DISPLAY DEVICE

A display device according to an embodiment includes: a substrate; and a plurality of light emitting devices disposed above the substrate. The light emitting device includes a first electrode, an auxiliary layer disposed above the first electrode, a light emitting layer disposed on the auxiliary layer, and a second electrode disposed above the light emitting layer, and a red light emitting layer and/or the auxiliary layer includes a discussed compound, e.g., a compound represented by Chemical Formula 1 and/or a compound represented by Chemical Formula 2.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2022-0168012, filed in the Korean Intellectual Property Office on Dec. 5, 2022, the entire content of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a display device, and for example, to a display device with reduced reflection (e.g., reflection of external light).

2. Description of the Related Art

When external light is reflected and/or scattered on a display surface of a display device, an original image on the display device may not be properly observed. For example, because a portable device such as a mobile phone, a laptop computer, and/or the like is increasingly being utilized outdoors where there may be an excess amount or there may be plenty of external light, a problem of the reflection and/or scattering of external light on the display surface of the display device should be be overcome.

Various suitable methods have been proposed to overcome the problem of the reflection and/or scattering of external light.

SUMMARY

An aspect according to one or more embodiments of the present disclosure is directed toward a display device with reduced external light reflection.

A display device according to an embodiment includes: a substrate; and a light emitting device on the substrate. The light emitting device includes a first electrode, a red auxiliary layer on the first electrode, a red light emitting layer on the red auxiliary layer, and a second electrode on the red light emitting layer, and the red light emitting layer and/or the red auxiliary layer includes a compound represented by Chemical Formula 1 and/or a compound represented by Chemical Formula 2.

A content (e.g., amount) of the compound represented by Chemical Formula 1 and/or the compound represented by Chemical Formula 2 in the red light emitting layer and/or the red auxiliary layer may be 1 wt % to 50 wt % based on a total weight of the red light emitting layer and/or the red auxiliary layer.

The light emitting device may further include: a capping layer on the second electrode; and an encapsulation layer on the capping layer.

The light emitting device may further include an inorganic absorption layer between the capping layer and the encapsulation layer and/or between the capping layer and the second electrode, and the inorganic absorption layer may include bismuth.

The display device may not include a (e.g., may exclude any) polarization layer (e.g., is free of polarization layer).

The display device may not include a (e.g., may exclude any) color filter (e.g., is free of color filter).

The display device may further include: a reflection control layer on the encapsulation layer; and a low-reflection inorganic layer on the light emitting device. The reflection control layer may include a pigment and/or a dye.

A display device according to another embodiment includes: a substrate; and a light emitting device on the substrate. The light emitting device includes a first electrode, a green auxiliary layer on the first electrode, a green light emitting layer on the green auxiliary layer, and a second electrode on the green light emitting layer, and the green light emitting layer and/or the green auxiliary layer includes at least one selected from among compounds represented by Chemical Formula 3 to Chemical Formula 6.

A content (e.g., amount) of the at least one selected from the compounds represented by Chemical Formula 3 to Chemical Formula 6, in the green light emitting layer and/or the green auxiliary layer, may be 1 wt % to 50 wt % based on a total weight of the green light emitting layer and/or the green auxiliary layer.

The light emitting device may further include: a capping layer on the second electrode; and an encapsulation layer on the capping layer.

The light emitting device may further include an inorganic absorption layer between the capping layer and the encapsulation layer or between the capping layer and the second electrode, and the inorganic absorption layer may include bismuth.

The display device may not include a (e.g., may exclude any) polarization layer (e.g., is free of polarization layer).

The display device may not include a (e.g., may exclude any) color filter (e.g., is free of color filter).

The display device may further include: a reflection control layer on the encapsulation layer; and a low-reflection inorganic layer on the light emitting device. The reflection control layer may include a pigment and/or a dye.

A display device according to another embodiment includes: a substrate; and a light emitting device on the substrate. The light emitting device includes a first electrode, a blue light emitting layer on the first electrode, and a second electrode on the blue light emitting layer, and the blue light emitting layer includes at least one selected from compounds represented by Chemical Formula 3, Chemical Formula 4, Chemical Formula 7, and Chemical Formula 8.

The at least one selected from the compounds represented by Chemical Formula 3, Chemical Formula 4, Chemical Formula 7, and Chemical Formula 8 may be 1 wt % to 50 wt % based on a total weight of the blue light emitting layer.

A display device according to another embodiment includes: a substrate; and a plurality of light emitting devices on the substrate. The plurality of light emitting devices include a first electrode, a hole control layer on the first electrode, a respective one of a red light emitting layer, a green light emitting layer, or a blue light emitting layer on the hole control layer, an electron control layer on the red light emitting layer, the green light emitting layer, and the blue light emitting layer, and a second electrode on the electron control layer, and the electron control layer or the hole control layer includes at least one selected from compounds represented by Chemical Formula 8 to Chemical Formula 11.

The at least one selected from compounds represented by Chemical Formula 8 to Chemical Formula 11 may be 1 wt % to 50 wt % based on a total weight of the electron control layer and/or the hole control layer.

A display device according to another embodiment includes: a substrate; and a plurality of light emitting devices on the substrate. The plurality of light emitting devices include a first electrode, a hole control layer on the first electrode, a red light emitting layer, a green light emitting layer, and a blue light emitting layer respectively disposed above or on the hole control layer, an electron control layer on the red light emitting layer, the green light emitting layer, and the blue light emitting layer, a second electrode on the electron control layer, a red auxiliary layer between the red light emitting layer and the hole control layer, and a green auxiliary layer between the green light emitting layer and the hole control layer The red auxiliary layer includes a compound represented by Chemical Formula 1, the green auxiliary layer includes a compound represented by Chemical Formula 3, and the blue light emitting layer includes a compound represented by Chemical Formula 8.

The display device may not include (e.g., may exclude) a polarization layer or a color filter (e.g., free of both polarization layer and color filter).

According to the embodiments, a display device having reduced external light reflection is provided.

DETAILED DESCRIPTION

In order to clearly describe the present disclosure, parts or portions that are irrelevant to the description are omitted, and identical or similar constituent elements throughout the specification are denoted by the same reference numerals.

Further, in the drawings, the size and thickness of each element are arbitrarily illustrated for ease of description, and the present disclosure is not limited to those illustrated in the drawings. In the drawings, the thickness of layers, films, panels, regions, etc., and the areas may be exaggerated for clarity and for ease of description.

In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of the stated elements but not the exclusion of any other elements.

Further, throughout the specification, the phrase “in a plan view” or “on a plane” refers to viewing a target portion from the top, and the phrase “in a cross-sectional view” or “on a cross-section” refers to viewing a cross-section formed by vertically cutting a target portion from the side.

Hereinafter, a light emitting device (or a light emitting element) and a display device including the light emitting device according to the present embodiment will be described in more detail with reference to the drawings.

FIG.1schematically illustrates a cross-sectional view of the light emitting device according to the present embodiment. Referring toFIG.1, the light emitting device according to the present embodiment includes a first electrode191, a hole control layer HTL, a light emitting layer EML, an electron control layer ETL, a second electrode270, a capping layer CPL, and an encapsulation layer TFE. According to embodiments of the present disclosure, a dye and/or a pigment having a light absorption characteristic is included in at least one of the hole control layer HTL, the light emitting layer EML, or the electron control layer ETL to reduce the reflectance of the display device (including the light emitting device) and to absorb external light. In an embodiment, the hole control layer HTL may include a hole injection layer and a hole transport layer. The electron control layer ETL may include an electron injection layer and an electron transport layer.

FIG.2schematically illustrates the cross-sectional view of the light emitting device emitting red, blue, and green light (e.g., a plurality of, or three light emitting devices for emitting red, blue, and green light, respectively). Referring toFIG.2, the light emitting device (e.g., a plurality of, or three the light emitting devices) according to the present embodiment may include the first electrode191, the hole control layer HTL, a red auxiliary layer RA, a red light emitting layer RE, a green auxiliary layer GA, a green light emitting layer GE, and a blue light emitting layer BE. The red auxiliary layer RA may be disposed between the red light emitting layer RE and the hole control layer HTL, and the green auxiliary layer GA may be disposed between the green light emitting layer GE and the hole control layer HTL.

The electron control layer ETL may be disposed above or on the red light emitting layer RE, the green light emitting layer GE, and the blue light emitting layer BE. The second electrode270may be disposed above or on the electron control layer ETL. The capping layer CPL may be disposed above or on the second electrode270.

In the present embodiment, a light absorbing material may be disposed in an individual layer of the light emitting device for emitting light of each color (e.g., disposed in the red auxiliary layer RA or the green auxiliary layer GA). In some embodiments, the light absorbing material may be disposed in the hole control layer HTL or the electron control layer ETL commonly disposed in each light emitting device.

Various embodiments are described below in more detail.

In an embodiment, the red auxiliary layer RA or the red light emitting layer RE may include a red dye, and the red dye may be a compound represented by Chemical Formula 1 or Chemical Formula 2. In this case, a content (e.g., amount) of the red dye within the red auxiliary layer RA and/or the red light emitting layer RE may be 1 wt % to 50 wt % based on a total weight of the red auxiliary layer RA and/or the red light emitting layer RE including the red dye.

Because the compound represented by Chemical Formula 1 or Chemical Formula 2 has an absorption coefficient for a red light emitting region close to 0, the reflectance of external light may be reduced without reducing the luminous efficiency.

FIG.3illustrates a light emission spectrum of a red light emitting device and an absorption spectrum (or a light absorption spectrum) of the compound represented by Chemical Formula 1. Referring toFIG.3, the compound represented by Chemical Formula 1 may be to absorb light with a wavelength of 600 nm or less while not substantially (e.g., hardly) absorbing light of a red wavelength, so that the reflectance of external light is reduced without reducing the luminous efficiency.

Table 1 andFIG.4show reflectance of the light emitting device according to a content (e.g., amount) of the compound of Chemical Formula 1 included in the red auxiliary layer.

Referring to Table 1 andFIG.4, it may be seen that the reflectance of the light emitting device is decreased as the content (e.g., amount) of the compound of Chemical Formula 1 is increased. Therefore, reflection of external light may be effectively prevented or reduced.

In an embodiment, an inorganic absorption layer IA may be further included between the second electrode270and the capping layer CPL or between the capping layer CPL and the encapsulation layer TFE. The inorganic absorption layer IA may include bismuth, and the inorganic absorption layer IA may reduce reflectance by absorbing external light.FIG.5illustrates the light emitting device including the inorganic absorption layer IA between the capping layer CPL and the encapsulation layer TFE. As shown inFIG.5, even in a case of the light emitting device including the inorganic absorption layer IA, when a light absorbing material is included in the red auxiliary layer RA, the reflectance may be reduced.

FIG.6shows the reflectance of the light emitting device according to the content (e.g., amount) of the compound of Chemical Formula 1 included in the red auxiliary layer RA in the light emitting device including the inorganic absorption layer IA shown inFIG.5. Referring toFIG.6, even in a case of the light emitting device including the inorganic absorption layer IA, it may be seen that reflectance is decreased as the content (e.g., amount) of the compound of Chemical Formula 1 included in the red auxiliary layer RA is increased.

In an embodiment, the green auxiliary layer GA or the green light emitting layer GE may include a yellow dye and/or a green dye. The yellow dye may be at least one compound represented by Chemical Formula 3 or 4, and the green dye may be at least one compound represented by Chemical Formula 5 or 6. In this case, a content (e.g., amount) of the dye within the green auxiliary layer GA or the green light emitting layer GE may be 1 wt % to 50 wt % based on a total weight of the green auxiliary layer GA or the green light emitting layer GE including the dye.

Table 2 andFIG.7show reflectance of the light emitting device according to a content (e.g., amount) of a compound of Chemical Formula 3 included in the green auxiliary layer.

Referring to Table 2 andFIG.7, it may be seen that the reflectance of the light emitting device is decreased as the content (e.g., amount) of the compound of Chemical Formula 3 is increased. Therefore, reflection of external light may be effectively prevented or reduced.

In an embodiment, the blue light emitting layer BE may include at least one compound represented by Chemical Formula 3, 4, 7, or 8. In this case, a content (e.g., amount) of the compound within the blue light emitting layer BE may be 1 wt % to 50 wt % based on a total weight of the blue light emitting layer BE.

Table 3 andFIG.8show reflectance of the light emitting device according to a content (e.g., amount) of the compound represented by Chemical Formula 7 included in the blue light emitting layer.

Referring to Table 3 andFIG.8, it may be seen that the reflectance of the light emitting device is decreased as the content (e.g., amount) of the compound of Chemical Formula 7 is increased. Therefore, reflection of external light may be effectively prevented or reduced.

As described above, the embodiments in which the light absorbing material is included in the light emitting layer and/or the auxiliary layer of the light emitting device for emitting light of each color have been described, but the present disclosure is not limited thereto. In some embodiments, the light absorbing material may be included in a common layer such as the hole control layer and/or the electron control layer. In this case, the same light absorbing material may be included in the light emitting device for emitting light of each color. For example, the light emitting device according to the present embodiment may include one or more dyes (e.g., the compounds) represented by Chemical Formulas 8 to 11 in the hole control layer or the electron control layer. In this case, a content (e.g., amount) of the dye within the hole control layer or the electron control layer may be 1 wt % to 50 wt % based on a total weight of the hole control layer or the electron control layer including the dye.

Table 4 andFIG.9show reflectance of the light emitting device according to the content (e.g., amount) of the compound of Formula 8 included in the hole control layer.

Referring to Table 4 andFIG.9, it may be seen that the reflectance of the light emitting device is decreased as the content (e.g., amount) of the compound of Chemical Formula 8 is increased. Therefore, reflection of external light may be effectively prevented or reduced. The compound of Chemical Formula 8 may be commonly included in the red light emitting device, the green light emitting device, and the blue light emitting device, and as may be seen fromFIG.9, reflectance is decreased in all wavelength regions.

FIG.10shows a cross-sectional view for a light emitting device according to another embodiment, and is substantially the same as the embodiment ofFIG.2except that the inorganic absorption layer IA is further included between the second electrode270and the capping layer CPL. A detailed description of the same component is omitted. The inorganic absorption layer IA may include bismuth.

According to an Embodiment 1 (or a first embodiment) in a structure ofFIG.10, the red auxiliary layer RA may include the compound of Chemical Formula 1, the green auxiliary layer GA may include the compound of Chemical Formula 3, and the blue light emitting layer BE may include the compound of Chemical Formula 8.

An optical characteristic of the Embodiment 1 is compared with an Embodiment 2 (or a second embodiment). Embodiment 2 has the structure ofFIG.10but does not include (e.g., may exclude any of) the compound of Chemical Formula 1, the compound of Chemical Formula 3, or the compound of Chemical Formula 8 in the respective layer, and the optical characteristics of Embodiments 1 and 2 are shown in Table 5 andFIG.11.

It may be seen that the Embodiment 1, in which the red auxiliary layer RA include the compound of Chemical Formula 1, the green auxiliary layer include the compound of Chemical Formula 3, and the blue light emitting layer include the compound of Chemical Formula 8, has a reflectance decrease of 0.31% compared with the Embodiment 2 that does not include the respective compounds.

FIG.12is a measurement of reflective colors of the Embodiments 1 and 2, andFIG.13shows the reflective colors (or reflective color senses) of the Embodiments 1 and 2. Referring toFIGS.12and13, it may be seen that the Embodiment 1 shows improved reflective color (or improved reflective color senses) compared with the Embodiment 2. For example, it may be seen that the light emitting device including a light absorbing dye and/or a light absorbing pigment according to the present embodiment reduces reflectance and has improved reflective color.

Because the light emitting device has an excellent or suitable low reflection characteristic, the light emitting device may be applied to a display device that does not include a separate polarization layer (e.g., is free of polarization layer or is polarization layer free). Hereinafter, one or more suitable structures of the display device including the light emitting device will be described. Similar to the one or more suitable embodiments described above, the light emitting device described below may include a light absorbing dye and/or a light absorbing pigment (e.g., does not include a separate color filter (e.g., is free of color filter or is color filter free)).

FIG.14schematically illustrates a cross-sectional view of the display device according to an embodiment.

Referring toFIG.14, a plurality of the light emitting devices LED are disposed above or on the substrate SUB. Each light emitting device LED may be the red light emitting device RED, the blue light emitting device BED, or the green light emitting device GED, and description of these light emitting devices is the same as described above. For example, each light emitting device LED may include a light absorbing dye and/or a light absorbing pigment within the device.

A partition wall350may be disposed between light emitting devices LED, and the encapsulation layer TFE may be disposed on the light emitting device LED and the partition wall350. A first organic film OL1, a first inorganic film IL1, and a second organic film OL2may be disposed above or on the encapsulation layer TFE. According to an embodiment, portions of the first organic film OL1, the first inorganic film IL1, and the second organic film OL2may be omitted (e.g., not be provided or may be removed (e.g., to form an opening therein)). As shown inFIG.14, a metal layer MTL may be disposed on the first inorganic film IL1, and a portion of the metal layer MTL may be connected to the metal layer MTL disposed on the first organic film OL1through an opening formed in the first inorganic film IL1. In an embodiment, the metal layer MTL may not be provided.

Light blocking members BML may be disposed on the second organic film OL2, and a red color filter RCF, a green color filter GCF, and a blue color filter BCF may be disposed between the light blocking members BML. Each color filter may be disposed to overlap the light emitting device emitting the same color. An overcoat layer OC may be disposed on the red color filter RCF, the green color filter GCF, and the blue color filter BCF. For example, the display device according to the embodiment ofFIG.14may include a color filter disposed overlapping the light emitting device LED without including a polarization layer.

FIG.15is a cross-sectional view of a display device according to another embodiment.FIG.15is substantially the same as the embodiment ofFIG.14except thatFIG.15does not include a color filter CF, but further includes a low-reflection inorganic layer RL disposed on the light emitting device LED, and includes a reflection control layer RCL instead of the overcoat layer OC. A detailed description of the same components is not provided again. In the present embodiment shown inFIG.15, the low-reflection inorganic layer RL disposed on the light emitting device LED is further included. Accordingly, the reflectance may be further reduced. In the embodiment ofFIG.15, each light emitting device LED may include a light absorbing dye and/or a light absorbing pigment within the device. Therefore, the reflectance may be reduced by the light emitting device LED, and the reflectance may be reduced by the low-reflection inorganic layer RL. In addition, the reflection control layer RCL is utilized instead of the overcoat layer OC. The reflection control layer RCL may be to absorb external light and may reduce the reflectance by including a light absorbing dye and/or a light absorbing pigment. A structure ofFIG.15is more economical (e.g., to produce) because the number of masks utilized (e.g., needed) in the manufacturing process is less than that ofFIG.14.

FIG.16shows a tandem structure in which light emitting devices are stacked. Referring toFIG.16, the hole control layer HTL, the red light emitting layer RE, the green light emitting layer GE, and the blue light emitting layer BE may be disposed above or on the first electrode191. In some embodiments, the red auxiliary layer and the green auxiliary layer may be further included. The metal layer MTL may be disposed above or on the light emitting layer, and an N-doped layer NDL and a P-doped layer PDL may be disposed above or on the metal layer MTL. Thereafter, the hole control layer HTL may be disposed, and the red light emitting layer RE, the green light emitting layer GE, and the blue light emitting layer BE may be disposed again. Next, the electron control layer ETL may be disposed, and the second electrode270may be disposed. The second electrode270may include a first layer271and a second layer272, and the first layer271may include Yb and the second layer272may include Ag and Mg. The capping layer CPL may be disposed above or on the second electrode270. Also, in an embodiment ofFIG.16, each light emitting device may include a light absorbing dye and/or a light absorbing pigment to reduce the reflectance.

The use of “may” when describing embodiments of the present disclosure refers to “one or more embodiments of the present disclosure”. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Throughout the disclosure, the expression, such as “at least one of a, b or c”, “at least one selected from a, b, and c”, “at least one selected from the group consisting of a, b, and c”, “at least one from among a, b, and c”, etc., indicates only a, only b, only c, both (e.g., simultaneously) a and b, both (e.g., simultaneously) a and c, both (e.g., simultaneously) b and c, all of a, b, and c, or variation(s) thereof.

Although the present disclosure has been described with reference to embodiments of the present disclosure, it will be understood that the present disclosure should not be limited to these embodiments but one or more suitable changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the present disclosure.

Accordingly, the technical scope of the present disclosure is not intended to be limited to the contents set forth in the detailed description of the specification, but is intended to be defined by the appended claims, and equivalents thereof.