Light-emitting device and display panel

Abstract

The embodiments of the present application disclose a light-emitting device and a display panel. A light-emitting device, whose luminous color is any one of the primary colors of red or green, comprises: a light-emitting layer comprising a main material; a compensation layer, wherein current-carrying holes are arranged on the hole injection side of the light-emitting layer; the light-emitting device has a light-on state and an operating state, and the light-emitting device has a light-on voltage in the light-on state that is lower than the operating voltage in the operating state; in the light-on state, there is a first activation energy difference ΔEa1 between the activation energy of the main material and the activation energy of the compensation layer, and the first activation energy difference ΔEa1 is less than 0 eV. The light-emitting device provided in the first aspect of the embodiments of the present application has a higher light-on voltage, which avoids the problem of display color deviation of the display panel when displaying low grayscale, and improves the color rendering accuracy of the display panel.

Description

Technical Field

[0001] The present invention relates to the field of display, and in particular to a light-emitting device and a display panel. Background Art

[0002] With the rapid development of electronic devices, organic light-emitting diode (OLED) display panels have been widely used in various consumer electronic products such as mobile phones, televisions, personal digital assistants, digital cameras, laptops, desktop computers, etc. due to their advantages such as high image quality, power saving, thin body and wide application range, becoming the mainstream display panel in the display field.

[0003] The turn-on voltages of the red, green, and blue light-emitting devices in an OLED display panel are inconsistent. When the display panel displays low grayscale, the display panel generally cannot maintain a true white light image well, and there is a color cast on the display.

[0004] Therefore, a new type of light emitting device and display panel is urgently needed. Summary of the Invention

[0005] The present invention provides a light-emitting device and a display panel. The light-emitting device provided in the first aspect of the present invention has a higher turn-on voltage, which reduces the difference between the turn-on voltage of a blue light-emitting device and the turn-on voltage of a blue light-emitting device. This avoids the problem of color shift when the display panel displays low grayscale images, thereby improving the color rendering accuracy of the display panel.

[0006] In a first aspect, an embodiment of the present application provides a light-emitting device, wherein the light-emitting color is any one of the primary colors of red or green, including:

[0007] a light-emitting layer comprising a host material;

[0008] a compensation layer, the current-carrying holes being disposed on the hole-injection side of the light-emitting layer;

[0009] The light emitting device has an on state and an operating state, and a turn-on voltage of the light emitting device in the on state is lower than an operating voltage of the light emitting device in the operating state;

[0010] In the on state, there is a first activation energy difference ΔEa1 between the activation energies of the host material and the compensation layer, and the first activation energy difference ΔEa1 is less than 0 eV.

[0011] In a possible implementation of the first aspect of the embodiment of the present application, the value of the first activation energy difference ΔEa1 is -0.12 eV to -0.08 eV.

[0012] In a possible implementation of the first aspect of the embodiments of the present application, the light-emitting device further includes a hole transport layer disposed on the hole injection side of the light-emitting layer, and the compensation layer is disposed between the hole transport layer and the light-emitting layer;

[0013] In the on state, the activation energy of the compensation layer is higher than that of the hole transport layer and the host material.

[0014] In a possible implementation of the first aspect of the embodiment of the present application, in the on state,

[0015] There is a second activation energy difference ΔEa2 between the activation energies of the compensation layer and the hole transport layer, and the second activation energy difference ΔEa2 has a value range of 0.2 eV to 0.3 eV.

[0016] In a possible implementation of the first aspect of the embodiments of the present application, in the on state, there is a third activation energy difference ΔEa3 between the host material and the hole transport layer, and the value range of ΔEa3 is 0.1 eV to 0.2 eV.

[0017] In a possible implementation of the first aspect of the embodiment of the present application, in a working state, there is a fourth activation energy difference ΔEa4 between the main material and the compensation layer, and the fourth activation energy difference ΔEa4 is ≥ 0 eV;

[0018] Preferably, the fourth activation energy difference ΔEa4 ranges from 0 eV to 0.05 eV.

[0019] In a possible implementation of the first aspect of the embodiments of the present application,

[0020] In a working state, the activation energy of the hole transport layer stacked on the hole injection side of the compensation layer is lower than the activation energy of the compensation layer.

[0021] In a possible implementation of the first aspect of the embodiments of the present application,

[0022] In the working state, there is a fifth activation energy difference ΔEa5 between the activation energies of the compensation layer and the hole transport layer, and the value range of the fifth activation energy difference ΔEa5 is 0.08 eV to 0.12 eV;

[0023] Preferably, in a working state, there is a sixth activation energy difference ΔEa6 between the activation energies of the host material and the hole transport layer, and the value range of ΔEa6 is 0.1 eV to 0.2 eV.

[0024] In a possible implementation of the first aspect of the embodiments of the present application,

[0025] The light-emitting layer also includes a guest material doped in a host material.

[0026] A second aspect of the present application provides a display panel having the light-emitting device of the first aspect of the present application. The display panel of the second aspect of the present application has high color rendering accuracy and good display effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which like or similar reference numerals designate like or similar features and which are not drawn to scale.

[0028] Figure 1 1 is a diagram showing the relationship between activation energy levels of the functional layers of the first red light-emitting device in comparative example 1 of the first aspect of the present application in the on state;

[0029] Figure 2 1 is a diagram showing the relationship between activation energy levels of the functional layers of the first red light-emitting device in comparative example 1 of the first aspect of the present application in a working state;

[0030] Figure 3 is a diagram showing the relationship between activation energy levels of the functional layers of the second red light-emitting device in the on state in Experimental Example 1 of the first aspect of the embodiments of the present application;

[0031] Figure 4 is a diagram showing the relationship between activation energy levels of the functional layers of the second red light-emitting device in the working state in Experimental Example 1 of the first aspect of the embodiments of the present application;

[0032] Figure 5 2 is a diagram showing the relationship between activation energy levels of the functional layers of the first green light-emitting device in the on state in Comparative Example 2 of the first aspect of the embodiment of the present application;

[0033] Figure 6 2 is a diagram showing the relationship between activation energy levels of the functional layers of the first green light-emitting device in comparative example 2 of the first aspect of the present invention in a working state;

[0034] Figure 7 is a diagram showing the relationship between activation energy levels of the functional layers of the second green light-emitting device in the on state in Experimental Example 2 of the first aspect of the embodiment of the present application;

[0035] Figure 8 is a diagram showing the relationship between activation energy levels of the functional layers of the second green light-emitting device in the working state in Experimental Example 2 of the first aspect of the embodiments of the present application;

[0036] In the picture:

[0037] HT-1: hole transport layer;

[0038] R'-1: first red compensation layer; R'-2: second red compensation layer;

[0039] RH-1: first red main body material;

[0040] G'-1: first green compensation layer; G'-2: second green compensation layer;

[0041] GH-1: The first green host material;

[0042] E-electron injection direction;

[0043] F-hole injection direction;

[0044] Unknown - Energy level region not considered. DETAILED DESCRIPTION

[0045] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the present invention.

[0046] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, the elements defined by the phrase "comprising..." do not exclude the presence of other identical elements in the process, method, article, or device comprising the elements.

[0047] It should be understood that when describing the structure of a component, when a layer or a region is referred to as being "on" or "over" another layer or region, it may mean that it is directly on the other layer or region, or that other layers or regions are included between it and the other layer or region. Furthermore, if the component is turned over, the layer or region will be "below" or "beneath" the other layer or region.

[0048] The inventors discovered that when a display panel displays low grayscale images, the different turn-on voltages of the red, green, and blue light-emitting devices prevent the display panel from displaying pure white. This results in a color shift phenomenon, resulting in a single, impure color. The inventors discovered that using the formula E = hc / λ, where h = 6.626*10 34 (m 2 kg / s), c=3*10 8 (m / s), 1eV=1.6*10 -19 (J), J=kg*m 2 / s 2 , and the wavelength of blue light is 460nm, the wavelength of green light is 530nm, and the wavelength of red light is 520nm. Theoretically, the minimum turn-on voltage for a blue light-emitting device is 2.7V, the minimum turn-on voltage for a green light-emitting device is 2.34V, and the minimum turn-on voltage for a red light-emitting device is 2.0V. Therefore, red and green light-emitting devices are both smaller than blue light-emitting devices. Therefore, turning on the blue light-emitting device will generate crosstalk current in the display panel, causing the red and / or green light-emitting devices to be slightly turned on, resulting in a color shift on the display panel.

[0049] To this end, a first aspect of an embodiment of the present application provides a light-emitting device that emits light in either a primary color of red or green. The light-emitting device includes a light-emitting layer and a hole transport layer disposed on the hole injection side of the light emitter for carrying holes. The light-emitting layer includes a host material. The light-emitting device has an on state and an operating state. The on state has a turn-on voltage that is lower than the operating voltage in the operating state.

[0050] In the on state, there is a first activation energy difference ΔEa1 between the activation energies of the host material and the compensation layer, and the first activation energy difference ΔEa1 is less than 0 eV.

[0051] In a possible implementation of the first aspect of the embodiment of the present application, the value of the first activation energy difference ΔEa1 is -0.12 eV to -0.08 eV.

[0052] The light-emitting device of the first aspect of the embodiment of the present application has an increased turn-on voltage when in the on state, thereby preventing the influence of current crosstalk generated when turning on light-emitting devices with higher turn-on voltages (such as blue light-emitting devices) on its own turn-on state. This improves the color rendering accuracy of the display panel when displaying low grayscale images, thereby enhancing the display quality and user experience.

[0053] In the embodiments of the present application, activation energy refers to the potential barrier that electrons or holes need to overcome when transferring between different functional layers of the light-emitting device. In the embodiments of the present application, the activation energy of a single layer or multiple functional layers can be understood as the potential barrier that electrons (or holes) need to overcome when flowing from the cathode side (or anode side) through the single layer or multiple functional layers, wherein the functional layer refers to the carrier layer and the light-emitting layer in the light-emitting device. The carrier layer in the light-emitting device includes an electron transport layer, a hole blocking layer, a compensation layer, a hole transport layer, and a hole injection layer, etc. Alternatively, the activation energy in the embodiments of the present application can also be understood as the energy required for electrons to flow from the cathode side through the functional layer carrying electrons, and the energy required for holes to flow from the anode side through the functional layer carrying holes.

[0054] When the functional layer is composed of a single material, the activation energy Ea of that material is the activation energy Ea corresponding to the functional layer. When the functional layer is composed of two or more materials, the activation energy of the functional layer can be calculated by first obtaining the product of the activation energy of each material and the corresponding molar mass fraction of each material; then summing these products to obtain the overall activation energy of the functional layer.

[0055] The activation energy can be calculated using the Arrhenius formula: Ea = E0 + mRT, where Ea is the activation energy, E0 and m are temperature-independent constants, T is the temperature, and R is the molar gas constant. This formula shows that the activation energy is temperature-dependent. Furthermore, the activation energy obtained using the above formula is expressed in joules (J). This can be converted to electron volts (eV) using a simple conversion formula: 1eV = 1.602176565*10 -19 J. It will be understood that a basic formula for calculating Ea is given in the embodiments of the present application, and those skilled in the art can calculate Ea based on the basic Arrhenius formula given in the embodiments of the present application or by various variations of the Arrhenius formula.

[0056] In some embodiments, the activation energy of the carrier layer and the light-emitting layer on the hole injection side of the light-emitting layer in the light-emitting device needs to be calculated, and the activation energy difference between the carrier layers on the hole injection side and between the light-emitting layer and the carrier layer on the hole injection side needs to be calculated. A single-hole device can be made and the single-hole device is tested by powering on to obtain the IV curve (i.e., current-voltage curve) of the single-hole device. Based on the IV curve of the single-hole device, the activation energy is calculated using the Arrhenius formula or multiple variations of the Arrhenius formula. It should be noted that the single-hole device in the embodiment of the present application only allows holes to pass through.

[0057] As a specific example, when calculating the difference ΔEa between the activation energies of the hole transport layer and the main material in a light-emitting device. A first single-hole device with a hole transport layer is made, and the first single-hole device is tested by power-on to obtain a first IV curve. The Ea1 of the hole transport layer is calculated using the Arrhenius formula. A second single-hole device with a hole transport layer and a light-emitting layer (having only the main material) is made, and the second single-hole device is tested by power-on so that holes flow from the hole transport layer to the light-emitting layer to obtain a second IV curve. The Ea2 of the hole transport layer and the light-emitting layer (having only the main material) is calculated using the Arrhenius formula. The difference calculation method can be used, that is, according to ΔEa=Ea2-Ea1, to calculate the difference ΔEa between the activation energies of the main material and the hole transport layer in the light-emitting device. The single-hole device only allows holes to pass through.

[0058] In some examples, a first single-hole device that only allows holes to pass through is produced, and the first single-hole device includes a stacked anode, a first hole transport layer, an electron blocking layer, and a cathode. A second single-hole device that only allows holes to pass through is produced, and the second single-hole device includes a stacked anode, a second hole transport layer, a light-emitting layer (having only a main material), an electron blocking layer, and a cathode. The first hole transport layer is the same as the second hole transport layer, and the first single-hole device and the second single-hole device are only tested with the light-emitting layer (having only a main material) as a single variable. The electron blocking layer can hinder the electrons generated by the cathode from being transmitted in the single-hole device, thereby achieving the purpose of allowing only holes to be transmitted in the single-hole device.

[0059] In some embodiments, it is necessary to calculate the activation energy of the carrier layer and the light-emitting layer on the electron injection side of the light-emitting layer in the light-emitting device, and it is necessary to calculate the activation energy difference between the carrier layer on the electron injection side and between the light-emitting layer and the carrier layer on the electron injection side. All of these can be done by making a single-electron device and conducting a power-on test on the single-electron device to obtain the IV curve (i.e., current-voltage curve) of the single-electron device. On the basis of the IV curve of the single-electron device, the activation energy is calculated using the Arrhenius formula or multiple variations of the Arrhenius formula. It should be noted that the single-electron device in the embodiment of the present application only allows electrons to pass through. As a specific example, when calculating the difference ΔEa' between the activation energy of the electron transport layer and the main material in the light-emitting device. A first single-electron device with an electron transport layer is made, the first single-electron device is tested by power-on to obtain a first IV curve, and the Arrhenius formula is used to calculate the Ea1' of the electron transport layer. A second single-electron device was fabricated, comprising an electron transport layer and a light-emitting layer (containing only a host material). This device was then tested by applying power to the device, allowing electrons to flow from the electron transport layer to the light-emitting layer. A second IV curve was obtained, and the Ea2' values ​​for the electron transport layer and the light-emitting layer (containing only a host material) were calculated using the Arrhenius equation. The difference in activation energy, ΔEa', between the host material and the electron transport layer in the light-emitting device can be calculated using the difference calculation method: ΔEa' = Ea2' - Ea1'.

[0060] In some examples, a first single-electron device that only allows electrons to pass through is made, and the first single-electron device includes a stacked anode, a hole blocking layer, a first electron transport layer, and a cathode. A second single-electron device that only allows electrons to pass through is made, and the second single-electron device includes a stacked anode, a hole blocking layer, a light-emitting layer (having only a main material), a second electron transport layer, and a cathode. The first electron transport layer is the same as the second electron transport layer, and the first single-electron device and the second single-electron device are only tested with the light-emitting layer (having only a main material) as a single variable. The hole blocking layer can hinder the holes generated by the anode from being transmitted in the single-electron device, thereby achieving the purpose of allowing only electron transmission in the single-electron device.

[0061] In other embodiments, the activation energy of the functional layer can be obtained using thermogravimetric analysis. For example, thermogravimetric analysis can be performed on the host materials in the hole transport layer, compensation layer, or light-emitting layer, and the activation energy of each functional layer can be directly calculated based on the thermogravimetric analysis results. Thermogravimetric analysis is a method for determining the relationship between the mass of a substance and temperature (or time) under a program-controlled temperature. After obtaining a thermogravimetric curve using thermogravimetric analysis, the average activation energy can be calculated using the Freeman-Carroll method or the OWAZa method.

[0062] Generally, the highest occupied energy orbital (HOMO) and the lowest occupied energy orbital (LUMO) are used to measure the energy level matching of each functional layer in a light-emitting device. The materials of each functional layer of the light-emitting device in the OLED display panel are selected based on the energy level matching predicted by the highest occupied energy orbital (HOMO) and the lowest occupied energy orbital (LUMO). However, HOMO and LUMO only consider the injection efficiency of carriers, and do not comprehensively consider the influence of other factors such as temperature and carrier transport on the carrier transfer process in each functional layer. Therefore, using the highest occupied energy orbital (HOMO) and the lowest occupied energy orbital (LUMO) to measure the energy level matching of each functional layer in a light-emitting device is likely to cause large deviations in the calculation results of the energy level difference between the functional layers, making it impossible to design a light-emitting device that meets expectations.

[0063] In the embodiment of the present application, the activation energy of the functional layers in the light-emitting device and the activation energy difference between the functional layers are used to design the light-emitting device. This can comprehensively consider factors such as carrier injection, carrier transmission, and temperature between the actual functional layers in the light-emitting device, and can more accurately and precisely define the difference relationship between the activation energies of the functional layers in the light-emitting device in the on state and / or the working state (that is, the energy barrier relationship between the functional layers). The difference relationship between the activation energies of the functional layers of the light-emitting device in accordance with the embodiment of the present application can better solve the problem of the red or green light-emitting device having too low a turn-on voltage in the on state, and the light-emitting device being affected by the crosstalk current, resulting in a low grayscale display color shift on the display panel.

[0064] In some optional embodiments, in the light-emitting device of the first aspect of the present application, the first activation energy difference ΔEa1 is -0.12 eV to -0.08 eV.

[0065] In some optional embodiments, the light-emitting device further includes a hole transport layer disposed on the hole injection side of the light-emitting layer, and a compensation layer disposed between the hole transport layer and the light-emitting layer. Both the hole transport layer and the compensation layer in the light-emitting device are used to carry holes. When the light-emitting device is in the on state, the activation energy of the compensation layer is higher than the activation energy of the hole transport layer and the main material. In these embodiments, the compensation layer in the light-emitting device is equivalent to a hole transport energy barrier layer between the hole transport layer and the main material when the light-emitting device is in the on state. In order for holes to cross the activation energy level of the compensation layer from the hole transport layer and flow into the light-emitting layer, more current needs to be applied to the light-emitting device to achieve the hole transfer from the hole transport layer to the light-emitting material in the light-emitting layer. Applying more current manifests itself in the light-emitting process of the light-emitting device as the need to apply more voltage to the light-emitting device to achieve the hole transfer from the hole transport layer to the light-emitting material in the light-emitting layer, thereby further contributing to the increase in the turn-on voltage of the light-emitting device.

[0066] In some optional embodiments, when the light-emitting device is in the on state, there is a second activation energy difference ΔEa2 between the activation energies of the compensation layer and the hole transport layer, and the second activation energy difference ΔEa2 ranges from 0.2 eV to 0.3 eV.

[0067] In some optional embodiments, when the light-emitting device is in the on state, there is a third activation energy difference ΔEa3 between the host material and the hole transport layer, and the value range of ΔEa3 is 0.1 eV to 0.2 eV.

[0068] In some optional embodiments, in addition to having a first activation energy difference ΔEa1 between the activation energies of the host material and the compensation layer in the on-state, where ΔEa1 is less than 0 eV, the light-emitting device also has a fourth activation energy difference ΔEa4 between the host material and the compensation layer in the operating state, where ΔEa4 is greater than or equal to 0 eV. In some embodiments, the fourth activation energy difference ΔEa4 ranges from 0 eV to 0.05 eV. Therefore, in these embodiments, the turn-on voltage of the light-emitting device is increased in the on-state, while the operating voltage of the light-emitting device remains substantially unchanged in the operating state (also referred to as the driving state or operating state). This increased turn-on voltage of the light-emitting device prevents the light-emitting device from being induced by current crosstalk, prevents color shift in the display panel, especially at low grayscale and low brightness, and improves display accuracy. While the light-emitting device is in the operating state, the substantially unchanged operating voltage of the light-emitting device ensures that parameters such as the light-emitting efficiency and brightness of the light-emitting device are not affected, further ensuring the display quality of the display panel. It should be noted that the light-emitting device is in a low grayscale when in the on state, and the luminous brightness is low relative to the luminous brightness of the light-emitting device in the operating state. It is understandable that the light-emitting device is in a high grayscale when in the operating state, and the luminous brightness is high relative to the luminous brightness of the light-emitting device in the on state. In some examples, the low grayscale range is grayscale 0 to grayscale 64, and the high grayscale range is grayscale 250 to grayscale 255. Theoretically, the minimum turn-on voltage for a blue light-emitting device is 2.7V, the minimum turn-on voltage for a green light-emitting device is 2.34V, and the minimum turn-on voltage for a red light-emitting device is 2.0V. Generally, the operating voltage range for blue, green, and red light-emitting devices is 3.5V to 4.0V. Generally, the operating voltage of a blue light-emitting device is greater than that of a green light-emitting device, and the operating voltage of a green light-emitting device is greater than that of a red light-emitting device.

[0069] In some optional embodiments, when the light-emitting device is in operation, the activation energy of a hole transport layer stacked on the hole injection side of the compensation layer is lower than that of the compensation layer. Furthermore, a fourth activation energy difference ΔEa4 exists between the host material of the light-emitting device and the compensation layer, and the fourth activation energy difference ΔEa4 is ≥ 0 eV. This means that the activation energy of the compensation layer is between the activation energies of the hole transport layer and the host material of the light-emitting layer. In these optional embodiments, the activation energy of the compensation layer is between the activation energies of the hole transport layer and the host material, allowing the operating voltage of the light-emitting device to remain substantially unchanged during operation without increasing. This ensures the luminous efficiency of the light-emitting device while avoiding excessive power consumption. Furthermore, the activation energy of the compensation layer being between the activation energies of the hole transport layer and the host material is equivalent to forming a hole injection energy level buffer layer between the hole transport layer and the host material, further improving the efficiency and quality of hole transfer from the hole transport layer to the host material. This can mitigate interfacial impact between the host material and the hole transport layer caused by the large activation energy difference, thereby extending the life of the light-emitting device.

[0070] In some optional embodiments, when the light-emitting device is in operation, there is a fifth activation energy difference ΔEa5 between the activation energies of the compensation layer and the hole transport layer, and the fifth activation energy difference ΔEa5 ranges from 0.08 eV to 0.12 eV.

[0071] In some optional embodiments, when the light-emitting device is in operation, there is a sixth activation energy difference ΔEa6 between the activation energies of the host material of the light-emitting layer and the hole transport layer, and the value range of ΔEa6 is 0.1 eV to 0.2 eV.

[0072] In some embodiments, when the light-emitting device is in operation, there is a sixth activation energy difference ΔEa6 between the activation energies of the host material and the compensation layer, and the value range of ΔEa6 is 0 eV to 0.05 eV.

[0073] In some optional embodiments, the light-emitting layer of the light-emitting device includes a host material and a guest material doped in the host material.

[0074] In some embodiments, the light-emitting device includes a hole injection layer, a hole transport layer, and a compensation layer disposed on the hole injection side of the light-emitting layer and stacked in the direction of hole injection into the light-emitting layer. The light-emitting device also includes an electron transport layer and a hole blocking layer disposed on the electron injection side of the light-emitting layer and stacked in the direction of electron injection into the light-emitting layer.

[0075] To further demonstrate the effectiveness of the light-emitting device provided in the first aspect of this application in resolving low-grayscale color shift in display panels, the following two sets of comparative experiments were designed. The first set of experiments tested the turn-on voltage and operating voltage of the red light-emitting device. The second set of experiments tested the turn-on voltage and operating voltage of the green light-emitting device.

[0076] The first set of experiments includes Comparative Example 1 and Experimental Example 1. In Comparative Example 1, a first red light-emitting device comprising a hole transport layer, a compensation layer, and a light-emitting layer was tested for turn-on voltage and operating voltage. In Comparative Example 1, the light-emitting layer of the first red light-emitting device comprises a first red host material. The activation energy relationship of the hole transport layer, the compensation layer, and the light-emitting layer of the first red light-emitting device in Comparative Example 1 in the turn-on state is as follows: Figure 1 As shown, in the hole injection direction, the activation energy of the hole transport layer is less than the activation energy of the compensation layer, and the activation energy of the compensation layer is less than the activation energy of the red host material. The activation energy relationship of the hole transport layer, the compensation layer and the light-emitting layer in the first red light-emitting device in comparative example 1 is as follows: Figure 2 As shown, in the hole injection direction, the activation energy of the hole transport layer is less than the activation energy of the compensation layer, and the activation energy of the compensation layer is less than the activation energy of the red host material.

[0077] In Experimental Example 1 of the first set of experiments, a second red light-emitting device comprising a hole transport layer, a compensation layer, and a light-emitting layer was tested for turn-on voltage and operating voltage. Furthermore, the light-emitting layer in Experimental Example 1 comprises a first red host material, and except for the compensation layer, the remaining functional layers of the second red light-emitting device in Experimental Example 1 are identical to those in Comparative Example 1. That is, only the compensation layer was used as a variable in the experiments in Experimental Example 1 and Comparative Example 1. The activation energy relationship of the hole transport layer, the compensation layer, and the light-emitting layer in the second red light-emitting device in Experimental Example 1 when in the turn-on state is shown in FIG. Figure 3 As shown in FIG, in the hole injection direction, the activation energy of the hole transport layer is lower than the activation energy of the first red host material, and the activation energy of the compensation layer is higher than the activation energy of the first red host material and the hole transport layer. The activation energy relationship of the hole transport layer, the compensation layer and the light-emitting layer in the second red light-emitting device in Experimental Example 1 is as follows: Figure 4 As shown, in the hole injection direction, the activation energy of the hole transport layer is less than the activation energy of the compensation layer, and the activation energy of the compensation layer is less than the activation energy of the first red host material.

[0078] Table 1 shows the test results of Comparative Example 1 and Experimental Example 1

[0079]

[0080] In Table 1, Von represents the turn-on voltage, Vd represents the operating voltage, and Eff. represents the efficiency (cd / A). As can be seen from Table 1, the turn-on voltage of Experimental Example 1 is increased by 0.24V relative to that of Comparative Example 1, and the difference between the operating voltages of Experimental Example 1 and Comparative Example 1 is -0.03V, which means that the operating voltage of Experimental Example 1 is basically the same as that of Comparative Example 1. Therefore, it can be clearly seen in the first set of experiments that the turn-on voltage of the light-emitting device in the embodiment of the present application is increased in the turn-on state, and the operating voltage remains basically unchanged in the operating state. The light-emitting device can resist the negative impact of crosstalk current when the display panel displays low grayscale, avoid the problem of color deviation of the display panel, and further improve the color rendering accuracy of the display panel, especially the color rendering accuracy at low grayscale.

[0081] The second set of experiments includes Comparative Example 2 and Experimental Example 2. In Comparative Example 2, a first green light-emitting device comprising a hole transport layer, a compensation layer, and a light-emitting layer was tested for turn-on voltage and operating voltage. In Comparative Example 2, the light-emitting layer of the single-hole device comprises a first green host material. The activation energy relationship of the hole transport layer, the compensation layer, and the light-emitting layer of the first green light-emitting device in Comparative Example 2 in the turn-on state is shown as follows: Figure 5 As shown, in the hole injection direction, the activation energy of the hole transport layer is less than the activation energy of the compensation layer, and the activation energy of the compensation layer is less than the activation energy of the first green host material. The activation energy relationship of the hole transport layer, the compensation layer and the light-emitting layer in the first green light-emitting device in comparative example 2 is as follows: Figure 6 As shown, in the hole injection direction, the activation energy of the hole transport layer is less than the activation energy of the compensation layer, and the activation energy of the compensation layer is less than the activation energy of the first green host material.

[0082] In Experimental Example 2 of the second set of experiments, a second green light-emitting device comprising a hole transport layer, a compensation layer, and a light-emitting layer was tested for turn-on voltage and operating voltage. Furthermore, the light-emitting layer in Experimental Example 2 comprises a first green host material, and except for the compensation layer, the other functional layers of the second green light-emitting device in Experimental Example 2 are the same as those in Comparative Example 2. That is, only the compensation layer was used as a variable in the experiments in Experimental Example 2 and Comparative Example 2. The activation energy relationship of the hole transport layer, the compensation layer, and the light-emitting layer in the second green light-emitting device in Experimental Example 2 when in the turn-on state is shown in FIG. Figure 7 As shown in FIG, in the hole injection direction, the activation energy of the hole transport layer is lower than the activation energy of the first green host material, and the activation energy of the compensation layer is higher than the activation energy of the first green host material and the hole transport layer. The activation energy relationship of the hole transport layer, the compensation layer and the light-emitting layer in the second green light-emitting device in Experimental Example 2 is as follows: Figure 8 As shown, in the hole injection direction, the activation energy of the hole transport layer is less than the activation energy of the compensation layer, and the activation energy of the compensation layer is less than the activation energy of the first green host material.

[0083] Table 2 shows the test results of Comparative Example 2 and Experimental Example 2

[0084]

[0085]

[0086] In Table 2, Von represents the turn-on voltage, Vd represents the operating voltage, and Eff. represents the efficiency (cd / A). Table 2 shows that the turn-on voltage of Experimental Example 2 is 0.17V higher than that of Comparative Example 2, while the difference in operating voltage between Experimental Example 2 and Comparative Example 2 is -0.05V, which means that the operating voltage of Experimental Example 2 is essentially the same as that of Comparative Example 2. Therefore, it can be clearly seen in the second set of experiments that the turn-on voltage of the light-emitting device in the embodiment of the present application increases when in the turn-on state, while the operating voltage remains essentially unchanged when in the operating state. The light-emitting device can resist the influence of crosstalk current when the display panel displays low grayscale, avoid the problem of color shift on the display panel, and further improve the accuracy of the display panel's color rendering, especially at low grayscales.

[0087] A second aspect of the present application provides a display panel having the light-emitting device of the first aspect of the present application. The display panel of the second aspect of the present application has high color rendering accuracy and good display effect.

[0088] While the embodiments of the present invention are described above, these embodiments do not exhaustively describe all details and do not limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the above description. These embodiments are selected and described in detail in this specification in order to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better utilize the invention and its modifications. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A light emitting device, characterized in that: Its luminous color is any one of the primary colors of red or green, including: a light-emitting layer comprising a host material; A compensation layer for carrying holes is provided on the hole injection side of the light-emitting layer; The light emitting device has an on state and an operating state, and the on voltage of the light emitting device in the on state is lower than the operating voltage in the operating state; In the light-on state, the activation energy of the main material minus the activation energy of the compensation layer is a first activation energy difference ΔEa1, and the first activation energy difference ΔEa1 is less than 0 eV; In the working state, the activation energy of the main material minus the activation energy of the compensation layer is a fourth activation energy difference ΔEa4, and the fourth activation energy difference ΔEa4 is ≥ 0 eV.

2. The light emitting device according to claim 1, wherein The first activation energy difference ΔEa1 ranges from -0.12 eV to -0.08 eV.

3. The light emitting device according to claim 1, wherein The light emitting device further comprises a hole transport layer disposed on the hole injection side of the light emitting layer, and the compensation layer is disposed between the hole transport layer and the light emitting layer; In the on state, the activation energy of the compensation layer is higher than the activation energy of the hole transport layer and the host material.

4. The light emitting device according to claim 3, characterized in that In the light-on state, The activation energy of the compensation layer minus the activation energy of the hole transport layer is a second activation energy difference ΔEa2, and the value range of the second activation energy difference ΔEa2 is 0.2 eV to 0.3 eV.

5. The light emitting device according to claim 3, characterized in that In the on state, the activation energy of the host material minus the activation energy of the hole transport layer is a third activation energy difference ΔEa3, and the value range of ΔEa3 is 0.1 eV to 0.2 eV.

6. The light emitting device according to any one of claims 1 to 5, characterized in that: The fourth activation energy difference ΔEa4 has a value range of 0 eV to 0.05 eV.

7. The light emitting device according to any one of claims 1 to 5, characterized in that: In the working state, the activation energy of the hole transport layer stacked on the hole injection side of the compensation layer is lower than the activation energy of the compensation layer.

8. The light emitting device according to claim 7, characterized in that In the working state, the activation energy of the compensation layer minus the activation energy of the hole transport layer is a fifth activation energy difference ΔEa5, and the value range of the fifth activation energy difference ΔEa5 is 0.08 eV to 0.12 eV.

9. The light emitting device according to claim 7, characterized in that In the working state, the activation energy of the host material minus the activation energy of the hole transport layer is a sixth activation energy difference ΔEa6, and the value range of ΔEa6 is 0.1 eV to 0.2 eV.

10. The light emitting device according to claim 1, wherein The light-emitting layer further includes a guest material doped in the host material.

11. A display panel, characterized in that: The light emitting device comprises the light emitting device according to any one of claims 1 to 10.

Images