LIGHT EMITTING DISPLAY DEVICE

A light emitting display device includes a first electrode, a second electrode, an opposing electrode, a first light emitting layer, and a second light emitting layer. The opposing electrode is on the first and second electrodes. The first light emitting layer is between the first electrode and the opposing electrode. The second light emitting layer is between the second electrode and the opposing electrode. The first light emitting layer and the second light emitting layer emit light of different colors. The first light emitting layer includes semiconductor nanocrystals. The second light emitting layer includes an organic material.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2017-0029909, filed on Mar. 9, 2017, and entitled, “Light Emitting Display Device,” is incorporated by reference herein in its entirety.

BACKGROUND

One or more embodiments herein relate to a light emitting display device.

2. Description of the Related Art

A variety of flat panel displays have been developed. Examples include liquid crystal displays, field emission displays, plasma display panels, devices, and organic light emitting diode (OLED) displays. OLED displays have pixels which emit light using OLEDs. The OLEDs generate light based on a recombination of electrons and holes in an organic light emitting layer.

SUMMARY

In accordance with one or more embodiments, a light emitting display device includes a substrate; a first electrode and a second electrode on the substrate; an opposing electrode on the first electrode and the second electrode; a first light emitting layer between the first electrode and the opposing electrode; and a second light emitting layer between the second electrode and the opposing electrode, wherein the first light emitting layer and the second light emitting layer are to emit light of different colors, the first light emitting layer includes semiconductor nanocrystals, and the second light emitting layer includes an organic material. The first light emitting layer may emit red light and the second light emitting layer may emit blue light.

The display device may include a third electrode on the substrate and a third light emitting layer between the third electrode and the opposing electrode, wherein the first light emitting layer, the second light emitting layer, and the third light emitting layer may emit different color light. The third light emitting layer may include semiconductor nanocrystals.

The display device may include the first light emitting layer is to emit red light, the second light emitting layer is to emit blue light, and the third light emitting layer is to emit green light. The semiconductor nanocrystals may include at least one of an InP-based material, a CIS-based material, and an InGaP-based material. The organic material may include an anthracene-based material.

The display device may include a hole transport layer between the first electrode and the first light emitting layer, between the second electrode and the second light emitting layer, and between the third electrode and the third light emitting layer. The hole transport layer may include a first hole transport layer, a second hole transport layer, and a third hole transport layer separated from each other.

The first hole transport layer may be between the first electrode and the first light emitting layer, the second hole transport layer may be between the second electrode and the second light emitting layer, and the third hole transport layer may be between the third electrode and the third light emitting layer.

The display device may include a hole injection layer between the hole transport layer and the first electrode, between the hole transport layer and the second electrode, and between the hole transport layer and the third electrode. The hole injection layer may include a first hole injection layer, a second hole injection layer, and a third hole injection layer which are separated from each other.

The first hole injection layer may be between the hole transport layer and the first electrode, the second hole injection layer may be between the hole transport layer and the second electrode, and the third hole injection layer be between the hole transport layer and the third electrode.

The display device may include an electron transport layer between the first light emitting layer and the opposing electrode, between the second light emitting layer and the opposing electrode, and between the third light emitting layer and the opposing electrode. The electron transport layer may include a first electron transport layer, a second electron transport layer, and a third electron transport layer separated from each other.

The first electron transport layer may be between the first light emitting layer and the opposing electrode, the second electron transport layer may be between the second light emitting layer and the opposing electrode, and the third electron transport layer may be between the third light emitting layer and the opposing electrode. An electron injection layer may be between the electron transport layer and the opposing electrode. The electron injection layer may include a first electron injection layer, a second electron injection layer, and a third electron injection layer separated from each other. The semiconductor nanocrystals may generate light based on a current generated by a voltage of the first electrode and a voltage of the opposing electrode.

In accordance with one or more other embodiments, a light emitting display device includes a substrate; a first light emitting layer on the substrate; and a second light emitting layer adjacent to the first light emitting layer, wherein the first light emitting layer includes an organic light emitting material which generates light of a first color and wherein the second light emitting layer includes an inorganic semiconductor light emitting material which generates light of a second color different from the first color.

DETAILED DESCRIPTION

Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings. Although the invention may be modified in various manners and have several exemplary embodiments, exemplary embodiments are illustrated in the accompanying drawings and will be mainly described in the specification. However, the scope of the invention is not limited to the exemplary embodiments and should be construed as including all the changes, equivalents and substitutions included in the spirit and scope of the invention.

In the drawings, thicknesses of a plurality of layers and areas are illustrated in an enlarged manner for clarity and ease of description thereof. When a layer, area, or plate is referred to as being “on” another layer, area, or plate, it may be directly on the other layer, area, or plate, or intervening layers, areas, or plates may be present therebetween. Conversely, when a layer, area, or plate is referred to as being “directly on” another layer, area, or plate, intervening layers, areas, or plates may be absent therebetween. Further when a layer, area, or plate is referred to as being “below” another layer, area, or plate, it may be directly below the other layer, area, or plate, or intervening layers, areas, or plates may be present therebetween. Conversely, when a layer, area, or plate is referred to as being “directly below” another layer, area, or plate, intervening layers, areas, or plates may be absent therebetween.

Throughout the specification, when an element is referred to as being “connected” to another element, the element is “directly connected” to the other element, or “electrically connected” to the other element with one or more intervening elements interposed therebetween. It will be further understood that the terms “comprises,” “including,” “includes” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

Some of the parts which are not associated with the description may not be provided in order to specifically describe embodiments of the present invention and like reference numerals refer to like elements throughout the specification.

FIG. 1illustrates an embodiment of a light emitting display device which includes a display panel111, a scan driver151, a data driver153, a timing controller122, and a power supply portion123.

The display panel111includes a plurality of scan lines SL1to SLi, a plurality of data lines DL1to DLj, and a power line VL for transmitting various signals for a plurality of pixels PX that emit light to display image. Here, i is a natural number greater than 2 and j is a natural number greater than 3. The power line VL includes a first driving power line VDL and a second driving power line VSL which are electrically separated from each other.

The pixels PX are arranged in matrix form in the display panel111. The pixels PX include, for example, a red pixel to emit red light, a green pixel to emit green light, and a blue pixel to emit blue light. The pixels PX may emit one or more different colors of light in another embodiment. For example, the display panel111may additionally or alternately include a white pixel for emitting white light.

A system outside the display panel111outputs various control signals (e.g., a vertical synchronization signal, a horizontal synchronization signal, a clock signal) and image data through an interface circuit using, for example, a low voltage differential signaling (LVDS) transmitter of a graphics controller. The vertical synchronization signal, the horizontal synchronization signal, and the clock signal are applied to the timing controller122, and the image data sequentially output from the system are also applied to the timing controller122.

The timing controller122generates a data control signal DCS and a scan control signal SCS based on the horizontal synchronization signal, the vertical synchronization signal, and the clock signal input to the timing controller122. The data control signal DCS and the scan control signal SCS are output to the data driver153and the scan driver151, respectively. The data control signal DCS is applied to the data driver153and the scan control signal SCS is applied to the scan driver151.

The data control signal DCS includes, for example, a dot clock, a source shift clock, a source enable signal, and a polarity inversion signal. The scan control signal SCS includes a gate start pulse, a gate shift clock, and a gate output enable.

The data driver153samples image data signals DATA according to the data control signal DCS from the timing controller122, latches the sampled image data signals corresponding to one horizontal line in each horizontal time (1H,2H, . . . ), and applies the latched image data signals to the data lines DL1to DLj. For example, the data driver153converts the image data signal DATA from the timing controller122to an analog signal using a gamma voltage input from the power supply portion123. The analog signals are applied to the data lines DL1to DLj. In addition, the data driver153may generate an initialization signal and a dummy signal, and the data driver153applies the initialization signal and the dummy signal to the data lines DL1to DLj.

The scan driver151includes a shift register and level shifter. The shift register generates scan signals based on the gate start pulse SCS from the timing controller122. The level shifter shifts the scan signals to have a voltage level suitable for driving the pixels PX. The scan driver151applies first to i-th scan signals to the scan lines SL1to SLi, respectively, based on the scan control signal SCS from the timing controller122.

The power supply portion123generates the gamma voltage, a first driving signal ELVDD, and a second driving signal ELVSS. The power supply portion123applies the first driving signal ELVDD to the first driving power line VDL and the second driving signal ELVSS to the second driving power line VSL.

FIG. 2illustrates a circuit embodiment of a pixel, which, for example, may be representative of the pixels PX ofFIG. 1. InFIG. 2, an n-th pixel PXn is illustrated to include a first switching element Tr1, a second switching element Tr2, a storage capacitor Cst, and a light emitting element (LED).

The first switching element Tr1includes a gate electrode connected to an n-th scan line SLn, and is connected between an m-th data line DLm and a first node N1. One of a drain electrode and a source electrode of the first switching element Tr1is connected to the m-th data line DLm. The other of the drain electrode and the source electrode of the first switching element Tr1is connected to the first node N1. For example, the drain electrode of the first switching element Tr1is connected to the m-th data line DLm, and the source electrode of the first switching element Tr1is connected to the first node N1, where m is a natural number.

The second switching element Tr2includes a gate electrode connected to the first node N1, and is connected between the first driving power line VDL and an anode electrode of the light emitting element LED. One of a drain electrode and a source electrode of the second switching element Tr2is connected to the first driving power line VDL. The other of the drain electrode and the source electrode of the second switching element Tr2is connected to a second node N2. For example, the drain electrode of the second switching element Tr2is connected to the first driving power line VDL through a third node N3, and the source electrode of the second switching element Tr2is connected to the second node N2.

The second switching element Tr2adjusts an amount (density) of a driving current flowing from the first driving power line VDL to the second driving power line VSL according to a magnitude of a signal applied to the gate electrode of the second switching element Tr2.

The storage capacitor Cst is connected between the first node N1and the second node N2. The storage capacitor Cst stores a signal applied to the gate electrode of the second switching element Tr2for one frame period.

The light emitting element LED is connected between the second node N2and the second driving power line VSL. The light emitting element LED includes an anode electrode connected to the second node N2and a cathode electrode connected to the second driving power line VSL. The light emitting element LED emits light in accordance with the driving current applied through the second switching element Tr2. The LED emits light of different brightness depending on the magnitude of the driving current.

The red pixel includes a red light emitting element LED that emits red light. The green pixel includes a green light emitting element LED that emits green light. The blue pixel includes a blue light emitting element LED that emits blue light.

FIG. 3illustrates an embodiment of a portion of a display panel, which, for example, may correspond to display panel111ofFIG. 1.FIG. 4illustrates a cross-sectional view taken along line I-I′ ofFIG. 3.FIG. 5is a cross-sectional view taken along line II-II′ ofFIG. 3.

Referring toFIGS. 3, 4, and 5, the display panel111includes a substrate110, a pixel circuit portion130on the substrate110, a light emitting element LED1on the pixel circuit portion130, and a sealing member250on the light emitting element LED1. One pixel PX1may be located at an area defined by a gate line151, a data line171, and a first driving power line172or VDL.

The pixel circuit portion130for driving the light emitting element LED1is on the substrate110and includes a first switching element Tr1, a second switching element Tr2, and a storage capacitor Cst. The pixel circuit portion130drives the light emitting element LED1. Examples of the pixel circuit portion130and the light emitting element LED1are illustrated inFIGS. 3 and 4. The pixel circuit portion130and the light emitting element LED1may have different structures in other embodiments.

Referring toFIG. 3, one pixel PX1includes two switching elements Tr1and Tr2and one storage capacitor Cst. The one pixel PX1may include a different number of thin film transistors and/or capacitors in another exemplary embodiment, e.g., three or more thin film transistors and two or more capacitors and may have various or different structures including additional signal lines.

A pixel PX1may refer to a smallest unit for emitting light to display images. The pixel may be, for example, a red pixel to emit red light, green pixel to emit green light, or a blue pixel to emit blue light. For example, a first pixel PX1may be a red pixel including a red light emitting element, a second pixel PX2may be a green pixel including a green light emitting element, and a third pixel PX3may be a blue pixel including a blue light emitting element.

Referring toFIGS. 3 and 4, one pixel PX1includes a first switching element Tr1, a second switching element Tr2, a storage capacitor Cst, and a light emitting element LED1. In such an exemplary embodiment, a configuration including the first switching element Tr1, the second switching element Tr2, and the storage capacitor Cst may be referred to as a pixel circuit portion130.

The pixel circuit portion130includes a gate line151arranged along one direction and a data line171and a first driving power line172insulated from the gate line151.

A buffer layer120may be on the substrate110to prevent permeation of undesirable elements (e.g., debris, moisture, etc.) and planarize a surface therebelow. The buffer layer120may include suitable materials for planarizing and/or preventing permeation. For example, the buffer layer120may include a silicon nitride (SiNx) layer, a silicon oxide (SiO2) layer, or a silicon oxynitride (SiOxNy) layer. In another embodiment, the buffer layer120may be omitted depending, for example, on the kinds of the substrate110and process conditions thereof.

A first semiconductor layer131and a second semiconductor layer132are on the buffer layer120. The first semiconductor layer131and the second semiconductor layer132may include a polycrystalline silicon layer, an amorphous silicon layer, or an oxide semiconductor such as indium gallium zinc oxide (IGZO) and indium zinc tin oxide (IZTO). When the second semiconductor layer132ofFIG. 4includes a polycrystalline silicon layer, the second semiconductor layer132includes a channel area which is not doped with impurities and p+ doped source and drain areas which are on opposite sides of the channel area. In such an exemplary embodiment, p-type impurities (e.g., boron B) may be used as dopant ions and B2H6is typically used. Such impurities may vary depending on the kinds of a thin film transistors (TFT).

The second switching element Tr2employs a p-channel metal oxide semiconductor (PMOS) TFT including p-type impurities. In one embodiment, the second switching element Tr2may employ an n-channel metal oxide semiconductor (NMOS) TFT or a complementary metal oxide semiconductor (CMOS) TFT.

A gate insulating layer140is on the first semiconductor layer131and the second semiconductor layer132. The gate insulating layer140may include at least one of tetraethylorthosilicate (TEOS), silicon nitride (SiNx), and silicon oxide (SiO2). The gate insulating layer140may have, for example, a double-layer structure where a SiNxlayer having a predetermined thickness (e.g., about 40 nm) and a TEOS layer having a predetermined thickness (e.g., about 80 nm) are sequentially stacked.

A gate transmission line including gate electrodes152and155is on the gate insulating layer140. The gate transmission line may further includes the gate line151, a first capacitor plate158, and other signal lines. The gate electrodes152and155may overlap at least a portion of or the entirety of the first and second semiconductor layers131and132, for example, a channel area thereof. The gate electrodes152and155may substantially prevent the channel area from being doped with impurities when a source area136and a drain area137of the first and second semiconductor layers131and132are doped with impurities, during the process of forming the first and second semiconductor layers131and132.

The gate electrodes152and155and the first capacitor plate158are on substantially a same layer and may include substantially a same metal material. The gate electrodes152and155and the first capacitor plate158may include at least one of molybdenum (Mo), chromium (Cr), and tungsten (W).

An insulating interlayer160is on the gate insulating layer140to cover the gate electrodes152and155. Similar to the gate insulating layer140, the insulating interlayer160may include or be formed of, for example, silicon nitride (SiNx), silicon oxide (SiOx), or tetraethoxysilane (TEOS).

A data transmission line includes source electrodes173and176and drain electrodes174and177and is on the insulating interlayer160. The data transmission line may include the data line171, the first driving power line172, a second capacitor plate178, and other signal lines. The source electrodes173and176and the drain electrodes174and177are connected to the source area136and the drain area137of the semiconductor layers131and132, respectively, through a contact hole defined at the gate insulating layer140and the insulating interlayer160.

The first switching element Tr1includes the first semiconductor layer131, the first gate electrode152, the first source electrode173, and the first drain electrode174. The second switching element Tr2includes the second semiconductor layer132, the second gate electrode155, the second source electrode176, and the second drain electrode177. The configurations of the first and second switching elements Tr1and Tr2may be different in an other embodiment.

The storage capacitor Cst includes the first capacitor plate158and the second capacitor plate178, with the insulating interlayer160therebetween.

The first switching element Tr1may function as a switching element to select pixels to perform light emission. The first gate electrode152is connected to the gate line151. The first source electrode173is connected to the data line171. The first drain electrode174is spaced apart from the first source electrode173and is connected to the first capacitor plate158.

The second switching element Tr2applies driving power to a pixel electrode211. The driving power allows a light emitting layer212of a light emitting element LED1in the selected pixel to emit light. The second gate electrode155is connected to the first capacitor plate158. Each of the second source electrode176and the second capacitor plate178is connected to the first driving power line172. The second drain electrode177is connected to the pixel electrode211through a contact hole. The pixel electrode211is the anode electrode of the light emitting element LED1.

With the aforementioned structure, the first switching element Tr1is driven by a gate voltage applied to the gate line151and transmits a data voltage applied to the data line171to the second switching element Tr2. The storage capacitor Cst stores a voltage equivalent to the difference between a common voltage applied to the second switching element Tr2from the first driving power line172and the data voltage transmitted from the first switching element Tr1. A current corresponding to the voltage stored in the storage capacitor Cst flows to the light emitting element LED1through the second switching element Tr2cause the light emitting layer212in the light emitting element LED1to emit light.

A planarization layer165covers the data transmission line, e.g., the data line171, the first driving power line172, the source electrodes173and176, the drain electrodes174and177, and the second capacitor plate178, which are patterned using a single mask. The planarization layer165is on the insulating interlayer160.

The planarization layer165serves to substantially eliminate a step difference and planarize a surface therebelow in order to increase luminous efficiency of the light emitting element LED1to be formed thereon. The planarization layer165may include at least one of a polyacrylate resin, an epoxy resin, a phenolic resin, a polyamide resin, a polyimide resin, an unsaturated polyester resin, a polyphenylen ether resin, a polyphenylene sulfide resin, and benzocyclobutene (BCB).

The pixel electrode211is on the planarization layer165and is connected to the drain electrode177through a contact hole defined at the planarization layer165. A portion of or the entirety of the pixel electrode211is at a pixel area500. For example, the pixel electrode211is disposed corresponding to the pixel area500which is defined by a pixel defining layer190. The pixel defining layer190may include, for example, a resin such as a polyacrylate resin and/or a polyimide resin.

A spacer333is on the pixel defining layer190and may include a material which is substantially the same as a material in the pixel defining layer190. The spacer333serves to substantially reduce or minimize a height difference between a layer at a display area of the display panel111and a layer at a non-display area of the display panel111.

The light emitting layer212is on the pixel electrode211in the pixel area500. A common electrode210(or an opposing electrode) is on the pixel defining layer190, the spacer333, and the light emitting layer212.

The light emitting layer212includes an organic material (e.g., a low molecular organic material or a high molecular organic material) or a semiconductor nanocrystal (e.g., a quantum dot or a quantum rod).

At least one of a hole injection layer HIL and a hole transport layer HTL may be between the pixel electrode211and the light emitting layer212. At least one of an electron transport layer ETL and an electron injection layer EIL may further be disposed between the light emitting layer212and the common electrode210.

The pixel electrode211and the common electrode210may be formed as one of a transmissive electrode, a transflective electrode, and a reflective electrode.

A transparent conductive oxide (“TCO”) may be used to form a transmissive electrode. Such a TCO may include at least one of indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc oxide (ZnO), and mixtures thereof.

A metal, e.g., magnesium (Mg), silver (Ag), gold (Au), calcium (Ca), lithium (Li), chromium (Cr), aluminum (Al), and copper (Cu), or an alloy thereof may be used to form a transflective electrode and a reflective electrode. In such an exemplary embodiment, whether an electrode is a transflective type or a reflective type depends on the thickness of the electrode. The transflective electrode may have a thickness, for example, of about 200 nm or less. The reflective electrode may have a thickness, for example, of about 300 nm or more. As the thickness of the transflective electrode decreases, light transmittance and resistance increase. On the contrary, as the thickness of the transflective electrode increases, light transmittance decreases.

The transflective electrode and the reflective electrode may have a multilayer structure which includes a metal layer including a metal or a metal alloy and a TCO layer stacked on the metal layer.

The pixel PX1may have a double-sided emission type structure for emitting a light in a direction of the pixel electrode211and the common electrode210. In such an exemplary embodiment, both the pixel electrode211and the common electrode210may be formed as a transmissive or transflective electrode.

A sealing member250is on the common electrode210and may include a transparent insulating substrate110of, for example, glass or transparent plastic. In addition, the sealing member250may have a thin film encapsulation structure in which one or more inorganic layers and one or more organic layers are alternately stacked. For example, as illustrated inFIG. 5, the sealing member250may include a first inorganic layer250a, an organic layer250bon the first inorganic layer250a, and a second inorganic layer250con the organic layer250b.

In an exemplary embodiment, as illustrated inFIGS. 4 and 5, a capping layer180may also be between the sealing member250and the common electrode210. The capping layer180may substantially prevent damage to the common electrode210below the sealing member250when the sealing member250is deposited. The capping layer180may include an inorganic material.

In an exemplary embodiment, as illustrated inFIG. 3, adjacent pixels PX1, PX2, and PX3are spaced apart from each other by a predetermined distance. For example, when defining three pixels as illustratedFIG. 3as a first pixel PX1, a second pixel PX2, and a third pixel PX3in order from a leftmost one of the three pixels, the distance between a first driving power line172connected to the first pixel PX1and a data line171connected to the second pixel PX2which is adjacent to the first pixel PX1is greater than a distance between a data line171and a first driving power line172which define a location of the first pixel PX1. This is to substantially prevent a material used to form the light emitting element LED1from penetrating into the second pixel PX2when the light emitting element LED1is deposited at the first pixel PX1through a mask deposition process.

The second pixel PX2and the third pixel PX3may have a configuration substantially equal to a configuration of the aforementioned first pixel PX1.

A light emitting element of the first pixel PX1may be defined as a first light emitting element212. A light emitting element of the second pixel PX2may be defined as a second light emitting element222. The light emitting element of the third pixel PX3may be defined as a third light emitting element232.

The first light emitting element212is a red light emitting element that emits red light. The first light emitting element212includes a first anode electrode211(or a first electrode), a first light emitting layer212, and a first cathode electrode213. The first light emitting layer212is between the first anode electrode211and the first cathode electrode213. The first anode electrode211is a pixel electrode of the first pixel PX1.

The first light emitting layer212includes semiconductor nanocrystals (or inorganic semiconductor light emitting materials). The first light emitting layer212generates a light based on an electric current. For example, the semiconductor nanocrystals of the first light emitting layer212are excited by a current to generate a light. The aforementioned current is generated by a voltage of the first anode electrode211and a voltage of the first cathode electrode213. The current passes between the first anode electrode211and the first cathode electrode213. In such an exemplary embodiment, the current is applied to the first light emitting layer212between the first anode electrode211and the first cathode electrode213.

The semiconductor nanocrystals may include nanometer-scale inorganic semiconductor particles. For example, the semiconductor nanocrystals have an average nanocrystalline diameter of less than about 150 [Å], most preferably, in a range from about 12 [Å] to about 150 [Å].

In one embodiment, the semiconductor nanocrystals may include inorganic fine crystals having a diameter for example, in a range from about 1 nm to about 1000 nm, in a range from about 2 nm to about 50 nm, or in a range from about 5 nm to about 20 nm (e.g., about 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm).

Examples of shapes of the semiconductor nanocrystals include a sphere, a rod, a disk, another shape, or combinations thereof. The semiconductor nanocrystals may sometimes be referred to as quantum dots or quantum rods, depending on their shape.

In one embodiment, the semiconductor nanocrystal includes a core including one or more first semiconductor materials, which may be overcoated by one or more second semiconductor materials or may be surrounded by a shell including one or more second semiconductor materials. A structure in which a core of a semiconductor nanocrystal is surrounded by a semiconductor shell may be referred to as a “core/shell” semiconductor nanocrystal.

By controlling the temperature of a reaction mixture during overcoating and monitoring an absorption spectrum of the core, an overcoated material having a high luminous quantum efficiency and narrow size distribution may be obtained. The overcoating may include one or more layers. The overcoating includes one or more kinds of semiconductor materials which are substantially equal to or different from the composition of the core. The overcoat may have a thickness of, for example, about 1 monolayer to about 10 monolayers. In one embodiment, the overcoating may have a thickness of greater than 10 monolayers. In an exemplary embodiment, one or more overcoatings may be on the core.

In an exemplary embodiment, a peripheral shell material may have a band gap greater than a band gap of a core material. In an exemplary embodiment, the peripheral shell material may have a bandgap less than a bandgap of the core material.

In an exemplary embodiment, the shell may have an atomic interval close (e.g. to within a predetermined amount) to that of the core substrate. In an exemplary embodiment, the shell material and the core material may have a substantially identical crystal structure.

Examples of a material of the semiconductor nanocrystals may include, but are not limited to, red (e.g., (CdSe) ZnS), green (e.g., (CdZnSe) CdZnS), and blue (e.g., (CdS) CdZnS). Elements in parentheses correspond to materials of the core. Elements outside the parentheses correspond to materials of the shell. For example, the semiconductor nanocrystal including (CdSe)ZnS includes a core including CdSe and a shell including ZnS.

The semiconductor nanocrystal converts a wavelength of a light to emit a predetermined specific light. The wavelength of light emitted from the first light emitting layer may vary depending on the size of the semiconductor nanocrystal. For example, the color of the light emitted from the first light emitting layer may vary depending on the diameter of the semiconductor nanocrystal.

The semiconductor nanocrystal may have a diameter in a predetermined range, e.g., from about 2 nm to about 10 nm. When the semiconductor nanocrystal has a small diameter (e.g., below a predetermined value), the wavelength of the emitted light is shortened to generate a blueish light. When the size of the semiconductor nanocrystal increases, the wavelength of the emitted light is lengthened to generate a reddish light. For example, a semiconductor nanocrystal having a diameter of about 10 nm may emit red light, a semiconductor nanocrystal having a diameter of about 7 nm may emit green light, and a semiconductor nanocrystal having a diameter of about 5 nm may emit blue light.

Since the first light emitting layer212is a red light emitting layer which emits a red light, the semiconductor nanocrystal of the first light emitting layer212may have a diameter of about 10 nm, for example.

A second light emitting element LED2is a green light emitting element that emits a green light. The second light emitting element LED2includes a second anode electrode221(or a second electrode), a second light emitting layer222, and a second cathode electrode223. The second light emitting layer222is between the second anode electrode221and the second cathode electrode223. The second anode electrode221is a pixel electrode of the second pixel PX2.

The second light emitting layer222may include the aforementioned semiconductor nanocrystals (or an inorganic semiconductor light emitting material). In such an exemplary embodiment, since the second light emitting layer222is a green light emitting layer that emits a green light, the semiconductor nanocrystals of the second light emitting layer222may have a diameter of about 7 nm, for example.

The second light emitting layer222generates a light based on a current. For example, the semiconductor nanocrystals of the second light emitting layer222are excited by a current to generate a light. The aforementioned current is generated by a voltage of the second anode electrode221and a voltage of the second cathode electrode223. The current passes between the second anode electrode221and the second cathode electrode223. In such an exemplary embodiment, the current is applied to the second light emitting layer222between the second anode electrode221and the second cathode electrode223.

A third light emitting element LED3is a blue light emitting element that emits a blue light. The third light emitting element LED3includes a third anode electrode231(or a third electrode), a third light emitting layer232, and a third cathode electrode233. The third light emitting layer232is between the third anode electrode231and the third cathode electrode233. The third anode electrode231is a pixel electrode of the third pixel PX3.

The third light emitting layer232includes an organic material (or an organic light emitting material). For example, the third light emitting layer232may include a red light emitting material such as tetraphenyl naphthacene (rubrene), tris(1-phenylisoquinoline)iridium(III) (Ir(piq)3), bis(2-benzo[b]thiophen-2-yl-pyridine) (acetylacetonate)iridium(III) (Ir(btp)2(acac)), tris(dibenzoylmethane)phenanthroline europium III (Eu(dbm)3(phen)), tris[4,4′-di-tert-butyl-(2,2′)-bipyridine] ruthenium (III) complex (Ru(dtbbpy)3*2 (PF6)), DCM1, DCM2, Eu(thenoyltrifluoroacetone)3, and butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), and may further include a polymer light emitting material such as a polyfluorene-based polymer and a polyvinyl-based polymer. In addition, the third light emitting layer232may include an anthracene-based material.

The third light emitting layer232generates light based on a current. For example, an organic material of the third light emitting layer232is excited by a current to generate a light. The aforementioned current is generated by a voltage of the third anode electrode231and a voltage of the third cathode electrode233. The current passes between the third anode electrode231and the third cathode electrode233. In such an exemplary embodiment, the current is applied to the third light emitting layer232between the third anode electrode231and the third cathode electrode233.

The first cathode electrode213, the second cathode electrode223, and the third cathode electrode233described above are parts of the aforementioned common electrode210. For example, the first cathode electrode213, the second cathode electrode223, and the third cathode electrode233are formed unitarily, and the unitary structure is the common electrode210.

FIG. 6illustrates a cross-sectional embodiment of the first pixel, the second pixel, and the third pixel ofFIG. 5. The light emitting display devices may further include a hole transport layer601, a hole injection layer602, an electron transport layer611, and/or an electron injection layer612.

The hole transport layer601is between the first anode electrode211and the first light emitting layer212, between the second anode electrode221and the second light emitting layer222, and between the third anode electrode231and the third light emitting layer232. The hole transport layer601improves the properties of the holes provided through the hole injection layer602to move to the light emitting layer. The hole transport layer601may include, for example, N,N-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPC), or N,N′-di(naphthalene-1-yl)-N,N′-diphenyl benzidine (α-NPD).

In an exemplary embodiment, the hole transport layer601may include a first hole transport layer, a second hole transport layer, and a third hole transport layer which are separated from each other. In such an exemplary embodiment, the first hole transport layer is between the first anode electrode211and the first light emitting layer212. The second hole transport layer is between the second anode electrode221and the second light emitting layer222. The third hole transport layer is between the third anode electrode231and the third light emitting layer232.

The hole injection layer602is between the hole transport layer601and the first anode electrode211, between the hole transport layer601and the second anode electrode221, and between the hole transport layer601and the third anode electrode231.

The hole injection layer602allows the holes from the first anode electrode211, the second anode electrode221, and the third anode electrode231to move more efficiently, thereby improving the electrical properties of the first, second, and third light emitting elements LED1, LED2, and LED3. The hole injection layer602may include, for example, a phthalocyanine compound such as copper phthalocyanine, a starburst-type amine such as TCTA, m-MTDATA, or m-MTDAPB.

In an exemplary embodiment, the hole injection layer602may include a first hole injection layer, a second hole injection layer, and a third hole injection layer which are separated from each other. In such an exemplary embodiment, the first hole injection layer is between the first anode electrode211and the first hole transport layer, the second hole injection layer is between the second anode electrode221and the second hole transport layer, and the third hole injection layer is between the third anode electrode231and the third hole transport layer.

The electron transport layer611is between the first light emitting layer212and the cathode electrode, between the second light emitting layer222and the cathode electrode, and between the third light emitting layer232and the cathode electrode.

The electron transport layer611allows electrons from the electron injection layer612to move easily to the first, second, and third light emitting layers. The electron transport layer611may include Alq3.

In an exemplary embodiment, the electron transport layer611may include a first electron transport layer, a second electron transport layer, and a third electron transport layer which are separated from each other. In such an exemplary embodiment, the first electron transport layer is between the first light emitting layer212and the first cathode electrode213(or the common electrode210), the second electron transport layer is between the second light emitting layer222and the second cathode electrode223(or the common electrode210), and the third electron transport layer is between the third light emitting layer232and the third cathode electrode233(or the common electrode210).

The electron injection layer612is between the electron transport layer611and the common electrode210. The electron injection layer612is on the electron transport layer611and, for example, may include PBD, PF-6P, PyPySPyPy, LiF, NaCl, CaF, Li2O, BaO, or Liq. The electron injection layer612attracts electrons from the common electrode210so that electrons may be more easily provided to the electron transport layer611.

In an exemplary embodiment, the electron injection layer612may include a first electron injection layer, a second electron injection layer, and a third electron injection layer which are separated from each other. In such an exemplary embodiment, the first electron injection layer is between the first cathode electrode213(or the common electrode210) and the first electron transport layer, the second electron injection layer is between the second cathode electrode223(or the common electrode210) and the second electron transport layer, and the third electron injection layer is between the third cathode electrode233(or the common electrode210) and the third electron transport layer.

The first light emitting layer212generates a light based on electrons from the electron transport layer611and holes from the hole transport layer601. For example, the semiconductor nanocrystals of the first light emitting layer212combine electrons from the electron transport layer611and holes from the hole transport layer601to generate light.

The second light emitting layer222generates a light based on electrons from the electron transport layer611and holes from the hole transport layer601. For example, the semiconductor nanocrystals of the second light emitting layer222combine electrons from the electron transport layer611and holes from the hole transport layer601to generate light.

The third light emitting layer232generates a light based on electrons from the electron transport layer611and holes from the hole transport layer601. For example, the organic material of the third light emitting layer232combines electrons from the electron transport layer611and holes from the hole transport layer601to generate light.

The first light emitting layer212may be manufactured, for example, by a solution process. In one embodiment, a solvent including a plurality of semiconductor nanocrystals is coated on the hole transport layer601through a solution process. Subsequently, when the solvent is volatilized, the first light emitting layer212including the plurality of semiconductor crystals is manufactured. The second light emitting layer222may also be manufactured by the solution process described above. In the solution process, the solution may be ejected by an inkjet method.

In accordance with one or more of the aforementioned embodiments, a light emitting display device may provide the following effects. A light emitting layer including semiconductor nanocrystals has excellent color reproducibility compared to a light emitting layer including organic materials. In addition, the light emitting layer including semiconductor nanocrystals may be driven at a voltage lower than a voltage at which a light emitting layer including organic materials is driven.

In an exemplary embodiment, a red light emitting layer and a green light emitting layer exhibit excellent luminous efficiency and excellent external quantum efficiency (EQE) when they include semiconductor nanocrystals.

A blue light emitting layer may be difficult to be manufactured with semiconductor nanocrystals due to its characteristics. When the blue light emitting layer includes semiconductor nanocrystals, light emitted from the blue light emitting layer has a wide half width and a central wavelength shifted to green rather than blue. Accordingly, when a blue light emitting layer includes semiconductor nanocrystals, it may be difficult to be used as a blue light emitting element.

According to the light emitting display device according to an exemplary embodiment, each of a red pixel and a green pixel includes a light emitting layer including semiconductor nanocrystals (quantum dots or quantum rods), and a blue pixel includes a light emitting layer including an organic material. Accordingly, the image quality of the light emitting display device may be improved.