Patent Publication Number: US-2021184146-A1

Title: Inorganic light emitting diode and inorganic light emitting device including the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 10-2019-0168691, filed in the Republic of Korea on Dec. 17, 2019 and No. 10-2020-0119844, filed in the Republic of Korea on Sep. 17, 2020, the entire contents of all these applications are incorporated herein by reference in its entirety into the present application. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a light emitting diode, and more specifically, to an inorganic light emitting diode enhances its stability and luminous efficiency and an inorganic light emitting device including the diode. 
     Discussion of the Related Art 
     As electronic and information technologies progress rapidly, a field of displays for processing and displaying a large quantity of information has been developed rapidly. Accordingly, various flat panel display devices have been widely used. Among the flat panel display devices, an organic light emitting diode (OLED) has come into spotlight. Since the OLED can be formed even on a flexible transparent substrate and has relatively lower power consumption, the OLED display device has attracted a lot of attention as a next-generation display device replacing LCD. However, in case of increasing current densities or raising driving voltages in the OLED for improving luminance in OLED display device, the luminous lifetime of the OLED become shorter owing to thermal degradation and deteriorations of organic materials in the OLED. 
     Recently, a display device using inorganic luminescent particles such as quantum dot (QD) or quantum rod (QR) has been developed. QD or QR is an inorganic luminescent particle that emits light as unstable stated excitons shift from its conduction band to its valance band. QD or QR has large extinction coefficient, high quantum yield among inorganic particles and generates strong fluorescence. Besides, since QD or QR has different luminescence wavelengths as its sizes, it is possible to obtain light within the whole visible light spectra so as to implement various colors by adjusting sizes of QD or QR. 
     When the inorganic luminescent particles such as QD are produced or are introduced into a light emitting diode, the inorganic luminescent particles are exposed to external environment as organic ligands bound to the surface of the particles are detached or separated from the particles. As the inorganic luminescent particles, which is very vulnerable to external environment such as moisture or oxygen, was exposed to external environments, the luminous efficiency of the particles is deteriorated. In addition, as voids are formed in an emitting material layer consisting of the inorganic luminescent particles and surface defects such as vacancy on a surface of the inorganic luminescent particles are caused, an exciton generation efficiency of the inorganic luminescent particles are deteriorate. 
     SUMMARY 
     Accordingly, embodiments of the present disclosure are directed to an inorganic light emitting diode and an inorganic light emitting device having the diode that substantially obviates one or more of the problems due to the limitations and disadvantages of the related art. 
     An object of the present disclosure is to provide an inorganic light emitting diode that minimizes surface defects on inorganic luminescent particles or voids to improve a stability of the inorganic luminescent particles and an inorganic light emitting device including the diode. 
     Another object of the present disclosure is to provide an inorganic light emitting diode that reduces its driving voltage and improves its luminous efficiency and an inorganic light emitting device including the diode. 
     Additional features and aspects will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the inventive concepts provided herein. Other features and aspects of the inventive concept can be realized and attained by the structure particularly pointed out in the written description, or derivable therefrom, and the claims hereof as well as the appended drawings. 
     To achieve these and other aspects of the inventive concept, as embodied and broadly described, the present disclosure provides an inorganic light emitting diode, comprises a first electrode; a second electrode facing the first electrode; and an emitting material layer disposed between the first and second electrodes, wherein the emitting material layer comprises an inorganic luminescent particle dispersed in a siloxane matrix, and wherein the siloxane matrix has a thickness equal to or less than a thickness of a layer of the inorganic luminescent particle. 
     As an example, the siloxane matrix can have the thickness of at least equal to or more than about a tenth, preferably about a fourth, and more preferably about a third of the thickness of the layer of the inorganic luminescent particle. 
     In one exemplary aspect, the inorganic luminescent particle and the siloxane matrix in the emitting material layer can be mixed with a volume ratio between about 1:0.01 and about 1:4, preferably between about 1:0.05 and about 1:2. 
     The siloxane matrix can comprise an orthosilicate moiety. For example, the orthosilicate moiety can comprise a tetramethyl orthosilicate moiety, a tetraethyl orthosilicate moiety, a tetrapropyl orthosilicate, a tetrabutyl orthosilicate and a tetrakis(2-ethylhexyl) orthosilicate moiety. 
     In another exemplary aspect, the siloxane matrix can comprise a silsesquionxne. 
     The inorganic luminescent particle can include at least one of a quantum dot (QD) and a quantum rod (QR). 
     In another aspect, the present disclosure an inorganic light emitting device that comprises a substrate and the inorganic light emitting diode over the substrate, as described above. 
     It is to be understood that both the foregoing general description and the following detailed description are examples and are explanatory and are intended to provide further explanation of the inventive concepts as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the disclosure, are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain principles of the disclosure. 
         FIG. 1  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with an exemplary aspect of the present disclosure; 
         FIG. 2  is a schematic cross-sectional view illustrating an inorganic light emitting diode (LED) in accordance with one exemplary aspect of the present disclosure. 
         FIG. 3  is a schematic diagram illustrating inorganic luminescent particles dispersed in a siloxane matrix in an emitting material layer of the inorganic LED in accordance with the present disclosure. 
         FIG. 4  is a schematic cross-sectional view illustrating an inorganic light emitting diode (LED) in accordance with another exemplary aspect of the present disclosure. 
         FIG. 5  is a schematic cross-sectional view illustrating an inorganic light emitting diode (LED) in accordance with still another exemplary aspect of the present disclosure. 
         FIG. 6  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with another exemplary aspect of the present disclosure. 
         FIG. 7  is a schematic cross-section view illustrating an inorganic light emitting diode (LED) in accordance with still another exemplary aspect of the present disclosure. 
         FIG. 8  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with still another exemplary aspect of the present disclosure. 
         FIG. 9  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with another exemplary aspect of the present disclosure. 
         FIG. 10  is a schematic cross-section view illustrating an inorganic light emitting diode (LED) in accordance with still another exemplary aspect of the present disclosure. 
         FIG. 11  is a TEM image illustrating a cross-section of an inorganic LED fabricated in accordance with an Example of the present disclosure. 
         FIGS. 12A and 12B  are TEM images illustrating a top or a cross-sectional of an inorganic LED fabricated in a Comparative Example. 
         FIGS. 13A to 13C  illustrate measurement results by STEM-EDS for the inorganic LED fabricated in accordance with an Example of the present disclosure, where  FIG. 13A  illustrates a line-profile of the inorganic LED,  FIG. 13B  is a graph illustrating atomic % of zinc, which is one element of a quantum dot, by STEM-EDS, and  FIG. 13C  is a graph illustrating atomic % of silicon, which is one element of a siloxane matrix, by STEM-EDS. 
         FIGS. 14A to 14C  illustrate measurement results by STEM-EDS for the inorganic LED fabricated in accordance with another Example of the present disclosure, where  FIG. 14A  illustrates a line-profile of the inorganic LED,  FIG. 14B  is a graph illustrating atomic % of zinc, which is one element of a quantum dot, by STEM-EDS, and  FIG. 14C  is a graph illustrating atomic % of silicon, which is one element of a siloxane matrix, by STEM-EDS. 
         FIGS. 15A to 15C  illustrate measurement results by STEM-EDS for the inorganic LED fabricated in the Comparative Example, where  FIG. 15A  illustrates a line-profile of the inorganic LED,  FIG. 15B  is a graph illustrating atomic % of zinc, which is one element of a quantum dot, by STEM-EDS, and  FIG. 15C  is a graph illustrating atomic % of silicon, which is one element of a siloxane matrix, by STEM-EDS. 
         FIG. 16  is a graph illustrating measurement results of leakage current by voltage (V)—current density in LEDs fabricated in accordance with Examples of the present disclosure. 
         FIG. 17  is a graph illustrating measurement results of voltage (V)—external quantum efficiency (EQE) in LEDs fabricated in accordance with Examples of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to aspects of the disclosure, examples of which are illustrated in the accompanying drawing. 
     [Inorganic Light Emitting Device and Inorganic LED] 
     The present disclosure relates to an inorganic light emitting diode (LED) in which an EML includes inorganic luminescent particles dispersed in a siloxane matrix of which thickness are designed to be equal to or less than a thickness of a layer of an inorganic luminescent layer, thus the inorganic LED lowers its driving voltage and improves its luminous efficiency, and an inorganic light emitting device including the inorganic LED. The inorganic LED can be applied to an inorganic light emitting device such as an inorganic light emitting display device and an inorganic light emitting illumination device.  FIG. 1  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with an exemplary aspect of the present disclosure. All the components of the inorganic light emitting display/illumination device according to all embodiments of the present disclosure are operatively coupled and configured. 
     As illustrated in  FIG. 1 , an inorganic light emitting display device  100  includes a substrate  110 , a thin film transistor Tr over the substrate  110  and an inorganic light emitting diode (LED) D connected to the thin film transistor Tr. 
     The substrate  112  can include, but is not limited to, glass, thin flexible material and/or polymer plastics. For example, the flexible material can be selected from the group, but is not limited to, polyimide (PI), polyethersulfone (PES), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate (PC) and combination thereof. The substrate  110 , over which the thin film transistor Tr and the inorganic LED D are arranged, form an array substrate. 
     A buffer layer  122  can be disposed over the substrate  110 , and the thin film transistor Tr is disposed over the buffer layer  122 . The buffer layer  122  can be omitted. 
     A semiconductor layer  120  is disposed over the buffer layer  122 . In one exemplary aspect, the semiconductor layer  120  can include, but is not limited to, oxide semiconductor materials. In this case, a light-shied pattern can be disposed under the semiconductor layer  120 , and the light-shield pattern can prevent light from being incident toward the semiconductor layer  120 , and thereby preventing the semiconductor layer  120  from being deteriorated by the light. Alternatively, the semiconductor layer  120  can include polycrystalline silicon. In this case, opposite edges of the semiconductor layer  120  can be doped with impurities. 
     A gate insulating layer  124  made of an insulating material is disposed on the semiconductor layer  120 . The gate insulating layer  124  can include, but is not limited to, an inorganic insulating material such as silicon oxide (SiO x ) or silicon nitride (SiN x ). 
     A gate electrode  130  made of a conductive material such as a metal is disposed over the gate insulating layer  124  so as to correspond to a center of the semiconductor layer  120 . While the gate insulating layer  124  is disposed over a whole area of the substrate  110  in  FIG. 1 , the gate insulating layer  124  can be patterned identically as the gate electrode  130 . 
     An interlayer insulating layer  132  made of an insulating material is disposed on the gate electrode  130  with covering over an entire surface of the substrate  110 . The interlayer insulating layer  132  can include, but is not limited to, an inorganic insulating material such as silicon oxide (SiO x ) or silicon nitride (SiN x ), or an organic insulating material such as benzocyclobutene or photo-acryl. 
     The interlayer insulating layer  132  has first and second semiconductor layer contact holes  134  and  136  that expose both sides of the semiconductor layer  120 . The first and second semiconductor layer contact holes  134  and  136  are disposed over both sides of the gate electrode  130  with spacing apart from the gate electrode  130 . The first and second semiconductor layer contact holes  134  and  136  are formed within the gate insulating layer  124  in  FIG. 1 . Alternatively, the first and second semiconductor layer contact holes  134  and  136  are formed only within the interlayer insulating layer  132  when the gate insulating layer  124  is patterned identically as the gate electrode  130 . 
     A source electrode  144  and a drain electrode  146 , each of which includes a conductive material such as a metal, are disposed on the interlayer insulating layer  132 . The source electrode  144  and the drain electrode  146  are spaced apart from each other with respect to the gate electrode  130 , and contact both sides of the semiconductor layer  120  through the first and second semiconductor layer contact holes  134  and  136 , respectively. 
     The semiconductor layer  120 , the gate electrode  130 , the source electrode  144  and the drain electrode  146  constitute the thin film transistor Tr, which acts as a driving element. The thin film transistor Tr in  FIG. 1  has a coplanar structure in which the gate electrode  130 , the source electrode  144  and the drain electrode  146  are disposed over the semiconductor layer  120 . Alternatively, the thin film transistor Tr can have an inverted staggered structure in which a gate electrode is disposed under a semiconductor layer and source and drain electrodes are disposed over the semiconductor layer. In this case, the semiconductor layer can include, but is not limited to, amorphous silicon. 
     Agate line and a data line, which cross each other to define a pixel region, and a switching element, which is connected to the gate line and the data line, can be further formed in the pixel region. The switching element is connected to the thin film transistor Tr, which is a driving element. In addition, a power line is spaced apart in parallel from the gate line or the data line, and the thin film transistor Tr can further includes a storage capacitor configured to constantly keep a voltage of the gate electrode for one frame. 
     Moreover, the inorganic light emitting display device  100  can include a color filter layer that comprises dyes or pigments for transmitting specific wavelength light of light emitted from the inorganic LED D. For example, the color filter layer can transmit light of specific wavelength such as red (R), green (G), blue (B) and/or white (W). Each of red, green, and blue color filter layers can be formed separately in each pixel region. In this case, the inorganic light emitting display device  100  can implement full-color through the color filter. 
     For example, when the inorganic light emitting display device  100  is a bottom-emission type, the color filter layer can be disposed on the interlayer insulating layer  132  with corresponding to the inorganic LED D. Alternatively, when the inorganic light emitting display device  100  is a top-emission type, the color filter layer can be disposed over the inorganic LED D, that is, a second electrode  230 . 
     In addition, the inorganic light emitting display device  100  can further comprise a color conversion layer which transforms specific wavelength light among the light emitted from the inorganic LED D. The color conversion layer can comprise an inorganic luminescent material such as a quantum dot and/or a quantum rod. For example, the color conversion layer can be disposed over the inorganic LED D or under the inorganic LED D. 
     A passivation layer  150  is disposed on the source and drain electrodes  144  and  146  over the whole substrate  110 . The passivation layer  150  has a flat top surface and a drain contact hole  152  that exposes the drain electrode  146  of the thin film transistor Tr. While the drain contact hole  152  is disposed on the second semiconductor layer contact hole  136 , it can be spaced apart from the second semiconductor layer contact hole  136 . 
     The inorganic LED D includes a first electrode  210  that is disposed on the passivation layer  150  and connected to the drain electrode  146  of the thin film transistor Tr. The inorganic LED D further includes an emissive layer  220  and a second electrode  230  each of which is disposed sequentially on the first electrode  210 . 
     The first electrode  210  is disposed in each pixel region. The first electrode  210  can be an anode and include a conductive material having relatively high work function value. For example, the first electrode  210  can include, but is not limited to, a doped or undoped metal oxide such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), indium-tin-zinc oxide (ITZO), indium-copper-oxide (ICO), tin oxide (SnO 2 ), indium oxide (In 2 O 3 ), cadmium:zinc oxide (Cd:ZnO), fluorine:tin oxide (F:SnO 2 ), indium:tin oxide (In: SnO 2 ), gallium:tin oxide (Ga:SnO 2 ) or aluminum:zinc oxide (Al:ZnO; AZO). Optionally, the first electrode  210  can include a metal or nonmetal material such as nickel (Ni), platinum (Pt), gold (Au), silver (Ag), iridium (Ir) or a carbon nanotube (CNT), other than the above-described metal oxide. 
     In one exemplary aspect, when the inorganic light emitting display device  100  is a bottom-emission type, the first electrode  210  can have a single-layered structure of transparent conductive oxide. Alternatively, when the inorganic light emitting display device  100  is a top-emission type, a reflective electrode or a reflective layer can be disposed under the first electrode  210 . For example, the reflective electrode or the reflective layer can comprise, but is not limited to, silver (Ag) or aluminum-palladium-copper (APC) alloy. In the inorganic LED D of a top-emission type, the first electrode  210  can have a triple-layered structure of ITO/Ag/ITO or ITO/APC/ITO. 
     In addition, a bank layer  160  is disposed on the passivation layer  150  in order to cover edges of the first electrode  210 . The bank layer  160  exposes a center of the first electrode  210 . 
     An emissive layer  220  is disposed on the first electrode  210 . In one exemplary aspect, the emissive layer  220  can have a single-layered structure of an emitting material layer (EML)  240  (see,  FIG. 2 ). Alternatively, the emissive layer  220  can have a multiple-layered structure of an EML  240 , a first charge transfer layer  250 , a second charge transfer layer  270 , a CCL  260 , and optionally at least one of an electron blocking layer (EBL)  265  and a hole blocking layer (HBL)  275  (see,  FIGS. 2, 4 and 5 ). In one exemplary aspect, the emissive layer  220  can have one emitting part. Alternatively, the emissive layer  220  can have multiple emitting parts to form a tandem structure. 
     The second electrode  230  is disposed over the substrate  110  above which the emissive layer  220  is disposed. The second electrode  230  can be disposed over a whole display area, can include a conductive material having a relatively low work function value compared to the first electrode  210 , and can be a cathode. For example, the second electrode  230  can include, but is not limited to, Ca, Ba, Ca/Al, LiF/Ca, LiF/Al, BaF 2 /Al, CsF/Al, CaCO 3 /Al, BaF 2 /Ca/Al, Al, Mg, Au:Mg or Ag:Mg. When the inorganic light emitting display device  100  is a top-emission type, the second electrode  230  is thin so as to have light-transmissive (semi-transmissive) property. 
     In addition, an encapsulation film  170  can be disposed over the second electrode  220  in order to prevent outer moisture from penetrating into the inorganic LED D. The encapsulation film  170  can have, but is not limited to, a laminated structure of a first inorganic insulating film  172 , an organic insulating film  174  and a second inorganic insulating film  176 . 
     Moreover, can the inorganic light emitting display device  100  can have a polarizer in order to decrease external light reflection. For example, the polarizer can be a circular polarizer. When the organic light emitting display device  100  is a bottom-emission type, the polarizer can be disposed under the substrate  100 . Alternatively, when the organic light emitting display device  100  is a top-emission type, the polarizer can be disposed over the encapsulation film  170 . In addition, a cover window can be attached to the encapsulation film  170  or the polarizer. In this case, the substrate  110  and the cover window can have a flexible property, thus the light emitting display device  100  can be a flexible display device. 
       FIG. 2  is a cross-sectional view illustrating an inorganic light emitting diode (LED) in accordance with one exemplary aspect of the present disclosure. As illustrated in  FIG. 2 , the inorganic LED D1 comprises a first electrode  210 , a second electrode  230  facing the first electrode  210  and an emissive layer  220  disposed between the first and second electrodes  210  and  230 . The inorganic light emitting display device  100  ( FIG. 1 ) can include a red pixel region, a green pixel region and a blue pixel region, and the inorganic LED D1 can be disposed in any pixel region of the red, green and blue pixel regions. The emissive layer  220  having single emitting part comprises an EML  240  disposed between the first and second electrodes  210  and  230 . Also, the emissive layer  220  can at least one of a first charge transfer layer (CTL1)  250  disposed between the first electrode and the EML  240 , a second charge transfer layer (CTL2)  270  disposed between the EML  240 . 
     In this aspect, the first electrode  210  can be an anode such as a hole injection electrode. The first electrode  210  can be located over a substrate  110  (see,  FIG. 1 ) that can be a glass or a polymer. As an example, the first electrode  210  can include, but is not limited to, a doped or undoped metal oxide such as ITO, IZO, ITZO, ICO, SnO 2 , In 2 O 3 , Cd:ZnO, F:SnO 2 , In: SnO 2 , Ga:SnO 2  and AZO. Optionally, the first electrode  210  can include a metal or nonmetal material such as Ni, Pt, Au, Ag, Ir and CNT, other than the above-described metal oxide. 
     The second electrode  230  can be a cathode such as an electron injection electrode. As an example, the second electrode  230  can include, but is not limited to, Ca, Ba, Ca/Al, LiF/Ca, LiF/Al, BaF 2 /Al, CsF/Al, CaCO 3 /Al, BaF 2 /Ca/Al, Al, Mg, Au:Mg or Ag:Mg. As an example, each of the first electrode  210  and the second electrode  230  can have a thickness of, but is not limited to, about 5 to about 300 nm, preferably about 10 nm to about 200 nm. 
     In one exemplary aspect, when the inorganic LED D1 is a bottom emission-type LED, the first electrode  210  can include, but is not limited to, a transparent conductive metal oxide such as ITO, IZO, ITZO or AZO, and the second electrode  230  can include, but is not limited to, Ca, Ba, Ca/Al, LiF/Ca, LiF/Al, BaF 2 /Al, Al, Mg, or an Ag:Mg alloy. 
     The EML  240  can include inorganic luminescent particles  300  (see,  FIG. 3 ) and a siloxane matrix  400  in which the inorganic luminescent particles  300  are dispersed. As an example, the inorganic luminescent particles  300  can include quantum dots (QDs) or quantum rods (QRs). QDs or QRs are inorganic luminescent particles each of which emits light as unstable charge excitons shifts from the conduction band energy level to the valance band (VB) energy level. These inorganic luminescent particles  300  have very large extinction coefficient, high quantum yield among inorganic particles and generates strong fluorescence. In addition, these inorganic luminescent particles  300  emit at different luminescence wavelengths as its size, and it is possible to emit lights within the whole visible light spectra so as to implement various colors by adjusting sizes of these inorganic luminescent particles  300 . When these inorganic luminescent particles  300  such as QDs and/or QRs are used as a luminescence material in the EML  240 , it is possible to enhance color purity in individual pixel region and to realize White (W) light consisting of red (R), green (G) and blue (B) light having high color purity. 
     In one exemplary aspect, the inorganic luminescent particles  300  (e.g., QDs or QRs) can have a single-layered structure. In another exemplary aspect, the inorganic luminescent particles  300  (e.g., QDs or QRs) can have a multiple-layered heterologous structure, i.e. core  310 /shell  320  structures, and can further comprise plural ligands  330  bound to a surface of the shell  320  (see,  FIG. 3 ). Each of the core  310  and the shell  320  can have a single layer or multiple layers, respectively. The reactivity of precursors forming the core  310  and/or shell  320 , injection rates of the precursors into a reaction vessel, reaction temperature and kinds of ligands  330  bonded to the outer surface of those inorganic luminescent particles  300  such as QDs or QRs can have affects upon the growth degrees, crystal structures of those inorganic luminescent particles  300 . As a result, it is possible to emit lights of various luminescent wavelength ranges, as the energy level bandgap of those inorganic luminescent particles  300  are adjusted. 
     In one exemplary aspect, the inorganic luminescent particles  300  (e.g., QDs and/or QRs) can have a type I core/shell structure where an energy level bandgap of the core  310  is within an energy level bandgap of the shell  320 . In case of using the type I core/shell structure, electrons and holes are transferred to the core  310  and recombined in the core  310 . Since the core  310  emits light from exciton energies, it is possible to adjust luminance wavelengths by adjusting sizes of the core  310 . 
     In another exemplary aspect, the inorganic luminescent particles  300  (e.g., QDs and/or QRs) can have type II core/shell structure where the energy level bandgap of the core  310  and the shell  320  are staggered and electrons and holes are transferred to opposite directions among the core  310  and the shell  320 . In case of using the type II core/shell structure, it is possible to adjust luminescence wavelengths as the thickness and the energy bandgap locations of the shell  320 . 
     In still another exemplary aspect, the inorganic luminescent particles  300  (e.g., QDs and/or QRs) can have reverse type I core/shell structure where the energy level bandgap of the core  310  is wider than the energy level bandgap of the shell  320 . In case of using the reverse type I core/shell structure, it is possible to adjust luminescence wavelengths as thickness of the shell  320 . 
     As an example, when the inorganic luminescent particle  300  (e.g., QDs and/or QRs) has a type-I core/shell structure, the core  310  is a region where luminescence substantially occurs, and a luminescence wavelength of the inorganic luminescent particle  300  is determined as the sizes of the core  310 . To achieve a quantum confinement effect, the core  310  necessarily has a smaller size than the exciton Bohr radius according to material of the inorganic luminescent particle  300 , and an optical bandgap at a corresponding size. 
     The shell  320  of the inorganic luminescent particles  300  (e.g., QDs and/or QRs) promotes the quantum confinement effect of the core  310 , and determines the stability of the particles  300 . Atoms exposed on a surface of colloidal inorganic luminescent particles  300  (e.g., QDs and/or QRs) having only a single structure have lone pair electrons which do not participate in a chemical bond, unlike the internal atoms. Since energy levels of these surface atoms are between the conduction band edge and the valance band edge of the inorganic luminescent particles  300  (e.g., QDs and/or QRs), the charges can be trapped on the surface of the inorganic luminescent particles  300  (e.g., QDs and/or QRs), and thereby resulting in surface defects. Due to a non-radiative recombination process of excitons caused by the surface defects, the luminous efficiency of the inorganic luminescent particles  300  can be degraded, and the trapped charges can react with external oxygen and compounds, leading to a change in the chemical composition of the inorganic luminescent particles  300 , or to a permanent loss of the electrical/optical properties of the inorganic luminescent particles  300 . 
     To effectively form the shell on the surface of the core  310 , a lattice constant of the material in the shell  320  needs to be similar to that of the material in the core  310 . As the surface of the core  310  is enclosed by the shell  320 , the oxidation of the core  310  can be prevented, the chemical stability of the inorganic luminescent particles  300  (e.g., QDs and/or QRs) can be enhanced, and the photo-degradation of the core  310  by an external factor such as water or oxygen can be prevented. In addition, the loss of excitons caused by the surface trap on the surface of the core  310  can be minimized, and the energy loss caused by molecular vibration can be prevented, thereby enhancing the quantum efficiency. 
     In one exemplary aspect, each of the core  310  and the shell  320  can include, but is not limited to, a semiconductor nanocrystal and/or metal oxide nanocrystal having quantum confinement effect. For example, the semiconductor nanocrystal of the core  310  and the shell  320  can be selected from the group, but is not limited to, consisting of Group II-VI compound semiconductor nanocrystal, Group III-V compound semiconductor nanocrystal, Group IV-VI compound semiconductor nanocrystal, Group compound semiconductor nanocrystal and combination thereof. 
     Particularly, Group II-VI compound semiconductor nanocrystal of the core  310  and/or the shell  320  can be selected from the group, but is not limited to, consisting of MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeSe, ZnO, CdS, CdSe, CdTe, CdSeS, CdZnS, CdSeTe, CdO, HgS, HgSe, HgTe, CdZnTe, HgCdTe, HgZnSe, HgZnTe, CdS/ZnS, CdS/ZnSe, CdSe/ZnS, CdSe/ZnSe, ZnSe/ZnS, ZnS/CdSZnS, CdS/CdZnS/ZnS, ZnS/ZnSe/CdSe and combination thereof. Group III-V compound semiconductor nanocrystal of the core and/or shell can be selected from the group, but is not limited to, consisting of AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AlGaAs, InGaAs, InGaP, AlInAs, AlInSb, GaAsN, GaAsP, GaAsSb, AlGaN, AlGaP, InGaN, InAsSb, InGaSb, AlGaInP, AlGaAsP, InGaAsP, InGaAsSb, InAsSbP, AlInAsP, AlGaAsN, InGaAsN, InAlAsN, GaAsSbN, GaInNAsSb and combination thereof. 
     Group IV-VI compound semiconductor nanocrystal of the core  310  and/or shell  320  can be selected from the group, but is not limited to, consisting of TiO 2 , SnO 2 , SnS, SnS 2 , SnTe, PbO, PbO 2 , PbS, PbSe, PbTe, PbSnTe and combination thereof. Also, Group compound semiconductor nanocrystal of the core  310  and/or shell  320  can be selected from the group, but is not limited to, AgGaS 2 , AgGaSe 2 , AgGaTe 2 , AgInS 2 , CuInS 2 , CuInSe 2 , Cu 2 SnS 3 , CuGaS 2 , CuGaSe 2  and combination thereof. Alternatively, each of the core  310  and the shell  320  can independently include multiple layers each of which has different Groups compound semiconductor nanocrystal, e.g., Group II-VI compound semiconductor nanocrystal and Group III-V compound semiconductor nanocrystal such as InP/ZnS, InP/ZnSe, GaP/ZnS, and the likes, respectively. 
     In another aspect, the metal oxide nanocrystal of the core  310  and/or shell  320  can include, but is not limited to, Group II or Group III metal oxide nanocrystal. As an example, the metal oxide nanocrystal of the core  310  and/or the shell  320  can be selected from the group, but is not limited to, MgO, CaO, SrO, BaO, Al 2 O 3  and combination thereof. 
     The semiconductor nanocrystal of the core  310  and/or the shell  320  can be doped with a rare earth element such as Eu, Er, Tb, Tm, Dy or an arbitrary combination thereof or can be doped with a metal element such as Mn, Cu, Ag, Al or an arbitrary combination thereof. 
     As an example, the core  310  in QDs or QRs  300  can include, but is not limited to, ZnSe, ZnTe, CdSe, CdTe, InP, ZnCdS, CuxIn1-xS, Cuxlnl-xSe, AgxIn1-xS and combination thereof. The shell  320  in QDs or QRs  300  can include, but is not limited to, ZnS, GaP, CdS, ZnSe, CdS/ZnS, ZnSe/ZnS, ZnS/ZnSe/CdSe, GaP/ZnS, CdS/CdZnS/ZnS, ZnS/CdSZnS, CdXZn1-xS and combination thereof. 
     In another exemplary aspect, the inorganic luminescent particle  300  can include, but is not limited to, alloy QD or alloy QR such as homogenous alloy QD or QR or gradient alloy QD or QR, e.g., CdSxSe1-x, CdSexTe1-x, CdXZn1-xS, ZnxCd1-xSe, CuxIn1-xS, CuxIn1-xSe, AgxIn1-xS. 
     In another exemplary aspect, the inorganic luminescent particle  300  can be QDs or QRs having a Perovskite structure. The inorganic luminescent particle such as The QDs or QRs of the Perovskite structure comprises a core as a luminescent component and optionally a shell. As an example, the core  310  of the inorganic luminescent particle  300  having the Perovskite structure can have the following structure of Chemical Formula 1: 
       [ABX 3 ]  [Chemical Formula 1]
 
     In Chemical Formula 1, A is an organic ammonium or alkali metal; B is a metal selected from the group consisting of divalent transition metal, rare earth metal, alkaline earth metal, Pb, Sn, Ge, Ga, In, Al, Sb, Bi, Po and combination thereof; and X is halogen selected from the group consisting of Cl, Br, I and combination thereof. 
     For example, when the A is an organic ammonium, the inorganic luminescent particle  300  constitutes an inorganic-organic hybrid Perovskite structure. The organic ammonium can comprise, but is not limited to, amidinium-based organic ion, (CH 3 NH 3 ) n , ((C x H 2x+1 ) n NH 3 ) 2 (CH 3 NH 3 ) n , (CnH 2n+1 NH 3 ) 2 , (CF 3 NH 3 ), (CF 3 NH 3 ) n , ((C x F 2x+1 ) n NH 3 ) 2 (CF 3 NH 3 ) n , ((C x F 2x+1 ) n NH 3 ) 2  and/or (CnF 2n+1 NH 3 ) 2 )(each of n and x is independently an integer equal to or more than 1, respectively). More specifically, the organic ammonium can be methyl ammonium or ethyl ammonium. 
     In addition, the alkali metal of the A can comprise, but is not limited to, Na, K, Rb, Cs and/or Fr. In this case, the inorganic luminescent particle constitutes an inorganic metal Perovskite structure. 
     For example, when the core  310  of the inorganic luminescent particle  300  having Perovskite structure is the inorganic-organic hybrid Perovskite structure, the inorganic-organic hybrid Perovskite structure has a layered structure in which an inorganic plane in which a metal cation is located is sandwiched between organic planes in which the organic cations are located. In this case, since the difference between the dielectric constant of the organic and inorganic materials is large, exciton is constrained in the inorganic plane constituting the inorganic-organic hybrid Perovskite lattice structure, and thus has the advantage of emitting light having high color purity. Also, when the core  310  of the inorganic luminescent particle  300  having Perovskite structure has the inorganic-organic hybrid Perovskite structure, it can be advantageous in terms of material stability. 
     By adjusting the composition ratio of each component, the kind and composition ratio of halogen (X) atom in the core  310  of the inorganic luminescent particle  300  having the Perovskite structure, it is possible to synthesize the core emitting light in various wavelengths. In addition, unlike the cores constituting other QDs or QRs, the inorganic luminescent particle  300  having Perovskite structure has a stable lattice structure, and thus luminous efficiency can be improved. 
     The organic ligand  330  bound to the surface on the inorganic luminescent particle  300  is not particularly limited. For example, the organic ligand  330  can comprise, but is not limited to, C 5 -C 30  saturated or unsaturated aliphatic acids such as lauric acid or oleic acid; C 5 -C 20  aliphatic amines such as oleylamine; phosphine oxides; and C 2 -C 20  alkyl thiols. As an example, the organic ligand  330  can be aliphatic acids. 
     When the inorganic luminescent particles  300  (e.g., QDs and/or QRs) are synthesized or the EML  240  is disposed using the inorganic luminescent particles  300 , some of the organic ligand  300  bound to the surface on the inorganic luminescent particles  300  are detached or separated from the particles  300 , thus the surface of the inorganic luminescent particles  300  are exposed to external environment. As the inorganic luminescent particles  300 , which is feasible to external environment such as oxygen or moisture, is not protected by the organic ligand  330 , voids are formed in some of the EML  240  when the EML  240  consisting only the inorganic luminescent particles  300 . In this case, leakage current is occurred in the inorganic LED D1 in which the EML consists of only the inorganic luminescent particles  300 . 
     In addition, atoms exposed on the surface of the shell  320  constituting the outmost of the inorganic luminescent particles  300  have lone pair electrons which do not participate in a chemical bond. Such surface atoms cause charges such as holes and electrons to be trapped on the surface of the inorganic luminescent particles  300 , and thereby resulting in surface defects. As the component composition in the shell  320  is changed by the surface defects, there exists a vacancy among the components in the shell  302 , and thereby, the lattice constant of the shell  320  is shifted. As a result, as the exciton confinement efficiency in the inorganic luminescent particles  300  are reduced, the inorganic luminescent particles  300  shows deteriorated luminous efficiency. 
     To address such problems and disadvantages, the EML  240  of the present disclosure includes the siloxane matrix  400  dispersing the inorganic luminescent particles  300 . Now, we will explain the functions and roles of the siloxane matrix that stabilizes the inorganic luminescent particles  300  in the EML  240  with referring to  FIG. 3 . As described above, some of the organic ligand  330  that is bound to the surface of the inorganic luminescent particles  300  are detached from the particles  300  in the course of synthesizing the particles  300  or disposing the EML  240 , thus the surface defects or voids are formed on the inorganic luminescent particles  300 . 
     On the contrary, the inorganic luminescent particles  300  are dispersed in the siloxane matrix  400  which can form a network structure. As the siloxane matrix  400  having a network structure encloses the inorganic luminescent particles  300 , the organic ligand  330  is rarely detached from the surface of the shell  320  which is the outmost of inorganic luminescent particles  300 . As a result, the siloxane matrix  400  allows the surface defects on the inorganic luminescent particles  300  to be minimized to stabilize the inorganic luminescent particles  300 . 
     In other words, the siloxane matrix  400  stabilizes the surface of the inorganic luminescent particle to prevent the surface defects of the inorganic luminescent particles  300 . In this case, the shift of the lattice constant of the shell  320  caused by the charge traps on the surface of the inorganic luminescent particles  300  or the vacancy of the component in the shell  320  can be minimized. Holes and electrons are recombined in the inorganic luminescent particles  300  in the EML  240  without trapping on the surface of the inorganic luminescent particles  300  to emit stably, thus the exciton confinement efficiency of the inorganic luminescent particles  300  are improved. The inorganic LED D1 in which the EML includes the inorganic luminescent particles  300  dispersed in the siloxane matrix  400  can lower its driving voltage and enhance its luminous efficiency. 
     The siloxane matrix  400  has a thickness T 2  equal to or less than a thickness T 1  of a layer of the inorganic luminescent particles  300 . When the thickness T 2  of the siloxane matrix  400  exceeds the thickness T 1  of the layer of the inorganic luminescent particles  300 , charges injection can be delayed due the insulator, i.e., the siloxane matrix  400 . As an example, when the inorganic luminescent particles  300  are formed in a mono-layer, the thickness T 2  of the siloxane matrix  400  can be equal to or less than the size of the inorganic luminescent particles  300 , for example, a radius of the inorganic luminescent particles  300  when the particles  300  are quantum dots. 
     In one exemplar aspect, the thickness T 2  of the siloxane matrix  400  can be between about a tenth (10%), preferably about a fourth (25%), and more preferably about a third (33.3%) of the thickness T 1  of the layer of the inorganic luminescent particles  330 , and the thickness T 1  of the layer of the inorganic luminescent particles  330 . When the siloxane matrix  400  has the thickness T 2  less than a tenth of the thickness T 1  of the layer of the inorganic luminescent particles  330 , the siloxane matrix  400  does not enclose sufficiently the outside of the inorganic luminescent particles  300 . Organic ligands  330  bound to the surface of the inorganic luminescent particles  300  that is not enclosed by the siloxane matrix  400  are detached from the inorganic luminescent particles  300 , voids and/or surface defects can be formed on the surface of the inorganic luminescent particles  300 . 
     In one exemplary aspect, the inorganic luminescent particles  300  and the siloxane  400  can be mixed with a volume ratio of about 1:0.01 to about 1:4, preferably about 1:0.5 to about 1:2, and more preferably about 1:0.1 to about 1:1 in fabricating the EML  240 . By adjusting the mixing ratio between the inorganic luminescent particles  300  and the siloxane  400 , the EML  240  in which the thickness T 2  of the siloxane matrix  400  is between a tenth or more of the layer thickness T 1  of the inorganic luminescent particles  300  and equal to or less that the layer thickness T 1  of the inorganic luminescent particles  300  can be fabricated. 
     The siloxane matrix  400  can be synthesized a monomer comprising at least one silanol group and/or a siloxane group. Such monomers can crosslink each other through curing processes such as heat treatment to form the siloxane matrix  400 . As an example, the monomer having the silanol group can comprise a silanol group-containing monomer such as ethylene-based unsaturated alkoxy silanes and ethylene-based unsaturated acyloxy silanes that is obtained by hydrolyzing a silyl group-containing unsaturated monomer. 
     For example, the ethylene-based unsaturated alkoxy silanes can comprise, but is not limited to, 1) acrylate-based alkoxy silanes such as -acryloxypropyl-trimethoxy silane, γ-acryloxypropyl-triethoxy silane, 2) methacrylate-based alkoxy silanes such as γ-methacryloxypropyl-trimethoxy silane, γ-methacryloxypropyl-triethoxy silane, γ-methacryloxymethyl-triethoxysilane, γ-methacryloxypropyl-tris(2-methoxyethoxy)silane. 
     Ethylene-based unsaturated acyloxy silanes can comprise, but is not limited to, acrylate-based acetoxy silanes, methacrylate-based acetoxy silanes and ethylene-based unsaturated acetoxy silanes (e.g., acrylatopropyl triacetoxy silane, methacrylatopropyl triacetoxy silane). 
     Silyl group-containing unsaturated compound that can obtained the monomer having the silanol group through hydrolysis can comprise, but is not limited to, chlorodimethyl vinyl silane, 5-trimethylsilyl-1,3-cyclopentadiene, 3-trimethylsilylallyl alcohol, trimethylsilyl methacrylate, 1-trimethylsilyl-1,3-butadiene, 1-trimethylsilyl cyclopentene, 2-trimethylsilyloxyethyl methacrylate, 2-trimethylsilyl oxyfuran, 2-trimethylsily oxypropene, and trisalkoxy silanes such as allyloxy-t-butyl dimethyl silane, allyloxy-trimethyl silane, trimethoxy-vinyl silane, triethoxy-vinyl silane, tris(methoxyethoxy) vinyl silane. Such a monomer having the silanol group can be used alone or in combination of two or more. 
     In another exemplary aspect, a precursor for the siloxane matrix  400  comprises a monomer having the siloxane group. The monomer having the siloxane group can include a monomer having a linear siloxane group, a monomer having a cyclic siloxane group, a monomer having a tetrahedral siloxane group and silsesquioxane. 
     As an example, the monomer having the linear siloxane group can comprise an alkyl siloxane, an alkoxy siloxane, an alkylalkoxy siloxane, a vinylalkoxy siloxane each of which is substituted with 4-8 C 1 -C 10  alkyl groups and/or C 1 -C 10  alkoxy groups. For example, the monomer having the linear siloxane group can have the following structure of Chemical Formula 2: 
     
       
         
         
             
             
         
       
     
     In Chemical Formula 2, each of R 1  and R 2  is independently selected from the group consisting of protium, deuterium, tritium, a hydroxyl group, a linear or branched C 1 -C 10  alkyl group, a C 2 -C 20  alkenyl group, a C 1 -C 10  alkoxy group, a C 1 -C 10  alkyl amino group, a C 1 -C 10  alkyl acryloxy group, a C 1 -C 10  alkyl methacryloxy group, a thiol group, a C 1 -C 10  alkyl thiol group, an ioscyanate group, a C 1 -C 10  alkyl ioscyanate group, an epoxy group, a C 1 -C 10  epoxy group, a C 5 -C 20  cycloaklyl epoxy group, a C 6 -C 20  aryl epoxy group, a C 4 -C 20  hetero aryl epoxy group, a glycidyloxy group, a C 1 -C 10  alkyl glycidyloxy group, an unsubstituted or halogen substituted C 6 -C 20  aryl group, an unsubstituted or halogen substituted C 4 -C 20  hetero aryl group, an unsubstituted or halogen substituted C 6 -C 20  aryloxy group, an unsubstituted or halogen substituted C 4 -C 20  hetero aryloxy group, an unsubstituted or halogen substituted C 6 -C 20  aryl amino group and an unsubstituted or halogen substituted C 4 -C 20  hetero aryl amino group; each of R 3  and R 4  is independently selected from the group consisting of protium, deuterium, tritium, a linear or branched C 1 -C 10  alkyl group, a C 1 -C 10  alkyl amino group, a C 6 -C 20  aryl group, a C 4 -C 20  hetero aryl group, a C 6 -C 20  aryl amino group and a C 4 -C 20  hetero aryl amino group. 
     In one exemplary aspect, the linear or branched C 1 -C 10  alkyl group in each of R 1  to R 4  can be a linear or branched C 1 -C 10  alkyl group. In another exemplary aspect, the unsubstituted or halogen substituted C 6 -C 20  aryl group in each of R 1  to R 4  cancan comprise independently, but is not limited to, phenyl, biphenyl, terphenyl, naphthyl, anthracenyl, pentalenyl, indenyl, indeno-indenyl, heptalenyl, biphenylenyl, indacenyl, phenalenyl, phenanthrenyl, benzo-phenanthrenyl, dibenzo-phenanthrenyl, azulenyl, pyrenyl, fluoranthenyl, triphenylenyl, chrysenyl, tetraphenylenyl, tetracenyl, pleiadenyl, picenyl, pentaphenylenyl, pentacenyl, fluorenyl, indeno-fluorenyl and spiro-fluorenyl, preferably phenyl, biphenyl, naphthyl, anthracenyl and indenyl, each of which can be unsubstituted or substituted with halogen. 
     In still another exemplary aspect, the C 4 -C 20  hetero aryl group in each of R 1  to R 4  can comprise independently, but is not limited to, an unfused or fused hetero aryl group such as pyrrolyl, pyridyl, pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl, imidazolyl, pyrazolyl, indolyl, iso-indolyl, indazolyl, indolizinyl, pyrrolizinyl, carbazolyl, benzo-carbazolyl, dibenzo-carbazolyl, indolo-carbazolyl, indeno-carbazolyl, benzo-furo-carbazolyl, benzo-thieno-carbazolyl, carbolinyl, quinolinyl, iso-quinolinyl, phthlazinyl, quinoxalinyl, cinnolinyl, quinazolinyl, quinolizinyl, purinyl, benzo-quinolinyl, benzo-iso-quinolinyl, benzo-quinazolinyl, benzo-quinoxalinyl, acridinyl, phenazinyl, phenoxazinyl, phenothiazinyl, phenanthrolinyl, perimidinyl, phenanthridinyl, phtheridinyl, naphthyridinyl, furanyl, pyranyl, oxazinyl, oxazolyl, oxadiazolyl, triazolyl, dioxinyl, benzo-furanyl, dibenzo-furanyl, thiopyranyl, xanthenyl, chromenyl, iso-chromenyl, thioazinyl, thiophenyl, benzo-thiophenyl, dibenzo-thiophenyl, difuro-pyrazinyl, benzofuro-dibenzo-furanyl, benzothieno-benzo-thiophenyl, benzothieno-dibenzo-thiophenyl, benzothieno-benzo-furanyl, benzothieno-dibenzo-furanyl, xanthne-linked spiro acridinyl, dihydroacridinyl, preferably pyridyl and pyrimidinyl, each of which is unsubstituted or substituted with halogen. 
     For example, R 1  in Chemical Formula 2 can be selected from the group consisting of protium, deuterium, tritium, a hydroxyl group, a linear or branched C 1 -C 10  alkyl group, a C 2 -C 20  alkenyl group, a C 1 -C 10  alkoxy group, a C 1 -C 10  alkyl amino group, a C 1 -C 10  alkyl acryloxy group, a C 1 -C 10  alkyl methacryloxy group, a thiol group, a C 1 -C 10  alkyl thiol group, a C 1 -C 10  alkyl glycidyloxy group and a C 6 -C 20  aryl group, R 2  can be selected from the group consisting of a hydroxyl group and a C 1 -C 10  alkoxy group, and each of R 3  and R 4  can be independently selected from the group consisting of protium, deuterium, tritium and a linear or branched C 1 -C 10  alkyl group. 
     In one exemplary aspect, the silicon atom in the siloxane monomer that can form the siloxane matrix  400  can be substituted with at least two, preferably at least three hydrolysable groups such as an alkoxy group, an unsubstituted or halogen substituted aryloxy group and/or an unsubstituted or halogen substituted hetero aryloxy group. 
     As an example, the siloxane monomer having the structure of Chemical Formula 2 can comprise alkoxy silanes having at least two alkoxy groups as the hydrolysable groups. For example, the siloxane monomer having two alkoxy groups can comprise, but is not limited to, dimethyldiethoxy silane, methyl (vinyl) diethoxy silane, 3-aminopropyl (methyl) diethoxy silane, (3-acryloxypropyl) methyldimethoxy silane, 3-glycidoxypropyl (methyl) diethoxy silane and methyl (phenyl) diethoxy silane. 
     The siloxane monomer having three alkoxy groups can comprise, but is not limited to, methyl trimethoxy silane, methyl triethoxy silane, ethyl triethoxy silane, n-propyl triethoxy silane, octyl triethoxy silane, vinyl triethoxy silane, 3-aminopropyl trimethoxy silane, 3-aminopropyl triethoxy silane, 3-(2-aminoethylamino) propyl trimethoxy silane, (3-acryoxyoropyl) trimethoxy silane, methacryloxymethyl triethoxy silane, 3-methacryloxypropyl trimethoxy silane, 3-methacryloxypropyl triethoxy silane, 3-mercaptopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, 2-(3,4-epoxycyclohexyl) ethyl triethoxy silane, 3-glycidyloxyopropyl trimethoxy silane, 3-glycidyloxypropyl trimethoxy silane, 3-glycidyloxypropyl triethoxy silane, phenyl trimethoxy silane, (4-chlorophenyl) triethoxy silane and [3-(phenylamino) propyl] trimethoxy silane. 
     The siloxane monomer having four alkoxy groups can comprise, but is not limited to, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), tetrabutyl orthosilicate (TBOS) and tetrakis (2-ethylhexyl) orthosilicate (TEHOS). 
     The cyclic siloxane monomer can comprise, but is not limited to, cyclo trisiloxane such as methyl hydro-cyclosiloxane, hexamethyl-cyclotrisilosane and hexaethyl-cyclo trisiloxane; cyclo tetrasiloxane such as tetraoctyl-cyclo tetrasiloxane; tetra- or penta-methyl cyclo tetrasiloxane; tetra-, penta-, hexa- or hepta-methyl cyclo pentasiloxane; penta- or hexa-methyl-cyclo hexasiloxane, tetraethyl-cyclo tetrasiloxane and tetraphenyl cyclo tetrasiloxane; decamethyl-cyclo pentasiloxane, dodecamethyl-cyclosiloxane, 1,3,5,7-tetramethyl-cyclo tetrasiloxane, 1,3,5,7,9-pentamethyl-cyclo pentasiloxane, 1,3,5,7,9,11-hexamethyl-cyclo hexasiloxane and combination thereof. 
     The monomer having the tetrahedral siloxane group can comprise, but is not limited to, tetrakis dimethyl siloxy silane, tetrakis diphenyl siloxy silane and tetrakis diethyl siloxy silane. 
     In addition to the linear, cyclic or tetrahedral siloxane, silsesquionxne (SSQ), for example, that can by synthesized by a reaction between methyl trichloro siloxane and dimethyl chloro siloxane, can be used as the precursor for the siloxane matrix  400 . Silsesquioxane can be cross-linked to synthesize poly-silsesquioxane having a ladder or a cage structure. For example, organo trichloro siloxane is hydrolyzed to synthesize a heptamer siloxane having a partial cage structure and a heptamer or an octamer siloxane having a cage structure. The obtained heptamer siloxane can be separated by solubility differences, and then the separated heptamer siloxane and organo trialkoxy silane or organo trichloro siloxane are condensed to obtain a silsesquioxane monomer. The silsesquioxane can have, but is not limited to, a chemical structure RSiO 3/2  (R is hydrogen, a C 1 -C 10  alkyl group, a C 2 -C 10  alkenyl group, an aryl group such as phenyl, or an arylene group), 
     In one exemplary aspect, the siloxane monomer for the siloxane matrix  400  can be an orthosilicate having four siloxane groups such as TMOS, TEOS, TPOS, TBOS and TEHOS. The orthosilicate is chemically stable, and can form network structures by heat to form the siloxane matrix  400 . 
     When the EML  240  includes inorganic luminescent particles  300  such as QDs and/or QRs and the siloxane matrix  400  dispersing the inorganic luminescent particles  300 , the EML  240  can be fabricated using a solution in which the inorganic luminescent particles  300  and the siloxane  400  are dispersed in an organic solvent, typically a C 1 -C 20  aliphatic hydrocarbon such as a C 3 -C 20  alkane. As an example, the EML  240  can be fabricated by applying the solution in which the inorganic luminescent particles  300  and the siloxane  400  are dispersed in the solvent on the CTL1  250  and then by evaporating the solvent to disperse the inorganic luminescent particles  300  in the siloxane matrix  400 . In one exemplary aspect, the EML  240  can be fabricated on the CTL1  250  using any soluble process such as spin coating, drop coating, dip coating, spray coating, roll coating, flow coating casting, screen printing and inkjet printing, or a combination thereof. 
     In one exemplary aspect, the EML  240  can include inorganic luminescent particles  300  such as QDs and/or QRs having photoluminescence (PL) wavelength peaks of 440 nm, 530 nm, and 620 nm so as to realize white LED. Optionally, the EML  240  can include inorganic luminescent particles  300  such as QDs or QRs having any one of red, green and blue colors, and can be formed to emit any one color. As an example, the EML  240  can have a thickness of, but is not limited to, about 5 nm to about 300 nm, preferably about 10 nm to about 200 nm. 
     Referring back to  FIG. 2 , in this aspect, the CTL1  250  can be a hole transfer layer which provides holes with the EML  240 . As an example, the CTL1  250  can include a hole injection layer (HIL)  252  disposed adjacently to the first electrode  210  between the first electrode  210  and the EML  240 , and a hole transport layer (HTL)  254  disposed adjacently to the EML  240  between the first electrode  210  and the EML  240 . 
     The HIL  252  facilitates the injection of holes from the first electrode  210  into the EML  240 . As an example, the HIL  252  can include, but is not limited to, an organic material selected from the group consisting of poly(ethylenedioxythiophene).polystyrenesulfonate (PEDOT:PSS); 4,4′,4″-tris(diphenylamino)triphenylamines (TDATA) doped with tetrafluoro-tetracyano-quinodimethane (F4-TCNQ); p-doped phthalocyanine such as zinc phthalocyanine (ZnPc) doped withF4-TCNQ; N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4″-diamine (α-NPD) doped with F4-TCNQ; hexaazatriphenylene-hexanitrile (HAT-CN); and a combination thereof. As an example, the HIL  252  can include the dopant such as F4-TCNQ in about 1 to about 30% by weight. The HIL  252  can be omitted in compliance with a structure of the inorganic LED D1. 
     The HTL  254  transports holes from the first electrode  210  into the EML  240 . The HTL  254  can include an inorganic material or an organic material. As an example, when the HTL  254  includes an organic material, the HTL  254  can include, but is not limited to, 4,4′-bis(p-carbazolyl)-1,1′-biphenyl compounds such as 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and 4,4′-bis(9-carbazolyl)-2,2′-dimethylbiphenyl (CDBP); aromatic amines, i.e. aryl amines or polynuclear aromatic amines selected from the group consisting of α-NPD, N4,N4′-di(naphthalene-1-yl)-N4,N4′-bis(4-vinylphenyl)biphenyl-4,4′-diamine (VNPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD), N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-spiro (spiro-TPD), N,N′-di(4-(N,N′-diphenyl-amino)phenyl)-N,N′-diphenylbenzidine (DNTPD), N,N′-Bis(3-methylphenyl)-N,N′-bis(phenyl)-9,9′-dioctylfluorene (DOFL-TPD), N2,N7-Di(naphthalene-1-yl)-9,9-dioctyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (DOFL-NPB), N4,N4′-Bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyl)phenyl)-N4,N4′-diphenylbiphenyl-4,4′-diamine (OTPD), tris(4-carbazolyl-9-ylphenyl)amine (TCTA), tetra-N-phenylbenzidine (TPB), tris(3-methylphenylphenylamino)-triphenylamine (m-MTDATA), poly(9,9′-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine (TFB), poly(4-butylphenyl-dipnehyl amine) (poly-TPD), spiro-NPB and combination thereof, conductive polymers such as polyaniline, polypyrrole, PEDOT:PSS; poly(N-vinylcarbazole) (PVK) and its derivatives; poly(para)phenylene vinylenes (PPV) and its derivatives such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MOMO-PPV); polymethacrylate and its derivatives; poly(9,9-octylfluorene) and its derivatives; poly(spiro-fluorene) and its derivatives; polyvinylfluoro and its derivatives such as poly[9-sec-butyl-2,7-difluoro-9H-carbazole] (2,7-F-PVF); metal complexes such as copper phthalocyanine (CuPc); and combination thereof. 
     In one exemplary aspect, the HTL  254  can have a multi-layered structure of a first HTL (HTL1) disposed between the HIL  252  and the EML  240  and a second HTL (HTL2) disposed between the HTL1 and the EML  240 . In this case, the HTL2 can be designed to have HOMO (Highest Occupied Molecular Orbital) energy deeper than HOMO energy level of the HTL1. As an example, the HTL1 can include, but is not limited to, TFB (HOMO: −5.3 eV), poly-TPD (HOMO: −5.1 eV) and/or VNPG (HOMO: −5.58 eV), and the HTL2 can include, but is not limited to, CBP (HOMO: −6.15 eV), PVK (HOML: −5.91 eV) and/or 2,7-F-PVF (HOMO: −6.3 eV). 
     Alternatively, when the HTL  254  includes an inorganic material, the HTL  254  can comprise an inorganic material selected from the group consisting of a metal oxide nanocrystal, a non-oxide metal nanocrystal and combination thereof. The metal oxide nanocrystal that can be used in the HTL  254  can be oxide nanocrystal of metal selected from Zn, Ti, Ni, Co, Cu, W, Sn, Cr, V, Mo, Mn, Pb, Ce, Re and combination thereof. For example, the metal oxide nanocrystal that can be used in the HTL  254  can be selected from, but is not limited to, the group consisting of ZnO, TiO 2 , CoO, CuO, Cu 2 O, FeO, In 2 O 3 , MnO, NiO, PbO, SnOx, Cr 2 O 3 , V 2 O 5 , Ce 2 O 3 , MoO 3 , Bi 2 O 3 , ReO 3  and combination thereof. The non-oxide metal nanocrystal can comprise, but is not limited to, CuSCN, Mo 2 S and p-type GAN. Alternatively, the metal oxide and/or the non-oxide metal nanocrystal in the HTL  254  can be doped with a p-dopant. As an example, the p-dopant can be selected from, but is not limited to, Li + , Na + , K + , Sr + , Ni 2+ , Mn 2+ , Pb 2+ , Cu + , Cu 2+ , C 2+ , Al 3+ , Eu 3+ , In 3+ , Ce 3+ , Er 3+ , Tb 3+ , Nd 3+ , Y 3+ , Cd 2+ , Sm 3+ , N, P, As and combination thereof. 
     In  FIG. 2 , while the CTL1  250  is divided into the HIL  252  and the HTL  254 , the CTL1  250  can have a mono-layered structure. For example, the CTL1  250  can include only the HTL  254  without the HIL  252  or can include the above-mentioned hole transporting material doped with the hole injection material (e.g., PEDOT:PSS). 
     The CTL1  250  including the HIL  252  and the HTL  254  can be laminated by any vacuum deposition process such as vacuum vapor deposition and sputtering, or by any soluble process such as spin coating, drop coating, dip coating, spray coating, roll coating, flow coating, casting, screen printing and inkjet printing, or a combination thereof. For example, each of the HIL  252  and the HTL  254  can have a thickness, but is not limited to, between about 10 nm and 200 nm, alternatively, about 10 nm and 100 nm. 
     The CTL2  270  is disposed between the EML  240  and the second electrode  230 . In this aspect, the CTL2  270  can be an electron transfer layer which provides electrons into the EML  240 . In one exemplary aspect, the CTL2  270  can include an electron injection layer (EIL)  272  disposed adjacently to the second electrode  230  between the second electrode  230  and the EML  240 , and an electron transport layer (ETL)  274  disposed adjacently to the EML  240  between the second electrode  230  and the EML  240 . 
     The EIL  272  facilitates the injection of electrons from the second electrode  230  into the EML  240 . For example, the EIL  272  can include, but is not limited to, a metal such as Al, Cd, Cs, Cu, Ga, Ge, In and/or Li, each of which is undoped or doped with fluorine; and/or metal oxide such as TiO 2 , ZnO, ZrO 2 , SnO 2 , WO 3  and/or Ta 2 O 3 , each of which is undoped or doped with Al, Mg, In, Li, Ga, Cd, Cs or Cu. 
     The ETL  274  transfers electrons into the EML  240  and comprises an inorganic material or an organic material. In one exemplary aspect, the ETL  274  can include an inorganic material so as to prevent an interface defect from being formed at an interface between the EML  240  and the ETL  274 , and thereby securing driving stability of the inorganic LED D1. In addition, when the ETL  274  includes an inorganic material having high charge mobility, the electron transport rate provided from the second electrode  230  can be improved, and electrons can be transported efficiently into the EML  240  owing to high electron levels or concentrations. 
     Moreover, in one exemplary aspect, the ETL  274  can include an inorganic material having relatively deep VB (valence band) energy level compared to VB energy level of the inorganic luminescent particles  300  in the EML  240 . As an example, an inorganic material having wide energy level bandgap (Eg) between the VB energy level and a CB (conduction band) energy level can be used as an electron transporting material of the ETL  274 . In this case, electrons can be efficiently injected into the EML  240  from the second electrode  230  via the ETL  274 . 
     In one exemplary aspect, the ETL  274  can comprise, but is not limited, an inorganic material such as a metal oxide nanocrystal, a semiconductor nanocrystal, a nitride and/or combination thereof. For Example, the ETL  274  can comprise the metal oxide nanocrystal. 
     As an example, the metal oxide nanocrystal in the ETL  274  can comprise, but is not limited to, an oxide nano particle of a metal component selected from the group consisting of Zn, Ca, Mg, Ti, Sn, W, Ta, Hf, Al, Zr, Ba and combination thereof. More particularly, the metal oxide in the ETL  274  can comprise, but is not limited to, TiO 2 , ZnO, ZnMgO, ZnCaO, ZrO 2 , SnO 2 , SnMgO, WO 3 , Ta 2 O 3 , HfO 3 , Al 2 O 3 , BaTiO 3 , BaZrO 3  and combination thereof. The semiconductor nanocrystal in the ETL  274  can comprise, but is not limited to CdS, ZnSe, ZnS, and the like, the nitride in the ETL  274  can comprise, but is not limited to, Si 3 N 4 . 
     In one exemplary aspect, the ETL  274  can be designed to have the CB (or LUMO) energy level substantially equal to the CB energy level of the EML  240  while the VB energy level deeper than the VB energy level of the EML  240 . To this end, the ETL  274  can further include a material (n-dopant) doped to the inorganic nanocrystals. The n-dopant in the ETL  274  can comprise, but is not limited to, cation of metal selected from Al, Mg, In, Li, Ga, Cd, Cs and Cu, particularly trivalent cation. 
     In an alternative aspect, when the ETL  274  comprises an organic material, the ETL  274  can comprise, but is not limited to, oxazole-based compounds, isoxazole-based compounds, triazole-based compounds, isotriazole-based compounds, oxadiazole-based compounds, thiadiazole-based compounds, phenanthroline-based compounds, perylene-based compounds, benzoxazole-based compounds, benzothiazole-based compounds, benzimidazole-based compounds, triazine-based compounds and aluminum complexes. 
     More particularly, the organic material in the ETL  274  can comprise, but is not limited to, 3-(4-Biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 2,9-Dimethyl-4,7-diphenyl-1,10-phenaathroline (bathocuproine, BCP), 1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole (TPBi), Tris(8-hydroxyquinoline)aluminum (Alq 3 ), bis(2-methyl-8-quninolinato)-4-phenylphenolatealuminum (III) (BAlq), bis(2-methyl-quinolinato)(tripnehylsiloxy) aluminum (III) (Salq) and combination thereof. 
     Similar to the CTL1  250 , while  FIG. 2  illustrates the CTL2  270  as a bi-layered structure including the EIL  272  and the ETL  274 , the CTL2  270  can have a mono-layered structure having only the ETL  274 . Alternatively, the CTL2  270  can have a mono-layered structure of ETL  274  including a blend of the above-described electron-transporting inorganic material with cesium carbonate. 
     The CTL2  270 , which includes the EIL  272  and/or the ETL  274  having the inorganic material, can be fabricated on the EML  240  by any vacuum deposition process such as vacuum vapor deposition and sputtering, or soluble process such as spin coating, drop coating, dip coating, spray coating, roll coating, flow coating, casting, screen printing and inkjet printing, or combination thereof. As an example, each of the EIL  272  and the ETL  274  can have a thickness, but is not limited to, between about 10 nm and about 200 nm, alternatively, about 10 nm and 100 nm. 
     For example, the inorganic LED D1 can have a hybrid CTL structure in which the HTL  254  of the CTL1  250  includes the organic material as describe above and the CTL2  270 , for example, the ETL  274  includes the inorganic material as described above. In this case, The inorganic LED D1 can enhance its luminous properties. 
     In the first aspect, the emissive layer includes only an EML and charge transfer layers. Unlikely, the inorganic LED of the present disclosure can further comprise at least one exciton blocking layer that controls the charger transfers.  FIG. 4  is a schematic cross-sectional view illustrating an inorganic light emitting diode (LED) in accordance with another exemplary aspect of the present disclosure. 
     As illustrated in  FIG. 4 , the inorganic LED D2 includes the first electrode  210 , the second electrode  230  facing the first electrode  210  and an emissive layer  220 A disposed between the first and second electrodes  210  and  230 . The inorganic light emitting display device  100  ( FIG. 1 ) can include a red pixel region, a green pixel region, and a blue pixel region, and the inorganic LED D2 can be disposed in any pixel region of the red, green and blue pixel regions. The emissive layer  220 A comprises the EML  340 , and can comprise at least one of the CTL1  350  disposed between the first electrode  210  and the EML  240  and the CTL2  270  disposed between the EML  240  and the second electrode  230 . In addition, the emissive layer  220 A further comprise an EBL  265  as a first exciton blocking layer disposed between the CTL1  250  and the EML  240  and a HBL  275  as a second exciton blocking layer disposed between the EML  240  and the CTL2  270 . The configuration of the electrodes  210  and  230  and the emissive layer  220 A other than the EBL  265  and HBL  275  can be substantially the same as the corresponding elements in the inorganic LED D1. 
     The EBL  265  prevents reduction of the luminous lifetime and luminous efficiency of the inorganic LED D2 when electrons are transferred to the first electrode  210  through the EML  240 . In other words, the EBL  265  prevents the electron transfer between the HTL  254  and the EML  240 . In one exemplary aspect, the EBL  265  can comprises, but is not limited to, TCTA, Tris[4-(diethylamino)phenyl]amine, N-(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluorene-2-amine, tri-p-tolylamine, 1,1-bis(4-(N,N′-di(ptolyl)amino)phenyl)cyclohexane (TAPC), m-MTDATA, 1,3-bis(N-carbazolyl)benzene (mCP), 3,3′-bis(N-carbazolyl)-1,1′-biphenyl (mCBP), poly-TPD, CuPc, DNTPD and 1,3,5-tris[4-(diphenylamino)phenyl]benzene(TDAPB). 
     The HBL  275  prevents reduction of the luminous lifetime and luminous efficiency of the inorganic LED D2 when holes are transferred to the second electrode  230  through the EML  240 . In other words, the HBL  275  prevents the hole transfer between the ETL  274  and the EML  240 . In one exemplary aspect, the HBL  275  can comprise, but is not limited to, oxadiazole-based compounds, triazole-based compounds, phenanthroline-based compounds, benzoxazole-based compounds, benzothiazole-based compounds, benzimidazole-based compounds, triazine-based compounds and aluminum complexes. For example, the HBL  275  can comprise a compound having a relatively low HOMO energy level compared to the luminescent materials in EML  240 . The HBL  275  can comprise, but is not limited to, BCP, BAlq, Alq 3 , 2-biphenyl-4-yl-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD), PBD, spiro-PBD and Liq. 
     The EML  240  in the emissive layer  220 A also comprises the inorganic luminescent particles  300  and the siloxane matrix  400  dispersing the inorganic luminescent particles  300  (see,  FIG. 3 ). The siloxane matrix  400  has the thickness T 2  equal to or less than the thickness T 1  of the layer of the inorganic luminescent particles  300 , and preferably, a tenth or more, preferably a fourth or more, and more preferably a third or more of the thickness T 1  of the layer of the inorganic luminescent particles  300 . The siloxane matrix  400  having the predetermined thickness T 1  in the EML  240  allows the inorganic luminescent particles  300  to become much stabilized and the surface defects on the inorganic luminescent particles  300  to be minimized, and therefore stabilizes excitons formed by recombination among holes and electrons in the EML  240 . As a result, the inorganic LED D2 can lower its driving voltage and power consumption as well as improve its luminous efficiency. 
     In an alternative aspect, an inorganic LED can include multiple emitting parts.  FIG. 5  is a schematic cross-sectional view illustrating an OLED in accordance with still another exemplary aspect of the present disclosure. 
     As illustrated in  FIG. 5 , the inorganic LED D3 comprises first and second electrodes  210  and  230  facing each other and an emissive layer  220 B with two emitting parts disposed between the first and second electrodes  210  and  230 . The inorganic light emitting display device  100  ( FIG. 1 ) can include a red pixel region, a green pixel region and a blue pixel region, and the inorganic LED D3 can be disposed in any pixel region of the red, green and blue pixel regions. The first electrode  210  can be an anode and the second electrode  220  can be a cathode. 
     The emissive layer  220 B includes a first emitting part  620  that includes a first EML (EML1)  640 , and a second emitting part  720  that includes a second EML (EML2)  740 . Also, the emissive layer  220 B can further comprise a charge generation layer (CGL)  680  disposed between the first emitting part  620  and the second emitting part  720 . 
     The CGL  680  is disposed between the first and second emitting parts  620  and  720  so that the first emitting part  620 , the CGL  680  and the second emitting part  720  are sequentially disposed on the first electrode  210 . In other words, the first emitting part  620  is disposed between the first electrode  210  and the CGL  680  and the second emitting part  720  is disposed between the second electrode  230  and the CGL  680 . 
     The first emitting part  620  comprises the EML1  640 . The first emitting part  620  can comprise at least one of a lower first charge transfer layer (first hole transfer layer)  650  disposed between the first electrode  210  and the EML1  640  and a lower second charge transfer layer (first electron transfer layer)  670  disposed between the EML1  640  and the CGL  680 . In one exemplary aspect, the first hole transfer layer  650  can comprise a HIL  652  disposed between the first electrode  210  and the EML1  640  and a first HTL (HTL1)  654  disposed between the EML1  640  and the HIL  652 . Alternatively, the first hole transfer layer  650  can have a single-layered structure of the HTL1  654 . The first electron transfer layer  670  can have a single-layered structure of a first ETL (ETL1)  674 . Alternatively, the first emitting part  620  can further comprise a first EBL (EBL1) disposed between the EML1  640  and the first hole transfer layer  650  and/or a first HBL (HBL1) disposed between the EML1  640  and the first electron transfer layer  670 . 
     The second emitting part  720  comprises the EML2  740 . The second emitting part  720  can comprise at least one of an upper first charge transfer layer (second hole transfer layer)  750  disposed between the CGL  680  and the EML2  740  and an upper second charge transfer layer (second electron transfer layer)  770  disposed between the second electrode  230  and the EML2  740 . The second hole transfer layer  750  can have a single-layered structure of a second HTL (HTL2)  754 . In one exemplary aspect, the second hole transfer layer  770  can comprise an EIL  772  and a second ETL (ETL2)  774  each of which is disposed sequentially between the second electrode  230  and the EML2  740 . Alternatively, the second electron transfer layer  770  can have a single-layered structure of the ETL2  774 . Alternatively, the second emitting part  720  can further comprise a second EBL (EBL2) disposed between the EML2  740  and the second hole transfer layer  750  and/or a second HBL (HBL2) disposed between the EML2  740  and the second electron transfer layer  770 . 
     The CGL  680  is disposed between the first emitting part  620  and the second emitting part  720 . The first emitting part  620  and the second emitting part  720  are connected via the CGL  680 . The CGL  680  can be a PN-junction CGL that junctions an N-type CGL (N-CGL)  682  with a P-type CGL (P-CGL)  684 . 
     The N-CGL  682  is disposed between the first electron transfer layer  670  and the second hole transfer layer  750  and the P-CGL  684  is disposed between the N-CGL  682  and the second hole transfer layer  750 . The N-CGL  682  transports electrons to the EML1  640  of the first emitting part  620  and the P-CGL  684  transport holes to the EML2  740  of the second emitting part  720 . 
     The N-CGL  682  can include N-type host and N-type dopant. The N-type host can comprise an alkali metal or an alkaline earth metal such as Li, Mg and Cs and/or alkali metal compound or alkaline earth compound such as CsCO 3  and CsN 3 . The N-type dopant can comprise an organic compound such as BCP, Alq 3 , and Bphen. For example, the N-CGL  682  can comprise, but is not limited to, Cs:BCP, Mg:Alq 3 , CsCO 3 :Alq 3 , Cs:Bphen, CsN 3 :Bphen. 
     The P-CGL  684  can comprise metal oxide such as ITO,  V2O5 , WO 3  and MoO 3 . Alternatively, the P-CGL  684  can comprise P-type host and P-type dopant. For example, the P-CGL  384  can comprise, but is not limited to, FeCl 3 :NPB and tetrfluorotetracyanoquinodimethane (F4-TCNQ):NPB. 
     In one exemplary aspect, each of the EML1  640  and the EML2  740  can be a red emitting material layer. The inorganic luminescent particles  300  ( FIG. 3 ) in the EML1  640  and the EML2  740  as the red emitting material layer can independently comprise, but is not limited to, InP/ZnSe, InP/ZnSeS, InP/ZnS, InP/ZnSe/ZnS, InP/ZnSeS/ZnS, CuInS/ZnSe, CuInS/ZnSeS, CuInS/ZnS, CuInS/ZnSe/ZnS and CuInS/ZnSeS/ZnS. 
     In another exemplary aspect, each of the EML1  640  and the EML2  740  can be a green emitting material layer. The inorganic luminescent particles  300  ( FIG. 3 ) in the EML1  640  and the EML2  740  as the green emitting material layer can independently comprise, but is not limited to, InP/ZnSe, InP/ZnSeS, InP/ZnS, InP/ZnSe/ZnS, InP/ZnSeS/ZnS, CuInS/ZnSe, CuInS/ZnSeS, CuInS/ZnS, CuInS/ZnSe/ZnS and CuInS/ZnSeS/ZnS. 
     In still another exemplary aspect, each of the EML1  640  and the EML2  740  can be a blue emitting material layer. The inorganic luminescent particles  300  ( FIG. 3 ) in the EMIL  1640  and the EML2  740  as the blue emitting material layer can independently comprise, but is not limited to, ZnSe/ZnS and ZnSeTe/ZnS. 
     In this case, the inorganic luminescent particles in the EML1  640  can be identical to or different from the inorganic luminescent particles in the EML2  740 . The EML2  740  can emit different color or have different luminous efficiency from the EML1  640  by making the inorganic luminescent particles in the EML1  640  different from the inorganic luminescent particles in the EML2  740 . 
     In the inorganic LED D3, each of the EML  640  and the EML2  740  includes a siloxane matrix  400  ( FIG. 3 ) whose thickness is equal to or less than the thickness of layer of the inorganic luminescent particle  300  so that the inorganic LED D3 can lower its driving voltage and improve its luminous efficiency. In addition, since the inorganic LED D3 has a double stack structure of blue, green or red emitting material layer, the inorganic LED D3 improve its color sense or optimize its luminous efficiency. 
       FIG. 6  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with another exemplary aspect of the present disclosure. As illustrated in  FIG. 6 , an inorganic light emitting display device  800  includes a substrate  810  that defines first to third pixel regions P1, P2 and P3, a thin film transistor Tr disposed over the substrate  810  and an inorganic LED D disposed over the thin film transistor Tr and connected to the thin film transistor Tr. As an example, the first pixel region P1 can be a blue pixel region, the second piex region P2 can be a green pixel region and the third pixel region P3 can be a red pixel region. 
     The substrate  810  can be a glass substrate or a flexible substrate. For example, the flexible substrate can be any one of a PI substrate, a PES substrate, a PEN substrate, a PET substrate and a PC substrate. 
     A buffer layer  812  is disposed over the substrate  810  and the thin film transistor Tr is disposed over the buffer layer  812 . The buffer layer  812  can be omitted. As illustrated in  FIG. 1 , the thin film transistor Tr includes a semiconductor layer, a gate electrode, a source electrode and a drain electrode and acts as a driving element. 
     A passivation layer  850  is disposed over the thin film transistor Tr. The passivation layer  850  has a flat top surface and a drain contact hole  852  that exposes a drain electrode of the thin film transistor Tr. 
     The inorganic LED D is disposed over the passivation layer  850 , and includes a first electrode  910  that is connected to the drain electrode of the thin film transistor Tr, and an emissive layer  920  and a second electrode  930  each of which is disposed sequentially on the first electrode  910 . The inorganic LED D is disposed in each of the first to third pixel regions P1, P2 and P3 and emits different light in each pixel region. For example, the inorganic LED D in the first pixel region P1 can emit blue light, the inorganic LED D in the second pixel region P2 can emit green light and the inorganic LED D in the third pixel region P3 can emit red light. 
     The first electrode  910  is separately formed for each of the first to third pixel regions P1, P2 and P3, and the second electrode  930  corresponds to the first to third pixel regions P1, P2 and P3 and is formed integrally. 
     The first electrode  910  can be one of an anode and a cathode, and the second electrode  930  can be the other of the anode and the cathode. In addition, one of the first electrode  910  and the second electrode  930  is a transmissive (or semi-transmissive) electrode and the other of the first electrode  910  and the second electrode  930  is a reflective electrode. 
     For example, the first electrode  910  can be an anode and can include conductive material having a relatively high work function value, i.e., a transparent conductive oxide layer of transparent conductive oxide (TCO). The second electrode  930  can be a cathode and can include conductive material having relatively low work function value, i.e., a metal material layer of low-resistant metal. For example, the first electrode  910  can include undoped or doped metal oxide including ITO, IZO, ITZO, ICO, SnO 2 , In 2 O 3 , Cd:ZnO, F;SnO 2 , In:SnO 2 , Ga:SnO 2  and AZO. Alternatively, the first electrode  910  can comprise Ni, Pt, Au, Ag, Ir and CNT in addition to the metal oxides. The second electrode  930  can include Al, Mg, Ca, Ag, alloy thereof (ex. Mg—Al) or combination thereof. 
     When the inorganic light emitting display device  800  is a bottom-emission type, the first electrode  910  can have a single-layered structure of a transparent conductive oxide layer. 
     Alternatively, when the inorganic light emitting display device  800  is a top-emission type, a reflective electrode or a reflective layer can be disposed under the first electrode  910 . For example, the reflective electrode or the reflective layer can include, but is not limited to, Ag or APC alloy. In the inorganic LED D of the top-emission type, the first electrode  910  can have a triple-layered structure of ITO/Ag/ITO or ITO/APC/ITO. Also, the second electrode  930  is thin so as to have light-transmissive (or semi-transmissive) property. 
     A bank layer  860  is disposed over the passivation layer  850  in order to cover edges of the first electrode  910 . The bank layer  860  corresponds to each of the first to third pixel regions P1, P2 and P3 and exposes a center of the first electrode  910 . 
     An emissive layer  920  is disposed on the first electrode  910 . In one exemplary aspect, the emissive layer  920  can have a single-layered structure of an EML. Alternatively, the emissive layer  920  can include at least one charge transfer layer. For example, the emissive layer  920  can further comprise at least one of a first charge transfer layer disposed between the first electrode  910  and the EML and a second charge transfer layer disposed between the second electrode  930  and the EML. Alternatively, the emissive layer can further comprise at least on exciton blocking layer  265  or  275  ( FIG. 4 ). 
     In one exemplary aspect, the EML in the first pixel region P1 as the blue pixel region can comprise blue inorganic luminescent particles, the EML in the second pixel region P2 as the green pixel region can comprise green inorganic luminescent particles and the EML in the second pixel region P3 as the red pixel region can comprise red inorganic luminescent particles. 
     An encapsulation film  870  is disposed over the second electrode  930  in order to prevent outer moisture from penetrating into the inorganic LED D. The encapsulation film  870  can have, but is not limited to, a triple-layered structure of a first inorganic insulating film, an organic insulating film and a second inorganic insulating film. 
     Moreover, the inorganic light emitting display device  800  can have a polarizer in order to decrease external light reflection. For example, the polarizer can be a circular polarizer. When the inorganic light emitting display device  800  is a bottom-emission type, the polarizer can be disposed under the substrate  810 . Alternatively, when the inorganic light emitting display device  800  is a top emission type, the polarizer can be disposed over the encapsulation film  870 . 
       FIG. 7  is a schematic cross-sectional view illustrating an inorganic LED in accordance with still another exemplary aspect of the present disclosure. As illustrated in  FIG. 7 , the inorganic LED D4 comprises a first electrode  910 , a second electrode  930  facing the first electrode  910  and an emissive layer  920  disposed between the first and second electrodes  910  and  930 . 
     The first electrode  910  can be an anode and the second electrode  930  can be a cathode. As an example, the first electrode  910  can be a reflective electrode and the second electrode  930  can be a transmissive (or semi-transmissive) electrode. 
     The emissive layer  920  comprises an EML  940 . The emissive layer  930  can comprise at least one of a first charge transfer layer (hole transfer layer)  950  disposed between the first electrode  910  and the EML  940  and a second charge transfer layer (electron transfer layer)  970  disposed between the second electrode  930  and the EML  940 . 
     In one exemplary aspect, the first charge transfer layer  950  can comprise a HIL  952  disposed between the first electrode  910  and the EML  940  and a HTL  954  disposed between the EML  940  and the HIL  952 . Alternatively, the HIL  952  can be omitted. 
     In one exemplary aspect, the second charge transfer layer  970  can comprise an EIL  972  disposed between the second electrode  930  and the EML  940  and an ETL  974  disposed between the EML  940  and the EIL  972 . Alternatively, the EIL  972  can be omitted. 
     In addition, the first charge transfer layer  940  can further comprise an auxiliary hole transport layer (auxiliary HTL)  956  disposed between the EML  940  and the HTL  954 . The auxiliary HTL  956  can comprise a first auxiliary HTL  956   a  located in the first pixel region P1, a second auxiliary HTL  956   b  located in the second pixel region P2 and a third auxiliary HTL  956   c  located in the third pixel region P3. 
     The first auxiliary HTL  956   a  has a first thickness, the second auxiliary HTL  956   b  has a second thickness and the third auxiliary HTL  956   c  has a third thickness. The first thickness is less than the second thickness, and the second thickness is less than the third thickness. Accordingly, the inorganic LED D4 has a micro-cavity structure. 
     Owing to the first to third auxiliary HTLs  956   a ,  956   b  and  956   c  having different thickness to each other, the distance between the first electrode  910  and the second electrode  930  in the first pixel region P1 emitting light in the first wavelength range (blue light) is less than the distance between the first electrode  910  and the second electrode  930  in the second pixel region P2 emitting light in the second wavelength (green light). In addition, the distance between the first electrode  910  and the second electrode  930  in the second pixel region P2 emitting light in the second wavelength is less than the distance between the first electrode  910  and the second electrode  930  in the third pixel region P3 emitting light in the third wavelength range (red light). Accordingly, the inorganic LED D3 has improved luminous efficiency. 
     In  FIG. 7 , the first auxiliary HTL  956   a  is located in the first pixel region P1. Alternatively, the inorganic LED D4 can implement the micro-cavity structure without the first auxiliary HTL  956   a . In addition, a capping layer can be disposed over the second electrode in order to improve out-coupling of the light emitted from the inorganic LED D4. 
     The EML  940  comprises a first EML (EML1)  942  located in the first pixel region P1, a second EML (EML2)  944  located in the second pixel region P2 and a third EML (EML3)  946  located in the third pixel region P3. Each of the EML1  942 , the EML2  944  and the EML3  946  can be a blue EML, a green EML and a red EML, respectively. The EML1  942  can comprise blue inorganic luminescent particles, the EML2  944  can comprise green inorganic luminescent particles and the EML3  946  can comprise red inorganic luminescent particles. 
     The inorganic LED D4 emits blue light, green light and red light in each of the first to third pixel regions P1, P2 and P3 so that the inorganic light emitting display device  800  ( FIG. 6 ) can implement a full-color image. 
     The inorganic light emitting display device  800  can further comprise a color filter layer corresponding to the first to third pixel regions P1, P2 and P3 for improving color purity of the light emitted from the inorganic LED D. As an example, the color filter layer can comprise a first color filter layer (blue color filter layer) corresponding to the first pixel region P1, the second color filter layer (green color filter layer) corresponding to the second pixel region P2 and the third color filter layer (red color filter layer) corresponding to the third pixel region P3. 
     When the inorganic light emitting display device  800  is a bottom-emission type, the color filter layer can be disposed between the inorganic LED D and the substrate  810 . Alternatively, when the inorganic light emitting display device  800  is a top-emission type, the color filter layer can be disposed over the inorganic LED D. 
       FIG. 8  is a schematic cross-sectional view illustrating an inorganic light emitting display device in accordance with still another exemplary aspect of the present disclosure. As illustrated in  FIG. 8 , the inorganic light emitting display device  1000  comprise a substrate  1010  defining a first pixel region P1, a second pixel region P2 and a third pixel region P3, a thin film transistor Tr disposed over the substrate  1010 , an inorganic LED D disposed over the thin film transistor Tr and connected to the thin film transistor Tr and a color filter layer  1020  corresponding to the first to third pixel regions P1, P2 and P3. As an example, the first pixel region P1 can be a blue pixel region, the second pixel region P2 can be a green pixel region and the third pixel region P3 can be a red pixel region. 
     The substrate  1010  can be a glass substrate or a flexible substrate. For example, the flexible substrate can be any one of a PI substrate, a PES substrate, a PEN substrate, a PET substrate and a PC substrate. The thin film transistor Tr is located over the substrate  1010 . Alternatively, a buffer layer can be disposed over the substrate  1010  and the thin film transistor Tr can be disposed over the buffer layer. As illustrated in  FIG. 1 , the thin film transistor Tr includes a semiconductor layer, a gate electrode, a source electrode and a drain electrode and acts as a driving element. 
     The color filter layer  1020  is located over the substrate  1010 . As an example, the color filter layer  1020  can comprise a first color filter layer  1022  corresponding to the first pixel region P1, a second color filter layer  1024  corresponding to the second pixel region P2 and a third color filter layer  1026  corresponding to the third pixel region P3. The first color filter layer  1022  can be a blue color filter layer, the second color filter layer  1024  can be a green color filter layer and the third color filter layer  1026  can be a red color filter layer. For example, the first color filter layer  1022  can comprise at least one of blue dye or blue pigment, the second color filter layer  1024  can comprise at least one of green dye or green pigment and the third color filter layer  1026  can comprise at least one of red dye or red pigment. 
     A passivation layer  1050  is disposed over the thin film transistor Tr and the color filter layer  1020 . The passivation layer  1050  has a flat top surface and a drain contact hole  1052  that exposes a drain electrode of the thin film transistor Tr. 
     The inorganic LED D is disposed over the passivation layer  1050  and corresponds to the color filter layer  1020 . The inorganic LED D includes a first electrode  1110  that is connected to the drain electrode of the thin film transistor Tr, and an emissive layer  1120  and a second electrode  1130  each of which is disposed sequentially on the first electrode  1110 . The inorganic LED D emits white light in the first to third pixel regions P1, P2 and P3. 
     The first electrode  1110  is separately formed for each of the first to third pixel regions P1, P2 and P3, and the second electrode  1130  corresponds to the first to third pixel regions P1, P2 and P3 and is formed integrally. 
     The first electrode  1110  can be one of an anode and a cathode, and the second electrode  1130  can be the other of the anode and the cathode. In addition, the first electrode  1110  can be a transmissive (or semi-transmissive) electrode and the second electrode  1130  can be a reflective electrode. 
     For example, the first electrode  1110  can be an anode and can include conductive material having a relatively high work function value, i.e., a transparent conductive oxide layer of transparent conductive oxide (TCO). The second electrode  1130  can be a cathode and can include conductive material having relatively low work function value, i.e., a metal material layer of low-resistant metal. For example, the transparent conductive oxide layer of the first electrode  1110  can include undoped or doped metal oxide including ITO, IZO, ITZO, ICO, SnO 2 , In 2 O 3 , Cd:ZnO, F;SnO 2 , In:SnO 2 , Ga:SnO 2  and AZO. Alternatively, the first electrode  910  can comprise Ni, Pt, Au, Ag, Ir and CNT in addition to the metal oxides. The second electrode  930  can include Al, Mg, Ca, Ag, alloy thereof (ex. Mg—Al) or combination thereof. 
     The emissive layer  1120  is disposed on the first electrode  1110 . The emissive layer  1120  includes at least two emitting parts emitting different colors. Each of the emitting part can have a single-layered structure of an EML. Alternatively, each of the emitting parts can include at least one of a hole transfer layer and an electron transfer layer, and optionally at least one exciton blocking layer. In addition, the emissive layer  1120  can further comprise a CGL disposed between the emitting parts. 
     At least one of the at least two emitting parts can be a blue EML and the other of the at least two emitting parts can be an EML emitting light whose wavelength is longer than the blue light. 
     A bank layer  1060  is disposed on passivation layer  1050  in order to cover edges of the first electrode  1110 . The bank layer  1060  corresponds to each of the first to third pixel regions P1, P2 and P3 and exposes a center of the first electrode  1110 . As described above, since the inorganic LED D emits white light in the first to third pixel regions P1, P2 and P3, the emissive layer  1120  can be formed as a common layer without being separated in the first to third pixel regions P1, P2 and P3. The bank layer  1060  is formed to prevent current leakage from the edges of the first electrode  1110 , and the bank layer  1060  can be omitted. 
     Moreover, the inorganic light emitting display device  1000  can further comprise an encapsulation film disposed on the second electrode  1130  in order to prevent outer moisture from penetrating into the OLED D. In addition, the organic light emitting display device  1000  can further comprise a polarizer disposed under the substrate  1010  in order to decrease external light reflection. 
     In the inorganic light emitting display device  1000  in  FIG. 8 , the first electrode  1110  is a transmissive electrode, the second electrode  1130  is a reflective electrode, and the color filter layer  1020  is disposed between the substrate  1010  and the inorganic LED D. That is, the inorganic light emitting display device  1000  is a bottom-emission type. Alternatively, the first electrode  1110  can be a reflective electrode, the second electrode  1120  can be a transmissive electrode (or semi-transmissive electrode) and the color filter layer  1020  can be disposed over the inorganic LED D in the organic light emitting display device  1000 . 
     In the inorganic light emitting display device  1000 , the inorganic LED D located in the first to third pixel regions P1, P2 and P3 emits white light, and the white light passes through each of the first to third pixel regions P1, P2 and P3 so that each of a blue color, a green color and a red color is displayed in the first to third pixel regions P1, P2 and P3, respectively. 
     A color conversion film can be disposed between the inorganic LED D and the color filter layer  1020 . The color conversion film corresponds to the first to third pixel regions P1, P2 and P3, and comprises a blue color conversion film, a green color conversion film and a red color conversion film each of which can convert the white light emitted from the inorganic LED D into blue light, green light and red light, respectively. For example, the color conversion film can comprise quantum dots. Accordingly, the organic light emitting display device  1000  can further enhance its color purity. Alternatively, the color conversion film can displace the color filter layer  1020 . 
       FIG. 9  is a schematic cross-sectional view illustrating an inorganic LED in accordance with still another exemplary aspect of the present disclosure. As illustrated in  FIG. 9 , the inorganic LED D5 comprises first and second electrodes  1110  and  1120  facing each other and an emissive layer  1120  disposed between the first and second electrodes  1110  and  1120 . The first electrode  1110  can be an anode and the second electrode  1120  can be a cathode. For example, the first electrode  1100  can be a transmissive electrode and the second electrode  1120  can be a reflective electrode. 
     The emissive layer  1120  includes a first emitting part  1220  comprising a first EML (EML1)  1240 , a second emitting part  1320  comprising a second EML (EML2)  1340  and a third emitting part  1420  comprising a third EML (EML3)  1440 . In addition, the emissive layer  1120  can further comprise a first charge generation layer (CGL1)  1280  disposed between the first emitting part  1220  and the second emitting part  1320  and a second charge generation layer (CGL2)  1380  disposed between the second emitting part  1320  and the third emitting part  1420 . Accordingly, the first emitting part  1220 , the CGL1  1280 , the second emitting part  1320 , the CGL2  1380  and the third emitting part  1420  are disposed sequentially on the first electrode  1110 . 
     The first emitting part  1220  comprise the EML1  1240 . The first emitting part  1220  can further comprise at least one of a lower first charge transfer layer (first hole transfer layer)  1250  disposed between the first electrode  1110  and the EML1  1240  and a lower second charge transfer layer (first electron transfer layer)  1270  disposed between the EML1  1240  and the CGL1  1280 . In one exemplary aspect, the lower first charge transfer layer  1250  can comprise a HIL  1252  disposed between the first electrode  1110  and the EML1  1240  and a HTL1  1254  disposed between the EML1  1240  and the HIL  1252 . Alternatively, the first hole transfer layer  1250  can have a single-layered structure of the HTL 1  1254 . The first electron transfer layer  1270  can have a single-layered structure of an ETL 1  1274 . Alternatively, the first emitting part  1220  can further comprise an EBL1 disposed between the EML1  1240  and the first hole transfer layer  1250  and/or a HBL1 disposed between the EML1  1240  and the first electron transfer layer  1270 . 
     The second emitting part  1320  comprises the EML2  1340 . The second emitting part  1320  can comprise at least one of a middle first charge transfer layer (second hole transfer layer)  1350  disposed between the CGL1  1280  and the EML2  1340  and a middle second charge transfer layer (second electron transfer layer)  1370  disposed between the EML2  1340  and the CGL2  1380 . As an example, the second hole transfer layer  1350  can have a single-layered structure of a HTL2  1354 . The second electron transfer layer  1370  can have a single-layered structure of an ETL2  1374 . Alternatively, the second emitting part  1320  can further comprise an EBL2 disposed between the EML2  1340  and the second hole transfer layer  1350  and/or a HBL2 disposed between the EML2  1340  and the second electron transfer layer  1370 . 
     The third emitting part  1420  comprises the EML3  1440 . The third emitting part  1420  can comprise at least one of an upper first charge transfer layer (third hole transfer layer)  1450  disposed between the CGL2  1380  and the EML3  1440  and an upper second charge transfer layer (third electron transfer layer)  1470  disposed between the second electrode  1130  and the EML3  1440 . The third hole transfer layer  1450  can have a single-layered structure of a third HTL (HTL3)  1454 . In one exemplary aspect, the third electron transfer layer  1470  can comprise an EIL  1472  and a third ETL (ETL3)  1474  each of which is disposed sequentially between the second electrode  1130  and the EML3  1440 . Alternatively, the third electron transfer layer  1470  can have a single-layered structure of the ETL3  1474 . Alternatively, the third emitting part  1420  can further comprise a third EBL (EBL3) disposed between the EML3  1440  and the third hole transfer layer  1450  and/or a third HBL (HBL3) disposed between the EML3  1440  and the third electron transfer layer  1470 . 
     The CGL1  1280  is disposed between the first emitting part  1220  and the second emitting part  1320 . That is, the first emitting part  1220  and the second emitting part  1320  are connected via the CGL1  1280 . The CGL1  1280  can be a PN-junction CGL that junctions a first N-type CGL (N-CGL1)  1282  with a first P-type CGL (P-CGL1)  1284 . 
     The N-CGL1  1282  is disposed between the first electron transfer layer  1270  and the second hole transfer layer  1350  and the P-CGL1  1284  is disposed between the N-CGL1  1282  and the second hole transfer layer  1450 . The N-CGL1  1282  transports electrons to the EML1  1240  of the first emitting part  1220  and the P-CGL1  1284  transport holes to the EML2  1340  of the second emitting part  1320 . 
     The CGL2  1380  is disposed between the second emitting part  1320  and the third emitting part  1420 . That is, the second emitting part  1320  and the third emitting part  1420  are connected via the CGL2  1380 . The CGL2  1380  can be a PN-junction CGL that junctions a second N-type CGL (N-CGL2)  1382  with a second P-type CGL (P-CGL2)  1384 . 
     The N-CGL2  1382  is disposed between the second electron transfer layer  370  and the third hole transfer layer  1450  and the P-CGL2  1384  is disposed between the N-CGL2  1382  and the third hole transfer layer  1450 . The N-CGL2  1382  transports electrons to the EML2  1340  of the second emitting part  1320  and the P-CGL2  1384  transport holes to the EML3  1440  of the third emitting part  1420 . 
     In this aspect, one of the first to third EMLs  1240 ,  1340  and  1440  can be a blue EML, another of the first to third EMLs  1240 ,  1340  and  1440  can be a green EML and the third of the first to third EMLs  1240 ,  1340  and  1440  can be a red EML. 
     As an example, the EML1  1240  can be a blue EML, the EML2  1340  can be a green EML and the EML3  1440  can be a red EML. Alternatively, the EML1  1240  can be a red EML, the EML2  1340  can be a green EML and the EML3  1440  can be a blue EML1. Hereinafter, the OLED D5 where the EML1  1240  is a blue EML, the EML2  1340  is a green EML and the EML3  1440  is a red EML will be described. 
     The EML1  1240  can comprise blue inorganic luminescent particles. The blue inorganic luminescent particles can comprise, but is not limited to, ZnSe/ZnS and ZnSeTe/ZnS. The EML2  1340  can comprise green inorganic luminescent particles. The green inorganic luminescent particles can comprise, but is not limited to, InP/ZnSe, InP/ZnSeS, InP/ZnS, InP/ZnSe/ZnS, InP/ZnSeS/ZnS, CuInS/ZnSe, CuInS/ZnSeS, CuInS/ZnS, CuInS/ZnSe/ZnS and CuInS/ZnSeS/ZnS. The EML3  1440  can comprise red inorganic luminescent particles. The red inorganic luminescent particles can comprise, but is not limited to, InP/ZnSe, InP/ZnSeS, InP/ZnS, InP/ZnSe/ZnS, InP/ZnSeS/ZnS, CuInS/ZnSe, CuInS/ZnSeS, CuInS/ZnS, CuInS/ZnSe/ZnS and CuInS/ZnSeS/ZnS. 
     The inorganic LED D5 emits white light in each of the first to third pixel regions P1, P2 and P3 and the white light passes though the color filter layer  1020  ( FIG. 8 ) correspondingly disposed in the first to third pixel regions P1, P2 and P3. Accordingly, the inorganic light emitting display device  1000  ( FIG. 8 ) can implement a full-color image. 
       FIG. 10  is a schematic cross-sectional view illustrating an inorganic LED in accordance with still another exemplary aspect of the present disclosure. As illustrated in  FIG. 10 , the inorganic LED D6 comprises first and second electrodes  1110  and  1120  facing each other and an emissive layer  1120 A disposed between the first and second electrodes  1110  and  1120 . The first electrode  1110  can be an anode and the second electrode  1120  can be a cathode. For example, the first electrode  1100  can be a transmissive electrode and the second electrode  1120  can be a reflective electrode. 
     The emissive layer  1120 A includes a first emitting part  1520  comprising a first EML (EML1)  1540 , a second emitting part  1620  comprising a second EML (EML2)  1640  and a third emitting part  1720  comprising a third EML (EML3)  1740 . In addition, the emissive layer  1120 A can further comprise a CGL1  1580  disposed between the first emitting part  1520  and the second emitting part  1620  and a CGL2  1680  disposed between the second emitting part  1620  and the third emitting part  1720 . Accordingly, the first emitting part  1520 , the CGL1  1580 , the second emitting part  1620 , the CGL2  1680  and the third emitting part  1720  are disposed sequentially on the first electrode  1110 . 
     The first emitting part  1520  comprise the EML1  1540 . The first emitting part  1520  can further comprise at least one of a lower first charge transfer layer (first hole transfer layer)  1550  disposed between the first electrode  1110  and the EML1  1540  and a lower second charge transfer layer (first electron transfer layer)  1570  disposed between the EML1  1540  and the CGL1  1580 . In one exemplary aspect, the first hole transfer layer  1550  can comprise a HIL  1552  disposed between the first electrode  1110  and the EML1  1540  and a HTL1  1554  disposed between the EML1  1540  and the HIL  1552 . Alternatively, the first hole transfer layer  1550  can have a single-layered structure of the HTL1  1554 . The first electron transfer layer  1570  can have a single-layered structure of an ETL 1  1574 . Alternatively, the first emitting part  1520  can further comprise an EBL1 disposed between the EML1  1540  and the first hole transfer layer  1550  and/or HBL1 disposed between the EML1  1540  and the first electron transfer layer  1570 . 
     The second emitting part  1620  comprises the EML2  1640 . The EML2  1640  comprise a lower EML  1642  and an upper EML  1644 . The lower EML  1642  is disposed adjacently to the first electrode  1110  and the upper EML  1644  is disposed adjacently to the second electrode  1130 . The second emitting part  1620  can comprise at least one of a middle first charge transfer layer (second hole transfer layer)  1650  disposed between the CGL1  1580  and the EML2  1640  and a middle second charge transfer layer (second electron transfer layer)  1570  disposed between the EML2  1640  and the CGL2  1680 . As an example, the second hole transfer layer  1650  can have a single-layered structure of a HTL2  1654 . The second electron transfer layer  1670  can have a single-layered structure of an ETL2  1674 . Alternatively, the second emitting part  1620  can further comprise an EBL2 disposed between the EML2  1640  and the second hole transfer layer  1650  and/or a HBL2 disposed between the EML2  1640  and the second electron transfer layer  1670 . 
     The third emitting part  1720  comprises the EML3  1740 . The third emitting part  1720  can comprise at least one of an upper first charge transfer layer (third hole transfer layer)  1750  disposed between the CGL2  1680  and the EML3  1740  and an upper second charge transfer layer (third electron transfer layer)  1770  disposed between the second electrode  1130  and the EML3  1740 . The third hole transfer layer  1750  can have a single-layered structure of a HTL3  1754 . In one exemplary aspect, the third electron transfer layer  1770  can comprise an EIL  1772  and an ETL3  1774  each of which is disposed sequentially between the second electrode  1130  and the EML3  1740 . Alternatively, the third electron transfer layer  1770  can have a single-layered structure of the ETL3  1774 . Alternatively, the third emitting part  1720  can further comprise an EBL3 disposed between the EML3  1740  and the third hole transfer layer  1750  and/or a HBL3 disposed between the EML3  1740  and the third electron transfer layer  1770 . 
     The CGL1  1680  is disposed between the first emitting part  1520  and the second emitting part  1620 . That is, the first emitting part  1520  and the second emitting part  1620  are connected via the CGL1  1580 . The CGL1  1580  can be a PN-junction CGL that junctions an N-CGL1  1582  with a P-CGL1  1584 . The N-CGL1  1582  is disposed between the first electron transfer layer  1570  and the second hole transfer layer  1650  and the P-CGL1  1584  is disposed between the N-CGL1  1582  and the second hole transfer layer  1650 . 
     The CGL2  1680  is disposed between the second emitting part  1620  and the third emitting part  1720 . That is, the second emitting part  1620  and the third emitting part  1720  are connected via the CGL2  1680 . The CGL2  1680  can be a PN-junction CGL that junctions an N-CGL2  1682  with a P-CGL2  1684 . The N-CGL2  1682  is disposed between the second electron transfer layer  1670  and the third hole transfer layer  1750  and the P-CGL2  1684  is disposed between the N-CGL2  1682  and the third hole transfer layer  1750 . 
     In this aspect, each of the EML1  1540  and the EML3  1740  can be a blue EML, respectively. In one exemplary aspect, each of the EML1  1540  and the EML3  1740  can comprise blue inorganic luminescent particles. The blue inorganic luminescent particles in the EML1  1540  can be identical to or different from the blue inorganic luminescent particles in the EML3  1740 . The EML3  1740  can emit different color or have different luminous efficiency from the EML1  1540  by making the inorganic luminescent particles in the EML 1  1540  different from the inorganic luminescent particles in the EML3  1740 . 
     One of the lower EML  1642  and the upper EML  1644  in the EML2  1640  can be a green EML and the other of the lower EML  1642  and the upper EML  1644  in the EML2  1640  can be a red EML. The green EML and the red EML is sequentially disposed to form the EML2  1640 . 
     In one exemplary aspect, the lower EML  1642  as the green EML can comprise green inorganic luminescent particles and the upper EML  1644  as the red EML can comprise red inorganic luminescent particles. 
     Alternatively, the EML2  1640  can have a single-layered structure to emit yellow light. In this case, the size of the green inorganic luminescent particles and the/or the red inorganic luminescent particles are adjusted so that the EML2  1640  can emit yellow wavelength light. 
     The OLED D6 emits white light in each of the first to third pixel regions P1, P2 and P3 and the white light passes though the color filter layer  1020  ( FIG. 8 ) correspondingly disposed in the first to third pixel regions P1, P2 and P3. Accordingly, the inorganic light emitting display device  1000  ( FIG. 8 ) can implement a full-color image. 
     In  FIG. 10 , the OLED D6 has a three-stack structure including the first to three emitting parts  1520 ,  1620  and  1720  which includes the EML1  1540  and the EML3  1740  as a blue EML. Alternatively, the OLED D6 can have a two-stack structure where one of the first emitting part  1520  and the third emitting part  1720  each of which includes the EML1  1540  and the EML3  1740  as a blue EML is omitted. 
     Example 1 (Ex. 1): Fabrication of QLED 
     A quantum light emitting diode (QLED) in which red quantum dots (InP/ZnSe/ZnS; average size 10 nm) are tetraethyl silicate (TEOS) matrix as a siloxane material was fabricated. The red quantum dots (6 mg/mL) and TEOS mixed with a volume ratio of 1:0.1 were dispersed in octane in a Glove box. 
     An ITO (50 nm)-glass was patterned to have luminous area 3 mm×3 mm and washed. And an emissive layer and cathode were laminated as the following order: 
     A HIL (PEDOT:PSS, spin coating (5000 rpm, 60 second) in water base, and heating (200° C., 15 minutes), 20 nm); a HTL (PVK (4 mg/IL in toluene), spin coating (3000 rpm, 60 seconds) and heating (230° C., 30 minutes), 20 nm); an EML (red QD InP/ZnSe/ZnS having oleic acid ligand (6 mg/mL): TEOS=1:0.1 by volume ratio in octane, spin coating (3000 rpm), 10 nm); an ETL (pyridine-based ETL material ET-048, the substrate was mounted to a deposition chamber, condensed at 102 base pressure for 12 second, and deposited under 102 torr of base pressure in a deposition chamber, 54 nm); an EIL (LiF, 1.2 nm); and cathode (Al, deposited in a metal chamber, 80-100 nm). 
     After a capping layer (CPL) was deposited on the cathode, the QLED was encapsulated with glass. And then, the QLED was transferred to a dry box for film formation, followed by encapsulation using UV-curable epoxy and moisture getter. 
     Example 2 (Ex. 2): Fabrication of QLED 
     A QLED was fabricated using the same materials as Example 1, except modifying the volume ratio of the red quantum dots and TEOS to 1:1 in the EML. 
     Comparative Example 1 (Ref 1): Fabrication of QLED 
     A QLED was fabricated using the same materials as Example 1, except modifying the volume ratio of the red quantum dots and TEOS to 1:5. 
     Comparative Example 2 (Ref 2): Fabrication of QLED 
     A QLED was fabricated using the same materials as Example 1, except forming the EML with only the red quantum dots without mixing TEOS. 
     Experimental Example 1: Analysis of Structural Shape of QLED 
     Structural shapes of the QLED fabricated in Ex. 2 and Ref 2 were analyzed using TEM.  FIG. 5  is a TEM image illustrating a cross-section of an inorganic LED fabricated in Ex. 2.  FIGS. 6A and 6B  are TEM images illustrating a top or a cross-sectional of an inorganic LED fabricated in Ref 2. As illustrated in  FIGS. 12A and 12B , as the organic ligand bonded to outer surface of the quantum dots is detached, surface defects are caused, and therefore, voids are formed in the EML with only the quantum dots. On the contrary, as illustrated in  FIG. 5 , when quantum dots are dispersed in or mixed with the siloxane matrix, voids are not formed in the EML as the siloxane matrix protects the quantum dots. 
     Experimental Example 2: STEM-EDS Analysis of QLED 
     STEM-EDS (scanning transmission electron microscopy-energy dispersive X-ray spectroscopy) measurement was performed to analysis elements in the QLEDs fabricated in Ex. 1-2 and Ref. 1. In order to analysis elements in the EML, zinc which is one of the element constituting the outmost shell of the quantum dots and silicon constituting the siloxane matrix were analyzed. 
     As illustrated in  FIGS. 13A to 13C , silicon was observed in a HTL adjacent area of the whole EML in the QLED fabricated in Ex. 1 and siloxane matrix covered about a third of the total thickness of the quantum dot layer in the EML. Also, as illustrated in  FIGS. 14A to 14C , silicon was observed in an area corresponding to the quantum dot layer in the EML fabricated in Ex. 2, i.e., the formed siloxane matrix had the thickness substantially identical to the thickness of the quantum dot layer in the EML. 
     On the other hand, as illustrated in  FIGS. 15A to 15C , silicon was observed to exceed the thickness of the quantum dot layer in the QLED fabricated in Ref. 1, i.e., siloxane matrix was formed over the thickness of the quantum dot layer in the EML. 
     Experimental Example 1: Evaluation of Luminous Properties of QLED 
     Each of the QLED fabricated in Ex. 1 to 2 and Ref. 1 to 2 was connected to an external power source and then luminous properties for all the diodes were evaluated using a constant current source (KEITHLEY) and a photometer PR650 at room temperature. In particular, driving voltage (V), current efficiency (cd/A), power efficiency (lm/W), external quantum efficiency (EQE, %), luminance (cd/m 2 ), color coordinates and at a current density of 10 J (mA/cm 2 ) and voltage-current density of the QLEDs were measured. The results thereof are shown in the following Table 1 and  FIGS. 16 and 17 . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Luminous Property of QLED 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sample 
                 V 
                 cd/A 
                 lm/W 
                 EQE (%) 
                 cd/m 2   
                 (CIEx, CIEy) 
               
               
                   
               
               
                 Ref. 1 
                 6.289 
                 2.050 
                 1.024 
                 2.235 
                 205.0 
                 (0.667, 0.318) 
               
               
                 Ref. 2 
                 3.719 
                 1.139 
                 0.962 
                 1.201 
                 113.9 
                 (0.688, 0.310) 
               
               
                 Ex. 1 
                 4.126 
                 4.698 
                 3.577 
                 4.656 
                 469.8 
                 (0.646, 0.306) 
               
               
                 Ex. 2 
                 4.454 
                 2.223 
                 1.157 
                 2.467 
                 222.3 
                 (0.653, 0.311) 
               
               
                   
               
            
           
         
       
     
     As indicated in Table 1 and  FIG. 17 , compared to the QLED in which the siloxane matrix was formed over the quantum dot layer in Ref. 1, the OLEDs in which the siloxane matrix was formed less than or equal to the quantum dot layer in Ex.1 to 2 lowered their driving voltages up to 34.4% and improved their current efficiency, power efficiency, EQE and luminance up to 128.9%, 249.3%, 108.3% and 129.2%, respectively. Also, compared to the QLED in which the EML consists of only the quantum dot in Ref. 2, the QLEDs in Ex. 1 to 2 improved their current efficiency, power efficiency, EQE and luminance up to 312.5%, 271.8%, 287.7% and 312.5%, respectively. In addition, as illustrated in  FIG. 16 , compared to the QLEDs fabricated in Ref. 1 to 2, the QLEDs fabricated in Ex. 1 to 2 showed much reduced leakage current. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope of the invention. Thus, it is intended that the present disclosure cover the modifications and variations of the present disclosure provided they come within the scope of the appended claims.