Quantum dot light-emitting device and display apparatus

A quantum dot light-emitting device and a display apparatus including the same, the device including a light-emitting device that emits a first light; a quantum dot layer facing the light-emitting device, the quantum dot layer including a plurality of quantum dots, absorbing the first light, and emitting a second light and a third light that have different wavelength ranges compared to the first light; and a band pass filter on the quantum dot layer, the band pass filter cutting off a portion of the second light and a portion of the third light.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2013-0112869, filed on Sep. 23, 2013, in the Korean Intellectual Property Office, and entitled: “Quantum Dot Light-Emitting Device and Display Apparatus,” is incorporated by reference herein in its entirety.

BACKGROUND

Embodiments relate to a quantum dot light-emitting device and a display apparatus.

2. Description of the Related Art

Flat panel display apparatuses may include, e.g., liquid crystal displays (LCDs), plasma display panels (PDPs), and organic light-emitting display apparatuses. LCDs may have advantages of excellent visibility, a simple thin film fabrication technology, low power and less heat emission, and may be used in mobile devices, computer monitors, and TVs.

An LCD is a light-receiving type display apparatus that forms an image by receiving light externally, e.g., not through self-emission. Thus, the LCD may include a backlight unit in a lower part of a liquid crystal display panel, and may display an image by using light emitted from the backlight unit.

A light-emitting diode (LED) that has an excellent effect in saving energy and has fast response speeds may be used as a light source of such a backlight unit. A LED backlight unit may enhance the characteristics of the LCD.

SUMMARY

Embodiments are directed to a quantum dot light-emitting device and a display apparatus.

The embodiments may be realized by providing a quantum dot light-emitting device including a light-emitting device that emits a first light; a quantum dot layer facing the light-emitting device, the quantum dot layer including a plurality of quantum dots, absorbing the first light, and emitting a second light and a third light that have different wavelength ranges compared to the first light; and a band pass filter on the quantum dot layer, the band pass filter cutting off a portion of the second light and a portion of the third light.

The plurality of quantum dots may include a plurality of first quantum dots that absorb the first light and emit the second light, and a plurality of second quantum dots that absorb the first light and emit the third light.

The first quantum dots and the second quantum dots may be formed of a same material and have different sizes.

The third light may have a longer wavelength than the second light, the band pass filter may cut off light in a shortest wavelength region of the second light, and the band pass filter may cut off light in a longest wavelength region of the third light.

A peak wavelength of the second light that passes through the band pass filter may be longer than a peak wavelength of the second light emitted from the quantum dot layer, and a peak wavelength of the third light that passes through the band pass filter may be shorter than a peak wavelength of the third light emitted from the quantum dot layer.

The band pass filter may reflect at least a portion of the first light.

The band pass filter may include a short wave pass filter (SWPF) and a long wave pass filter (LWPF).

A cutoff wavelength of the SWPF may be shorter than or equal to about 655 nm, and a cutoff wavelength of the LWPF may be longer than or equal to about 500 nm.

The first light may be a blue light or an ultraviolet light, the second light may be a green light, and the third light may be a red light.

The plurality of quantum dots may include a core, the core including one of ZnSe, ZnO, ZnTe, InP, GaP, InGaN, or InN.

The plurality of quantum dots may further include a shell surrounding the core, the shell including one of ZnS, ZnSe, GaP, or GaN.

The embodiments may be realized by providing a display apparatus including a backlight unit; and a display panel that receives light from the backlight unit and displays an image, the display panel including a first substrate, a second substrate, and a liquid crystal layer between the first substrate and the second substrate, wherein the backlight unit includes a first region from which a first light is emitted, and a second region from which a second light and a third light are emitted, the second region including a light-emitting device that emits a first light; a quantum dot layer facing the light-emitting device, the quantum dot layer including a plurality of quantum dots, absorbing the first light, and emitting a second light and a third light that have different wavelength ranges compared to the first light; and a band pass filter on the quantum dot layer, the band pass filter cutting off a portion of the second light and a portion of the third light.

The first and second regions of the backlight may be adjacent to one corner of the display panel.

The backlight unit may include a first light guide that transmits the first light from the first region toward the display panel, and a second light guide that transmits the second light and the third light toward the display panel after having passed through the band pass filter.

The display panel may further include a color filter therein, the color filter reproducing a color.

The plurality of quantum dots may include a plurality of first quantum dots that absorb the first light and emit the second light, and a plurality of second quantum dots that absorb the first light and emit the third light.

The third light may have a longer wavelength than the second light, the band pass filter may cut off light in a shortest wavelength region of the second light, and the band pass filter may cut off light in a longest wavelength region of the third light.

The band pass filter may reflect at least a portion of the first light.

The first light may be a blue light or an ultraviolet light, the second light may be a green light, and the third light may be a red light.

The embodiments may be realized by providing a display apparatus including a substrate, the substrate being divided to define a first sub-pixel area for emitting a blue light, a second sub-pixel area for emitting a green light, and a third sub-pixel area for emitting a red light; a pixel electrode on the substrate; an opposite electrode facing the pixel electrode; an intermediate layer between the pixel electrode and the opposite electrode, the intermediate layer including a plurality of quantum dots and emitting and a band pass filter on one of the pixel electrode and the opposite electrode, the one of the pixel electrode and the opposite electrode being adjacent to a side of the apparatus at which light is emitted, wherein the band pass filter overlies the second sub-pixel area and the third sub-pixel area, and cuts off a portion of the green light and a portion of the red light.

The pixel electrode may include a first pixel electrode, a second pixel electrode, and a third pixel electrode, the first pixel electrode overlying the first sub-pixel are, the second pixel electrode overlying the second sub-pixel area, and the third pixel electrode overlying third sub-pixel area, the intermediate layer may include a first intermediate layer, a second intermediate layer, and a third intermediate layer, the first intermediate layer overlying the first sub-pixel area and including a plurality of quantum dots that emit the blue light, the second intermediate layer overlying the second sub-pixel area and including a plurality of quantum dots that emit the green light, and the third intermediate layer overlying third sub-pixel area and including a plurality of quantum dots that emit the red light, the first sub-pixel area may include a first light-emitting device on the substrate, the first light-emitting device including a sequential stack of the first pixel electrode, the first intermediate layer, and the opposite electrode, the second sub-pixel area may include a second light-emitting device on the substrate, the second light-emitting device including a sequential stack of the second pixel electrode, the second intermediate layer, and the opposite electrode, and the third sub-pixel area may include a third light-emitting device on the substrate, the third light-emitting device including a sequential stack of the third pixel electrode, the third intermediate layer, and the opposite electrode, the third pixel electrode.

The display apparatus may further include a color filter on the one of the pixel electrode or the opposite electrode that is adjacent to a side of the apparatus at which light is emitted, the color filter including a first region overlying the first sub-pixel area and through which the blue light passes; a second region overlying the second sub-pixel area and through which the green light passes; and a third region overlying the third sub-pixel area and through which the red light passes; wherein the intermediate layer includes a plurality of quantum dots that emit the blue light, a plurality of quantum dots that emit the green light, and a plurality of quantum dots that emit the red light, and the band pass filter overlies the second region and the third region of the color filter.

The quantum dots that emit the blue light, the quantum dots that emit the green light, and the quantum dots that emit the red light may include a same material as one another and have different sizes from one another.

The band pass filter may cut off light in a shortest wavelength region of the green light, and the band pass filter may cut off light in a longest wavelength region of the red light.

DETAILED DESCRIPTION

In the following embodiments, the terms “first” and “second” are used for the purpose of distinguishing one component from another component, not as a limiting meaning.

In the following embodiments, the terms in a singular form may include plural forms unless referred to the contrary.

In the following embodiments, the term “include”, “comprise”, “has”, “including”, “comprising”, or “having” means that there is a characteristic or component described in the specification and does not exclude that one or more other characteristics or components may be added.

In the following embodiments, when an element such as a film, region, or component is referred to as being “on” another element, it can be directly on another element or intervening elements may also be present.

FIG. 1illustrates a schematic sectional view of a quantum dot light-emitting device10according to an embodiment, andFIG. 2illustrates an expanded sectional view of part A1 of a quantum dot layer12included in the quantum dot light-emitting device10ofFIG. 1.

Referring toFIGS. 1 and 2, the quantum dot light-emitting device10may include a light-emitting device11(that emits a first light), the quantum dot layer12on or facing the light-emitting device11, and a band pass filter13on the quantum dot layer12. The quantum dot layer12may include a plurality of quantum dots, e.g., first and second quantum dots12aand12b, that absorb the first light and that emit a second light and a third light. The band pass filter13may block a portion of the second light and a portion of the third light.

The first light may be light that excites the first and second quantum dots12aand12bin the quantum dot layer12. In an implementation, the first light may be a blue light or an ultraviolet light. The light-emitting device11(emitting the first light) may include a plurality of light-emitting diodes (LEDs)11a(in which current flows in a semiconductor and light is emitted).

The first quantum dots12a(in the quantum dot layer12) may absorb the first light and emit the second light. The second quantum dots12b(in the quantum dot layer12) may absorb the first light that emit the third light.

A quantum dot is a spherical semiconductor nano material having a size of several nm to several hundred nm. For example, the quantum dot may include a core formed of a material having a small band gap and a shell surrounding the core. Due to a quantum confinement effect, the quantum dot may have discontinuous band gap energy, unlike a bulk state material. Thus, by introducing such a quantum dot into a light-emitting device, it is possible to implement a light-emitting device having high luminance efficiency and color purity.

For example, a quantum dot including cadmium (Cd) (e.g., cadmium selenide (CdSe)), may be suitable for implementing a light-emitting device having high photoluminescence quantum yield and narrow full width at half maximum (FWHM). However, cadmium (Cd) is a heavy metal element that is highly toxic and the Restriction of Hazardous Substances (RoHS) rule inhibits the usage of cadmium (Cd). Accordingly, a light-emitting device using a more environmentally friendly quantum dot may be desirable.

Thus, a quantum dot light-emitting device according to an embodiment may include environmentally friendly quantum dots, e.g., the first and second quantum dots12aand12b, which do not include a toxic heavy metal material, such as cadmium (Cd) or mercury (Hg). In an implementation, the first and second quantum dots12aand12bmay include a core that includes, e.g., one of ZnSe, ZnO, ZnTe, InP, GaP, InGaN, or InN.

The first and second quantum dots12aand12bmay further include a shell that surrounds the core and protects the core, thereby increasing fluorescence and stability of the first and second quantum dots12aand12b. In an implementation, the shell may include, e.g., one of ZnS, ZnSe, GaP, or GaN

As noted above, the first quantum dots12amay absorb the first light and may emit the second light. The second light may be, e.g., green light. The second quantum dots12bmay absorb the first light and may emit the third light. The third light may be, e.g., red light. In an implementation, the first quantum dots12aand the second quantum dots12bmay be formed of the same material and may have different sizes. In an implementation, the first quantum dot12aand the second quantum dot12bmay be formed of different materials.

For example, a quantum dot may have a characteristic an the interval between energy bands varies depending on a size of the quantum dot. As a result, even if the same quantum dots (e.g., quantum dots formed of the same material) are used, it is possible to emit light having different wavelengths when the size of the quantum dots is different. The smaller the quantum dot is in size, the larger its energy band gap may be Thus, the wavelength of an emitted light may be shortened.

In an implementation, first quantum dots12a(that emit the second light) may be smaller in size than the second quantum dots12b(that emit the third light). For example, the third light may have a longer wavelength than the second light. In an implementation, the second light may be green light (of which a central wavelength thereof is about 530±5 nm and of which the FWHM is about 40 to 60 nm), and the third light may be red light (of which a central wavelength thereof is about 625±5 nm and of which the FWHM is about 40 to 60 nm).

The band pass filter13may be on the quantum dot layer12. The band pass filter13may transmit a portion of the second light and a portion of the third light, and may reflect or absorb remaining portions of the second light and the third light. By including the band pass filter13, the quantum dot light-emitting device10according to an embodiment may help enhance the characteristics of the environmentally friendly quantum dots, e.g., the first and second quantum dots12aand12b(which may not exhibit as good a photoluminescence quantum yield or a FWHM, compared to a quantum dot including cadmium (Cd)). A detailed configuration of the band pass filter13may be as follows:

FIG. 3illustrates a graph of a transmission spectrum of the band pass filter13included in the quantum dot light-emitting device10ofFIG. 1, andFIG. 4illustrates a graph of spectra of lights before and after passing through the band pass filter13ofFIG. 3, after being emitted from the quantum dot layer12of the quantum dot light-emitting device10ofFIG. 1.

Referring toFIGS. 1 and 3, the band pass filter13of the quantum dot light-emitting device10according to an embodiment may include a long wave pass filter (LWPF)13aand a short wave pass filter (SWPF)13b.

The LWPF13aand the SWPF13bmay have structures in which a high refraction layer and a low refraction layer are alternately stacked. In an implementation, a cutoff wavelength of the LWPF13amay be equal to or longer than about 500 nm (e.g., about 500 nm or longer), and a cutoff wavelength of the SWPF13bmay be shorter than or equal to about 655 nm (e.g., about 655 nm or shorter).

Referring back toFIG. 1, in an implementation, a short wavelength range of a green light may be cut off by the LWPF13a, a long wavelength range of a red light may be cut off by the SWPF13b, and a blue light (e.g., all blue light in a blue wavelength range) may be cut off, e.g., reflected or absorbed by the LWPF13a. For example, a portion of the green light (e.g., second light) having a relatively shorter wavelength may be cut off by the LWPF13a, and a portion of the red light (e.g., third light) having a relatively longer wavelength may be cut off by the SWPF13b. For example, the band pass filter may cut off light in a shortest wavelength region of the second light and may cut off light in a longest wavelength region of the third light.

In the description above, FWHM refers to a maximum difference of two points corresponding to a location that has ½ of a maximum transmittance, at the transmission spectrum of the band pass filter13. The cutoff wavelength refers to a wavelength value corresponding to a place that has ½ of maximum transmittance, at the transmission spectrum of the band pass filter.

InFIG. 4, spectra of second and third lights before passing through the band pass filter13ofFIG. 3(after being emitted from the quantum dot layer12according to the present embodiment) are compared with spectra of second and third lights (after being emitted from the quantum dot layer12according to the present embodiment and then passing through the band pass filter13ofFIG. 3).

The band pass filter13may transmit light of a longer or longest wavelength range of the second light, and may transmit light of a shorter or shortest wavelength range of the third light. For example, the band pass filter13may cut off light of a relatively shorter wavelength range (e.g., a shortest wavelength region) of the second light, and may cut off light of a relatively longer wavelength range (e.g., a longest wavelength region) of the third light. As a result, the FWHM of the second light and the third light may be narrowed.

Referring toFIG. 4, a peak wavelength of the second light that is transmitted through the band pass filter13may be longer than that of the second light that is emitted from the quantum dot layer12(e.g., prior to passing through the band pass filter13). A peak wavelength of the third light that is transmitted through the band pass filter13may be shorter than that of the third light that is emitted from the quantum dot layer12(e.g., prior to passing through the band pass filter13).

For example, the FWHM of the second light and the third light that are emitted from the quantum dot layer12may narrow, and peak wavelengths may shift.

In addition, the cutoff wavelength of the LWPF13a(included in the band pass filter13) may be equal to or longer than about 500 nm, and at least a portion of a first light having a wavelength shorter than a green light, e.g., a blue light or an ultraviolet light, may be reflected by the band pass filter13.

The portion of the first light that is reflected by the band pass filter13may re-enter the quantum dot layer12, the first light having re-entered the quantum dot layer12may excite the quantum dots12aand12b, and the quantum dot layer12may re-emit the second light and the third light by using the re-entered blue or first light.

For example, the first (e.g., blue) light may be reflected (and not transmitted) by the band pass filter13, and may repetitively enters the quantum dot layer12, and it is possible to enhance the luminance efficiency of the quantum dot light-emitting device10according to an embodiment.

FIG. 5illustrates a schematic sectional view of a display apparatus100according to an embodiment.

Referring toFIG. 5, the display apparatus100according to an embodiment may include a backlight unit110and a display panel120(that receives lights from the backlight unit110). The display panel120may display an image, and may include a first substrate122, a second substrate125, and a liquid crystal layer123between the first substrate122and the second substrate125.

The backlight unit110may include a first region P1 (that emits a first light) and a second region P23 (that emits a second light and a third light). The second region P23 (that emits the second light and the third light) may include the quantum dot light-emitting device10ofFIG. 1. The quantum dot light-emitting device10may include a light-emitting device11(that emits a first light), a quantum dot layer12(that includes a plurality of quantum dots, absorbs the first light, and emits the second light and the third light that have different wavelength range from the first light), and a band pass filter13(that is on the quantum dot layer12and that cuts off a portion of the second light and a portion of the third light.)

The first region P1 (that emits the first light) and the second region P23 (that emits the second light and the third light) may be arranged on regions corresponding to one corner of the display panel120. For example, the first region P1 and the second region P23 may be adjacent to a corner of the display panel120. The backlight unit110may further include a first light guide30(that transmits the first light emitted to or toward the display panel120) and a second light guide40(that transmits the second light and the third light to or toward the display panel120, e.g., by way of the first light guide

The first region P1 (that emits the first light) may include a light-emitting diode package20including a plurality of light-emitting diodes (LEDs) that emit the first light. The second region P23 (that emits the second light and the third light) may include the quantum dot light-emitting device10ofFIG. 1as described above.

The first light guide30and the second light guide40may be arranged under the display panel120. Edges of the first light guide30and the second light guide40may face the first region P1 (that emits the first light) and second region P23 (that emits the second light and the third light), e.g., respectively.

The first light may be transmitted to the display panel120through the first light guide30. The second light and the third light may be transmitted to or toward the display panel120through the second light guide40(e.g., and then through the first light guide30). The first to third lights may correspond to or may be a blue light, a green light, and a red light, respectively. The backlight unit110according to the present embodiment may make or provide a white light by a combination of the first to third lights.

The quantum dot layer12of the quantum dot light-emitting device10may include a plurality of first quantum dots (12ainFIG. 2) that absorb the first light and that emit the second light, and a plurality of second quantum dots (12binFIG. 2) that absorb the first light and that emit the third light. The band pass filter13may cut off a portion of light of a relatively shorter wavelength range (e.g., a shortest wavelength region) from the second light, and may cut off a portion of light of a relatively longer wavelength range (e.g., a longest wavelength region) from the third light, and may decrease the FWHM of the second and third lights.

In addition, the band pass filter13may reflect at least a portion of the first light, the reflected first light may re-enter the quantum dot layer12, and it is possible to recycle the reflected first light and thus enhance the luminance efficiency of the quantum dot light-emitting device10. Related detailed descriptions are provided above and thus may be omitted.

The display panel120may include a first substrate122, a second substrate125, and a liquid crystal layer123between the first substrate122and the second substrate125. The first substrate122may include wirings and devices, e.g., thin film transistors (TFTs) (not shown). A first electrode (not shown) may be on the first substrate122.

In order to realize colors, a color filter layer124may be on a surface of the second substrate125, on which the liquid crystal layer123is arranged. The color filter layer124may include, e.g., a color filter124aand a black matrix124b(that separates the color filter124afrom another color filter124a).

In addition, a second electrode (not shown) may be on a surface of the color filter layer124, on which the liquid crystal layer123is arranged.

The display apparatus100according to the present embodiment may allow current to flow between the first electrode (not shown) and the second electrode (not shown), and may control the on/off of a light emitted according to the alignment of liquid crystals according to the on/off of currents.

The color filter layer124may include, e.g., a region that transmits a blue light, a region that transmits a green light, and a region that transmits a red light, and may realize colors on the display apparatus100by using transmitted lights.

Polarizing plates121and126may be respectively arranged on outer surfaces of the first substrate122and the second substrate125, and various optical sheets (not shown) may be arranged between the backlight unit110and the display panel120.

FIG. 6illustrates a graph of spectra before and after light emitted from a backlight unit included in the display apparatus100ofFIG. 5passes through a color filter.FIG. 7illustrates a graph comparing a spectrum after light emitted from the backlight unit110included in the display apparatus100ofFIG. 5passes through a color filter, with a spectrum after light emitted from another backlight unit (that includes cadmium (Cd)) passes through a color filter.

Referring toFIG. 6, a first light Blue (that is emitted from the first region P1 of the backlight unit110ofFIG. 5), a second light Green and a third light Red (that are emitted from the quantum dot light-emitting device10included the second region P23) may enter a color filter C/F.

The graph at the center ofFIG. 6represents a transmission spectrum of the color filter C/F itself, and the color filter C/F may have a transmittance of the color filter itself for a blue light, a green light, and a red light.

The first to third lights (that have entered the color filter) may pass through the color filter and then may have spectra corresponding to the lowest or bottom graph ofFIG. 6.

FIG. 7illustrates a graph that compares intensities of a blue light, a green light, and a red light according to a wavelength (after lights emitted from the quantum dot light-emitting device10according to an embodiment pass through a color filter) with intensities of blue light, green light, and red light according to wavelength (after lights emitted from a quantum dot light-emitting device that includes cadmium (Cd) pass through a color filter).

For example, the quantum dot light-emitting device10according to an embodiment may include environmentally friendly quantum dots, e.g., without a toxic material such as cadmium (Cd), and may include the band pass filter13in order to help improve the characteristics of the environmentally friendly quantum dots. InFIG. 7, it may be seen that the quantum dot light-emitting device10according to the present embodiment may have similar characteristics to the other quantum dot light-emitting device that includes cadmium (Cd).

FIG. 8illustrates a graph of a color reproduction range of the quantum dot light-emitting device10ofFIG. 1. Table 1, below, represents color reproduction ratios of a quantum dot light-emitting device that includes cadmium (Cd) and the quantum dot light-emitting device10(e.g., according to an embodiment and free of cadmium (Cd)) ofFIG. 1and sRGB gamut match ratios.

Referring toFIG. 8and Table 1, the color reproduction ratios of the lights emitted from the quantum dot light-emitting device that includes cadmium (Cd) and the quantum dot light-emitting device10ofFIG. 1(not including cadmium (Cd) and including the band pass filter13) may be significantly or substantially similar to each other. For example, in a match ratio with respect to sRGB, two cases both were 100%, and in a match ratio with respect to NTSC, the case including cadmium (Cd) was 94.9% and the case not including cadmium (Cd) was 93.5%.

For example, it may be seen that the quantum dot light-emitting device10ofFIG. 1according to an embodiment had similar characteristics to a light-emitting device including cadmium (Cd), even in terms of a color reproduction ratio.

FIG. 9illustrates a schematic sectional view of a display apparatus200according to another embodiment.

Referring toFIG. 9, the display apparatus200according to the present embodiment may include a substrate210that is divided into and/or defines a first sub-pixel area Pb, a second sub-pixel area Pg, and a third sub-pixel area Pr at which a blue light B, a green light G, and a red light B are emitted, respectively. The first sub-pixel area Pb may include a first light-emitting device thereon that includes a sequentially stacked first pixel electrode220a, first intermediate layer240a(including a plurality of quantum dots that emit a blue light), and opposite electrode250on the substrate210. The second sub-pixel area Pg may include a second light-emitting device thereon that includes a sequentially stacked second pixel electrode220b, second intermediate layer240b(including a plurality of quantum dots that emit a green light), and opposite electrode250on the substrate210. The third sub-pixel area Pr may include a third light-emitting device thereon that includes a sequentially stacked third pixel electrode220c, third intermediate layer240c(including a plurality of quantum dots that emit a red light), and opposite electrode250on the substrate210.

Each sub-pixel area may be divided by a pixel-defining layer230, and an encapsulation substrate270(that protects the first to third light-emitting devices) may be arranged on the opposite electrode250.

In an implementation, the first pixel electrode220a, the second pixel electrode220b, and the third pixel electrode220cmay be reflective electrodes, and the opposite electrode250may be a transparent or translucent electrode.

For example, the display apparatus200according to the present embodiment may be a top emission type, in which a light may be emitted toward the opposite electrode250.

The first intermediate layer240a, the second intermediate layer240b, and the third intermediate layer240cmay include a plurality of quantum dots that emit a blue light, a green light, and a red light, respectively. In an implementation, in addition to a quantum dot layer, the intermediate layers240a,240b,240cmay further include at least one of a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and an electron injection layer (EIL).

The display apparatus200according to the present embodiment may be a self-emitting type display apparatus in which excitons that are generated when holes injected from the first to third pixel electrodes220ato220cand electrons injected from the opposite electrode250are combined at the quantum dot layer and generate a light while dropping from an excited state to a ground state.

As described above, a quantum dot may have a discontinuous energy band by a quantum confinement effect, the display apparatus200according to the present embodiment may emit lights having high luminance efficiency and color purity.

The quantum dots included in the first to third intermediate layers240ato240caccording to the present embodiment may be formed of the same material and may have different sizes. For example, the quantum dot included in the first intermediate layer240amay be the smallest, and the quantum dot included in the third intermediate layer240cmay be the largest.

The quantum dots may be environmentally friendly quantum dots that do not include a toxic heavy metal material, e.g., cadmium (Cd) or mercury (Hg). In an implementation, the quantum dots may include a core that includes, e.g., one of ZnSe, ZnO, ZnTe, InP, GaP, InGaN, or InN. In an implementation, the quantum dots may include a shell that includes, e.g., one of ZnS, ZnSe, GaP, or GaN.

The display apparatus200according to the present embodiment may include, on the opposite electrode250, a band pass filter260that cuts off a portion of a green light and a portion of a red light. The band pass filter260may be arranged on an inner region of the encapsulation substrate270corresponding to or overlying the second sub-pixel area Pg and the third sub-pixel area Pr.

The band pass filter260according to the present embodiment may be arranged to be common to, e.g., may continuously overlie, the second sub-pixel area Pg and the third sub-pixel area Pr. The band pass filter260may include an LWPF261and an SWPF262.

According to the configuration above, the display apparatus200may include as a light-emitting layer that is an environmentally friendly quantum dot layer (e.g., that does not include cadmium (Cd)), and may decrease the FWHM of a green light G and a red light R using the band pass filter260, thereby increasing color purity.

FIG. 10illustrates a schematic sectional view of a display apparatus300according to another embodiment.

Referring toFIG. 10, the display apparatus300according to the present embodiment may include a substrate310that is divided into and/or defines a first sub-pixel area Pb, a second sub-pixel area Pg, and a third sub-pixel area Pr at which a blue light, a green light, and a red light are emitted, respectively. The first sub-pixel area Pb may include a first light-emitting device thereon that includes a sequentially stacked first pixel electrode320a, first intermediate layer340aincluding a plurality of quantum dots that emit a blue light, and opposite electrode350on the substrate310. The second sub-pixel area Pg may include a second light-emitting device thereon that includes a sequentially stacked second pixel electrode320b, second intermediate layer340bincluding a plurality of quantum dots that emit a green light, and opposite electrode250on the substrate310. The third sub-pixel area Pr may include a third light-emitting device thereon that includes a sequentially stacked third pixel electrode320c, a third intermediate layer340cincluding a plurality of quantum dots that emit a red light, and opposite electrode350on the substrate310.

Each sub-pixel area may be divided by a pixel-defining layer330, and an encapsulation substrate370(that protects the first to third light-emitting devices) may be on the opposite electrode350.

In an implementation, the first pixel electrode320a, the second pixel electrode320b, and the third pixel electrode320cmay be transparent or translucent electrodes, and the opposite electrode350may be a reflective electrode.

For example, the display apparatus300according to the present embodiment may be a bottom emission type, in which a light is emitted toward the first to third pixel electrodes320ato320c.

The first intermediate layer340a, the second intermediate layer340b, and the third intermediate layer340cmay include a plurality of quantum dots that emit a blue light, a green light, and a red light, respectively. The quantum dots may be formed of the same material and may have different sizes. For example, the quantum dot included in the first intermediate layer340amay be the smallest, and the quantum dot included in the third intermediate layer340cmay be the largest.

The quantum dots may be environmentally friendly quantum dots that do not include a toxic heavy metal material, e.g., cadmium (Cd) or mercury (Hg). The quantum dots may include a core that includes, e.g., one of ZnSe, ZnO, ZnTe, InP, GaP, InGaN, or InN. The quantum dots may include a shell that includes, e.g., one of ZnS, ZnSe, GaP, or GaN.

The display apparatus300according to the present embodiment may include a band pass filter360that cuts off a portion of a green light and a portion of a red light. In an implementation, the band pass filter360may be arranged only on outer regions of the substrate310corresponding to or overlying the second sub-pixel area Pg and the third sub-pixel area Pr. In an implementation, the band pass filter360may also be arranged between the second and the third pixel electrodes320band320cand the substrate310.

The band pass filter360according to the present embodiment may be arranged to be common to, e.g., may continuously overlie, the second sub-pixel area Pg and the third sub-pixel area Pr. The band pass filter360may include an LWPF361and an SWPF362.

FIG. 11illustrates a schematic sectional view of a display apparatus400according to another embodiment, andFIG. 12illustrates an expanded sectional view of part A2 of an intermediate layer440included in the display apparatus400ofFIG. 11.

Referring toFIGS. 11 and 12, the display apparatus400according to the present embodiment may include a substrate410(that is divided into or defines a first sub-pixel area Pb, a second sub-pixel area Pg, and a third sub-pixel area Pr at which a blue light B, a green light G, and a red light R are emitted, respectively). The display apparatus400may include a pixel electrode420, an intermediate layer440(that includes a plurality of quantum dots and that emits lights), and an opposite electrode450that are sequentially stacked on the substrate410.

The pixel electrode420may be a reflective electrode, and the opposite electrode450may be a transparent or translucent electrode.

For example, the display apparatus400according to the present embodiment may be a top emission type in which a light is emitted toward the opposite electrode450.

The intermediate layer440may include a plurality of quantum dots Qb that emit a blue light, a plurality of quantum dots Qg that emit a green light, and a plurality of quantum dots Qr that emit a red light. In an implementation, in addition to the quantum dots Qb, Qg, and Qr, the intermediate layer440may further include at least one of an HIL, an HTL, an ETL, or an EIL. The quantum dots Qb, Qg, and Qr may be formed of the same material and may have different sizes, according to the wavelength of an emitted light. In addition, the quantum dots Qb, Qg, and Qr may not include a heavy metal, e.g., cadmium (Cd).

The display apparatus400according to the present embodiment may emit a light when excitons drop from an excited state to a ground state. The excitons may be generated by combining holes injected from the pixel electrode420and electrons injected from the opposite electrode250in a quantum dot layer that includes the quantum dots Qb, Qg, and Qr. For example, the intermediate layer440may emit a white light.

A color filter480(for reproducing a color on the display apparatus400) may be included on the opposite electrode430. The color filter480may include a first region480a(overlying the first sub-pixel area Pb and transmitting a blue light), a second region480b(overlying the second sub-pixel area Pg and transmitting a green light), and a third region480c(overlying the third sub-pixel area Pr and transmitting a red light).

A band pass filter460may be included on regions of the color filter480corresponding to or overlying the second sub-pixel area Pg and the third sub-pixel area Pr, e.g., on or overlying the second region480band the third region480cof the color filter480.

The band pass filter460according to the present embodiment may be arranged to be common to, e.g., may continuously overlie, the second sub-pixel area Pg and the third sub-pixel area Pr. The band pass filter460may include an LWPF461and an SWPF462. The band pass filter460may reflect or absorb portions of a green light and a red light emitted from the intermediate layer440to decrease the FWHM of the green light and the red light that is externally emitted, thereby enhancing the color purity of the display apparatus400.

An encapsulation substrate470may be on the band pass filter460.

In an implementation, the band pass filter460is between the encapsulation substrate470and the color filter480. In an implementation, the band pass filter460may be on an outer surface of the encapsulation substrate470.

FIG. 13illustrates a schematic sectional view of a display apparatus500according to another embodiment.

Referring toFIG. 13, the display apparatus500according to the present embodiment may include a substrate510that is divided into or defines a first sub-pixel area Pb, a second sub-pixel area Pg, and a third sub-pixel area Pr at which a blue light, a green light, and a red light are emitted, respectively. The display apparatus500may further include a pixel electrode520, an intermediate layer540(that includes a plurality of quantum dots and emits light), and an opposite electrode550, that are sequentially stacked on the substrate510.

The pixel electrode520may be a transparent or translucent electrode, and the opposite electrode450may be a reflective electrode.

For example, the display apparatus500according to the present embodiment may be a bottom emission type in which a light is emitted toward the pixel electrode520.

The intermediate layer540may include a plurality of quantum dots (Qb inFIG. 12) that emit a blue light, a plurality of quantum dots (Qg inFIG. 12) that emit a green light, and a plurality of quantum dots (Qr inFIG. 12) that emit a red light. In addition to a quantum dot layer, the intermediate layer540may further include at least one of an HIL, an HTL, an ETL, or an EIL. The quantum dots Qb, Qg, and Qr may be formed of the same material and may have different sizes, according to the wavelength of an emitted light. In addition, the quantum dots Qb, Qg, and Qr may not include a toxic heavy metal, e.g., cadmium (Cd).

The display apparatus500according to the present embodiment may emit light when excitons drop from an excited state to a ground state. The excitons may be generated by combining holes injected from the pixel electrode520and electrons injected from the opposite electrode550in a quantum dot layer including the quantum dots Qb, Qg, and Qr. For example, the intermediate layer540may emit a white light.

A color filter580(for reproducing a color) may be included on a surface of the pixel electrode520through which light is emitted. The color filter580may include a first region580aoverlying the first sub-pixel area Pb and transmitting a blue light, a second region580boverlying the second sub-pixel area Pg and transmitting a green light, and a third region580coverlying the third sub-pixel area Pr and transmitting a red light.

A band pass filter560may be on regions of a surface of the color filter580through which light is emitted and corresponding to or overlying the second sub-pixel area Pg and the third sub-pixel area Pr, e.g., on the second region580band the third region580cof the color filter580.

The band pass filter560according to the present embodiment may be arranged to be common to, e.g., may continuously overlie, the second sub-pixel area Pg and the third sub-pixel area Pr. The band pass filter560may include an LWPF561and an SWPF562. The band pass filter560may reflect or absorb portions of a green light and a red light emitted from the intermediate layer540to decrease the FWHM of the green light and the red light that are or end up being externally emitted, thereby enhancing the color purity of the display apparatus500.

In an implementation, the color filter580and the band pass filter560may be between the substrate510and the pixel electrode520. In an implementation, the color filter580and the band pass filter560may also be on an outer surface of the substrate510.

The quantum dot light-emitting device and the display apparatus according to the embodiments may have a narrow FWHM and high luminance efficiency because or even though, e.g., cadmium (Cd), is not used. Thus, the quantum dot light-emitting device and the display apparatus may be environmentally friendly.