CN108717956B - Organic light emitting display panel and display device thereof - Google Patents
Organic light emitting display panel and display device thereof Download PDFInfo
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- CN108717956B CN108717956B CN201810551640.XA CN201810551640A CN108717956B CN 108717956 B CN108717956 B CN 108717956B CN 201810551640 A CN201810551640 A CN 201810551640A CN 108717956 B CN108717956 B CN 108717956B
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- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
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Abstract
The invention provides an organic light-emitting display panel and a display device, relates to the technical field of display, and aims to improve the injection capability and the migration capability of electrons. The organic light emitting display panel comprises an array substrate, wherein the array substrate comprises a plurality of driving elements; an organic light emitting device disposed corresponding to the driving element, the organic light emitting device including an anode and a cathode, and an organic functional layer between the anode and the cathode, the organic functional layer including an organic light emitting layer, and a first electron transport layer between the cathode and the organic light emitting layer; wherein the first electron transport layer comprises an electron transport matrix and a first dopant, the first dopant comprises a lanthanide, and the first dopant has a work function less than that of the cathode; the melting point range of the first dopant is 750-900 ℃, the boiling point is lower than 2300 ℃, and the doping percentage of the first dopant in the first electron transport layer is as follows: 0.5 to 7 percent. The organic light emitting display panel is suitable for the field of display devices.
Description
Technical Field
The invention relates to the technical field of display, in particular to an organic light-emitting display panel and a display device thereof.
Background
In recent years, with the continuous development of display technologies, various display devices, such as liquid crystal display devices, organic light emitting display devices, etc., have become mainstream products of display industries at present, wherein an organic light emitting display panel becomes a mainstream trend of development of display industries due to a series of excellent performances, such as lightness, thinness, low power consumption, high brightness, high contrast, high resolution, wide viewing angle, etc., and is a hot spot of controversial research in the current display field.
An important component of the organic light emitting display panel is an organic light emitting diode that emits light by driving a light emitting layer located between an anode and a cathode by an electric field applied between the anode and the cathode. In the prior art, the insufficient injection capability and migration capability of electrons may cause the recombination center of holes and electrons to deviate from the light-emitting layer, which results in the decrease of the light-emitting efficiency of the light-emitting layer, and therefore, how to further improve the injection capability and migration capability of electrons in the organic light-emitting diode, so that the recombination center of holes and electrons does not deviate, thereby improving the performance of the organic light-emitting device is a problem to be solved urgently in the field.
Disclosure of Invention
Embodiments of the present invention provide an organic light emitting display panel and a display device thereof, which are used to improve electron injection capability and mobility.
An aspect of an embodiment of the present invention provides an organic light emitting display panel including:
an array substrate including a plurality of driving elements;
an organic light emitting device provided corresponding to the driving element, the organic light emitting device including an anode and a cathode, and an organic functional layer between the anode and the cathode, the organic functional layer including an organic light emitting layer, and a first electron transport layer between the cathode and the organic light emitting layer;
wherein the first electron transport layer comprises an electron transport matrix and a first dopant, the first dopant comprises a lanthanide, and the first dopant has a work function that is less than the work function of the cathode;
the melting point range of the first dopant is 750-900 ℃, the boiling point is lower than 2300 ℃, and the doping percentage of the first dopant in the first electron transport layer is as follows: 0.5 to 7 percent.
Another aspect of embodiments of the present invention provides an organic light emitting display device including the organic light emitting display panel according to the previous aspect of the present invention.
The beneficial effects of the aspects and any possible implementation described above are as follows:
in this embodiment, a first electron transport layer is disposed between the cathode and the organic light emitting layer, the first electron transport layer includes a first dopant, and the first dopant includes a lanthanide metal element, so that a migration rate of electrons generated by the cathode to the organic light emitting layer can be increased, an injection barrier can be reduced, and the electrons can be transferred to the first electron transport layer. And after negative bias is applied to the cathode, the electron carriers overcome the potential barrier and migrate to the organic light-emitting layer towards a low energy level, and the work function of the first doping agent is smaller than that of the cathode, so that the electron carriers are favorably migrated from the cathode to the first electron transport layer. Because the first dopant comprises lanthanide metal elements, when the first dopant accounts for a higher volume percentage of the first electron transport layer, the first dopant converges in the first electron transport layer to generate black spots, which affects the light transmittance of the first electron transport layer and also reduces the yield of products. In addition, when the first dopant occupies a lower volume percentage of the first electron transport layer, the migration of electron carriers is affected, and in this embodiment, in order to balance the electron carrier transport efficiency and the light transmittance of the first electron transport layer, the doping percentage of the first dopant in the first electron transport layer is set to be between 0.5% and 7%. In addition, the melting point range of the first dopant is set to be 750-900 ℃, the boiling point is lower than 2300 ℃, the preparation process is facilitated, and illustratively, when the first dopant is evaporated into the first electron transport layer by using an evaporation process, the melting point and the boiling point are relatively low, so that the formed film layer structure and the organic material serving as a dopant host are not damaged.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an organic light emitting display panel according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an organic light emitting display panel according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an organic light emitting display panel according to an embodiment of the present invention;
FIG. 4 is a cross-sectional view of the organic light emitting device at position AA' of FIG. 3 according to an embodiment of the present invention;
FIG. 5 is another cross-sectional view of the organic light emitting device at position AA' of FIG. 3 according to an embodiment of the present invention;
FIG. 6 is another cross-sectional view of the organic light emitting device at position AA' of FIG. 3 according to an embodiment of the present invention;
FIG. 7 is another cross-sectional view of the organic light emitting device at position AA' of FIG. 3 according to an embodiment of the present invention;
FIG. 8 is another cross-sectional view of the organic light emitting device at position AA' of FIG. 3 according to an embodiment of the present invention;
FIG. 9 is another cross-sectional view of the organic light emitting device at position AA' of FIG. 3 according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of an organic light emitting display device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious 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.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, third, etc. may be used to describe the electron transport layers in the embodiments of the present invention, the electron transport layers should not be limited to these terms. These terms are only used to distinguish the electron transport layers from each other. For example, a first electron transport layer may also be referred to as a second electron transport layer, and similarly, a third electron transport layer may also be referred to as a first electron transport layer without departing from the scope of embodiments of the present invention.
It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element.
Before the present embodiment is described in detail, the structure of the organic light emitting display panel and the technical spirit of the present invention will be briefly described:
as shown in fig. 1, a schematic structural diagram of an organic light emitting display panel according to an embodiment of the present invention provides an organic light emitting display panel, where the organic light emitting display panel 1 includes an array substrate 10, the array substrate includes a plurality of driving elements (not shown in the figure), the organic light emitting display panel 1 further includes organic light emitting devices 11 corresponding to the driving elements, and each organic light emitting device 11 includes an anode 12, a cathode 14, and an organic functional layer 13 disposed between the anode 12 and the cathode 14.
It is understood that the anode 12 is in contact with a side surface of the array substrate 10, and the cathode 14 is located on a side surface of the organic functional layer 13 facing away from the array substrate 10.
Inevitably, the array substrate 10 in this embodiment may be a flexible substrate, and the corresponding organic light emitting display panel 1 may be a flexible organic light emitting display panel, which has special effects of low power consumption and being bendable, and is suitable for various display devices, especially for wearable display devices. Optionally, the flexible substrate is made of polyester imide or polyethylene terephthalate resin. In addition, the array substrate 10 may also be a rigid substrate, and the corresponding organic light emitting display panel 1 is a rigid organic light emitting display panel. In fact, the material of the organic light emitting display panel is not particularly limited in this embodiment.
In this embodiment a positive voltage is applied to the anode 12 during electroluminescence. The material of the anode 12 in this embodiment may be indium tin oxide. Specifically, the anode 12 includes at least a reflective film, which may be on a surface of the anode 12 facing away from the array substrate 10, and the material of the reflective film may be silver. The anode 12 may further include a transparent conductive film on a surface of the reflective film facing away from the array substrate 10, and the transparent conductive film may be made of indium tin oxide or indium zinc oxide.
In this embodiment, a negative voltage may be applied to the cathode 14 during electroluminescence. In order to improve the injection capability of electron carriers from the cathode 14 into the organic functional layer 13, the material of the cathode 14 may be Ag, Al, Ca, In, Li, Mg, or other low work function metal material or low work function composite metal material.
As shown in fig. 2, which is a schematic diagram of the principle of the organic light emitting display panel according to the embodiment of the present invention, under the action of an external electric field, electrons e are injected from the cathode 14 into the organic functional layer 13, and holes h are injected from the anode 12 into the organic functional layer 13. The injected electrons e and the injected holes h generate excitons upon recombination of the organic light emitting layer 131. The excitons migrate under the action of the electric field, transferring energy to the organic light emitting molecules in the organic light emitting layer 131, electrons of the organic light emitting molecules transition from a ground state to an excited state and release energy, and finally the energy is released in the form of photons and emits light.
In the prior art, the transfer efficiency and injection efficiency of electron carriers from a cathode to an organic light emitting layer are low, and the light emitting efficiency of an organic light emitting display panel is further influenced.
In order to solve the above problems and improve the injection efficiency and the migration efficiency of the electron carriers, the inventors propose the following technical solutions:
the present invention provides an organic light emitting display panel, as shown in fig. 3 and 4, fig. 3 is another schematic structural diagram of an organic light emitting display panel provided by an embodiment of the present invention, fig. 4 is a cross-sectional view of an organic light emitting device at position AA' in fig. 3 provided by an embodiment of the present invention, as shown in fig. 3, the organic light emitting display panel 1 includes an array substrate 10, the array substrate 10 includes a plurality of driving elements 101, and in fig. 3, the organic light emitting device 11 is set to have a transparency of 60% so as to see the driving elements 101 covered thereby, in order to exemplarily show a relationship between the driving elements and the organic light emitting device.
Referring to fig. 4, the organic light emitting display panel 1 further includes an organic light emitting device 11 disposed corresponding to the driving element 101, the organic light emitting device 11 including an anode 12 and a cathode 14, and an organic functional layer 13 disposed between the anode 12 and the cathode 14, the organic functional layer 13 including an organic light emitting layer 131, and a first electron transport layer 132 disposed between the cathode 14 and the organic light emitting layer 131, the first electron transport layer 132 including a first dopant 1321, the first dopant 1321 including a lanthanide.
And, the work function of the first dopant 1321 is smaller than that of the cathode 14; the melting point of the first dopant 1321 ranges from 750 ℃ to 900 ℃, the boiling point is below 2300 ℃, and the doping percentage of the first dopant 1321 in the first electron transport layer 132 is: 0.5 to 7 percent.
In this embodiment, the first electron transport layer 132 is disposed between the cathode 14 and the organic light emitting layer 131, the first electron transport layer 132 includes the first dopant 1321, and the first dopant 1321 includes the lanthanide, so that the mobility rate of electrons generated by the cathode 14 to the organic light emitting layer 131 can be increased, the injection barrier can be reduced, and the electrons can be transferred to the first electron transport layer 132. And, after applying a negative bias to the cathode, the electron carriers migrate toward the organic light emitting layer 131 toward a low energy level against the potential barrier, and the work function of the first dopant 1321 is smaller than that of the cathode 14, facilitating the migration of the electron carriers from the cathode 14 to the first electron transport layer 132.
Since the first dopant 1321 includes the lanthanide, when the lanthanide occupies a higher volume percentage of the first electron transport layer 1321, the first dopant 1321 may converge in the first electron transport layer 132 to generate black spots, which may affect the light transmittance of the first electron transport layer 132 and may reduce the yield of the product. Also, when the first dopant 1321 occupies a low volume percentage of the first electron transit layer 1321, it affects the migration of electron carriers, and in this embodiment, in order to balance the electron carrier transit efficiency and the light transmittance of the first electron transit layer 132, the doping percentage of the first dopant 1321 in the first electron transit layer 132 is set to be between 0.5% and 7%.
In addition, the melting point range of the first dopant is set to be 750-900 ℃, the boiling point is lower than 2300 ℃, which is beneficial to process preparation, and exemplarily, when the first dopant is evaporated into the first electron transport layer by using an evaporation process, the melting point and the boiling point are relatively low, so that the formed film layer structure cannot be damaged.
In one embodiment, the melting or sublimation point of the electron transport matrix in the first electron transport layer 132 is 150-430 ℃ with a boiling point <500 ℃; the melting point or sublimation point of the organic light emitting layer 131 is 150-450 ℃, and the boiling point is <550 ℃.
In this embodiment, the melting point or sublimation point and the boiling point of the electron transport matrix in the first electron transport layer 132 are limited, so as to ensure that other organic film layers in the organic light emitting device 11 are not lost in the preparation process, thereby improving the yield.
Moreover, the melting point or sublimation point of the electron transport matrix of the first electron transport layer is close to the melting point or sublimation point of the organic light emitting layer 131, so that the two layers have equivalent heat resistance, the same preparation environment is achieved, and the process is facilitated to be realized.
It is emphasized that the numerical values referred to in this example include the end points.
In one embodiment, as shown in fig. 5, which is another cross-sectional view of the organic light emitting device at the AA' position in fig. 3 provided in the embodiment of the present invention, the organic functional layer 13 further includes a second electron transport layer located between the first electron transport layer 132 and the organic light emitting layer 131, the second electron transport layer 133 is not doped with the first dopant, and the highest occupied orbital level HOMO2 of the electron transport matrix in the second electron transport layer 133 and the highest occupied orbital level HOMO3 of the host material of the organic light emitting layer 131 satisfy: i HOMO2-HOMO3| <1 eV.
In this embodiment, after the highest occupied orbital level HOMO2 of the second electron transport layer 133 and the highest occupied orbital level HOMO3 of the host material of the organic light emitting layer 131 satisfy the above relationship, the function of suppressing the hole carriers from migrating from the cathode to the organic light emitting layer can be achieved, and meanwhile, the phenomenon that the electron carriers are recombined with the hole carriers without being transported to the organic light emitting layer and the light emitting efficiency is affected is avoided.
In addition, since the second electron transport layer 133 does not contain the first dopant 1321, the first dopant 1321 can be effectively blocked from diffusing into the organic light emitting layer 131, so that the absorption of photons generated by the recombination of electrons and holes is avoided, and the light emitting efficiency of the organic light emitting display panel is ensured.
Note that, in order to avoid the case where the value of the highest occupied orbital level HOMO2 of the electron-transporting host in the second electron-transporting layer 133 is positive, the value of the highest occupied orbital level HOMO4 of the host material of the organic light-emitting layer 131 is negative, or the value of the highest occupied orbital level HOMO2 of the electron-transporting host in the second electron-transporting layer 133 is negative, and the value of the highest occupied orbital level HOMO4 of the host material of the organic light-emitting layer 131 is positive, which is not favorable for comparison between the two, the present embodiment compares the two relative values. Illustratively, the highest occupied orbital level HOMO2 of the electron-transporting host in the second electron-transporting layer 133 is 6eV, and the highest occupied orbital level HOMO4 of the host material of the organic light-emitting layer 131 is 5eV, so that since holes are transited toward the high energy level, since the highest occupied orbital level HOMO4 of the host material of the organic light-emitting layer 131 is relatively low, the transition of holes is not facilitated, and thus the second electron-transporting layer functions to block holes.
In one implementation, as shown in fig. 6, which is another cross-sectional view of the organic light emitting device at the AA' position in fig. 3 provided in the embodiment of the present invention, the thickness d2 of the second electron transporting layer 133 is in the range of: d2 is more than or equal to 2 nm. As can be seen from the above embodiments, the second electron transport layer 133 does not contain the first dopant, so that the first dopant is prevented from affecting the organic light emitting layer 131, and thus the thickness of the second electron transport layer is not too thin. Illustratively, the thickness d2 of the second electron transport layer 133 ranges from: d2 is more than or equal to 2 nm.
In one embodiment, the doping concentration of the first dopant 1321 of the first electron transport layer 132 on the side closer to the cathode 14 is greater than the doping concentration of the first dopant 1321 of the first electron transport layer 132 on the side farther from the cathode 14.
In this embodiment, the concentration of the first dopant 1321 in the first electron transport layer 132 decreases in the direction from the cathode 14 to the organic light emitting layer 131, so that electrons do not span higher energy levels, accumulation of electrons at the interface is avoided, injection of electrons is facilitated, and the response speed of the organic light emitting device is increased.
Moreover, the doping concentration of the first dopant in the first electron transport layer 132 close to the cathode 14 is slightly higher, so that the electron carriers generated by the cathode 14 can smoothly migrate into the first electron transport layer 132, thereby providing the migration rate of the electron carriers. In one embodiment, as shown in fig. 7, which is another cross-sectional view of the organic light emitting device at AA' of fig. 3 according to an embodiment of the present invention, the organic functional layer 13 further includes a third electron transport layer 134 located between the first electron transport layer 132 and the second electron transport layer 133.
In this embodiment, the third electron transport layer 134 is disposed between the first electron transport layer 132 and the second electron transport layer 133, so that the distance from the first electron transport layer 132 containing the first dopant 1321 to the organic light emitting layer 131 is increased, the influence of the first dopant 1321 on the organic light emitting layer 131 can be blocked, and the lanthanide in the first dopant 1321 can be prevented from absorbing the photons generated by the organic light emitting layer 131.
In addition, in the process of the transition of the electrons from the cathode 14 to the organic light emitting layer 131, the electrons first transition from the first electron transport layer 132 to the third electron transport layer 134, and then transition to the second electron transport layer 133, so that an energy level gradient of the electron transition is formed, the electrons do not need to cross higher energy levels, the accumulation of the electrons on an interface is avoided, the injection of the electrons is facilitated, and the response speed of the organic light emitting device is improved.
In one embodiment, the third electron transport layer 134 is not doped with the first dopant 1321, and the material of the electron transport matrix in the third electron transport layer 134 is the same as the material of the electron transport matrix in the first electron transport layer 132.
In this embodiment, since the third electron transport layer 134 is not doped with the first dopant 1321, the first dopant 1321 can be effectively prevented from affecting the organic light emitting layer 131.
Illustratively, both the electron transport matrix of the third electron transport layer 134 and the electron transport matrix of the first electron transport layer 132 may be Yb, so that the electron carrier transfer efficiency and the electron carrier injection efficiency may be improved.
In one embodiment, shown in fig. 8, which is another cross-sectional view of the organic light emitting device at AA' of fig. 3 according to an embodiment of the present invention, the third electron transporting layer 134 is doped with a first dopant 1321. Also, the doping concentration of the first dopant 1321 in the third electron transit layer 134 is smaller than the doping concentration of the first dopant 1321 in the first electron transit layer 132. In this embodiment, the concentration of the first dopant 1321 in the third electron transport layer 134 is lower than the concentration of the first dopant 1321 in the first electron transport layer 132, and a concentration gradient of the first dopant 1321 is formed in a direction from the cathode 14 to the organic light emitting layer 131, so that electrons do not cross a higher energy level, accumulation of electrons at an interface is avoided, injection of electrons is facilitated, and a response speed of the organic light emitting device is increased.
In addition, the third electron transport layer 134 is closer to the organic light emitting layer 131 than the first electron transport layer 132, and only if the concentration of the first dopant 1321 in the third electron transport layer 134 is lower than the concentration of the first dopant 1321 in the first electron transport layer 132, the first dopant 1321 is ensured not to diffuse into the second electron transport layer 132, and the organic light emitting layer 131 is not affected.
As can be seen from the above embodiments, although the third electron transport layer 134 contains the first dopant 1321, the second electron transport layer 133 does not contain the first dopant 1321 because the second electron transport layer 133 is disposed between the third electron transport layer 134 and the organic light emitting layer 131, and thus the first dopant 1321 can be effectively prevented from entering the organic light emitting layer 131.
In one embodiment, with continued reference to fig. 8, third electron transport layer 134 is doped with a first dopant 1321, and the doping concentration of first dopant 1321 in third electron transport layer 134 on the side closer to first electron transport layer 132 is greater than the doping concentration of first dopant 1321 in third electron transport layer 134 on the side farther from first electron transport layer 132. In other words, since the concentration of the first dopant 1321 in the first electron transit layer 132 is relatively large, it diffuses toward the third electron transit layer 134, so that the concentration of the third electron transit layer 134 on the side close to the first electron transit layer 132 is relatively high.
In this embodiment, the concentration of the first dopant 1321 in the third electron transport layer 134 decreases in the direction from the cathode 14 to the organic light emitting layer 131, so that the first dopant 1321 is not diffused into the second electron transport layer 132, and the organic light emitting layer 131 is not affected.
In addition, since the first dopant 1321 is provided in the third electron transport layer 134, a barrier for injecting electron carriers from the first electron transport layer 132 into the third electron transport layer 134 is lowered, and transition of the electron carriers is utilized.
In combination with the above embodiments, the concentration of the first dopant 1321 is gradually decreased in the direction from the cathode 14 to the organic light emitting layer 131, so that electrons do not span higher energy levels, accumulation of electrons at the interface is avoided, electron injection is facilitated, and the response speed of the organic light emitting device is improved.
In one embodiment, in the present embodiment, the material of the electron transport matrix in the third electron transport layer 134 is the same as the material of the electron transport matrix in the first electron transport layer 132; for example, the electron transport matrix of the third electron transport layer 134 may be bipyridine, triazine ring, lithium quinoline, or the like, so that the electron carrier transfer efficiency and the electron carrier injection efficiency may be improved.
Alternatively, the material of the electron transport matrix in the third electron transport layer 134 is the same as the material of the electron transport matrix in the second electron transport layer 133. For example, the electron transport matrix of the third electron transport layer 134 may be a carbazole-based material, a thiophene-based material, a fluorene-based material, or a spiro-based material, so as to suppress the mobility rate of the hole carriers and prevent the electron carriers and the hole carriers from accumulating and recombining in the third electron transport layer.
In one embodiment, the first dopant 1321 can be a lanthanide metal. Exemplary are Sm, Eu, Tm or Yb, etc. In combination with the above embodiments, the first electron transport layer 132 doped with the first dopant 1321 can effectively improve the electron injection capability and the electron transport capability.
In another embodiment, the first dopant 1321 is a metal oxide or a metal halide of a lanthanide metal.
In another embodiment, the first electron transport layer 132 is doped with at least two first dopants 1321, the at least two first dopants 1321 comprising different lanthanide metal elements. Illustratively, the first dopant may include Yb and Sm; or comprises Yb and Eu, or comprises Sm and Tm, and the like.
In this embodiment, two different lanthanide metal elements are doped, so that the injection capability and the mobility of the electron carrier can be further improved.
In one embodiment, as shown in fig. 9, which is another cross-sectional view of the organic light emitting device at AA' of fig. 3 according to an embodiment of the present invention, an electron injection layer 138 is further included between the cathode 14 and the first electron transport layer 132, and the electron injection layer 138 is a lanthanide metal. The lanthanide metal can improve the injection capability of the electron carriers, so when the electron injection layer 138 is the lanthanide metal, the interface barrier between the cathode 14 and the first electron transport layer 132 is reduced, and the injection capability of the electrons is improved, so that more electron carriers migrate toward the organic light emitting layer 131.
Further, the electron injection layer 138 has a work function smaller than that of the cathode 14. Since the electron carriers are shifted to a low energy level, the electron injection layer 138 has a work function smaller than that of the cathode 14, thereby facilitating the electron carrier transition and increasing the mobility of the electron carriers.
Further, the electron injection layer 138 has a work function greater than that of the first dopant 1321.
In this embodiment, since the electron carriers are transited to a low energy level, after the work function of the electron injection layer 138 is greater than that of the first dopant 1321, the work function of the first electron transport layer 132 including the first dopant 1321 is made smaller than that of the electron injection layer 138, which is beneficial to the transition of the electron carriers and increases the mobility of the electron carriers.
The present embodiment provides an organic light emitting display device, as shown in fig. 10, which is a schematic structural diagram of the organic light emitting display device according to the embodiment of the present invention, and the organic light emitting display device includes the organic light emitting display panel 1. It should be noted that although fig. 10 illustrates a mobile phone, the organic light emitting display device is not limited to the mobile phone, and specifically, the organic light emitting display device may include, but is not limited to, any electronic device having a display function, such as a Personal Computer (PC), a Personal Digital Assistant (PDA), a wireless handheld device, a Tablet Computer (Tablet Computer), an MP4 player, or a television.
In the present invention, the organic light emitting display device includes the organic light emitting display panel 1, so that the organic light emitting display device can achieve all the beneficial effects of the organic light emitting display panel 1, that is, the first electron transport layer 132 is disposed between the cathode 14 and the organic light emitting layer 131, the first electron transport layer 132 includes the first dopant 1321, and the first dopant 1321 includes the lanthanide, so that the mobility rate of electrons generated by the cathode 14 to migrate to the organic light emitting layer 131 can be increased, the injection barrier can be reduced, and the electrons can be transferred to the first electron transport layer 132. And, after applying a negative bias to the cathode, the electron carriers migrate toward the organic light emitting layer 131 toward a low energy level against the potential barrier, and the work function of the first dopant 1321 is smaller than that of the cathode 14, facilitating the migration of the electron carriers from the cathode 14 to the first electron transport layer 132.
Since the first dopant 1321 includes the lanthanide, when the lanthanide occupies a higher volume percentage of the first electron transport layer 1321, the first dopant 1321 may converge in the first electron transport layer 132 to generate black spots, which may affect the light transmittance of the first electron transport layer 132 and may reduce the yield of the product. Also, when the first dopant 1321 occupies a low volume percentage of the first electron transit layer 1321, it affects the migration of electron carriers, and in this embodiment, in order to balance the electron carrier transit efficiency and the light transmittance of the first electron transit layer 132, the doping percentage of the first dopant 1321 in the first electron transit layer 132 is set to be between 0.5% and 7%.
In addition, the melting point range of the first dopant is set to be 750-900 ℃, the boiling point is lower than 2300 ℃, the preparation process is facilitated, and illustratively, when the first dopant is evaporated into the first electron transport layer by using an evaporation process, the melting point and the boiling point are relatively low, so that the formed film layer structure and the organic material serving as a dopant host are not damaged.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. An organic light emitting display panel, comprising:
an array substrate including a plurality of driving elements;
an organic light emitting device provided corresponding to the driving element, the organic light emitting device including an anode and a cathode, and an organic functional layer between the anode and the cathode, the organic functional layer including an organic light emitting layer, and a first electron transport layer between the cathode and the organic light emitting layer;
wherein the first electron transport layer comprises an electron transport matrix and a first dopant, the first dopant comprises a lanthanide, and the first dopant has a work function that is less than the work function of the cathode;
the melting point range of the first dopant is 750-900 ℃, the boiling point is lower than 2300 ℃, and the doping percentage of the first dopant in the first electron transport layer is as follows: 0.5% -7%;
an electron injection layer is further arranged between the cathode and the first electron transport layer, the electron injection layer is lanthanide metal, and the work function of the electron injection layer is larger than that of the first dopant;
the organic functional layer further comprises a second electron transport layer located between the first electron transport layer and the organic light emitting layer, the second electron transport layer being not doped with the first dopant therein, and a highest occupied orbital level HOMO2 of an electron transport host in the second electron transport layer and a highest occupied orbital level HOMO3 of a host material of the organic light emitting layer satisfy:
|HOMO2-HOMO3|<1eV；
the organic functional layer further comprises a third electron transport layer located between the first electron transport layer and the second electron transport layer, the third electron transport layer having a host material that is the same as the electron transport host material in the second electron transport layer and being doped with the first dopant, wherein,
the doping concentration of the first dopant in the third electron transport layer is less than the doping concentration of the first dopant in the first electron transport layer, and
a doping concentration of the first dopant in the third electron transport layer proximate to the first electron transport layer is greater than a doping concentration of the first dopant in the third electron transport layer distal to the first electron transport layer.
2. The organic light-emitting display panel according to claim 1,
the melting point or sublimation point of the electron transport matrix is 150-430 ℃, and the boiling point is less than 500 ℃;
the melting point or sublimation point of the organic light-emitting layer is 150-450 ℃ and the boiling point is less than 550 ℃.
3. The organic light-emitting display panel according to claim 1, wherein the thickness d of the second electron transport layer is 2nm or more.
4. The organic light-emitting display panel according to claim 1, wherein a doping concentration of the first dopant in the first electron transport layer on a side close to the cathode is greater than a doping concentration of the first dopant in the first electron transport layer on a side away from the cathode.
5. The organic light-emitting display panel according to claim 1, wherein the first dopant is a simple substance of a lanthanide metal.
6. The organic light-emitting display panel according to claim 1, wherein the first dopant is a metal oxide or a metal halide of a lanthanide metal.
7. The organic light-emitting display panel of claim 1, wherein the first electron-transporting layer is doped with at least two first dopants, the at least two first dopants comprising different lanthanide metals.
8. The organic light-emitting display panel according to claim 1, wherein a work function of the electron injection layer is smaller than a work function of the cathode.
9. An organic light emitting display device, comprising the organic light emitting display panel according to any one of claims 1 to 8.
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| CN1901243A (en) * | 2006-07-25 | 2007-01-24 | 清华大学 | Organic electroluminescence device |
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| CN102790185A (en) * | 2012-08-28 | 2012-11-21 | 友达光电（苏州）有限公司 | Organic light emitting device |
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| CN1261249A (en) * | 1999-01-21 | 2000-07-26 | Tdk株式会社 | Organic electroluminescent display device |
| CN1905235A (en) * | 2005-07-25 | 2007-01-31 | Lg电子株式会社 | Organic electroluminescence device and method for fabricating the same |
| CN1901243A (en) * | 2006-07-25 | 2007-01-24 | 清华大学 | Organic electroluminescence device |
| CN102790185A (en) * | 2012-08-28 | 2012-11-21 | 友达光电（苏州）有限公司 | Organic light emitting device |
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Effective date of registration: 20211021 Address after: No.8, liufangyuan Henglu, Donghu New Technology Development Zone, Wuhan City, Hubei Province Patentee after: WUHAN TIANMA MICRO-ELECTRONICS Co.,Ltd. Patentee after: Wuhan Tianma Microelectronics Co.,Ltd. Shanghai Branch Address before: Room 509, building 1, No. 6111, Longdong Avenue, Pudong New Area, Shanghai, 201201 Patentee before: SHANGHAI TIANMA AM-OLED Co.,Ltd. |