CN222655683U - Display panel and display device - Google Patents

Abstract

The application provides a display panel and a display device. The display panel comprises a substrate and a light-emitting functional layer, wherein the light-emitting functional layer is positioned on one side surface of the substrate, and in the light-emitting direction of the display panel, the light-emitting functional layer comprises a plurality of organic functional layers which are sequentially overlapped, and the refractive indexes of the organic functional layers are in an increasing trend along the light-emitting direction of the display panel. The refractive indexes of the plurality of organic functional layers of the luminous functional layer are increased along the light emergent direction of the display panel, so that emergent light rays of the display panel can be effectively deflected towards the positive viewing angle direction, the light emergent efficiency of the display panel can be better improved, the brightness of a device is enhanced, and the service life of the device is prolonged relative to the prior related art.

Description

Display panel and display device

Technical Field

The application relates to the technical field of display, in particular to a display panel and a display device.

Background

An Organic LIGHT EMITTING Diode (OLED) device has low light-emitting efficiency.

However, since the low power consumption requirement of the existing display products is increasingly prominent, it is important to further improve the light emitting efficiency of the OLED display panel.

Disclosure of Invention

In view of the above, the embodiments of the present application provide a display panel, a method for manufacturing the display panel, and a display device, so as to solve the problem of low light-emitting efficiency of the existing display panel.

In a first aspect, a display panel is provided, including a substrate and a light-emitting functional layer, where the light-emitting functional layer is located on a side surface of the substrate. In the light emitting direction of the display panel, the light emitting functional layer comprises a plurality of organic functional layers which are sequentially stacked, and the refractive indexes of the organic functional layers are in an increasing trend along the light emitting direction of the display panel.

With reference to the first aspect, in some implementations of the first aspect, refractive indexes of the plurality of organic functional layers sequentially increase along a light emitting direction of the display panel.

With reference to the first aspect, in some implementations of the first aspect, a light emitting direction of the display panel is a direction from the substrate to the light emitting functional layer.

With reference to the first aspect, in certain implementation manners of the first aspect, the light extraction layer further includes a light extraction layer, where the light extraction layer is located on a side of the light emitting functional layer away from the substrate, and refractive indexes of the plurality of organic functional layers are all smaller than refractive indexes of the light extraction layer.

With reference to the first aspect, in certain implementations of the first aspect, the refractive index of the light extraction layer is greater than or equal to 1.9 and less than or equal to 2.5.

With reference to the first aspect, in certain implementations of the first aspect, the refractive indices of the plurality of organic functional layers are each greater than or equal to 1.5 and less than or equal to 1.95.

With reference to the first aspect, in certain implementations of the first aspect, the plurality of organic functional layers includes a hole transport layer, an organic light emitting layer, a hole blocking layer, and an electron transport layer stacked in order along a direction of the substrate toward the light emitting functional layer.

With reference to the first aspect, in certain implementations of the first aspect, the organic light-emitting layer includes a stacked first body light-emitting layer and a second body light-emitting layer in a direction from the substrate toward the light-emitting functional layer, the second body light-emitting layer having a refractive index greater than a refractive index of the first body light-emitting layer.

With reference to the first aspect, in certain implementations of the first aspect, the display panel further includes a hole injection layer, the hole injection layer being located between the substrate and the hole transport layer, the hole injection layer having a refractive index that is less than a refractive index of the hole transport layer.

With reference to the first aspect, in certain implementations of the first aspect, the hole injection layer has a refractive index greater than or equal to 1.5 and less than or equal to 1.6.

With reference to the first aspect, in certain implementations of the first aspect, the refractive index of the hole transport layer is greater than or equal to 1.6 and less than or equal to 1.7, the refractive index of the organic light emitting layer is greater than or equal to 1.7 and less than or equal to 1.8, the refractive index of the hole blocking layer is greater than or equal to 1.75 and less than or equal to 1.85, and the refractive index of the electron transport layer is greater than or equal to 1.8 and less than or equal to 1.9.

With reference to the first aspect, in certain implementations of the first aspect, the hole transport layer has a thickness of greater than or equal to 90 nm and less than or equal to 150 nm, the organic light emitting layer has a thickness of greater than or equal to 15 nm and less than or equal to 60 nm, the hole blocking layer has a thickness of greater than or equal to 3 nm and less than or equal to 20 nm, and the electron transport layer has a thickness of greater than or equal to 15 nm and less than or equal to 50 nm.

With reference to the first aspect, in certain implementations of the first aspect, the light emitting device includes a first electrode layer and a second electrode layer, where the first electrode layer is located on a side of the light emitting functional layer that is close to the substrate, and the second electrode layer is located on a side of the light emitting functional layer that is far from the substrate.

With reference to the first aspect, in certain implementations of the first aspect, the first electrode layer is an anode layer and the second electrode layer is a cathode layer.

In a second aspect, a display device is provided, which includes the display panel of any one of the above.

The embodiment of the application provides a display panel and a display device, wherein the refractive indexes of a plurality of organic functional layers provided with luminous functional layers are in an increasing trend along the light emitting direction of the display panel, so that the emergent light rays of the display panel can be effectively deflected towards the positive viewing angle direction, the light emitting efficiency of the display panel can be better improved, the brightness of a device is enhanced, and the service life of the device is prolonged compared with the prior art.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:

Fig. 1a is a schematic cross-sectional structure of a display panel according to an embodiment of the application.

Fig. 1b is a schematic cross-sectional structure of a light-emitting functional layer according to an embodiment of the application.

Fig. 2 is a schematic cross-sectional structure of a display panel according to another embodiment of the application.

Fig. 3 is a schematic cross-sectional structure of a display panel according to another embodiment of the application.

Fig. 4 is a schematic cross-sectional structure of a display panel according to another embodiment of the application.

Fig. 5 is a top view of a display device according to another embodiment of the application.

Fig. 6 is a schematic cross-sectional view of a display device according to another embodiment of the application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Fig. 1a is a schematic cross-sectional structure of a display panel according to an embodiment of the application. As shown in fig. 1a, the display panel includes a substrate 100 and a light emitting function layer 200 positioned on one side surface of the substrate 100, the light emitting function layer 200 including a plurality of organic function layers sequentially stacked on the substrate 100.

Specifically, the light emitting direction of the display panel is the direction from the substrate 100 to the light emitting functional layer 200, i.e. the display panel is a top emission structure. In the light emitting direction of the display panel, the plurality of organic functional layers include a hole transport layer 210, an organic light emitting layer 220, a hole blocking layer 230, and an electron transport layer 240, which are sequentially stacked. The refractive indexes of the hole transport layer 210, the organic light emitting layer 220, the hole blocking layer 230, and the electron transport layer 240 are n ₁、n₂、n₃ and n ₄, respectively, and n ₁ to n ₄ are satisfied in an increasing trend.

In one embodiment, the refractive indexes of the plurality of organic functional layers sequentially increase along the light emitting direction of the display panel.

In one embodiment, the refractive indices of the hole transport layer 210, the organic light emitting layer 220, the hole blocking layer 230, and the electron transport layer 240 satisfy n ₁<n₂<n₃<n₄.

According to the law of refraction n ₁sinθ₁＝n₂sinθ₂, when n ₁<n₂, sin θ ₁>sinθ₂, where θ ₁ is the angle of incidence of the light at the film with refractive index n ₁ and θ ₂ is the angle of refraction of the light at the film with refractive index n ₂. The incident angle refers to the angle between the incident ray and the normal, and the refraction angle refers to the angle between the refracted ray and the normal. Therefore, when the light is incident from the film with smaller refractive index to the film with larger refractive index, the refraction angle θ ₂ of the light is smaller than the incident angle θ ₁ of the light.

As shown in fig. 1a, when light is incident from the organic light emitting layer 220 to the hole blocking layer 230 due to n ₂<n₃, according to the refraction law, the refraction angle θ ₃<θ₂ of the light at the contact interface of the hole blocking layer 230 and the organic light emitting layer 220, and accordingly, the outgoing light is shifted toward the positive viewing angle direction. Similarly, due to n ₃<n₄, when light is incident on the electron transport layer 240 from the hole blocking layer 230, the angle of refraction θ ₄<θ₃ of the light at the interface of the hole blocking layer 230 and the electron transport layer 240 is according to the law of refraction. Therefore, after the light passes through the organic light emitting layer 220, the hole blocking layer 230 and the electron transporting layer 240, the outgoing light is shifted toward the forward viewing angle direction accordingly.

As shown in fig. 1a, a portion of the light incident on the hole transport layer 210 from the organic light emitting layer 220 passes through the hole transport layer 210, the organic light emitting layer 220, the hole blocking layer 230 and the electron transport layer 240 and exits, and since n ₁<n₂<n₃<n₄ is similar to the above analysis, the refraction angle of the portion of the light passing through each organic functional layer is smaller than the incident angle, and the light finally exits from the electron transport layer 240 is also shifted toward the front view angle accordingly.

In the related art, the refractive index of each organic functional layer is irregularly staggered, for example, n ₁<n₂＝n₃>n₄, so that two portions of light rays finally emitted from the electron transport layer 240 may be shifted toward a small viewing angle direction or may be shifted toward a large viewing angle direction to a smaller extent, which is not better than the effect of shifting the emitted light rays toward a positive viewing angle direction in the embodiment of the present application. Therefore, the refractive index of each organic functional layer in the light emergent direction of the display panel provided by the embodiment of the application is increased, so that the deviation effect of the emergent light to the positive viewing angle direction is better, the light emergent efficiency can be better improved, the brightness of the device is enhanced, and the service life of the device is prolonged compared with the prior related technology.

In one embodiment, the refractive index of each of the plurality of organic functional layers is greater than or equal to 1.5 and less than or equal to 1.95.

In one embodiment, the refractive index of the hole transport layer 210 is greater than or equal to 1.6 and less than or equal to 1.7, specifically may be 1.6, 1.65, 1.68, 1.7, the refractive index of the organic light emitting layer 220 is greater than or equal to 1.7 and less than or equal to 1.8, specifically may be 1.7, 1.75, 1.78, 1.8, the refractive index of the hole blocking layer 230 is greater than or equal to 1.75 and less than or equal to 1.85, specifically may be 1.75, 1.78, 1.80, 1.85, and the refractive index of the electron transport layer 240 is greater than or equal to 1.8 and less than or equal to 1.9, specifically may be 1.8, 1.85, 1.88, 1.9.

Specifically, the refractive index of the hole transport layer 210 may be set to 1.65, the refractive index of the organic light emitting layer 220 may be set to 1.75, the refractive index of the hole blocking layer 230 may be set to 1.82, and the refractive index of the electron transport layer 240 may be set to 1.89. Taking an example that the incident angle of the organic light emitting layer 220 to the hole blocking layer 230 is 60 ° according to the refraction law, in this embodiment, the angle between the outgoing light passing through the hole blocking layer 230 and the electron transport layer 240 and the normal line is 46 °. In this embodiment, the angle of incidence of the light incident on the hole transport layer 210 from the organic light emitting layer 220 is 50 °, and the angle of the outgoing light after finally passing through the organic light emitting layer 220, the hole blocking layer 230 and the electron transport layer 240 is 26 ° with respect to the normal line.

In contrast, for example, the refractive indexes of the hole transport layer 210, the organic light emitting layer 220, the hole blocking layer 230, and the electron transport layer 240 in the related art are 1.78, 1.81, and 1.80, respectively. Similarly, taking an incident angle of 60 ° as an example, in the related art, the angle between the outgoing light passing through the hole blocking layer 230 and the electron transporting layer 240 and the normal line is 75 °. In the related art, the incident angle of the light incident on the hole blocking layer 230 from the organic light emitting layer 220 is 50 °, and the angle between the outgoing light and the normal line after finally passing through the organic light emitting layer 220, the hole blocking layer 230 and the electron transport layer 240 is 50 °.

By the data comparison, the data can be more clearly and directly seen, the mode that the refractive indexes of the plurality of organic functional layers are increased in the light emitting direction is set in the implementation, compared with the prior art, the included angle of the emergent light relative to the normal can be effectively reduced, namely the emergent light is deviated to the positive viewing angle direction, so that the light emitting efficiency can be better improved, the brightness of a device is enhanced, and the service life of the device is prolonged relative to the prior art.

In one embodiment, the display panel further includes a hole injection layer between the substrate 100 and the hole transport layer 210, and the hole injection layer has a refractive index smaller than that of the hole transport layer 210 and a refractive index greater than or equal to 1.5 and less than or equal to 1.95.

In one embodiment, the hole injection layer has a refractive index greater than or equal to 1.5 and less than or equal to 1.6.

In one embodiment, the display panel further includes an electron blocking layer between the hole transport layer 210 and the organic light emitting layer 220, and the electron blocking layer has a refractive index greater than that of the hole transport layer 210 and less than that of the organic light emitting layer 220, and has a refractive index greater than or equal to 1.5 and less than or equal to 1.95. It should be understood that the OLED device may include only a portion of the film layers of the plurality of organic functional layers described above.

In one embodiment, the thickness of the hole transport layer 210 is greater than or equal to 90 nm and less than or equal to 150 nm, the thickness of the organic light emitting layer 220 is greater than or equal to 15 nm and less than or equal to 60 nm, the thickness of the hole blocking layer 230 is greater than or equal to 3 nm and less than or equal to 20 nm, and the thickness of the electron transport layer 240 is greater than or equal to 15 nm and less than or equal to 50 nm.

Fig. 1b is a schematic cross-sectional structure of a light-emitting functional layer according to an embodiment of the application. As shown in fig. 1b, in a direction from the substrate 100 to the light emitting functional layer 200, the organic light emitting layer 220 includes a first body light emitting layer 221 and a second body light emitting layer 222 stacked, and a refractive index n ₂₂ of the second body light emitting layer 222 is greater than a refractive index n ₂₁ of the first body light emitting layer 221.

The first host light-emitting layer 221 comprises a hole host material and a TADF light-emitting guest material with strong hole transport capability near the hole transport layer 210, and the second host light-emitting layer 222 comprises an electron host material and a TADF light-emitting guest material with strong electron transport capability near the electron transport layer 240, which regulate and control carriers to realize carrier balance and widen a light-emitting interval so as to improve device efficiency.

As shown in fig. 1b, when light is incident from the first body emission layer 221 to the second body emission layer 222 due to n ₂₁<n₂₂, according to the refraction law, the refraction angle θ ₂₂<θ₂₁ of the light at the contact interface of the first body emission layer 221 and the second body emission layer 222, and accordingly, the outgoing light is shifted to the positive viewing angle direction.

Fig. 2 is a schematic cross-sectional structure of a display panel according to another embodiment of the application. With respect to fig. 1, the display panel in fig. 2 further includes a light extraction layer 300, the light extraction layer 300 is located on a side of the light emitting functional layer 200 away from the substrate 100, and refractive indexes of the plurality of organic functional layers are all smaller than refractive indexes of the light extraction layer. An incident angle of light incident on the interface between the light-emitting functional layer 200 and the light extraction layer 300 is set to be θ ₅, an included angle between the light emitted through the light extraction layer 300 and the normal direction is set to be θ ₆, and θ ₆<θ₅ is set according to the refraction law. Therefore, when the refractive index of the light extraction layer 300 is set to be larger than that of the light emitting functional layer 200, the light emitted through the light extraction layer 300 is deflected in the forward viewing angle direction, and the light extraction efficiency of the display panel can be improved.

In one embodiment, the refractive index of the light extraction layer 300 is greater than or equal to 1.9 and less than or equal to 2.5, and preferably, the refractive index of the light extraction layer 300 may be 1.9,2.07,2.2,2.3 or 2.5, or the like.

In one embodiment, the light extraction layer 300 includes a concave-convex lens structure that functions to change the path of light to reduce light localized within the display panel, thereby increasing the light extraction efficiency of the display panel.

In one embodiment, the display panel further includes a first electrode layer 400 and a second electrode layer 500, the first electrode layer 400 is located at a side of the light emitting function layer 200 near the substrate 100, and the second electrode layer 500 is located at a side of the light emitting function layer 200 far from the substrate 100.

In one embodiment, the first electrode layer 400 is an anode layer and the second electrode layer 500 is a cathode layer. The anode layer is transparent conductive oxide or metal, can have a multi-film composite structure, such as an ITO/Ag/ITO structure, and the cathode can be a magnesium-silver alloy layer.

The refractive index of the second electrode layer 500 is generally low, and when the incident angle of the light incident from the light emitting functional layer 200 to the contact interface between the second electrode layer 500 and the light extraction layer 300 is 46 ° by taking the refractive index of the second electrode layer 500 as 0.16 and the refractive index of the light extraction layer 300 as an example, the refractive angle of the refracted light through the light extraction layer 300 is 26 ° according to the law of refraction, and the outgoing light through the light extraction layer 300 is significantly shifted in the forward viewing angle direction, so that the brightness in the forward viewing angle direction can be effectively enhanced.

In one embodiment, the display panel includes red, green, and blue subpixels. The specific values of the refractive indexes of the film layers are taken as green sub-pixels, so that the values of the red sub-pixels and the blue sub-pixels are adjusted accordingly.

Fig. 3 is a schematic cross-sectional structure of a display panel according to another embodiment of the application. As shown in fig. 3, the display panel further includes a pixel circuit 600 between the substrate 100 and the first electrode 400, and the pixel circuit 600 and the first electrode 400 are electrically connected to drive the light emitting device to emit light at a predetermined brightness. The display panel may further include a planarization layer 700 between the pixel circuit 600 and the first electrode 400. The planarization layer may be an inorganic layer or an organic layer.

In one embodiment, the display panel further includes a thin film encapsulation layer located on a side of the second electrode layer 500 away from the substrate 100, for encapsulating the light emitting function layer 200, so as to prevent water oxygen in the external environment from eroding the organic light emitting layer 220 in the light emitting function layer 200, thereby making the service life of the display panel longer.

Fig. 4 is a schematic cross-sectional structure of a display panel according to another embodiment of the application. Compared with fig. 2, the light emitting direction of the display panel in fig. 4 is the direction from the light emitting functional layer 200 to the substrate 100, and the display panel has a bottom emission structure. In the light emitting direction of the display panel, between the first electrode layer 400 and the second electrode layer 500, the plurality of organic functional layers include an electron transport layer 240, a hole blocking layer 230, an organic light emitting layer 220, and a hole transport layer 210, which are sequentially stacked. The refractive indexes of the hole transport layer 210, the organic light emitting layer 220, the hole blocking layer 230 and the electron transport layer 240 are n ₁、n₂、n₃ and n ₄, respectively, and n ₁>n₂>n₃>n₄ is satisfied, that is, the refractive indexes of the plurality of organic functional layers are increased in an emitting direction of the display panel.

As shown in fig. 4, since n ₁>n₂, when light is incident from the organic light-emitting layer 220 to the hole transport layer 210, the incident angle is θ ₁₁. According to the law of refraction, the angle of refraction θ ₁₂<θ₁₁ of the light at the contact interface of the hole transport layer 210 and the organic light emitting layer 220, and thus, the light emitted from the light emitting functional layer 200 is shifted toward the positive viewing angle direction.

As shown in fig. 4, another portion of the light emitted from the organic light emitting layer 220 is reflected at the interface of the second electrode layer 500 after passing through the hole blocking layer 230 and the electron transporting layer 240, and is incident at the interface of the electron transporting layer 240 and the hole blocking layer 230, with an incident angle θ ₁₃, and due to n ₁>n₂>n₃>n₄, the incident angle θ ₁₆<θ₁₅<θ₁₄<θ₁₃ is similar to the above analysis. Therefore, the refraction angle of the light passing through each organic functional layer is smaller than the incident angle, and the light finally exiting from the hole transport layer 210 is correspondingly shifted towards the front view direction.

The embodiment of the application also provides a display device, as shown in fig. 5, and fig. 5 is a top view of the display device in another embodiment of the application. As shown in fig. 5, the display device in this embodiment includes a display area 10 and a non-display area 20, and the display area 10 displays an image by a plurality of sub-pixels. Specifically, the display area 10 may be rectangular, and the non-display area 20 is disposed around the display area 10. Of course, the shape and arrangement of the display region 10 and the non-display region 20 include, but are not limited to, the examples described above, the display region 10 being provided with a plurality of sub-pixels emitting light of different colors, the sub-pixels being characterized as minimum units for emitting light (e.g., minimum addressable units of a display panel).

In one embodiment, the display device can be any product or component with display function, such as a television, a display, a notebook computer, a digital photo frame, a navigator and the like. The display device may include a power supply assembly, and a display panel electrically connected to the power supply assembly. The display panel may be the display panel in any of the above embodiments.

Fig. 6 is a cross-sectional view of the display device of fig. 5 taken along the direction A-A'. As shown in fig. 6, the display device in this embodiment includes, in addition to the display panel 11, a polarizer 12, an optical adhesive 13, and a cover 14, which are stacked on the light-emitting side of the display panel 11.

In one embodiment, the display device further includes a support film 15 on a side of the display panel 11 remote from the cover plate 14.

In one embodiment, the shape of the display panel of the display device application may be more selected, for example, the display area 10 may have a circular shape like a wristwatch when the display panel is used for a wearable device worn on a user, and the display area 10 and the non-display area 20 may take on, for example, a circular, polygonal, or other shape when the display panel is used for display on a vehicle.

In one embodiment, the display device in this embodiment may be a mobile phone, including the display panel of the top emission structure shown in fig. 1-3. Because, top-emitting devices are the first choice for active display on small screens such as cell phones. Large displays (e.g. televisions) are due to the large luminance area of the pixels themselves and the sufficient space to place the TFTs and pixels, even if the TFTs block some light, the effect is not noticeable. On small displays, however, it is particularly important to maximize the light emitting area because the pixels on the display are very dense. If the resolution of the OLED is increased, the number of TFTs is increased, so that the problem of bottom emission is more prominent. Of course, the amount of light can also be increased by increasing the power consumption of the pixels, but this increases the power consumption and requires stronger power. But this is not a good solution as it may have an adverse effect on the lifetime of the light emitting element. Therefore, most of the display panels adopted on the mobile display and the IT instrument display at present are top emission structures, and the light emitting efficiency of the display panels can be effectively ensured by the embodiment of the application.

It is noted that in the drawings, the size of layers and regions may be exaggerated for clarity of illustration. Moreover, it will be understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element or intervening layers may be present. In addition, it will be understood that when an element or layer is referred to as being "under" another element or layer, it can be directly under the other element or intervening layers or elements may be present. In addition, it will be understood that when a layer or element is referred to as being "between" two layers or elements, it can be the only layer between the two layers or elements, or more than one intervening layer or element may also be present. Like reference numerals refer to like elements throughout.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

It will be appreciated by persons skilled in the art that the foregoing description of the preferred embodiments of the application has been given by way of illustration only, and that various modifications, equivalents, and alternatives falling within the spirit and principles of the application are deemed to be within the scope of the application as defined by the appended claims.

Claims (15)

1. A display panel, comprising:

A substrate, and

The light-emitting functional layer is positioned on one side surface of the substrate;

In the light emitting direction of the display panel, the light emitting functional layer comprises a plurality of organic functional layers which are sequentially stacked, and the refractive indexes of the organic functional layers are in an increasing trend along the light emitting direction of the display panel.

2. The display panel according to claim 1, wherein refractive indexes of the plurality of organic functional layers sequentially increase in a light emitting direction of the display panel.

3. The display panel according to claim 1, wherein a light emitting direction of the display panel is a direction from the substrate to the light emitting functional layer.

4. The display panel according to claim 3, further comprising a light extraction layer located on a side of the light emission functional layer remote from the substrate, wherein refractive indices of the plurality of organic functional layers are each smaller than refractive indices of the light extraction layer.

5. The display panel according to claim 4, wherein a refractive index of the light extraction layer is greater than or equal to 1.9 and less than or equal to 2.5.

6. The display panel according to claim 1, wherein refractive indices of the plurality of organic functional layers are each greater than or equal to 1.5 and less than or equal to 1.95.

7. The display panel according to claim 1, wherein the plurality of organic functional layers include a hole transport layer, an organic light emitting layer, a hole blocking layer, and an electron transport layer stacked in this order along a direction in which the substrate is directed to the light emitting functional layer.

8. The display panel according to claim 7, wherein the organic light-emitting layer includes a first body light-emitting layer and a second body light-emitting layer stacked in a direction from the substrate toward the light-emitting functional layer, the second body light-emitting layer having a refractive index greater than that of the first body light-emitting layer.

9. The display panel of claim 7, further comprising a hole injection layer between the substrate and the hole transport layer, the hole injection layer having a refractive index that is less than a refractive index of the hole transport layer.

10. The display panel according to claim 9, wherein a refractive index of the hole injection layer is greater than or equal to 1.5 and less than or equal to 1.6.

11. The display panel according to claim 7, wherein the refractive index of the hole transport layer is 1.6 or more and 1.7 or less, the refractive index of the organic light-emitting layer is 1.7 or more and 1.8 or less, the refractive index of the hole blocking layer is 1.75 or more and 1.85 or less, and the refractive index of the electron transport layer is 1.8 or more and 1.9 or less.

12. The display panel according to claim 7, wherein the hole transport layer has a thickness of 90 nm or more and 150 nm or less, the organic light-emitting layer has a thickness of 15 nm or more and 60 nm or less, the hole blocking layer has a thickness of 3 nm or more and 20 nm or less, and the electron transport layer has a thickness of 15 nm or more and 50 nm or less.

13. The display panel of claim 1, further comprising a first electrode layer and a second electrode layer, the first electrode layer being located on a side of the light-emitting functional layer that is closer to the substrate, the second electrode layer being located on a side of the light-emitting functional layer that is farther from the substrate.

14. The display panel of claim 13, wherein the first electrode layer is an anode layer and the second electrode layer is a cathode layer.

15. A display device comprising the display panel of any one of claims 1-14.