Single-emission-base color narrow-band organic polariton light-emitting diode of novel assembly film and preparation method thereof

Abstract

The invention discloses a biphenyl vinyl derivative molecule (BDAVBi) and a synthesis method thereof, a preparation method of a novel organic assembled film (OAF), and a single-emission-base color narrow-band organic polariton light-emitting diode of the novel assembled film and a preparation method of the single-emission-base color narrow-band organic polariton light-emitting diode. At present, an organic light-emitting diode (OLED) is expected to be used for preparing multicolor, narrow-band emission and high-definition displays. However, it is very challenging to achieve a wide color gamut and high fidelity strong color purity in accordance with the BT.2020 standard. However, by embedding the organic assembly film into a microcavity OLED, efficient organic polariton electroluminescence can be generated. The polariton OLED (POLED) disclosed by the invention has the following advantages: low turn-on voltage (about 2 V), emission of six different narrowband colors (from blue to red, the full width at half maximum being less than 26 nm), maintenance of stability at a current density up to 118 A / cm < 2 >, and external quantum efficiency (EQE) up to 1.98% and internal quantum efficiency (IQE) close to 100% at a current density of 89 A / cm < 2 >. Wide color gamut and high color purity can be achieved by controlling photon components. The innovative invention is expected to promote the realization of an electrically driven organic solid-state laser (EDOSSLS) integrated into a single-component system, and is applied to the field of display and illumination of the tip.

Description

Technical Field

[0001] The invention relates to the technical field of multicolor organic light emitting diodes and display and lighting, in particular to a novel assembled film single-emission-based color narrow-band organic polariton light emitting diode and a preparation method thereof. Background Art

[0002] Advances in ultra-high-definition display (UDD) technology require electroluminescent (EL) devices to achieve high color fidelity in the three primary colors of red, green, and blue to meet the BT.2020 recommendation standard of the International Telecommunication Union Radiocommunication Sector. Multicolor organic light-emitting materials (OLMs) have become promising candidates for the manufacture of multicolor organic light-emitting diodes (OLEDs), which are key to the production of full-color displays. These materials are valued for their light weight, scalability to large sizes, and highly tunable optoelectronic properties. Currently, the time-consuming and laborious design and synthesis of multicolor luminescent molecules, the extremely complex integration of multicolor OLED devices, and the broadband emission of most OLEDs (full width at half maximum, FWHM, more than 60nm) have seriously hindered the application of user-friendly UDD technology. Therefore, it is of great significance to develop color OLEDs with narrowband emission, simple integration, and efficient electroluminescent performance. The present invention will provide a breakthrough method to prepare narrowband, colorful, and efficient OLEDs, and move towards the realization of electrically driven organic solid-state lasers (EDOSSLs), which is expected to promote the development of display technology and lighting. Summary of the invention

[0003] The invention relates to the technical field of multicolor organic light emitting diodes and display and lighting, in particular to a novel assembled film single-emission-based color narrow-band organic polariton light emitting diode and a preparation method thereof.

[0004] The purpose of the present invention is to provide a single-emission-based color narrow-band organic polaritons light-emitting diode of a novel assembled film and a preparation method thereof, so as to solve the problems of broadband emission, low color fidelity and difficulty in integrating multicolor devices of OLEDs in the prior art. In existing literature reports, the full width at half maximum (FWHM) of colored organic light-emitting diodes exceeds 60nm, which seriously damages the high color fidelity of such devices and is very unfavorable for their practical application. In order to alleviate the emission linewidth problem, one method is to integrate organic emitters into microcavities to construct microcavity OLEDs, which is very effective in reducing the emission linewidth. However, since the cavity dispersion in the weak coupling state depends on the angle, its development is affected. However, when organic exciton crystal materials are strongly coupled with microcavity photons, resulting in the formation of exciton polaritons (EPs), these EPs utilize the beneficial properties of excitons and photons, so that the photons generated by polaritons dispersion have both narrowband characteristics and angle-independent characteristics. Therefore, organic polaritons pave the way for the simultaneous control of multicolor and narrowband emission in polaritons OLED systems. But the electroluminescent properties of these devices have been less than ideal due to challenges in combining them with the carrier-transport layers necessary for OLEDs.

[0005] The present invention discloses a method for synthesizing a distyryl derivative molecule, which is characterized in that a distyryl derivative 4,4'-bis[4-(diphenylamino)phenyl]biphenyl molecule, namely BDAVBi, is designed and synthesized, and the specific synthesis steps are as follows:

[0006] S1. Mix ([1,1'-biphenyl]-4,4'-diylbis(methylene))bis(phosphonate)tetraethyl with NaH powder in tetrahydrofuran solution, cool in an ice bath at 0°C for 1h, then inject 4-(diphenylamine)benzaldehyde / tetrahydrofuran solution into the reaction ball, stir the reaction mixture at room temperature for 12h, pour into water, and extract the product with CH2Cl2. Wash the mixed organic phase with ultrapure water, dry with anhydrous MgSO4, filter, evaporate, and then recrystallize with n-hexane, and finally dry to obtain the product BDAVBi powder.

[0007] The present invention discloses a method for preparing a novel organic assembled film, and adopts a simple space-restricted self-assembly method to prepare a centimeter-level BDAVBi organic assembled film (BDAVBi OAF). The specific steps are as follows:

[0008] S2. Use an analytical balance to accurately weigh the BDAVBi powder, then add it to dichloromethane (CH2Cl2) and dissolve it with slight heat. Add pure water to a glass petri dish, and then carefully transfer the BDAVBi / CH2Cl2 solution to the water surface. As the solvent evaporates, a large area of ​​OAF is formed on the water surface.

[0009] The present invention discloses a novel assembled film single-emission base color narrow-band organic polaritons light-emitting diode, whose structure from bottom to top is composed of a substrate, a lower reflector, a hole injection layer, a light-emitting layer, an electron injection layer and an upper reflector, wherein the light-emitting layer is a large-area organic assembled film BDAVBi OAF, and the upper and lower reflectors are silver (Ag) films of different thicknesses. In the angle-resolved reflectivity measurement at room temperature, the OLED device of a specific thickness exhibits the characteristics of a strong coupling state, and in the electroluminescence measurement, the device shows super strong electroluminescence performance, that is, the current density can be as high as 118A / cm 2 , the external quantum efficiency (EQE) is 1.98%, and the turn-on voltage is as low as 2V. Six different narrowband emissions from blue to red (each less than 26nm wide) can be provided simply by adjusting the thickness of the light-emitting layer, and the color gamut accounts for 71.93% of the BT.2020 standard. It should be understood that the advantages of the present invention will be explained in the subsequent description, and the following detailed description is exemplary and explanatory. The objects and other advantages of the present invention can be achieved and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required in the description of the embodiments:

[0011] Figure 1 These are the specific synthesis steps of a distyryl derivative BDAVBi molecule designed and synthesized in Example 1 of the present invention.

[0012] Figure 2 A is a schematic diagram of the preparation of BDAVBi OAF in Example 2 of the present invention.

[0013] Figure 2 B is a real photo of the BDAVBi OAF prepared in Example 2 of the present invention.

[0014] Figure 3 This is the absorption and emission spectrum of the BDAVBi OAF prepared in Example 2 of the present invention.

[0015] Figure 4 It is a schematic diagram of the device structure of a single-emission-based color narrow-band organic polariton light-emitting diode (POLED) of a novel assembled film prepared in Example 3 of the present invention.

[0016] Figure 5The angle-resolved reflectance spectrum (left) / simulation (right) result diagram of the POLED with a light-emitting layer thickness of 90 nm prepared in Example 4 of the present invention. The red and yellow dotted lines represent the fitting curves of the exciton dispersion and cavity mode dispersion, respectively, and the blue line fits the dispersion curves of the lower polariton branch (LP) and the upper polariton branch (UP) under the coupled resonator model.

[0017] Figure 6 AF is the angle-resolved reflectance spectra of POLEDs with light-emitting layer thicknesses of 61 nm, 78 nm, 90 nm, 108 nm, 143 nm and 202 nm prepared in Example 4 of the present invention, wherein the red and yellow dashed lines represent the fitting curves of exciton dispersion and cavity mode dispersion, respectively, and the blue line fits the LP and UP dispersion curves under the coupled resonator model.

[0018] Figure 7 AC is the electroluminescence (EL) performance of the POLED with a light-emitting layer thickness of 90 nm prepared in Example 4 of the present invention. A is the dependence of current density (blue line) and current efficiency (red line) on voltage. B is the dependence of luminescence (blue line) and EQE (red line) on current density. C is the dependence of luminescence on voltage.

[0019] Figure 8 A is an electroluminescent photograph of six different colors of POLEDs of six different thicknesses prepared in Example 4 of the present invention under EL action.

[0020] Figure 8 B is an EL spectrum diagram of six POLEDs with different thicknesses prepared in Example 4 of the present invention, and the full width at half maximum (FWHM) is less than 26 nm. Fig. 9 AD are electroluminescent performance diagrams of POLEDs prepared in Example 4 of the present invention with luminescent layer thicknesses of 61 nm, 78 nm, 108 nm, 143 nm and 202 nm, respectively. Dependence of current density (A) and current efficiency (B) on voltage. Dependence of luminescence (C) and EQE (D) on current density.

[0021] Fig.10 AF is the angle-resolved photoluminescence / electroluminescence (PL / EL) spectra of the POLEDs with luminescent layer thicknesses of 61 nm, 78 nm, 90 nm, 108 nm, 143 nm and 202 nm prepared in Example 4 of the present invention. In the white dashed rectangle, the EL spectrum is superimposed on the PL spectrum at an angle of ±15°.

[0022] Fig.11 A is the color coordinates of the six POLEDs with different thicknesses prepared in Example 4 of the present invention on the CIE diagram, marked with white circles.

[0023] Fig.11B is a comparison chart of the color gamut (white triangle) of the six POLEDs of different thicknesses prepared in Example 4 of the present invention and the color gamut standard of BT.2020 (red triangle). DETAILED DESCRIPTION

[0024] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve the technical problems raised in previous years and achieve the technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various features in the various embodiments of the present invention can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0025] Embodiment 1:

[0026] A distyryl derivative 4,4'-bis[4-(diphenylamino)phenyl]biphenyl molecule, namely BDAVBi, was designed and synthesized. The synthetic route is as follows: Figure 1 The specific steps of synthesis are as follows:

[0027] ([1,1'-biphenyl]-4,4'-diylbis(methylene))bis(phosphonate)tetraethyl (1 mmol, 0.454 g) was mixed with NaH powder (16.67 mmol, 0.4 g) in tetrahydrofuran (THF) solution and cooled in an ice bath at 0°C for 1 hour. Then, a 4-(diphenylamine)benzaldehyde / THF solution (>2 mmol) was injected into the reaction sphere. The reaction mixture was stirred at room temperature for 12 hours and then poured into water. The product was extracted with CH2Cl2. The combined organic phases were washed with water, dried over anhydrous MgSO4, filtered, and evaporated. The product was separated by flash chromatography on silica gel using CH2Cl2 / petroleum ether (1:3). It was then recrystallized from n-hexane and finally dried to obtain BDAVBi powder with a yield of 80% ± 2%.

[0028] Embodiment 2:

[0029] BDAVBi OAF is prepared by a simple space-restricted self-assembly method. The schematic diagram of the preparation principle is shown in the figure. Figure 2 As shown in A. Use an analytical balance to accurately weigh 10 mg of BDAVBi powder. Then, add 1 mL of dichloromethane (CH2Cl2) and dissolve it with slight heat. Add 15 mL of pure water to a 60 nm glass petri dish, and then carefully transfer 50 μL of BDAVBi / CH2Cl2 stock solution to the water surface. As the solvent evaporates, a large area of ​​OAF is formed on the water surface. The size of the prepared OAF can reach the centimeter level, such as Figure 2B. By changing the concentration of the mother solution, OAFs with different thicknesses and less roughness can be prepared in a controllable manner. The normalized steady-state absorption and photoluminescence (PL) spectra of BDAVBi OAF were tested. The absorption spectrum shows a wide range of absorption characteristics with a broad peak at 420nm, while the PL spectrum mainly shows a transition at 503nm. The results are shown in Figure 3 shown.

[0030] Embodiment three:

[0031] The structural components of the large-area BDAVBi OAF integrated together to build an OLED are as follows: a 150nm silver film is evaporated on a silicon substrate, topped by a 30nm PEDOT:PSS 8000 layer, and then a BDAVBi OAF light-emitting layer. Covering these layers is a thin 5nm layer of 1,3,5-tri(1-phenyl-1h-benzimidazol-2-yl)benzene (TPBi), a 5nm layer of cesium fluoride (CsF), and a 35nm silver film. In this device, the silver films have a dual purpose: they are electrodes that facilitate charge injection and act as optical microcavities within the device. The structural schematic is shown below. Figure 4 shown.

[0032] Embodiment 4:

[0033] Six BDAVBi OAFs with thicknesses of 61nm, 78nm, 90nm, 108nm, 143nm, and 202nm were embedded in the device in Example 3 as light-emitting layers, and the angle-resolved reflectance spectrum (ARR), electroluminescence (EL) performance, angle-resolved photoluminescence spectrum (ARRPL), and angle-resolved electroluminescence spectrum (ARREL) were tested respectively.

[0034] Angle-resolved reflectance (ARR) test of POLED devices: Angle-resolved reflectance spectra of POLEDs constructed with BDAVBiOAF layers of different thicknesses were measured at room temperature. In the POLED configured with a 90nm thick BDAVBi OAF layer, two different optical modes were observed, which exhibited anti-crossing behavior near the vibrational resonance centered at 452nm. This phenomenon is characteristic of a strong coupling state, as clearly demonstrated by the formation of the lower polariton branch (LP) and the upper polariton branch (UP). To further confirm the existence of strong coupling, we used a coupled resonator model to simulate the dispersion relations of the LP and UP branches. The simulation results show that the model dispersion curve (represented by the blue line) is in good agreement with the experimentally observed UP and LP branches, and the calculated Rabi splitting energy is approximately 522meV, as shown in the figure. Figure 5 More details of the ARR spectra of POLEDs embedded with different thicknesses are shown in Figure 6 As shown in AF.

[0035] Test of electroluminescence (EL) performance of POLED devices: Using Keithley 2400SCS semiconductor electrical test system, we first measured the POLED embedded with a 90nm thick BDAVBi OAF light-emitting layer. The maximum current efficiency and brightness of the device were about 10cd / A and 144,000cd / m 2 Taking advantage of the strong stability and excellent charge transport properties of OAF, this POLED device can withstand currents up to tens of volts, equivalent to 118A / cm 2 The external quantum efficiency (EQE) of the device is 89A / cm 2 The maximum value is 1.98% when the turn-on voltage is only 2V. The calculation shows that the internal quantum efficiency (IQE) of POLED based on BDAVBi OAF almost reaches the theoretical limit of 100%. Figure 7 As shown in AC.

[0036] The emission spectrum of POLED is tunable because it depends on the size of the microcavity; by varying the thickness of the BDAVBi OAF layer, a range of emission colors of POLED, including blue, cyan, green, yellow-green, yellow, and red, were successfully achieved. Figure 8 A shows their corresponding EL spectra. Figure 8 As shown in B, the full width at half maximum is less than 26nm. The EL performance of these six different color devices was further evaluated, and the data are shown in Fig. 9 As shown in AD.

[0037] The angle-resolved EL (ARREL) measurements of POLEDs with different emitting layer thicknesses were compared with the angle-resolved PL (ARRPL) of the same devices. Fig.10 AF. Due to the numerical aperture of the microscope objective used in the experiment, the ARREL spectrum is restricted to an angular range of ±15°, and the wavelength shift of the POLED does not exceed 5nm across the device when viewed from different angles. This phenomenon can be traced back to the LPB, which exhibits a significant wavelength shift in response to angle changes due to its more excitonic properties. This property is fundamental to the performance of the POLED, as the emission only passes through the LPB, ensuring significantly enhanced color stability across the entire viewing angle range. Fig.11 A illustrates the CIE color coordinate distribution of the six-color POLED, highlighted by white circular markers. Fig.11 B shows that the color gamut of the six-color POLED device (white triangle) accounts for 71.93% of the color gamut of the BT.2020 standard (red triangle).

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the claims of this patent application.

Claims

1. A method for synthesizing a distyryl derivative molecule, characterized in that: A distyryl derivative 4,4'-bis[4-(diphenylamino)phenyl]biphenyl molecule, namely BDAVBi, was designed and synthesized. The specific synthesis steps are as follows: S1. Mix ([1,1'-biphenyl]-4,4'-diylbis(methylene))bis(phosphonate)tetraethyl with NaH powder in tetrahydrofuran solution, cool in an ice bath at 0°C for 1h, then inject 4-(diphenylamine)benzaldehyde / tetrahydrofuran solution into the reaction ball, stir the reaction mixture at room temperature for 12h and pour into water, extract the product with CH2Cl2. Wash the mixed organic phase with water, dry with anhydrous MgSO4, filter, evaporate, and then recrystallize with n-hexane, and finally dry to obtain the product BDAVBi powder.

2. The method for synthesizing a distyryl derivative molecule according to claim 1, characterized in that: The reaction environment of step S1 must be anhydrous and oxygen-free, and the dosages of the drugs are: 1 mmol, 16.67 mmol, and 2 mmol respectively.

3. A distyryl derivative molecule BDAVBi, characterized in that: Prepared by the synthesis method described in claims 1 and 2, its structural formula is:

4. A method for preparing a novel organic assembly film, characterized in that: The distyryl derivative BDAVBi molecule as claimed in claim 3 is prepared by a simple spatially restricted self-assembly method to prepare a BDAVBi organic assembly film (BDAVBiOAF), the specific steps of which are as follows: S2. Use an analytical balance to accurately weigh the BDAVBi powder, then add it to dichloromethane (CH2Cl2) and dissolve it with slight heat. Add pure water to a glass petri dish, and then carefully transfer the BDAVBi / CH2Cl2 solution to the water surface. As the solvent evaporates, a large area of ​​OAF is formed on the water surface.

5. The method for preparing BDAVBi OAF according to claim 4, characterized in that: The concentration of the BDAVBi / CH2Cl2 solution in step S2 is 10 mg / mL, the size of the glass culture dish is 60 nm, the volume of pure water is 15 mL, and the volume of the BDAVBi / CH2Cl2 solution transferred to the water surface is 50 μL.

6. The method for preparing BDAVBi OAF according to claims 4 and 5, characterized in that: The area of ​​the prepared BDAVBiOAF can reach the centimeter level. The main absorption peak of these OAFs is 420nm, and the main emission peak is 503nm.

7. A novel assembled film single-emission base color narrow-band organic polariton light-emitting diode, characterized in that: From bottom to top, it includes a substrate, a lower reflector, a hole injection layer, a light-emitting layer, an electron injection layer and an upper reflector.

8. The novel assembled film single-emission basic color narrow-band organic polariton light-emitting diode as claimed in claim 7, characterized in that: The light-emitting layer is the large-area BDAVBi OAF layer as described in claims 4, 5 and 6, and the upper and lower reflectors are silver (Ag) films with different thicknesses.

9. The novel assembled film single-emission basic color narrow-band organic polariton light-emitting diode as claimed in claims 7 and 8, characterized in that: In angle-resolved reflectance spectroscopy measurements at room temperature, the signatures of a strong coupling state are revealed.

10. The novel assembled film single-emission basic color narrow-band organic polariton light-emitting diode as claimed in claims 7 and 8, characterized in that: In the electroluminescence performance measurement, the device with a specific thickness showed super strong electroluminescence performance, with a current density of up to 118A / cm 2 , the turn-on voltage is as low as 2V, and the external quantum efficiency can reach 1.98%.

11. The novel assembled film single-emission basic color narrow-band organic polariton light-emitting diode as claimed in claims 7 and 8, characterized in that: By varying the thickness of the BDAVBi OAF light-emitting layer, the emission spectrum can be tuned to include blue, cyan, green, yellow-green, yellow, and red.

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