Cluster doping enhanced sky blue light organic photodiode and its preparation method and application

Abstract

The present invention is applicable to the technical field of organic photodiodes, and provides a method for preparing a cluster-doping-enhanced sky-blue organic photodiode, comprising the following steps: adding a gold alkynyl complex and 1,4-(PPh2)2C6H4 to a dichloromethane solution and stirring; adding Cu(MeCN)4BF4 dissolved in a mixed solution of dichloromethane and acetone, stirring in the dark; placing the reactants in an n-pentane solution to obtain blue-green needle-shaped crystals; dissolving mCP and PO-T2T in a dichloromethane solution, oscillating and ultrasonically obtaining an exciplex solution; dissolving the crystals in the exciplex solution to obtain a cluster-doping-enhanced exciplex mixed solution; and preparing a cluster-doping-enhanced sky-blue organic photodiode. The present invention also provides a cluster-doping-enhanced sky-blue organic photodiode and its application. The preparation method of the present invention is simple to operate, takes less time, consumes less energy, has simple process requirements, and can prepare an organic photodiode with significantly improved brightness, high external quantum efficiency, high color purity, and good device stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic photodiodes, and in particular relates to a cluster-doping enhanced sky-blue light organic photodiode, a preparation method, and an application thereof. Background Art

[0002] Metal nanoclusters (NCs) possess excellent optoelectronic properties. Their low toxicity, high photoluminescence quantum yield, and simple synthesis conditions make them candidate materials for the next generation of light-emitting diodes. Their rich excited state composition enables their photoluminescence band to cover the entire visible light band, allowing them to be added to the emission layer (EmL) of existing organic photodiodes (OLEDs) to flexibly regulate the electroluminescent behavior of light-emitting devices.

[0003] However, in the specific doping strategy, the following issues need to be considered: 1) There are few existing high-performance metal nanoclusters, making it difficult to ensure the excellent optical properties of the emitter; 2) The thermally induced phase separation characteristics of metal clusters make them difficult to adapt to the evaporation processing technology, and their unique nanosize makes it difficult to form a uniform and stable thin film structure by spin coating; 3) When constructing OLED dopants, it is necessary to accurately consider their energy level matching to avoid the occurrence of inefficient energy transfer.

[0004] Therefore, under the premise of ensuring good film uniformity and color purity of OLED emitters, the emission intensity of electroluminescence should be improved, the power consumption of the device should be reduced, and the service life of the device should be guaranteed. This is also the key to cluster doping to enhance OLED electroluminescence. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a method for preparing a cluster-doping-enhanced sky-blue light organic photodiode, aiming to solve the problems raised in the above background technology.

[0006] The embodiment of the present invention is achieved by: a method for preparing a cluster doping enhanced sky blue light organic photodiode, comprising the following steps:

[0007] S1, the gold alkynyl complex AuC2R (R = C6H 11 O) and crystalline 1,4-(PPh2)2C6H4 were added to the dichloromethane solution and stirred at room temperature to obtain a mixture;

[0008] S2. Dissolve Cu(MeCN)4BF4 in a mixed solution of dichloromethane and acetone, and add the solution to the mixture obtained in S1. Stir the obtained reactant in the dark;

[0009] S3, placing the reactant obtained in S2 in n-pentane solution, and crystallizing by vapor diffusion method to obtain blue-green needle-shaped crystals;

[0010] S4, dissolving the electron acceptor material mCP and the electron donor material PO-T2T in a dichloromethane solution, shaking and ultrasonicating, and then allowing to stand to obtain an exciplex solution;

[0011] S5, dissolving the crystals obtained in S3 in the exciplex solution obtained in S4, sonicating, and then allowing to stand to obtain a cluster-doping-enhanced exciplex mixed solution;

[0012] S6. Preliminary preparation of sky-blue organic photodiodes based on cluster doping enhancement:

[0013] S61, cleaning the ITO conductive glass and performing ultraviolet ozone treatment;

[0014] S62, spin coating a PEDOT:PSS solution on the treated ITO glass, followed by annealing to obtain a hole injection layer, and then transferring the layer to a glove box filled with N2 gas;

[0015] S63, spin-coating the cluster-doping enhanced exciplex mixed solution obtained in S5 on the PEDOT:PSS layer as a light-emitting layer;

[0016] S7. Transfer the product obtained in S6 into a vacuum chamber, and sequentially deposit CN-T2T, LiF, and Al layers by thermal evaporation, wherein the CN-T2T layer serves as an electron transport layer and a hole blocking layer, and the LiF and Al layers serve as top electrodes, thereby obtaining the cluster-doping enhanced sky-blue light organic photodiode.

[0017] Preferably, in S1, the stirring speed is 580-620 r / min and the stirring time is 12-18 min.

[0018] Preferably, in S2, the stirring speed is 780-820 r / min and the stirring time is 25-35 min.

[0019] Preferably, in S4, after the electron acceptor material mCP and the electron donor material PO-T2T are dissolved in the dichloromethane solution, the concentration of mCP is 1.5 mg / mL, the concentration of PO-T2T is 1.5 mg / mL, the shaking time is 1-3 min, and the ultrasonic time is 1-3 min.

[0020] Preferably, in S5, the crystals obtained in S3 are dissolved in the exciplex solution obtained in S4, the concentration of the crystals is 1.0 mg / mL, and the ultrasonication time is 1-3 min.

[0021] Preferably, in S61, the step of cleaning the ITO conductive glass is specifically: cleaning the ITO conductive glass with soap, deionized water, ethanol, chloroform, acetone and isopropyl alcohol in sequence;

[0022] In S62, the rotation speed of the spin coating is 1800-2200 r / min, the temperature during the spin coating process is 20-25°C, the humidity is 40-50%, and the temperature of the annealing is 165-175°C, and the time is 25-35 min.

[0023] In S63, the rotation speed of the spin coating is 1800-2200 r / min, the temperature during the spin coating process is 20-23° C., and the concentrations of water vapor and oxygen do not exceed 5 ppm.

[0024] Preferably, in S7, the evaporation rate of CN-T2T and LiF is 0.05-0.15 nm / s, the thickness of CN-T2T is 35-45 nm, and the thickness of LiF is 1-2 nm; the evaporation rate of Al is 1-2 nm / s, and the thickness is 100-200 nm.

[0025] Another object of the embodiment of the present invention is to provide a cluster-doping-enhanced sky-blue light organic photodiode, which is prepared by the above-mentioned preparation method.

[0026] Another object of the embodiments of the present invention is to provide an application of a cluster-doping-enhanced sky-blue light organic photodiode in the preparation of a light-emitting device.

[0027] In the embodiment of the present invention, metal nanoclusters Au6Cu2 and sky-blue light-emitting exciplexes mCP:PO-T2T are used to construct cluster-doping-enhanced sky-blue organic light-emitting diodes. The electroluminescence curves of the selected metal nanoclusters and the exciplexes are highly overlapped, and host-guest energy transfer conditions are met. A sky-blue organic light-emitting diode with an electroluminescence (EL) peak of 480nm is prepared using a mixed solution of cluster-doping-enhanced exciplexes as the emission layer. The device has an EL peak of 1887cd m -2 The high brightness and high external quantum yield (EQE) of 0.767% are 2.37 times and 1.65 times that of the undoped device, respectively. At the same time, the similar electroluminescence spectrum ensures good color purity of the device, and the doping system also enhances the service life of the device.

[0028] The preparation method of the embodiment of the present invention is simple to operate, takes less time, consumes less energy, and has simple process requirements. The prepared cluster-doping enhanced sky-blue light organic photodiode has significantly improved brightness, high external quantum efficiency, high color purity, and good device stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The absorption spectrum and photoluminescence spectrum of the metal nanocluster Au6Cu2 provided in Example 1 of the present invention;

[0030] Figure 2Transmission electron microscope (TEM) image of the metal nanoclusters Au6Cu2 provided in Example 1 of the present invention;

[0031] Figure 3 Atomic force microscopy (AFM) images of exciplex films of doped and undoped metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention;

[0032] Figure 4 Schematic diagram of the photoluminescence quantum yield (PLQY) of the exciplex films doped with and undoped with metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention;

[0033] Figure 5 Schematic diagram of the energy level structure of the cluster-doping enhanced sky-blue light organic photodiode provided in Example 1 of the present invention;

[0034] Figure 6 The electroluminescence spectra of the cluster-doping enhanced sky-blue organic photodiode provided in Example 1 of the present invention under different voltage biases;

[0035] Figure 7 Brightness-voltage-current density curves of sky-blue organic photodiodes doped with and undoped with metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention;

[0036] Figure 8 Brightness-external quantum efficiency curves of sky-blue organic photodiodes doped with and undoped with metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention;

[0037] Figure 9 The sky blue light organic photodiode of the doped and undoped metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention has an average power of 50 cdm -2 Brightness decay curve under brightness;

[0038] Figure 10 This is an optical photograph of the sky blue organic photodiode at maximum brightness after being doped with metal nanoclusters provided in Example 1 of the present invention;

[0039] Figure 11 This is an optical photograph of the sky blue light organic photodiode without metal nanoclusters provided in Comparative Example 1 at maximum brightness. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0042] Example 1: A cluster doping-enhanced sky-blue organic photodiode, the preparation method of which specifically comprises the following steps:

[0043] S1. Take 96.0 mg of gold alkynyl complex AuC2R (R = C6H 11 0) was dissolved in 5 mL of chromatographically pure dichloromethane solution, and then 46.0 mg of crystalline 1,4-(PPh2)2C6H4 was added and stirred on a magnetic stirrer at a speed of 600 r / min for 15 min;

[0044] S2, 38.0 mg of Cu(MeCN)4BF4 was dissolved in a mixed solution of 5 mL of chromatographically pure dichloromethane and 3 mL of acetone, and then added to S1. The resulting reaction mixture was stirred at 800 rpm on a magnetic stirring table at 20°C in the dark for 30 min;

[0045] S3. Place the solution obtained in S2 in n-pentane solution with a slightly open container. After standing for 96 hours in a sealed container at 5°C, collect the blue-green needle-like crystals appearing on the inner wall of the container, which are metal nanoclusters Au6Cu2.

[0046] S4. Dissolve 3.0 mg of the electron acceptor material mCP and 3.0 mg of the electron donor material PO-T2T in 1 mL of chromatographically pure dichloromethane solution, stir vigorously to ensure that the powder is completely dissolved, then mix them in a volume ratio of 1:1 and shake for 1 minute, then sonicate for 1 minute and let stand to obtain a uniformly distributed exciplex mixed solution;

[0047] S5, dissolving 1.0 mg of the crystals prepared by S3 in 1 mL of the exciplex mixed solution prepared by S4, and then sonicating for 1 min to ensure that the crystals are completely dissolved, to obtain a cluster-doping-enhanced exciplex mixed solution;

[0048] S6. The ITO conductive glass was cleaned with soap, deionized water, ethanol, chloroform, acetone, and isopropyl alcohol in sequence, and then subjected to UV-ozone treatment. A PEDOT:PSS solution (Baytron PVPAl 4083) was spin-coated on the treated ITO glass through a filter, followed by annealing to obtain a hole injection layer. The substrate was then transferred to a glove box filled with N2 gas. The cluster-doped enhanced exciplex mixed solution prepared in S5 was then spin-coated on the ITO glass substrate on which the PEDOT:PSS had been spin-coated.

[0049] PEDOT:PSS was spin-coated on ITO at a speed of 2000 r / min for 30 seconds and annealed at 170°C for 30 minutes. The temperature during the spin-coating process was 21°C and the humidity was 30%. The cluster-doping-enhanced exciplex mixed solution was rotated at a speed of 2000 r / min for 30 seconds. The temperature during the spin-coating process was maintained at 20°C, and the water vapor concentration and oxygen concentration were 5 ppm.

[0050] S7. The electron transport layer CN-T2T, the electron injection layer LiF, and the metal electrode Al are evaporated onto a glass substrate by evaporation to obtain a cluster-doping enhanced sky blue light organic photodiode. The evaporation rate of CN-T2T and LiF is 0.1 nm / s, and the final thicknesses are 40 nm and 1 nm, respectively; the evaporation rate of Al is 1 nm / s, and the final thickness is 100 nm.

[0051] Comparative Example 1: A sky blue light organic photodiode, the preparation method of which comprises the following steps:

[0052] S1. Dissolve 3.0 mg of the electron acceptor material mCP and 3.0 mg of the electron donor material PO-T2T in 1 mL of chromatographically pure dichloromethane solution, stirring vigorously to ensure that the powder is completely dissolved. Then, mix them in a volume ratio of 1:1 and shake for 1 minute. Then, sonicate for 1 minute and let it stand to obtain a uniformly distributed exciplex mixed solution.

[0053] S2. The ITO conductive glass was cleaned with soap, deionized water, ethanol, chloroform, acetone, and isopropyl alcohol in sequence, and then subjected to UV-ozone treatment. A PEDOT:PSS solution (Baytron PVPAl 4083) was spin-coated on the treated ITO glass through a filter, followed by annealing to obtain a hole injection layer. The substrate was then transferred to a glove box filled with N2 gas. The exciplex mixture solution prepared in S1 was then spin-coated on the PEDOT:PSS-coated ITO glass substrate.

[0054] PEDOT:PSS was spin-coated on ITO at a speed of 2000 r / min for 30 seconds and annealed at 170°C for 30 minutes. The temperature during the spin-coating process was 21°C and the humidity was 30%. The exciplex mixture solution was spin-coated at a speed of 2000 r / min for 30 seconds. The temperature during the spin-coating process was maintained at 20°C, and the water vapor concentration and oxygen concentration were 5 ppm.

[0055] S3. The electron transport layer CN-T2T, the electron injection layer LiF, and the metal electrode Al are evaporated onto the glass substrate by an evaporation operation to obtain the sky blue light organic photodiode.

[0056] Performance testing:

[0057] The blue-green needle-shaped crystals obtained in Example 1 were analyzed, and the absorption spectrum and photoluminescence spectrum were obtained as follows: Figure 1 As shown, according to Figure 1 It can be seen that the synthesized blue-green needle-shaped crystals have the characteristic absorption peaks and emission peaks of metal nanoclusters, ensuring the high purity of the material; the transmission electron microscope (TEM) image is as follows Figure 2 As shown, according to Figure 2 It can be seen that the size distribution of the synthesized metal nanoclusters is uniform;

[0058] The thin film formed by the cluster doping enhanced exciplex mixed solution in Example 1 and the thin film formed by the exciplex mixed solution in Comparative Example 1 were analyzed, and the atomic force microscope (AFM) images were obtained as shown in FIG. Figure 3 As shown, according to Figure 3 It can be seen that the exciplex film after doping with metal nanoclusters maintains its original low roughness, which is conducive to smooth carrier injection between the transport layer and the emission layer; the photoluminescence quantum yield (PLQY) is shown in the figure below. Figure 4 As shown;

[0059] The cluster doping enhanced sky blue light organic photodiode prepared in Example 1 was analyzed to obtain the energy level structure diagram as shown below: Figure 5 As shown, according to Figure 5 It can be seen that the semiconductor energy level of the cluster emitter can be used to design the device structure based on the measured value; the electroluminescence spectra under different voltage bias are obtained as follows Figure 6 As shown, according to Figure 6 It can be seen that the electroluminescence peak of the device remains stable at 480nm from low voltage to maximum brightness voltage;

[0060] The cluster doping enhanced sky blue light organic photodiode prepared in Example 1 and the sky blue light organic photodiode prepared in Comparative Example 1 were compared and analyzed to obtain the brightness-voltage-current density curve as shown in FIG. Figure 7 As shown, the brightness-external quantum efficiency curve is as follows Figure 8 As shown, according to Figure 7 、 Figure 8 It can be seen that the brightness and external quantum efficiency of the device after doping with metal nanoclusters are significantly improved; -2 The brightness attenuation curve under brightness is as follows Figure 9 As shown, according to Figure 9 It can be seen that the brightness of the device after doping with metal nanoclusters decays significantly slower and the device stability is improved. This is because the doped metal nanoclusters reduce the concentration quenching of the exciplex; the optical photograph at maximum brightness is shown in the figure below. Figure 10 、 Figure 11 As shown, according to Figure 10 、 Figure 11 It can be seen that the maximum brightness of the device after doping with metal nanoclusters is significantly improved;

[0061] In summary, the present invention proposes a method for constructing a cluster-doped enhanced sky-blue organic photodiode using metal clusters Au6Cu2 and exciplexes mCP:PO-T2T. Metal nanoclusters with the same emission band significantly increase the photoluminescence quantum yield of the sky-blue exciplex from 20.01% to 29.83%, significantly enhancing the luminescence intensity of the film. At the same time, atomic force microscopy shows that the introduction of clusters maintains the flatness of the film. Furthermore, the cluster-doped exciplex system is used as the emission layer to prepare a sky-blue organic light-emitting diode with an electroluminescence (EL) wavelength of 480nm. The device has an EL wavelength of 1887cd m -2 The high brightness and high external quantum yield of 0.767% are 2.37 times and 1.65 times that of the undoped device, respectively. At the same time, the color purity of the device is good. At the same time, the doping of the clusters enhances the service life of the sky blue organic diode. In the case of no encapsulation, the device has a high brightness of 50 cd m -2 The brightness decay time under brightness is extended from 6.23min to 13.71min.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a cluster doping enhanced sky blue light organic photodiode, characterized in that: The following steps are involved: S1, the gold alkynyl complex AuC2R (R = C6H 11 O) and crystalline 1,4-(PPh2)2C6H4 were added to the dichloromethane solution and stirred at room temperature to obtain a mixture; S2. Dissolve Cu(MeCN)4BF4 in a mixed solution of dichloromethane and acetone, and add the solution to the mixture obtained in S1. Stir the obtained reactant in the dark; S3, placing the reactant obtained in S2 in n-pentane solution, and crystallizing by vapor diffusion method to obtain blue-green needle-shaped crystals; S4, dissolving mCP and PO-T2T in a dichloromethane solution, shaking and sonicating, and then allowing to stand to obtain an exciplex solution; S5, dissolving the crystals obtained in S3 in the exciplex solution obtained in S4, sonicating, and then allowing to stand to obtain a cluster-doping-enhanced exciplex mixed solution; S6. Preliminary preparation of sky-blue organic photodiodes based on cluster doping enhancement: S61, cleaning the ITO conductive glass and performing ultraviolet ozone treatment; S62, spin coating a PEDOT:PSS solution on the treated ITO glass, followed by annealing to obtain a hole injection layer, and then transferring the layer to a glove box filled with N2 gas; S63, spin-coating the cluster-doping enhanced exciplex mixed solution obtained in S5 on the PEDOT:PSS layer as a light-emitting layer; S7. Transfer the product obtained in S6 into a vacuum chamber, and sequentially deposit CN-T2T, LiF, and Al layers by thermal evaporation, wherein the CN-T2T layer serves as an electron transport layer and a hole blocking layer, and the LiF and Al layers serve as top electrodes, thereby obtaining the cluster-doping enhanced sky-blue light organic photodiode.

2. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S1, the stirring speed is 580-620 r / min and the stirring time is 12-18 min.

3. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S2, the stirring speed is 780-820 r / min and the stirring time is 25-35 min.

4. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S4, after mCP and PO-T2T are dissolved in dichloromethane solution, the concentration of mCP is 1.5 mg / mL, the concentration of PO-T2T is 1.5 mg / mL, the shaking time is 1-3 min, and the ultrasonic time is 1-3 min.

5. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S5, the crystals obtained in S3 are dissolved in the exciplex solution obtained in S4. The concentration of the crystals is 1.0 mg / mL, and the ultrasonic time is 1-3 min.

6. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S61, the steps of cleaning the ITO conductive glass are specifically as follows: cleaning the ITO conductive glass with soap, deionized water, ethanol, chloroform, acetone and isopropyl alcohol in sequence; In S62, the spin coating speed is 1800-2200 r / min, the temperature during the spin coating process is 20-25°C, the humidity is 40-50%, and the annealing temperature is 165-175°C, and the time is 25-35 minutes; In S63, the rotation speed of the spin coating is 1800-2200 r / min, the temperature during the spin coating process is 20-23° C., and the concentrations of water vapor and oxygen do not exceed 5 ppm.

7. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S7, the evaporation rate of CN-T2T and LiF is 0.05-0.15 nm / s, the thickness of CN-T2T is 35-45 nm, and the thickness of LiF is 1-2 nm; the evaporation rate of Al is 1-2 nm / s, and the thickness is 100-200 nm.

8. A cluster doping enhanced sky blue light organic photodiode, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the cluster-doping-enhanced sky-blue organic photodiode according to claim 8 in preparing a light-emitting device.

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