Substrate-free flexible alternating current electroluminescent device and preparation method thereof
By modifying the PDMS substrate and using a substrate-free design, the heat dissipation and mechanical performance problems of traditional flexible ACEL devices are solved, achieving uniformity of AgNW electrodes and efficient heat dissipation of the device, making it suitable for wearable devices and flexible displays.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG TIANCHONG VEHICLE LAMP GROUP
- Filing Date
- 2025-11-28
- Publication Date
- 2026-04-10
AI Technical Summary
Traditional flexible AC electroluminescent devices suffer from heat dissipation and mechanical properties due to the presence of a substrate, leading to heat accumulation and shortened device lifespan. They are also difficult to apply in ultra-flexible scenarios. Furthermore, the electrode layer has a strong bond with the substrate when the substrate is removed, making it difficult to peel off.
Hydrophobic PDMS was used as a substrate. The PDMS surface was modified by a gradient coating of aminosilane coupling agent and polydopamine/polyethyleneimine. Combined with a silver nanowire coating of carboxylated cellulose nanocrystals, a substrate-free four-layer structure device was formed. The PDMS substrate was then removed by mechanical exfoliation.
It achieves uniform film formation of AgNW electrodes, reduces resistance non-uniformity, improves heat dissipation performance and mechanical flexibility of devices, and extends device lifespan, making it suitable for wearable devices and flexible displays.
Smart Images
Figure CN121843347A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of flexible electronic devices, and particularly relates to a substrate-free flexible alternating current electroluminescent device (ACEL) based on a silver nanowire (AgNW) transparent electrode and a preparation method thereof. BACKGROUND
[0002] With the rapid development of flexible electronic technology, alternating current electroluminescent (ACEL) devices have become a research hotspot in the field of next-generation flexible display and intelligent sensing due to their uniform cold light emission, low power consumption, ultra-thin characteristics, etc. The electronic structure of a flexible ACEL device is composed of a top electrode layer, a light-emitting layer, a dielectric layer and a bottom electrode layer. Since the four layers of the electronic structure of the flexible ACEL device are formed by solidifying liquid coatings, a substrate is needed to support the liquid raw materials during molding. After the processing of all the coatings of the device is completed, the substrate becomes part of the device as a substrate. However, the presence of the substrate will obviously affect the heat dissipation performance of the electronic structure layer. The thermal conductivity of the traditional PI / PET substrate is only 0.2 W / mK, and the Joule heat generated by the device is difficult to dissipate effectively, resulting in heat accumulation. High temperature environment will accelerate the diffusion of Cu atoms in the ZnS lattice, destroy the structure of the light-emitting layer, and thus shorten the service life of the device. In addition, the mechanical properties of the substrate also have a great influence on the mechanical properties of the device: for example, the Young's modulus of the flexible substrate (such as PET) is relatively high (about 2-4 GPa), which limits the application of the device in the field of ultra-flexible (such as stretchable electronics). For another example, the interfacial stress between the substrate and the functional layer is easy to cause interlayer peeling, reducing the reliability of the device.
[0003] It is not difficult to think that if the substrate can be removed after the device is processed and only the four layers of the solidified electronic structure layer are left, the heat dissipation effect of the device will be greatly improved, thereby effectively improving the service life of the device, and naturally avoiding the influence of the mechanical properties of the substrate on the mechanical properties of the device.
[0004] However, the conventional flexible ACEL device usually adopts polyethylene terephthalate (PET) or polyimide (PI) as a flexible substrate, the substrate has good hydrophilicity and good combination with the water-based coating AgNW ink as an electrode layer, the combination strength between the top electrode layer directly contacting with the substrate after the ACEL device is processed and formed is large, and it is difficult to peel the top electrode layer from the substrate perfectly. In view of the problem, the application selects hydrophobic PDMS (polydimethylsiloxane) as a substrate to reduce the combination strength between the substrate and the top electrode layer, and then the electronic structure layer is peeled from the substrate perfectly after the electronic structure layer is processed on the substrate. However, due to the hydrophobicity of PDMS, it is difficult for the water-based coating AgNW ink to form a very uniform film coating on the surface. This will result in poor uniformity of the electrode resistance (electrode sheet resistance non-uniformity NUF value > 25%). The non-uniformity of the sheet resistance will cause local hot spots during the operation of the device, accelerate the degradation of the material, and result in a short service life of the device with high brightness, which is difficult to meet the actual application requirements. SUMMARY
[0005] The application aims to provide a substrate-free flexible ACEL device and a preparation method thereof to solve the above problems in the prior art.
[0006] The application first provides a substrate-free flexible alternating current electroluminescent device, which comprises a four-layer structure, and the four-layer structure comprises, from a light-emitting side to a back light side, a top electrode layer, a light-emitting layer, a dielectric layer and a bottom electrode layer in sequence, characterized in that the top electrode layer is a silver nanowire (AgNW) coating added with carboxylated cellulose nanocrystals (CNC), and the light-emitting layer is a polymer matrix ZnS:Cu layer.
[0007] Further, the top electrode layer is formed by spraying and curing 1-5 mg / mL concentration of AgNW ink containing 0.8 wt% carboxylated cellulose nanocrystals on a PDMS substrate.
[0008] Further, the surface of the PDMS substrate for preparing the top electrode layer has a gradient coating of amino silane coupling agent (APTES) and polydopamine (PDA) / polyethyleneimine (PEI).
[0009] Optionally, the bottom electrode layer is a silver nanowire (AgNW) coating added with carboxylated cellulose nanocrystals (CNC).
[0010] For the above light-emitting device, the application further provides a preparation method, which comprises the following steps: Step 1, preparation and modification of the PDMS substrate: Step 1.1, PDMS film preparation: mix PDMS main agent (usually marked as component A on the package, mostly dimethylsiloxane), curing agent (usually marked as component B on the package, commonly used DBP (dibutyl phthalate)) and n-hexane in a mass ratio of 10:1:2, stir uniformly, coat on a clean glass surface, scrape the surface flat with a scraper (control the thickness to be 50-200 μm), and cure at 80°C for 2 hours to form a transparent and smooth PDMS film; Step 1.2, PDMS surface gradient chemical modification: Step 1.2.1, mix APTES and ethanol in a volume ratio of 1:1-1:4, spray on the surface of the PDMS film (droplet size 50-100 μm), cure at 90°C for 5-20 minutes, form a primer layer on the surface of the PDMS film to form an amino-functionalized surface; Step 1.2.2, mix PDA nanoparticles (particle size 50-200 nm) with a concentration of 1-3 mg / mL and 0.1-0.5wt% PEI, coat on the surface of the primer layer, crosslink at 60°C for 5-30 minutes to form a gradient hydrophilic surface; obtain a surface-modified PDMS substrate.
[0011] Step 2, device preparation: Step 2.1, top electrode layer preparation: spray 0.4-0.9wt% carboxylated CNC-containing AgNW ink (aspect ratio 200-1000) with a concentration of 1-5 mg / mL on the surface-modified PDMS substrate, cure at 80°C for 5-30 minutes to form a top electrode layer; Step 2.2, light-emitting layer preparation: mix ZnS:Cu powder (Cu doping concentration 1 mol%) with PB glue in a mass ratio of 1:1-1:2, print on the top electrode layer through a 100-400 mesh screen, and cure at 110°C for 5-20 minutes; Step 2.3, dielectric layer preparation: mix BaTiO3 powder (particle size 100-500 nm) with PB glue in a mass ratio of 1:1-1:2, print on the light-emitting layer through a 100-300 mesh screen, and cure at 110°C for 5-20 minutes, with a thickness of 10-20 μm; Step 2.4, bottom electrode layer preparation: prepare on the surface of the dielectric layer in the same process as the top electrode layer, or brush the conductive paste to form a bottom electrode layer.
[0012] Step 3, substrate-free peeling: Remove the PDMS substrate by mechanical peeling to obtain a self-supporting flexible ACEL device (device thickness <70 μm, bending radius <1 mm).
[0013] Advantages of the present application 1. By using an aminosilane coupling agent (APTES) and a gradient coating of polydopamine (PDA) / polyethyleneimine (PEI), a hydrophilic gradient PDMS surface is constructed, which significantly improves the wettability of AgNW ink and the film uniformity of the top electrode. This can reduce the sheet resistance non-uniformity of AgNW electrode from >25% to <10%, thereby eliminating local hot spots and greatly extending the continuous working life of high-brightness devices.
[0014] 2. Carboxylated cellulose nanocrystals (CNC) are introduced into AgNW ink to enhance the uniformity and mechanical stability of the AgNW network through hydrogen bonding. A more uniform AgNW network exhibits both higher resistance (leading to better conductivity) and higher transmittance (leading to higher light transmittance). Experiments show that the transmittance in the visible light range remains >85%.
[0015] 3. After the PDMS substrate is removed, the device exists in a self-supporting form. Compared to flexible devices on PET / PI substrates, the outer surface of the substrate-free device is covered with silver conductive electrodes, which facilitates heat exchange between the device and the air, promotes effective dissipation of Joule heat generated by the device, improves heat dissipation performance, and thus extends the device's lifespan. Simultaneously, it reduces the overall Young's modulus of the device (<1 MPa), achieving ultra-flexible characteristics. Experiments have shown that the device can withstand more than 1000 bending cycles (bending radius 1 mm), making it suitable for curved displays and wearable applications.
[0016] This invention solves the technical bottlenecks of uneven electrode film formation and thermal failure in traditional flexible ACEL devices through innovative surface modification technology and substrate-free structure design, significantly improving the light emission uniformity, thermal stability and lifespan of the device, and is applicable to wearable devices, flexible displays, smart lighting and other fields. Attached Figure Description
[0017] Figure 1 The figure shown is a comparison of the resistance non-uniformity (NUF) values of the samples obtained from Experiment 1-14 of the second experiment.
[0018] Figure 2 The transmittance spectrum of sample 4 is shown.
[0019] Figure 3 The figure shows the relationship between the brightness of the substrate-free ACEL device of the present invention and the brightness of the conventional PET-based ACEL device as a function of operating time. The figure (I0-I) / I0(%) represents the rate of change of brightness, where I0 is the initial brightness value and I is the real-time brightness value. Detailed Implementation
[0020] Example 1: Exploration of Preparation Conditions for Substrate PDMS In this invention, the first step in preparing the electroluminescent device is to prepare a PDMS substrate. The PDMS substrate is prepared by curing a main agent, a curing agent, and a suitable proportion of n-hexane. Specifically, the main agent and curing agent with different n-hexane contents are mixed evenly, poured into a clean glass bath, and the surface is smoothed with a scraper before being placed in an oven at 80°C for 2 hours for curing. However, the amount of n-hexane added significantly affects the leveling properties of the substrate. To obtain a PDMS substrate with uniform thickness, the effect of the n-hexane content in the PDMS formulation on the uniformity of the cured thickness was first tested. The PDMS composition consisted of 10 g of the main agent and 1 g of the curing agent (the ratio of main agent to curing agent was determined according to the manufacturer's instructions; commercially available PDMS typically uses a 10:1 ratio). Hexane content was set at 0 g, 1 g, 2 g, and 3 g. During the experiment, it was found that when the hexane content was 0 g and 1 g, the uncured PDMS had very poor fluidity, making it difficult to form a uniform thickness. When the hexane content was 3 g, the uncured PDMS was very thin and had high fluidity. When the hexane content was 2 g, the viscosity of the uncured PDMS was just right. By measuring the thickness of the cured PDMS at different locations, it was found that the cured PDMS had the most uniform thickness when the hexane content was 2 g.
[0021] Example 2: PDMS substrate surface modification experiment Experiment 1: A PDMS substrate and an electroluminescent device were prepared according to the following steps, denoted as Sample 1: (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0022] (2) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0023] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0024] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0025] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0026] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0027] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 1 was found to be 30%.
[0028] Experiment 2: A PDMS substrate and an electroluminescent device were prepared according to the following steps: the PDMS substrate was prepared, the surface of the PDMS substrate was modified, and the electroluminescent device was prepared. This was designated as Sample 2. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0029] (2) PDMS substrate surface modification: PEI was mixed with 2 mg / mL PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated onto the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate. (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0030] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0031] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0032] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0033] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0034] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 2 was found to be 24%.
[0035] Experiment 3: A PDMS substrate and an electroluminescent device were prepared according to the following steps: surface modification of the PDMS substrate and preparation of the electroluminescent device. This sample is designated as Sample 3. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0036] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:4, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0037] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0038] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0039] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0040] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0041] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0042] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 3 was found to be 18%.
[0043] Experiment 4: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This is designated as Sample 4. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0044] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0045] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0046] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0047] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0048] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0049] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0050] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 4 was found to be 6%.
[0051] Experiment 5: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This is designated as Sample 5. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0052] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:1, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0053] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0054] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0055] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0056] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0057] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0058] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 5 was found to be 9%.
[0059] Experiment 6: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This sample is designated as Sample 6. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0060] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0061] S2, a PEI solution with a mass percentage of 0.3 wt% is coated onto the surface of the base coating and crosslinked at 60°C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0062] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0063] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0064] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0065] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0066] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 6 was found to be 17%.
[0067] Experiment 7: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This is designated as Sample 7. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0068] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0069] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0070] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0071] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0072] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0073] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0074] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 7 was found to be 15%.
[0075] Experiment 8: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This sample is designated as Sample 8. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0076] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0077] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0078] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0079] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0080] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0081] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0082] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 8 was found to be 12%.
[0083] Experiment 9: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This sample is designated as Sample 9. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0084] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0085] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.1 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0086] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0087] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0088] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0089] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0090] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 9 was found to be 9%.
[0091] Experiment 10: A PDMS substrate and an electroluminescent device were prepared according to the following steps: the PDMS substrate was prepared, the surface of the PDMS substrate was modified, and the electroluminescent device was prepared. This was designated as Sample 10. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0092] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0093] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.2 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0094] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0095] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0096] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0097] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0098] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 10 was found to be 8%.
[0099] Experiment 11: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This sample is designated as Sample 11. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0100] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:2, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0101] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.5 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.8 wt% carboxylated CNC is sprayed and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0102] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0103] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0104] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0105] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0106] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 11 was found to be 11%.
[0107] Experiment 12: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This sample is designated as Sample 12. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0108] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:1, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0109] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.4 wt% carboxylated CNC is sprayed onto the substrate and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0110] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0111] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0112] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0113] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0114] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 12 was found to be 13%.
[0115] Experiment 13: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This is designated as Sample 13. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0116] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:1, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0117] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.6 wt% carboxylated CNC is sprayed onto the substrate and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0118] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0119] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0120] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0121] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0122] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 13 was found to be 10%.
[0123] Experiment 14: Prepare a PDMS substrate and an electroluminescent device according to the following steps: prepare the PDMS substrate, perform surface modification treatment on the PDMS substrate, and prepare the electroluminescent device. This is designated as Sample 14. (1) Preparation of PDMS substrate: Mix the main agent, curing agent, and n-hexane in a mass ratio of 10:1:2, stir until homogeneous, pour into a clean glass tank, and use a scraper to smooth the surface to ensure a smooth and uniform thickness. Then place it in an oven at 80°C for 2 hours to cure and obtain a PDMS substrate.
[0124] (2) PDMS substrate surface modification: S1. Mix APTES and ethanol at a volume ratio of 1:1, spray the mixture onto the surface of a PDMS substrate, control the droplet size to 50-100 μm, and then cure at 90°C for 8 minutes.
[0125] S2, PEI is mixed with PDA nanoparticles (particle size between 50-200 nm) at a mass percentage of 0.3 wt%, coated on the surface of the base coating, and crosslinked at 60 °C for 10 minutes to obtain a surface-modified PDMS substrate; (3) Preparation of transparent conductive films of silver nanowires: On a PDMS substrate, AgNW ink with a concentration of 2 mg / mL containing 0.9 wt% carboxylated CNC is sprayed onto the substrate and then cured at 80°C for 10 minutes to form a transparent conductive film of silver nanowires, which constitutes the top electrode.
[0126] (3) Fabrication of the light-emitting layer: The light-emitting layer mixture was prepared by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture was screen-printed onto the top electrode using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0127] (4) Dielectric layer fabrication: BaTiO3 and PB adhesive were mixed in a 1:1 mass ratio to obtain a dielectric layer mixture. The dielectric layer mixture was screen printed onto the light-emitting layer using a 150-mesh printing screen and then cured in an oven at 110°C for 10 min.
[0128] (5) Fabrication of the bottom electrode layer: A layer of conductive silver paste is screen-printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0129] (6) Peeling A certain pulling force is applied to the PDMS side to peel the PDMS substrate from the device, thereby obtaining substrate-free flexible ACEL device sample 1.
[0130] The resistance non-uniformity (NUF) of the silver nanowire thin film in the top electrode layer of sample 14 was found to be 11%.
[0131] The experimental parameters for experiments 1-14 above are listed below: Sample No. Volume ratio of APTES / ethanol Concentration of PDA Mass fraction of PEI Mass fraction of CNC Silver nanowire film resistance non-uniformity NUF value Sample 1 Untreated Untreated Untreated Untreated 30% Sample 2 Untreated 2 mg / mL 0.3 wt% 0.8 wt% 24% Sample 3 1:4 2 mg / mL 0.3 wt% 0.8 wt% 18% Sample 4 1:2 2 mg / mL 0.3 wt% 0.8 wt% 6% Sample 5 1:1 2 mg / mL 0.3 wt% 0.8 wt% 9% Sample 6 1:2 0 mg / mL 0.3 wt% 0.8 wt% 17% Sample 7 1:2 1 mg / mL 0.3 wt% 0.8 wt% 15% Sample 8 1:2 3 mg / mL 0.3 wt% 0.8 wt% 12% Sample 9 1:2 2 mg / mL 0.1 wt% 0.8 wt% 9% Sample 10 1:2 2 mg / mL 0.2 wt% 0.8 wt% 8% Sample 11 1:2 2 mg / mL 0.5 wt% 0.8 wt% 11% Sample 12 1:1 2 mg / mL 0.3 wt% 0.4 wt% 13% Sample 13 1:1 2 mg / mL 0.3 wt% 0.6 wt% 10% Sample 14 1:1 2 mg / mL 0.3 wt% 0.9 wt% 11% Reference Figure 1 Based on the table above, it can be concluded that the modification conditions of PDMS have a significant impact on the resistivity non-uniformity (NUF) of the subsequent silver nanowire thin films. Sample 4 exhibits the lowest NUF, at 6%, representing a substantial optimization of the NUF compared to Sample 1, which did not undergo any modification to the PDMS substrate. Figure 2 It can be further seen that the transmittance of the silver nanowire film in the visible light band of sample 4 is above 85%.
[0132] Example 3: Fabrication of Flexible ACEL Devices on PET Substrates Comparative samples were prepared following the traditional PET substrate flexible ACEL device fabrication steps: (1) Cut a PET substrate with a size of 10 cm*10 cm and a thickness of 125 μm; (2) Prepare an ethanol solution with a silver nanowire concentration of 2 mg / mL, spray it onto a PET substrate, and then cure it at 80°C for 10 minutes. (3) Preparation of the light-emitting layer: The light-emitting layer is made by mixing ZnS:Cu and PB adhesive in a 1:1 mass ratio. The light-emitting layer mixture is screen-printed onto the top electrode using a 150-mesh printing screen and cured in an oven at 110°C for 10 min.
[0133] (4) Dielectric layer preparation: The dielectric layer is prepared by mixing BaTiO3 and PB adhesive in a 1:1 mass ratio. The dielectric layer mixture is screen printed onto the light-emitting layer using a 150-mesh printing screen and cured in an oven at 110°C for 10 min.
[0134] (5) Preparation of bottom electrode layer: A layer of conductive silver paste is screen printed using a 300-mesh screen and then cured at 60°C for 10 minutes.
[0135] To test the influence of the substrate on the lifetime of the AC electroluminescent sheet, this invention tested the brightness variation over time of the comparative sample with a PET substrate prepared in Example 3 and the substrate-free flexible AC electroluminescent sheet sample 4 prepared in Example 2. Specifically, the brightness values of the two types of light-emitting sheets were measured every 20 minutes, where I0 is the original brightness value of the device and I is the real-time brightness value of the light-emitting sheet. The test results are as follows: Figure 3 As shown in the figure, compared with the traditional PET substrate flexible ACEL device, the working life of the substrate-free flexible ACEL device of the present invention is significantly improved, which further illustrates that the uniformity of the silver nanowire film and the substrate-free structure play an optimizing role in the working life of the device.
Claims
1. A substrate-free flexible AC electroluminescent device, characterized in that, The structure comprises a four-layer structure, wherein the four-layer structure consists of a top electrode layer, a light-emitting layer, a dielectric layer, and a bottom electrode layer, from the light-emitting side to the backlight side. The top electrode layer is a silver nanowire (AgNW) coating with added carboxylated cellulose nanocrystals (CNC), and the light-emitting layer is a polymer matrix ZnS:Cu layer.
2. The substrate-free flexible AC electroluminescent device according to claim 1, characterized in that, The top electrode layer is formed by spraying and curing silver nanowire (AgNW) ink containing carboxylated cellulose nanocrystals (CNC) onto a PDMS substrate.
3. The substrate-free flexible AC electroluminescent device according to claim 2, characterized in that, The top electrode layer is formed by spraying and curing AgNW ink containing 0.8 wt% carboxylated cellulose nanocrystals onto a PDMS substrate.
4. The substrate-free flexible AC electroluminescent device according to claim 1, characterized in that, The surface of the PDMS substrate used to prepare the top electrode layer has a gradient coating of aminosilane coupling agent (APTES) and polydopamine (PDA) / polyethyleneimine (PEI).
5. A method for fabricating a substrate-free flexible AC electroluminescent device, characterized in that, Includes the following steps: Step 1, PDMS substrate preparation and modification: Step 1.1, PDMS film preparation: Mix PDMS main agent, curing agent and n-hexane in a mass ratio of 10:1:2, stir evenly and coat it on a clean glass surface, smooth the surface with a scraper, and cure at 80°C for 2 hours to form a transparent and smooth PDMS film. Step 1.2, Gradient chemical modification of PDMS surface: Step 1.2.1: Mix APTES and ethanol at a volume ratio of 1:1 to 1:4, spray the mixture onto the PDMS membrane surface, and cure it at 90°C for 5-20 minutes to form a base coating on the PDMS membrane surface, thus forming an aminated surface. Step 1.2.2: PDA nanoparticles at a concentration of 1-3 mg / mL are mixed with 0.1-0.5 wt% PEI and coated onto the surface of the base coating. Crosslinking is performed at 60℃ for 5-30 minutes to form a gradient hydrophilic surface; a surface-modified PDMS substrate is obtained. Step 2, Device fabrication: Step 2.1, Preparation of top electrode layer: Spray AgNW ink with a concentration of 1-5 mg / mL containing 0.4-0.9 wt% carboxylated CNC onto a surface-modified PDMS substrate, and cure at 80℃ for 5-30 minutes to form the top electrode layer; Step 2.2, Light-emitting layer preparation: Mix ZnS:Cu powder and PB adhesive at a mass ratio of 1:1 to 1:2, and print the mixture onto the top electrode layer through a 100-400 mesh screen. Cur at 110℃ for 5-20 minutes. Step 2.3, Dielectric layer preparation: Mix BaTiO3 powder and PB adhesive at a mass ratio of 1:1 to 1:2, and print the mixture onto the light-emitting layer through a 100-300 mesh screen. Cur at 110℃ for 5-20 minutes, and control the thickness to 10-20 μm. Step 2.4, Preparation of the bottom electrode layer: Prepare the bottom electrode layer on the surface of the dielectric layer using the same process as the top electrode layer, or brush on a conductive paste to form the bottom electrode layer; Step 3, substrate-free peeling: A self-supporting flexible ACEL device is obtained by removing the PDMS substrate through mechanical peeling.
6. The method for fabricating a substrate-free flexible AC electroluminescent device according to claim 5, characterized in that, In step 1.1, when the scraper is leveling, the thickness of the mixture of main agent, curing liquid and n-hexane should be controlled to be 50-200 μm; In step 1.2.1, the droplet size of the APTES and ethanol mixture sprayed is 50-100 μm; Step 1.2.2: The particle size of the PDA nanoparticles is 50-200 nm; In step 2.1, the aspect ratio of the silver nanowires in the AgNW ink is 200-1000; In step 2.2, the Cu doping concentration in the ZnS:Cu powder is 1 mol% Step 2.3: The particle size of BaTiO3 powder is 100-500 nm.
7. The method for fabricating a substrate-free flexible AC electroluminescent device according to claim 5, characterized in that, In step 1.2.1, APTES and ethanol are mixed at a volume ratio of 1:
2.
8. The method for fabricating a substrate-free flexible AC electroluminescent device according to claim 5, characterized in that, In step 1.2.2, the concentration of PDA nanoparticles is 2 mg / mL and the weight percentage of PEI is 0.3 wt%.
9. The method for fabricating a substrate-free flexible AC electroluminescent device according to claim 5, characterized in that, In step 2.1, the AgNW ink has a concentration of 2 mg / mL and contains 0.8 wt% carboxylated CNC.
10. The method for fabricating a substrate-free flexible AC electroluminescent device according to claim 5, characterized in that, In step 2.2, ZnS:Cu powder and PB adhesive are mixed at a mass ratio of 1:1; in step 2.3, BaTiO3 powder and PB adhesive are mixed at a mass ratio of 1:1.