CN108987594B - Organic electroluminescent diode and organic electroluminescent device - Google Patents
Organic electroluminescent diode and organic electroluminescent device Download PDFInfo
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Abstract
The invention discloses an organic light-emitting diode, which comprises a first electrode, a first carrier functional layer, at least two blue light emitting layers, a second carrier functional layer and a second electrode which are sequentially stacked; the blue light emitting layer comprises a phosphorescent light emitting layer close to the first carrier function layer and a fluorescent light emitting layer close to the second carrier function layer; the energy level barrier of the first carrier functional layer and the phosphorescent light-emitting layer is smaller than the energy level barrier of the second carrier functional layer and the fluorescent light-emitting layer, and the carrier mobility of the phosphorescent light-emitting layer is smaller than that of the fluorescent light-emitting layer. The organic electroluminescent diode emits blue phosphorescence from the phosphorescent light emitting layer at low voltage and emits blue fluorescence from the fluorescent light emitting layer at high voltage, thereby improving the light emitting efficiency. The invention provides an organic electroluminescent device, wherein the blue sub-pixel unit is the organic electroluminescent diode, so that the luminous efficiency of the device among the sub-pixel units under low voltage is balanced, and the color cast of the device is improved.
Description
Technical Field
The invention belongs to the technical field of display, and particularly relates to an organic electroluminescent diode and an organic electroluminescent device.
Background
An Organic Light Emitting diode (abbreviated as OLED) is an active Light Emitting Display device, and is expected to become a next generation of mainstream flat panel Display technology due to its advantages of simple preparation process, low cost, high contrast, wide viewing angle, low power consumption, and the like, and is one of the most concerned technologies in the flat panel Display technology at present.
Obtaining efficient monochrome display of three primary colors of red, green and blue is an indispensable part for realizing full-color display. Through research and development for more than twenty years, particularly, the discovery of phosphorescent materials enables the performance of red and green monochromatic organic electroluminescent devices to reach the standard of practical application, however, as the wavelength range of the absorption spectrum of blue light is short, the band gap of blue organic electroluminescent materials is wide, more energy needs to be obtained for the radiation luminescence of blue materials, the brightness, the efficiency and the service life of the blue devices are still poor, and the performance of the blue devices needs to be improved.
On the other hand, fig. 1 shows a voltage-luminance graph of RGB three-color sub-pixels in a conventional display device, and it can be seen from the graph that, in a conventional OLED display device, the lighting voltages of the RGB three-color sub-pixels are not uniform, specifically, the lighting voltage of the blue sub-pixel is greater than that of the green sub-pixel, and is greater than that of the red sub-pixel. In practical application, when the blue sub-pixel is lighted, although the voltage mainly spans the blue sub-pixel, because the conductivity of the common hole injection layer is better, a part of the voltage can be applied to the green sub-pixel and/or the red sub-pixel through the common hole injection layer, because the lighting voltages of the red sub-pixel and the green sub-pixel are both smaller than the lighting voltage of the blue sub-pixel, the red sub-pixel and/or the green sub-pixel are easy to be lighted simultaneously, that is, under the condition of low gray scale, the luminous brightness of the red sub-pixel and/or the green sub-pixel cannot reach the low-brightness display effect strictly according to the requirement, and the phenomenon of low gray scale color cast (red cast or green cast) occurs.
Disclosure of Invention
Therefore, the first technical problem to be solved by the present invention is the defect of low light emitting efficiency of the blue light device in the prior art.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the invention provides an organic light-emitting diode, which comprises a first electrode, a first carrier functional layer, at least two blue light emitting layers, a second carrier functional layer and a second electrode which are sequentially stacked; the blue light emitting layer comprises a phosphorescent light emitting layer arranged close to the first carrier function layer and a fluorescent light emitting layer arranged close to the second carrier function layer;
the energy level barrier between the first carrier functional layer and the main material of the phosphorescent light emitting layer is smaller than the energy level barrier between the second carrier functional layer and the main material of the fluorescent light emitting layer, and the carrier mobility of the phosphorescent light emitting layer is smaller than that of the fluorescent light emitting layer.
Preferably, in the organic electroluminescent diode, the first electrode is an anode, and the second electrode is a cathode; an energy level barrier Δ E between the HOMO level of the first carrier functional layer and the HOMO level of the phosphorescent light-emitting layer host materialh1An energy level barrier Δ E smaller than the LOMO energy level of the second carrier function and the LOMO energy level of the fluorescent light emitting layer host materiale1。
Further preferably, in the organic electroluminescent diode, the first carrier function layer is one of a hole injection layer, a hole transport layer and an electron blocking layer, and the second carrier function layer is one of an electron injection layer, an electron transport layer and a hole blocking layer.
Preferably, in the organic electroluminescent diode, the first carrier functional layer is an electron blocking layer, and the second carrier functional layer is a hole blocking layer.
Preferably, in the organic electroluminescent diode, the first electrode is a cathode, and the second electrode is an anode; an energy level barrier Δ E between the LUMO level of the first carrier function layer and the LUMO level of the host material of the phosphorescent light-emitting layere2An energy level barrier Δ E smaller than the HOMO level of the second carrier function and the HOMO level of the fluorescent light emitting layer host materialh2。
Further preferably, in the organic electroluminescent diode, the first carrier function layer is one of an electron injection layer, an electron transport layer and a hole blocking layer, and the second carrier function layer is one of a hole injection layer, a hole transport layer and an electron blocking layer.
Preferably, in the organic electroluminescent diode, the first carrier functional layer is a hole blocking layer, and the second carrier functional layer is an electron blocking layer.
Preferably, in the organic electroluminescent diode, a third carrier functional layer is further disposed between the first carrier functional layer and the first electrode; and/or a fourth carrier function layer is arranged between the second carrier function layer and the second electrode.
Preferably, in the above organic electroluminescent diode, the turn-on voltage of the phosphorescent light-emitting layer is lower than the turn-on voltage of the fluorescent light-emitting layer.
The second technical problem to be solved by the present invention is the defect that the OLED display device in the prior art is prone to color cast at low brightness.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the invention provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array mode, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit, and the blue sub-pixel unit is the organic electroluminescent diode.
The technical scheme of the invention has the following advantages:
1. the invention provides an organic electroluminescent diode, which comprises a first electrode, a first current carrier functional layer, at least two blue light emitting layers, a second current carrier functional layer and a second electrode which are arranged in a laminated manner; the blue light emitting layer comprises a phosphorescent light emitting layer arranged close to the first carrier function layer and a fluorescent light emitting layer arranged close to the second carrier function layer;
and the energy level barrier between the first carrier functional layer and the phosphorescent light-emitting layer is smaller than the energy level barrier between the second carrier functional layer and the fluorescent light-emitting layer main body material, and the carrier mobility of the phosphorescent light-emitting layer is smaller than that of the fluorescent light-emitting layer.
In the organic electroluminescent diode, the injection performance of carriers in the light emitting layer is determined by an energy level barrier between the light emitting layer and the adjacent carrier functional layer host material, and the carrier mobility in the carrier functional layer. The smaller the energy level potential barrier between the main material of the light emitting layer and the adjacent carrier functional layer is, the more favorable the carrier is injected into the light emitting layer; and at low voltage, the influence of the energy level barrier on the injection of the carriers is small, the injection proportion of different carriers (electrons and holes) into the light-emitting layer is relatively balanced, the influence effect of the energy level barrier on the injection of the carriers is increased along with the increase of voltage, and the injection difficulty of the carriers into the light-emitting layer can be obviously improved by the large energy level barrier at high voltage.
The organic light-emitting diode provided by the invention has the advantages that the carrier mobility of the phosphorescent light-emitting layer is smaller than that of the fluorescent light-emitting layer, the injection proportion of carriers from the first electrode and the second electrode into the blue light-emitting layer is relatively balanced at low voltage, more carriers from the second electrode in the fluorescent light-emitting layer are injected into the phosphorescent light-emitting layer due to the relatively high carrier mobility of the fluorescent light-emitting layer, and the carriers from the first electrode are compounded in the phosphorescent light-emitting layer, so that the organic light-emitting diode emits blue phosphorescence. In addition, the energy level barrier between the first carrier function layer and the phosphorescent light emitting layer host material is smaller than the energy level barrier between the second carrier function layer and the fluorescent light emitting layer host material, the difficulty of injecting carriers from the second electrode into the light emitting layer from the second carrier function layer is significantly increased at high voltage, the transport performance of carriers from the first electrode is higher than that of carriers from the second electrode, the carriers from the second electrode and the carriers from the first electrode are combined in the fluorescent light emitting layer near the second electrode, and the organic electroluminescent diode emits blue fluorescence. The organic light-emitting diode provided by the invention realizes phosphorescence light emission under low voltage by adjusting the position of carrier recombination under low voltage, and obviously improves the blue light luminous efficiency of the organic light-emitting diode under low voltage.
2. The organic electroluminescent diode provided by the invention has the advantages that the first electrode is an anode and generates holes, and the second electrode is a cathode and generates electrons. At low voltage, the injection ratio of electrons and holes into the light-emitting layer is balanced, more electrons in the fluorescent light-emitting layer are injected into the phosphorescent light-emitting layer due to high carrier mobility of the fluorescent light-emitting layer, the electrons and the holes are recombined in the phosphorescent light-emitting layer, and the device emits blue phosphorescence. At high voltage, Δ E due to energy level barriere1Larger, electron byThe difficulty of injecting the second carrier function into the light emitting layer is increased, the transmission performance of electrons is limited, the electrons and the holes are combined in the fluorescent light emitting layer close to the cathode, and the device emits blue fluorescence, so that the high light emitting efficiency of the device under low voltage is realized.
3. The organic electroluminescent diode provided by the invention has the advantages that the first electrode is the cathode and generates electrons, and the second electrode is the anode and generates holes. At low voltage, the injection proportion of electrons and holes into the light-emitting layer is balanced, and due to the high carrier mobility of the fluorescent light-emitting layer, more holes in the fluorescent light-emitting layer are injected into the phosphorescent light-emitting layer, so that the electrons and the holes are recombined in the phosphorescent light-emitting layer, and the device emits blue phosphorescence. At high voltage, Δ E due to energy level barrierh2The electron and the hole are combined in the fluorescent light-emitting layer close to the anode, and the device emits blue fluorescence, so that the high light-emitting efficiency of the device under low voltage is realized.
4. The organic electroluminescent device provided by the invention comprises a plurality of pixel units distributed in an array manner, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit, and the blue sub-pixel unit is the organic electroluminescent diode.
Because the wavelength of the absorption spectrum of blue light is short, the band gap between the HOMO level and the LUMO level of the blue light-emitting dye is wide, and higher energy is required for blue light emission, the light-emitting efficiency of a blue light sub-pixel unit is low under low voltage, the light-emitting efficiency of blue light, red light and green light of an organic electroluminescent device is unbalanced, color cast is easy to occur, and low gray scale is red.
According to the electromechanical electroluminescence device provided by the invention, the blue light emitting layer of the blue light sub-pixel unit is set as a double light emitting layer of the phosphorescence light emitting layer and the fluorescence light emitting layer, and the energy level barrier and the carrier mobility in the phosphorescence light emitting layer and the fluorescence light emitting layer are adjusted, so that the phosphorescence light emitting layer of the blue light sub-pixel unit emits light under low voltage, and the fluorescence light emitting layer of the blue light sub-pixel unit emits light under high voltage. The phosphorescent light-emitting layer has high luminous efficiency, so that the luminous efficiency among the three seed pixel units under low voltage is balanced, and the problem of color cast of the device is solved. Further, the blue fluorescent light-emitting material has stable light-emitting performance and a long light-emitting life, and the blue fluorescent light-emitting layer emits light at a high voltage to relatively maintain the color coordinates of the device, thereby improving color stability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a voltage-luminance graph of RGB three-color sub-pixels in a conventional full-color display device;
fig. 2 is a schematic structural diagram of an organic electroluminescent diode according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an organic electroluminescent diode according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an organic electroluminescent diode according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an organic electroluminescent diode according to an embodiment of the present invention;
description of reference numerals:
11-a first electrode, 12-a third carrier functional layer, 13-a first carrier functional layer, 14-a blue light emitting layer, 15-a second carrier functional layer, 16-a fourth carrier functional layer, 141-a phosphorescent light emitting layer, 142-a fluorescent light emitting layer.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. 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 invention.
In the description of the present invention, it should be noted that the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
This invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. It will be understood that when an element such as a layer is referred to as being "formed on" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly formed on" or "directly disposed on" another element, there are no intervening elements present.
According to a first technical solution, an embodiment of the present invention provides an organic electroluminescent diode, as shown in fig. 2, including a first electrode 11, a first carrier function layer 13, two blue light emitting layers 14, a second carrier function layer 15, and a second electrode 17, which are sequentially stacked. Among them, the two blue light emitting layers 14 are a phosphorescent light emitting layer 141 disposed adjacent to the first carrier function layer 13 and a fluorescent light emitting layer 142 disposed adjacent to the second carrier function layer 15, respectively. When the organic electroluminescent diode works, a certain driving voltage is applied, so that first carriers generated by the first electrode 11 are transmitted to the blue light emitting layer 14 through the first carrier functional layer 13; and is recombined with the second carriers from the second electrode 17 transported through the second carrier functional layer 15.
It should be noted that, since the wavelength of the absorption spectrum of blue light is short, the band gap between the HOMO level and the LUMO level of the blue light-emitting dye is wide, and higher energy is required for blue light emission, the light emission efficiency of the blue light-emitting device is low at low voltage.
In view of the above problem, in the present embodiment, the mobility of the first carrier functional layer 13 to the first carrier is set to be smaller than the mobility of the second carrier functional layer 15 to the second carrier, at a low voltage, the injection ratio of the first carrier and the second carrier into the blue light emitting layer 14 is relatively balanced, and since the carrier mobility of the fluorescent light emitting layer 142 is higher than that of the phosphorescent light emitting layer 141, the second carrier in the fluorescent light emitting layer 142 is more injected into the phosphorescent light emitting layer, and then is combined with the first carrier in the phosphorescent light emitting layer 141 to emit phosphorescence. Meanwhile, the energy level barrier between the first carrier function layer 13 and the host material of the phosphorescent light emitting layer 141 is smaller than the energy level barrier between the second carrier function layer 15 and the host material of the fluorescent light emitting layer 142, the energy level barrier between the carrier function layer and the host material of the light emitting layer has a large influence on the injection efficiency of carriers in the light emitting layer under high voltage, the injection difficulty of the second carriers into the blue light emitting layer 14 is obviously increased due to the high energy level barrier between the second carrier function layer 15 and the host material of the fluorescent light emitting layer 142, and the transmission performance of the first carrier function layer 13 is relatively better than that of the second carrier function layer 15, so that the first carriers and the second carriers are combined in the fluorescent light emitting layer 142 close to the second electrode 17 to emit fluorescence.
The organic electroluminescent diode in this embodiment realizes light emission from the phosphorescent light emitting layer 141 at a low voltage and light emission from the fluorescent light emitting layer 142 at a high voltage. Since the phosphorescent light emitting layer 141 emits light using triplet excitons, the light emitting efficiency thereof is higher than that of the fluorescent light emitting layer 142 emitting light using singlet excitons, so that the blue light diode has high light emitting efficiency at low voltage, and meanwhile, since the light emitting performance of fluorescent light emission is stable and the light emitting life is long, the color stability of the blue light diode at high voltage is high and the device life is long.
That is, the phosphorescent light emitting layer 141 has a relatively lower turn-on voltage than the fluorescent light emitting layer 142, and the phosphorescent light emitting layer 141 is turned on first at a low voltage, so that the defect of low light emitting efficiency of a blue light device at a low voltage is solved by virtue of high phosphorescent light emitting efficiency.
Specifically, the first electrode 11 may be an anodeThe second electrode 17 may be a cathode, and the first carrier functional layer 13 located between the anode and the phosphorescent light-emitting layer 141 is a hole-type carrier functional layer, and specifically may be a hole injection layer, a hole transport layer, or an electron blocking layer. The second carrier functional layer 15 located between the cathode and the fluorescent light-emitting layer 142 is a carrier functional layer of an electron type, and specifically may be an electron injection layer, an electron transport layer, or a hole blocking layer. The hole mobility of the first carrier functional layer 13 is smaller than the electron mobility of the second carrier functional layer 15, and at a low voltage, more electrons are injected into the phosphorescent light-emitting layer 141 in the fluorescent light-emitting layer 142, so that the electrons and holes are recombined in the phosphorescent light-emitting layer 141, and phosphorescent light emission is realized. Meanwhile, the energy level barrier Δ E between the HOMO level of the first carrier functional layer 13 and the HOMO level of the host material of the phosphorescent light-emitting layer 141h1An energy level barrier Δ E smaller than the LOMO energy level of the second carrier function and the LOMO energy level of the fluorescent light emitting layer 142 host materiale1. At high voltage, due to Delta Ee1Larger, blocks the transport of electrons to the blue light emitting layer 14, and allows the electrons and holes to recombine in the fluorescent light emitting layer 142 near the cathode to emit fluorescence. Therefore, the light emitting area of the organic light emitting diode is adjusted under different voltages, and the blue light emitting diode has high light emitting efficiency under low voltage.
As an alternative embodiment, the first electrode 11 may also be a cathode, the second electrode 17 may also be an anode, and the second carrier functional layer 15 located between the anode and the fluorescent light-emitting layer 142 is a hole-type carrier functional layer, and specifically may be a hole injection layer, a hole transport layer, or an electron blocking layer. The second carrier functional layer 15 located between the cathode and the phosphorescent light-emitting layer 141 is a carrier functional layer of an electron type, and specifically may be an electron injection layer, an electron transport layer, or a hole blocking layer. The electron mobility of the phosphorescent light-emitting layer 141 is smaller than the hole mobility of the fluorescent light-emitting layer 142, and at a low voltage, holes in the fluorescent light-emitting layer 142 are more injected into the phosphorescent light-emitting layer 141, so that electrons and holes are recombined in the phosphorescent light-emitting layer 141 near the cathode, and phosphorescent light emission is realized. At the same time, the LUMO level of the first carrier functional layer 13 and the host material of the phosphorescent light-emitting layer 141Energy level barrier Δ E of LUMO energy level of chargee2An energy level barrier Δ E between the HOMO level of the second carrier function and the HOMO level of the host material of the fluorescent light emitting layer 142h2. At high voltage, due to Delta Eh2Larger, blocking the transport of holes to the blue light-emitting layer 14, allowing electrons and holes to recombine in the fluorescent light-emitting layer 142 near the anode to emit fluorescence. Therefore, the light emitting area of the organic light emitting diode is adjusted under different voltages, and the blue light emitting diode has high light emitting efficiency under low voltage.
As a first alternative embodiment, as shown in fig. 3, a third carrier function layer 12 may be further provided between the first carrier function layer 13 and the first electrode 11. For example, the first electrode 11 is an anode, the first carrier functional layer 13 is an electron blocking layer, and the third carrier functional layer 12 may be provided as a hole injection layer, a hole transport layer, or a stack of a hole injection layer and a hole transport layer. Alternatively, the first carrier functional layer 13 is a hole transport layer, and the third carrier functional layer 12 is provided as a hole injection layer. As long as the carrier mobility of the phosphorescent light-emitting layer 141 is smaller than that of the fluorescent light-emitting layer 142, it is ensured that the two carriers can emit light at the position of the phosphorescent light-emitting layer 141 in a combined manner at a low voltage.
As a variation of the first alternative embodiment, the first electrode 11 is a cathode, the first carrier functional layer 13 is a hole blocking layer, and the third carrier functional layer 12 may be provided as an electron injection layer, an electron transport layer, or a stack of an electron injection layer and an electron transport layer. Alternatively, the first carrier functional layer 13 is an electron transport layer, and the third carrier functional layer 12 is provided as an electron injection layer.
As a second alternative embodiment, as shown in fig. 4, a fourth carrier function layer 16 may be further provided between the second carrier function layer 15 and the second electrode 17. For example, the second electrode 17 is a cathode, the second carrier functional layer 15 is a hole blocking layer, and the fourth carrier functional layer 16 may be provided as an electron injection layer, an electron transport layer, or a stack of an electron injection layer and an electron transport layer. Alternatively, the second carrier functional layer 15 is an electron transport layer, and the fourth carrier functional layer 16 is provided as an electron injection layer. As long as the carrier mobility of the phosphorescent light-emitting layer 141 is smaller than that of the fluorescent light-emitting layer 142, the two carriers can be ensured to emit light at the position of the phosphorescent light-emitting layer 141 in a composite manner under low voltage; the energy level barrier between the first carrier function layer 13 and the host material of the phosphorescent light emitting layer 141 is smaller than the energy level barrier between the second carrier function layer 15 and the host material of the fluorescent light emitting layer 142, so that the two carriers can emit light at the position of the fluorescent light emitting layer 142 in a combined manner under high voltage.
As a variation of the second alternative embodiment, the second electrode 17 is an anode, the second carrier functional layer 15 is an electron blocking layer, and the fourth carrier functional layer 16 may be provided as a hole injection layer, a hole transport layer, or a stack of a hole injection layer and a hole transport layer. Alternatively, the second carrier functional layer 15 is a hole transport layer, and the fourth carrier functional layer 16 is provided as a hole injection layer.
As a third alternative embodiment, as shown in fig. 5, it is also possible to provide a fourth carrier functional layer 16 between the second carrier functional layer 15 and the second electrode 17, and a third carrier functional layer 12 between the first carrier functional layer 13 and the first electrode 11. For example, the first electrode 11 is an anode, the first carrier functional layer 13 is an electron blocking layer, and the third carrier functional layer 12 may be provided as a hole injection layer, a hole transport layer, or a stack of a hole injection layer and a hole transport layer. The second electrode 17 is a cathode, the second carrier functional layer 15 is a hole blocking layer, and the fourth carrier functional layer 16 may be provided as an electron injection layer, an electron transport layer, or a stack of an electron injection layer and an electron transport layer. Alternatively, the first carrier functional layer 13 is a hole transport layer, and the third carrier functional layer 12 is provided as a hole injection layer. The second carrier functional layer 15 is an electron transport layer, and the fourth carrier functional layer 16 is provided as an electron injection layer. As long as the carrier mobility of the phosphorescent light-emitting layer 141 is smaller than that of the fluorescent light-emitting layer 142, the two carriers can be ensured to emit light at the position of the phosphorescent light-emitting layer 141 in a composite manner under low voltage; the energy level barrier between the first carrier function layer 13 and the host material of the phosphorescent light emitting layer 141 is smaller than the energy level barrier between the second carrier function layer 15 and the host material of the fluorescent light emitting layer 142, so that the two carriers can emit light at the position of the fluorescent light emitting layer 142 in a combined manner under high voltage.
As a variation of the third alternative embodiment, the first electrode 11 is a cathode, the first carrier functional layer 13 is a hole blocking layer, and the third carrier functional layer 12 may be provided as an electron injection layer, an electron transport layer, or a stack of an electron injection layer and an electron transport layer. The second electrode 17 is an anode, the second carrier functional layer 15 is an electron blocking layer, and the fourth carrier functional layer 16 may be provided as a hole injection layer, a hole transport layer, or a stack of a hole injection layer and a hole transport layer. Alternatively, the first carrier functional layer 13 is an electron transport layer, and the third carrier functional layer 12 is provided as an electron injection layer. The second carrier functional layer 15 is a hole transport layer, and the fourth carrier functional layer 16 is provided as a hole injection layer.
According to a second embodiment, the embodiment of the present invention provides an organic electroluminescent device, including a plurality of pixel units arranged in an array, each pixel unit includes a red sub-pixel unit, a green sub-pixel unit, and a blue sub-pixel unit, and each sub-pixel unit of different light-emitting colors includes a first electrode 11, a light-emitting layer, at least one carrier functional layer, and a second electrode 17, which are stacked. The light emitting layers in each sub-pixel unit are a red light emitting layer, a green light emitting layer, and a blue light emitting layer 14, respectively.
In the organic electroluminescent device, the wavelengths of red light, green light, and blue light are gradually shorter, and the energy is gradually higher. Therefore, the starting voltage of the red sub-pixel unit is lower than that of the green sub-pixel unit and that of the blue sub-pixel unit, and when the blue sub-pixel unit is independently lighted at low voltage, the red sub-pixel unit is easily lighted at the same time; when the blue sub-pixel unit and the red sub-pixel unit are simultaneously lightened, the luminous efficiency of the blue sub-pixel unit is obviously lower than that of the red sub-pixel unit, and the problem of low gray scale color cast is caused.
In order to solve the above problem, an organic electroluminescent device according to an embodiment of the present invention is provided, in which a blue sub-pixel unit is provided as the organic electroluminescent diode according to any one of the embodiments of the present invention.
For example, the blue sub-pixel unit has a first electrode 11 (anode), a second electrode 17 (cathode), and a first carrier functional layer 13 between the anode and the phosphorescent light-emitting layer 141 is a hole type carrier functional layer, specifically a hole injection layer, a hole transport layer, or an electron blocking layer. The second carrier functional layer 15 located between the cathode and the fluorescent light-emitting layer 142 is a carrier functional layer of an electron type, and specifically may be an electron injection layer, an electron transport layer, or a hole blocking layer. The hole mobility of the phosphorescent light-emitting layer 141 is smaller than the electron mobility of the fluorescent light-emitting layer 142, and at a low voltage, the injection ratio of the holes from the anode and the electrons from the cathode into the blue light-emitting layer is relatively balanced, and because the electron mobility in the fluorescent light-emitting layer 142 is high, more electrons are injected into the phosphorescent light-emitting layer 141, and the electrons and the holes are combined in the phosphorescent light-emitting layer 141, so that phosphorescent light emission is realized. Meanwhile, the energy level barrier Δ E between the HOMO level of the first carrier functional layer 13 and the HOMO level of the host material of the phosphorescent light-emitting layer 141h1An energy level barrier Δ E smaller than the LOMO energy level of the second carrier function and the LOMO energy level of the fluorescent light emitting layer 142 host materiale1. At high voltage, due to Delta Ee1Larger, blocks the transport of electrons to the blue light emitting layer 14, and allows the electrons and holes to recombine in the fluorescent light emitting layer 142 near the cathode to emit fluorescence. Therefore, the light emitting area of the organic light emitting diode is adjusted under different voltages, and the blue light emitting diode has high light emitting efficiency under low voltage.
That is, in the organic electroluminescent device in the embodiment, the fluorescent light emitting layer 142 and the phosphorescent light emitting layer 141 are disposed in the blue sub-pixel unit, and the lighting voltage of the phosphorescent light emitting layer 141 is lower than the lighting voltage of the fluorescent light emitting layer 142, and the phosphorescent light emitting layer 141 in the blue sub-pixel unit is lit at a low voltage.
As a modified embodiment, the blue sub-pixel unit may also be any other organic electroluminescent diode provided in the first technical aspect of the present invention.
As an alternative embodiment, the red sub-pixel unit and the green sub-pixel unit in the organic electroluminescent device may also be any organic electroluminescent diode having any structure disclosed in the prior art, as long as the red sub-pixel unit can emit red light and the green sub-pixel unit can emit green light, and the structure is not particularly limited herein.
Example 1
The present embodiment provides a specific example of an organic electroluminescent diode, which includes a first electrode 11, a third carrier functional layer 12, a first carrier functional layer 13, two blue light emitting layers 14, a second carrier functional layer 15, a fourth carrier functional layer 16, and a second electrode 17, which are sequentially stacked.
The first electrode 11 is an anode, the third carrier functional layer 12 is a hole injection layer and a hole transport layer which are stacked, the first carrier functional layer 13 is an electron blocking layer, the two blue light emitting layers 14 are a phosphorescent light emitting layer 141 close to the first electrode 11 and a fluorescent light emitting layer 142 close to the second electrode 17, respectively, the second carrier functional layer 15 is a hole blocking layer, the fourth carrier functional layer 16 is a stack of an electron transport layer and an electron injection layer, and the second electrode 17 is a cathode.
In the organic electroluminescent diode,. DELTA.Eh1Is 0eV,. DELTA.Ee10.17 eV; the phosphorescent layer 141 is made of phosphorescent material, specifically TCTA: FIrpic (5%, 20nm), and has hole mobility of 5.2e-4cm2V/s; the fluorescent light-emitting layer 142 is made of a fluorescent material, specifically TmPyPb: DSA-Ph (5%, 20nm), and has an electron mobility of 1.1e-3cm2/V/s。
The device structure of the organic electroluminescent diode in this embodiment is: ITO (10nm)/Ag (100nm)/ITO (10nm)/HATCN (5nm)/m-MTDATA (20nm)/TCTA (200nm)/TCTA FIrpic (5%, 20nm)/TmPyPb (5%, 20 nm)/DSA-Ph (5%, 20nm)/BPhen (5nm)/T mPyPb (40nm)/LiF (1nm)/Mg: Ag (20%, 15nm)/NPB (60 nm).
Example 2
This example provides an organic electroluminescent diode that is substantially the same as the organic electroluminescent diode described in example 1, with the only difference that:
in the organic electroluminescent diode,. DELTA.Eh1Is 0eV,. DELTA.Ee1Is 0.2 eV; the phosphorescent layer 141 is made of phosphorescent material, specifically TCTA: FIrpic (5%, 20nm), and has hole mobility of 5.2e-4cm2V/s; the fluorescent light-emitting layer 142 is made of a fluorescent material, specifically TPBi: DSA-Ph (5%, 20nm), and has an electron mobility of 8.2e-4cm2/V/s。
The device structure of the organic electroluminescent diode in this embodiment is: ITO (10nm)/Ag (100nm)/ITO (10nm)/HATCN (5nm)/m-MTDATA (20nm)/TCTA (200nm)/TCTA FIrpic (5%, 20nm)/TPBi DSA-Ph (5%, 20nm)/BPhen (5nm)/TmPy Pb (40nm)/LiF (1nm)/Mg: Ag (20%, 15nm)/NPB (60 nm).
Example 3
This example provides an organic electroluminescent diode that is substantially the same as the organic electroluminescent diode described in example 1, with the only difference that:
the third carrier functional layer 12 is not provided, and the fourth carrier functional layer 16 is an electron injection layer.
The device structure of the organic electroluminescent diode in this embodiment is: ITO (10nm)/Ag (100nm)/ITO (10nm)/TCTA (300nm)/TCTA FIrpic (5%, 20nm)/T mPyPb DSA-Ph (5%, 20nm)/BPhen (5nm)/TmPyPb (40nm)/Mg: Ag (20%, 15nm)/N PB (60 nm).
Example 7
The embodiment provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit. The blue sub-pixel unit is the organic electroluminescent diode in embodiment 1.
The structure of the red sub-pixel unit is ITO (10nm)/Ag (100nm)/ITO (10nm)/HATCN (5nm)/α -NPD (20nm)/TCTA (200n m)/CZPPQCz Ir (piq)3(3％,30nm)/TmPyPb(40nm)/LiF(1nm)/Mg:Ag(20％,15nm)/NPB(60nm)。
The green sub-pixel unit has the structure of ITO (10nm)/Ag (100nm)/ITO (10nm)/HATCN (5nm)/m-MTDATA (20nm)/α -NPD (200nm)/TCTA Ir (ppy)3(8％,30nm)/BAlq(40nm)/LiF(1nm)/Mg:Ag(20％,15nm)/NPB(60nm)。
Example 8
The embodiment provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit. The blue sub-pixel unit is the organic electroluminescent diode in embodiment 2.
The device structure of the red sub-pixel unit and the green sub-pixel unit is the same as that of embodiment 7.
Example 9
The embodiment provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit. The blue sub-pixel unit is the organic electroluminescent diode in embodiment 3.
The device structure of the red sub-pixel unit and the green sub-pixel unit is the same as that of embodiment 7.
Comparative example 1
This comparative example provides an organic electroluminescent diode which is substantially the same as the organic electroluminescent diode described in example 1, with the only difference that:
the blue light emitting layer 14 is only a phosphorescent light emitting layer 141.
Comparative example 2
This comparative example provides an organic electroluminescent diode which is substantially the same as the organic electroluminescent diode described in example 1, with the only difference that:
in the organic electroluminescent diode,. DELTA.Eh1Is 0.1eV,. DELTA.Ee1Is 0 eV; the phosphorescent layer 141 is made of phosphorescent material, specifically TAPC (5%, 20nm), and has hole mobility of 6.1e-3cm2V/s; the fluorescent light-emitting layer 142 is made of fluorescent materialThe optical material, specifically TPBi: DSA-Ph (5%, 20nm), has an electron mobility of 8.2e-4cm2/V/s。
The device structure of the organic electroluminescent diode in this embodiment is: ITO (10nm)/Ag (100nm)/ITO (10nm)/HATCN (5nm)/m-MTDATA (20nm)/TPD (200nm)/TAPC: FIrpic (5%, 20nm)/TPBi: DSA-Ph (5%, 20nm)/TPBi (5nm)/TmPyPb (40nm)/LiF (1nm)/Mg: Ag (20%, 15nm)/NPB (60 nm).
Comparative example 3
This comparative example provides an organic electroluminescent diode which is substantially the same as the organic electroluminescent diode described in example 5, with the only difference that:
the blue light emitting layer 14 is only a phosphorescent light emitting layer 141.
Comparative example 5
The embodiment provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit. Wherein, the blue sub-pixel unit is the organic electroluminescent diode in comparative example 1.
The device structure of the red sub-pixel unit and the green sub-pixel unit is the same as that of embodiment 7.
Comparative example 6
The embodiment provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit. Wherein, the blue sub-pixel unit is the organic electroluminescent diode in the comparative example 2.
The device structure of the red sub-pixel unit and the green sub-pixel unit is the same as that of embodiment 7.
Comparative example 7
The embodiment provides an organic electroluminescent device which comprises a plurality of pixel units distributed in an array, wherein each pixel unit comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit. Wherein, the blue sub-pixel unit is the organic electroluminescent diode in comparative example 3.
The device structure of the red sub-pixel unit and the green sub-pixel unit is the same as that of embodiment 7.
Example of detection
The above examples 7 to 9 and comparative examples 5 to 7 were tested and the test results were compared as shown in the following table:
as can be seen from the data in the above table, the organic electroluminescent diode provided by the present invention has the advantages that by providing the double blue light emitting layers of the phosphorescent light emitting layer and the fluorescent light emitting layer, and adjusting the energy level barriers between the phosphorescent light emitting layer and the fluorescent light emitting layer and the adjacent carrier functional layer, and the carrier mobility in the two light emitting layers, the composite position of the carriers in the diode is migrated along with the change of voltage, so that the phosphorescent light emitting at low voltage and the phosphorescent light emitting at high voltage are realized, and the light emitting efficiency of the blue light device is effectively improved. In the organic electroluminescent device formed by applying the blue light device, the luminous efficiency of the blue light sub-pixel unit under low brightness is improved, and the low gray scale color cast of the device is effectively improved.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (11)
1. An organic light-emitting diode is characterized by comprising a first electrode, a first current carrier functional layer, at least two blue light emitting layers, a second current carrier functional layer and a second electrode which are sequentially stacked; the blue light emitting layer comprises a phosphorescent light emitting layer arranged close to the first carrier function layer and a fluorescent light emitting layer arranged close to the second carrier function layer;
the first electrode is an anode and the second electrode is a cathodeThe electrode is a cathode; the first current carrier functional layer is a hole type current carrier functional layer, and the second current carrier functional layer is an electron type current carrier functional layer; an energy level barrier Δ E between the HOMO level of the first carrier functional layer and the HOMO level of the phosphorescent light-emitting layer host materialh1An energy level barrier Δ E smaller than the LUMO energy level of the second carrier function layer and the LUMO energy level of the fluorescent light emitting layer host materiale1；
The hole mobility of the phosphorescent light-emitting layer is smaller than the electron mobility of the fluorescent light-emitting layer.
2. The organic electroluminescent diode of claim 1, wherein the first carrier functional layer is one of a hole injection layer, a hole transport layer and an electron blocking layer, and the second carrier functional layer is one of an electron injection layer, an electron transport layer and a hole blocking layer.
3. The organic electroluminescent diode according to claim 1 or 2, wherein the first carrier functional layer is an electron blocking layer and the second carrier functional layer is a hole blocking layer.
4. The organic electroluminescent diode according to claim 1 or 2, wherein a third carrier functional layer is further provided between the first carrier functional layer and the first electrode; and/or a fourth carrier function layer is arranged between the second carrier function layer and the second electrode.
5. The organic electroluminescent diode according to claim 1 or 2, wherein an on-voltage of the phosphorescent light emitting layer is lower than an on-voltage of the fluorescent light emitting layer.
6. An organic light-emitting diode is characterized by comprising a first electrode, a first current carrier functional layer, at least two blue light emitting layers, a second current carrier functional layer and a second electrode which are sequentially stacked; the blue light emitting layer comprises a phosphorescent light emitting layer arranged close to the first carrier function layer and a fluorescent light emitting layer arranged close to the second carrier function layer;
the first electrode is a cathode, and the second electrode is an anode; the first carrier functional layer is an electronic carrier functional layer, and the second carrier functional layer is a hole type carrier functional layer; an energy level barrier Δ E between the LUMO level of the first carrier function layer and the LUMO level of the host material of the phosphorescent light-emitting layere2An energy level barrier Δ E smaller than the HOMO level of the second carrier functional layer and the HOMO level of the fluorescent light emitting layer host materialh2；
The electron mobility of the phosphorescent light-emitting layer is smaller than the hole mobility of the fluorescent light-emitting layer.
7. The organic electroluminescent diode of claim 6, wherein the first carrier functional layer is one of an electron injection layer, an electron transport layer, and a hole blocking layer, and the second carrier functional layer is one of a hole injection layer, a hole transport layer, and an electron blocking layer.
8. The organic electroluminescent diode according to claim 6 or 7, wherein the first carrier functional layer is a hole blocking layer and the second carrier functional layer is an electron blocking layer.
9. The organic electroluminescent diode according to claim 6 or 7, wherein a third carrier functional layer is further provided between the first carrier functional layer and the first electrode; and/or a fourth carrier function layer is arranged between the second carrier function layer and the second electrode.
10. The organic electroluminescent diode according to claim 6 or 7, wherein an on-voltage of the phosphorescent light emitting layer is lower than an on-voltage of the fluorescent light emitting layer.
11. An organic electroluminescent device, comprising a plurality of pixel units distributed in an array, wherein the pixel units comprise a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit, and the blue sub-pixel unit is the organic electroluminescent diode according to any one of claims 1 to 5 or the organic electroluminescent diode according to any one of claims 6 to 10.
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