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

Abstract

The invention is applicable to the technical field of organic photodiodes, and provides a preparation method of a cluster doping enhanced sky-blue light organic photodiode, which comprises the following steps: adding a gold alkynyl complex and 1, 4-(PPh2) 2C6H4 into a dichloromethane solution, and stirring; adding Cu (MeCN) 4BF4 dissolved in a mixed solution of dichloromethane and acetone, and stirring in a dark place; placing the reactant in an n-pentane solution to obtain a blue-green needle-like crystal; the preparation method comprises the following steps: dissolving mCP and PO-T2T in a dichloromethane solution, and carrying out oscillation ultrasonic treatment to obtain an exciplex solution; dissolving the crystal in an exciplex solution to obtain a cluster doping enhanced exciplex mixed solution; and preparing the sky-blue light organic photodiode based on cluster doping enhancement. The invention also provides a cluster doping enhanced sky-blue light organic photodiode and application thereof. The preparation method is simple in operation, less in time consumption, low in energy consumption and simple in process requirement, the brightness of the prepared organic photodiode is obviously improved, the external quantum efficiency is high, the color purity is high, and the device stability is good.

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 and a preparation method and application thereof. Background Art

[0002] Metal nanoclusters (NCs) have excellent optoelectronic properties. Their low toxicity, high photoluminescence quantum yield and simple synthesis conditions make them candidate materials for the new generation of light-emitting diodes. The rich excited state composition makes their photoluminescence band cover the entire visible light band, so that they can 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 it difficult to adapt them 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 device power consumption should be reduced, and the device service life 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-mentioned background technology.

[0006] The embodiment of the present invention is implemented as follows: a method for preparing a cluster doping enhanced sky blue light organic photodiode comprises 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, dissolving Cu(MeCN)4BF4 in a mixed solution of dichloromethane and acetone, and then adding the solution to the mixture obtained in S1, and stirring the obtained reactant in the dark;

[0009] S3, placing the reactant obtained in S2 in a n-pentane solution, and crystallizing by a 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 standing to obtain an exciplex solution;

[0011] S5, dissolving the crystal obtained in S3 in the exciplex solution obtained in S4, and allowing to stand after ultrasonication 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 time is 12-18 min.

[0018] Preferably, in S2, the stirring speed is 780-820 r / min and the 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 oscillation time is 1-3 min, and the ultrasound 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 ultrasonic 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 isopropanol 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 annealing temperature 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 concentration of water vapor and oxygen does not exceed 5 ppm.

[0024] Preferably, in S7, the evaporation rates of CN-T2T and LiF are 0.05-0.15 nm / s, the thickness of CN-T2T is 35-45 nm, 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 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] The embodiment of the present invention uses metal nanoclusters Au6Cu2 and sky blue light emitting exciplexes mCP:PO-T2T to construct a cluster doping enhanced sky blue light organic light emitting diode. The electroluminescence curves of the selected metal nanoclusters and the exciplexes are highly overlapped and have host-guest energy transfer conditions. A sky blue light organic light emitting diode with an electroluminescence (EL) peak of 480nm is prepared by using a cluster doping enhanced exciplex mixed solution as an emission layer. The device has a luminescent property 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 the 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 little time, consumes low energy, and has simple process requirements. The prepared cluster-doped 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 2A transmission electron microscope (TEM) image of the metal nanocluster Au6Cu2 provided in Example 1 of the present invention;

[0031] Figure 3 Atomic force microscope (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 film doped with and undoped with metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention;

[0033] Figure 5 A 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 light 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 light organic photodiodes doped with and without 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 light organic photodiodes doped with and without metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention;

[0037] Fig. 9 The sky blue light organic photodiodes of the doped and undoped metal nanoclusters provided in Example 1 and Comparative Example 1 of the present invention have an average light intensity of 50 cdm. -2 Brightness decay curve under brightness;

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

[0039] Fig.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 solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 in conjunction with specific embodiments.

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

[0043] S1. Take 96.0 mg of the gold alkynyl complex AuC2R (R = C6H 11 0) dissolved in 5 mL of chromatographically pure dichloromethane solution, then added 46.0 mg of crystalline 1,4-(PPh2)2C6H4, 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, and the resulting reaction mixture was stirred at 800 r / min on a magnetic stirring table at 20°C in the dark for 30 min;

[0045] S3, the solution obtained in S2 was slightly opened and placed in n-pentane solution, sealed and left to stand at 5°C for 96 hours, and then the blue-green needle-shaped crystals appearing on the inner wall of the container were collected, which were metal nanoclusters Au6Cu2;

[0046] S4, 3.0 mg of the electron acceptor material mCP and 3.0 mg of the electron donor material PO-T2T were dissolved in 1 mL of chromatographically pure dichloromethane solution, stirred vigorously to ensure that the powder was completely dissolved, and then mixed in a volume ratio of 1:1 and shaken for 1 min, and then ultrasonicated for 1 min and allowed to 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, washing the ITO conductive glass with soap, deionized water, ethanol, chloroform, acetone and isopropanol in turn, and treating it with ultraviolet ozone; spin coating the PEDOT:PSS solution (Baytron PVPAl 4083) on the treated ITO glass through a filter head, and then annealing to obtain a hole injection layer, and then transferring the substrate to a glove box filled with N2 gas; and then coating the cluster doping enhanced exciplex mixed solution prepared in S5 on the ITO glass substrate on which PEDOT:PSS has been spin-coated by spin coating;

[0049] PEDOT:PSS was spin-coated on ITO at a rotation speed of 2000 r / min and a rotation time of 30 s, and annealed at 170°C for 30 min. During the spin-coating process, the temperature was 21°C and the humidity was 30%. The rotation speed of the cluster-doped enhanced exciplex mixed solution was 2000 r / min and the rotation time was 30 s. During the spin-coating process, the temperature should be kept at 20°C, and the water vapor concentration and oxygen concentration should be 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 operation to obtain a cluster doping enhanced sky blue light organic photodiode, wherein the evaporation rate of CN-T2T and LiF is 0.1nm / s, and the final thickness is 40nm and 1nm respectively; the evaporation rate of Al is 1nm / s, and the final thickness is 100nm.

[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, stir vigorously to ensure that the powder is completely dissolved, then mix them in a volume ratio of 1:1 and shake for 1 min, then ultrasonicate for 1 min and let stand to obtain a uniformly distributed exciplex mixed solution;

[0053] S2, washing the ITO conductive glass with soap, deionized water, ethanol, chloroform, acetone and isopropanol in turn, and treating it with ultraviolet ozone; spin coating the PEDOT:PSS solution (Baytron PVPAl 4083) on the treated ITO glass through a filter head, and then annealing to obtain a hole injection layer, and then transferring the substrate to a glove box filled with N2 gas; and then coating the excited complex mixed solution prepared in S1 on the ITO glass substrate on which the PEDOT:PSS has been spin-coated by spin coating;

[0054] PEDOT:PSS was spin-coated on ITO at a rotation speed of 2000 r / min and a rotation time of 30 s, and annealed at 170°C for 30 min. During the spin-coating process, the temperature was 21°C and the humidity was 30%. The rotation speed of the excited complex mixed solution was 2000 r / min and the rotation time was 30 s. During the spin-coating process, the temperature should be kept at 20°C, and the water vapor concentration and oxygen concentration should be 5 ppm.

[0055] S3, evaporating the electron transport layer CN-T2T, the electron injection layer LiF, and the metal electrode Al onto the glass substrate by evaporation operation, thereby obtaining the sky blue light organic photodiode.

[0056] Performance Test:

[0057] The blue-green needle-shaped crystals obtained in Example 1 were analyzed to obtain absorption spectra and photoluminescence spectra as shown in FIG. 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 to obtain atomic force microscope (AFM) images 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 an energy level structure schematic diagram as shown in 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 biases 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 Fig. 9 As shown, according to Fig. 9 It can be seen that the brightness decay of the device after doping with metal nanoclusters is 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 as follows Fig.10 , Fig.11 As shown, according to Fig.10 , Fig.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 light organic photodiode using metal clusters Au6Cu2 and exciplexes mCP:PO-T2T. The metal nanoclusters with the same emission band significantly increase the photoluminescence quantum yield of the sky-blue light exciplexes 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 the clusters maintains the flatness of the film. Furthermore, the cluster-doped exciplex system is used as the emission layer to prepare a sky-blue light organic light-emitting diode with an electroluminescence (EL) wavelength of 480nm. The device has a wavelength of 1887cd m -2 The high brightness and high external quantum yield of 0.767% are 2.37 times and 1.65 times of those of undoped devices, respectively. At the same time, the color purity of the device is good. The doping of 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 protection scope 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, dissolving Cu(MeCN)4BF4 in a mixed solution of dichloromethane and acetone, and then adding the solution to the mixture obtained in S1, and stirring the obtained reactant in the dark; S3, placing the reactant obtained in S2 in a n-pentane solution, and crystallizing by a vapor diffusion method to obtain blue-green needle-shaped crystals; S4, dissolving the electron acceptor material mCP and the electron donor material PO-T2T in a dichloromethane solution, shaking and ultrasonicating, and then standing to obtain an exciplex solution; S5, dissolving the crystal obtained in S3 in the exciplex solution obtained in S4, and allowing to stand after ultrasonication 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 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 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.

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 step of cleaning the ITO conductive glass is specifically: cleaning the ITO conductive glass with soap, deionized water, ethanol, chloroform, acetone and isopropanol in sequence; 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%, the temperature of the annealing is 165-175°C, and the time is 25-35 min.

7. 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 concentration of water vapor and oxygen does not exceed 5 ppm.

8. The method for preparing a cluster doping enhanced sky blue light organic photodiode according to claim 1, characterized in that: In S7, the evaporation rates of CN-T2T and LiF are 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.

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

10. Use of the cluster-doping enhanced sky blue light organic photodiode as claimed in claim 8 in preparing a light-emitting device.

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