A transparent stretchable organic light emitting diode and a method of manufacturing the same

Abstract

The application discloses a kind of transparent stretchable organic light emitting diode and its preparation method, belong to flexible organic photoelectric device technical field, and include anode layer, hole transport layer, organic light emitting layer, electron transport layer and cathode layer in turn from bottom to top.The present application takes PDMS transfer conductive ink transfer printing process as core, by accurate control transfer printing template preparation, ink coating, pressure application, peeling speed and other parameters, realizes the lossless, high-precision transfer printing of transparent conductive electrode, effectively solves the problems of incomplete transfer printing, ink falling, pattern distortion and other problems existing in the present transfer printing process, and simultaneously combined with surface modification treatment, significantly improves the interfacial bonding force between electrode and PDMS substrate, organic functional unit, avoids interlayer peeling during stretching process.

Description

Technical Field

[0001] This invention relates to the field of flexible organic optoelectronic devices, and in particular to a transparent stretchable organic light-emitting diode and its fabrication method. Background Technology

[0002] Organic light-emitting diode (OLED) devices are widely used in the field of flexible displays due to their advantages such as self-illumination, high contrast, wide viewing angle, low power consumption, and thinness and flexibility. With the rapid development of industries such as wearable devices, flexible electronics, and transparent displays, high demands are being placed on the stretchability and transparency of OLED devices. Not only do the devices need to have a certain stretching deformation capability, but they also need to maintain stable photoelectric performance and mechanical reliability during repeated stretching, while having high light transmittance to meet the needs of transparent displays, semi-transparent interactive applications, and other scenarios.

[0003] Existing methods for fabricating transparent and stretchable OLED devices suffer from the following technical drawbacks: First, the flexible substrate lacks sufficient heat resistance and mechanical stability, making it difficult to withstand the high-temperature processes involved in OLED device fabrication (such as electrode deposition and organic layer evaporation). Furthermore, it is prone to breakage and deformation during stretching, affecting device lifespan. Simultaneously, the substrate's transparency is difficult to match with the electrode layer, leading to a decrease in overall device transmittance. Second, the electrode layer often uses traditional rigid conductive materials or ordinary transparent conductive materials, which are prone to cracking during stretching, resulting in decreased conductivity or even failure. Moreover, achieving both transparency and stretchability is difficult, and the electrode fabrication process is complex, especially... First, when using transfer printing technology, existing transfer methods are difficult to adapt to the transfer requirements of transparent conductive ink, and cannot achieve high-precision and high-consistency electrode pattern preparation. Second, the interfacial bonding force between the electrode and the flexible substrate and organic light-emitting layer is weak. In particular, when using PDMS transfer conductive ink transfer printing technology to prepare electrodes, problems such as incomplete transfer, conductive ink peeling, and electrode pattern distortion are prone to occur. When stretched, interlayer peeling is prone to occur, which damages the structural integrity of the device. Third, it is difficult to balance the flexibility, barrier performance and transparency of the encapsulation layer. It cannot effectively block the intrusion of water vapor and oxygen, resulting in the decay of the device's light-emitting performance and affecting the overall transparency of the device.

[0004] Polydimethylsiloxane (PDMS), as a high-performance polymer material, possesses excellent heat resistance, chemical stability, mechanical properties, and transparency, making it an ideal material for transparent, stretchable, and flexible substrates. Transparent conductive inks formulated with materials such as silver nanowires, Ag@Au core-shell nanowires, and transparent conductive polymers offer new avenues for the fabrication of transparent, stretchable electrodes due to their superior stretchability, conductivity stability, and transparency. However, effectively combining transparent conductive ink electrodes with flexible substrates and organic light-emitting layers through an efficient and precise PDMS transfer conductive ink transfer process—achieving non-destructive transfer, high-precision patterning, and good interfacial bonding while maintaining the device's transparency, stretchability, and photoelectric stability—remains a pressing technical challenge. Therefore, developing a method for fabricating transparent, stretchable organic light-emitting diodes (OLEDs) with high transparency, high stretchability, high photoelectric stability, and long lifespan, based on a PDMS transfer conductive ink transfer process, is of significant practical and industrial value. Summary of the Invention

[0005] The purpose of this invention is to address the technical defects in the existing transparent stretchable OLED device fabrication process, such as poor substrate compatibility, poor electrode transfer effect, weak interlayer bonding, and difficulty in balancing encapsulation performance and transparency, by providing a method for fabricating transparent stretchable organic light-emitting diodes.

[0006] Another object of the present invention is to provide a transparent stretchable organic light-emitting diode obtained by the above preparation method.

[0007] The technical solution adopted to achieve the purpose of this invention is: A method for fabricating a transparent, stretchable organic light-emitting diode includes the following steps: Step 1: After activating the substrate, perform hydrophobic treatment to obtain the pretreated substrate; Step 2: Patterned electrodes are fabricated on the upper surface of the pretreated substrate using transparent conductive ink; Step 3: Drop the degassed PDMS mixture onto the patterned electrode, then cure it, and peel off the substrate to obtain the anode layer or cathode layer. Step 4: A hole transport layer, an organic light-emitting layer, and an electron transport layer are sequentially spin-coated onto the upper surface of the anode layer to form an organic functional unit; Step 5: Apply pressure to the cathode layer and heat it to bond it to the organic functional unit to obtain a transparent stretchable organic light-emitting diode.

[0008] In the above technical solution, in step 1, the substrate is glass, quartz sheet or silicon wafer.

[0009] In the above technical solution, in step 1, the activation process of the substrate is as follows: the substrate is subjected to plasma surface activation treatment for 5-15 minutes and the power is 30-60W, so that active groups such as hydroxyl and carboxyl groups are formed on the substrate surface.

[0010] In the above technical solution, the hydrophobic treatment process in step 1 is as follows: octadecyltrichlorosilane is dropped onto the activated substrate surface, dried at a vacuum of -0.06 to -0.1 MPa and a temperature of 60-120°C for 2-4 hours, and then ultrasonically cleaned with ethanol and dichloromethane in sequence.

[0011] In the above technical solution, in step 2, the preparation process of the transparent conductive ink is as follows: using silver nanowires or Ag@Au core-shell nanowires as conductive fillers, using transparent elastic polymers as binders, adding dispersants and solvents, stirring evenly, and then using ultrasonic dispersion treatment to obtain uniformly dispersed transparent conductive ink; wherein, the mass fraction of conductive fillers is 5%-15%, the mass fraction of binders is 10%-20%, the mass fraction of dispersants is 1%-3%, and the remaining amount is solvent, ensuring that the transparent conductive ink has excellent transparency, stretchability, and printability, and is suitable for PDMS transfer printing process.

[0012] In the above technical solution, in step 2, a patterned electrode is prepared on the substrate surface using a scraping process.

[0013] In the above technical solution, in step 4, the anode layer is first subjected to surface activation treatment, and then spin-coated to prepare organic functional units. The specific process is as follows: plasma surface activation treatment is performed in a mixed gas of oxygen and / or argon (volume ratio of 4:1-2:1) for 5-15 minutes and power of 80-120W, so that active groups such as hydroxyl and carboxyl groups are formed on the substrate surface, thereby improving the hydrophilicity of the surface.

[0014] In the above technical solution, the hole transport layer is prepared in step 4 as follows: PEDOT:PSS is spin-coated onto the anode layer at a spin speed of 3000-4000 rpm for 1-3 min, and the annealing temperature is 60-120℃ for 10-20 min.

[0015] In the above technical solution, the preparation process of the organic light-emitting layer in step 4 is as follows: spin-coating a super yellow solution onto the hole transport layer, wherein the concentration of the super yellow solution is 3-8 mg / ml, the super yellow solution is a mixed solution of super yellow and a solvent, wherein the solvent is toluene, chlorobenzene or tetrahydrofuran, the spin-coating speed is 2000-3000 rpm, the spin-coating time is 1-3 min, the annealing temperature is 60-120℃, and the annealing time is 10-20 min.

[0016] In the above technical solution, in step 4, the electron transport layer is prepared using a mixture of poly[9,9-bis[3-(ethyldimethylamino)propyl]-9',9'-dioctyl[2,2'-bis-9H-fluorene]-7,7'-dimethyldibromide and ethoxylated polyethyleneimine in a mass ratio of 10:1-15:1, with methanol or ethanol as the solvent. The concentration of the mixture is 2-5 mg / ml. The spin coating speed is 2000-3000 rpm, the spin coating time is 1-3 min, the annealing temperature is 60-120℃, and the annealing time is 10-20 min. The organic functional unit uses a transparent flexible light-emitting polymer to ensure that the organic functional unit has excellent transparency and stretchability, is compatible with the anode layer and subsequent cathode layer, and does not affect the overall light transmittance of the device.

[0017] In the above technical solution, in step 3, the PDMS mixture is a mixture of PDMS prepolymer and curing agent at a mass ratio of 10:1-15:1. Vacuum degassing is used to remove air bubbles from the mixture. The degassing time is 15-30 min, the vacuum degree is -0.08~-0.1 MPa, the thickness of the anode layer or cathode layer is 100-200 μm, the curing temperature is 80-120℃, and the curing time is 1-2 h.

[0018] In the above technical solution, in step 5, the pressure applied is 0.05-0.1 MPa to prevent the organic functional unit from being damaged by pressure, and the heating temperature is 50-70℃ to make the cathode layer and anode layer fit together tightly.

[0019] Another aspect of the present invention includes a transparent stretchable organic light-emitting diode obtained by the preparation method, which, from bottom to top, comprises an anode layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, and a cathode layer.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention addresses the core pain points of existing transparent stretchable organic light-emitting diode (OLED) fabrication technologies by innovating a PDMS transfer conductive ink transfer process. This not only solves the performance defects of single-structure devices but also achieves a synergistic improvement in overall device performance through the synergistic effect between the PDMS transfer conductive ink electrodes (cathode and anode layers) and organic functional units. Compared with existing technologies, it possesses the following significant advantages. Furthermore, the core logic of the synergistic effect of each layer is explained through a mechanistic analysis, providing solid technical support for realizing subsequent economic and social benefits. Specifically, these include: 1) This invention addresses the core pain points of electrode layer transfer, improving transfer effect and accuracy, and achieving synergistic adaptation between the electrode layer and the substrate. The specific synergy and mechanism are as follows: This invention adopts a synergistic design of "interface modification + transfer parameters" to construct an efficient transfer system. First, by utilizing the excellent flexibility, surface inertness, and material compatibility of PDMS material, a seamless fit is formed when the substrate and PDMS substrate come into contact, avoiding contact gaps and uneven stress caused by material differences, thus eliminating electrode pattern distortion at the source. Second, interface modification works synergistically by performing plasma surface activation treatment on the substrate, oxidizing the Si-CH3 groups on the substrate surface to generate active groups such as hydroxyl (-OH) and carboxyl (-COOH), and using octadecyltrichlorosilane to modify the substrate interface, forming stable Si-O-Si hydrophobic chemical bonds, which significantly reduces the interfacial adhesion between the ink and the substrate. Third, the process parameters are precisely optimized, including the ratio of PDMS prepolymer to curing agent, polymerization temperature, and time, to ensure that the PDMS and ink patterned electrodes are completely transferred and the transfer rate is ≥90%, achieving perfect adaptation between the electrodes and the substrate. 2) Enhanced interlayer bonding and improved device mechanical reliability through interfacial synergy, with a clear mechanism: This invention achieves tight bonding between layers through a dual mechanism of "interface modification + process synergy." Firstly, the interfacial synergy between the electrode and the substrate, relying on precise optimization of process parameters, enables the ink electrode to form a stable chemical bond with the PDMS substrate, fundamentally preventing electrode delamination from the substrate during stretching. Secondly, the interfacial synergy between the electrode and the organic functional unit, after electrode transfer and curing, forms a flat and dense conductive layer, effectively avoiding the potential barrier height between the electrode and the light-emitting layer caused by conventional methods, forming good interfacial contact. At the same time, the elastic binder in the electrode can form intermolecular forces such as van der Waals forces and hydrogen bonds with the flexible polymer in the organic light-emitting layer, which not only improves the interfacial charge transport efficiency but also enhances the bonding strength between the electrode and the organic functional unit. 3) Simplified manufacturing process: The synergy between process and materials reduces the difficulty of industrialization, and the mechanism is feasible. This invention significantly reduces the difficulty of industrialization. First, material reuse synergy: PDMS material serves as both a flexible substrate and a transfer template, eliminating the need for additional special transfer templates (such as traditional photoresist templates or metal templates), reducing the types of materials and preparation steps, and lowering material costs and equipment investment. Second, process compatibility synergy: The PDMS transfer conductive ink transfer curing process (80-120℃), the spin coating annealing temperature of the hole transport layer and electron transport layer (60-120℃) are fully compatible, eliminating the need for additional equipment parameter adjustments, avoiding damage to the materials of each layer by high-temperature processes, and reducing equipment replacement frequency, thus improving production efficiency. Third, process simplification synergy: Transparent conductive ink can be directly applied and transferred to complete electrode preparation, eliminating the need for complex steps such as vacuum evaporation, sputtering, and etching required for traditional electrode preparation, shortening the production process, reducing material waste and labor costs, and ultimately reducing equipment investment costs, making it suitable for large-scale industrial mass production.

[0021] 2. The PDMS substrate of the present invention has excellent transparency (transmittance ≥90%), mechanical tensile properties (stretch rate ≥200%) and chemical stability. It not only solves the problems of insufficient heat resistance and tensile properties of existing substrates, but also perfectly matches the PDMS transfer conductive ink transfer process, providing reliable support for high-precision transfer of electrodes, while ensuring the overall transparency of the device.

[0022] 3. This invention takes PDMS transfer conductive ink transfer process as the core, and achieves non-destructive and high-precision transfer of transparent conductive electrodes by precisely controlling parameters such as transfer template preparation, ink coating, pressure application, and peeling speed. It effectively solves the problems of incomplete transfer, ink peeling, and pattern distortion in existing transfer processes. At the same time, combined with surface modification treatment, it significantly improves the interfacial bonding force between the electrode and the substrate and organic functional units, and avoids interlayer delamination during stretching. This invention achieves tight bonding between layers through a dual mechanism of "interface modification + process synergy": First, after plasma treatment and modification with octadecyltrichlorosilane, the substrate surface forms dense hydrophobic groups, weakening the interfacial bonding between the electrode and the substrate; second, after electrode transfer and curing, a smooth and dense conductive layer is formed on the surface, achieving good energy level matching with the hole transport layer and electron transport layer in the organic functional unit, which not only improves the interfacial charge transport efficiency but also enhances the interfacial bonding between the electrode and the organic functional unit through intermolecular forces; third, the cathode layer adopts the same PDMS transfer process as the anode layer, forming a symmetrical interfacial bonding structure with the electron transport layer, ensuring uniform stress on the upper and lower interfaces of the device and avoiding interlayer delamination caused by local stress concentration during stretching.

[0023] 4. This invention uses transparent conductive ink formulated with silver nanowires or Ag@Au core-shell nanowires, combined with PDMS transfer printing process, to prepare transparent stretchable electrodes (anode layer and cathode layer) with a light transmittance of ≥75% and a stretchability of ≥100%, which takes into account both transparency and stretchability, and has stable conductivity. After repeated stretching 100 times, the conductivity decays by ≤10%, which solves the defect of traditional electrodes that are difficult to balance transparency and stretchability.

[0024] 5. The preparation process of this invention is simple and highly controllable, and the parameters of each step are easy to adjust. In particular, the PDMS transfer conductive ink transfer process is convenient to operate and highly efficient, making it suitable for industrial mass production. The transparent stretchable organic light-emitting diodes prepared have a transmittance of ≥40%; wherein, the stretching ratio is ≥80%, and the device efficiency decay is ≤40%, which has broad prospects for industrial application.

[0025] 6. The transparent stretchable organic light-emitting diode of the present invention is suitable for various scenarios such as wearable devices, flexible display terminals, smart interactive devices, and transparent display panels. It can achieve stable light emission under deformations such as stretching, bending, and twisting, while having excellent transparency to meet the application requirements of transparent displays. Attached Figure Description

[0026] Figure 1 The molecular structural formulas in step 4 of Example 1 are as follows: (a) is the molecular structural formula of polydimethylsiloxane, (b) is the molecular structural formula of Super Yellow, (c) is the molecular structural formula of PEDOT:PSS, (d) is the molecular structural formula of poly[9,9-bis[3-(ethyldimethylamino)propyl]-9',9'-dioctyl[2,2'-bis-9H-fluorene]-7,7'-dimethyldibromide, and (e) is the molecular structural formula of ethoxylated polyethyleneimine.

[0027] Figure 2 This is a schematic diagram of the process for preparing the transparent stretchable organic light-emitting diode of the present invention.

[0028] Figure 3 The change in contact angle before and after hydrophobic treatment of quartz glass surface using octadecyltrichlorosilane was investigated.

[0029] Figure 4 This is a spectral diagram of the transparent stretchable organic light-emitting diode of the present invention.

[0030] Figure 5 This is a graph showing the relationship between voltage, brightness, and current density for the transparent stretchable organic light-emitting diode of the present invention.

[0031] Figure 6 This is a graph showing the relationship between brightness, energy efficiency, and current efficiency of the transparent stretchable organic light-emitting diode of the present invention.

[0032] Figure 7 This is a graph showing the relationship between the brightness and external quantum efficiency of the transparent stretchable organic light-emitting diode of the present invention.

[0033] Figure 8 The transmittance of polydimethylsiloxane, the cathode and anode layers of Example 1, and the transparent stretchable organic light-emitting diode. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0035] Example 1 like Figures 2-3As shown, a method for fabricating a transparent, stretchable organic light-emitting diode includes the following steps: Step 1: Place the glass substrate in a plasma treatment device and introduce gases such as argon and oxygen for plasma surface activation treatment. The treatment time is 5 minutes and the power is 30W, resulting in a modified glass substrate. Place the modified glass substrate in a glass petri dish and drop 10 μL of octadecyltrichlorosilane onto the surface of the glass substrate. Dry it in a vacuum drying oven at a vacuum degree of -0.06 MPa and a temperature of 60°C for 2 hours. Afterward, ultrasonically clean it sequentially with ethanol and dichloromethane to obtain the pretreated substrate.

[0036] Step 2: Using silver nanowires or Ag@Au core-shell nanowires as conductive fillers and a transparent elastic polymer as a binder, appropriate amounts of dispersant and solvent are added. After stirring evenly, ultrasonic dispersion is performed to obtain a uniformly dispersed transparent conductive ink. The conductive filler has a mass fraction of 5%, the binder has a mass fraction of 10%, the dispersant has a mass fraction of 1%, and the remainder is solvent. Patterned electrodes are then fabricated on the upper surface of the substrate after the pretreatment in Step 1 using a blade coating process.

[0037] Step 3: Mix the PDMS prepolymer and curing agent at a mass ratio of 10:1, stir thoroughly, and then remove air bubbles from the mixture using a vacuum degassing process for 15 minutes at a vacuum degree of -0.08. The degassed PDMS mixture is then drop-coated onto a patterned electrode using a drop-coating method to a thickness of 100 μm. Curing is then performed at 80℃ for 1 hour. After curing, the substrate is peeled off to obtain the anode or cathode layer. The cathode layer has a sheet resistance ≤20 Ω / □, an elongation ≥100%, and a conductivity attenuation ≤10% after 100 repeated stretching cycles.

[0038] like Figure 1As shown, in step 4, the anode layer is placed in a plasma treatment device, oxygen is introduced, and plasma surface activation treatment is performed for 5 minutes at a power of 80W to form active groups such as hydroxyl and carboxyl groups on the substrate surface, thereby improving the surface hydrophilicity. Then, a hole transport layer, an organic light-emitting layer, and an electron transport layer are sequentially spin-coated onto the upper surface of the anode layer using a solution spin-coating method to form an organic functional unit. Specifically, PEDOT:PSS is spin-coated onto the anode layer to obtain the hole transport layer at a spin-coating speed of 3000 rpm for 1 minute, with an annealing temperature of 120°C and an annealing time of 10 minutes. A prepared super yellow solution is spin-coated onto the hole transport layer to obtain the organic light-emitting layer. The concentration of the super yellow is 3-8 mg / ml, and the super yellow solution is a mixture of super yellow and a solvent, such as toluene, chlorobenzene, or tetrahydrofuran. The spin-coating speed is 3000 rpm for 1 minute, with an annealing temperature of 120°C and an annealing time of 20 minutes. A mixture of poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylaminopropyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide and ethoxylated polyethyleneimine in a mass ratio of 10:1 was spin-coated onto an organic light-emitting layer to obtain an electron transport layer. The solvent was methanol or ethanol, the concentration of the mixture was 5 mg / ml, the spin-coating speed was 3000 rpm, the spin-coating time was 1 min, the annealing temperature was 60 °C, and the annealing time was 20 min. The organic functional unit has excellent transparency and stretchability, is compatible with the anode layer and subsequent cathode layer, and does not affect the overall light transmittance of the device.

[0039] Step 5: Precisely align the cathode layer with the organic functional unit to avoid damaging the organic light-emitting layer. Apply pressure controlled at 0.05 MPa to prevent the organic functional unit from being crushed. Heat to 50°C to obtain a transparent, stretchable organic light-emitting diode.

[0040] Example 2 like Figures 2-3 As shown, a method for fabricating a transparent, stretchable organic light-emitting diode includes the following steps: Step 1: Place the glass substrate in a plasma treatment device and introduce gases such as argon and oxygen for plasma surface activation treatment. The treatment time is 10 minutes and the power is 50W, resulting in a modified glass substrate. Place the modified glass substrate in a glass petri dish and drop 10 μL of octadecyltrichlorosilane onto the surface of the glass substrate. In a vacuum drying oven at a vacuum degree of -0.1 MPa and a temperature of 100℃ for 3 hours, the substrate is then ultrasonically cleaned sequentially with ethanol and dichloromethane to obtain a pretreated substrate.

[0041] Step 2: Using silver nanowires or Ag@Au core-shell nanowires as conductive fillers and a transparent elastic polymer as a binder, appropriate amounts of dispersant and solvent are added. After stirring evenly, ultrasonic dispersion is performed to obtain a uniformly dispersed transparent conductive ink. The conductive filler has a mass fraction of 10%, the binder 15%, the dispersant 2%, and the remainder is solvent. Patterned electrodes are then fabricated on the upper surface of the pretreated substrate from Step 1 using a blade coating process.

[0042] Step 3: Mix PDMS prepolymer and curing agent at a mass ratio of 10:1 to obtain a mixture. After thorough stirring, remove air bubbles from the mixture using vacuum degassing treatment for 15 minutes at a vacuum degree of -0.1 MPa. The degassed PDMS mixture is then drop-coated onto a patterned electrode using a drop-coating method to a thickness of 150 μm. Curing is then performed at 100℃ for 1.5 hours. After curing, the substrate is peeled off to obtain an anode layer or cathode layer. The cathode layer has a sheet resistance ≤20 Ω / □, an elongation ≥100%, and a conductivity attenuation ≤10% after 100 repeated stretching cycles.

[0043] like Figure 1 As shown, in step 4, the anode layer is placed in a plasma treatment device, oxygen is introduced, and plasma surface activation treatment is performed for 10 minutes at a power of 80W to form active groups such as hydroxyl and carboxyl groups on the substrate surface, thereby improving the surface hydrophilicity. Then, a hole transport layer, an organic light-emitting layer, and an electron transport layer are sequentially spin-coated onto the upper surface of the anode layer using a solution spin-coating method to form an organic functional unit. Specifically, PEDOT:PSS is spin-coated onto the anode layer to obtain the hole transport layer at a spin-coating speed of 4000 rpm for 2 minutes, followed by an annealing temperature of 100°C and an annealing time of 20 minutes. A prepared super yellow solution is spin-coated onto the hole transport layer to obtain the organic light-emitting layer. The concentration of the super yellow is 6 mg / ml, and the super yellow solution is a mixture of super yellow and a solvent, such as toluene, chlorobenzene, or tetrahydrofuran. The spin-coating speed is 3000 rpm for 2 minutes, followed by an annealing temperature of 100°C and an annealing time of 20 minutes. A mixture of poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylaminopropyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide and ethoxylated polyethyleneimine in a mass ratio of 15:1 was spin-coated onto an organic light-emitting layer to obtain an electron transport layer. The solvent was methanol or ethanol, the concentration of the mixture was 4 mg / ml, the spin-coating speed was 3000 rpm, the spin-coating time was 2 min, the annealing temperature was 100 °C, and the annealing time was 20 min. The organic functional unit exhibits excellent transparency and stretchability, is compatible with the anode layer and subsequent cathode layer, and does not affect the overall light transmittance of the device.

[0044] Step 5: Precisely align the cathode layer with the organic functional unit to avoid damaging the organic light-emitting layer. Apply pressure controlled at 0.05 MPa to prevent the organic functional unit from being crushed. Heat to 60°C to obtain a transparent, stretchable organic light-emitting diode.

[0045] Example 3 like Figures 2-3 As shown, a method for fabricating a transparent, stretchable organic light-emitting diode includes the following steps: Step 1: Place the glass substrate in a plasma treatment device and introduce gases such as argon and oxygen for plasma surface activation treatment. The treatment time is 15 minutes and the power is 60W, resulting in a modified glass substrate. Place the modified glass substrate in a glass petri dish and add 15 μL of octadecyltrichlorosilane to the surface of the glass substrate. In a vacuum drying oven at a vacuum degree of -0.1 MPa and a temperature of 120°C for 4 hours, the substrate is then ultrasonically cleaned sequentially with ethanol and dichloromethane to obtain a pretreated substrate.

[0046] Step 2: Using silver nanowires or Ag@Au core-shell nanowires as conductive fillers and a transparent elastic polymer as a binder, appropriate amounts of dispersant and solvent are added. After stirring evenly, ultrasonic dispersion is performed to obtain a uniformly dispersed transparent conductive ink. The conductive filler has a mass fraction of 15%, the binder has a mass fraction of 20%, the dispersant has a mass fraction of 3%, and the remainder is solvent. Patterned electrodes are then fabricated on the upper surface of the substrate after the pretreatment in Step 1 using a blade coating process.

[0047] Step 3: Mix the PDMS prepolymer and curing agent at a mass ratio of 10:1, stir thoroughly, and then remove air bubbles from the mixture using a vacuum degassing process for 20 minutes at a vacuum degree of -0.1 MPa. The degassed PDMS mixture is then drop-coated onto a patterned electrode using a drop-coating method to a thickness of 200 μm. Curing is then performed at 120℃ for 2 hours. After curing, the substrate is peeled off to obtain the anode or cathode layer. The cathode layer has a sheet resistance ≤20 Ω / □, an elongation ≥100%, and a conductivity attenuation ≤10% after 100 repeated stretching cycles.

[0048] like Figure 1As shown, in step 4, the anode layer is placed in a plasma treatment device, oxygen is introduced, and plasma surface activation treatment is performed for 5 minutes at a power of 80W to form active groups such as hydroxyl and carboxyl groups on the substrate surface, thereby improving the surface hydrophilicity. Then, a hole transport layer, an organic light-emitting layer, and an electron transport layer are sequentially spin-coated onto the upper surface of the anode layer using a solution spin-coating method to form an organic functional unit. Specifically, PEDOT:PSS is spin-coated onto the anode layer to obtain the hole transport layer at a spin-coating speed of 3000 rpm for 1.5 minutes, followed by an annealing temperature of 120°C and an annealing time of 20 minutes. A prepared super yellow solution is spin-coated onto the hole transport layer to obtain the organic light-emitting layer. The concentration of the super yellow is 8 mg / ml, and the super yellow solution is a mixture of super yellow and a solvent, such as toluene, chlorobenzene, or tetrahydrofuran. The spin-coating speed is 3000 rpm for 1.5 minutes, followed by an annealing temperature of 120°C and an annealing time of 20 minutes. A mixture of poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylaminopropyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide and ethoxylated polyethyleneimine in a mass ratio of 15:1 was spin-coated onto an organic light-emitting layer to obtain an electron transport layer. The solvent was methanol or ethanol, the concentration of the mixture was 5 mg / ml, the spin-coating speed was 3000 rpm, the spin-coating time was 1.5 min, the annealing temperature was 120 °C, and the annealing time was 20 min. This organic functional unit layer exhibits excellent transparency and stretchability, is compatible with the anode layer and subsequent cathode layer, and does not affect the overall light transmittance of the device.

[0049] Step 5: Precisely align the cathode layer with the organic functional unit to avoid damaging the organic light-emitting layer. Apply pressure controlled at 0.05 MPa to prevent the organic functional unit from being crushed. Heat to 70°C to obtain a transparent, stretchable organic light-emitting diode.

[0050] Application examples like Figure 4 As shown, the spectra of the transparent stretchable organic light-emitting diode prepared in Example 1 were measured in air using a Keithley 2400 source meter and an absolute external quantum efficiency measurement system (AQSIQ). The spectra were measured on the front side (substrate side), back side, and after 100% stretching. Figure 4 As can be seen from the front and back tests, the transparent stretchable organic light-emitting diode (OLED) can emit light from both sides. The 100% stretch test proves that the transparent stretchable OLED can also emit light under stretching.

[0051] like Figure 5As shown, the electrical and optical properties of the transparent stretchable organic light-emitting diode prepared in Example 1 before and after stretching were tested in an air environment using a Keithley 2400 source meter and an absolute external quantum efficiency measurement system. Figure 5 It can be seen that when the stretching ratio is 80%, the maximum brightness of the transparent stretchable organic light-emitting diode before and after stretching is 29037 cd / m². 2 Reduced to 23617 cd / m 2 The decrease is less than 20%. At a voltage of 12V, the current density only drops from 747mA / cm². 2 Dropped to 668 mA / cm 2 The decrease was less than 15%.

[0052] like Figure 6 As shown, the energy efficiency and current efficiency of the transparent stretchable organic light-emitting diode (OLED) prepared in Example 1 were tested in an air environment using a Keithley 2400 source meter and an absolute external quantum efficiency measurement system. When the stretching ratio was 80%, the maximum current efficiency of the transparent stretchable OLED decreased from 11.1 cd / A to 6.9 cd / A, a decrease of <40%; the maximum energy efficiency of the transparent stretchable OLED decreased from 5.2 lm / W to 3.2 lm / W, a decrease of <40%.

[0053] like Figure 7 As shown, the external quantum efficiency of the transparent stretchable organic light-emitting diode prepared in Example 1 was tested before and after stretching using a Keithley 2400 source meter and an absolute external quantum efficiency measurement system in an air environment. Figure 7 It can be seen that when the stretching ratio is 80%, the external quantum efficiency of the transparent stretchable organic light-emitting diode decreases from 3.2% to 2.1%, a decrease of less than 40%.

[0054] like Figure 8 As shown, transmittance tests were performed on the PDMS, the conductive ink (anode layer or cathode layer) after PDMS transfer, and the transparent stretchable organic light-emitting diode of Example 1. Figure 8 It is known that the transparent stretchable electrode (anode layer) prepared by the present invention using transparent conductive ink formulated with silver nanowires or Ag@Au core-shell nanowires, combined with PDMS transfer printing process, has a light transmittance ≥75% and a stretchability ≥100%, balancing transparency and stretchability. Furthermore, it exhibits stable conductivity, with a conductivity decay of ≤10% after 100 repeated stretching cycles, thus overcoming the limitation of traditional electrodes in achieving both transparency and stretchability. The transparent stretchable organic light-emitting diode of the present invention has a light transmittance ≥40%, demonstrating broad prospects for industrial applications.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a transparent, stretchable organic light-emitting diode, characterized in that, Includes the following steps: Step 1: After activating the substrate, perform hydrophobic treatment to obtain the pretreated substrate; Step 2: Patterned electrodes are fabricated on the upper surface of the pretreated substrate using transparent conductive ink; Step 3: Drop the degassed PDMS mixture onto the patterned electrode, then perform a curing process, and peel off the substrate to obtain the anode layer or cathode layer. Step 4: A hole transport layer, an organic light-emitting layer, and an electron transport layer are sequentially spin-coated onto the upper surface of the anode layer to form an organic functional unit; Step 5: Apply pressure to the cathode layer and heat it to bond it to the organic functional unit to obtain a transparent stretchable organic light-emitting diode.

2. The preparation method according to claim 1, characterized in that, In step 1, the substrate is glass, quartz sheet or silicon wafer.

3. The preparation method according to claim 1, characterized in that, In step 1, the activation process of the substrate is as follows: the substrate is subjected to plasma surface activation treatment for 5-15 minutes and the power is 30-60W.

4. The preparation method according to claim 1, characterized in that, In step 1, the hydrophobic treatment process is as follows: octadecyltrichlorosilane is dropped onto the activated substrate surface, dried at a vacuum of -0.06 to -0.1 MPa and a temperature of 60-120°C for 2-4 hours, and then ultrasonically cleaned with ethanol and dichloromethane in sequence.

5. The preparation method according to claim 1, characterized in that, In step 2, the transparent conductive ink is prepared as follows: using silver nanowires or Ag@Au core-shell nanowires as conductive fillers, using transparent elastic polymers as binders, adding dispersants and solvents, stirring evenly, and then using ultrasonic dispersion treatment to obtain uniformly dispersed transparent conductive ink; wherein, the mass fraction of conductive fillers is 5%-15%, the mass fraction of binders is 10%-20%, and the mass fraction of dispersants is 1%-3%.

6. The preparation method according to claim 1, characterized in that, In step 2, patterned electrodes are prepared on the substrate surface using a blade coating process.

7. The preparation method according to claim 1, characterized in that, In step 3, the PDMS mixture is a mixture of PDMS prepolymer and curing agent at a mass ratio of 10:1-15:

1. Vacuum degassing is used to remove air bubbles from the mixture. The degassing time is 15-30 min, the vacuum degree is -0.08~-0.1 MPa, the curing temperature is 80-120℃, the curing time is 1-2 h, and the thickness of the anode layer or cathode layer is 100-200 μm.

8. The preparation method according to claim 1, characterized in that, In step 4, the anode layer is first subjected to surface activation treatment, and then the organic functional unit is prepared by spin coating. The specific process is as follows: plasma surface activation treatment is performed in a mixed gas of oxygen and / or argon for 5-15 min and power of 80-120W. The hole transport layer is prepared by spin-coating PEDOT:PSS onto the anode layer at a spin speed of 3000-4000 rpm for 1-3 min, an annealing temperature of 60-120℃ for 10-20 min. The organic light-emitting layer is prepared as follows: a super yellow solution is spin-coated onto the hole transport layer. The concentration of the super yellow solution is 3-8 mg / ml. The super yellow solution is a mixture of super yellow and a solvent, wherein the solvent is toluene, chlorobenzene, or tetrahydrofuran. The spin-coating speed is 2000-3000 rpm, the spin-coating time is 1-3 min, the annealing temperature is 60-120℃, and the annealing time is 10-20 min. The electron transport layer is prepared by mixing a mixture of poly[9,9-bis[3-(ethyldimethylamino)propyl]-9',9'-dioctyl[2,2'-bis-9H-fluorene]-7,7'-dimethyldibromide and ethoxylated polyethyleneimine with a solvent in a mass ratio of 10:1-15:

1. The solvent is methanol or ethanol. The concentration of the mixture is 2-5 mg / ml. The spin coating speed is 2000-3000 rpm, the spin coating time is 1-3 min, the annealing temperature is 60-120℃, and the annealing time is 10-20 min.

9. The preparation method according to claim 1, characterized in that, In step 5, the applied pressure is 0.05-0.1 MPa, and the heating temperature is 50-70°C.

10. The transparent stretchable organic light-emitting diode obtained by the preparation method according to any one of claims 1 to 9, characterized in that, From bottom to top, it includes the anode layer, hole transport layer, organic light-emitting layer, electron transport layer, and cathode layer.

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