Display device and display panel

Abstract

The invention relates to the technical field of display, in particular to a display device and a display panel, and the display device comprises an anode, a cathode and N light-emitting units which are sequentially stacked, each light-emitting unit comprises a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer and an electron transport layer which are sequentially stacked in the direction away from the anode, and a charge generation layer is arranged between every two adjacent light-emitting units. Wherein the N light-emitting units are sequentially defined as a first light-emitting unit to an Nth light-emitting unit from the anode to the cathode; lUMO energy level difference exists between the hole blocking layer and the electron transmission layer of each light emitting unit, and the difference value between the LUMO energy level difference between the Nth light emitting unit and at least one light emitting unit from the first light emitting unit to the (N-1) th light emitting unit is not smaller than a first preset threshold value. The display device can effectively improve the problem of large color drift before and after aging of the laminated device.

Description

Technical Field

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

[0002] Organic Light Emitting Diode (OLED) has gradually become the mainstream display technology for smartphones due to its advantages of self-luminescence, fast response, low power consumption, thinness and foldability. With the improvement of technology maturity and the reduction of industry chain costs, OLED has gradually penetrated into medium and large-sized display fields such as tablets and notebook computers. This puts higher requirements on the lifespan and color gamut of OLED devices, and the device solutions conventionally used in smartphones are no longer applicable. Summary of the invention

[0003] In order to overcome the above-mentioned defects, the present invention provides a display device and a display panel, which can effectively improve the problem of large color drift before and after aging of the stacked device.

[0004] In a first aspect, the present invention provides a display device, comprising:

[0005] anode;

[0006] a cathode; and

[0007] N light-emitting units stacked in sequence between the anode and the cathode, wherein each light-emitting unit comprises a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer and an electron transport layer stacked in sequence in a direction away from the anode, and a charge generation layer is arranged between adjacent light-emitting units, wherein the N light-emitting units are sequentially defined as the first light-emitting unit to the Nth light-emitting unit from the anode to the cathode, and N is a natural number greater than or equal to 2;

[0008] There is a LUMO energy level difference between the hole blocking layer and the electron transport layer of each light-emitting unit, and the difference between the LUMO energy level difference between the Nth light-emitting unit and at least one of the 1st to N-1th light-emitting units is not less than a first preset threshold.

[0009] Further, the light-emitting layer includes a red light-emitting unit, a green light-emitting unit and a blue light-emitting unit, wherein the red light-emitting unit includes a red light organic layer and a red light material sequentially stacked in a direction toward a cathode, the green light-emitting unit includes a green light organic layer and a green light material layer sequentially stacked in a direction toward a cathode, the blue light-emitting layer includes a blue light organic layer and a blue light material layer sequentially stacked in a direction toward a cathode, and wherein the red light organic layer and the green light organic layer are a multi-layer stacked structure;

[0010] The HOMO energy level difference between the multiple red organic layers of at least one of the second to Nth light emitting units is not less than the second preset threshold, and the HOMO energy level difference between the multiple green organic layers is not less than the third preset threshold.

[0011] Furthermore, the first preset threshold is 0.1 eV.

[0012] Furthermore, the red light organic layer is two layers, and the green light organic layer is two layers;

[0013] The second preset threshold is 0.1 eV and the third preset threshold is 0.1 eV.

[0014] Furthermore, at least one of the first to the N-1th light emitting units,

[0015] The material HB1 of the hole blocking layer includes:

[0016]

[0017] The materials ET1 of the electron transport layer include:

[0018] and

[0021] In the Nth light-emitting unit, the material of the hole blocking layer HB2 includes:

[0022]

[0023] The materials ET2 of the electron transport layer include:

[0024] and

[0027] Further, and The mass ratio is 1:1; and The mass ratio is 1:1.

[0033] Furthermore, the red light organic layer includes a first red light layer and a second red light layer, the first red light layer is closer to the anode than the second red light layer, and the material RP1 of the first red light layer includes:

[0034]

[0035] The material RP2 of the second red light layer includes:

[0036]

[0037] The green light organic layer includes a first green light layer and a second green light layer. The first green light layer is closer to the anode than the second green light layer. The material GP1 of the first green light layer includes:

[0038]

[0039] The material GP2 of the second green light layer includes:

[0040]

[0041] Furthermore, the charge generation layer includes an N-type charge generation layer and a P-type charge generation layer stacked in sequence from the anode toward the cathode.

[0042] Furthermore, the device further comprises: a hole injection layer arranged between the anode and the first light-emitting unit.

[0043] Furthermore, the device further includes: a light extraction layer formed on the cathode.

[0044] In a second aspect, the present invention provides a display panel, comprising:

[0045] substrate;

[0046] The display devices are arranged in an array and formed on the substrate.

[0047] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0048] In the technical solution for implementing the present invention, the present invention significantly improves the problem of large color drift before and after aging of the stacked device by limiting the electron and hole injection barriers of different light-emitting units and introducing a double auxiliary light-emitting layer structure.

[0049] The implementation of the present invention not only does not affect the key performance indicators of the stacked device, such as voltage, efficiency, and life, but also can improve the performance of products equipped with stacked devices without any modification to the existing mass production lines, thereby providing great convenience for product application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, among which:

[0051] Figure 1 It is a schematic diagram of the structure of an existing double-layer stacked OLED;

[0052] Figure 2is a schematic diagram of stacking N light-emitting units according to an embodiment of the present invention;

[0053] Figure 3 is a schematic diagram of the stacked structure of each light-emitting unit according to an embodiment of the present invention;

[0054] Figure 4 is a schematic structural diagram of a light-emitting layer according to an embodiment of the present invention;

[0055] Figure 5 is a schematic diagram of a stacked OLED structure including two light-emitting units according to an embodiment of the present invention;

[0056] Figure 6 It is defined according to one embodiment of the present invention that ΔLUMO2-ΔLUMO1≥0.1 ev.

[0057] Reference numerals list :

[0058] 1: anode; 2: cathode; 3: light-emitting unit; 3-1: hole transport layer; 3-2: electron blocking layer; 3-3: light-emitting layer; 331: red light-emitting unit; 332: green light-emitting unit; 333: blue light-emitting unit; 3-4: hole blocking layer; 3-5: electron transport layer; 4: charge generation layer; 4-1: N-type charge generation layer; 4-2: P-type charge generation layer; 5: hole injection layer. DETAILED DESCRIPTION

[0059] Some embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0060] Conventional double-layer OLED structure and its OLED color coordinate drift data

[0061] Stacked OLED is a new device technology that connects two or more light-emitting units in series through a charge generation layer. By connecting devices in series, the efficiency and life of the device are increased exponentially, and it has broad application prospects in medium-sized devices. Figure 1 A typical stacked OLED device combination is shown, taking the existing double-layer stacked OLED as an example, which is composed of a first light-emitting unit and a second light-emitting unit. The light-emitting layer of the first light-emitting unit is located in the first period of the microcavity standing wave, and the light-emitting layer of the second light-emitting unit is located in the second period of the microcavity standing wave. Figure 1 Describe the device structure in detail. The device structure from bottom to top is:

[0062] The hole injection layer (HIL), the first light-emitting unit, the N-type charge generation layer (NCGL), the P-type charge generation layer (PCGL), the second light-emitting unit, the metal cathode (CTD) and the light extraction layer (CPL) are sequentially deposited on the anode.

[0063] The first light-emitting unit is as follows from bottom to top:

[0064] a first hole transport layer (HTL1), a first electron blocking layer (EBL1), a first light emitting layer, a first hole blocking layer (HBL1) and a first electron transport layer (ETL1);

[0065] Red, green and blue top-emitting stacked light-emitting devices are prepared respectively by vacuum evaporation. The first light-emitting layer includes a first red light-emitting unit, a first green light-emitting unit and a first blue light-emitting unit arranged in parallel. The first red light-emitting unit includes a first red light organic layer (R Prime1) and a first red light material (R EML1) stacked in sequence toward a cathode. The first green light-emitting unit includes a first green light organic layer (G Prime1) and a first green light material layer (G EML1) stacked in sequence toward the cathode. The first blue light-emitting layer includes a first blue light organic layer (BPrime1) and a first blue light material layer (B EML1) stacked in sequence toward the cathode.

[0066] The second light-emitting unit is as follows from bottom to top:

[0067] a second hole transport layer (HTL2), a second electron blocking layer (EBL2), a second light emitting layer, a second hole blocking layer (HBL2) and a second electron transport layer (ETL2);

[0068] The second light-emitting layer includes a second red light-emitting unit, a second green light-emitting unit and a second blue light-emitting unit arranged in parallel, the second red light-emitting unit includes a second red light organic layer (R Prime2) and a second red light material (R EML2) stacked in sequence toward the cathode direction, the second green light-emitting unit includes a second green light organic layer (G Prime2) and a second green light material layer (G EML2) stacked in sequence toward the cathode direction, and the second blue light-emitting layer includes a second blue light organic layer (B Prime2) and a second blue light material layer (B EML2) stacked in sequence toward the cathode direction.

[0069] The materials of each layer of the first light-emitting unit and the second light-emitting unit are the same organic material, so that the energy level difference between the layers is zero.

[0070] For top-emitting stacked devices, the light-emitting layers of the first light-emitting unit and the second light-emitting unit make different contributions to the light color of the device. Due to the existence of the charge generation layer, there are differences in charge injection and transfer between the first and second light-emitting units. During current aging, the brightness decay rates of the two light-emitting units may be different. The superimposed two light-emitting layers make different contributions to the light color of the device, and the color coordinates of the device before and after reliability are very likely to shift significantly.

[0071] The existing stacked OLED was subjected to an aging test using a fixed current. The red, green, and blue light-emitting devices decayed to 95% of the initial brightness, respectively. The color coordinate change values ​​of the conventional implementation scheme device after the brightness decayed to 95% are shown in Table 1. Since the two superimposed light-emitting layers contribute differently to the light color of the device, the color coordinates of the device before and after the reliability test are very likely to shift significantly.

[0072] Table 1 Drift of color coordinates in superimposed two luminescent layers

[0073] Brightness decays to 95% color coordinate change value Blue light devices 0.0002 Green light devices 0.0004 Red light devices 0.0003

[0074] As can be seen from Table 1, during the aging process of the stacked device, the brightness attenuation of different light-emitting units shows significant non-uniformity. This inconsistency leads to different brightness attenuation of different colors during use. Over time, this difference will gradually accumulate and eventually cause color drift problems, which in turn affects the overall performance and display effect of the device.

[0075] Defining the electron and hole injection barriers for different light-emitting units

[0076] The present invention aims to solve the problem of color drift caused by inconsistent brightness attenuation of different light-emitting units during the aging process of the stacked OLED device. Without changing the basic structure of the existing stacked OLED device, the problem is improved by limiting the electron and hole injection barriers of different light-emitting units. The specific description is as follows.

[0077] The present invention provides a display device, referring to Figure 2 ,include:

[0078] Anode 1;

[0079] cathode 2; and

[0080] N light-emitting units 3 are stacked in sequence between the anode 1 and the cathode 2 .

[0081] A charge generation layer 4 is disposed between adjacent light emitting units 3, wherein the N light emitting units are sequentially defined as the first light emitting unit to the Nth light emitting unit from the anode toward the cathode, where N is a natural number greater than or equal to 2. Figure 2The figure shows a stacking diagram of N light-emitting units, where N=1, 2, N-1, N; when N is 2, there are two light-emitting units in the entire display device, namely the first light-emitting unit and the second light-emitting unit from bottom to top, and a charge generation layer 4 is connected between two adjacent light-emitting units. When N=3, there are three light-emitting units in the entire display device, namely the first light-emitting unit, the second light-emitting unit and the third light-emitting unit from bottom to top, and so on, forming a stacking structure of multiple light-emitting units.

[0082] The stacked structure of each light emitting unit 3 is shown in FIG. Figure 3 Each light-emitting unit 3 includes a hole transport layer 3-1, an electron blocking layer 3-2, a light-emitting layer 3-3, a hole blocking layer 3-4 and an electron transport layer 3-5 which are stacked in sequence in a direction away from the anode 1.

[0083] There is a LUMO energy level difference between the hole blocking layer 3-4 and the electron transport layer 3-5 of each light-emitting unit 3, and the difference between the LUMO (LUMO: Lowest Unoccupied Molecular Orbital, the orbit with the lowest energy level of unoccupied electrons is called the lowest unoccupied orbital) energy level difference between the Nth light-emitting unit and at least one of the 1st to N-1th light-emitting units is not less than the first preset threshold.

[0084] OLED includes an anode, a cathode, and a light-emitting layer disposed between the anode and the cathode. The light-emitting principle is to inject holes and electrons from the anode and the cathode into the light-emitting layer respectively. When the electrons and holes meet in the light-emitting layer, the electrons and holes recombine to generate excitons. When the excited state changes to the ground state, these excitons emit light. The electrons of the Nth light-emitting unit are directly injected from the cathode, while for the 1st light-emitting unit to the N-1th light-emitting unit, the electrons are injected by the electrons of the cathode passing through the charge generation layer layer by layer. The present invention improves the problem of large color drift before and after aging of the stacked device by increasing the electron and hole injection barriers of the Nth light-emitting unit and other light-emitting units.

[0085] In one embodiment, the first preset threshold is 0.1 eV.

[0086] In one embodiment, referring to Figure 1 The stacked OLED includes two light-emitting units, which are sequentially defined as the first light-emitting unit and the second light-emitting unit from the anode toward the cathode, satisfying the following energy level difference:

[0087] ΔLUMO2-ΔLUMO1≥0.1 eV;

[0088] Among them, ΔLUMO2=HBL2 LUMO-ETL2 LUMO; ΔLUMO1=HBL1 LUMO-ETL1 LUMO.

[0089] HBL2 is the hole blocking layer of the second light-emitting unit; ETL2 is the electron transport layer of the second light-emitting unit; HBL1 is the hole blocking layer of the first light-emitting unit; and ETL1 is the electron transport layer of the first light-emitting unit.

[0090] The calculation process is:

[0091] S1, calculate the LUMO energy level difference between the hole blocking layer and the electron transport layer of the first light-emitting unit, recorded as ΔLUMO1.

[0092] S2, calculating the LUMO energy level difference between the hole blocking layer and the electron transport layer of the second light-emitting unit, recorded as ΔLUMO2.

[0093] S3, setting the difference between ΔLUMO2 and ΔLUMO1, and setting the difference to be greater than or equal to 0.1 eV.

[0094] In one embodiment, the stacked OLED includes three light-emitting units, which are sequentially defined as a first light-emitting unit, a second light-emitting unit, and a third light-emitting unit from the anode toward the cathode, satisfying the following energy level difference:

[0095] ΔLUMO3-ΔLUMO1≥0.1 eV; and / or

[0096] ΔLUMO3-ΔLUMO2≥0.1 eV;

[0097] Among them, ΔLUMO3=HBL3 LUMO-ETL3 LUMO; ΔLUMO2=HBL2 LUMO-ETL2 LUMO; ΔLUMO1=HBL1 LUMO-ETL1 LUMO.

[0098] The calculation process of this embodiment can be understood by referring to the above S1-S3. In this embodiment, ΔLUMO3 is the LUMO energy level difference between the hole blocking layer and the electron transport layer of the third light-emitting unit.

[0099] HBL3 is the hole blocking layer of the third light-emitting unit; ETL3 is the electron transport layer of the third light-emitting unit; HBL2 is the hole blocking layer of the second light-emitting unit; ETL2 is the electron transport layer of the second light-emitting unit; HBL1 is the hole blocking layer of the first light-emitting unit; ETL1 is the electron transport layer of the first light-emitting unit.

[0100] When limiting the LUMO lowest unoccupied molecular orbital energy level difference of the multi-layer light-emitting layers, the more layers are involved, the more significant the correction effect on the color drift is.

[0101] Introducing a multi-auxiliary light-emitting layer structure

[0102] Next, the present invention introduces a double auxiliary light-emitting layer structure. By using a double Prime structure, the color drift of the stacked device structure before and after aging can be significantly improved, as described in detail below.

[0103] In one embodiment, the light-emitting layer 3-3 includes a red light-emitting unit 331, a green light-emitting unit 332 and a blue light-emitting unit 333, wherein the red light-emitting unit 331 includes a red light organic layer and a red light material stacked in sequence toward the cathode direction, the green light-emitting unit 332 includes a green light organic layer and a green light material layer stacked in sequence toward the cathode direction, the blue light-emitting layer 333 includes a blue light organic layer and a blue light material layer stacked in sequence toward the cathode direction, and wherein the red light organic layer and the green light organic layer are a multi-layer stacked structure.

[0104] Reference Figure 4 , at least one of the second to Nth light emitting units has a plurality of red light organic layers and a plurality of green light organic layers, Figure 4 The case where the red and green organic layers are two layers is shown in FIG. The HOMO energy level difference between the multiple red organic layers of at least one of the second to Nth light-emitting units is not less than the second preset threshold, and the HOMO energy level difference between the multiple green organic layers is not less than the third preset threshold.

[0105] In this embodiment, the light-emitting unit located above the first light-emitting unit is focused on, and the difficulty of hole injection between other layers and the first light-emitting unit is increased by increasing the highest occupied molecular orbital HOMO (Highest Occupied Molecular Orbital) energy level difference, i.e., HOMOgap, between the red and green organic layers. This adjustment helps to achieve a balance in carrier transport between the various layers, ensuring uniform distribution of electrons and holes in the light-emitting layer. In this way, the present invention enhances the stability of the light-emitting layer interface by introducing a Prime layer, significantly improving the device life of the light-emitting unit, and maintaining good performance and stability in long-term use.

[0106] In one embodiment, the red light organic layer is two layers, and the green light organic layer is two layers; the second preset threshold is 0.1 eV and the third preset threshold is 0.1 eV.

[0107] Reference Figure 5 The stacked OLED includes two light-emitting units, and in the second light-emitting unit, the red light organic layer includes a first red light layer (1st R Prime2) and a second red light layer (2nd R Prime2) stacked in sequence toward the cathode direction;

[0108] The green light organic layer includes a first green light layer (1st GPrime2) and a second green light layer (2nd G Prime2) stacked in sequence toward the cathode direction, satisfying the following relationship:

[0109] |HOMO_2nd G Prime2-HOMO_1st G Prime2|≥0.1ev; and

[0110] |HOMO_2nd R Prime2-HOMO_1st R Prime2|≥0.1ev.

[0111] The calculation process is:

[0112] 1. Calculate the absolute value of the HOMO energy level difference between the first red light layer (1st R Prime2) and the second red light layer (2nd R Prime2) in the second light-emitting unit, and calculate the absolute value of the HOMO energy level difference between the first green light layer (1st G Prime2) and the second green light layer (2nd G Prime2) in the second light-emitting unit;

[0113] 2. Control the above two absolute values ​​to be greater than or equal to 0.1ev.

[0114] Material selection for the main layer structure in display devices

[0115] In order to accurately achieve the preset energy level difference, in one embodiment, at least one of the first to the N-1th light-emitting units,

[0116] The material HB1 of the hole blocking layer includes:

[0117]

[0118] The materials ET1 of the electron transport layer include:

[0119] and

[0122] In the Nth light-emitting unit, the material HB2 of the hole blocking layer includes:

[0123]

[0124] The materials ET2 of the electron transport layer include:

[0125] and

[0128] In one embodiment, and The mass ratio is 1:1; and The mass ratio is 1:1.

[0133] In one embodiment, the red light organic layer includes a first red light layer and a second red light layer, the first red light layer is closer to the anode than the second red light layer, and the material RP1 of the first red light layer includes:

[0134]

[0135] The material RP2 of the second red light layer includes:

[0136]

[0137] The green light organic layer includes a first green light layer and a second green light layer. The first green light layer is closer to the anode than the second green light layer. The material GP1 of the first green light layer includes:

[0138]

[0139] The material GP2 of the second green light layer includes:

[0140]

[0141] When judging the energy level of a stacked OLED device, a reverse analysis method can be used to detect the energy level structure of the materials used in the layer structure of the OLED device through a nuclear magnetic resonance spectrometer. Through this detection, the energy level differences between the layers can be analyzed and identified in detail, and then the energy level differences can be calculated.

[0142] Refined structure of display devices

[0143] In one embodiment, the charge generation layer 4 includes an N-type charge generation layer 4 - 1 and a P-type charge generation layer 4 - 2 stacked in sequence from the anode toward the cathode.

[0144] In one embodiment, the device further comprises: a hole injection layer 5 disposed between the anode and the first light-emitting unit.

[0145] In one embodiment, the device further comprises: a light extraction layer 6 formed on the cathode 2 .

[0146] In one embodiment, the cathode of the device includes, from bottom to top, a first ITO layer, an Ag metal layer, and a second ITO layer.

[0147] Application of display devices

[0148] The present invention further provides a display panel, comprising:

[0149] substrate;

[0150] The display devices are arranged in an array and formed on the substrate.

[0151] The display device of the present invention is used to test the effect of improving color shift

[0152] Example 1

[0153] This embodiment provides a display device, which is consistent with the device structure of a conventional double-layer OLED structure. Figure 1 The only difference from the conventional structure is that different HBL and ETL materials are used in the first light-emitting unit and the second light-emitting unit of Example 1, as shown in Table 2, wherein HBL1 and HBL2 are BCP and DPVBi respectively, and ETL1 and ETL2 are formed by doping TPBi with BPhen and Liq in a ratio of 5:5 respectively.

[0154] Table 2 Materials of HBL1, HBL2, ETL1 and ETL2 in Example 1

[0155]

[0156]

[0157] like Figure 6 As shown, this embodiment defines:

[0158] ΔLUMO2-ΔLUMO1≥0.1 eV; wherein ΔLUMO2=HBL2 LUMO-ETL2 LUMO; and ΔLUMO1=HBL1 LUMO-ETL1 LUMO.

[0159] Taking the conventional double-layer OLED structure as the reference device, by limiting the LUMO energy level difference of HBL1 / ETL1 and HBL2 / ETL2, as shown in Table 3, the decay rates of the first light-emitting unit and the second light-emitting unit during current aging tend to be consistent. The test results are shown in Table 4.

[0160] Table 3 LUMO energy level difference between the first light-emitting unit and the second light-emitting unit

[0161] Reference Device Embodiment 1 Device ΔLUMO2-ΔLUMO1 0.0ev 0.2ev

[0162] Table 4. CIE-x color coordinate change value when brightness decays to 95% @1931 color space

[0163] Reference Device Example 1 Blue light devices ΔCIE-x=0.0002 ΔCIE-x=0.0001 Green light devices ΔCIE-x=0.0004 ΔCIE-x=0.0003 Red light devices ΔCIE-x=0.0003 ΔCIE-x=0.0002

[0164] It can be seen from the test data in Table 4 that the color shift before and after the reliability is improved by adopting the embodiment method.

[0165] Example 2

[0166] Reference Figure 5 The present invention provides a device structure design, which is different from the first embodiment in that, in the second light-emitting unit of the present embodiment, the red light organic layer is two layers, the green light organic layer is two layers, the red light organic layer includes a first red light layer (1st RPrime2) and a second red light layer (2nd R Prime2) stacked in sequence toward the cathode direction; the green light organic layer includes a first green light layer (1st G Prime2) and a second green light layer (2nd GPrime2) stacked in sequence toward the cathode direction. The materials of 1st G Prime2 and 2nd G Prime2 are TPD and TCTA, respectively, and the materials of 1st G Prime2 and 2nd G Prime2 are NPD and TAPC, respectively, and their structural formulas are shown in Table 5.

[0167] Table 5 Material selection for red and green light organic layers

[0168]

[0169]

[0170] The HOMO Gap relationship between the 1st R Prime2 and the 2nd R Prime2 satisfies the following relationship:

[0171] |HOMO_2nd G Prime2-HOMO_1st G Prime2|≥0.1ev; and

[0172] |HOMO_2nd R Prime2-HOMO_1st R Prime2|≥0.1ev.

[0173] Taking the conventional double-layer OLED structure as a reference device, the present invention improves the charge transfer balance of the second light-emitting unit by setting a double G Prime and a double R Prime structure in the second light-emitting unit and limiting the HOMO energy level difference between 1st G prim2 and 2nd G Prime2 as well as 1st R prime2 and 2nd R Prime2, as shown in Table 6. The test results are shown in Table 7.

[0174] Table 6 HOMO energy level difference of the second light-emitting unit double G Prime and double R Prime structures

[0175]

[0176] Table 7. CIE-x color coordinate change value when brightness decays to 95% @1931 color space

[0177] Reference Device Example 2 Blue light devices ΔCIE-x=0.0002 ΔCIE-x=0.0002 Green light devices ΔCIE-x=0.0004 ΔCIE-x=0.0002 Red light devices ΔCIE-x=0.0003 ΔCIE-x=0.0002

[0178] It can be seen from the data in Table 7 that the present invention sets a double G Prime and double R Prime structure in the second light-emitting unit and limits the HOMO energy level difference between 1st G prim2 and 2nd G Prime2 as well as 1st R pr ime2 and 2nd R Prime2, thereby improving the charge transfer balance of the second light-emitting unit and increasing the stability of the interface between the Prime layer and the light-emitting layer, thereby significantly improving the device life of the second light-emitting unit and improving the color shift before and after reliability.

[0179] The present invention significantly improves the problem of large color drift before and after aging of the stacked device by adopting a method of limiting electron and hole injection barriers of different light-emitting units and introducing a double auxiliary light-emitting layer structure.

[0180] The implementation of the present invention not only does not affect the key performance indicators of the stacked device, such as voltage, efficiency, and life, but also can improve the performance of products equipped with stacked devices without any modification to the existing mass production lines, thereby providing great convenience for product application and promotion.

[0181] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, different steps do not have to be performed in such an order. They can be performed simultaneously (in parallel) or in other orders. These changes are within the scope of protection of the present invention.

[0182] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A display device, characterized in that: include: anode; cathode; as well as N light-emitting units stacked in sequence between the anode and the cathode, wherein each light-emitting unit comprises a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer and an electron transport layer stacked in sequence in a direction away from the anode, and a charge generation layer is arranged between adjacent light-emitting units, wherein the N light-emitting units are sequentially defined as the first light-emitting unit to the Nth light-emitting unit from the anode to the cathode, and N is a natural number greater than or equal to 2; There is a LUMO energy level difference between the hole blocking layer and the electron transport layer of each light-emitting unit, and the difference between the LUMO energy level difference between the Nth light-emitting unit and at least one of the 1st to N-1th light-emitting units is not less than a first preset threshold.

2. The display device according to claim 1, characterized in that The light-emitting layer comprises a red light-emitting unit, a green light-emitting unit and a blue light-emitting unit, wherein the red light-emitting unit comprises a red light organic layer and a red light material sequentially stacked in a direction toward a cathode, the green light-emitting unit comprises a green light organic layer and a green light material layer sequentially stacked in a direction toward a cathode, the blue light-emitting layer comprises a blue light organic layer and a blue light material layer sequentially stacked in a direction toward a cathode, and wherein the red light organic layer and the green light organic layer are a multi-layer stacked structure; The HOMO energy level difference between the multiple red organic layers of at least one of the second to Nth light emitting units is not less than the second preset threshold, and the HOMO energy level difference between the multiple green organic layers is not less than the third preset threshold.

3. The display device according to claim 1 or 2, characterized in that: The first preset threshold is 0.1 eV.

4. The display device according to claim 2, characterized in that The red light organic layer has two layers, and the green light organic layer has two layers; The second preset threshold is 0.1 eV and the third preset threshold is 0.1 eV.

5. The display device according to claim 1, characterized in that At least one of the first to the N-1th light emitting units, The material HB1 of the hole blocking layer includes: The materials ET1 of the electron transport layer include: In the Nth light-emitting unit, the material HB2 of the hole blocking layer includes: The materials ET2 of the electron transport layer include:

6. The display device according to claim 5, characterized in that and The mass ratio is 1:1; The mass ratio is 1:

1.

7. The display device according to claim 3 or 5, characterized in that: The red light organic layer includes a first red light layer and a second red light layer. The first red light layer is closer to the anode than the second red light layer. The material RP1 of the first red light layer includes: The material RP2 of the second red light layer includes: The green light organic layer includes a first green light layer and a second green light layer. The first green light layer is closer to the anode than the second green light layer. The material GP1 of the first green light layer includes: The material GP2 of the second green light layer includes:

8. The display device according to claim 1, characterized in that The charge generation layer includes an N-type charge generation layer and a P-type charge generation layer stacked in sequence from the anode toward the cathode.

9. The display device according to claim 1, characterized in that: The device further includes: a hole injection layer disposed between the anode and the first light emitting unit.

10. The device according to claim 1, characterized in that The device further includes a light extraction layer formed on the cathode.

11. A display panel, characterized in that: include: substrate; A display device according to any one of claims 1 to 10 arranged in an array formed on the substrate.

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