High external quantum efficiency organic deep red / near-infrared light emitting diodes based on strongly oriented emissive layers

Abstract

High external quantum efficiency organic deep red / near infrared light emitting diode based on strong orientation light emitting layer belongs to the technical field of diode.The application uses solution method to prepare the organic deep red / near infrared light emitting diode with excellent performance and controllable wavelength by adjusting eccentric distance, chuck rotating speed, solvent system and other factors, and simultaneously significantly improves the performance of the device. The organic deep red / near infrared light emitting diode has a light emitting range of 600-850nm, and the external quantum efficiency of the best performance device can be as high as about 18%.

Description

TECHNICAL FIELD

[0001] The application relates to a high-external quantum efficiency organic deep red / near-infrared light-emitting diode based on a strong orientation light-emitting layer and a preparation method thereof, and belongs to the technical field of organic light-emitting diodes. BACKGROUND

[0002] The organic deep red / near-infrared light-emitting diode has important applications in the fields of biological imaging, infrared illumination, optical communication, environmental sensing, food and product quality control and the like. The organic small molecule device generally adopts vacuum evaporation deposition, but due to the limitation of the size of the vacuum cavity, it is difficult to realize the preparation of a large-area OLED device, and it is also difficult to accurately control the doping ratio, especially in the case of low concentration doping. In addition, the evaporation method has high power consumption and is easy to cause waste of materials and energy. The solution-processed organic light-emitting diode has more advantages in the commercial production of low-cost, large-area and flexible displays. At present, the external quantum efficiency of the organic light-emitting diode in the blue, green and orange-red light-emitting range has reached more than 20%, while the performance of the organic deep red / near-infrared light-emitting diode with excellent biocompatibility has developed slowly. In addition to the inherent limitation of the light-emitting quantum yield caused by the narrow band gap, the difficulty lies in the lack of an effective method for constructing a high-external quantum efficiency organic deep red / near-infrared light-emitting diode through a solution processing method.

[0003] In order to fine-tune the solid-state molecular arrangement of the active layer, people have carried out continuous research and a large number of optimization strategies. In recent years, by applying external force to guide the molecular arrangement, adjusting the film forming parameters to control the film morphology and crystal phase, an organic field effect transistor with significantly enhanced charge carrier mobility has been used. In 2022, Oliveira et al. tried to use Langmur-Blodgett film to improve the performance of the device, and the device prepared by the method has obviously improved performance. However, the operation of the method is complex, the film forming equipment is expensive, and the technical requirements are very high.

[0004] The application provides a strong orientation light-emitting layer applied to a high-external quantum efficiency organic deep red / near-infrared light-emitting diode and a preparation method thereof. The application obtains an organic deep red / near-infrared light-emitting diode with obviously improved light out-coupling output efficiency and external quantum efficiency by controlling the degree of molecular ordered arrangement in the light-emitting layer film forming process. SUMMARY

[0005] The strong orientation light-emitting layer applied to the organic deep red / near-infrared LED and the preparation method thereof provided by the application are realized through the following steps:

[0006] Step A: accurately weighing PVK as a light-emitting layer host material and TP AAP as a light-emitting layer guest material, preparing a light-emitting layer host-guest material into a light-emitting layer mixture solution, and adopting solvent dissolution;

[0007] Step B: spin-coat the hole injection layer PEDOT:PSS on the pre-prepared ITO glass substrate, and then anneal treatment;

[0008] Step C: then spin-coat the hole transport layer PVK on the hole injection layer PEDOT:PSS and perform anneal treatment;

[0009] Step D: place the substrate obtained in Step C on a large turntable, the substrate is 0.5-5 cm away from the rotation center of the large turntable, and the light-emitting layer mixture solution in Step A is rapidly spin-coated into a film in an eccentric spin-coating manner;

[0010] Step E: anneal the film obtained in Step D at 60-130°C for 10-30 min, and then remove the position to be covered by the anode after cooling;

[0011] Step F: transfer the light-emitting layer obtained by removing the anode position in Step E into a vacuum evaporation chamber, and then evaporate the electron transport layer TmPyPB, the electron injection layer LiF, and the cathode Al on the light-emitting layer in sequence to obtain an organic deep red / near-infrared light-emitting diode;

[0012] In Step A of the above summary, the mass ratio of the host and the guest is 0.5%-30% (preferably 7-9%); in addition, chlorobenzene is used for dissolution; and in the light-emitting layer mixture solution, 0.8-1.2 ml of chlorobenzene corresponds to 7 g of PVK.

[0013] In Step B of the above summary, after the ITO glass substrate is cleaned, it is ultrasonically washed with deionized water, acetone, and ethanol respectively for 15-30 min. The obtained PEDOT:PSS layer is annealed at 140-170°C for 15 min.

[0014] In Step C of the above summary, after the annealing of the hole injection layer PEDOT:PSS layer is completed, it is immediately transferred into a vacuum glove box, and the PVK layer is prepared after cooling. The PVK layer is annealed at 100-130°C for 15 min.

[0015] In Step D of the above summary, the rotation speed is controlled between 1500-4000 rpm. If the rotation speed is too low, the organic molecules in the film cannot be effectively arranged, and if the rotation speed is too high, the solvent volatilizes too quickly, which can cause the molecules to form a film before they have a chance to arrange under stress, affecting the horizontal dipole orientation ratio. The size of the substrate is preferably (14-16) cm* (13-14) cm, preferably 15.5 cm in length and 13.5 cm in width, and the corresponding volume of the light-emitting layer mixture solution is 20-30 microliters.

[0016] In Step E of the above summary, multiple diodes can be prepared at one time, and the position covered by the anode of each diode is removed using a doctor blade or an organic solvent chlorobenzene.

[0017] In step F of the above summary, the vacuum degree is less than 3*10 -4 The evaporation is carried out under a pressure of 10 The following.

[0018] The organic deep red / near-infrared light emitting diode has a light emitting range of 600-850 nm, and the external quantum efficiency of the best performance device can be as high as about 18%. The organic molecules in the prepared light emitting layer reach a level of more than 70% of the dipole orientation ratio, and the light out-coupling output efficiency of the prepared organic deep red / near-infrared light emitting diode is obviously improved, which has certain application prospect in the fields of information storage, medical devices and imaging technology. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 1 is a schematic diagram of the eccentric spin coating device of the present application;

[0020] Figure 2 Figure 1 is a schematic diagram of the eccentric spin coating device of the present application;

[0021] Figure 3 Figure 1 is a schematic diagram of the eccentric spin coating device of the present application;

[0022] Figure 4 Figure 1 is a schematic diagram of the eccentric spin coating device of the present application; DETAILED DESCRIPTION

[0023] The present application will be described in detail below in conjunction with the embodiments, and the present application is not limited to these manufacturing examples.

[0024] Example 1

[0025] PVK 7 mg two bottles, TPAAP 4.8 mg one bottle, the bottle mouth gently twist loose into the glove box, one of the bottles of PVK added 1 mL of chlorobenzene, fully dissolved after the hole transport layer. The other two bottles each added 1 mL of chloroform, fully dissolved after taking 416 μL PVK and 80 μL TPAAP into a new bottle mixed as light emitting layer solution (light emitting layer solution PVK and TPAAP mass ratio of 7.6%, every 7g PVK corresponding chlorobenzene 1ml). On the prepared ITO glass substrate (length of 15.5 cm wide 13.5 cm) spin PEDOT: PSS layer and annealed at 160 °C for 15 min, after annealing, immediately transferred into the vacuum glove box, cooled spin PVK layer and annealed at 120 °C for 15 min. Again after cooling the substrate is placed at a distance of 2 cm from the center of rotation, taking 26 μL solution using eccentric spin coating method to prepare light emitting layer film, the speed control at 2900 rpm. The resulting film in 120 °C annealing for 15 min, after cooling the anode covered position using chlorobenzene gently wipe, and transferred into the vacuum evaporation chamber. In the vacuum degree of 2*10 -4 Pa conditions under the electron transport layer TmPyPB, electron injection layer LiF, cathode Al, evaporation when each layer corresponding to the maximum rate of control at The organic deep red / near infrared light emitting diode can be obtained.

[0026] Example 2

[0027] PVK 7 mg two bottles, TPAAP 4.8 mg one bottle, the bottle mouth gently twist loose into the glove box, one of the bottles of PVK added 1 mL of chlorobenzene, fully dissolved after the hole transport layer. The other two bottles each added 1 mL of chloroform, fully dissolved after taking 416 μL PVK and 80 μL TPAAP into a new bottle mixed as light emitting layer solution (light emitting layer solution PVK and TPAAP mass ratio of 7.6%, every 7g PVK corresponding chlorobenzene 1ml). On the prepared ITO glass substrate (length of 15.5 cm wide 13.5 cm) spin PEDOT: PSS layer and annealed at 160 °C for 15 min, after annealing, immediately transferred into the vacuum glove box, cooled spin PVK layer and annealed at 120 °C for 15 min. Again after cooling the substrate is placed at a distance of 2 cm from the center of rotation, taking 26 μL solution using eccentric spin coating method to prepare light emitting layer film, the speed control at 2900 rpm. The resulting film in 120 °C annealing for 15 min, after cooling the anode covered position using chlorobenzene gently wipe, and transferred into the vacuum evaporation chamber. In the vacuum degree of 2*10 -4The electron transport layer TmPyPB, the electron injection layer LiF and the cathode Al were sequentially deposited under the condition of Pa, and the maximum rates were controlled at The organic deep red / near-infrared light emitting diode was obtained.

[0028] Example 3

[0029] Two bottles of PVK7 mg and one bottle of TPAAP 4.8 mg were accurately weighed using a centile analysis balance, and one bottle of PVK was added with 1 mL of chlorobenzene, and after being fully dissolved, it was used as a hole transport layer. The other two bottles were each added with 1 mL of chloroform, and after being fully dissolved, 720 μL of PVK and 200 μL of TPAAP were added into a new bottle and mixed uniformly as a light emitting layer solution (the mass ratio of PVK and TPAAP in the light emitting layer solution was 5.3%, and 1 ml of chlorobenzene was corresponding to 7 g of PVK). The PEDOT: PSS layer was spin-coated on the ITO glass substrate (15.5 cm long and 13.5 cm wide) prepared in advance and was annealed at 160°C for 10 min. After the annealing was completed, it was immediately transferred into the vacuum glove box, and after cooling, the PVK layer was spin-coated and annealed at 120°C for 10 min. After cooling again, the substrate was placed at a distance of 4 cm from the rotation center, and 25 μL of solution was used to prepare a light emitting layer film using eccentric spin coating method, and the rotation speed was controlled at 1600 rpm. The obtained film was annealed at 130°C for 10 min, and after cooling, the anode covered position was gently wiped with chlorobenzene, and was transferred into the vacuum evaporation chamber. The electron transport layer TmPyPB, the electron injection layer LiF and the cathode Al were sequentially deposited under the condition of Pa, and the maximum rates were controlled at -4 The organic deep red / near-infrared light emitting diode was obtained.​

Claims

1. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer, characterized in that, Includes the following steps: Step A: Accurately weigh PVK as the host material of the light-emitting layer and TPAAP as the guest material of the light-emitting layer, prepare the host and guest materials of the light-emitting layer into a solution of the light-emitting layer mixture, and dissolve it with a solvent; Step B: Spin-coat a hole injection layer PEDOT:PSS onto a pre-prepared ITO glass substrate, and then anneal it. Step C: Then spin-coat the hole transport layer PVK onto the hole injection layer PEDOT:PSS and perform annealing. Step D: Place the substrate obtained in step C on a large turntable, with the substrate 0.5-5 cm away from the center of rotation of the turntable. Take the luminescent layer mixture solution from step A and spin-coat it rapidly to form a film using an eccentric spin-coating method; control the rotation speed between 1500-4000 rpm. Step E: Anneal the film obtained in step D at 60-130℃ for 10-30 min, and remove the area to be covered by the anode after cooling. Step F: The light-emitting layer obtained in Step E, after removing the anode position, is transferred into a vacuum evaporation chamber. An electron transport layer TmPyPB, an electron injection layer LiF, and a cathode Al are then deposited sequentially on the light-emitting layer to obtain an organic deep red / near-infrared light-emitting diode.

2. The method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 1, characterized in that, In step A above, the mass ratio of the host and guest components is 0.5%-30%; chlorobenzene is used for dissolution; and 0.8-1.2 ml of chlorobenzene corresponds to every 7 g of PVK in the luminescent layer mixture solution.

3. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 2, characterized in that, The mass ratio of the subject and object is 7-9%.

4. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 1, characterized in that, In step B, after cleaning the ITO glass substrate, it is ultrasonicated twice each with deionized water, acetone, and ethanol for 15-30 min. The resulting PEDOT:PSS layer is then annealed at 140-170℃ for 15 min. In step C, after the hole injection layer PEDOT:PSS layer is annealed, it is immediately transferred into a vacuum glove box, cooled, and then the PVK layer is prepared. The PVK layer is annealed at 100-130℃ for 15 min.

5. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 1, characterized in that, The volume of the luminescent layer mixture solution corresponding to the substrate dimensions of (14-16) cm * (13-14) cm is 20-30 μL.

6. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 5, characterized in that, The base measures 15.5 cm in length and 13.5 cm in width.

7. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 1, characterized in that, In step E, multiple diode arrays are prepared at once. The area covered by the anode of each diode is gently scraped off with a scraper or wiped off with the organic solvent chlorobenzene.

8. A method for fabricating a high external quantum efficiency organic deep-red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer according to claim 1, characterized in that, In step F, when the vacuum level is below 3*10 -4 Evaporation was carried out under Pa conditions, with the maximum evaporation rate for each layer controlled at 2-6 Å / s.

9. A high external quantum efficiency organic deep red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer, prepared according to any one of claims 1-8.

10. An application of a high external quantum efficiency organic deep red / near-infrared light-emitting diode based on a strongly oriented light-emitting layer, prepared according to any one of claims 1-8, for use in the fields of information storage, medical devices, and imaging technology.

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