CN113725374B - OLED device with inverted structure and preparation method - Google Patents
OLED device with inverted structure and preparation method Download PDFInfo
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- CN113725374B CN113725374B CN202110801218.7A CN202110801218A CN113725374B CN 113725374 B CN113725374 B CN 113725374B CN 202110801218 A CN202110801218 A CN 202110801218A CN 113725374 B CN113725374 B CN 113725374B
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- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000002347 injection Methods 0.000 claims abstract description 68
- 239000007924 injection Substances 0.000 claims abstract description 68
- 239000000243 solution Substances 0.000 claims abstract description 62
- DHDHJYNTEFLIHY-UHFFFAOYSA-N 4,7-diphenyl-1,10-phenanthroline Chemical compound C1=CC=CC=C1C1=CC=NC2=C1C=CC1=C(C=3C=CC=CC=3)C=CN=C21 DHDHJYNTEFLIHY-UHFFFAOYSA-N 0.000 claims abstract description 34
- ZDRUQYXMEVVOJU-UHFFFAOYSA-L C(=O)O.C([O-])([O-])=O.[Li+].[Li+] Chemical compound C(=O)O.C([O-])([O-])=O.[Li+].[Li+] ZDRUQYXMEVVOJU-UHFFFAOYSA-L 0.000 claims abstract description 30
- MPAGKJUBXYEFNL-UHFFFAOYSA-L [Li+].[Li+].OB(O)O.[O-]C([O-])=O Chemical compound [Li+].[Li+].OB(O)O.[O-]C([O-])=O MPAGKJUBXYEFNL-UHFFFAOYSA-L 0.000 claims abstract description 23
- 230000005525 hole transport Effects 0.000 claims abstract description 21
- 238000000137 annealing Methods 0.000 claims abstract description 12
- 238000000151 deposition Methods 0.000 claims abstract description 9
- 239000011248 coating agent Substances 0.000 claims abstract description 8
- 238000000576 coating method Methods 0.000 claims abstract description 8
- 238000002207 thermal evaporation Methods 0.000 claims abstract description 5
- 238000004140 cleaning Methods 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 239000011521 glass Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 13
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 239000008367 deionised water Substances 0.000 claims description 9
- 229910021641 deionized water Inorganic materials 0.000 claims description 9
- 239000012153 distilled water Substances 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 9
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 8
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 6
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 6
- 238000004528 spin coating Methods 0.000 claims description 5
- NWZSZGALRFJKBT-KNIFDHDWSA-N (2s)-2,6-diaminohexanoic acid;(2s)-2-hydroxybutanedioic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O.NCCCC[C@H](N)C(O)=O NWZSZGALRFJKBT-KNIFDHDWSA-N 0.000 claims description 4
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 4
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 4
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 4
- 239000004327 boric acid Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 235000019253 formic acid Nutrition 0.000 claims description 4
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 238000004506 ultrasonic cleaning Methods 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 abstract description 3
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 abstract 2
- 239000010408 film Substances 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 4
- 238000005401 electroluminescence Methods 0.000 description 4
- 238000001194 electroluminescence spectrum Methods 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229920000144 PEDOT:PSS Polymers 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 238000000089 atomic force micrograph Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000031700 light absorption Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000001566 impedance spectroscopy Methods 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/17—Carrier injection layers
- H10K50/171—Electron injection layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K2102/00—Constructional details relating to the organic devices covered by this subclass
- H10K2102/301—Details of OLEDs
- H10K2102/321—Inverted OLED, i.e. having cathode between substrate and anode
Abstract
The invention relates to the field of semiconductor devices, and discloses an inverted structure OLED device and a preparation method thereof, wherein the preparation method comprises the steps of preparing lithium carbonate-formic acid solution; preparing a lithium carbonate-boric acid solution; treating an ITO transparent cathode; and coating one of lithium carbonate-formic acid solution and lithium carbonate-boric acid solution on the ITO transparent cathode, annealing to obtain an electron injection layer, and sequentially depositing a BPhen electron transport layer, a PBD luminescent layer, a CBP hole transport layer, a MoO3 hole injection layer and an Al anode on the multi-source thermal evaporation system to obtain the OLED device with the inverted structure. The lithium carbonate-formic acid layer as an electron injection layer, based on the PBD light emitting layer, the OLED device exhibits excellent photovoltaic device performance with a maximum irradiance of 5.24mW/cm2 and an EQE of 2.47%, and the lithium carbonate-formic acid layer exhibits excellent electron performance and facilitates electron injection, thereby improving the electro-optic performance of the inverted structure OLED device.
Description
Technical Field
The invention relates to the field of semiconductor devices, in particular to an inverted structure OLED device and a preparation method thereof.
Background
Organic electroluminescent devices having an inverted structure (inverted OLED devices) are receiving attention due to great advantages in terms of operation durability and integration with n-type thin film transistors. Ultraviolet or near ultraviolet OLEDs are also widely used in high density information storage, sensor analysis, biomedical and forensic applications. Ultraviolet or near ultraviolet OLED with high photoelectric efficiency is mainly concentrated in a normal structure, because a higher electron injection barrier exists between a transparent Indium Tin Oxide (ITO) cathode and an Electron Transport Layer (ETL) in the inverted structure OLED, so that unbalance of electron-hole in a light emitting layer is caused, and the performance of an ultraviolet OLED device is restrained from being improved.
At present, the main method for solving the problems is to introduce an electron injection layer between ITO and ETL, and the acquisition of the existing strong electron injection layer is mostlyIs prepared from active alkali metal Ca, ba, cs, li, al, mg and inorganic compound LiF, csF, cs 2 CO 3 And MoS 2 The process has the advantages of more energy consumption, higher cost and narrower manufacturing requirement surface.
Disclosure of Invention
The invention aims to provide an inverted structure OLED device and a preparation method thereof, which aim to improve the electro-optical performance of the inverted structure OLED device and facilitate the manufacture.
In order to achieve the above object, the present invention provides an inverted OLED device and a method for manufacturing the same, comprising an ITO transparent cathode, a strong electron injection layer connected to the ITO transparent cathode, a BPhen electron transport layer connected to the strong electron injection layer, a PBD light emitting layer connected to the BPhen electron transport layer, a CBP hole transport layer connected to the PBD light emitting layer, and a MoO connected to the CBP hole transport layer 3 A hole injection layer, and the MoO 3 And an Al anode connected with the hole injection layer.
In a second aspect, the present invention provides a method for fabricating an inverted structure OLED device, comprising:
preparing a lithium carbonate-formic acid solution;
preparing a lithium carbonate-boric acid solution;
treating an ITO transparent cathode;
coating one of lithium carbonate-formic acid solution and lithium carbonate-boric acid solution on the ITO transparent cathode, annealing to obtain an electron injection layer, and sequentially depositing a BPhen electron transport layer, a PBD luminescent layer, a CBP hole transport layer and MoO 3 And the hole injection layer and the Al anode are used for obtaining the OLED device with the inverted structure.
Wherein, the specific steps for preparing the lithium carbonate-formic acid solution are as follows:
200mg of lithium carbonate is dissolved in 1ml of formic acid, 1.25ml of hydrazine hydrate is added, and the solution is stirred until the solution is transparent;
naturally cooling the solution to room temperature;
adding deionized water to prepare the lithium carbonate-formic acid solution with the concentration of 1-7 mg/ml.
The specific mode for preparing the lithium carbonate-boric acid solution is as follows: 200mg of lithium carbonate was dissolved in 11.5ml of boric acid solution (0.05 g/ml), and deionized water was added to prepare a lithium carbonate-boric acid solution having a concentration of 3-10 mg/ml.
The specific steps of the ITO transparent cathode treatment are as follows:
placing the ITO coated glass sheet into an ultrasonic cleaner added with distilled water and ITO glass cleaning liquid for repeated cleaning twice;
replacing distilled water and ITO glass cleaning liquid in the ultrasonic cleaner with acetone, and repeating the cleaning twice;
replacing acetone in the ultrasonic cleaning instrument with isopropanol, and repeating the cleaning twice;
and (3) placing the ITO coated glass sheet into an ultraviolet ozone cleaning machine to radiate for 10-20min to obtain the ITO transparent cathode.
Wherein, the cleaning time of each cleaning process in the preparation of the ITO transparent cathode is 10-20min, and the ultrasonic frequency is 40KHz.
Wherein the weight part ratio of the distilled water to the ITO glass cleaning liquid is 100:1-3.
Wherein, coating one of lithium carbonate-formic acid solution and lithium carbonate-boric acid solution on the ITO transparent cathode, annealing to obtain an electron injection layer, and finally depositing the BPhen electron transport layer, the PBD luminescent layer, the CBP hole transport layer and the MoO in sequence 3 The preparation method of the OLED device with the inverted structure comprises the following specific steps of:
spin coating one of the lithium carbonate-formic acid solution and the lithium carbonate-boric acid solution on the ITO transparent cathode at a speed of 3000 rpm for 50-70s;
annealing is carried out on annealing tables at 220-240 ℃ and 310-330 ℃ for 15-30min respectively, and the electron injection layer is prepared;
at a vacuum degree of 10 -4 Sequentially depositing the BPhen electron transport layer, the PBD luminescent layer, the CBP hole transport layer and the MoO in a multi-source thermal deposition vacuum chamber of pa 3 A hole injection layer and an Al anode.
Wherein the thickness of the BPhen electron transport layer is 15-35nm; the thickness of the PBD luminescent layer is 25-45nm; by a means ofThe thickness of the CBP hole transport layer is 60-80nm; the MoO 3 The thickness of the hole injection layer is 1-6nm; the thickness of the Al anode is 100-200nm.
According to the OLED device with the inverted structure and the preparation method, all materials are commercially supplied, and further purification treatment is not needed. The invention selects lithium carbonate-formic acid as a single electron injection layer, and based on a PBD luminescent layer, the OLED device shows excellent photoelectric device performance with 5.24mW/cm 2 Analysis shows that the lithium carbonate-formic acid layer exhibits excellent electron properties and facilitates electron injection, thereby improving the electro-optical properties of the inverted structure OLED device.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of an inverted structure OLED device of the present invention;
FIG. 2 is a flow chart of a method of fabricating an inverted structure OLED device of the present invention;
FIG. 3 is a flow chart of the preparation of a lithium carbonate-formic acid solution of the present invention;
FIG. 4 is a flow chart of the present invention for processing an ITO transparent cathode;
FIG. 5 shows an ITO transparent cathode coated with one of a lithium carbonate-formic acid solution and a lithium carbonate-boric acid solution, annealed to obtain an electron injection layer, and finally sequentially deposited with a BPhen electron transport layer, a PBD light-emitting layer, a CBP hole transport layer, and MoO 3 The hole injection layer and the Al anode are used for obtaining a flow chart of the OLED device with the inverted structure;
FIG. 6 is an AFM image of 1.5 μm by 1.5 μm;
FIG. 7 is a J-V, R-V, EQE and EL spectra of an inverted near ultraviolet OLED having lithium carbonate-formic acid solutions as electron injection layers at concentrations of 1, 3, 5 and 7mg/ml, respectively;
FIG. 8 is a J-V, R-V, EQE and EL spectra of an inverted near ultraviolet OLED having lithium carbonate-boric acid solutions as electron injection layers at concentrations of 3, 5, 7 and 10mg/ml, respectively;
FIG. 9 is an ultraviolet-visible light absorption spectrum of a quartz plate, a film of lithium carbonate-formic acid (3 mg/ml) or lithium carbonate-boric acid (7 mg/ml) coated on the quartz plate;
FIG. 10 shows (a) I-V, (b) Z-V and (c) of a single-electron device having different concentrations of lithium carbonate-formic acid solution (1, 3 and 5 mg/ml) and lithium carbonate-boric acid solution (3, 5 and 7 mg/ml) as electron injection layersA characteristic relationship diagram;
1-ITO transparent cathode, 2-strong electron injection layer, 3-BPhen electron transport layer, 4-PBD luminescent layer, 5-CBP hole transport layer, 6-MoO 3 Hole injection layer, 7-Al anode.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In a first aspect, referring to fig. 1, the present invention provides an inverted structure OLED device:
comprises an ITO transparent cathode 1, a strong electron injection layer 2 connected with the ITO transparent cathode 1, a BPhen electron transport layer 3 connected with the strong electron injection layer 2, a PBD luminescent layer 4 connected with the BPhen electron transport layer 3, a CBP hole transport layer 5 connected with the PBD luminescent layer 4, and MoO connected with the CBP hole transport layer 5 3 A hole injection layer 6, and the MoO 3 An Al anode 7 to which the hole injection layer 6 is connected.
In this embodiment, all materials are commercially available without further purification treatment. The invention selects lithium carbonate-formic acid as single electron injectionThe layer, based on the PBD light-emitting layer 4, the inverted structure OLED device shows excellent photoelectric device performance, and has a weight of 5.24mW/cm 2 Analysis shows that the lithium carbonate-formic acid layer exhibits excellent electron properties and facilitates electron injection, thereby improving the electro-optical properties of the inverted structure OLED device.
In a second aspect, referring to fig. 2 to 10, the present invention further provides a method for preparing an OLED device with an inverted structure, including:
s101, preparing a lithium carbonate-formic acid solution;
the method comprises the following specific steps:
s201, 200mg of lithium carbonate is dissolved in 1ml of formic acid, 1.25ml of hydrazine hydrate is added, and the solution is stirred until the solution is transparent;
s202, naturally cooling the solution to room temperature;
s203, adding deionized water to prepare a lithium carbonate-formic acid solution with the concentration of 1-7 mg/ml.
S102, preparing a lithium carbonate-boric acid solution;
in a specific mode, 200mg of lithium carbonate is dissolved in 11.5ml of boric acid solution (0.05 g/ml), deionized water is added, and the lithium carbonate-boric acid solution with the concentration of 3-10mg/ml is prepared.
The preparation of the lithium carbonate-formic acid solution (abbreviated FA) and the lithium carbonate-boric acid solution (abbreviated BA) is shown in fig. 3. 200mg of Li was added to a beaker 2 CO 3 Powder and 1ml of formic acid, stirred to Li 2 CO 3 Completely dissolved. Then adding 1.25ml of hydrazine hydrate into the solution, stirring until the solution is clear, cooling to room temperature, and adding a certain amount of deionized water to prepare the FA with the concentration of 1-7 mg/ml. Likewise, 200mg of Li 2 CO 3 The powder was dissolved in 11.5ml boric acid and deionized water was added to give a concentration of 3-10mg/ml BA.
S103, processing an ITO transparent cathode;
the method comprises the following specific steps:
s301, placing the ITO coated glass sheet into an ultrasonic cleaner added with distilled water and ITO glass cleaning liquid for repeated cleaning twice;
s302, replacing distilled water and ITO glass cleaning liquid in the ultrasonic cleaner with acetone, and repeating the cleaning twice;
s303, replacing acetone in the ultrasonic cleaning instrument with isopropanol, and repeating cleaning twice;
s304, placing the ITO coated glass sheet into an ultraviolet ozone cleaning machine to radiate for 10-20min to obtain the ITO transparent cathode.
The cleaning time of each cleaning process in the preparation of the ITO transparent cathode is 10-20min, and the ultrasonic frequency is 40KHz. The weight part ratio of the distilled water to the ITO glass cleaning liquid is 100:1-3.
All inverted near ultraviolet OLEDs were assembled on commercial ITO glass substrates, which were treated sequentially with chemical solvents, deionized water, and uv ozone for 15 minutes for use.
S104, coating one of lithium carbonate-formic acid solution and lithium carbonate-boric acid solution on the ITO transparent cathode 1, annealing to obtain an electron injection layer, and finally sequentially depositing a BPhen electron transport layer 3, a PBD luminescent layer 4, a CBP hole transport layer 5 and MoO 3 The hole injection layer 6 and the Al anode 7 result in an inverted structure OLED device.
The method comprises the following specific steps:
s401, spin-coating one of the lithium carbonate-formic acid solution and the lithium carbonate-boric acid solution on the ITO transparent cathode 1 at a speed of 3000 revolutions per minute for 50-70S;
s402, annealing is carried out on annealing tables at 220-240 ℃ and 310-330 ℃ for 15-30min respectively, and the electron injection layer is prepared;
s403 at vacuum degree of 10 -4 Sequentially depositing the BPhen electron transport layer 3, the PBD luminescent layer 4, the CBP hole transport layer 5 and the MoO in a multi-source thermal deposition vacuum chamber of pa 3 A hole injection layer 6 and an Al anode 7.
The thickness of the BPhen electron transport layer 3 is 15-35nm; the thickness of the PBD luminescent layer 4 is 25-45nm; the thickness of the CBP hole transport layer 5 is 60-80nm; the MoO 3 The thickness of the hole injection layer 6 is 1-6nm; the thickness of the Al anode 7 is 100-200nm.
The electron injection layer is prepared by spin-coating FA or BA onto ITO substrate at 3000 rpm for spin-coating time60s, and then annealed in an environment of 220 ℃ (FA) or 320 ℃ (BA) for 20 minutes. The ITO substrate coated with the electron injection layer was then immediately transferred to a multi-source thermal evaporation system. Then at 10 -4 BPhen (25 nm) was deposited under Pa as Electron Transport Layer (ETL), PBD (35 nm) as near ultraviolet light emitting layer (EML), CBP (70 nm) as Hole Transport Layer (HTL), moO, respectively 3 (5 nm) as Hole Injection Layer (HIL) and Al (100 nm) as reflective anode. Finally, 25mm of the product is prepared 2 Inverted near ultraviolet OLEDs of effective light emitting area. The basic flow of preparing an inverted near ultraviolet OLED is shown in fig. 2. A series of inverted near ultraviolet OLEDs with different electron injection layers were constructed.
Devices A1 ITO/FA (1 mg/ml)/BPhen (25 nm)/PBD (35 nm)/CBP (70 nm)/MoO 3 (5nm)/Al(100nm).
Device A2 ITO/FA (3 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
Device A3 ITO/FA (5 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
Device A4 ITO/FA (7 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
Device B1 ITO/BA (3 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
Device B2 ITO/BA (5 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
Device B3 ITO/BA (7 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
Device B4 ITO/BA (10 mg/ml)/BPhen/PBD/CBP/MoO 3 /Al.
The ultraviolet-visible absorption spectrum of the film was measured using an ultraviolet-visible spectrophotometer. The surface morphology of the spin-coated film was investigated by measuring with an Atomic Force Microscope (AFM). The current density-voltage-irradiance (J-V-R) characteristic and Electroluminescence (EL) spectrum of the inverted near-uv OLED are provided by a chrono-digital source meter, a spectrum scanner, and data acquisition software. Impedance-voltage (Z-V) and phase-voltageThe curves were obtained from impedance analyzer to single electron device (EOC) tests. All J-V-R, Z-V and +.>The measurements were all performed at room temperature without encapsulation.
Performance of near ultraviolet OLED and coating Li 2 CO 3 The surface morphology of the film is closely related. As shown in FIG. 6a, AFM images of ITO showed a Root Mean Square (RMS) roughness of 0.64nm. After coating the ITO surface with a layer of FA or BA, the corresponding RMS value was reduced to 0.55nm or 0.54nm, respectively (FIGS. 6b-6 c). The spin-coated film effectively fills some crystal boundaries and pinholes on the ITO surface, and improves the appearance and quality of the film.
The J-V-R characteristic curves of inverted near ultraviolet OLED with different concentrations of FA or BA as electron injection layers are shown in FIGS. 7-8. Table 1 summarizes some key parameters. First, the effect of FA concentration on near-uv OLED performance. As shown in FIG. 7, when FA having an optimal concentration of 3mg/ml is used as the electron injection layer, the EQE of the device (device A2) reaches the highest level of 2.47% @1.58mA/cm 2 Maximum irradiance reaches 5.24mW/cm 2 At 9.3V, the EL peak is 406nm and the maximum half-width is 52nm. And device A1 (1.51% @1.48 mA/cm) 2 1 mg/ml), device A3 (1.86% @4.49mA/cm 2 5 mg/ml) and device A4 (1.73% @7.06mA/cm 2 7 mg/ml) the EQE of device A2 with FA as the electron injection layer at a concentration of 3mg/ml was increased by 63.6%, 32.8% and 42.8%, respectively.
Also, as shown in FIG. 8, the J-V-R characteristic of the inverted near ultraviolet OLED (device B3) with 7mg/ml BA as the electron injection layer exhibited the best performance. The maximum irradiance of the device was 2.28mW/cm 2 @9.5V, maximum EQE of 2.17% @0.73mA/cm 2 The EL peak was 404nm and the half-width was 55nm. And device B1 (EQE is 1.35% @12.83mA/cm 2 3 mg/ml), device B2 (EQE 1.53% @5.91mA/cm 2 5 mg/ml) and device B4 (EQE 1.36% @1.18mA/cm 2 10 mg/ml) the EQE of device B3 was increased by 60.7%, 41.8% and 59.6%, respectively. The solution concentration is optimized to provide a simple and feasible method for adjusting the device performance and can be finely controlled. The two solution-treated lithium carbonates are used as electron injection layers, the devices with the optimal performance are respectively device A2 and device B3, and the maximum EQE and the maximum spoke of device A2Illuminance (2.47% and 5.24 mW/cm) 2 ) Slightly better than device B3 (2.17% and 2.28 mW/cm) 2 ) This is probably due to the greater electron injection capability of FA. Li, on the other hand 2 CO 3 The photoelectric performance of the inverted near ultraviolet OLED as an electron injection layer is equivalent to or even better than that of a traditional structural device with PBD as a light-emitting layer and ITO as a transparent anode. For example, with PEDOT: PSS+WO x And PEDOT: PSS+WS 2 The maximum EQE of the near-UV OLED of conventional structure as hole injection layer was 2.3% and 2.1%, respectively, and the maximum radiation was 3.98mW/cm, respectively 2 And 4.7mW/cm 2 . This indicates Li 2 CO 3 The superiority in the aspect of electron injection improves the photoelectric performance of the ultraviolet OLED.
TABLE 1 summary of performance of inverted near ultraviolet OLEDs with different concentrations of FA and BA as electron injection layers
As shown in fig. 7d and 8d, the inverted near-uv OLED with FA or BA as the electron injection layer exhibited similar EL spectra with emission peaks of 404-406nm, resulting from near-uv emission of PBD molecules.
As shown in fig. 9, FA or BA is used as the electron injection layer, and the light absorption in the near ultraviolet band is very small, which is also beneficial to obtain a high-performance near ultraviolet OLED device.
The electron injection capabilities of FA and BA were further investigated by testing single electron device current-voltage (I-V) and impedance spectroscopy. The construction of a series of single electron devices is as follows.
Device C1 ITO/FA (1 mg/ml)/BPhen/Liq/Al.
Device C2 ITO/FA (3 mg/ml)/BPhen/Liq/Al.
Device C3 ITO/FA (5 mg/ml)/BPhen/Liq/Al.
Device D1 ITO/BA (3 mg/ml)/BPhen/Liq/Al.
Device D2 ITO/BA (5 mg/ml)/BPhen/Liq/Al.
Device D3 ITO/BA (7 mg/ml)/BPhen/Liq/Al.
As shown in FIG. 10a, device C2 #FA of 3mg/ml as electron injection layer) shows the highest current at the same voltage. This indicates that the electron injection capability of the device C2 is the strongest. Z-V andas shown in fig. 10b and 10c, all single electron devices exhibit about 10 at low voltages 5 Omega, the phase angle is about-90 deg.. This indicates that these single electron devices are in an insulating state at this time. The impedance decreases rapidly as the voltage increases to a certain value (transition voltage). At the same time, the corresponding phase angle is close to 0 °. This means that the single electron device is in a semiconductor state at high voltage. The lowest transition voltage for device C2 represents the strongest electron injection, followed by device C3 (5 mg/ml of FA), device D3 (7 mg/ml of BA), device C1 (1 mg/ml of FA), device D2 (5 mg/ml of BA) and device D1 (3 mg/ml of BA). For Z-V and->The analysis result of the electron injection capability of the curve is consistent with the test result of the I-V. In the whole, the electron injection can be finely regulated and controlled by changing the concentrations of FA and BA, so that the aim of improving the performance of the inverted near ultraviolet OLED is fulfilled.
The above disclosure is only a preferred embodiment of the present invention, and it should be understood that the scope of the invention is not limited thereto, and those skilled in the art will appreciate that all or part of the procedures described above can be performed according to the equivalent changes of the claims, and still fall within the scope of the present invention.
Claims (8)
1. A preparation method of an OLED device with an inverted structure is characterized in that,
comprising the following steps: preparing a lithium carbonate-formic acid solution;
preparing a lithium carbonate-boric acid solution;
treating an ITO transparent cathode;
coating one of lithium carbonate-formic acid solution and lithium carbonate-boric acid solution on the ITO transparent cathode, annealing to obtain an electron injection layer, and finally sequentially depositing BPhen electron transferTransport layer, PBD light-emitting layer, CBP hole transport layer, moO 3 The hole injection layer and the Al anode are used for obtaining an OLED device with an inverted structure;
the inverted structure OLED device comprises an ITO transparent cathode, a strong electron injection layer connected with the ITO transparent cathode, a BPhen electron transport layer connected with the strong electron injection layer, a PBD luminescent layer connected with the BPhen electron transport layer, a CBP hole transport layer connected with the PBD luminescent layer, and MoO connected with the CBP hole transport layer 3 A hole injection layer, and the MoO 3 And an Al anode connected with the hole injection layer.
2. The method of fabricating an inverted OLED device of claim 1,
the specific steps for preparing the lithium carbonate-formic acid solution are as follows:
200mg of lithium carbonate is dissolved in 1ml of formic acid, 1.25ml of hydrazine hydrate is added, and the solution is stirred until the solution is transparent;
naturally cooling the solution to room temperature;
adding deionized water to prepare the lithium carbonate-formic acid solution with the concentration of 1-7 mg/ml.
3. The method of fabricating an inverted OLED device of claim 1,
the specific mode for preparing the lithium carbonate-boric acid solution is as follows: 200mg of lithium carbonate was dissolved in 11.5ml of boric acid solution (0.05 g/ml), and deionized water was added to prepare a lithium carbonate-boric acid solution having a concentration of 3-10 mg/ml.
4. The method of fabricating an inverted OLED device of claim 1,
the specific steps of the ITO transparent cathode treatment are as follows:
placing the ITO coated glass sheet into an ultrasonic cleaner added with distilled water and ITO glass cleaning liquid for repeated cleaning twice;
replacing distilled water and ITO glass cleaning liquid in the ultrasonic cleaner with acetone, and repeating the cleaning twice;
replacing acetone in the ultrasonic cleaning instrument with isopropanol, and repeating the cleaning twice;
and (3) placing the ITO coated glass sheet into an ultraviolet ozone cleaning machine to radiate for 10-20min to obtain the ITO transparent cathode.
5. The method of fabricating an inverted OLED device of claim 4,
the cleaning time of each cleaning process in the preparation of the ITO transparent cathode is 10-20min, and the ultrasonic frequency is 40KHz.
6. The method of fabricating an inverted OLED device of claim 4,
the weight part ratio of the distilled water to the ITO glass cleaning liquid is 100:1-3.
7. The method of fabricating an inverted OLED device of claim 1,
coating one of lithium carbonate-formic acid solution and lithium carbonate-boric acid solution on the ITO transparent cathode, annealing to obtain an electron injection layer, and finally sequentially depositing the BPhen electron transport layer, the PBD luminescent layer, the CBP hole transport layer and the MoO 3 The preparation method of the OLED device with the inverted structure comprises the following specific steps of:
spin coating one of the lithium carbonate-formic acid solution and the lithium carbonate-boric acid solution on the ITO transparent cathode at a speed of 3000 rpm for 50-70s;
annealing is carried out on annealing tables at 220-240 ℃ and 310-330 ℃ for 15-30min respectively, and the electron injection layer is prepared;
at a vacuum degree of 10 -4 Sequentially depositing the BPhen electron transport layer, the PBD luminescent layer, the CBP hole transport layer and the MoO in a multi-source thermal deposition vacuum chamber of pa 3 A hole injection layer and an Al anode.
8. The method of manufacturing an inverted structure OLED device of claim 7,
the thickness of the BPhen electron transport layer is 15-35nm; the thickness of the PBD luminescent layer is 25-45nm; the thickness of the CBP hole transport layer is 60-80nm; the MoO 3 The thickness of the hole injection layer is 1-6nm; the thickness of the Al anode is 100-200nm.
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