CN113948665A - Preparation method of film layer, light-emitting diode and preparation method of light-emitting diode - Google Patents

Preparation method of film layer, light-emitting diode and preparation method of light-emitting diode Download PDF

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CN113948665A
CN113948665A CN202010681387.7A CN202010681387A CN113948665A CN 113948665 A CN113948665 A CN 113948665A CN 202010681387 A CN202010681387 A CN 202010681387A CN 113948665 A CN113948665 A CN 113948665A
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layer
functional layer
electric field
forming
light
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王天锋
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TCL Technology Group Co Ltd
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    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/10Deposition of organic active material
    • H10K71/12Deposition of organic active material using liquid deposition, e.g. spin coating
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14Carrier transporting layers
    • H10K50/15Hole transporting layers
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14Carrier transporting layers
    • H10K50/16Electron transporting layers
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17Carrier injection layers
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17Carrier injection layers
    • H10K50/171Electron injection layers
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/10Deposition of organic active material
    • H10K71/191Deposition of organic active material characterised by provisions for the orientation or alignment of the layer to be deposited

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Abstract

The invention provides a preparation method of a film layer, a light-emitting diode and a preparation method of the light-emitting diode. The preparation method of the film layer comprises the following steps: the spin coating solution is spin coated on a substrate, and an electric field is applied to the substrate during the spin coating. The film is formed by spin coating under the action of an electric field, so that the wettability of the spin coating solution on the substrate is improved, the uniform spreading of the spin coating solution is promoted, and a uniform and smooth high-quality film layer is obtained. The preparation method of the light-emitting diode comprises the following steps: forming a first functional layer on the bottom electrode; forming a light emitting layer on the first functional layer; forming a second functional layer on the light emitting layer; forming a top electrode on the second functional layer; the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light-emitting layer adopt the preparation method. Therefore, the film quality of the first functional layer and/or the second functional layer and the carrier migration efficiency thereof are improved, so that the light emitting performance of the light emitting diode prepared by the method is further improved.

Description

Preparation method of film layer, light-emitting diode and preparation method of light-emitting diode
Technical Field
The invention belongs to the technical field of display, and particularly relates to a preparation method of a film layer, a light emitting diode and a preparation method of the light emitting diode.
Background
The spin-coating method is a film layer preparation method, has the advantages of accurate and controllable film layer thickness, high cost performance, energy conservation, low pollution and the like, and is commonly used for preparing functional film layers of light-emitting diodes. The conventional spin coating process includes: dropping the slurry on the substrate, rotating the spin coater, spreading the slurry on the substrate under the action of centrifugal force, and volatilizing the solvent to form a film and crystallizing under the action of thermal force to form a functional film layer of the device. However, since the spin-coating solution needs to form a film on the substrate, the wettability of the spin-coating solution on the substrate directly affects the quality of the film, and how to improve the wettability of the spin-coating solution on the substrate is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
One of the objectives of the present invention is to provide a method for preparing a film layer, which is to improve the wettability of a spin-on solution on a substrate.
The invention aims to provide a preparation method of a light-emitting diode and the light-emitting diode prepared by the preparation method.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a film, comprising: a spin-coating solution is spin-coated on a substrate, and an electric field is applied to the substrate during the spin-coating process.
In a second aspect, the present invention provides a method for manufacturing a light emitting diode, including the following steps:
forming a first functional layer on the bottom electrode;
forming a light emitting layer on the first functional layer;
forming a second functional layer on the light emitting layer;
forming a top electrode on the second functional layer;
the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light-emitting layer adopt the preparation method of the film layer.
In a third aspect, the invention provides a light emitting diode, which is prepared by the preparation method of the light emitting diode.
According to the preparation method of the film, the spin-coating solution is spin-coated on the substrate, an electric field is applied during spin-coating, and the spin-coating film is formed under the action of the electric field, so that the wettability of the spin-coating solution on the substrate is improved, the uniform spreading of the spin-coating solution is promoted, and a uniform and flat high-quality film can be obtained.
According to the preparation method of the light-emitting diode provided by the invention, the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light-emitting layer adopt the preparation method of the film layer, so that the film layer quality of the first functional layer and/or the second functional layer is improved, meanwhile, the molecular orientation of the film layer is improved, the carrier injection into the film layer is promoted, the carrier migration efficiency of the first functional layer and/or the second functional layer is improved, and the light-emitting performance of the light-emitting diode prepared by the method is further improved.
The light-emitting diode provided by the invention is prepared by the preparation method, has good carrier migration efficiency, good light-emitting performance and long service life.
Drawings
FIG. 1 is a schematic diagram of the manner in which a constant electric field is applied to prepare a film according to an embodiment of the present invention;
FIG. 2 is a schematic view of an alternative electric field applied during the preparation of a film according to another embodiment of the present invention;
fig. 3 is a flowchart of a method for manufacturing a light emitting diode according to an embodiment of the invention;
FIG. 4 is a schematic diagram of the mode of action of the electric field in one embodiment of the present invention;
FIG. 5 is a schematic diagram of the mode of action of the electric field in another embodiment of the present invention;
FIG. 6 is a schematic diagram of the mode of action of an electric field in another embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a light emitting diode according to an embodiment of the present invention;
FIG. 8 is a J-V curve of the light emitting diodes of example 1 and comparative examples 1-2;
FIG. 9 shows the results of external quantum efficiency tests of the light emitting diodes of example 1 and comparative examples 1 to 2;
FIG. 10 is a graph of luminance vs. voltage (L-V) for the LEDs of example 1 and comparative examples 1-2.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
A method of preparing a film comprising: the spin coating solution is spin coated on a substrate, and an electric field is applied to the substrate during the spin coating.
According to the preparation method of the film layer provided by the embodiment of the invention, the spin coating solution is spin-coated on the substrate, an electric field is applied during spin coating, and the film is formed by spin coating under the action of the electric field, so that the wettability of the spin coating solution on the substrate is improved, the uniform spreading of the spin coating solution is promoted, and the uniform and flat high-quality film layer can be obtained.
Specifically, the substrate serves as a base layer for depositing a spin-on solution to form a film layer. The substrate may be selected from materials conventional in the art, and embodiments of the present invention are not particularly limited thereto.
The composition and properties of the spin-coating solution can be referred to the actually prepared film layer, which is not particularly limited in the embodiments of the present invention.
The step of spin-coating the spin-coating solution on the substrate and spin-coating parameters thereof may be performed by referring to conventional techniques in the art, and in some embodiments, the spin-coating method is set to a rotation speed of 3000 to 5000 rpm.
In addition to the spin coating, an electric field is applied during spin coating. The film is formed by spin coating under the action of an electric field, so that the wettability of a spin coating solution on a substrate is improved, and the quality of a film layer is improved.
The contact angle of the spin-coating solution and the substrate is in negative correlation with the electric field intensity, the infiltration performance of the spin-coating solution on the substrate is influenced by the intensity of the electric field, and the higher the electric field intensity is on the premise of ensuring that the film layer is safe and not broken down, the better the infiltration performance of the spin-coating solution on the substrate is. In some embodiments, the electric field is strongDegree of 103~107V/cm. The electric field intensity is controlled in the range, so that the spin coating solution is promoted to be uniformly spread, the performance of the film layer is flexibly adjusted, the substrate can be prevented from being punctured due to overhigh electric field intensity, and the process safety is ensured.
The frequency of the electric field also influences the wetting performance of the spin-coating solution on the substrate to a certain extent, the surface tension of the spin-coating solution is mainly influenced by intermolecular force, unidirectional vibration and overall movement of solute molecules can be promoted under the action of the electric field, different masses of the solute molecules and the relative positions of the electric branched chains are changed, the original copolymerization balance of the solute molecules is damaged, the surface tension is further reduced, and the wetting performance of the spin-coating solution is enhanced. In some embodiments, the frequency of the electric field is between 1Hz and 10GHz, preferably between 10kHz and 10 GHz. Too high or too low frequency of the electric field is not favorable for improving the wetting property of the spin coating solution.
As shown in fig. 1 and 2, the electric field may be selected to be a constant electric field or an alternating electric field, and particularly, the polarity of the solute of the spin-coating solution may be referred to.
In some embodiments, the solute of the spin-on solution is a polar molecule and the electric field is a constant electric field. The polar molecules have high response to the electric field, and the performance of the film layer can be effectively adjusted by adopting a constant electric field with smaller electric field intensity. "polar molecule" refers to a molecule covalently bonded in polar form, with the centers of the positive and negative charges not coinciding to form a dipole. The positive and negative charges of the polar molecules are acted by the electric field force to generate couple moment to rotate, and the resultant force at any point of the couple action surface is zero; therefore, the translation state of the object is not changed, and only the rotation state of the object is changed.
In some embodiments, the solute of the spin-on solution is a non-polar molecule and the electric field is an alternating electric field. The non-polar molecules have small response to the electric field, and the performance of the film layer can be effectively adjusted by adopting an alternating electric field with larger electric field intensity. The term "nonpolar molecule" refers to a molecule having a dipole moment μ equal to 0, i.e., a molecule in which atoms are covalently bonded to each other, the charge distribution in the molecule is uniform, and the centers of positive and negative charges coincide with each other.
The electric field can be arranged in any direction and position of the spin-coating sample, and can be flexibly adjusted according to the type of the actually prepared device. In some embodiments, the electric field has a field strength direction perpendicular or parallel to the substrate.
In addition, the electric field can be a uniform electric field or a non-uniform electric field, and can be flexibly selected according to actual production conditions. In some embodiments, the electric field is uniform across the spin-coated surface of the substrate to further enhance the molecular orientation of the prepared film.
In conclusion, by the method, the film is formed by spin coating under the action of the electric field, so that the wettability of the spin coating solution on the substrate is effectively improved, the uniform spreading of the spin coating solution is promoted, and a uniform and smooth high-quality film layer is obtained.
Based on the technical scheme, the embodiment of the invention also provides a preparation method of the light-emitting diode and the light-emitting diode prepared by the preparation method.
As shown in fig. 3, an embodiment of the present invention provides a method for manufacturing a light emitting diode, including the following steps:
s01, forming a first functional layer on the bottom electrode;
s02, forming a light-emitting layer on the first functional layer;
s03, forming a second functional layer on the light-emitting layer;
s04, forming a top electrode on the second functional layer;
the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light-emitting layer adopt the preparation method of the film layer. Thus, the method of fabricating the light emitting diode may have all the features and advantages of the method of fabricating the film layer described above.
According to the method for preparing the light-emitting diode provided by the embodiment of the invention, the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light-emitting layer adopt the method for preparing the film layer, so that the film quality of the first functional layer and/or the second functional layer is improved, meanwhile, the molecular orientation of the film layer is improved, the injection of carriers into the film layer is promoted, the carrier migration efficiency of the first functional layer and/or the second functional layer is improved, and the light-emitting performance of the light-emitting diode prepared by the method is further improved.
Specifically, in step S01, the first functional layer is formed on the bottom electrode.
When the first functional layer is formed on the bottom electrode, the bottom electrode constitutes a substrate for forming the first functional layer, and may be an anode or a cathode, and the material thereof may be selected from electrode materials conventional in the art. In some embodiments, the bottom electrode is an anode, and the anode material is at least one selected from ITO (indium tin oxide), FTO (fluorine doped tin oxide), IZO (zinc doped indium oxide), AZO (aluminum doped zinc oxide), ATO (aluminum doped tin oxide), GZO (gallium doped zinc oxide), MZO (magnesium doped zinc oxide), and AMO (aluminum doped magnesium oxide). The anode materials have good wettability, which is beneficial to the uniform spreading of the spin coating solution on the anode and improves the uniformity of the film layer; on the other hand, the work function of the anode material is matched with that of the first functional layer, so that the electrical characteristics of the device can be improved.
As an embodiment, the bottom electrode is an anode, and the bottom electrode is subjected to a pretreatment before the step of forming the first functional layer on the bottom electrode, the pretreatment including a chemical treatment and/or a physical treatment, preferably, the chemical treatment includes: at least one of acid treatment and alkali treatment; the physical treatment includes at least one of ultrasonic treatment, thermal treatment and ultraviolet ozone treatment. By carrying out the pretreatment on the anode, the contact angle between the spin coating solution and the electrode interface is reduced, the uniform spreading of the spin coating solution is promoted, the film forming property of the spin coating solution is improved, and the high-quality first functional layer is favorably obtained. In some embodiments, sonication with alkaline wash (pH > 10) is carried out for 15min and twice with deionized water, each for 15 min; then, isopropanol is ultrasonically cleaned for 15min, dried for 2h at 80 ℃, and subjected to ozone ultraviolet treatment for 15 min.
And forming a first functional layer on the bottom electrode by using a spin coating method, and referring to the preparation method of the film layer, wherein the formed film layer has the same or similar performance as the film layer.
In some embodiments, in the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light emitting layer, the electric field is a constant electric field to enhance the carrier mobility of the spin-on layer.
On the basis of the above embodiment, the electric field strength direction of the electric field is perpendicular to the bottom electrode. As shown in fig. 4, a is a spin-on coating layer, B constitutes a substrate of a, and when an electric field in the B → a direction is applied during spin-coating, the energy level of the a-plane at the AB interface is increased, thereby promoting hole injection into the a-layer and improving the carrier mobility of the a-layer. By reversing the direction of the electric field, as shown in fig. 5, applying an electric field in the direction B ← a during spin coating can deepen the energy level of the a-plane at the AB interface, promote electron injection, and improve the carrier mobility of the a-layer.
On the basis of the above embodiment, the electric field strength direction of the electric field is parallel to the bottom electrode. As shown in fig. 6, an electric field is applied to the side surface of the device to promote the spin coating solution to form a film on the substrate uniformly, so that the mean free path of the carriers transferred between the film molecules is reduced, the relaxation time is reduced, and the mobility of the carriers in the layer a is improved; meanwhile, the orientation of the film molecules is improved, and the scattering of photons among the film molecules can be weakened, so that the transmittance of the film is improved.
The material of the first functional layer can be selected to be polar molecules or non-polar molecules, when the material of the first functional layer is selected to be polar molecules, the responsiveness to an electric field is high, and the performance of the film layer can be effectively adjusted by adopting a constant electric field with smaller electric field intensity; when the material of the first functional layer is nonpolar molecules, the responsivity to the electric field is small, and an alternating electric field with higher electric field intensity can be adopted.
In some embodiments, one of the first functional layer and the second functional layer is a hole functional layer and the other of the first functional layer and the second functional layer is an electron functional layer.
On the basis of the above embodiment, the hole function layer includes at least one of a hole injection layer and a hole transport layer; wherein the hole injection layer is formed from a material selected from at least one of PEDOT, PSS (poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonic acid)), CuPc, F4-TCNQ (2,3,5, 6-tetrafluoro-7, 7',8,8' -tetracyanoquinodimethane), HATCN (2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazatriphenylene), MoOx, VOx, WOx, CrOx, and CuO; the material forming the hole transport layer is selected from TFB (poly [ (9, 9-di-N-octylfluorenyl-2, 7-diyl) -alt- (4,4'- (N- (4-N-butyl) phenyl) -diphenylamine) ]), PVK (polyvinylcarbazole), TPD (N, N' -bis (3-methylphenyl) -N, N '-diphenyl-1, 1' -biphenyl-4, 4 '-diamine), PFN (poly [ (9, 9-bis (3' - (N, N-dimethylamino) propyl) -2, 7-fluorene) -alt-2, 7- (9, 9-dioctylfluorene) ]), PFB [ N, N '- (4-N-butylphenyl) -N, N' -diphenyl-p-phenylenediamine ] - [9, 9-di-n-octylfluorenyl-2, 7-diyl ] copolymer, CBP (4,4' -bis (9-carbazole) biphenyl), and Poly-TPD.
On the basis of the above embodiment, the electron function layer includes at least one of an electron injection layer and an electron transport layer; wherein the material for forming the electron injection layer is selected from zinc oxide, ZnMgO, TiO2、Fe2O3、SnO2、Ta2O3At least one of AlZnO, ZnSnO and InSnO; the material for forming the electron transport layer is selected from ZnMgO and TiO2、Fe2O3、SnO2、Ta2O3At least one of AlZnO, ZnSnO and InSnO.
In a further embodiment, the first functional layer is preferably a hole functional layer, and the method for improving the hole mobility is beneficial to balancing hole-electron injection of the device, so that the luminous efficiency of the device is improved. In a specific embodiment, the hole function layer includes a hole injection layer and a hole transport layer sequentially formed on the bottom electrode. The hole transport layer is used as a transition regulation layer of the hole injection layer, and the hole transport layer and the hole injection layer are combined, so that the performance of the device is optimal.
In step S02, a light-emitting layer is formed on the first functional layer.
The specific steps for forming the light emitting layer can refer to conventional operations in the art, and the embodiment of the present invention is not limited thereto.
The material of the light-emitting layer is preferably inorganic semiconductor quantum dots, including but not limited to II-VI group quantum dots, III-V group quantum dots, II-V group quantum dots, III-VI group quantum dots, IV-VI group quantum dots, I-III-VI group quantum dots, II-IV-VI group quantum dots, IV group simple substance quantum dots and the like, and the material can be of a core structure or a core-shell structure.
In step S03, a second functional layer is formed on the light-emitting layer.
The step of forming the second functional layer may refer to a conventional operation in the art, and may also employ the same operation as step S02 described above. When the same operation as in step S02 is performed, the second functional layer is formed to have the same or similar effect as that of the first functional layer, for example, the molecular orientation and the carrier transfer efficiency are improved.
The second functional layer may be an electron functional layer or a hole functional layer, with particular reference to the device structure.
When the bottom electrode is an anode, the second functional layer is an electronic functional layer, and the specific composition and properties thereof can be referred to the conventional technology in the field. In some embodiments, the second functional layer is an electron injection layer; in some embodiments, the second functional layer is an electron transport layer; in some embodiments, the second functional layer includes an electron injection layer and an electron transport layer formed on the electron injection layer.
When the bottom electrode is a cathode, the second functional layer is a hole functional layer, and the specific composition and properties thereof can be referred to the conventional technology in the field. In some embodiments, the second functional layer is a hole injection layer; in some embodiments, the second functional layer is a hole transport layer; in some embodiments, the second functional layer includes a hole injection layer and a hole transport layer formed on the hole injection layer.
In step S04, a top electrode is formed on the second functional layer.
The specific steps for forming the top electrode can refer to the conventional operations in the art, such as forming the top electrode on the second functional layer by evaporation, chemical vapor deposition, spin coating, inkjet printing, and the like. The electrode material of the top electrode can be referred to the conventional technique in the art.
In summary, different from the conventional spin coating method, the embodiment of the invention forms the hole functional layer and/or the electron functional layer by spin coating under the action of the electric field, solves the technical problems of poor film performance, low carrier mobility and the like caused by irregular arrangement of solute molecules easily affected by brownian motion in the conventional spin coating method, realizes flexible and controllable adjustment of the carrier mobility and the interface injection barrier of the hole functional layer and/or the electron functional layer on the basis of not changing the structure and the material of the light emitting diode, balances the hole-electron injection of the device, and improves the luminous efficiency and the service life of the device.
Correspondingly, the light-emitting diode is prepared by the preparation method.
The light-emitting diode provided by the embodiment of the invention is prepared by the preparation method, and has good light-emitting performance and carrier migration efficiency.
As shown in fig. 7, the light emitting diode manufactured by the above manufacturing method includes: the organic electroluminescent device comprises a bottom electrode 1, a first functional layer 2, a luminescent layer 3, a second functional layer 4 and a top electrode 5, wherein the bottom electrode 1 and the top electrode 5 are oppositely arranged, the luminescent layer 3 is arranged between the bottom electrode 1 and the top electrode 5, the first functional layer 2 is arranged between the bottom electrode 1 and the luminescent layer 3, and the second functional layer 4 is arranged between the luminescent layer 3 and the top electrode 5.
The structure of the light emitting diode can refer to the conventional technology in the field, when the light emitting diode is in a positive structure, the anode is connected with the substrate to be used as a bottom electrode; when the light emitting diode is in an inverted structure, the cathode is connected with the substrate to be used as a bottom electrode. In addition, specific structures of the first functional layer and the second functional layer can refer to the conventional technology in the field, including but not limited to a carrier injection layer, a carrier transport layer, a carrier blocking layer and the like.
In some embodiments, the bottom electrode is an anode, the top electrode is a cathode, the first functional layer is a hole injection layer, and the second functional layer is an electron injection layer.
In some embodiments, the bottom electrode is an anode, the top electrode is a cathode, the first functional layer is a hole injection layer, and the second functional layer is an electron input layer.
In some embodiments, the bottom electrode is an anode, the top electrode is a cathode, the first functional layer is a hole injection layer, and the second functional layer is an electron injection layer;
in some embodiments, the bottom electrode is an anode, the top electrode is a cathode, the first functional layer includes a hole injection layer and a hole transport layer sequentially formed on the bottom electrode, and the second functional layer includes an electron injection layer and an electron transport layer sequentially formed on the light emitting layer.
In order that the above details of the practice and operation of the present invention will be clearly understood by those skilled in the art, and the advanced nature of the light emitting diode and the method of making the same according to the embodiments of the present invention will be apparent, the practice of the present invention will be illustrated by the following examples.
Example 1
The embodiment provides a light emitting diode, and a preparation method thereof specifically comprises the following steps:
(1) providing an ITO anode, and pretreating the anode: ultrasonic cleaning with alkaline cleaning solution (pH > 10) for 15min, ultrasonic cleaning with deionized water for 15min twice, ultrasonic cleaning with isopropanol for 15min, oven drying at 80 deg.C for 2h, and ozone ultraviolet treating for 15 min.
(2) Forming a hole injection layer on the anode: under an electric field, spin-coating a PEDOT (Poly ethylene glycol ether ketone) PSS solution on an anode, spin-coating at 5000rpm for 40s, and then carrying out annealing treatment at 150 ℃ for 15min to form a hole injection layer; wherein the electric field has an intensity direction perpendicular to the anode and facing the hole injection layer and an intensity of 10%4V/cm。
(3) Forming a hole transport layer on the hole injection layer: under an electric field, spin-coating a TFB solution (with the concentration of 8mg/mL and the solvent of chlorobenzene) on the hole injection layer, carrying out spin-coating at 3000rpm for 30s, and then carrying out annealing treatment at 80 ℃ for 30min to form a hole transport layer; wherein the electric field has an electric field strength of 10, and the electric field strength is perpendicular to the anode and toward the hole transport layer4V/cm。
(4) Forming a light emitting layer on the hole transport layer: taking a CdSe/ZnS solution (the concentration is 30mg/mL, the solvent is n-octane), and spin-coating the CdSe/ZnS solution on the hole transport layer in a glove box (the water oxygen content is less than 0.1ppm) at the rotating speed of 3000rpm to form a light-emitting layer.
(5) Forming an electron transport layer on the light emitting layer: in a glove box (the water oxygen content is less than 0.1ppm), ZnO solution (the concentration is 45mg/mL, the solvent is ethanol) is spin-coated on the luminescent layer, the coating is spin-coated at 3000rpm for 30s, and then annealing treatment is carried out at 80 ℃ for 30min, so as to form the electron transport layer.
(6) Forming a cathode on the electron transport layer: and evaporating Al on the electron transport layer by adopting an evaporation method to form an Al electrode with the thickness of 60-150 nm.
Comparative example 1
This comparative example provides a light emitting diode prepared substantially the same as in example 1, except that: in the step (2) and the step (3), no electric field is applied at the time of spin coating.
Comparative example 2
This comparative example provides a light emitting diode prepared substantially the same as in example 1, except that: in the step (2) and the step (3), an electric field is applied after the solution film layer is formed by spin coating.
And (3) performance testing:
the contact angles of the PEDOT/PSS solution on the anode in the example 1 and the comparative example 1 are respectively detected, and the detection results are shown in the table 1, which shows that the contact angle of the spin-coating solution on the anode can be reduced by applying an electric field during the spin-coating process, and the uniform film formation of the spin-coating solution on the anode can be promoted.
TABLE 1
Figure BDA0002585957230000111
2. The light emitting diodes of the embodiment 1 and the comparative examples 1 to 2 are respectively subjected to performance tests, and the test indexes and the test method are as follows:
(1) construction of Current Density-Voltage (J-V) curves
And testing by adopting an efficiency testing system which is constructed by controlling a QE PRO spectrometer, Keithley 2400 and Keithley 6485 by LabView under the environment of room temperature and air humidity of 30-60%, and measuring parameters such as voltage and current to construct a J-V curve.
(2) External Quantum Efficiency (EQE):
the ratio of the number of electrons-holes injected into the quantum dots to the number of emitted photons, the unit is%, is an important parameter for measuring the quality of the electroluminescent device, and can be obtained by measuring with an EQE optical measuring instrument. The specific calculation formula is as follows:
Figure BDA0002585957230000112
in the formula etaeFor light output coupling efficiency, ηrIs the ratio of the number of recombination carriers to the number of injection carriers, chi is the ratio of the number of excitons generating photons to the total number of excitons, KRTo the rate of the radiation process, KNRIs the non-radiative process rate.
And (3) testing conditions are as follows: the method is carried out at room temperature, and the air humidity is 30-60%.
(3) Construction of a Brightness-Voltage (L-V) Curve
The luminance (L) is the ratio of the area of the luminous flux of the light-emitting surface in a given direction to the luminous flux perpendicular to the given direction (cd/m)2). And controlling the calibrated linear silicon light pipe system PDB-C613 by adopting LabView to measure, calculating the brightness of the device by combining a spectrum and a visual function, and constructing an L-V curve according to the change of the brightness along with the voltage.
FIG. 8 is a J-V curve of the light emitting diodes of example 1 and comparative examples 1-2, showing that the current density of the light emitting diode of example 1 is higher than that of the light emitting diodes of comparative examples 1-2 at each driving voltage, illustrating that the light emitting diode prepared by the method of the present invention can effectively improve the hole mobility of the device, balance hole-electron injection, and improve the light emitting efficiency of the device; FIG. 9 is an external quantum efficiency test result of the light emitting diodes of example 1 and comparative examples 1 to 2, showing that example 1 has higher external quantum efficiency than the light emitting diodes of comparative examples 1 to 2; FIG. 10 is an L-V curve of the light emitting diodes of example 1 and comparative examples 1-2, showing that the light emitting diode of example 1 has a lower turn-on voltage than the light emitting diodes of comparative examples 1-2, which shows that the energy barrier of example 1 is lower, the brightness is higher at the same voltage, and the comprehensive performance of the device is better.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (11)

1. A method of preparing a film, comprising: a spin-coating solution is spin-coated on a substrate, and an electric field is applied to the substrate during the spin-coating process.
2. The method of claim 1, wherein the electric field has a strength of 103~107V/cm; and/or
The frequency of the electric field is 1 Hz-10 GHz.
3. The production method according to claim 1, wherein the electric field is a constant electric field or an alternating electric field; and/or
The electric field intensity direction of the electric field is vertical or parallel to the substrate.
4. The production method according to any one of claims 1 to 3, wherein the solute of the spin-coating solution is a polar molecule, and the electric field is a constant electric field; or
The solute of the spin-coating solution is nonpolar molecules, and the electric field is an alternating electric field.
5. A preparation method of a light-emitting diode is characterized by comprising the following steps:
forming a first functional layer on the bottom electrode;
forming a light emitting layer on the first functional layer;
forming a second functional layer on the light emitting layer;
forming a top electrode on the second functional layer;
wherein the step of forming a first functional layer on the bottom electrode and/or the step of forming a second functional layer on the light-emitting layer employs the production method according to any one of claims 1 to 4.
6. The production method according to claim 5, wherein in the step of forming the first functional layer on the bottom electrode and/or the step of forming the second functional layer on the light-emitting layer, the electric field is a constant electric field.
7. The production method according to claim 5, wherein one of the first functional layer and the second functional layer is a hole functional layer, and the other of the first functional layer and the second functional layer is an electron functional layer.
8. The production method according to claim 7, wherein the hole function layer includes at least one of a hole injection layer and a hole transport layer;
wherein the material forming the hole injection layer is selected from at least one of PEDOT, PSS, CuPc, F4-TCNQ, HATCN, MoOx, VOx, WOx, CrOx and CuO;
the material forming the hole transport layer is selected from at least one of TFB, PVK, Poly-TPD, PFN, PFB, CBP and TPD.
9. The production method according to claim 7, wherein the electron function layer includes at least one of an electron injection layer and an electron transport layer;
wherein the material forming the electron injection layer is selected from zinc oxide, ZnMgO, TiO2、Fe2O3、SnO2、Ta2O3At least one of AlZnO, ZnSnO and InSnO;
the material for forming the electron transport layer is selected from ZnMgO and TiO2、Fe2O3、SnO2、Ta2O3At least one of AlZnO, ZnSnO and InSnO.
10. The method according to claim 5, wherein the bottom electrode is an anode, and the step of forming the first functional layer on the bottom electrode is preceded by a pretreatment comprising a chemical treatment and/or a physical treatment;
wherein the chemical treatment comprises: at least one of acid treatment and alkali treatment;
the physical treatment includes at least one of ultrasonic treatment, thermal treatment and ultraviolet ozone treatment.
11. A light-emitting diode produced by the production method according to any one of claims 5 to 10.
CN202010681387.7A 2020-07-15 2020-07-15 Preparation method of film layer, light-emitting diode and preparation method of light-emitting diode Pending CN113948665A (en)

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