Organic light-emitting display panel and device

An organic light-emitting display panel and an organic light-emitting display device are provided. The organic light-emitting display panel includes: a first electrode, a first light-emitting layer, a second light-emitting layer and a second electrode that are stacked in turn. The ratio of the hole mobility to the electron mobility of the first light-emitting layer is greater than or equal to 102, and the ratio of the electron mobility to the hole mobility of the second light-emitting layer is greater than or equal to 102.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No. 201611159259.6, filed on Dec. 15, 2016 and entitled “ORGANIC LIGHT-EMITTING DISPLAY PANEL AND DEVICE”, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relates to organic light-emitting display technologies, and in particular, to an organic light-emitting display panel and an organic light-emitting display device.

BACKGROUND

Due to the technical advantages of no backlight source, high contrast, small thickness, large visual angle and fast reaction speed, etc., Organic Light-Emitting Display has become one of the important development directions of the display industries.

The existing organic light-emitting display panel includes: a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, an anode and a substrate. During operation, a bias voltage is applied between the anode and the cathode of the organic light-emitting display panel, so that holes and electrons can break through the interfacial energy barrier and migrate respectively from the hole transport layer and the electron transport layer to the light-emitting layer, and on the light-emitting layer, electrons and holes are recombined to generate excitons. The excitons are unstable, and energy can be released. The energy is transferred to the molecules of the organic light-emitting material in the light-emitting layer, so that the molecules transit from a ground state to an excited state. The excited state is very unstable, and thus the excited molecules return to the ground state from the excited state, so that a light emitting phenomenon appears due to radiative transition. Therefore, in the organic light-emitting display panel, the performance of the organic light-emitting display panel is determined by the combination efficiency of the electrons and the holes. However, in the existing organic light-emitting display panel, the recombination efficiency of the electrons and the holes is low, causing the high bias voltage required by the organic light-emitting display panel, the low light-emitting efficiency, and the very short lifetime.

SUMMARY

The present disclosure provides an organic light-emitting display panel and an organic light-emitting display device, thereby improving the combination efficiency of electrons and holes in the organic light-emitting display panel, and hence lowering the bias voltage required by the organic light-emitting display panel, improving the light-emitting efficiency of the organic light-emitting display panel, and prolonging the lifetime of the organic light-emitting display panel.

In a first aspect, embodiments of the present invention provide an organic light-emitting display panel, which includes: a first electrode, a first light-emitting layer, a second light-emitting layer and a second electrode that are stacked in turn. The ratio of the hole mobility to the electron mobility of the first light-emitting layer is larger than or equal to 102, and the ratio of the electron mobility to the hole mobility of the second light-emitting layer is larger than or equal to 102.

In a second aspect, embodiments of the present invention further provide an organic light-emitting display device, which includes any of the organic light-emitting display panels according to the embodiments of the present invention.

In the embodiments of the present invention, by defining the ratio of the hole mobility to the electron mobility of the first light-emitting layer as larger than or equal to 102and defining the ratio of the electron mobility to the hole mobility of the second light-emitting layer as larger than or equal to 102, it solves the problems of the existing organic light-emitting display panel that due to the low combination efficiency of electrons and holes, the bias voltage required by the organic light-emitting display panel is high, the light-emitting efficiency is low, and the lifetime is very short. With the organic light-emitting display panel according to the embodiments of the present invention, the combination efficiency of electrons and holes may be improved, thereby lowering the bias voltage required by the organic light-emitting display panel, improving the light-emitting efficiency of the organic light-emitting display panel, and prolonging the lifetime of the organic light-emitting display panel.

DETAILED DESCRIPTION

The present invention will be further illustrated in detail in conjunction with the drawings and embodiments. It may be understood that, the specific embodiments described here are only set for explaining, rather than limiting, the present invention. Additionally, it further needs to be noted that, for convenient description, the drawings only show the parts related to the disclosure, rather than the whole contents.

FIG. 1Ais a structural representation of an organic light-emitting display panel according to one embodiment of the present invention. Referring toFIG. 1A, the organic light-emitting display panel includes a substrate10. The substrate10is divided into a plurality of pixel regions32and non-pixel regions31, and the pixel regions32and the non-pixel regions31are provided alternately.

The non-pixel region31includes a thin-film transistor20formed on the substrate10and a pixel-defining layer27formed on one side of the thin-film transistor20that is away from the substrate10. The pixel region32includes a pixel light-emitting unit33. The pixel light-emitting unit33includes a first electrode11, a second electrode12and a film layer formed between the first electrode11and the second electrode12.

InFIG. 1A, the thin-film transistor20may include a gate electrode21, a gate insulating layer22, an active layer23, a source electrode24and a drain electrode25. The thin-film transistor may be a thin-film transistor with a bottom-gate structure (that is, the gate electrode is located between the substrate and the active layer), or it may be a thin-film transistor with a top-gate structure (that is, the active layer is located between the substrate and the gate electrode). Exemplarily, inFIG. 1A, the thin-film transistor20is a thin-film transistor with a bottom-gate structure, where the active layer23is formed above the gate electrode21, that is, the gate electrode21may be located between the substrate10and the active layer23. The gate electrode21may be formed on the substrate10and have conductivity. The gate insulating layer22may be formed on the gate electrode21and cover the gate electrode21. The gate insulating layer22insulates the gate electrode21from the active layer23. The active layer23may be formed on the gate insulating layer22. The active layer23may correspond to the gate electrode21, for example, the active layer23may be overlapped with the gate electrode21. The active layer13may include a source region and a drain region that are doped with an N-type or P-type dopant, and a channel region that connects the source region to the drain region. Generally, the source region and the drain region are respectively formed on the two ends of the active layer23, and the channel region is formed in the middle of the active layer23. The active layer23may include a semiconductor material. The source electrode24and the drain electrode25may be formed on the active layer23. The source electrode24and the drain electrode25may be isolated from each other and electrically connected with each other via the active layer23which serves as a channel. The source electrode24and the drain electrode25may be electrically connected to the source region and the drain region of the active layer23, respectively. The source electrode24and the drain electrode25each have conductivity.

The organic light-emitting display panel further includes a planarization layer26, and the planarization layer26may be formed on the entire substrate10. The planarization layer26corresponding to the pixel region32is formed with the pixel light-emitting unit33, and the planarization layer26corresponding to the non-pixel region31is formed with the pixel-defining layer27.

The planarization layer26is formed with a plurality of through holes28, and the drain electrode25of the thin-film transistor is electrically connected with the first electrode11of the pixel light-emitting unit33that is located in the pixel region32. Optionally, as shown inFIG. 1A, in the pixel light-emitting unit33, the first electrode11is formed on the planarization layer26corresponding to the pixel region32, and adjacent two of the pixel-defining layers27expose at least one part of the first electrode11that is located in the pixel region32. The second electrode12covers the pixel region32and the non-pixel region31.

FIG. 1Bis a structural representation of dashed area A inFIG. 1A. Referring toFIG. 1B, the organic light-emitting display panel includes: a first electrode11, a first light-emitting layer131, a second light-emitting layer132and a second electrode12that are stacked in turn. The ratio of the hole mobility to the electron mobility of the first light-emitting layer131is larger than or equal to 102, and the ratio of the electron mobility to the hole mobility of the second light-emitting layer132is larger than or equal to 102.

Here, the ratio of the hole mobility to the electron mobility of the first light-emitting layer131is larger than or equal to 102, meaning that during specific manufacturing, the material of the first light-emitting layer131is selected to meet that the ratio of the hole mobility to the electron mobility is larger than or equal to 102. Thus, the first light-emitting layer131can be made to have a very high hole transport efficiency, so that greater number of holes may be injected into the first light-emitting layer131, and holes may be accelerated to accumulate near the interface between the first light-emitting layer131and the second light-emitting layer132. The ratio of the electron mobility to the hole mobility of the second light-emitting layer132is larger than or equal to 102, meaning that during specific manufacturing, the material of the second light-emitting layer132is selected to meet that the ratio of the electron mobility to the hole mobility is larger than or equal to 102. Thus, the second light-emitting layer132may be made to have a very high electron transport efficiency, so that the greater number of electrons may be injected into the second light-emitting layer132, and the electrons may be accelerated to accumulate near the interface between the second light-emitting layer132and the first light-emitting layer131.

It may be understood that, the concentration of electrons and holes in the light-emitting layer of the organic light-emitting display panel will influence the combination efficiency of electrons and holes in the light-emitting layer, which determines the light-emitting efficiency and the performance of the organic light-emitting display panel. In the embodiments of the present invention, by defining the ratio of the hole mobility to the electron mobility of the first light-emitting layer being larger than or equal to 102and defining the ratio of the electron mobility to the hole mobility of the second light-emitting layer being larger than or equal to 102, the concentration of electrons and holes in the light-emitting layer of the organic light-emitting display panel may be improved, so that it facilitate improving the combination efficiency of electrons and holes near the interface between the first light-emitting layer131and the second light-emitting layer132and lowering the bias voltage required by the organic light-emitting display panel, thereby improving the light-emitting efficiency and the performance of the organic light-emitting display panel.

Optionally, the ratio of the hole mobility of the first light-emitting layer131to the electron mobility of the second light-emitting layer132is larger than or equal to 0.5 and is smaller than or equal to 2. In such an configuration, the hole transport capacity of the first light-emitting layer131is made close to the electron transport capacity of the second light-emitting layer132, so that carrier balance in the organic light-emitting display panel may be boosted, thereby realizing the high efficiency and the long lifetime of the organic light-emitting display panel. It should be noted that in this embodiment, further optionally, the hole mobility of the first light-emitting layer131may be defined as equal to the electron mobility of the second light-emitting layer132, and in this case, the hole transport capacity of the first light-emitting layer131can be made equal to the electron transport capacity of the second light-emitting layer132, so that carrier balance in the organic light-emitting display panel can be boosted more effectively, thereby realizing the high efficiency and the long lifetime of the organic light-emitting display panel. However, in a practical manufacture process, a certain error range may exist. As a result, optionally, the ratio of the hole mobility of the first light-emitting layer131to the electron mobility of the second light-emitting layer132may be selected as larger than or equal to 0.5 and smaller than or equal to 2.

Optionally, the sum of the thickness of the first light-emitting layer131and the second light-emitting layer132is smaller than or equal to 30 nm.

The first light-emitting layer131and/or the second light-emitting layer132may include at least one host material and at least one guest dopant.

Because in the organic light-emitting display panel, the holes are transported on the highest occupied molecular orbital (HOMO) energy level after being injected from the first electrode11, and the electrons are transported on the lowest unoccupied molecular orbital (LUMO) energy level after being injected from the second electrode12, the electrons on the lowest unoccupied molecular orbital (LUMO) energy level are combined with the holes on the highest occupied molecular orbital (HOMO) energy level near the interface between the first light-emitting layer131and the second light-emitting layer132under the action of a bias voltage. In order to lower the interfacial energy barrier between the light-emitting layers (including the first light-emitting layer131and the second light-emitting layer132) and the electrodes so as to improve the injection capacity of holes or electrons, optionally in the first light-emitting layer131or the second light-emitting layer132, the highest occupied molecular orbital (HOMO) energy level of the host material is higher than the highest occupied molecular orbital (HOMO) energy level of the guest dopant, and the lowest unoccupied molecular orbital (LUMO) energy level of the host material is lower than the lowest unoccupied molecular orbital (LUMO) energy level of the guest dopant; the highest occupied molecular orbital (HOMO) energy level of the guest dopant in the first light-emitting layer131is lower than the highest occupied molecular orbital (HOMO) energy level of the guest dopant in the second light-emitting layer132; the lowest unoccupied molecular orbital (LUMO) energy level of the guest dopant in the first light-emitting layer131is lower than the lowest unoccupied molecular orbital (LUMO) energy level of the guest dopant in the second light-emitting layer132.

Exemplarily, the first light-emitting layer131includes a first host material and a first guest dopant, and the second light-emitting layer132includes a second host material, a second guest dopant and a third guest dopant; the highest occupied molecular orbital (HOMO) energy level of the first host material is higher than the highest occupied molecular orbital (HOMO) energy level of the first guest dopant; the highest occupied molecular orbital (HOMO) energy level of the second host material is higher than the highest occupied molecular orbital (HOMO) energy level of the second guest dopant and the highest occupied molecular orbital (HOMO) energy level of the third guest dopant; the highest occupied molecular orbital (HOMO) energy level of the first guest dopant is lower than the highest occupied molecular orbital (HOMO) energy level of the second guest dopant and the highest occupied molecular orbital (HOMO) energy level of the third guest dopant; the highest occupied molecular orbital (HOMO) energy level of the second guest dopant is lower than the highest occupied molecular orbital (HOMO) energy level of the third guest dopant; the lowest unoccupied molecular orbital (LUMO) energy level of the first host material is lower than the lowest unoccupied molecular orbital (LUMO) energy level of the first guest dopant; the lowest unoccupied molecular orbital (LUMO) energy level of the second host material is lower than the lowest unoccupied molecular orbital (LUMO) energy level of the second guest dopant and the lowest unoccupied molecular orbital (LUMO) energy level of the third guest dopant; the lowest unoccupied molecular orbital (LUMO) energy level of the first guest dopant is lower than the lowest unoccupied molecular orbital (LUMO) energy level of the second guest dopant and the lowest unoccupied molecular orbital (LUMO) energy level of the third guest dopant; the lowest unoccupied molecular orbital (LUMO) energy level of the second guest dopant is higher than the lowest unoccupied molecular orbital (LUMO) energy level of the third guest dopant.

FIG. 2is a structural representation of a partial film of another organic light-emitting display panel according to one embodiment of the present invention. In comparison withFIG. 1B, inFIG. 2, the organic light-emitting display panel further includes a first auxiliary light-emitting layer14and a second auxiliary light-emitting layer15. Specifically, referring toFIG. 2, the first auxiliary light-emitting layer14is located between the first electrode11and the first light-emitting layer131; the first auxiliary light-emitting layer14includes at least one of a hole-injecting layer, a hole transport layer and an electron blocking layer. The second auxiliary light-emitting layer15is located between the second electrode12and the second light-emitting layer132; the second auxiliary light-emitting layer includes at least one of an electron-injecting layer, an electron transport layer and a hole blocking layer.

It should be noted that, inFIG. 2, the organic light-emitting display panel includes both the first auxiliary light-emitting layer14and the second auxiliary light-emitting layer15, which this is merely a specific example of the disclosure, rather than limiting the disclosure. During specific manufacturing, the organic light-emitting display panel may include only the first auxiliary light-emitting layer14, or include only the second auxiliary light-emitting layer15.

Optionally, if the organic light-emitting display panel includes the second auxiliary light-emitting layer15, the second auxiliary light-emitting layer15is doped with at least one of an alkali metal, an alkaline earth metal or a rare-earth metal. Exemplarily, the second auxiliary light-emitting layer15includes an electron transport layer; optionally, the electron transport layer is doped with at least one of an alkali metal, an alkaline earth metal or a rare-earth metal. In such a configuration, the interfacial energy barrier between the first electrode12and the organic material of the organic light-emitting display panel may be reduced, so that the electron injection capacity and the performance of the organic light-emitting display panel may be improved. Typically, the electron transport layer may be doped with at least one of lithium, natrium, kalium, rubidium, cesium, magnesium, calcium, strontium, barium, ytterbium, samarium or gadolinium.

In the above technical solutions, optionally, the first electrode11and/or the second electrode12may be taken as a light exit side electrode (that is, the electrode via which the light is emitted to the outside) of the organic light-emitting display panel, which will be illustrated in detail below by a typical example.

FIG. 3is a structural representation of a part of film layers of yet another organic light-emitting display panel according to one embodiment of the present invention. Referring toFIG. 3, the organic light-emitting display panel only takes the second electrode12as the light exit side electrode. After being formed near the interface between the first light-emitting layer131and the second light-emitting layer132, the light is emitted out via the second electrode12. Specifically, the first electrode11may include a first conductive transparent film111, a second conductive transparent film112and a reflective film113that is located between the first conductive transparent film111and the second conductive transparent film112. Optionally, in specific design, the material and the thickness of each of the films of the first electrode11may vary, so long as it can guarantee that the first electrode11has an excellent hole injection capacity and an excellent reflection effect. For example, the material of the first conductive transparent film111and the second conductive transparent film112in the first electrode11may be tin indium oxide, zinc indium oxide or a mixture of aluminum oxide and zinc oxide, the material of the reflective film113may be silver or a silver-containing alloy, and the thickness of the reflective film113may be 50 nm-150 nm. The material of the light exit side electrode (the second electrode12) may be silver or a silver-containing alloy. The thickness of the light exit side electrode (the second electrode12) may vary, so long as it can guarantee that the light exit side electrode (the second electrode12) has an excellent electron injection capacity and a good light transmissibility. For example, the material of the light exit side electrode (the second electrode12) may be a silver-containing alloy, where the percentage of volume of the silver contained in the alloy is larger than or equal to 80%, and the thickness of the light exit side electrode, i.e., the second electrode12, is 10 nm-20 nm. Based on this, in order to make the organic light-emitting display panel have a good display effect, optionally the transmissibility of the light exit side electrode (the second electrode12) under the light with a wavelength of 550 nm is larger than or equal to 20% and is smaller than or equal to 50%.

FIG. 4is a structural representation of a part of film layers of yet another organic light-emitting display panel according to one embodiment of the present invention. Referring toFIG. 4, the organic light-emitting display panel only takes the first electrode11as the light exit side electrode. After being formed near the interface between the first light-emitting layer131and the second light-emitting layer132, the light is emitted out via the first electrode11. Specifically, the material of the first electrode11is a conductive transparent material, and during specific design, the material and the thickness of the first electrode11may vary, so long as it can guarantee that the first electrode11has an excellent hole injection capacity and a good light transmissibility. For example, the conductive transparent film of the first electrode11may be made from material of tin indium oxide, zinc indium oxide or a mixture of aluminum oxide and zinc oxide. The material of the second electrode12may be silver or a silver-containing alloy. The thickness of the second electrode12may vary, so long as it can guarantee that the second electrode12has an excellent electron injection capacity and a good reflection effect. For example, the material of the second electrode12may be a silver-containing alloy, where the percentage of volume of the silver contained in the alloy is larger than or equal to 80%, and the thickness of the second electrode12may be 50 nm-150 nm.

FIG. 5is a structural representation of a part of film layers of yet another organic light-emitting display panel according to one embodiment of the present invention. Referring toFIG. 5, the organic light-emitting display panel takes both the first electrode11and the second electrode12as the light exit side electrode. After the light is formed near the interface between the first light-emitting layer131and the second light-emitting layer132, one part thereof is emitted out via the first electrode11, and the other part thereof is emitted out via the second electrode12.

It should be noted that, during the manufacturing of the organic light-emitting display panel provided in this application, the first electrode11may be first formed on a substrate, then film layers may be formed in turn between the first electrode11and the second electrode12, and the second electrode12is formed finally; or alternatively, the second electrode12may be first formed on the substrate, then film layers may be formed in turn between the first electrode11and the second electrode12, and the first electrode11is formed finally. That is, the organic light-emitting display panel may have an upright structure or an inversed structure.

One embodiment of the present invention further provides an organic light-emitting display device.FIG. 6is a structural representation of an organic light-emitting display device according to one embodiment of the present invention. Referring toFIG. 6, the organic light-emitting display device101includes any organic light-emitting display panel201of the embodiments of the present invention. Specifically, the organic light-emitting display device may be a mobile phone, a notebook computer, an intelligent wearable device and an information inquiry machine in a public hall.

In the organic light-emitting display device according to the embodiment of the present invention, by defining the ratio of the hole mobility to the electron mobility of the first light-emitting layer as larger than or equal to 102and defining the ratio of the electron mobility to the hole mobility of the second light-emitting layer as larger than or equal to 102, it solves the problems of the existing organic light-emitting display panel that due to the low combination efficiency of electrons and holes, the bias voltage required by the organic light-emitting display panel is high, the light-emitting efficiency is low, and the lifetime is very short. Thus, with the organic light-emitting display device according to the embodiment of the present invention, the combination efficiency of electrons and holes may be improved, thereby lowering the bias voltage required by the organic light-emitting display panel, improving the light-emitting efficiency of the organic light-emitting display panel, and prolonging the lifetime of the organic light-emitting display panel.

It should be noted that the embodiments of the present invention and the technical principles used therein are described as above. It should be appreciated that the disclosure is not limited to the particular embodiments described herein, and any apparent alterations, modification and substitutions can be made without departing from the scope of protection of the disclosure. Accordingly, while the disclosure is described in detail through the above embodiments, the disclosure is not limited to the above embodiments and can further include other additional embodiments without departing from the concept of the disclosure.