The silver precipitate was collected and cut using a nanoframework to control its average outer diameter range of 20-30 nm.

[0032] The mass percentage of reduced graphene oxide was controlled at 25%, and the mass percentage of silver nanoparticles was controlled at 75%. After vigorous stirring, a stable RGO / AgNPs hybrid membrane was collected on a polytetrafluoroethylene membrane using a vacuum filtration device. The thickness of the RGO / AgNPs hybrid membrane was controlled at approximately 2.5-3.5 μm. The RGO / AgNPs hybrid membrane was then collected by peeling it off with a polytetrafluoroethylene scraper.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. The present invention adds a charge transport confinement layer between the negative friction layer and the electrode layer. The charge transport confinement layer is composed of reduced RGO and Ag mixed nanoparticles, which can cause the coupling effect of charge trapping and polarization enhancement at the interface, thereby improving the output electrical performance of TENG.

[0035] 2. The positive tribological layer material of this invention is an organic-inorganic perovskite thin film doped with a mixture of BiOI and FCNT nanoparticles, which can effectively improve the output electrical performance of the device, and the output is catalyzed by photocatalysis. The positive tribological electrode is based on organic-inorganic hybrid perovskite, and the surface charge density of TENG is effectively increased by using a high-k dielectric material. At the same time, the BiOI doped in the positive tribological electrode can respond to light radiation.

[0036] 3. To achieve a high dielectric constant while maintaining the flexibility of the polymer matrix, and to prevent a significant decrease in the breakdown strength and mechanical properties of the composite material due to increasing filler content, this invention adds a dielectric-conductive filler, MWCNT, to the PDMS / PVDF / TiO2 composite film. Adding MWCNT filler to the PDMS / PVDF / TiO2 polymer significantly enhances the polymer's dielectric constant, primarily attributable to the quantum tunneling effect and the Maxwell-Wagner polarization effect. The mechanism for improving the dielectric constant mainly involves charge accumulation at the interface between the MWCNT and the PDMS / PVDF / TiO2 composite film. Adding MWCNT facilitates the establishment of a conductive system in the composite material, thereby effectively increasing the dielectric constant and coefficient of friction of the negative triboelectric electrode, improving the tribological properties of the negative triboelectric electrode material, and thus significantly enhancing the output electrical performance. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the nanogenerator structure of the present invention.

[0038] Figure 2 This is a flowchart of the fabrication process of the nanogenerator of the present invention. Detailed Implementation

[0039] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0040] like Figure 1 As shown, this invention provides a photoresponsive triboelectric nanogenerator. Existing photoresponsive triboelectric nanogenerators mainly include a first substrate 1, a positive friction layer 2, a negative friction layer 3, an electrode layer 5, and a second substrate 7. The feature of this invention is the addition of a charge transport confinement layer 4 between the negative friction layer 3 and the electrode layer 5. The charge transport confinement layer 4 is a mixed nanolayer of reduced graphene oxide (RGO) and silver (Ag).

[0041] To control the interface charge, this invention introduces a charge transport confinement layer 4 in the TENG, which uses a mixture of RGO and silver nanoparticles. Its function is to capture and confine the interface charge, and it can play a synergistic role in capturing and blocking the charge at the interface; at the same time, the TENG exhibits photoresponse.

[0042] In an embodiment of the present invention, the positive friction layer 2 is an organic-inorganic perovskite film doped with a mixture of bismuth oxyiodide (BiOI) and carbon fluoride nanotubes (FCNT). The negative friction layer 3 is a composite film of multi-walled carbon nanotubes (MWCNT) / polydimethylsiloxane (PDMS) / polyvinylidene fluoride (PVDF) / titanium dioxide (TiO2). The charge transport confinement layer 4 is a reduced graphene oxide / silver nanoparticle hybrid film.

[0043] In this embodiment, a composite dielectric layer is constructed by simultaneously introducing highly electronegative organic filler PVDF and inorganic filler TiO2 into MWCNT-doped PDMS, thereby broadening the triboelectric polarity. The addition of both inorganic and organic fillers has a synergistic effect on improving the TENG electrical output characteristics.

[0044] Further, in the embodiments of the present invention, preferred doping ratios are given: In the positive friction layer 2, the doping ratio of fluorinated carbon nanotubes is 1.8-2.3 wt%; the doping ratio of bismuth oxyiodide nanoparticles is 4.8-5.3 wt%. In the negative friction layer 3, the doping ratios of polyvinylidene fluoride and titanium dioxide are both 1.8-2.3 wt%; the doping ratio of multi-walled carbon nanotubes is 14.5-15.5 wt%, wherein the outer diameter of the multi-walled carbon nanotubes is preferably about 20 nm, and the length is preferably about 20 μm. In the charge transport confinement layer 4, the mass percentage of reduced graphene oxide is 25%, and the mass percentage of silver nanoparticles is 75%, wherein the average particle size range of the reduced graphene oxide is preferably 10-15 nm, and the outer diameter range of the silver nanoparticles is preferably 20-30 nm.

[0045] Furthermore, in the embodiments of the present invention, preferred thickness parameters for the functional layers are given: the thickness of the positive friction layer 2 is 155-170 μm; the thickness of the negative friction layer 3 is 135-155 μm; and the thickness of the charge transport confinement layer 4 is 2.7-3.2 μm.

[0046] In this embodiment, controlling the thickness of the negative triboelectric layer 3 is crucial to ensure that the addition of organic and inorganic materials has no impact on the film thickness. The effect of its thickness on TENG performance is as follows: Initially, as the thickness of the negative triboelectric layer gradually increases, the generation of triboelectric charge gradually increases. However, when the layer thickness reaches a critical threshold, triboelectric charge will no longer be generated. From this point onward, as the film thickness increases, the electrostatic induction effect gradually weakens, leading to a decrease in total output. Therefore, the thickness of the negative triboelectric layer 3, i.e., the MWCNT / PDMS / PVDF / TiO2 film, should be controlled within a suitable range.

[0047] Furthermore, a thicker charge transport confinement layer 4 is not necessarily better, and the optimal ratio of the two materials in the charge transport confinement layer is 25% RGO and 75% silver nanoparticles. The explanation is as follows: Initially, as the RGO film gradually thickens, more triboelectric charges are captured. However, once a critical threshold is exceeded, as the RGO layer thickness continues to increase, the surface negative polarity of the negative triboelectric layer near the interface is continuously shielded, inhibiting charge transport. Therefore, the optimal thickness of the RGO / AgNPs layer is approximately 3 μm. The ratio of the two materials in the charge transport confinement layer is explained as follows: Due to the accumulation of charge at the interface between the two materials, strong polarization occurs in the interface region. Silver nanoparticles effectively enhance the dielectric properties of the hybrid layer, leading to an increase in output performance as the proportion of silver nanoparticles increases. With the enhanced dielectric properties of the RGO / AgNPs hybrid layer, the polarization charge density increases accordingly, significantly improving the output power of the TENG. However, when the mass percentage of AgNPs exceeds 75%, the output charge begins to decrease because the high dielectric enhancement obtained through AgNPs can only be achieved near percolation. Therefore, in the charge transport confinement layer, the proportion of RGO should be controlled at 25% and the proportion of silver nanoparticles at 75%.

[0048] In an embodiment of the present invention, the first substrate 1 is an FTO glass plate, the electrode layer 5 is a copper electrode, one side of the copper electrode is attached to the charge transport restriction layer 4, and the other side is set on the second substrate 7 by foam tape 6. The second substrate 7 is an acrylic plate. The first substrate 1 and the second substrate 7 are respectively fixed on the stator and mover of the linear motor.

[0049] Compared to ITO glass, FTO exhibits superior chemical stability across the entire pH range and is more suitable for deposition in solutions under non-neutral conditions. ITO, on the other hand, is relatively unstable at pH < 5. Therefore, the spin-coating substrate selected for the cathode material in this invention is FTO glass. For example, the area of ​​the controllable FTO glass plate is 4 × 4 cm. 2 The area of ​​the foam tape and acrylic substrate is also controlled to be 4×4cm. 2 This controls the effective contact area of ​​the positive and negative friction layer materials to be 4×4cm.2 .

[0050] Overall, to fabricate the photoresponsive triboelectric nanogenerator with the charge transport confinement layer introduced in this invention, some or all of the following materials may be required. This is because some materials in this invention can be purchased directly as finished products, or the initial materials can be prepared in-house. The complete list of materials is as follows:

[0051] Multi-walled carbon nanotubes (MWCNTs), polyvinylidene fluoride particles (PVDF), polydimethylsiloxane PDMS (A:B = 10:1), chloroform solution, titanium dioxide powder (Ti), graphene oxide (GO), L-ascorbic acid (L-AA), silver nitrate powder (AgNO3), sodium borohydride powder (NaBH4), fluorinated carbon nanotubes (FCNTs), bismuth nitrate pentahydrate powder (Bi(NO3)3·5H2O), potassium iodide powder (KI), lead iodide (PbI2), lead chloride (PbCl2), cesium iodide (CsI), dimethylformamide (DMF), isopropanol (IPA), methylamine iodide (MAI), formamidinium hydroiodate (FAI), anhydrous ethanol (CH3CH2OH), ethylene glycol ((CH2OH)2), copper tape (Cu), and fluorine-doped tin dioxide (FTO) conductive glass.

[0052] refer to Figure 2 The preparation method of the present invention mainly includes the following steps:

[0053] Step 1: Prepare the positive friction layer 2 and the negative friction layer 3;

[0054] Step 2, prepare charge transport confinement layer 4, as follows:

[0055] Silver was cut to the nanoscale using a nanoframework, mixed and stirred with reduced graphene oxide, filtered and collected, and exfoliated to obtain a mixed nanolayer of reduced graphene oxide and silver.

[0056] Step 3, component assembly, as follows:

[0057] The charge transport restriction layer 4 is attached between one side of the electrode layer 5 and the negative friction layer 3; the other side of the positive friction layer 2 and the negative friction layer 3 are spaced apart; the first substrate 1 and the second substrate 7 are respectively fixed on the stator and the mover of the linear motor.

[0058] In embodiments of the present invention, a more specific preparation process is provided, see reference. Figure 2 The positive friction layer 2 is an organic-inorganic perovskite thin film doped with a mixture of bismuth oxyiodide and carbon fluoride nanotubes. Its preparation process is as follows:

[0059] ①Preparation or purchase of BiOI nanoparticles: An embodiment of this invention provides a preparation process as follows:

[0060] BiOI was synthesized via a hydrothermal method using Bi(NO3)3·5H2O and KI as the bismuth and iodine sources, respectively. First, 1.5 g (0.004 mol) of Bi(NO3)3·H2O was added to 80 mL of ethylene glycol. The solution was stirred thoroughly at room temperature to obtain a white turbid liquid. Then, 0.5 g (0.003 mol) of KI was dissolved in 80 mL of deionized water and added dropwise to the white turbid liquid. With continuous stirring, a brick-red BiOI precipitate was obtained. The reagents and precipitate were then transferred to a 100 mL high-pressure hydrothermal synthesis reactor and treated at 165 °C for 24 h. The resulting product was filtered and washed three times with deionized water and anhydrous ethanol, respectively. It was then dried in a forced-air drying oven at 65 °C to obtain BiOI crystals. These crystals were then cut using a nanoframework to control the average particle size range of 12-15 nm.

[0061] ②Preparation of organic-inorganic hybrid perovskite thin films doped with bismuth oxyiodide (BiOI) and carbon fluoride nanotubes (FCNT)

[0062] Weigh CsI, PbCl2, and PbI2, dissolve them in DMF, add FCNT nanoparticles to make their mass percentage in the entire composite film 1.8-2.3%, preferably 2%, and stir at 75°C for 30 minutes, labeling it as Solution I; for example, the ratio of CsI, PbCl2, PbI2, and DMF is 20.2-20.7 mg: 66.8-67.2 mg: 626.5-627 mg: 1 mL; and more preferably 20.5 mg: 67 mg: 626.8 mg: 1 mL.

[0063] Weigh FAI, MAI, IPA and DMF, add BiOI nanoparticles to make their mass percentage in the entire composite membrane 4.8-5.3%, preferably 5%, and stir at room temperature for 1 hour, labeled as solution II; for example, the ratio of FAI, MAI, IPA and DMF is 89.2-90mg: 200.2-200.7mg: 3mL: 30μL, and more preferably 89.5mg: 200.5mg: 3mL: 30μL.

[0064] Solution I and solution II were spin-coated sequentially on the front side of the first substrate 1 and then annealed to obtain an organic-inorganic hybrid perovskite film doped with bismuth iodide and carbon fluoride nanotubes. For example, the spin-coating speed was 1500 rpm for 20 s, and the annealing was performed on a hot plate at 80°C for 40 min.

[0065] Compared to other traditional triboelectric materials, perovskites possess excellent piezoelectric properties, low-temperature processability, and good biocompatibility, as well as ferroelectricity. The organic-inorganic hybrid perovskite selected in this invention combines the advantages of both organic and inorganic perovskites, exhibiting excellent piezoelectric and triboelectric properties, superior charge transport capability, and high thermal stability, while also having relatively low production costs. Previous tests have shown that the organic-inorganic hybrid perovskite has a higher output voltage and better device stability. Therefore, the positive triboelectric layer material of this invention uses organic-inorganic perovskite as the base material for the positive triboelectric electrode.

[0066] To fully utilize solar energy and indoor lighting for TENG (Temperature Enzyme and Heat), this invention dops the positive tribological electrode with BiOI material. BiOI is a photocatalyst with visible light activity, belonging to the p-type narrow bandgap semiconductor family. This material absorbs visible light to enhance electrical output, responding in the visible light region by forming photogenerated charge carriers. BiOI has a unique layered crystal structure with the narrowest bandgap among the bismuth halides family, which facilitates the effective separation of photogenerated electrons. The positive tribological electrode material is selected for spin-coating on an FTO (Flame Metal Oxide) glass plate. When BiOI comes into contact with FTO, a built-in electric field is formed. This built-in electric field effectively promotes the separation of electron-hole pairs at the interface, effectively suppressing their recombination, thereby increasing the positive charge density of the positive tribological layer. The working mechanism of BiOI is as follows: When BiOI is irradiated, photogenerated charge carriers are generated. Under the condition of the built-in electric field, electrons move from BiOI to FTO, while a few charge carriers (holes) diffuse to the surface of BiOI, at which point the positive charge density on the BiOI surface increases. Because the MWCNT / PDMS / PVDF / TiO2 composite film, a triboelectric anode material, possesses strong charge trapping capabilities, when the positive triboelectric electrode and the MWCNT / PDMS / PVDF / TiO2 composite film come into contact under irradiation conditions, the available diffused charges on the BiOI surface readily transfer to the MWCNT / PDMS / PVDF / TiO2 composite film. Correspondingly, the remaining holes will remain on the BiOI surface, thereby increasing the number of holes in the positive triboelectric electrode. In summary, the incorporation of BiOI significantly enhances the absorption of visible light by the positive triboelectric electrode material, while simultaneously promoting charge separation and reducing the recombination probability of photogenerated carriers, thus constructing a light-enhanced TENG.

[0067] FCNTs appear as a powdery solid. Due to the relative inertness of the carbon nanotube (CNT) surface and its tendency to aggregate and entangle, they are difficult to disperse in a medium, thus greatly limiting their applications. Therefore, FCNTs were developed by surface modification of CNTs. FCNTs maintain their three-dimensional tubular structure while significantly altering their surface properties, conductivity, lubricity, and other characteristics. Because of their unique electrochemical properties, fluorinated carbon nanotubes show potential applications in sensors, piezoelectric devices, and chips.

[0068] To reduce the attenuation of charge on the electrode surface, embedding high-conductivity charge transport paths within the dielectric layer to rapidly transport accumulated charge to deeper layers is an ideal approach. In this invention, highly conductive FCNTs with high charge trapping capabilities are added to the organic-inorganic hybrid perovskite in the positive triboelectric electrode material. This provides charge transport paths to reduce surface charge loss, and the strongly polar fluorine groups in the FCNTs enhance the inductive properties of the triboelectric layer, thereby improving the conductivity of the positive electrode. When organic-inorganic hybrid perovskite doped with BiOI nanoparticles is mixed with an appropriate amount of conductive FCNTs, the change in dielectric properties is negligible, but the effective charge transport path value can be significantly reduced, thus effectively increasing the output power of the TENG. It should be noted that the thickness of the positive triboelectric electrode film needs to be controlled within the range of 155-170 μm.

[0069] The negative friction layer 3 is a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite film (MWCNT / PDMS / PVDF / TiO2 composite film), and its preparation process is as follows:

[0070] ①Preparation or purchase of TiO2 nanoparticles: An embodiment of this invention provides a preparation process as follows:

[0071] Using an in-situ pressurized inert gas method, Ti is first used as a raw material and subjected to resistance heating in a vacuum evaporator. The evaporated Ti is then introduced into helium (He) gas to form Ti microparticles, which are then deposited through a liquid nitrogen (N2) cooling rod. The cooling rod is then heated to room temperature, and oxygen (O2) is introduced to oxidize the titanium powder into TiO2 powder. This powder is collected by scraping it off with a polytetrafluoroethylene (PTFE) scraper, and then the TiO2 particles are cut using a nanoframework to obtain TiO2 nanoparticles with an average particle size range of 12-15 nm.

[0072] ②Preparation of MWCNT / PDMS / PVDF / TiO2 composite membrane:

[0073] MWCNT particles, PVDF nanoparticles, and TiO2 nanoparticles are added to a chloroform solution, with the mass percentage of MWCNT particles controlled at 14.5-15.5%, preferably 15%. Both the organic material PVDF and the inorganic material TiO2 can improve TENG power; the mass percentages of PVDF nanoparticles and TiO2 nanoparticles are controlled at 1.8-2.3%, preferably 2%. The mixture is stirred at a very low speed for about 45 minutes to achieve uniform dispersion. Then, polydimethylsiloxane is added and stirred continuously until fully mixed. PDMS is added according to the maximum solubility ratio. After approximately 30 minutes of ultrasonic treatment, the chloroform in the mixture is evaporated. Then, a curing agent is added; preferably, the weight ratio of the curing agent to PDMS is 1:10. The mixture of MWCNT particles, PVDF nanoparticles, TiO2 nanoparticles, and PDMS is ultrasonically treated for about 20 minutes to remove air bubbles. The mixture is then poured into a cavity formed by PTFE with a thickness of approximately 5 micrometers, thereby controlling the thickness of the composite film within the range of 135-155 micrometers. The membrane is cured in an oven at 780℃~830℃ (preferably 800℃) for about 2 hours, and then cured at room temperature for about 24 hours to obtain the MWCNT / PDMS / PVDF / TiO2 composite membrane.

[0074] PDMS is an excellent candidate for a negative triboelectric layer material due to its high electronegativity, high flexibility, and economic feasibility. However, the low dielectric constant of PDMS greatly limits its application in energy storage and electronic integrated devices. Therefore, developing PDMS composite materials with high dielectric constant and low dielectric loss can effectively power electronic devices and improve the triboelectric performance of TENGs. The negative triboelectric layer material of this invention is a MWCNT / PDMS / PVDF / TiO2 composite film. The negative triboelectric electrode of this invention is based on PDMS. For pure PDMS, the addition of the organic material PVDF is beneficial to enhancing triboelectric electronegativity, while the doping of the inorganic material TiO2 promotes strong electron capture of the negative electrode and can increase the dielectric constant, while also promoting the formation of the electroactive β phase PVDF. Furthermore, the addition of inorganic and organic fillers can have a greater synergistic enhancement effect on the amplification of TENG output.

[0075] Although PDMS itself possesses outstanding triboelectric properties, its electrical properties are expected to be further improved by introducing organic and inorganic fillers. Therefore, developing PDMS composite materials with high dielectric constants and low dielectric losses is a good approach to powering electronic devices and improving the triboelectric output of TENGs. Thus, to enhance the electronegativity of the negative tribological layer, the organic filler PVDF was introduced into PDMS. PVDF is an organic piezoelectric material with high electronegativity and corrosion resistance; it also facilitates charge trapping and storage. Therefore, adding PVDF helps to enhance the triboelectric negative electrode. Compared to pure PDMS, the triboelectric output performance of PVDF / PDMS can be effectively improved.

[0076] To further improve the electrical performance of the negative triboelectric electrode, this invention introduces TiO2 (optimal TiO2 doping ratio of 2 wt%), an inorganic filler with high dielectric properties, into the negative triboelectric electrode. As an n-type semiconductor, TiO2 possesses strong electron trapping and high dielectric constant properties. TiO2 acts as a charge trapping site, reducing surface discharge in air and promoting the formation of electroactive β-phase PVDF nanofibers. Therefore, TiO2 serves as an excellent charge trapping and electron transport material. During the preparation of the negative electrode triboelectric nanocomposite material, TiO2 exhibits good compatibility with PDMS / PVDF, effectively improving the output power of the TENG (Tribological Electrode Engraving).

[0077] Because the electronegativity difference between PDMS and positive triboelectric electrode materials is relatively small, this invention adds conductive filler MWCNT and highly electronegative PVDF as organic fillers to PDMS to broaden the triboelectric polarity. Simultaneously, inorganic filler TiO2 is added to construct a MWCNT / PDMS / PVDF / TiO2 composite dielectric layer. The simultaneous addition of inorganic and organic fillers has a synergistic enhancement effect on improving the electrical output characteristics of the triboelectric electrode (TENG).

[0078] In the embodiments of the present invention, the specific fabrication steps of the charge transport confinement layer 4 can be described as follows:

[0079] First, GO was ultrasonically treated in deionized water for 2 hours. Due to the strong ion absorption capacity of deionized water, clean and uniformly dispersed GO was obtained after ultrasonic treatment. Next, the RGO layer was prepared. L-AA was selected as the reducing agent and added to the GO dispersion with vigorous stirring. After thorough stirring, the RGO was filtered and dried on PTFE to obtain RGO sheets on the PTFE membrane. These sheets were then cut using a nanoframework to control the average particle size range of 10-15 nm. Next, AgNO3 was added to the container, and NaBH4 was slowly added. This step aimed to reduce Ag ions to generate Ag. The Ag precipitate was collected and cut using a nanoframework to control the average outer diameter range of 20-30 nm. Finally, an RGO / AgNPs hybrid layer was prepared, with the mass percentage of RGO controlled at 25% and the mass percentage of silver nanoparticles at 75%. After 12 hours of vigorous stirring, a stable RGO / AgNPs hybrid membrane can be collected on the polyPTFE membrane using a vacuum filtration device. The thickness of the RGO / AgNPs hybrid membrane is controlled to be approximately 2.5-3.5 μm. The RGO / AgNPs hybrid membrane is then collected by peeling it off with a PTFE scraper.

[0080] The output electrical performance of a triboelectric generator (TENG) primarily depends on the surface charge density of the triboelectric material. Therefore, two materials with the greatest possible difference in triboelectric properties should be selected to construct a high-performance TENG. However, since triboelectric charges may decay on the surface of the triboelectric material and transfer to the interface between the triboelectric layer and the electrode, the triboelectric charge density decreases, thus affecting the output electrical performance of the TENG. Therefore, to control the interface charge and improve the TENG's output, this invention employs a hybrid nanoparticle of RGO and silver as a charge transport confinement layer, which plays a synergistic role in capturing and blocking charges at the interface.

[0081] Before triboelectric charging, adding an RGO / AgNPs hybrid layer significantly reduces the surface potential of the MWCNT-PDMS / PVDF / TiO2 composite film, thereby enabling a larger triboelectric charging potential difference between the positive and negative triboelectric electrodes and exhibiting superior output electrical performance. This is due to the coupling effect of charge trapping and enhanced polarization at the interface caused by the RGO / AgNPs hybrid layer, which effectively improves the electrical output performance of TENG. On the one hand, the RGO / AgNPs hybrid layer traps charges at the interface, preventing interface electrons under the negative triboelectric layer from combining with positive charges; on the other hand, adding silver nanoparticles to RGO enhances the interfacial polarization between the silver nanoparticles and RGO, thereby increasing the dielectric strength of the hybrid and achieving the goal of enhancing triboelectric performance.

[0082] In embodiments of the present invention, the specific steps of device assembly can be described as follows:

[0083] Cut the MWCNT / PDMS / PVDF / TiO2 composite membrane into a suitable area, for example, 4×4cm. 2 The stripped RGO / AgNPs hybrid membrane was then attached to the MWCNT / PDMS / PVDF / TiO2 composite membrane, and then a 4×4cm area membrane was attached to it. 2 Copper tape was adhered to the RGO / AgNPs hybrid film. The copper tape can be directly used as a copper electrode. Then, a 4×4cm... 2 Apply foam tape to the back of the copper tape, then apply a 4×4cm piece of foam tape to the other side. 2 An acrylic substrate is used. The acrylic substrate at the bottom of the negative friction layer and the FTO glass substrate of the positive friction layer are fixed to the mover and stator of the linear motor, respectively. By adjusting the drive controller, the position, amplitude, and speed of the motor mover are controlled, thereby causing the positive and negative friction layers of the device to periodically contact and separate. The FTO and Cu electrodes of the device are connected to the test terminals of a multimeter with wires to measure the output electrical performance of the device. At this point, the assembly of the TENG is complete, and the measurement can be performed next.

Claims

1. A method for fabricating a photoresponsive triboelectric nanogenerator with an introduced charge transport confinement layer, wherein the photoresponsive triboelectric nanogenerator with an introduced charge transport confinement layer comprises a first substrate (1), a positive triboelectric layer (2), a negative triboelectric layer (3), an electrode layer (5), and a second substrate (7), characterized in that, A charge transport confinement layer (4) is disposed between the negative friction layer (3) and the electrode layer (5). The charge transport confinement layer (4) is a mixed nanolayer of reduced graphene oxide and silver, used to capture and confine interfacial charges. The preparation method includes the following steps: Step 1, prepare the positive friction layer (2) and the negative friction layer (3); The positive friction layer (2) is an organic-inorganic perovskite film doped with a mixture of bismuth oxyiodide and carbon fluoride nanotubes. Its preparation process is as follows: First, bismuth iodide nanoparticles were prepared. Then, cesium iodide, lead chloride, and lead iodide were dissolved in dimethylformamide, and fluorinated carbon nanotube nanoparticles were added and stirred to obtain solution I; formamidinium hydroiodate and methyl iodide were dissolved in a mixture of isopropanol and dimethylformamide, and bismuth oxyiodide nanoparticles were added and stirred to obtain solution II; Finally, solution I and solution II were spin-coated and annealed on the first substrate (1) to obtain an organic-inorganic hybrid perovskite film doped with bismuth iodide and carbon fluoride nanotubes. The negative friction layer (3) is a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite film, and its preparation process is as follows: First, multi-walled carbon nanotube particles, polyvinylidene fluoride nanoparticles, and titanium dioxide nanoparticles are added to a chloroform solution and stirred at low speed to disperse them evenly. Then, polydimethylsiloxane is added and stirred continuously until fully mixed. The chloroform is evaporated by ultrasonic treatment, and a curing agent is added. The mixture of multi-walled carbon nanotube particles, polyvinylidene fluoride nanoparticles, titanium dioxide nanoparticles, and polydimethylsiloxane is ultrasonically treated to remove air bubbles. Then, it is poured into the cavity formed by the polytetrafluoroethylene membrane and cured sequentially at 780℃~830℃ and room temperature to obtain a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite membrane. Step 2, prepare the charge transport confinement layer (4), as follows: Silver was cut to the nanoscale using a nanoframework, mixed and stirred with reduced graphene oxide, filtered and collected, and exfoliated to obtain a mixed nanolayer of reduced graphene oxide and silver. Step 3, component assembly, as follows: The charge transport restriction layer (4) is attached between one side of the electrode layer (5) and the negative friction layer (3); the positive friction layer (2) and the other side of the negative friction layer (3) are spaced apart; the first substrate (1) and the second substrate (7) are respectively fixed on the stator and the mover of the linear motor.

2. The preparation method according to claim 1, characterized in that, In solution I, the ratio of cesium iodide, lead chloride, lead iodide, and dimethylformamide is 20.2-20.7 mg: 66.8-67.2 mg: 626.5-627 mg: 1 mL; the mass percentage of fluorinated carbon nanotube nanoparticles is 1.8-2.3%. In solution II, the ratio of formamidinium hydroiodate, methyl iodide, isopropanol, and dimethylformamide is 89.2-90 mg: 200.2-200.7 mg: 3 mL: 30 μL; the mass percentage of bismuth oxyiodide nanoparticles is 4.8-5.3%.

3. The preparation method according to claim 1, characterized in that, The method for preparing the charge transport confinement layer (4) is as follows: L-ascorbic acid was selected as the reducing agent. The L-ascorbic acid was added to the dispersion of graphene oxide and stirred vigorously. Then, the reduced graphene oxide was filtered and dried using PTFE to obtain reduced graphene oxide sheets on the PTFE membrane. The sheets were then cut using a nanoframework to control the average particle size range to 10-15 nm. Sodium borohydride solution was added to silver nitrate powder to reduce silver ions to silver. The silver precipitate was collected and cut with a nanoframework to control its average outer diameter range of 20-30 nm. The mass percentage of reduced graphene oxide was controlled at 25%, and the mass percentage of silver nanoparticles was controlled at 75%. After vigorous stirring, a stable RGO / AgNPs hybrid membrane was collected on a polytetrafluoroethylene membrane using a vacuum filtration device. The thickness of the RGO / AgNPs hybrid membrane was controlled at 2.5-3.5 μm. The RGO / AgNPs hybrid membrane was then collected by peeling it off with a polytetrafluoroethylene scraper.

4. The preparation method according to claim 1, characterized in that, The positive friction layer (2) is an organic-inorganic perovskite film doped with bismuth oxyiodide and fluorinated carbon nanotube mixed nanoparticles; the negative friction layer (3) is a multi-walled carbon nanotube / polydimethylsiloxane / polyvinylidene fluoride / titanium dioxide composite film; the charge transport confinement layer (4) is a reduced graphene oxide / silver nanoparticle hybrid film.

5. The preparation method according to claim 4, characterized in that, In the positive friction layer (2), the doping ratio of fluorinated carbon nanotubes is 1.8-2.3wt%; the doping ratio of bismuth oxyiodide nanoparticles is 4.8-5.3wt%; in the negative friction layer (3), the doping ratios of polyvinylidene fluoride and titanium dioxide are both 1.8-2.3wt%; the doping ratio of multi-walled carbon nanotubes is 14.5-15.5wt%; in the charge transport confinement layer (4), the mass percentage of reduced graphene oxide is 25%, and the mass percentage of silver nanoparticles is 75%.

6. The preparation method according to claim 5, characterized in that, The multi-walled carbon nanotubes have an outer diameter of 20 nm and a length of 20 µm; the reduced graphene oxide has an average particle size range of 10-15 nm, and the silver nanoparticles have an outer diameter range of 20-30 nm.

7. The preparation method according to claim 1, 4, 5, or 6, characterized in that, The thickness of the positive friction layer (2) is 155-170 micrometers; the thickness of the negative friction layer (3) is 135-155 micrometers; and the thickness of the charge transport confinement layer (4) is 2.7-3.2 micrometers.

8. The preparation method according to claim 1, characterized in that, The first substrate (1) is an FTO glass plate, the electrode layer (5) is a copper electrode, one side of the copper electrode is attached to the charge transport restriction layer (4), and the other side is set on the second substrate (7) by foam tape (6). The second substrate (7) is an acrylic plate. The first substrate (1) and the second substrate (7) are respectively fixed on the stator and mover of the linear motor.

Images