KR20230103979A - White Light Emitting Element and Display Device Using the Same - Google Patents

Abstract

A white light emitting device and a display device using the white light emitting device of the present invention apply an inversely structured light emitting device and a plurality of stacks emitting white light within the device, by providing an optical compensation layer to the outside of the emitting side electrode, so that the cathode electrode and the inside of the stack are provided. By reducing the thickness of the contacting electron transport layer, the driving voltage can be reduced and both viewing angle characteristics and efficiency can be improved.

Description

White light emitting element and display device using the same {White Light Emitting Element and Display Device Using the Same}

The present invention relates to a light emitting device, and more particularly, to a white light emitting device capable of reducing driving voltage and improving efficiency and viewing angle characteristics by changing the adjacent structure of an emission-side electrode in an inverted light emitting device and a display device using the same. it's about

Recently, a self-luminous display device that does not require a separate light source and is being considered as a competitive application for compact device and vivid color display. The self-emitting display device may be classified into an organic light emitting display device and an inorganic light emitting display device according to an internal light emitting material.

Meanwhile, a self-luminous display device includes a plurality of sub-pixels and emits light by including a light emitting element in each sub-pixel without a separate light source.

In addition, the display device is high-resolution, highly integrated, does not require a fine metal mask, and a tandem element commonly constituting an organic layer and a light emitting layer has been highlighted in terms of fairness, and research is being conducted on this.

In a recent light emitting display device, an inverted light emitting device (inverted OLED) is being considered in that a circuit configuration within a sub-pixel can be simplified and thus a light emitting unit can be increased. However, when a plurality of stacks between both electrodes of an inverted light emitting device are applied, the thickness of the electron transport layer is increased in order to adjust the emission position of the light emitting layer in the lowermost stack. In this case, when the thickness of the material of the electron transport layer with low mobility increases, there is a problem in that the driving voltage increases, and the viewing angle characteristic deteriorates due to the overall thickness of the stack.

The present invention is an invention to solve this problem, and a white light emitting device having a light emitting device of an inverse structure capable of reducing driving voltage and improving viewing angle characteristics and efficiency by changing an emission side electrode and an adjacent structure, and a display device using the same It is an invention about

The white light emitting device and the display device using the same according to the present invention have the following effects.

A white light emitting device and a display device using the white light emitting device of the present invention employs a white light emitting device having an inverse structure, and has an optical compensation layer externally in contact with a cathode electrode, which is an emission side, to compensate for a cavity of an internal stack structure of the white light emitting device. With the optical compensation layer, the thickness of the electron transport layer adjacent to the inner side of the cathode electrode and the thickness of the cathode electrode are lowered, thereby lowering the driving voltage of the light emitting device and improving efficiency. In addition, by reducing the thickness of the entire light emitting device structure between both electrodes where the driving voltage acts, variability due to viewing angle is reduced, thereby improving image quality.

1 is a cross-sectional view showing a white light emitting device according to an embodiment of the present invention.
2 and 3 are cross-sectional views corresponding to one sub-pixel of a display device according to various embodiments of the present invention.
FIG. 4 is a circuit diagram of one sub-pixel of the display device having the white light emitting device of FIG. 1 .
5 is a schematic cross-sectional view of an optical functional layer of a display device according to an embodiment of the present invention.
6A and 6B are cross-sectional views showing white light emitting devices used in the first and second experimental examples.
7A to 7C are cross-sectional views showing third to fifth experimental examples.
8 is a cross-sectional view showing a sixth experimental example.
9 is a graph showing white spectra of the first to sixth experimental examples.
10A to 10C are cross-sectional views showing eighth to tenth experimental examples.
11 is a cross-sectional view showing an eleventh experimental example.
12 is a graph showing white spectra of first and second experimental modifications and eighth to eleventh experimental examples.
13 is a cross-sectional view illustrating a display device according to another exemplary embodiment of the present invention.
14A to 14D are graphs showing the relationship between red, green, blue and white efficiencies and the thickness of the light compensation layer.
15 is a cross-sectional view showing a white light emitting device according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Like reference numbers throughout the specification indicate substantially the same elements. In the following description, if it is determined that a detailed description of a technique or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, the component names used in the following description are selected in consideration of the ease of writing the specification, and may be different from the part names of the actual product.

Since the shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining various embodiments of the present invention are exemplary, the present invention is not limited to those shown in the drawings. Like reference numerals designate like elements throughout this specification. In addition, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. When 'includes', 'has', 'consists of', etc. mentioned in this specification is used, other parts may be added unless 'only' is used. In the case where a component is expressed in the singular, the case including the plural is included unless there is an explicit notice.

In interpreting the components included in various embodiments of the present invention, even if there is no separate explicit board, it is interpreted as including an error range.

In describing various embodiments of the present invention, in the case of describing the positional relationship, for example, 'on ~', '~ on top', '~ on the bottom', '~ next to', etc. When the positional relationship of parts is described, one or more other parts may be located between two parts unless 'immediately' or 'directly' is used.

In describing various embodiments of the present invention, in the case of explaining the temporal relationship, for example, 'after', 'after', 'after', 'before', etc. When is described, it may also include non-continuous cases unless 'immediately' or 'directly' is used.

In describing various embodiments of the present invention, 'first ~', 'second ~', etc. may be used to describe various components, but these terms are only used to distinguish between identical and similar components. am. Therefore, components modified with 'first to' in this specification may be the same as components modified with 'second to' within the technical spirit of the present invention, unless otherwise noted.

Each feature of the various embodiments of the present invention can be partially or entirely combined or combined with each other, technically various interlocking and driving are possible, and each of the various embodiments can be implemented independently of each other or together in an association relationship. may be

Meanwhile, in the present specification, EL (electroluminescence) spectrum refers to (1) a PL (photoluminescence) spectrum reflecting inherent characteristics of a light emitting material such as a dopant material or a host material included in an organic light emitting layer, and , (2) the out-coupling emittance spectrum curve, which is determined according to the structure and optical properties of the organic light-emitting device including the thickness of organic layers such as an electron transport layer.

1 is a cross-sectional view showing a white light emitting device according to an embodiment of the present invention.

1, the white light emitting device ED according to an embodiment of the present invention has an optical compensation layer 110 on a substrate 100 and a first surface SF1 in contact with the optical compensation layer 110. A cathode electrode 120, an anode electrode 200 facing the second surface SF2 of the cathode electrode 120, and the second surface SF2 of the cathode electrode 120 and the anode electrode 200 ), an intermediate functional layer (OS) including a plurality of stacks (S1, S2, and S3) separated by charge generating layers (140, 160) and emitting white light may be included.

The 'intermediate functional layer (OS)' of the present invention is particularly named as such because it is between the opposing cathode electrode 120 and the anode electrode 200 and has a light emitting function by including a light emitting layer.

In FIG. 1 , the intermediate functional layer OS is illustrated as including three stacks, but is not limited thereto, and the intermediate functional layer OS may include at least two stacks including a charge generation layer between the stacks. Accordingly, the intermediate functional layer OS may have a 3-stack structure, a 2-stack structure, or a 4-stack structure or more.

The intermediate functional layer OS has a first stack S1 including a first blue light emitting layer 133 as a minimum configuration, and a first to third light emitting layers 153, 154, and 155 each having a longer wavelength than blue and different from each other. It may include 2 stacks (S2).

The second stack S2 may include, for example, a red light emitting layer 153 , a yellow green light emitting layer 154 , and a green light emitting layer 155 as light emitting layers.

In addition, the intermediate functional layer OS may further include a third stack S3 including the second blue light emitting layer 173 as shown in FIG. 1 in addition to the above-described minimum configuration.

The plurality of stacks including the intermediate functional layer (OS) are each divided into charge generating layers 140 and 160, each of which may include a light emitting layer, and a first stack (S1) emitting blue to indicate white. and a second stack S2 emitting light with a longer wavelength than blue. To improve efficiency, a stack having the same structure as the first stack S1 and/or the second stack S2 may be further included in the intermediate functional layer OS.

In some cases, stacks added in addition to the first and second stacks S1 and S2 may include a blue light emitting layer and other color light emitting layers adjacent to the blue light emitting layer in order to further improve blue efficiency. A stack having a blue light emitting layer and a light emitting layer of another color adjacent to the blue light emitting layer may be applied in the case of three or more stacks.

In addition, each stack is involved in transporting electrons to the light emitting layers 133, 153/154/155, 173 below each of the first blue light emitting layer 133, the red light emitting layer 153, and the second blue light emitting layer 173. It includes the first to third electron transport layers 130, 150, and 171, and the light emitting layers 133, 153-155 on the upper side of the first blue light emitting layer 133, the green light emitting layer 155, and the second blue light emitting layer 173, 173) may include first to third hole transport layers 135, 157, and 175 involved in hole transport.

The first stack S1 adjacent to the cathode electrode 120 is between the cathode electrode 120 and the first electron transport layer 130 to inject electrons from the cathode electrode 120 into the internal intermediate functional layer OS. An injection layer 125 may be further provided, and the third stack S3 adjacent to the anode electrode 200 transfers holes from the anode electrode 200 between the third hole transport layer 175 and the anode electrode 200. A hole injection layer 177 injected into the functional layer OS may be provided.

The first and second charge generation layers 140 and 160 provided between the stacks are p-type charge generation layers 140a and 160a involved in hole generation and hole transfer to adjacent stacks, respectively, and electron generation and electron generation to adjacent stacks. N-type charge generating layers 140b and 160b involved in transfer may be included.

In the white light emitting device ED of the present invention, the cathode electrode 120 contacts the first surface SF1 facing the substrate 100 and includes the optical compensation layer 110, so that the thickness of the intermediate functional layer OS and the cathode The thickness of the electrode 120 itself may be reduced. In particular, the optical compensation layer 110 is provided in contact with the first surface SF1 opposite to the second surface SF2 facing the intermediate functional layer OS, and the cathode 120 can adjust the cavity. The optical compensation layer 110, in particular, reduces the thickness of the first electron transport layer 130 inside the intermediate functional layer OS, and the first blue light emitting layer 133 forms the second surface SF2 of the cathode electrode 120. , and the resonance thickness required for the internal intermediate functional layer (OS) of the white light emitting device (ED) can be reduced, and accordingly, the driving voltage can be remarkably reduced.

The fact that the white light emitting device (ED) of the present invention reduces the driving voltage reduces the thickness of the intermediate functional layer (OS) of the entire white light emitting device (ED), and in particular, reduces the thickness of the electron transport layer, which is an organic layer having low mobility. because it can

In a light emitting device in which light is emitted only by resonance between opposite electrodes, when a plurality of stacks between both electrodes is applied, the thickness of the common layer is increased to adjust the light emitting position of the light emitting layer in the lowermost stack. In addition, the problem of the thick common layer appears as a thick hole transport layer in normal structure light emitting devices (a structure in which the anode electrode is connected to the thin film transistor and located on the lower side, and the cathode electrode is located on the upper side of the intermediate functional layer), and in reverse structure light emitting devices, thick may appear as an electron transport layer. In addition, since the material of the electron transport layer has relatively lower mobility than other transport materials provided in the intermediate functional layer (OS), the driving voltage due to the increase in the thickness of the electron transport layer adjacent to the cathode electrode in the structure having the reverse structure light emitting device The increase was a weak problem, but the white light emitting device of the present invention can solve this problem because the optical compensation layer 110 in contact with the cathode electrode 120 controls the cavity order.

In addition, in the white light emitting device ED of the present invention, the thickness between the cathode electrode 120 and the anode electrode 200 is reduced and the cavity order is reduced, thereby preventing deterioration of viewing angle characteristics. The cavity order means an order in which light emitting layers included in the intermediate functional layer can obtain optimal light emission. Being able to reduce the cavity order means that, in a structure having a plurality of light emitting layers in an intermediate functional layer, optimal light emitting characteristics can be obtained even when the position of the light emitting layer provided in each stack is a short distance from the cathode electrode. In order for the microcavity effect to occur only with the resonance effect in the intermediate functional layer (OS) between the cathode and anode electrodes, the light of the corresponding wavelength in the light emitting layer must be in a condition where constructive interference occurs between the anode and cathode electrodes, which is the intermediate function It is related to the total thickness of the layer OS, and the cavity order increases as the total thickness of the intermediate functional layer OS increases. In contrast, in the white light emitting device of the present invention, not only the intermediate functional layer (OS) but also the optical compensation layer 110 in contact with the cathode electrode 120 below the cathode electrode 120 compensates for the cavity of light emission, Together with the cathode electrode 120, the total thickness of the intermediate functional layer OS in the white light emitting device ED is reduced, thereby reducing the cavity order and reducing the driving voltage.

2 and 3 are cross-sectional views corresponding to one sub-pixel of a display device according to various embodiments of the present invention. 4 is a circuit diagram of one sub-pixel of the display device having the white light emitting device of FIG. 1, and FIG. 5 is a cross-sectional view schematically illustrating an optical functional layer of the display device according to the present invention.

As shown in FIGS. 2 and 3 , the display device of the present invention includes a substrate 100 having a plurality of sub-pixels each having a light emitting part EM and a non-emitting part NEM around the light emitting part, and on the substrate, A sub-pixel driving circuit (resistance except for the OLED in FIG. 4) provided in the non-emitting portion (NEM) of the sub-pixels, a planarization layer 240 covering the sub-pixel driving circuit, and on the planarization layer, at least the The optical compensation layers 110 and 410 provided to correspond to the light emitting unit EM of the sub-pixels, and the cathode electrode of FIG. 1 provided in each of the sub-pixels and in contact with the optical compensation layers 110 and 410. 120, an anode electrode 200, and a white light emitting device (ED) having an intermediate functional layer (OS) therebetween.

As shown in FIG. 4 , the sub-pixel driving circuit includes a switching transistor SW provided at an intersection between the scan line SL and the data line DL and the cathode electrode of the switching transistor SW and the white light emitting device ED. A driving transistor DR connected to (see 120 in FIG. 2 ) and a storage capacitor Cst connected between a connection node of the switching transistor SW and the driving transistor DR and a source electrode of the driving transistor DR. do. The anode electrode of the white light emitting device (ED) is connected to the driving power supply voltage line (VDL) to receive the driving power supply voltage (EVDD), and the source electrode of the driving transistor (DR) is connected to the base power supply voltage line (VSL) The base power supply voltage (EVSS) is supplied. The gate electrode of the switching transistor SW is connected to the scan line SL to receive a scan signal, and the driving transistor DR is connected to the switching transistor SW to receive a scan signal according to the signal transmitted from the switching transistor SW. turns on

In the display device of the present invention, as shown in FIG. 4 , the anode electrode of the light emitting element having the reverse structure is directly connected to the driving power supply voltage line VDL, and the cathode electrode is connected to the node D of the drain electrode of the driving transistor DR. When the driving transistor DR is turned on, when the driving power supply voltage EVDD is applied to the driving power supply voltage line VDL, a current path is formed in the white light emitting device ED to emit light, so that the driving transistor DR can emit light. Regardless of deterioration of DR, the white light emitting device ED can be driven, and therefore, a separate sense transistor for initialization or arrangement of a reference voltage line for applying an initialization voltage is not required, thereby reducing the configuration of the sub-pixel driving circuit. It can be simplified, and the light emitting part can be maximized by the simplified arrangement of the sub-pixel driving circuit part in the bottom emission method in which light is emitted through the substrate 100 .

In the display device according to the exemplary embodiment of the present invention, for example, the switching transistor SW and the driving transistor DR included in the sub-pixel are N-type. However, it is not limited to this, and one of the transistors SW and DR provided in the sub-pixel may be N-type and the other may be P-type, and in some cases, the switching transistor SW and the driving transistor DR All may be P-type.

These sub-pixels are supplied with a data signal and a scan signal from a data driver (not shown) and a scan driver (not shown) through a data line and a scan line, and when the switching transistor is switched, the driving power supply voltage line (VDL), white A current path is formed between the light emitting element ED, the driving transistor DR, and the base power supply voltage line VSS, so that the white light emitting element ED emits light.

Among the sub-pixel driving circuit parts, the driving transistor DR includes, for example, a gate electrode 210 on the substrate 100 and a gate insulating film 211 interposed between the gate electrode 210 as shown in FIG. 2 . It includes a semiconductor layer 215, a drain electrode 216a and a source electrode 216b provided on both sides of the semiconductor layer and spaced apart from each other.

The gate electrode 210 may include a metal such as aluminum (Al), chromium (Cr), copper (Cu), titanium (Ti), molybdenum (Mo), or tungsten (W). In addition, as shown, the gate electrode 210 is formed as a double layer, and at least one of the stacked layers prevents impurities or moisture entering from the lower side of the substrate 100 from affecting the semiconductor layer 215. It can be used as a barrier layer. The gate electrode 210 is not limited to a double layer, and may be formed as a single layer or a plurality of layers of three or more layers.

The drain electrode 216a and the source electrode 216b may be formed of the same metal layer. The drain electrode 216a and the source electrode 216b may also be formed as a single layer, but are not limited thereto and may be formed as multiple layers.

The semiconductor layer 215 may be any one of an oxide semiconductor layer, polysilicon, and amorphous silicon, or may be formed by stacking two or more layers of different layers among them. When the semiconductor layer 215 includes an oxide semiconductor layer and polysilicon, it may be formed through a crystallization process. The semiconductor layer 215 may further include an etch stop layer 218 to prevent over-etching of the channel portion. In some cases, the anti-etching layer 218 may be omitted.

Meanwhile, in the same process of forming the driving transistor DR, the scan line SL, the data line DL, the driving power supply voltage line VDL, the base power supply voltage line VSL, and the switching transistor SW described in FIG. and a storage capacitor Cst may be formed together. In addition, the base power voltage line VSL includes the first connection electrode 212 on the same layer as the gate electrode 210 of FIG. 2 , and the second connection electrode (on the same layer as the drain electrode 216a and the source electrode 216b). 217), the connection line pattern 220 may be provided in the non-emitting portion NEM of the sub-pixel SP on the substrate.

The switching transistor SW and the driving transistor DR may be protected by a protective layer 221 , and the connection line pattern 220 may be provided on the protective layer 221 .

In addition, a color conversion layer 230 is provided on the passivation layer 221 corresponding to at least the light emitting unit EM, and covers the color conversion layer 230, the passivation layer 221, and the connection line pattern 220 and is flattened. Layer 240 is provided. The planarization layer 240 may be formed of a planarizable organic material for a uniform surface of the white light emitting device ED to be formed thereon.

An array 1000 includes a sub-pixel driving circuit such as a driving transistor DR, insulating layers 211 , 221 , 240 , and a color conversion layer 230 formed on the substrate 100 .

In the display device of the present invention, optical compensation layers 110 and 410 are provided on the planarization layer 240 to correspond to at least the light emitting unit EM. The optical compensation layers 110 and 410 may be formed corresponding to only the light emitting part EM, or partially or entirely extending to the entire light emitting part EM and the non-emitting part NEM around the light emitting part EM. Correspondingly can be formed.

A contact hole CT is provided in the optical compensation layers 110 and 410 and the planarization layer 240 to expose a part of the drain electrode 216a, and the cathode electrode 120 is provided through the contact hole CT. ) is connected to the drain electrode 216a and is formed on the planarization layer 240 . In the example shown in FIG. 2 , the contact hole CT is continuously formed in a common hole shape in the planarization layer 240 and the optical compensation layer 110 . In addition, when the optical compensation layer 110 is located only in the light emitting part EM, the contact hole CT located in the non-emitting part NEM and the optical compensation layer 110 have a non-overlapping relationship, in this case In this case, the contact hole CT may be provided only in the planarization layer 240 .

A bank 190 may be provided on the array substrate 1000 to expose the light emitting portion EM of the sub-pixels. The bank 190 may overlap the cathode electrode 120 located in a part of the non-emission portion NEM and may be formed thereon.

In the display device shown in FIG. 2 , the optical compensation layer 110 is a transparent insulating film, and in this case, the optical compensation layer 110 can compensate for the cavity without causing other electrical effects outside the white light emitting device ED. can For electrical connection between the cathode electrode 120 and the drain electrode 216a, the optical compensation layer 110 may be removed and provided in the contact hole CT area. 2, in order to reduce the connection resistance between the cathode electrode 120, which is a transparent electrode, and the drain electrode 216a in the contact hole CT, a metal component is placed between the cathode electrode 120 and the drain electrode 216a. A metal of the same layer as the connection line pattern 220 may be further included. The optical compensation layer 110 has a higher refractive index than the cathode electrode 120, so that there is no light loss at the interface between the cathode electrode 120 and the optical compensation layer 110, from the cathode electrode 120 through the optical compensation layer 110 to the lower side. to increase the light emission efficiency.

In the display device shown in FIG. 3 , the optical compensation layer 410 is a transparent electrode different from the cathode electrode 120 . For example, the cathode electrode 120 may be indium tin oxide (ITO), and the optical compensation layer 410 may be indium zinc oxide (IZO). However, the cathode electrode 120 and the optical compensation layer 410 are not limited to the presented example, and if the optical compensation layer 410 lower than the cathode electrode 120 has a higher refractive index, it can be changed to another type of transparent electrode. there is. In some cases, even if the cathode electrode 120 and the optical compensation layer 410 include the same metal component, the refractive index may be changed by changing the component ratio.

At this time, the optical compensation layer 410 is a transparent electrode having a higher refractive index than the cathode electrode 120, and prevents light loss at the interface between the optical compensation layer 410 and the cathode electrode 120, and at the cathode electrode 120 This is to increase the emission efficiency of light downward through the optical compensation layer 410 .

In the display devices of FIGS. 2 and 3 , a refractive index difference between the optical compensation layers 110 and 410 and the cathode electrode 120 may be 0.1 or more and 0.4 or less. In addition, the optical compensation layers 110 and 410 may have a refractive index similar to or higher than the average refractive index of the intermediate functional layer OS to compensate for the optical cavity.

In the display device of FIG. 3 , since the optical compensation layer 410 is made of a transparent electrode and has conductivity, it may be integrally formed with the cathode electrode 120 in the same process. Therefore, as shown in FIG. 3 , the optical compensation layer 410 and the cathode electrode 120 may have the same width, and the drain electrode 216a of the driving transistor DR may be directly connected to the optical compensation layer 410 . At this time, the cathode electrode 120 is electrically connected to the drain electrode 216a through the optical compensation layer 410 and receives an electrical signal from the driving transistor DR. In this case, the optical compensation layer 410 may electrically connect the cathode electrode 120 and the driving transistor DR. Since the cathode electrode 120 and the optical compensation layer 410 are doubly connected, an increase in electrical resistance may be prevented at a connection portion of the contact hole CT with the drain electrode 216a.

In the display device of FIG. 3 , the widths of the optical compensation layer 410 and the cathode electrode 120 may be varied.

The display device according to FIG. 3 has the same functional characteristics as the display device according to FIG. 2 in the function of adjusting the cavity of the intermediate functional layer (OS) of the optical compensation layer 410, and the upper part of the optical compensation layer 410 has a white color. As described above, the light emitting element ED may have the same effect of reducing the driving voltage and reducing the cavity order by reducing the thickness of the entire intermediate functional layer OS due to the provision of the optical compensation layer 410 . As shown in FIGS. 1 to 5 , in the display device of the present invention, a driving current is generated when voltage is applied to the cathode electrode 120 and the anode electrode 200 respectively. When the anode electrode 200 is a reflective electrode and the cathode electrode 120 is a transparent electrode, when light is generated in the intermediate functional layer OS, resonance occurs between the electrodes 200 and 120 in the intermediate functional layer OS. The converted light finally passes to the cathode electrode 120, and the light passing through the cathode electrode 120 passes through the optical compensation layers 110 and 410 and the color conversion layer 230, and the color conversion layer 230 The light according to the wavelength selectively transmitted in may be transmitted to the side of the substrate 100 .

The anode electrode 200 may include at least one of aluminum, silver, gold, and magnesium, or may be an aluminum alloy, a silver alloy, a gold alloy, or a magnesium alloy.

Meanwhile, in the display device including the white light emitting device (ED) of the present invention, the optical compensation layers 110 and 410 are transparent insulating films or transparent electrodes, which means that the optical compensation layers 110 and 410 are the white light emitting devices (ED). This is to compensate for the optical cavity without causing other electrical influences from the outside. In addition, the optical compensation layers 110 and 410 are formed to a thickness of 1000 Å or more to 3000 Å or less to compensate cavities in all of the red, green, blue, and white sub-pixels provided on the substrate 100 . More preferably, the optical compensation layers 110 and 410 are transparent insulating films or transparent electrodes having a thickness of 1100 Å to 2400 Å.

The cathode electrode 120 directs light emitted from each light emitting layer provided between the cathode electrode 120 and the anode electrode 200 to the cathode electrode 120 side, and for transparency of the cathode electrode 120, The thickness of the optical compensation layers 110 and 410 is less than 1000 Å, more preferably, the thickness of the cathode electrode 120 may be 100 Å to 700 Å.

The optical compensation layers 110 and 410 have a refractive index equal to or greater than the average refractive index of the intermediate functional layer OS in order to increase the light output effect of the white light emitting device ED without causing total internal reflection. It may be made of a transparent insulating film or a transparent electrode having.

The optical compensation layers 110 and 410 have higher refractive indices than the cathode electrode 120 but have similar refractive indices with a difference of 0.4 or less. Accordingly, the optical compensation layers 110 and 410 have the first Light passing through the cathode electrode 120 may be emitted along the traveling direction without being substantially reflected from the surface SF1 . In addition, in the display device of FIG. 2 , for example, the optical compensation layer 110 is a material having high transmittance without internal absorption of light, and may include silicon nitride (SiNx) as a component. In the display device of FIG. 3 , the optical compensation layer 410 is made of a transparent electrode having high transmittance without internal absorption of light and having a higher refractive index than the adjacent cathode electrode 110, for example, indium zinc oxide (IZO). can In this case, the cathode electrode 110 may be indium tin oxide (ITO).

In some cases, the optical compensation layer may be replaced with a material having low light absorption, a refractive index equal to or greater than the average refractive index of the intermediate functional layer OC, and little reflectance on the surface in contact with the cathode electrode 120 . Hereinafter, the reason for having the optical compensation layer in the white light emitting device and the display device of the present invention and the effect of the specific thickness of the optical compensation layer will be examined through experiments.

6A and 6B are cross-sectional views showing white light emitting devices used in the first and second experimental examples, and FIGS. 7A to 7C are cross-sectional views showing third to fifth experimental examples. 8 is a cross-sectional view showing a sixth experimental example. 9 is a graph showing white spectra of the first to sixth experimental examples.

FIG. 6A is a first experimental example, which has a white light emitting device having a forward structure, and has an inverted structure of FIG. 1 described above. The white light emitting device according to the first experimental example includes an anode electrode (Anode), a hole injection layer (HIL), a first hole transport layer (HTL1), a first blue light emitting layer (B EML1) on a substrate (SUB) 10, First electron transport layer (ETL1), first charge generating layer (CGL1), second hole transport layer (HTL2), red light emitting layer (R EML), yellow green light emitting layer (YG EML), green light emitting layer (G EML), second electron The transport layer ETL2, the second charge generation layer CGL2, the third hole transport layer HTL3, the second blue light emitting layer B EML2, the third electron transport layer ETL3, the electron injection layer EIL, and the cathode electrode ) is formed in the order of arrangement. In the white light emitting device of the pure structure according to the first experimental example, the first and second charge generation layers CGL1 and CGL2 have an n-type charge generation layer (n CGL) on the lower side and a p-type charge generation layer on the upper side ( p CGL) may have a stacked structure. The white light emitting device having a net structure according to the first experimental example emits light toward the substrate (SUB) 10.

In the first experimental example (Ex1), the anode located on the lower side was ITO, and the cathode electrode located on the upper side opposite to the anode electrode was made of aluminum (Al).

In the second to sixth experimental examples (Ex2 to Ex6), the cathode electrode located on the lower side was ITO, and the anode electrode located on the upper side opposite to the anode electrode was made of aluminum (Al).

FIG. 6B is a white light emitting device having an inverse structure known as a second experimental example, and has the same layer configuration as the intermediate functional layer (OS) described in FIG. 1 . However, the white light emitting device according to the second experimental example emits light only through resonance between the cathode and the anode, and emits light toward the substrate (SUB) 10 below the cathode. do.

A white light emitting device according to the second experimental example includes a cathode electrode, an electron injection layer (EIL) 25, a first electron transport layer (ETL1) 30, and a first blue light emitting layer on a substrate (SUB) 10. (B EML1) (33), a first hole transport layer (HTL1) (35), a first charge generation layer (CGL1) (40), a second electron transport layer (ETL2) (50), a red light emitting layer (R EML) (53) ), yellow-green light emitting layer (YG EML) 54, green light emitting layer (G EML) 55, second hole transport layer (HTL2) 57, second charge generation layer (CGL2) 60, third electron transport layer (ETL3) 71, the second blue light emitting layer (B EML2) 73, the third hole transport layer (HTL3) 75, the hole injection layer (HIL) 77 and the anode electrode (Anode) 80 formed in sequence. The first and second charge generating layers CGL1 (40) and CGL2 (60) include p-type charge generating layers (p CGL) 40a and 60a on the lower side and n-type charge generating layers (n CGL) on the upper side, respectively. (40b, 60b) may have a stacked structure. The white light emitting device having an inverse structure according to the second experimental example emits light toward the substrate (SUB) 10.

The third to fifth experimental examples (Ex3, Ex4, and Ex5) according to FIGS. 7A to 7C have a white light emitting device structure with an inverse structure of the structure of FIG. 6B, but the total thickness of the intermediate functional layer (OS) and the substrate (SUB) ) and the thickness of the cathode electrode 20 in contact with each other.

As shown in FIG. 8, in the white light emitting device with an inverse structure according to the sixth experimental example (Ex6), the intermediate functional layer (OS) shown in FIG. 1 is interposed between the cathode 120 and the anode 200. and a structure of a white light emitting device having an optical compensation layer (OCL) between a substrate (SUB) and a cathode electrode (Cathode). In the following experiment, a silicon nitride film was used as the optical compensation layer (OCL).

In the first experimental example (Ex1) and the second experimental example (Ex2), there is a difference in whether the white light emitting device has a pure structure or an inverse structure, and in the first experimental example (Ex1), the lowermost electrode is an anode electrode of ITO. A transparent electrode is used, and the lowermost electrode in the second experimental example (Ex2) uses an ITO transparent electrode as a cathode electrode. In each of the first and second experimental examples (Ex1 and Ex2), the lowermost ITO transparent electrode was set to the same thickness of 1200 Å.

In the white light emitting device ED of the first experimental example Ex1, the anode electrode is connected to the driving transistor DR, and the cathode electrode is connected to the base power supply voltage line. In addition, one side of the driving transistor DR is connected to the driving power supply voltage line VDL, and the other side is connected to the anode electrode of the white light emitting device ED. In this case, turn-on of the white light emitting device ED is affected by the driving characteristics of the driving transistor DR. Therefore, the white light emitting device ED of the forward structure is composed of the white light emitting device ED and the driving transistor DR in order to detect a change in threshold voltage due to deterioration of the driving transistor DR, compared to the white light emitting device of the reverse structure. A deterioration detection means such as a sensor transistor may be further provided at the connected node, and a complicated pixel circuit in a sub-pixel is required, which may decrease an aperture ratio.

On the other hand, as shown in FIG. 4, in the white light emitting devices of the inverse structure of the second to sixth experimental examples (Ex2 to Ex6), when the driving transistor DR is turned on, the driving power supply voltage EVDD When applied, a current path is formed in the white light emitting device ED to emit light, so the white light emitting device ED can be driven regardless of degradation of the driving transistor DR. Since arrangement of a sense transistor or a reference voltage line for applying an initialization voltage is not required, the configuration of the sub-pixel driving circuit can be simplified, and the arrangement of the sub-pixel driving circuit has been simplified from the bottom emission method in which light is emitted through the substrate 100. There is an advantage of maximizing the light emitting part. The second experimental example (Ex2) to the sixth experimental example (Ex6) are white light emitting devices having an inverse structure, and the thicknesses of the first electron transport layer and the cathode electrode in contact with the cathode electrode are compared, and the difference in effect is shown in Table 1. was In the second experimental example (Ex2), the thicknesses of the first electron transport layer and the cathode electrode are 910 Å and 1200 Å, respectively, and in the third experimental example (Ex3), the thicknesses of the first electron transport layer and the cathode electrode are 500 Å and 1658 Å, respectively. In Example 3 (Ex3), the thickness of the first electron transport layer of the intermediate functional layer (OS) was reduced and the thickness of the cathode electrode (Cathode) was increased compared to the second Example (Ex2). In the fourth experimental example (Ex4), the thicknesses of the first electron transport layer (ETL1) and the cathode electrode (ITO) were 100 Å and 2090 Å, respectively, compared to the third experimental example (Ex3) in order to reduce the driving voltage. 1 The thickness of the electron transport layer (ETL1) is reduced and the thickness of the cathode electrode (ITO) is increased. In the fifth experimental example (Ex5), the thickness of the first electron transport layer and the cathode electrode was 100 Å and 440 Å, respectively, which compared to the fourth experimental example (Ex4), the optical change when the thickness of the cathode electrode was reduced. would have looked

Compared to the above-described fifth experimental example (Ex5), the white light emitting device of the sixth experimental example (Ex6) has a difference in that the thickness of the cathode electrode 120 is reduced and the optical compensation layer (OCL) 110 is further included. Thus, the thickness of the first electron transport layer was 100 Å, the thickness of the cathode electrode was 330 Å, and the thickness of the optical compensation layer (OCL) was 1580 Å.

Meanwhile, in the first experimental example (Ex1), the thickness of the intermediate functional layer (OS) between the anode electrode and the cathode electrode (Cathode) is 3470 Å, and in the second experimental example (Ex2), the first experimental example (Ex1) The thickness of the intermediate functional layer (OS) between the cathode electrode (Cathode) and the anode electrode (Anode) is 4280 Å by increasing the cavity order by increasing the thickness of the first electron transport layer. The third experimental example (Ex3) has a lower thickness of the first electron transport layer than the second experimental example (Ex2), and the total thickness of the intermediate functional layer (OS) is 3870 Å. In the fourth to sixth experimental examples (Ex4 to Ex6), the total thickness of the intermediate functional layer (OS) was 3470 Å. This is because the thickness of the first electron transport layer ETL1 is reduced by 400 Å in the fourth to sixth experimental examples (Ex4 to Ex6) compared to the third experimental example (Ex3).

In addition, Table 1 shows the driving voltage, red efficiency (R efficiency), green efficiency (G efficiency), blue efficiency (B efficiency), and white efficiency (W efficiency) in each experimental example based on the first experimental example (Ex1). , and the comparison value was displayed.

structure (thickness) [Å] Driving
Voltage
(vs Ex1)[V] R efficiency
(%) G efficiency
(%) B efficiency
(%) W efficiency
(%) viewing angle
Deviation
(Δu'v') ETL1 ITO
[Anode/
Cathode] OCL Ex1 100 1200
[Anode] - 0 100 100 100 100 0.0226 Ex2 910 1200 [Cathode] - +2.2 107 98 99 101 0.0253 Ex3 500 1658 [Cathode] - 0 100 94 99 97 0.0247 Ex4 100 2090 [Cathode] - -1.1 96 90 96 93 0.0242 Ex5 100 440 [Cathode] - -1.1 114 105 90 105 0.0252 Ex6 100 330 [Cathode] 1580 -1.1 109 102 101 104 0.0198

As shown in Table 1, the second experimental example (Ex2), which reverses the structure of the first experimental example (Ex1), has an increased thickness of the first electron transporting layer in contact with the cathode electrode, so the existence of the increased first electron transporting layer and the first There is a problem in that the driving voltage is increased compared to the first experimental example (Ex1) due to the low mobility of the electron transport layer. In the case of the third experimental example (Ex3), in which the thickness of the cathode electrode is increased in order to improve the problem of the increase in the driving voltage of the reverse structure white light emitting device of the second experimental example (Ex2), the first experimental example (Ex1) Although the driving voltage characteristics are shown, the green efficiency, blue efficiency, and white efficiency are all lowered, and as shown in Table 1, the viewing angle deviation generated when looking at an angle of 45 degrees compared to when looking at the front of the white color is the first experimental example (Ex1) It can be seen that the contrast increases.

On the other hand, compared to the third experimental example (Ex3), in the fourth to sixth experimental examples (Ex4 to Ex6) reducing the first electron transport layer to 1/5, the driving voltage is 1.1 in common compared to the first experimental example (Ex1). It can be seen that V is lowered and the driving voltage is reduced. However, it can be seen that the fourth experimental example (Ex4) and the fifth experimental example (Ex5) have a larger viewing angle deviation of white color than the first experimental example (Ex1). In particular, as shown in FIG. 9 , in the fourth experimental example (Ex4), the efficiencies of red, green, blue, and white are all low, so it can be seen that all of the color efficiencies are low. On the other hand, in the fifth experimental example (Ex5), the thickness of the cathode electrode was reduced compared to the fourth experimental example (Ex4), so that the efficiency of red, green, and white was improved, but the efficiency of blue was significantly lowered and the viewing angle deviation was greater. You can check. This is because the thin cathode electrode and the first electron transport layer (ETL1) are in contact, the first blue light emitting layer is located at a short distance from the lower surface of the cathode electrode, and light emission is determined only by resonance between the cathode electrode and the anode electrode of the white light emitting device. It is understood that the blue efficiency was not secured.

On the other hand, in the sixth experimental example (Ex6) according to an embodiment of the present invention, an optical compensation layer of a transparent insulating film such as SiNx is provided under the cathode electrode, so that the cathode electrode can be maintained even when the thin cathode electrode and the first electron transport layer are provided. The light that passes through is compensated for the cavity in the optical compensation layer on the lower side, and the light emission efficiency is increased and emitted, and the red, green, blue, and white efficiencies are all improved compared to the inverse structure white light emitting device of the second experimental example (Ex2). In addition, it can be confirmed that the white light emitting device of the first experimental example (Ex1) having a pure structure is also improved. In addition, the sixth experimental example (Ex6) according to an embodiment of the present invention has a viewing angle deviation of 0.0198, which is the lowest compared to all experimental examples, as shown in Table 1, so it can be expected that the amount of abnormal visibility according to the viewing angle change is the smallest. This means that the viewer recognized the best picture quality in the sixth experimental example (Ex6) compared to other experimental examples.

On the other hand, in the experiment of Table 1, as in the white light emitting device of the structure of FIG. In the first experimental example (Ex1) or in the second to fifth experimental examples (Ex2 to Ex5), which have an inverse white light emitting structure but do not apply an optical compensation layer, efficiency and voltage characteristics by varying the thickness of the cathode electrode and the electron transport layer looked at, etc.

Hereinafter, with reference to Table 2, effects in the seventh experimental example (Ex7) in which the optical compensation layer is a transparent electrode different from the cathode electrode will be examined.

In the following experiments, the anode electrode and the cathode electrode made of ITO, which is the lower electrode, were each changed to 1100 Å in the first experimental modification (Ex1a) of the pure structure and the second experimental modification (Ex2a) of the inverse structure.

The seventh experimental example (Ex7) follows the configuration of the white light emitting device of FIG. 1 described above, and differs from the aforementioned sixth experimental example (Ex6) in that the material of the optical compensation layer is a transparent electrode of IZO (Indium Zinc Oxide). and all other features are the same.

In the seventh experimental example (Ex7), on the substrate 100, a transparent electrode of IZO is sequentially formed to a thickness of 1300 Å as an optical compensation layer (OCL), and then, a transparent electrode of ITO is formed as a cathode electrode 120 to a thickness of 550 Å. is formed to a thickness of , and then a first electron transport layer is formed to a thickness of 100 Å. Also in the seventh experimental example (Ex7), the total thickness of the intermediate functional layer (OS) was set to 3470 Å, as in the third to sixth experimental examples (Ex6).

structure (thickness) [Å] Driving
Voltage
(vs Ex1a)[V] R efficiency
(%) G efficiency
(%) B efficiency
(%) W efficiency
(%) ETL1 ITO
[Anode/
Cathode] OCL Ex1a 100 1100
[Anode] - 0 100 100 100 100 Ex2a 910 1100 [Cathode] - +2.2 107 98 99 101 Ex3 500 1658 [Cathode] - 0 100 94 99 97 Ex7 100 550 [Cathode] 1300 -1.1 99 98 109 116

As shown in Table 2, the white light emitting device of the seventh experimental example (Ex7) has an advantage in that the driving voltage is reduced by 1.1V compared to the standard white light emitting device of the first experimental modification (Ex1a). This is an effect obtained by reducing electrical resistance by connecting the optical compensation layer of the transparent electrode to the lower side of the reduced cathode electrode. In addition, the white light emitting device of the seventh experimental example (Ex7) shows a similar level of red and green efficiencies compared to the white light emitting device of the first experimental modification (Ex1a), and the blue efficiency is significantly improved by 109%. can know In particular, in the case of the white transmission part not using a color filter, the white efficiency is remarkably improved to a level of 116% by using the double transparent electrode of the cathode electrode and the optical compensation layer.

On the other hand, the above-described first to seventh experimental examples (Ex1 to Ex7) are experiments from the viewpoint of a white light emitting device. Since insulating films including thin film transistors are added to the lower side of the light emitting part of the white light emitting element in the display device, in the following experiments, the white sub-pixel is a display device to which the experiment of structures in which insulating films are added to the lower side of the cathode electrode and/or the optical compensation layer is applied. Efficiency and viewing angle characteristics of

In the following experiment, a first interlayer insulating film (INE1), a second interlayer insulating film (INE2) and a planarization layer of inorganic insulating film components are sequentially placed between the white light emitting device of the pure structure of FIG. 6A, the substrate (SUB), and ITO (anode electrode). (OC) is further provided to make the first experimental modification (Ex1b), and between the white light emitting element of the inverse structure of FIG. A second interlayer insulating film (INE2) and a planarization layer (OC) are further provided as a second experimental modification (Ex2b).

10A to 10C are cross-sectional views showing eighth to tenth experimental examples, and FIG. 11 is a cross-sectional view showing an eleventh experimental example. 12 is a graph showing white spectra of first and second experimental modifications and eighth to eleventh experimental examples.

The 8th to 10th experimental examples (Ex8, Ex9, and Ex10) according to FIGS. 10a to 10c have a white light emitting device structure inverse to the structure of FIG. 6b, and, like the 3rd to 5th experimental examples described above, intermediate functions There is a difference between the total thickness of the layer OS and the thickness of the cathode 20 in contact with the substrate SUB.

As shown in FIG. 11, the reverse structure white light emitting device according to the eleventh experimental example (Ex11) has an intermediate functional layer (OS) shown in FIG. 1 between a cathode and an anode (200), and optical A structure of a white light emitting device having a compensation layer (OCL) at a lower side in contact with a cathode electrode is shown.

In the first modified example (Ex1b) and the second modified example (Ex2b), there is a difference in whether the white light emitting device has a pure structure or an inverted structure, and in the first modified example (Ex1b), the lowermost electrode is the anode electrode. In the second experimental modification (Ex2b), the lowermost electrode uses an ITO transparent electrode as a cathode electrode. In each of the first and second experimental modifications (Ex1b and Ex2b), the lowermost ITO transparent electrode was set to the same thickness of 1200 Å.

The second experimental modification (Ex2b) and the eighth to eleventh experimental examples (Ex8 to Ex11) are white light emitting devices having an inverse structure, and the thicknesses of the first electron transport layer and the cathode electrode in contact with the cathode electrode are compared and are shown in Table 3. showed up In the second experimental modification (Ex2b), the thickness of the first electron transport layer and the cathode electrode is 910 Å and 1200 Å, respectively, and in the eighth experimental example (Ex8), the thickness of the first electron transport layer and the cathode electrode is 500 Å and 1658 Å, respectively. In the eighth experimental example (Ex8), compared to the second experimental modification (Ex2b), the functional layer of the intermediate functional layer (OS) is reduced and the thickness of the cathode electrode (Cathode) is increased. In the ninth experimental example (Ex9), the thicknesses of the first electron transport layer (ETL1) and the cathode electrode (ITO) were 100 Å and 2090 Å, respectively, compared to the eighth experimental example (Ex8) in order to reduce the driving voltage. 1 The thickness of the electron transport layer (ETL1) is reduced and the thickness of the cathode electrode (ITO) is increased. In the 10th experimental example (Ex10), the thickness of the first electron transport layer and the cathode electrode was 100 Å and 440 Å, respectively, and this compared to the 9th experimental example (Ex-9), the optical change when the cathode electrode was reduced would have looked

Compared to the above-described tenth experimental example (Ex10), the white light emitting device of the eleventh experimental example (Ex11) has a difference in that the thickness of the cathode electrode 120 is reduced and the optical compensation layer (OCL) 110 is further provided. Thus, the thickness of the first electron transport layer was 100 Å, the thickness of the cathode electrode was 330 Å, and the thickness of the optical compensation layer (OCL) was 1580 Å.

In the 8th to 11th experimental examples (Ex8, Ex9, Ex10, and Ex11), the first interlayer insulating film is formed on the lower side of the ITO (cathode electrode) as in the first modified example (Ex1b) and the second modified example (Ex2b) described above. (INE1), a second interlayer insulating film (INE2) and a planarization layer (OC) are applied.

The first interlayer insulating layer INE1 may be the gate insulating layer 211 of FIG. 2 and may further include a buffer layer in some cases. In the experiment, the first interlayer insulating film (INE1) was applied by stacking a silicon oxide film (SiOx) with a thickness of 3000 Å and a silicon nitride film (SiNx) with a thickness of 1000 Å. The second interlayer insulating film INE2 may be the passivation film 221 of FIG. 2 , and in the experiment, SiOx was applied to a thickness of 1800 Å. In addition, the thickness of the planarization layer OC was 2900 nm.

In addition, Table 3 shows the driving voltage, red efficiency (R efficiency), green efficiency (G efficiency), blue efficiency (B efficiency), and white efficiency (W efficiency) in each of the experimental examples (Ex1b). The comparative value was displayed as a reference.

structure (thickness) [Å] Driving
Voltage
(vs Ex1b)[V] R efficiency
(%) G efficiency
(%) B efficiency
(%) W efficiency
(%) viewing angle
Deviation
(Δu'v') ETL1 ITO
[Anode/
Cathode] OCL Ex1b 100 1200
[Anode] - 0 100 100 100 100 0.0285 Ex2b 910 1200 [Cathode] - +2.2 104 101 86 101 0.0285 Ex8 500 1658 [Cathode] - 0 96 100 99 98 0.0247 Ex9 100 2090 [Cathode] - -1.1 91 98 96 95 0.0193 Ex10 100 440 [Cathode] - -1.1 104 98 109 101 0.0152 Ex11 100 330 [Cathode] 1580 -1.1 106 103 103 104 0.0187

The results shown in Table 3 and FIG. 12 apply the insulating film included in the array 1000 of FIG. 2 or 3 to the lower part of the white light emitting element in a structure in which an insulating film is actually required under the white light emitting element in the display device. In this case, as shown in Table 3, both the first experimental modification (Ex1b) and the second experimental modification (Ex2b) show that the viewing angle deviation characteristics are larger than those of the first and second experimental examples (Ex1 and Ex2), This can be expected to cause problems in visibility due to color deviation when the known white light emitting device of pure structure and white light emitting device of reverse structure are applied to an actual display device. The second experimental modification (Ex2b) in which the structure of the light emitting device is reversed has the existence of an increased first electron transport layer and low mobility of the first electron transport layer because the thickness of the first electron transport layer in contact with the cathode electrode is increased. There is a problem in that the driving voltage is increased by 2.2V compared to the first experimental modification (Ex1b).

In the case of the eighth experimental example (Ex8) in which the thickness of the cathode electrode is increased in order to improve the problem of the increase in the driving voltage of the white light emitting device with the inverse structure of the second experimental modification (Ex2b), the first experimental modification (Ex1b) However, it can be seen that the red efficiency, blue efficiency, and white efficiency are all lowered.

On the other hand, compared to the eighth experimental example (Ex8), the driving voltage is common in the ninth to eleventh experimental examples (Ex9 to Ex11) reducing the thickness of the first electron transport layer (ETL1) to 1/5. Compared to the example (Ex1b) and the eighth experimental example (Ex8), it can be seen that the effect of reducing the driving voltage is lowered by 1.1V. However, it can be seen that the ninth experimental example (Ex9) and the tenth experimental example (Ex10) have poor color efficiency, as shown in Table 3 and FIG. 12 . In addition, in the case of the tenth experimental example (Ex10), the green efficiency is decreased and the blue efficiency is relatively improved, but the efficiency increase is large, and color discrimination defects may appear when white is displayed.

On the other hand, in the eleventh experimental example (Ex11) according to an embodiment of the present invention, the optical compensation layer is provided under the cathode, so that even when the thin cathode electrode and the first electron transport layer are provided, light passing through the cathode electrode In the lower optical compensation layer, the cavity is compensated and the light emission efficiency is increased and emitted, so that the red, green, blue and white efficiencies are all improved compared to the inverse structure white light emitting device of the second experimental modification (Ex2b), but also It can be confirmed that the white light emitting device of the first experimental modification (Ex1b) of the structure is also improved. In addition, it can be expected that the degree of improvement in red, green, blue, and white efficiencies is similar, so that display is possible while maintaining the balance for each color during white display. In addition, the 11th experimental example (Ex11) according to an embodiment of the present invention has a viewing angle deviation of 0.0187, and it can be seen that there is a viewing angle improvement effect compared to the structure of the white light emitting device except for the insulating film described in Table 1 and FIG. there is.

Hereinafter, a display device according to another exemplary embodiment of the present invention will be described.

13 is a cross-sectional view of a display device according to another exemplary embodiment, and FIGS. 14A to 14D are graphs illustrating a relationship between red, green, blue, and white efficiencies and a thickness of a light compensation layer.

13 shows a display device according to another embodiment of the present invention to which an optical compensation layer is applied so as to have an optimal cavity compensation effect in each sub-pixel displaying a different color.

13 , in a display device according to another embodiment of the present invention, a substrate 100 includes a red sub-pixel R_SP, a green sub-pixel G_SP, a blue sub-pixel B_SP, and a white sub-pixel W_SP. and between the planarization layer 240 and the substrate 100, a red conversion layer 230R, a green conversion layer 230G, and a blue conversion layer 230G correspond to the red sub-pixel, the green sub-pixel, and the blue sub-pixel, respectively. A conversion layer 230B is further included.

The cathode electrode 120 of the white light emitting device ED is connected to the drain electrode 216a of the driving transistor DR through the contact hole CT passing through the planarization layer 240 and the passivation layer 221 .

In a display device according to another embodiment of the present invention, optical compensation layers 310a, 310b, 310c, and 310d having different thicknesses are provided in sub-pixels emitting different lights to compensate for optimum cavities for each sub-pixel. .

Descriptions of the same parts as those in FIG. 2 or 3 are omitted.

14A to 14D show an eleventh experimental example (Ex11) shown in FIG. 11 using a silicon nitride film as an optical compensation layer, and evaluating the color efficiency of each sub-pixel by varying the thickness of the optical compensation layer.

As shown in FIG. 14A, the red conversion efficiency for the red pixel is that the red conversion layer is further provided below the optical compensation layer, and when the thickness of the optical compensation layer is changed from 190 nm (1900 Å) to 240 nm (2400 Å), the efficiency is the first. It is improved by more than 125% compared to the experimental modification (Ex1b). Among the ranges evaluated, it can be seen that there is an efficiency improvement of 132% or more in the range of 210 nm to 222 nm.

As shown in FIG. 14B, the green efficiency for the green pixel is that the green conversion layer is further provided below the optical compensation layer, and when the thickness of the optical compensation layer is changed from 110 nm (1100 Å) to 160 nm (1600 Å), the efficiency is the first. It is improved by more than 101% compared to the experimental modification (Ex1b). Among the evaluated ranges, it can be seen that there is an efficiency improvement of 106.8% or more in the range of 126 nm to 140 nm.

As shown in FIG. 14c, the blue efficiency for the blue pixel is that the blue conversion layer is further provided below the optical compensation layer, and when the thickness of the optical compensation layer is changed from 150 nm (1500 Å) to 200 nm (2000 Å), the efficiency is the first. It is improved by more than 99% compared to the experimental modification (Ex1b). Among the evaluated ranges, it can be seen that there is an efficiency improvement of 102.5% or more in the range of 170 nm to 180 nm.

As shown in FIG. 14D, the white pixel does not have a color conversion layer, and has similar results to the eleventh experimental example (Ex11) examined in Table 2 above. That is, when the thickness of the optical compensation layer is changed from 130 nm (1300 Å) to 180 nm (1800 Å), the efficiency is improved by 101.6% or more compared to the first modified example (Ex1b). Among the evaluated ranges, it can be seen that there is an efficiency improvement of 103.5% or more in the range of 144 nm to 162 nm.

As such, the optical compensation layers 310a, 310b, 310c, and 310d may have different thicknesses for optimum efficiency for each color pixel, and the optical compensation layers 310a, 310b, and 310c may have different thicknesses for optimum efficiency of each sub-pixel. , 310d) may have different thicknesses for each sub-pixel of each color. Further, the thickness of the optical compensation layer may increase in order of thicknesses of the green sub-pixel G_SP, the white sub-pixel W_SP, the blue sub-pixel B_SP, and the red sub-pixel (310b<310d< 310c < 310a).

Meanwhile, FIGS. 14A to 14D are according to an exemplary embodiment, and when the optical compensation layer is provided at a thickness level of 1100 Å to 2400 Å, the cavity compensation effect for each color of each sub-pixel is obtained, so it may be formed with the same thickness. In some cases, the optical compensation layer may be the same in two of the four sub-pixels and the same in the remaining sub-pixels. Alternatively, the difference in thickness of the optical compensation layer may be given by dividing the three sub-pixels into one other sub-pixel.

In a structure in which the display device has only red, green, and blue sub-pixels without white sub-pixels, the optical compensation layer may apply different thicknesses to the three sub-pixels or make two of the plurality of sub-pixels the same as the other one. .

15 is a cross-sectional view showing a white light emitting device according to another embodiment of the present invention.

As shown in FIG. 15, the white light emitting device according to another embodiment of the present invention is a light emitting device having an inverse structure, and includes four or more stacks (S1) in an intermediate functional layer (OS) between a cathode electrode (Cathode) and an anode electrode (Anode). , S2, S3, ..Sn).

The plurality of stacks S1 , S2 , S3 , ..Sn included in the intermediate functional layer OS are each divided into charge generating layers CGL1 , CGL2 , CGL3 , .., and each may include a light emitting layer. The first stack S1 includes a first blue light emitting layer B EML1 to emit blue light, and the second stack S2 includes a phosphorescent light emitting unit P EMLU that emits light with a longer wavelength than blue. . As described in FIG. 1 , the phosphorescent light emitting unit P EMLU may include a red light emitting layer R EML, a yellow green light emitting layer YG EML, and a green light emitting layer G EML. The phosphorescent light emitting unit P EMLU may include at least two or more of the light emitting layers having a longer wavelength than blue.

The third stack S3 may include a blue light emitting layer B EML2 and a non-blue light emitting layer NB EML contacting the blue light emitting layer B EML2 and emitting different colors. In this case, a non-blue light emitting layer (NB EML) is included to increase the white light emitting efficiency and the white light emitting efficiency of the white light emitting device.

As shown in FIG. 15, in the third stack S3, the non-blue light emitting layer NB EML and the blue light emitting layer B EML2 may be formed in that order. The blue light emitting layer NB EML may be positioned on the upper side.

An additional stack Sn may be further added to the third stack S3 to compensate for insufficient color efficiency when white light is emitted.

As described in FIG. 3 , the white light emitting device shown in FIG. 15 is formed so that the optical compensation layer 110 or 410 and the cathode electrode 120 have the same width.

In this case, the optical compensation layer 110 may be a transparent insulating film or a transparent electrode having a refractive index greater than that of the cathode electrode 120 by 0.1 to 0.4 or less.

In FIG. 15, CML1 to CML5 are common layers such as an electron transport layer or a hole transport layer, and the electron transport layer is located below the light emitting layers (NB EML, PEML U), and is located above the light emitting layers (B EML1, B EML2, P EMLU) It is a hole transport layer. The first electron transport layer 130 is located in the first stack S1 and is provided to control a cavity for blue light emission, and is thin as in the sixth experimental example (Ex6) or seventh experimental example (Ex7) described above. It is provided with a thickness, and the overall thickness of the intermediate functional layer (OS) can be reduced.

In addition, the Nth stack Sn may include a charge transport layer in contact with the light emitting layer therein. Here, the charge transport layer is at least one of an electron transport layer and a hole transport layer.

In the white light emitting device of the embodiment of FIG. 15 , the optical compensation layer 110 or 410 is provided under the cathode electrode 120, so that cavity compensation in the intermediate functional layer OS is performed using the optical compensation layer 110 or 410. , the thickness of the first electron transport layer ETL1 positioned below the first blue light emitting layer B EML1 in the first stack S1 may be reduced, which may reduce the thickness of the entire intermediate functional layer OS. means there is Through this, the white light emitting device of the embodiment according to FIG. 15 can also reduce the driving voltage by reducing the thickness of the intermediate functional layer (OS), and improve the efficiency of white light as well as blue color efficiency by cavity compensation.

Meanwhile, the above-described experimental examples have examined the meaning of the optical compensation layer and the difference in thickness for each sub-pixel, and the thickness can be varied as needed when the internal configuration of the white light emitting device is changed.

A white light emitting device and a display device using the white light emitting device of the present invention employs a white light emitting device having an inverse structure, and has an optical compensation layer externally in contact with a cathode electrode, which is an emission side, to compensate for a cavity of an internal stack structure of the white light emitting device. With the optical compensation layer, the thickness of the electron transport layer adjacent to the inner side of the cathode electrode and the thickness of the cathode electrode are lowered, thereby lowering the driving voltage of the light emitting device and improving efficiency. In addition, by reducing the thickness of the entire light emitting device structure between both electrodes where the driving voltage acts, variability due to viewing angle is reduced, thereby improving image quality.

In the white light emitting device and the display device using the white light emitting device of the present invention, the thickness of the electron transport layer adjacent to the inner side of the cathode electrode may be reduced to 500 Å or less. Preferably, in the white light emitting device and the display device using the white light emitting device of the present invention, the electron transport layer closest to the inside of the cathode electrode may have a thickness of 50 Å or more and 500 Å or less.

A white light emitting device according to an embodiment of the present invention includes an optical compensation layer on a substrate, a cathode electrode having a first surface in contact with the optical compensation layer, an anode electrode facing the second surface of the cathode electrode, and the cathode. Between the second surface of the electrode and the anode electrode, a plurality of stacks separated by a charge generation layer are included, one of which is a first stack including a blue light emitting layer, and the other of the stacks each having a longer wavelength than blue. and may include an intermediate functional layer that is a second stack including first to third light emitting layers different from each other.

The optical compensation layer may be transparent and thicker than the cathode electrode.

The optical compensation layer is a transparent insulating film, and may have a refractive index equal to or greater than the average refractive index of the intermediate functional layer.

The optical compensation layer may be a transparent electrode having a higher refractive index than the cathode electrode.

The optical compensation layer may be a silicon nitride film.

An organic insulating layer may be further included between the substrate and the optical compensation layer.

A color conversion layer may be further included between the organic insulating layer and the substrate.

Light generated from the intermediate functional layer may pass through the cathode electrode, pass through the optical compensation layer, and pass through the substrate.

The cathode electrode may include a transparent electrode having a thickness of 200 Å to 500 Å.

The optical compensation layer may have a thickness of 1100 Å to 2400 Å.

An electron transport layer adjacent to the cathode electrode may be thinner than the cathode electrode.

A third stack including a blue light emitting layer may be further included on the intermediate functional layer.

The intermediate functional layer may further include a fourth stack in contact with a blue light emitting layer and a light emitting layer of a different color.

A display device according to an exemplary embodiment of the present invention includes a substrate having a plurality of sub-pixels each having a light-emitting part and a non-light-emitting part around the light-emitting part, and a sub-pixel driving circuit provided on the substrate in the non-emitting part of the sub-pixels. a planarization layer covering the sub-pixel driving circuit, an optical compensation layer provided on the planarization layer to correspond to at least the light emitting part of the sub-pixels, and provided in each of the sub-pixels, the optical compensation layer A cathode electrode having a first surface in contact with the cathode electrode, an anode electrode opposed to the second surface of the cathode electrode, and a plurality of stacks separated by a charge generating layer between the second surface of the cathode electrode and the anode electrode. wherein one of the stacks is a first stack including a blue light emitting layer, and the other is a middle functional layer that is a second stack including first to third light emitting layers each having a longer wavelength than blue and different from each other.

The optical compensation layer may be transparent and thicker than the cathode electrode.

The optical compensation layer may be a transparent insulating layer or a transparent electrode having a higher refractive index than the cathode electrode.

The refractive index of the optical compensation layer may be equal to or greater than the average refractive index of the intermediate functional layer.

Further, the sub-pixels of the substrate include a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel, and between the planarization layer and the substrate, the red sub-pixel, the green sub-pixel, and the blue sub-pixel. Corresponding to may further include a red conversion layer, a green conversion layer and a blue conversion layer, respectively.

The optical compensation layer may have at least two or more different thicknesses for the red sub-pixel, the green sub-pixel, the blue sub-pixel, and the white sub-pixel.

The optical compensation layer may be thicker in order of thicknesses of the green sub-pixel, the white sub-pixel, the blue sub-pixel, and the red sub-pixel.

The sub-pixel driving circuit includes a driving transistor including a gate electrode on the substrate, a semiconductor layer with a gate insulating film interposed between the gate electrode, and source and drain electrodes spaced apart from each other on both sides of the semiconductor layer. And, the drain electrode may be connected to the cathode electrode.

The optical compensation layer may electrically connect the cathode electrode and the driving transistor.

A connection between the drain electrode and the cathode electrode may be made through a common contact hole of the planarization layer and the optical compensation layer.

The cathode electrode may be a transparent electrode having a thickness of 200 Å to 500 Å, and the optical compensation layer may be a transparent insulating film or a transparent electrode having a thickness of 1100 Å to 2400 Å.

A third stack including a blue light emitting layer may be further included on the intermediate functional layer.

On the other hand, the present invention described above is not limited to the above-described embodiments and accompanying drawings, and various substitutions, modifications, and changes are possible within a range that does not depart from the technical spirit of the present invention. It will be clear to those skilled in the art.

100: substrate 110, 410: optical compensation layer
120: cathode electrode 125: electron injection layer
130: first electron transport layer 133: first blue light emitting layer
135: first hole transport layer 140: first charge generating layer
150: second electron transport layer 153: red light emitting layer
154: yellow-green light-emitting layer 155: green light-emitting layer
157: second hole transport layer 160: second charge generation layer
171: third electron transport layer 173: second blue light emitting layer
175: third hole transport layer 177: hole injection layer
190: bank 200: anode electrode
210: gate electrode 211: gate insulating film
215: semiconductor layer 216a: drain electrode
216b: source electrode 218: etch stop film
220: connection line pattern 221: protective film
230: color conversion layer 240: planarization layer

Claims (25)

an optical compensation layer on the substrate;
a cathode electrode having a first surface in contact with the optical compensation layer;
an anode electrode opposed to the second surface of the cathode electrode;
Between the second surface of the cathode electrode and the anode electrode, a plurality of stacks separated by a charge generation layer are included, one of which is a first stack including a blue light emitting layer, and the other is a blue light emitting layer, respectively. A white light emitting device including an intermediate functional layer that is a second stack including first to third light emitting layers having a longer wavelength and different from each other. According to claim 1,
The optical compensation layer is transparent and thicker than the cathode electrode. According to claim 1,
The optical compensation layer has a higher refractive index than the cathode electrode. According to claim 1,
The optical compensation layer is a transparent insulating film, and the refractive index is equal to or greater than the average refractive index of the intermediate functional layer. According to claim 1,
The optical compensation layer is a white light emitting device of a transparent electrode having a higher refractive index than the cathode electrode. According to claim 1,
The optical compensation layer is a white light emitting device of a silicon nitride film or indium zinc oxide (IZO). According to claim 1,
A white light emitting device further comprising an organic insulating film between the substrate and the optical compensation layer. According to claim 7,
A white light emitting device further comprising a color conversion layer between the organic insulating film and the substrate. According to claim 1,
The light generated from the intermediate functional layer passes through the cathode electrode and through the optical compensation layer to pass through the substrate. According to claim 2,
The cathode electrode is a white light emitting device including a transparent electrode having a thickness of 100Å to 700Å. According to claim 2,
The optical compensation layer is a white light emitting device having a thickness of 1100Å to 2400Å. According to claim 1,
An electron transport layer adjacent to the cathode electrode is thinner than the cathode electrode. According to claim 1,
A white light emitting device further comprising a third stack including a blue light emitting layer on the intermediate functional layer. According to claim 1,
A white light emitting device further comprising a fourth stack in which a blue light emitting layer and a light emitting layer of a different color are in contact with the intermediate functional layer. a substrate having a plurality of sub-pixels each having a light-emitting part and a non-light-emitting part around the light-emitting part;
a sub-pixel driving circuit provided on the substrate in non-emitting portions of the sub-pixels;
a planarization layer covering the sub-pixel driving circuit;
an optical compensation layer provided on the planarization layer to correspond to at least the light emitting parts of the sub-pixels;
a cathode electrode provided in each of the sub-pixels and having a first surface in contact with the optical compensation layer;
an anode electrode opposed to the second surface of the cathode electrode; and
Between the second surface of the cathode electrode and the anode electrode, a plurality of stacks separated by a charge generation layer are included, one of which is a first stack including a blue light emitting layer, and the other is a blue light emitting layer, respectively. A display device including an intermediate functional layer that is a second stack including first to third light emitting layers having a longer wavelength and different from each other. According to claim 15,
The optical compensation layer is a transparent insulating film or a transparent electrode thicker than the cathode electrode. According to claim 15,
The optical compensation layer has a refractive index equal to or greater than the average refractive index of the intermediate functional layer and a refractive index greater than that of the transparent electrode. According to claim 15,
The sub-pixels of the substrate include a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel;
The display device further comprises a red conversion layer, a green conversion layer, and a blue conversion layer respectively corresponding to the red sub-pixel, the green sub-pixel, and the blue sub-pixel, between the planarization layer and the substrate. According to claim 18,
The optical compensation layer has at least two or more different thicknesses for the red sub-pixel, the green sub-pixel, the blue sub-pixel, and the white sub-pixel. According to claim 18,
The optical compensation layer is thicker in order of thickness of the green sub-pixel, the white sub-pixel, the blue sub-pixel, and the red sub-pixel. According to claim 15,
The sub-pixel driving circuit includes a driving transistor including a gate electrode on the substrate, a semiconductor layer with a gate insulating film interposed between the gate electrode, and source and drain electrodes spaced apart from each other on both sides of the semiconductor layer. do,
A display device in which the drain electrode is connected to the cathode electrode. According to claim 15,
The optical compensation layer electrically connects the cathode electrode and the driving transistor to the display device. According to claim 21,
A connection between the drain electrode and the cathode electrode is made through a common contact hole of the planarization layer and the optical compensation layer. According to claim 15,
The cathode electrode is a transparent electrode having a thickness of 100 Å to 700 Å,
The optical compensation layer is a transparent insulating film or a transparent electrode having a thickness of 1100 Å to 2400 Å. According to claim 15,
The display device further comprising a third stack including a blue light emitting layer on the intermediate functional layer.

Images