CN110544748A - Method for improving efficiency of thermal delay fluorescence OLED device - Google Patents
Method for improving efficiency of thermal delay fluorescence OLED device Download PDFInfo
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- H10K50/00—Organic light-emitting devices
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- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
- H10K50/12—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
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- H10K50/12—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
- H10K50/121—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants for assisting energy transfer, e.g. sensitization
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Abstract
The invention discloses a method for improving the efficiency of a thermal delay fluorescence OLED device, wherein the thermal delay fluorescence OLED device comprises a carrier modulation layer and a light-emitting layer, the light-emitting layer is composed of a main body light-emitting material and an object doping material, and the method is characterized in that: adding a carrier modulation layer CBP, and adding an auxiliary doping material TPBi into the light-emitting layer. The invention adds a carrier modulation layer CBP and adds TPBi as an auxiliary doping material into the light-emitting layer of the thermal delay fluorescence OLED device, thereby improving the exciton utilization rate of the light-emitting layer and improving the efficiency of the device, and the efficiency of the prepared thermal delay fluorescence OLED device is greatly improved by taking CBP as a main light-emitting material and 4CzIPN as a thermal delay fluorescence object doping material.
Description
Technical Field
the invention mainly relates to a method for improving the efficiency of a thermal delay fluorescent OLED device, wherein an auxiliary doping material is used in the thermal delay fluorescent OLED device, and a new thought can be provided for preparing the thermal delay fluorescent OLED device with simple structure and higher efficiency.
Background
In an OLED device, the efficiency, i.e., the exciton utilization rate of the light-emitting material, is reduced, and the factors are mainly reflected in the light-emitting orientation of the material, the exciton utilization rate, and the like. The exciton utilization rate is that only 25% of singlet excitons of the traditional fluorescent material can be utilized; TADF materials can achieve 100% internal quantum efficiency, and on the other hand, exciton utilization of OLED devices is also affected by the balance of holes and electrons in the light emitting layer, so carrier imbalance also reduces the efficiency of OLED devices.
Disclosure of Invention
The invention aims to make up the defects of the prior art and provides a method for improving the efficiency of a thermal retardation fluorescence OLED device.
The invention is realized by the following technical scheme:
A method for improving the efficiency of a thermal retardation fluorescence OLED device comprises a carrier modulation layer and a light emitting layer, wherein the light emitting layer comprises a host light emitting material, a guest doping material and an auxiliary doping material, the carrier modulation layer is 4, 4-Bis (9-carbazole) biphenyl (4, 4'-Bis (N-carbazolyl) -1,1' -biphenol, CBP), and the auxiliary doping material is 1,3, 5-tris (1-phenyl-1H-benzimidazole-2-yl) benzene (1, 3,5-Tri (1-phenyl-1H-benzozo [ d ] imidiazol-2-yl) phenyl, TPBi).
The host luminescent material is 4, 4-Bis (9-carbazole) biphenyl (4, 4'-Bis (N-carbazolyl) -1,1' -biphenyl, CBP), and the guest doping material is a thermal retardation fluorescent material 4 CzIPN.
The thickness of the carrier modulation layer is 0nm or 10nm, the thickness of the luminescent layer formed by the host luminescent material, the guest doping material and the auxiliary doping material is 30nm in total, wherein the concentration of the guest doping material is 8wt% and is kept unchanged, and the concentration of the auxiliary doping material is 0wt% to 50 wt%.
The carrier modulation layer CBP is 10nm, and the concentration of the auxiliary doping material is 50 wt%.
The 4, 4-Bis (9-carbazole) biphenyl (4, 4'-Bis (N-carbazolyl) -1,1' -biphenyl, CBP) is evaporated on an ITO glass substrate of the thermal delay fluorescent OLED device to form a carrier modulation layer; and the host luminescent material, the guest doping material and the auxiliary doping material are jointly evaporated on the ITO glass substrate of the thermal delay fluorescent OLED device to form a luminescent layer.
To fabricate a high efficiency thermal retarded fluorescent OLED device, we fabricated device A, B for testing efficiency, where B is the control. The preparation method of the devices A and B comprises the following steps:
for device A (ITO/TAPC (30nm)/CBP (10nm)/CBP: TPBi:4CzIPN,
50wt%:8wt%(30nm)/TPBi(40nm)/LiF(1nm)/Al(100nm))，
The operation steps are as follows:
(1) And cleaning the ITO glass substrate.
(2) And drying the cleaned ITO glass substrate by using a heating table after drying to remove water.
(3) And carrying out ultraviolet ozone treatment on the ITO glass substrate.
(4) And placing the ITO glass sheet subjected to ultraviolet ozone treatment on a substrate frame, then placing the substrate frame into a coating machine, and vacuumizing the coating machine.
(5) Sequentially plating TAPC, a carrier modulation layer, a light-emitting layer, TPBi, LiF and Al on the glass substrate, wherein the thickness of the carrier modulation layer CBP is 10nm, the thickness of the light-emitting layer is 30nm, and the proportion of TPBi to the thermal retardation fluorescent material 4CzIPN is respectively 50wt% and 8 wt%. And then opening the coating machine after the coating machine is naturally cooled for half an hour, and taking out the prepared OLED device.
(6) And packaging the OLED device.
(7) and carrying out a light emitting test on the OLED device.
Device B (ITO/TAPC (30nm)/CBP:4CzIPN,
8wt% (30nm)/TPBi (40nm)/LiF (1nm)/Al (100nm)), that is, no carrier modulation layer and no TPBi doped in the light-emitting layer; the experimental procedure was as follows:
(1) And repeating the steps (1), (2), (3) and (4) of the device A.
(2) and sequentially plating an organic layer, a luminescent layer, LiF and Al on the ITO glass substrate, wherein the thickness of the luminescent layer is 30nm, the thermal retardation fluorescent material 4CzIPN is doped as an object, and the doping proportion is 8 wt%. And then, after the coating machine is naturally cooled for half an hour, opening the coating machine and taking out the prepared OLED device.
(3) and packaging the OLED device.
(4) And carrying out a light emitting test on the OLED device.
The principle of the invention is as follows:
A carrier modulation layer CBP with the thickness of 10nm is added in the thermal delay fluorescent device, so that an exciton recombination area is limited, the exciton utilization rate is improved, and the efficiency of the device is improved; an electron transport material TPBi is added into the luminous layer to serve as an auxiliary doping agent, so that the efficiency of the device is improved. The hole transport capability of CBP as a main material is far better than that of electron transport capability, and the electron transport material TPBi is added to balance the transport rates of electrons and holes of a light-emitting layer, so that the efficiency of the device is greatly improved. Through efficiency measurement, the efficiency of the two thermal delay fluorescent OLED devices is compared, the efficiency of the thermal delay fluorescent OLED device which is added into the modulation layer CBP and the luminous layer is doped with TPBi is greatly improved, the exciton utilization rate is improved, and the device efficiency is greatly improved.
The invention has the advantages that:
The invention adds a carrier modulation layer CBP and adds TPBi as an auxiliary doping material into the light-emitting layer of the thermal delay fluorescence OLED device, thereby improving the exciton utilization rate of the light-emitting layer and improving the efficiency of the device, and the efficiency of the prepared thermal delay fluorescence OLED device is greatly improved by taking CBP as a main light-emitting material and 4CzIPN as a thermal delay fluorescence object doping material.
Drawings
Fig. 1 is a diagram showing a structure of a device.
Fig. 2 is a device energy level diagram.
Fig. 3 is a graph of efficiency of the device as a function of current density.
Detailed Description
As shown in fig. 1 and 2, a method for improving efficiency of a thermal retardation fluorescence OLED device includes a carrier modulation layer, a light emitting layer, and the light emitting layer is composed of a host light emitting material and a guest doping material, and is characterized in that: adding a carrier modulation layer CBP, and adding an auxiliary doping material TPBi into the light-emitting layer.
according to the method for improving the efficiency of the thermal delay fluorescence OLED device, CBP is selected as a carrier modulation layer of the thermal delay fluorescence OLED device, CBP is selected as a main material of a light emitting layer, TPBi is selected as an auxiliary doping material, and 4CzIPN is selected as an object doping material.
the method for improving the efficiency of the thermal retardation fluorescence OLED device is characterized in that the thickness of a carrier modulation layer CBP is 0 or 10nm, the total thickness of a luminescent layer main body luminescent material CBP, an object doping material thermal retardation fluorescence material 4CzIPN and an auxiliary doping material TPBi is 30nm, wherein the concentration of the object thermal retardation fluorescence material 4CzIPN is kept unchanged when the concentration is 8wt%, and the concentration range of the auxiliary doping material TPBi is 0wt% to 50 wt%.
The thickness CBP of the carrier modulation layer is 10nm, and the proportion of the auxiliary doping material TPBi of the luminous layer and the thermal delay fluorescent material 4CzIPN of the guest doping material is 50wt% and 8 wt%.
forming a carrier modulation layer on an ITO glass substrate of the thermal delay fluorescence OLED device by CBP evaporation; and the host material CBP, the guest material 4CZIPN and the auxiliary material TPBi are jointly evaporated on the ITO glass substrate of the thermal delay fluorescent OLED device to form a light-emitting layer.
The following provides a detailed description of embodiments of the invention. The embodiment provides a detailed implementation mode and a specific operation process based on the technical scheme of the invention. The scope of the present invention includes, but is not limited to, the following examples.
Referring to fig. 1, 2, to prepare a device of device a (ITO/TAPC (30nm)/CBP (10nm)/CBP: TPBi:4CzIPN =30wt%:8wt% (30nm)/TPBi (40nm)/LiF (1nm)/Al (100nm)) structure, we performed the following steps:
(1) And cleaning the ITO substrate:
Ultrasonic cleaning treatment was performed in an ITO washing solution for 30min, and then ultrasonic pure water treatment was performed in pure water for 10 min.
(2) Heating and drying
After the ITO was cleaned, the water on the ITO glass substrate was blown clean with nitrogen, and then heated on a heating table at 120 ℃ for 10min to dry the moisture.
(3) And ultraviolet light treatment:
After the steps (1) and (2), the ITO substrate is treated for 10min by using an ultraviolet light cleaning machine so as to remove organic matter residues on the surface of the ITO substrate, increase the number of hydroxyl groups on the surface of the ITO substrate and effectively improve the work function of the surface of the ITO substrate.
(4) After the ITO glass substrate has been processed through steps (1), (2), (3), we transfer the ITO substrate into a high vacuum coater chamber, after which the vacuum degree of the chamber is raised to 3 x 10-6 Torr, followed by vapor deposition of TAPC, CBP, TPBi, LiF and Al at the rates of 1 a/s, 0.4 a/s and 1 a/s, respectively, with film layer thicknesses of 30nm, 10nm, 40nm, 1nm and 100nm, respectively. The light-emitting layer is CBP as a host material, 4CzIPN as a guest material, TPBi as an auxiliary dopant and has a thickness of 30nm, wherein the proportion of TPBi to the thermal retardation fluorescent material 4CzIPN is 50wt% and 8wt%, respectively. And after the coating is finished, opening the coating machine to take out the device after the coating machine is cooled to a proper temperature.
(5) and packaging the device:
Taking out the coated device, adhering the glass cover plate coated with the curing adhesive and the device substrate in an inert gas filled environment, and irradiating for 3min under ultraviolet light for curing.
(6) The packaged device was subjected to an optoelectrical test using a spectroscopic photometer 2400, and the test result obtained after the test processing is shown as a in fig. 3.
for preparation of control device B (ITO/TAPC (30nm)/CBP:4CzIPN =8 wt%)
The device with the structure of (30nm)/TPBi (40nm)/LiF (1nm)/Al (100nm)) comprises the following steps:
(1) And repeating the steps (1), (2) and (3) of preparing the device A.
(2) After the ITO glass substrate has been processed through steps (1), (2), (3), we transfer the ITO substrate into a high vacuum coater chamber, then raise the vacuum of the chamber to 3 x 10-6 Torr, then vapor deposit TAPC, TPBi, LiF and Al at the rates of 1 a/s, 0.4 a/s and 1 a/s, respectively, with the film layers having thicknesses of 30nm, 40nm, 1nm and 100nm, respectively. The light-emitting layer is made of CBP (cubic boron nitride) serving as a host material and 4CzIPN serving as a guest material, the thickness is 30nm, and the proportion of the 4CzIPN serving as a thermal retardation fluorescent material is 8 wt%. And after the coating is finished, opening the coating machine to take out the device after the coating machine is cooled to a proper temperature.
(3) And packaging the device:
Taking out the coated device, adhering the glass cover plate coated with the curing adhesive to the device substrate in an inert gas filled environment, and then irradiating for 3min under ultraviolet light for curing.
(4) the packaged device was subjected to an optoelectrical test using a spectroscopic photometer 2400, and the test result obtained after the test processing is shown as B in fig. 3.
Through efficiency tests of the devices A and B, as shown in FIG. 3, the Current Efficiency (CE) 61.04 cd/A and the External Quantum Efficiency (EQE) 23.93% of the device A with TPBi added can be obtained, compared with the device B without TPBi, while the Current Efficiency (CE) 23.19 cd/A and the External Quantum Efficiency (EQE) 7.47% of the device B without TPBi added can be obtained, which shows that the efficiency of the device A with TPBi added in the light-emitting layer of the thermal retardation fluorescent device can be obviously improved.
Claims (5)
1. A method for improving the efficiency of a thermal delay fluorescence OLED device is characterized in that: the thermal retardation fluorescence OLED device comprises a carrier modulation layer and a light-emitting layer, wherein the light-emitting layer comprises a host light-emitting material, a guest doping material and an auxiliary doping material, the carrier modulation layer is 4, 4-Bis (9-carbazole) biphenyl (4, 4'-Bis (N-carbazolyl) -1,1' -biphenol, CBP), and the auxiliary doping material is 1,3, 5-tris (1-phenyl-1H-benzimidazole-2-yl) benzene (1, 3,5-Tri (1-phenyl-1H-benzimidazole [ d ] imidozol-2-yl) phenyl, TPBi).
2. The assisted doping method of claim 1 for improving the efficiency of a thermal retardation OLED device, comprising: the host luminescent material is 4, 4-Bis (9-carbazole) biphenyl (4, 4'-Bis (N-carbazolyl) -1,1' -biphenyl, CBP), and the guest doping material is a thermal retardation fluorescent material 4 CzIPN.
3. The method of claim 2, wherein the method comprises: the carrier modulation layer has a thickness of 0nm or 10nm, and the thicknesses of the host luminescent material, the guest doping material and the auxiliary doping material are 30nm together, wherein the concentration of the guest doping material is 8wt%, and the concentration of the auxiliary doping material is 0wt% to 50 wt%.
4. the method of claim 3, wherein the method comprises: the carrier modulation layer CBP is 10nm, and the concentration of the auxiliary doping material is 50 wt%.
5. the method of claim 2, wherein the method comprises: the 4, 4-Bis (9-carbazole) biphenyl (4, 4'-Bis (N-carbazolyl) -1,1' -biphenyl, CBP) is evaporated on an ITO glass substrate of the thermal delay fluorescent OLED device to form a carrier modulation layer; and the host luminescent material, the guest doping material and the auxiliary doping material are jointly evaporated on the ITO glass substrate of the thermal delay fluorescent OLED device to form a luminescent layer.
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| US20090189509A1 (en) * | 2008-01-29 | 2009-07-30 | Tsinghua University | Organic light emitting devices |
| CN102270751A (en) * | 2011-07-26 | 2011-12-07 | 昆山维信诺显示技术有限公司 | Organic electrophosphorescent luminescent device and preparation method thereof |
| CN108463894A (en) * | 2015-12-28 | 2018-08-28 | 国立大学法人九州大学 | Organic electroluminescent device |
| CN109244256A (en) * | 2018-08-01 | 2019-01-18 | 华南理工大学 | Efficient undoped ultra-thin light-emitting layer thermal activation delayed fluorescence Organic Light Emitting Diode and preparation method thereof |
-
2019
- 2019-08-09 CN CN201910734390.8A patent/CN110544748A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090189509A1 (en) * | 2008-01-29 | 2009-07-30 | Tsinghua University | Organic light emitting devices |
| CN102270751A (en) * | 2011-07-26 | 2011-12-07 | 昆山维信诺显示技术有限公司 | Organic electrophosphorescent luminescent device and preparation method thereof |
| CN108463894A (en) * | 2015-12-28 | 2018-08-28 | 国立大学法人九州大学 | Organic electroluminescent device |
| CN109244256A (en) * | 2018-08-01 | 2019-01-18 | 华南理工大学 | Efficient undoped ultra-thin light-emitting layer thermal activation delayed fluorescence Organic Light Emitting Diode and preparation method thereof |
Non-Patent Citations (1)
| Title |
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