CN115884615A - Quantum dot light-emitting device and display panel - Google Patents

Quantum dot light-emitting device and display panel Download PDF

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CN115884615A
CN115884615A CN202111129846.1A CN202111129846A CN115884615A CN 115884615 A CN115884615 A CN 115884615A CN 202111129846 A CN202111129846 A CN 202111129846A CN 115884615 A CN115884615 A CN 115884615A
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quantum dot
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quantum
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dot light
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陈开敏
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TCL Technology Group Co Ltd
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TCL Technology Group Co Ltd
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Priority to PCT/CN2022/118607 priority patent/WO2023045811A1/en
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    • 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
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
    • 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]
    • H10K50/14—Carrier transporting layers
    • H10K50/15—Hole transporting layers

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Abstract

The application discloses a quantum dot light-emitting device and a display panel. The quantum dot light-emitting device comprises a first electrode layer, a quantum dot light-emitting layer and a second electrode layer which are sequentially stacked; the quantum dots of the quantum dot light-emitting layer are quantum dots with a core-shell structure and comprise a core layer and a shell layer; the quantum dot light-emitting layer comprises a first quantum dot layer and a second quantum dot layer, the second quantum dot layer is arranged on one side, deviating from the first electrode layer, of the first quantum dot layer, and the shell layer energy level width of the quantum dots of the second quantum dot layer is larger than that of the quantum dots of the first quantum dot layer. The quantum dot light-emitting device effectively improves the injection balance of electrons and holes through the arrangement of the quantum dot light-emitting layer, and improves the efficiency of the device under the conventional use brightness while keeping the long service life of the quantum dot light-emitting device.

Description

Quantum dot light-emitting device and display panel
Technical Field
The application relates to the technical field of quantum dot electroluminescence, in particular to a quantum dot light-emitting device and a display panel.
Background
The quantum dot electroluminescence (QLED) printing display technology is considered as a novel flat panel display technology which grows fastest in the future, has the advantages of all solid states of an OLED, low energy consumption, ultra-thinness, no visual angle limitation, strong color expression, wide working temperature range, excellent anti-seismic performance, easiness in realizing flexible display and the like, has the advantages of long service life and high brightness of an LCD, is suitable for preparation by a solution method, and has the advantages of potential low manufacturing cost and the like. Meanwhile, the QLED has the excellent characteristics of large-area film forming, low power consumption, easy spectrum adjustment and the like, can be used as an ideal planar light source, and has wide application prospect in the field of future energy-saving, environment-friendly and green illumination.
At present, through the improvement of materials and the optimization design of device structures, the maximum current efficiency which can be achieved by quantum dot electroluminescence (QLED) and the service life of devices are greatly broken through, wherein the maximum current efficiency of red and green quantum dot devices can approach 100%, and the service life of the red devices also approaches the commercial standard.
One key index that needs to be improved for the QLED to be commercially available is that the device is about 300cd/m 2 The efficiency at luminance is used conventionally. Although the maximum current efficiency of the QLED is basically in accordance with the standard, the light emitting efficiency under the conventional use brightness is very low, and is usually only half or even lower than the maximum efficiency. There are currently fewer solutions to this problem.
Therefore, it is highly desirable to provide a quantum dot light emitting device, which can improve the light emitting efficiency of the device under the conventional use brightness on the premise of maintaining the long service life of the quantum dot light emitting device.
Disclosure of Invention
The application provides a quantum dot light-emitting device, which enables the HOMO (Highest Occupied Molecular Orbital) energy level difference between a hole transport layer and a quantum dot layer to be smaller and a hole injection barrier to be relatively reduced through the arrangement of a quantum dot light-emitting layer; meanwhile, an electron injection barrier is added, so that the injection balance of electrons and holes is effectively improved, and the efficiency of the quantum dot light-emitting device under the conventional use brightness is improved while the long service life of the quantum dot light-emitting device is kept.
The embodiment of the application provides a quantum dot light-emitting device, which comprises a first electrode layer, a quantum dot light-emitting layer and a second electrode layer which are sequentially stacked;
the quantum dots of the quantum dot light-emitting layer are quantum dots with a core-shell structure and comprise a core layer and a shell layer;
the quantum dot light-emitting layer comprises a first quantum dot layer and a second quantum dot layer, the second quantum dot layer is arranged on one side, deviating from the first electrode layer, of the first quantum dot layer, and the shell layer energy level width of the quantum dots of the second quantum dot layer is larger than that of the quantum dots of the first quantum dot layer.
Optionally, in some embodiments of the present application, a hole transport layer is further disposed between the first electrode layer and the quantum dot light emitting layer. The material of the hole transport layer is selected from one or more of TFB, PVK, TCTA, TPD and CBP.
Optionally, in some embodiments of the present application, an electron transport layer is further disposed between the quantum dot light emitting layer and the second electrode layer. The material of the electron transport layer is selected from ZnO and TiO 2 And SnO 2 One or more of them.
Optionally, in some embodiments of the present application, the quantum dot light emitting layer further includes a third quantum dot layer disposed on a side of the second quantum dot layer away from the first quantum dot layer, and a shell energy level width of quantum dots of the third quantum dot layer is greater than a shell energy level width of quantum dots of the second quantum dot layer.
That is, the quantum dot light emitting layer includes multiple quantum dot layers, such as, but not limited to: 2 quantum dot layers, 3 quantum dot layers, 4 quantum dot layers, etc. In detail, in the multi-layer quantum dot layer, the quantum dot layer arranged closer to the electron transport layer has a wider energy level width of the quantum dot shell layer; in other words, the quantum dot layer disposed closer to the hole transport layer has a narrower energy level width of the quantum dot shell layer.
Optionally, in some embodiments of the present application, the total thickness of the quantum dot light emitting layer, i.e., all quantum dot layers, is in the range of 5 to 80 nm. The thicknesses of the first quantum dot layer, the second quantum dot layer and the third quantum dot layer are respectively between 5 and 30nm, namely the thickness of the single quantum dot layer is between 5 and 30 nm.
Optionally, in some embodiments of the present application, in the quantum dot light emitting layer, the spectral peak position fluctuation of all quantum dot layers is less than or equal to 2nm. In the quantum dot light-emitting layer, the fluctuation of the light half-peak width of all quantum dot layers is less than or equal to 1nm.
Optionally, in some embodiments of the present application, the quantum dot is a Type i core-shell quantum dot, and the shell energy level may completely cover the core energy level.
Optionally, in some embodiments of the present application, the shell layer of the quantum dot is a multilayer shell layer.
Optionally, in some embodiments of the present application, an outermost shell energy level width of the quantum dots of the second quantum dot layer is greater than an outermost shell energy level width of the quantum dots of the first quantum dot layer.
Optionally, in some embodiments of the present application, an outermost shell energy level width of the quantum dots of the third quantum dot layer is greater than an outermost shell energy level width of the quantum dots of the second quantum dot layer.
Optionally, in some embodiments of the present application, the energy level widths of the multiple shell layers become wider from inside to outside.
Optionally, in some embodiments of the present application, the luminescence peak positions of the core-shell structure quantum dots are consistent.
Optionally, in some embodiments of the present application, the quantum dots are selected from one or more of blue quantum dots, red quantum dots, and green quantum dots.
Optionally, in some embodiments of the present application, the core layer of the quantum dot is selected from one or more of CdSe, cdS, znSe, znS, cdTe, znTe, cdznsse, znSeTe, znste, znTeS, cdSeS, cdSeTe, cdTeS, cdzneses, cdZnSeTe, cdzneste, cdZnSeTe, inP este, inP, inAs, inAsP, pbS, pbSe, pbTe, pbSeS, pbSeTe, and PbSTe.
Optionally, in some embodiments of the present application, the shell of the quantum dot is selected from one or more of CdSe, cdS, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, zneses, cdSeS, cdSeTe, cdTeS, cdZnSeS, cdZnSeTe, cdSeSTe, znSeTe, cdznsette, inP, inAs, inAsP, pbS, pbSe, pbTe, pbSeS, pbSeTe, and PbSTe.
Correspondingly, the application also provides a display panel, which comprises the quantum dot light-emitting device.
The beneficial effect of this application lies in:
the quantum dot light-emitting device of this application has increased quantum dot layer thickness through the quantum dot luminescent layer that sets up to contain a plurality of quantum dot layers to, the quantum dot shell energy level of the quantum dot layer that is close to the hole transport layer more is narrower, and the quantum dot shell energy level that is close to the electron transport layer more is wider. Specifically, the thickness of the quantum dot layer is increased by designing the luminescent layer into a multilayer quantum dot mode, so that the efficiency of the quantum dot luminescent device under the conventional use brightness is improved, and meanwhile, the quantum dots close to the hole transport layer are selected from quantum dots with narrow shell energy levels, so that the HOMO energy level difference between the hole transport layer and the quantum dot layer is smaller, the hole injection barrier is relatively reduced, and the injection is easier; on the other hand, the quantum dots close to the electron transport layer are quantum dots with wide shell energy level, and the electron injection barrier is increased, so that the injection balance of electrons and holes is effectively improved, and the long service life of the multilayer quantum dot device is realized.
By adjusting the light-emitting layer in the quantum dot device, the efficiency of the device under the conventional use brightness is greatly improved on the premise of keeping the good service life of the device, the performance of the device is more in line with the commercial application standard, and the application of the quantum dot electroluminescent technology and the target of the display industry are further advanced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a first schematic structural diagram of a quantum dot light-emitting device provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram ii of a quantum dot light-emitting device provided in an embodiment of the present application;
fig. 3 is a schematic energy level diagram of a quantum dot light emitting device provided in an embodiment of the present application;
fig. 4 is a schematic structural diagram of a display panel provided in an embodiment of the present application;
fig. 5 is a band gap diagram of a common material.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The embodiment of the application provides a quantum dot light-emitting device and a display panel. The following are detailed descriptions. It should be noted that the following description of the embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". The terms first, second, third and the like are used merely as labels, and do not impose numerical requirements or an established order. Various embodiments of the invention may exist in a range of versions; it is to be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention; accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, it is contemplated that the description of a range from 1 to 6 has specifically disclosed sub-ranges such as, for example, from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within a range such as, for example, 1, 2, 3,4, 5, and 6, as applicable regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any number (fractional or integer) recited within the indicated range.
The embodiment of the application provides a quantum dot light-emitting device. Referring to fig. 1, the quantum dot light emitting device 100 includes a first electrode layer 110, a hole injection layer 120, a hole transport layer 130, a quantum dot light emitting layer 140, an electron transport layer 150, and a second electrode layer 160 disposed on a substrate 101. For example, the first electrode layer 110 and the second electrode layer 160 are an anode and a cathode, respectively.
The quantum dots of the quantum dot light-emitting layer are quantum dots with a core-shell structure and comprise a core layer and a shell layer. The quantum dots are Type I core-shell structure quantum dots, and the shell energy level can completely cover the core energy level. That is, the energy level widths (band gaps) of the core layer and the shell layer of the quantum dot become wider in order from the inside to the outside.
The quantum dot light emitting layer 140 includes a plurality of quantum dot layers, for example, 2, 3,4, or 5 quantum dot layers. In the direction from the hole transport layer 130 to the electron transport layer 150, the shell energy level of the quantum dots selected for each quantum dot layer in the plurality of quantum dot layers gradually widens. Furthermore, the total thickness of the quantum dot light-emitting layer, namely all the quantum dot layers is in the range of 5-80 nm; wherein the thickness of the quantum dot layer of each single layer is between 5 and 30 nm.
In one embodiment, referring to fig. 1, the quantum dot light emitting layer 140 includes a first quantum dot layer 1401 and a second quantum dot layer 1402. The second quantum dot layer 1402 is disposed on a side of the first quantum dot layer 1401 facing away from the hole transport layer 130. Further, the shell level width of the quantum dots of the second quantum dot layer 1402 is larger than the shell level width of the quantum dots of the first quantum dot layer 1401. Further, the shell of the quantum dot may be a multi-layer shell, in which case, the outermost shell energy level width of the quantum dot of the second quantum dot layer is greater than the outermost shell energy level width of the quantum dot of the first quantum dot layer.
In another embodiment, referring to fig. 2, the quantum dot light emitting layer 140 includes a first quantum dot layer 1401, a second quantum dot layer 1402, and a third quantum dot layer 1403. The second quantum dot layer 1402 is disposed on a side of the first quantum dot layer 1401 facing away from the hole transport layer 130, and the third quantum dot layer 1403 is disposed on a side of the second quantum dot layer 1402 facing away from the first quantum dot layer 1401. Further, the shell level width of the quantum dots of the second quantum dot layer 1402 is larger than the shell level width of the quantum dots of the first quantum dot layer 1401; the shell level width of the quantum dots of the third quantum dot layer 1403 is greater than the shell level width of the quantum dots of the second quantum dot layer 1402. Further, the shell of the quantum dot may be a multi-layer shell, in which case, an outermost shell energy level width of the quantum dot of the third quantum dot layer is greater than an outermost shell energy level width of the quantum dot of the second quantum dot layer.
That is, the quantum dot light emitting layer is formed by stacking a plurality of quantum dot layer films. And the quantum dot layers are composed of cores and shells, and the luminescence peak positions are basically consistent. Further, each quantum dot layer is different in that the closer to the cathode, the wider the shell level; the closer to the anode, the narrower the shell energy level of the quantum dot.
Further, the shell layer of the quantum dot can be a multilayer shell layer; it is understood that the shell level refers to the widest shell level of the multi-layered shell. Further, the energy level width (band gap) of the multi-layered shell layer becomes wider in order from the inner (core) to the outer. Fig. 3 is a schematic diagram of energy levels of a quantum dot light emitting device. The white part of the quantum dot light emitting layer shown in fig. 3 represents the energy level position and thickness of the quantum dot shell layer, and the dark color represents the energy level position of the quantum dot light emitting core. The energy level width (band gap) of an individual material is generally measured by a method such as UPS; for example, referring to fig. 5, fig. 5 shows the bandgap of a common material.
In some embodiments, the spectral peak position fluctuations of all quantum dot layers in the quantum dot light emitting layer are ≦ 2nm. Further, in the quantum dot light-emitting layer, the fluctuation of the light half-peak width of all quantum dot layers is less than or equal to 1nm. That is, the luminescence peak positions of the core-shell structure quantum dots are consistent.
In some embodiments, the quantum dots are selected from one or more of blue, red and green quantum dots. For example, the quantum dots may be blue quantum dots; for example, the quantum dots may be red quantum dots; for example, the quantum dots may be green quantum dots. The color of light generated due to the quantum dots depends on the kind and size of the quantum dots. Conceivably, the light emission color of the quantum dots can be determined according to the selected specific kinds of the quantum dots and the sizes thereof; conversely, the type and size of the quantum dots may be selected according to the desired color of the quantum dots.
In some embodiments, the compounds of the core layer of the quantum dot are independently selected from: group II-VI CdSe, cdS, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, znSeS, znSeTe, znTeS, cdSeS, cdSeTe, cdTeS, cdZnSeS, cdZnSeTe, cdZnSTe, cdSeSTe, znSeTe or CdZnSeTe; or InP, inAs or InAsP from group III-V; or group IV-VI PbS, pbSe, pbTe, pbSeS, pbSeTe or PbSTe; or a combination of any one or more of the above.
In some embodiments, the compound of the shell layer of the quantum dot is independently selected from: group II-VI CdSe, cdS, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, znSeS, znSeTe, znTeS, cdSeS, cdSeTe, cdTeS, cdZnSeS, cdZnSeTe, cdZnSTe, cdSeSTe, znSeTe or CdZnSeTe; or InP, inAs or InAsP from group III-V; or group IV-VI PbS, pbSe, pbTe, pbSeS, pbSeTe or PbSTe; or a combination of any one or more of the above.
In some embodiments, the core-shell structure quantum dot may be CdSe// ZnSe, cdSe// ZnSe// ZnSeS, cdSe// ZnSe// ZnS, cdSe// CdSZnSe// CdZnS, inP// GaP// ZnSe, inP// GaP// ZnS. For example, cdSe// ZnSe core-shell structure quantum dots, cdSe is the core layer and ZnSe is the shell layer. For example, cdSe// ZnSe// ZnSeS core-shell structure quantum dots are CdSe, znSe and ZnSeS from inside to outside in sequence.
It will be understood by those skilled in the art that the quantum dot light emitting device 100 shown in fig. 1 and 2 is only an example, and those skilled in the art may add or reduce a part of the functional layer according to the actual process requirements. The quantum dot light-emitting device is formed by the conventional process in the field by using the conventional materials in the field.
For example, the anode may be made of Indium Tin Oxide (ITO). For example, the hole injection layer may be made of poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid (PEDOT: PSS), polythiophene, or polyaniline. For example, the hole transport layer may be made of one or a combination of TFB, PVK, TCTA, TPD, and CBP. For example, the electron transport layer may be made of ZnO or TiO 2 Or SnO 2 And (4) preparing. For example, whatThe cathode can be made of Al or Ag.
The preparation method of the quantum dot device comprises the following steps: the method comprises the steps of preparing a first electrode, a hole injection layer, a hole transport layer, a quantum dot light emitting layer (such as a first quantum dot layer, a second quantum dot layer and a third quantum dot layer) in sequence, an electron transport layer and a second electrode on a substrate in sequence, and packaging.
Referring to fig. 4, the display panel according to the embodiment of the present disclosure includes the quantum dot light emitting device 100, such as a QLED device.
The specific embodiment is as follows:
example 1
In this embodiment, a quantum dot light emitting device (QLED device) is provided, as shown in fig. 2, the quantum dot light emitting device 100 includes a first electrode layer 110, a hole injection layer 120, a hole transport layer 130, a quantum dot light emitting layer 140 (including a first quantum dot layer 1401, a second quantum dot layer 1402, and a third quantum dot layer 1403), an electron transport layer 150, and a second electrode layer 160, which are sequentially stacked on a substrate 101. The first electrode layer 110 is an anode, and the second electrode layer 160 is a cathode.
Specifically, in the quantum dot light-emitting device, ITO is used for the anode (first electrode layer 110). The hole injection layer 120 adopts PEDOT PSS. The hole transport layer 130 employs TFB; the quantum dot light emitting layer 140 includes a first quantum dot layer 1401, a second quantum dot layer 1402 and a third quantum dot layer 1403, core-shell quantum dots having structures of CdSe// ZnSe, cdSe// ZnSe// ZnSeS, and CdSe// ZnSe// ZnSeS are adopted, wherein particle diameters of the quantum dots are 8nm, 10nm and 12nm, thicknesses of the quantum dot layers are 8nm, 10nm and 12nm, respectively, se and S in the outermost ZnSeS shell layer of the quantum dots CdSe// ZnSe// ZnSeS account for 50%, and luminescence peak positions and half-peak widths of the three layers of quantum dots are 465nm and 20nm, respectively. The energy level width (band gap) can be referred to as shown in fig. 5. The electron transport layer 150 is made of ZnO. The cathode (second electrode layer 160) is made of Al.
Example 2
In this embodiment, a quantum dot light emitting device (QLED device) is provided, and as shown in fig. 2, the quantum dot light emitting device 100 includes a first electrode layer 110, a hole injection layer 120, a hole transport layer 130, a quantum dot light emitting layer 140 (including a first quantum dot layer 1401, a second quantum dot layer 1402, and a third quantum dot layer 1403 in sequence), an electron transport layer 150, and a second electrode layer 160, which are sequentially stacked on a substrate 101. The first electrode layer 110 is an anode, and the second electrode layer 160 is a cathode.
Specifically, in the quantum dot light-emitting device, ITO is used for the anode (first electrode layer 110). PSS is used as the hole injection layer 120. The hole transport layer 130 employs TFB. The quantum dot light-emitting layer 140 comprises a first quantum dot layer 1401, a second quantum dot layer 1402 and a third quantum dot layer 1403, wherein core-shell quantum dots with double-layer shell layers of CdSe// CdZnSe// CdZnS are adopted, the particle sizes of the quantum dots are 15nm, the light-emitting peak positions of the three layers of quantum dots are 630nm, 631nm and 630nm respectively, and the half-peak widths of the three layers of quantum dots are 25nm, 26nm and 25nm respectively; in addition, the Cd content in the outermost CdZnS shell layer of first quantum dot layer 1401 is 40wt%, the Cd content in the outermost CdZnS shell layer of second quantum dot layer 1402 is 20wt%, and the Cd content in the outermost CdZnS shell layer of third quantum dot layer 1403 is 10wt%. The electron transport layer 150 is made of ZnO. The cathode (second electrode layer 160) is made of Al. In the present embodiment, the CdZnS alloy material can be regarded as a mixture of CdS and ZnS, and as shown in fig. 5, the band gap of CdS is narrower than that of ZnS, and the band gap of their alloy approaches that of a more dominant material. The more Cd is occupied, the narrower the band gap is. Fig. 5 shows the band gap of a common material, and the band gap of an individual material is generally measured by a method such as UPS.
Example 3
Referring to fig. 1, the quantum dot light emitting device 100 includes a first electrode layer 110, a hole injection layer 120, a hole transport layer 130, a quantum dot light emitting layer 140 (including a first quantum dot layer 1401, a second quantum dot layer 1402), an electron transport layer 150, and a second electrode layer 160, which are sequentially stacked on a substrate 101. The first electrode layer 110 is an anode, and the second electrode layer 160 is a cathode.
Specifically, in the quantum dot light-emitting device, ITO is used for the anode (first electrode layer 110). PSS is used as the hole injection layer 120. The hole transport layer 130 employs TFB; the quantum dot light emitting layer 140 includes a first quantum dot layer 1401 and a second quantum dot layer 1402, and core-shell quantum dots having structures of InP// GaP// ZnSe, inP// GaP// ZnS, respectively; the particle diameters of the two quantum dots are 12nm, the luminescence peaks are 531nm and 532nm respectively, the half-peak widths are 28nm and 29nm respectively, and the thicknesses of the quantum dot layers are 24nm and 18nm respectively. The electron transport layer 150 is made of ZnO. The cathode (second electrode layer 160) is made of Al.
Comparative example 1
Comparative example 1 differs from example 1 in that: the quantum dot light-emitting layer only comprises one quantum dot layer, core-shell quantum dots adopting CdSe// ZnSe// ZnSeS are adopted, and the thickness of the quantum dot light-emitting layer is consistent with that of the second quantum dot layer in the embodiment 1.
Comparative example 2
Comparative example 2 differs from example 1 in that: the quantum dot light-emitting layer only comprises one quantum dot layer, core-shell quantum dots of CdSe// ZnSe// ZnSeS are adopted, and the thickness of the quantum dot light-emitting layer is consistent with that of the quantum dot light-emitting layer in the embodiment 1 (all quantum dot layers are stacked).
Example 4
In an embodiment of the present invention, referring to fig. 4, the display panel 200 includes: a substrate 210, wherein a plurality of the qd-led devices 100 are formed on the substrate 210. It will be understood by those skilled in the art that the substrate 210 may also have a structure formed thereon through several previous processes, for example, there may be an inorganic film layer, several layers in a tft structure, or complete tfts and traces may have been formed. Of course, the display panel 200 may also include other known structures such as a package cover, which are not described herein.
Experimental example 1 related photoelectric property test of QLED device
The QLED devices obtained in example 1, example 2, example 3, comparative example 1 and comparative example 2 were tested at 2mA current for CE @ max, CE @300knit and T95@1knit, respectively, and the results are detailed in Table 1. CE refers to current efficiency at different voltagesThe value varies, CE @ max being the maximum value that the current efficiency of the device can reach. CE @300nit refers to the current efficiency of the device at 300nit of light emission luminance. T95 refers to the time required for the device to decay from the initial luminance to 95% luminance. 1knit is 1000nit and 1000cd/m 2 And represents luminance. T95@1knit is the time required for the initial luminance to be set at 1000nit, decaying to 950nit, and is commonly used as an indicator of the lifetime of the device. If the lifetime is not ideal, T50@100nit is described, i.e. the time required to start a brightness of 100nit and decay to 50 nit.
TABLE 1
Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2
CE@max(cd/A) 18.6 50.8 80.2 17.3 17.5
CE@300knit(cd/A) 17.0 45.2 75.1 2.4 15.8
T95@1knit(hrs) 115 7k 3k 107 11
It can be seen from table 1 that, after a quantum dot wide energy level shell and mechanisms with different thicknesses are introduced into a quantum dot light-emitting layer of the QLED device, the service life of the device is well maintained under the condition of keeping the luminous efficiency to be improved. Increasing the thickness of the quantum dot light-emitting layer can improve the light-emitting efficiency (CE @ 300knit) of the device under the conventional use brightness, and the service life is obviously reduced.
Specifically, according to comparison between comparative example 1 and comparative example 2, it can be found that although the efficiency of the QLED under the conventional use brightness can be effectively improved by increasing the thickness of the quantum dot light emitting layer in the QLED, the carrier injection of the device is unbalanced due to the adoption of the quantum dot light emitting layer in comparative example 2, so that the service life of the QLED is greatly reduced.
Specifically, according to comparison between examples 2 and 3 and the comparative example, it can be seen that the efficiency is improved after the thickness is increased, but the lifetime reaches the thousand-hour level due to the increase of the shell level increment (from the anode to the cathode).
In conclusion, by adjusting the quantum dot light-emitting layer in the quantum dot device, on the premise of maintaining the good service life of the device, the efficiency of the device under the conventional use brightness is greatly improved, the performance of the device is more in line with the commercial application standard, and the application of the quantum dot electroluminescent technology and the target of the display industry are further advanced.
This application increases quantum dot layer thickness through the mode of designing luminescent layer for multilayer quantum dot to promote quantum dot light emitting device efficiency under the conventional use luminance, the quantum dot that will be close to hole transport layer simultaneously selects the narrow quantum dot of shell energy level, and the HOMO energy level difference between hole transport layer and the quantum dot layer is littleer this moment, and the hole injection barrier reduces relatively, injects into more easily. On the other hand, the quantum dots close to the electron transport layer are quantum dots with wide shell energy level, and the electron injection barrier is increased, so that the injection balance of electrons and holes is effectively improved, and the long service life of the multilayer quantum dot device is realized.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
The foregoing detailed description is directed to a quantum dot light emitting device and a display panel provided in the embodiments of the present application, and specific examples are applied herein to explain the principles and implementations of the present application, and the description of the foregoing embodiments is only used to help understanding the method and the core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.

Claims (11)

1. A quantum dot light-emitting device is characterized by comprising a first electrode layer, a quantum dot light-emitting layer and a second electrode layer which are sequentially stacked;
the quantum dots of the quantum dot light-emitting layer are core-shell structure quantum dots, and the core-shell structure quantum dots comprise core layers and shell layers;
the quantum dot light emitting layer comprises a first quantum dot layer and a second quantum dot layer, the second quantum dot layer is arranged on one side, deviating from the first electrode layer, of the first quantum dot layer, and the shell layer energy level width of the quantum dots of the second quantum dot layer is larger than that of the quantum dots of the first quantum dot layer.
2. The quantum dot light-emitting device according to claim 1, wherein the quantum dot light-emitting layer further comprises a third quantum dot layer disposed on a side of the second quantum dot layer facing away from the first quantum dot layer, and wherein a shell-level width of quantum dots of the third quantum dot layer is greater than a shell-level width of quantum dots of the second quantum dot layer.
3. The qd-dot light emitting device of claim 1 or 2, characterized in that, in the qd-dot light emitting layer, the spectral peak position fluctuation of all the qd-dot layers is less than or equal to 2nm; and/or
In the quantum dot light-emitting layer, the light half-peak width fluctuation of all quantum dot layers is less than or equal to 1nm.
4. The qd-led device of claim 2, wherein the thickness of the qd-led layer is 5nm to 80nm; and/or
The thicknesses of the first quantum dot layer, the second quantum dot layer and the third quantum dot layer are respectively between 5nm and 30 nm.
5. The quantum dot light-emitting device according to claim 1, wherein the quantum dot is a Type i core-shell structure quantum dot.
6. The quantum dot light-emitting device according to claim 1 or 5, wherein the shell layer of the quantum dot is a multilayer shell layer; preferably, the energy level width of the multi-layered shell layer is widened from the inside to the outside.
7. The quantum dot light-emitting device according to claim 6, wherein an outermost shell level width of the quantum dots of the second quantum dot layer is larger than an outermost shell level width of the quantum dots of the first quantum dot layer; and/or
And the outermost shell energy level width of the quantum dots of the third quantum dot layer is greater than that of the quantum dots of the second quantum dot layer.
8. The quantum dot light-emitting device according to claim 1, wherein the quantum dots are selected from one or more of blue quantum dots, red quantum dots and green quantum dots.
9. A quantum dot light-emitting device according to claim 1, wherein the core layer of the quantum dot is selected from one or more of CdSe, cdS, znSe, znS, cdTe, znTe, cdZnSe, cdZnTe, znSeS, znete, znTeS, cdSeS, cdSeTe, cdTeS, cdZnSeS, cdZnSeTe, cdSeSTe, znSeTe, cdznsette, inP, inAs, inAsP, pbS, pbSe, pbTe, pbSeS, pbSeTe, and PbSTe; and/or
The shell of the quantum dot is selected from one or more of CdSe, cdS, znSe, znS, cdTe, znTe, cdZnS, cdZnSe, cdZnTe, znSeS, znSeTe, znTeS, cdSeTe, cdTeS, cdZnSeS, cdZnSeTe, cdZnSTe, cdSeSTe, znSeTe, cdZnSeTe, inP, inAs, inAsP, pbS, pbSe, pbTe, pbSeS, pbSeTe and PbSTe.
10. The quantum dot light-emitting device according to claim 1, wherein a hole transport layer is further disposed between the first electrode layer and the quantum dot light-emitting layer, and/or
An electron transmission layer is arranged between the quantum dot light-emitting layer and the second electrode layer;
the material of the hole transport layer is selected from one or more of TFB, PVK, TCTA, TPD and CBP; the material of the electron transport layer is selected from ZnO and TiO 2 And SnO 2 One or more of them.
11. A display panel comprising a quantum dot light emitting device according to any of claims 1 to 10.
CN202111129846.1A 2021-09-26 2021-09-26 Quantum dot light-emitting device and display panel Pending CN115884615A (en)

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