Patent Publication Number: US-11653544-B2

Title: Organic light emitting display and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 16/991,721, filed Aug. 12, 2020, which is a continuation of application Ser. No. 16/547,776, filed Aug. 22, 2019, now U.S. Pat. No. 10,804,335, issued Oct. 13, 2020, which is a continuation of application Ser. No. 16/163,839, filed Oct. 18, 2018, now U.S. Pat. No. 10,403,688, issued Sep. 3, 2019, which in turn is a continuation of application Ser. No. 15/661,409, filed Jul. 27, 2017, now U.S. Pat. No. 10,109,685, issued Oct. 23, 2018, which in turn is a continuation of application Ser. No. 14/712,190, filed May 14, 2015, now U.S. Pat. No. 9,722,001, issued Aug. 1, 2017, the entire contents of all being hereby incorporated by reference. 
    
    
     Korean Patent Application No. 10-2014-0175994, filed on Dec. 9, 2014, in the Korean Intellectual Property Office, and entitled: “Organic Light Emitting Display and Manufacturing Method Thereof,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Provided are an organic light emitting display and a manufacturing method thereof. 
     2. Description of the Related Art 
     An organic light emitting display may be used in a small mobile device such as a smart phone in addition to being applied to a large-sized TV with a large screen. 
     SUMMARY 
     Embodiments may be realized by providing an organic light emitting display, including a substrate; a first electrode and a second electrode above the substrate and facing each other; at least two organic light emitting layers between the first electrode and the second electrode; and at least two color filters on the second electrode, the organic light emitting layers emitting a first color light, and the color filters emitting a second color light and a third color light. 
     The first color light may be blue light. 
     The color filters may include a quantum dot material. 
     The color filters may include a first color filter and a second color filter, and the first color filter may emit the second color light, and the second color filter may emit the third color light. 
     The second color light may be green light and the third color light may be red light. 
     Each of the color filters may include a first region adjacent to the second electrode and a second region, and the quantum dot material may be in the second region. 
     The organic light emitting display may further include a charge generating layer between the at least two organic light emitting layers. 
     The charge generating layer may include an n-type charge generating layer and a p-type charge generating layer. 
     The n-type charge generating layer may be adjacent to the first electrode, and the p-type charge generating layer may be adjacent to the second electrode. 
     The first electrode may be an anode, and the second electrode may be a cathode. 
     The organic light emitting layers may include a soluble material. 
     The organic light emitting display may further include an n-type charge generating layer between the second electrode and the light emitting layers. 
     The organic light emitting display may further include a buffer layer between the second electrode and the light emitting layers. The buffer layer may include one or more of WO 3 , MoO x , or hexaazatriphenylenehexacarbonitrile (HATCN). 
     The organic light emitting display may further include a sealing substrate sealing the organic light emitting display. The color filters may be between the sealing substrate and the second electrode. 
     The sealing substrate may include a transparent material, and light emitted from the organic light emitting layers may be emitted through the sealing substrate. 
     Embodiments may be realized by providing a manufacturing method of an organic light emitting display, including forming a first electrode above a substrate; forming at least two organic light emitting layers above the first electrode with a charge generating layer between the organic light emitting layers; and forming a second electrode above the at least two organic light emitting layers, the organic light emitting layers being formed using a soluble material. 
     The manufacturing method may further include one or more of forming one or more of a hole injection layer or a hole transport layer between the first electrode and the organic light emitting layers to supply holes generated from the first electrode to the organic light emitting layers; or forming one or more of an electron injection layer or an electron transport layer between the second electrode and the organic light emitting layers to supply electrons generated from the second electrode to the organic light emitting layers. 
     The organic light emitting layers may be formed under conditions of normal pressure. 
     The manufacturing method may further include forming a buffer layer including one or more of WO 3 , MoO x , or 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN) below the second electrode. 
     The manufacturing method may further include preparing a sealing substrate on which at least two color filters including a quantum dot material are formed; and laminating the substrate and the sealing substrate with the at least two color filters facing the second electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
         FIG.  1    illustrates a schematic cross-sectional view of an organic light emitting display according to an embodiment; 
         FIG.  2    illustrates a schematic cross-sectional view of an organic light emitting display according to an embodiment; 
         FIG.  3    illustrates a schematic cross-sectional view of an organic light emitting display according to an embodiment; 
         FIG.  4    illustrates a schematic cross-sectional view of an organic light emitting display according to an embodiment; 
         FIG.  5    illustrates a schematic cross-sectional view of an organic light emitting display according to an embodiment; and 
         FIG.  6    illustrates a schematic cross-sectional view of an organic light emitting display according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art. 
     In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout. 
     Although the terms “first, second, and so forth” are used to describe diverse constituent elements, such constituent elements are not limited by the terms. The terms are used only to discriminate a constituent element from another constituent element. Accordingly, in the following description, a first constituent element may be a second constituent element. 
     Hereinafter, embodiments will be described with reference to the accompanying drawings. 
       FIG.  1    illustrates a cross-sectional view of an organic light emitting display according to an embodiment. 
     Referring to  FIG.  1   , an organic light emitting display according to an embodiment may include a substrate  50 , a first electrode  100  and a second electrode  200  disposed above the substrate  50  to face, e.g., be separated from, each other, at least two organic light emitting layers  300  and  400  located between the first electrode  100  and the second electrode  200 , and at least two color filters  900  located on the second electrode  200 . The organic light emitting layers  300  and  400  may emit a first color light L 1 , and the color filters  900  may emit a second color light L 2  and a third color light L 3 , respectively. 
     The substrate  50  may include an insulating substrate. If the organic light emitting display is a front emission type display, a semi-transparent or non-transparent substrate may be used as the insulating substrate. 
     The insulating substrate may be made of a material such as glass, quartz, and polymeric resin. Examples of the polymer material may include polyethersulphone (PES), polyacrylate (PA), polyarylate (PAR), polyetherimide (PEI), polyethylene napthalate (PEN), polyethylene terepthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide (PI), polycarbonate (PC), cellulose triacetate (CAT or TAC), cellulose acetate propionate (CAP) and a combination thereof. In some embodiments, the insulating substrate may be a flexible substrate made of a flexible material such as polyimide (PI). 
     Although not shown, the substrate  50  may further include other structures disposed on the insulating substrate. Examples of the other structures may include a wiring, an electrode, and an insulating film. In some embodiments, the substrate  50  may include a plurality of thin film transistors arranged on an insulating substrate. The drain electrodes of some of the thin film transistors may be connected electrically to the first electrode  100 . The thin film transistor may include an active region made of, for example, amorphous silicon, polycrystalline silicon, or single crystalline silicon. In embodiments, the thin film transistor may include an active region containing an oxide semiconductor. 
     The first electrode  100  may be disposed on the substrate  50 , and the first electrode  100  may be disposed in each pixel of the organic light emitting display. The first electrode  100  may be an anode, and the first electrode  100  may include a conductive material that may have a relatively large work function compared to the second electrode  200 . For example, the first electrode  100  may include Indium-Tin-Oxide (ITO), Indium-Zinc-Oxide (IZO), Zinc Oxide (ZnO), or Indium Oxide (In 2 O 3 ). The above-mentioned conductive materials may have a transparent property as well as a relatively large work function. 
     In addition to the above-mentioned conductive materials, a reflective material such as silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), lead (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca) or a mixture thereof may be further included in the first electrode  100 . The first electrode  100  may have a single layer structure formed of the above-mentioned conductive material and reflective material, or may have a multilayer structure formed by stacking plural layers. For example, the first electrode  100  may have a multilayer structure of ITO/Mg, ITO/MgF, ITO/Ag, or ITO/Ag/ITO. 
     The second electrode  200  may be a cathode, and may be a front electrode or common electrode formed regardless of pixels. The second electrode  200  may include a conductive material that may have a relatively low work function compared to the first electrode  100 . 
     The second electrode  200  may include Li, Ca, LiF/Ca, LiF/Al, Al, Mg, Ag, Pt, Pd, Ni, Au Nd, Ir, Cr, BaF, Ba, or a compound or mixture thereof (e.g., a mixture of Ag and Mg). The second electrode  200  may further include an auxiliary electrode. The auxiliary electrode may further include a film formed by depositing the material, and transparent metal oxide, formed on the film, for example, Indium-Tin-Oxide (ITO), Indium-Zinc-Oxide (IZO), Zinc Oxide (ZnO), Indium-Tin-Zinc-Oxide, or MnO 2 . 
     As the second electrode  200 , a conductive layer that may have a small work function may be formed as a thin film, and a transparent conductive film, for example, an Indium-Tin-Oxide (ITO) layer, an Indium-Zinc-Oxide (IZO) layer, a Zinc Oxide (ZnO) layer, or an Indium Oxide (In 2 O 3 ) layer, may be stacked thereon. 
     As described above, the second electrode  200  may be formed of a transparent conductive material, the light generated from the organic light emitting layers  300  and  400  may be emitted forward through the second electrode  200 , and it may be possible to implement a front emission type organic light emitting display. 
     The first color light L 1  may be blue light. For example, the organic light emitting layers  300  and  400  emitting the first color light L 1  may be blue organic light emitting layers. The organic light emitting layers  300  and  400  may include a soluble material, and in a manufacturing process of an organic light emitting display, which will be described later, the organic light emitting layers may be formed by an ink-jet printing method or a discharging method using a slit nozzle without using a deposition method. In the case of the deposition method, the unit price of the product may be increased, for example, due to an expensive deposition apparatus. In the case of forming the organic light emitting layers by using a soluble material, an inexpensive apparatus may be used, and it may be possible to reduce the unit price of the product. 
     By forming at least two organic light emitting layers  300  and  400 , it may be possible to emit a large amount of light. For example, as shown in  FIG.  1   , the organic light emitting layers  300  and  400  may include a first organic light emitting layer  300  and a second organic light emitting layer  400 . Blue light may be emitted from the first organic light emitting layer  300  and the second organic light emitting layer  400 , and it may be possible to increase the luminous efficiency of the organic light emitting display by increasing the amount of light emitted. Illustrated is an embodiment including organic light emitting layers, i.e., the organic light emitting layers  300  and  400 . If a larger amount of light emitted is required, another organic light emitting layer, e.g., a third organic light emitting layer (not shown) or a fourth organic light emitting layer (not shown), may be added, and these layers may be organic light emitting layers that emit blue light. 
     Holes may be provided from the first electrode  100  and electrons may be provided from the second electrode  200 , the provided holes and electrons may be coupled with each other in the organic light emitting layers  300  and  400  located between the first electrode  100  and the second electrode  200 , and light may be generated by the energy generated when exitons formed by the coupling fall to the ground state. 
     The color filters  900  may allow the light provided from the organic light emitting layers  300  and  400  to be emitted as the second color light L 2  or the third color light L 3 . For example, the color filters  900  may convert the first color light L 1  provided from the organic light emitting layers  300  and  400  into the second color light L 2  or the third color light L 3 . 
     The color filters  900  may include a first color filter  910  and a second color filter  950 . The first color filter  910  may emit the second color light L 2 , and the second color filter  950  may emit the third color light L 3 . The second color light L 2  may be green light and the third color light L 3  may be red light. The color filters  910  and  950  may be formed only in some regions of the upper side of the organic light emitting layers  300  and  400 , and may not be formed in some regions of the upper side thereof. For example, as shown in  FIG.  1   , the first color filter  910  and the second color filter  950  may be formed at some positions above the organic light emitting layers  300  and  400 , and the color filters may not be formed at some positions above the organic light emitting layers  300  and  400 . The first color light L 1  that may be blue light may be emitted directly at the position at which the color filter is not formed, and the blue light passing through the first color filter  910  may be converted into the second color light L 2  and emitted as green light. The blue light passing through the second color filter  950  may be converted into the third color light L 3  and emitted as red light. 
     The organic light emitting display may include a sealing substrate  700 , and the sealing substrate  700  may seal (cap) the organic light emitting display while preventing various organic layers constituting the organic light emitting display from being damaged by being exposed to the outside. The sealing substrate  700  may be formed of a transparent material, and the light emitted from the organic light emitting layers  300  and  400  may be emitted through the sealing substrate  700 . As described above, the sealing substrate  700  and the second electrode  200  may be formed of a transparent material, and light may be freely emitted through the front surface of the organic light emitting display. 
     The above-described color filters  900  may be formed on, for example, the sealing substrate  700 , and the color filters  900  may be formed directly on the second electrode  200 . 
     The color filters  900  may include quantum dot materials  10  and  20 . Quantum dots refer to semiconductor nanoparticles that may have a size of several nm to several tens nm, and may have characteristics that emission light varies depending on the size of the particles by a quantum confinement effect. For example, the quantum dots may generate strong light in a narrow wavelength band, and light emitted from the quantum dots may be generated when the electrons in an unstable (excited) state fall from a conduction band to a valence band. The quantum dots may have a property that generates light having a short wavelength as the particles are smaller, and generates light having a long wavelength as the particles are larger. By adjusting the size of the quantum dots, it may be possible to generate light having a desired wavelength in a visible light region. Therefore, it may be possible to obtain light of a desired wavelength by adjusting the size of the quantum dot materials  10  and  20 . 
     The quantum dot materials  10  and  20  may have a particle size of 10 nm or less. For example, the quantum dot materials may emit red light if the particle size ranges from 55 to 65 Å, may emit green light if the particle size ranges from 40 to 50 Å, and may emit blue light if the particle size ranges from 20 to 35 Å. The quantum dot materials may emit yellow light if the particle size is intermediate between those of the quantum dot material emitting red light and the quantum dot material emitting green light. By including the quantum dot materials in the color filters  900 , it may be possible to increase the color purity. 
     The quantum dot materials  10  and  20  may include silicon (Si)-based nano crystals, Group II-VI-based compound semiconductor nano crystals, Group III-V-based compound semiconductor nano crystals, Group IV-VI-based compound semiconductor nano crystals, and mixtures thereof. 
     The Group II-VI-based compound semiconductor nano crystals may be formed of one selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HggZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and HgZnSTe. 
     The Group III-V-based compound semiconductor nano crystals may be formed of one selected from GaPAs, AlNP, AINAs, AlPAs, InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs, InAlNP, InAlNAs, and InAlPAs. 
     The Group IV-VI-based compound semiconductor nano crystals may be formed of SbTe. 
     Each of the color filters  900  may emit desired light, but may emit light having higher purity if the quantum dot materials  10  and  20  are included in the color filters  900  as described above. For example, in the case of the color filters  900  including the first color filter  910  and the second color filter  950 , if the first color filter  910  emits green light and the second color filter  950  emits red light, the first color filter  910  may include the quantum dot material  10  corresponding to the wavelength range of 500 nm to 570 nm, which is a green light wavelength range. The second color filter  950  may include the quantum dot material  20  corresponding to the wavelength range of 600 nm to 670 nm, which is a red light wavelength range. 
     Although not separately shown, an n-type charge generating layer may be further included between the second electrode  200  and the light emitting layers  300  and  400  to impart the conductivity between the second electrode  200  and the light emitting layers  300  and  400 . 
     A buffer layer  600  may be further included between the second electrode  200  and the light emitting layers  300  and  400 . For example, the buffer layer  600  may include one or more of WO 3 , MoO x , or hexaazatriphenylenehexacarbonitrile (HATCN). The second electrode  200  may be formed by a deposition method or a sputtering method by using a material such as an inorganic material. Various kinds of organic layers located therebelow may be damaged, or their functions may be deteriorated. By forming the buffer layer  600 , it may be possible to prevent the deterioration of the functions by the second electrode. If the n-type charge generating layer is further included, the buffer layer  600  may be located between the second electrode  200  and the n-type charge generating layer. 
     The organic light emitting display may further include a charge generating layer  500  located between at least two organic light emitting layers  300  and  400 . The charge generating layer  500  may include an n-type charge generating layer and a p-type charge generating layer. 
     The p-type charge generating layer may generate holes and electrons. The generated holes may be injected into the organic light emitting layer  400  adjacent on, e.g., to, the upper side, and the generated electrons may be injected into the n-type charge generating layer and then injected into the organic light emitting layer  300  adjacent on, e.g., to, the lower side. 
     The n-type charge generating layer may inject the electrons generated from the p-type charge generating layer into the organic light emitting layer  300  on the lower side. The n-type charge generating layer may be made of the same material as that of an electron transport layer, which will be described later. 
       FIG.  2    illustrates a cross-sectional view of an organic light emitting display according to an embodiment. As shown in  FIG.  2   , the charge generating layer  500  may include an n-type charge generating layer  510  and a p-type charge generating layer  520 , which are separated from each other. The n-type charge generating layer  510  may be located adjacent to the first electrode  100 , e.g., relative to the p-type charge generating layer  520 , and the p-type charge generating layer  520  may be located adjacent to the second electrode  200 , e.g., relative to the n-type charge generating layer  510 . The n-type charge generating layer  510  may be formed in contact with the organic light emitting layer  300  located on the lower side, and the p-type charge generating layer  520  may be formed in contact with the organic light emitting layer  400  located on the upper side. The n-type charge generating layer  510  and the p-type charge generating layer  520  may be formed in contact with each other. 
     The other configurations may be the same as described above, and a more detailed description will be omitted. 
       FIGS.  3  and  4    illustrate cross-sectional views of an organic light emitting display according to an embodiment. In the organic light emitting display of  FIGS.  3  and  4   , the quantum dot materials may be removed from the organic light emitting display of  FIGS.  1  and  2   . As shown in  FIGS.  3  and  4   , the quantum dot materials may not be included in the color filters  910  and  950 . 
     The other configurations may be the same as described above, and a repeated description will be omitted. 
       FIG.  5    illustrates a cross-sectional view of an organic light emitting display according to an embodiment. Referring to  FIG.  5   , color filters  911  and  951  may include first regions  915  and  955  adjacent to the second electrode  200 , and second regions  925  and  965 . For example, the color filter  911  ( 951 ) may include the first region  915  ( 955 ) and the second region  925  ( 965 ), which are separated from each other. The second regions  925  and  965  may be formed adjacent to the sealing substrate  700 , or in contact with the sealing substrate  700 . 
     The first color filter  911  may be divided into the first region  915  and the second region  925 , and the second color filter  951  may be divided into the first region  955  and the second region  965 . 
     The quantum dot materials  10  and  20  may be located only in the second regions  925  and  965 . For example, the quantum dot materials  10  and  20  may be formed at positions, adjacent to the sealing substrate  700 , in the respective color filters  911  and  951  to help increase color conversion efficiency. By forming the quantum dot materials  10  and  20  to be close to the sealing substrate  700 , it may be possible to prevent the mixing of colors between the second color light L 2  and the third color light L 3 , and high-purity colors may be implemented. 
     In an embodiment, the quantum dot materials  10  and  20  may be located inside the color filters and may have a constant concentration gradient. The concentration gradient may be set such that the quantum dot materials have a higher concentration as they are closer to the sealing substrate. 
       FIG.  6    illustrates a cross-sectional view of an organic light emitting display according to an embodiment. 
     Referring to  FIG.  6   , the organic light emitting display may include a first charge transfer region  830  and  840  located between the first electrode  100  and the organic light emitting layer  300  and a second charge transfer region  810  and  820  located between the second electrode  200  and the organic light emitting layer  400 . Any one of the first charge transfer region  830  and  840  and the second charge transfer region  810  and  820  may be responsible for the transfer of holes, and the other one thereof may be responsible for the transfer of electrons. 
     In this embodiment, the first electrode  100  may be an anode electrode and the second electrode  200  may be a cathode electrode. The first charge transfer region  830  and  840  adjacent to the anode electrode may be a hole transfer region, and the second charge transfer region  810  and  820  adjacent to the cathode electrode may be an electron transfer region. 
     The first charge transfer region  830  and  840  may have a single layer structure made of a single material or different materials, or a multilayer structure including plural layers made of different materials. In an embodiment, the first charge transfer region  830  and  840  may further include a buffer layer and a first charge blocking layer. In an embodiment, any one of the hole injection layer  830  and the hole transport layer  840  may be omitted, or the hole injection layer  830  and the hole transport layer  840  may be configured as a single layer. 
     The hole injection layer  830  may be disposed on the first electrode  100 , and may increase the efficiency of hole injection into the organic light emitting layers  300  and  400  from the first electrode  100 . For example, the hole injection layer  830  may decrease an energy barrier, and may allow the holes to be injected efficiently. 
     The hole injection layer  830  may include, for example, a phthalocyanine compound such as copper phthalocyanine (CuPc),
     m-MTDATA(4,4′,4″-tris(N-3-methylphenyl-N-phenylamino)triphenylamine),   TDATA(4,4′,4″-tris(diphenylamino)triphenylamine),   2-TNATA(4,4′,4″-tris[2-naphthyl(phenyl)-amino]triphenyl-amine),   Pani/DBSA(Polyaniline/Dodecylbenzenesulfonic acid), PEDOT/PSS(Poly(3,4-ethylene dioxythiophene)/Polystyrene sulfonate), PANI/CSA (Polyaniline/Camphorsulfonic acid), or PANI/PSS (Polyaniline/Polystyrene sulfonate).   

     The hole transport layer  840  may be disposed on the hole injection layer  830  and may transport the holes injected into the hole injection layer  830  to the organic light emitting layers  300  and  400 . When the highest occupied molecular energy (HOMO) of the hole transport layer  840  is substantially lower than the work function of a material forming the first electrode  100 , and is substantially higher than the HOMO of the organic light emitting layers  300  and  400 , the hole transport efficiency may be optimized. The hole transport layer  840  may include, for example,
     NPD(4,4′-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl),   TPD(N,N′-diphenyl-N,N′-bis[3-methylphenyl]-1,1′-biphenyl-4,4′-diamine),   s-TAD(2,2′,7,7′-tetrakis-(N,N-diphenylamino)-9,9′-spirobifluoren), or   m-MTDATA(4,4′,4″-tris(N-3-methylphenyl-N-phenylamino)triphenylamine).   

     The first charge transfer region  830  and  840  may further include a charge generating material to improve conductivity in addition to the above-mentioned materials. The charge generating material may be distributed uniformly or non-uniformly in the first charge transfer region  830  and  840 . The charge generating material may be, for example, a p-dopant. The p-dopant may be, for example, one of a quinone derivative, metal oxide and a cyano group-containing compound. Examples of the p-dopant may include a quinone derivative such as 
     TCNQ (Tetracyanoquinodimethane) and TCNQ (Tetracyanoquinodimethane), and metal oxide such as tungsten oxide and molybdenum oxide. 
     As described above, the first charge transfer region  830  and  840  may further include at least one of the buffer layer and the first charge blocking layer. The buffer layer may increase the light emission efficiency by compensating for a resonance distance according to the wavelength of light emitted from the organic light emitting layers  300  and  400 . As a material included in the buffer layer, a material that may be included in the first charge transfer region  830  and  840  may be used. The first charge blocking layer may prevent the injection of charges into the first charge transfer region  830  and  840  from the second charge transfer region  810  and  820 . 
     The organic light emitting layers  300  and  400  may be disposed on the first charge transfer region  830  and  840 . The organic light emitting layers  300  and  400  may be made of a material that may be used for light emitting layers. For example, the organic light emitting layers  300  and  400  may be made of materials emitting red, green and blue light. In an embodiment, the organic light emitting layers  300  and  400  may be made of a material emitting blue light. The organic light emitting layers  300  and  400  may include a fluorescent material or phosphorescent material. 
     In an exemplary embodiment, the organic light emitting layers  300  and  400  may include a host and a dopant. 
     As the host, for example, Alq3(tris-(8-hydroyquinolato) aluminum(III)),
     CBP(4,4′-N,N′-dicarbazole-biphenyl), PVK(poly(N-vinylcarbazole)),   ADN(9,10-Bis(2-naphthalenyl)anthracene),   TCTA(4,4′,4″-tris(Ncarbazolyl)triphenylamine),   TPBi(1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene), TBADN(2-(t-butyl)-9,   10-bis (20-naphthyl) anthracene), DSA(distyrylarylene),   CDBP(4,4′-Bis(9-carbazolyl)-2,2′-Dimethyl-biphenyl), or   MADN(2-Methyl-9,10-bis(naphthalen-2-yl)anthracene) may be used.   

     As the dopant, both a fluorescent dopant and a phosphorescent dopant may be used. The kind of the dopant may vary according to the light emission color of the organic light emitting layers  300  and  400 . 
     As the red dopant, for example, a fluorescent material including
     PBD:Eu(DBM)3(Phen)(2-biphenyl-4-yl-5-(4-t-butylphenyl)-1,3,4-oxadiazole:Tris(dibenzoylmethane) mono(1,10-phenanthroline)europium(III)) or perylene may be used. In an embodiment, a phosphorescent material including a metal complex such as PIQIr(acac)(bis(1-phenylisoquinoline)acetylacetonate iridium),   PQIr(acac)(bis(1-phenylquinoline)acetylacetonate iridium),   PQIr(tris(1-phenylquinoline)iridium) and PtOEP(octaethylporphyrin platinum) or an organometallic complex may be used.   

     As the green dopant, for example, a fluorescent material including
     Alq3(tris-(8-hydroyquinolato) aluminum(III)) may be used. In an embodiment, a phosphorescent material including, for example,   Ir(ppy)3(fac tris(2-phenylpyridine)iridium),   Ir(ppy)2(acac)(Bis(2-phenylpyridine)(acetylacetonate)iridium(III)), or   Ir(mpyp)3(2-phenyl-4-methyl-pyridine iridium), may be used.   

     As the blue dopant, for example, a fluorescent material including one of spiro-DPVBi(spiro-4,′-bis(2,2′-diphenylvinyl)1,1′-biphenyl), spiro-6P(spiro-sixphenyl), DSB(distyrylbenzene), DSA(distyrylarylene), PFO(polyfluorene)-based polymer and PPV(poly p-phenylene vinylene))-based polymer may be used. In an embodiment, a phosphorescent material including, for example,
     F2Irpic(bis[2-(4,6-difluorophenyl)pyridinato-N,C2′]iridium picolinate),   (F2ppy)2Ir(tmd)(bis[2-(4,6-difluorophenyl)pyridinato-N,C2′]iridium   2,2,6,6-tetramethylheptane-3,5-dione), or   Ir(dfppz)3(tris[1-4,6-difluorophenyl)pyrazolate-N,C2′]iridium), may be used.   

     The second charge transfer region  810  and  820  may be disposed on the organic light emitting layers  300  and  400 . The second charge transfer region  810  and  820  may have a single layer structure made of a single material or different materials, or a multilayer structure including plural layers made of different materials. In an embodiment, the second charge transfer region  810  and  820  may further include a second charge blocking layer. As illustrated in the figure, the second charge transfer region  810  and  820  may include an electron transport layer  820  and an electron injection layer  810 . In an embodiment, any one of the electron transport layer  820  and the electron injection layer  810  may be omitted, or the electron transport layer  820  and the electron injection layer  810  may be configured as a single layer. 
     The electron transport layer  820  may be disposed on the organic light emitting layers  300  and  400 , and may transport electrons injected from the electron injection layer  810  toward the organic light emitting layers  300  and  400 . 
     The electron transport layer  820  may include, for example, Alq3(tris-(8-hydroyquinolato) aluminum(III)), TPBi(1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene), BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), Bphen(4,7-diphenyl-1,10-phenanthroline), TAZ(3-(Biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole), NTAZ(4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole), tBu-PBD(2-(4-biphenylyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole), BAlq(Bis(2-methyl quinolinolato-N1,O8)-(1,1′-Biphenyl-4-olato)aluminum), Bebq2(Bis(10-hydroxybenzo[h]quinolinato)beryllium), ADN(9,10-bis(2-naphthyl)anthracene) or a mixture thereof. 
     The electron injection layer  810  may be disposed on the electron transport layer  820 , and may increase the efficiency of electron injection into the organic light emitting layers  300  and  400  from the second electrode  200 . 
     As the electron injection layer  810 , for example, lanthanide metal such as LiF, LiQ (lithium quinolrate), Li 2 O, BaO, NaCl, CsF and Yb, or halide metal such as RbCl and RbI may be used. The electron injection layer  810  may also be made of a mixture of the above-mentioned material and organo metal salt that may have an insulating property. The organo metal salt may be a material that may have an energy band gap of about 4 eV or more. For example, the organo metal salt may include metal acetate, metal benzoate, metal acetoacetate, metal acetylacetonate or metal stearate. 
     As mentioned above, the second charge transfer region  810  and  820  may further include the second charge blocking layer. The second charge blocking layer may include one or more of, for example, BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) or Bphen(4,7-diphenyl-1,10-phenanthroline). 
     Provided is a manufacturing method of an organic light emitting display. Hereinafter, a manufacturing method of an organic light emitting display will be described with reference again to  FIGS.  1  to  6   . 
     The manufacturing method of an organic light emitting display may include forming the first electrode  100  above the substrate  50 , forming at least two organic light emitting layers  300  and  400  above the first electrode  100  while the charge generating layer  500  is interposed between the organic light emitting layers  300  and  400 , and forming the second electrode  200  above the organic light emitting layers  300  and  400 . 
     The organic light emitting layers may be formed using a soluble material. For example, the organic light emitting layers may be formed using a material containing a solvent. The organic light emitting layers may be formed by mixing a material forming the organic light emitting layers with a solvent, coating the mixed material and solvent by an ink-jet printing method or a discharging method using a slit nozzle, and then, performing a drying and baking step. Thus, it may be possible to simplify a manufacturing process, and it may be possible to reduce the unit price of the product by reducing the manufacturing cost. By forming at least two organic light emitting layers, it may be possible to increase the luminous efficiency. 
     The formation of the organic light emitting layers may be performed under conditions of normal pressure. For example, the formation of the organic light emitting layers may be performed under conditions of atmospheric pressure, or about 1 atmosphere. Since the formation of the organic light emitting layers may be performed under conditions of atmospheric pressure, it may not separately require conditions of vacuum or reduced pressure. Thus, it may be possible to manufacture the organic light emitting display without using an expensive manufacturing apparatus, and the unit price of the product may be reduced. In examples, other organic/inorganic layers in addition to the organic light emitting layers may be formed under conditions of normal pressure. Therefore, the overall manufacturing process of the organic light emitting display may be performed under conditions of normal pressure, and there may be an advantage of reducing the manufacturing cost while simplifying the manufacturing process. In an embodiment, the formation of the second electrode may be performed under conditions of reduced pressure or vacuum by a sputtering process. 
     The manufacturing method of an organic light emitting display may further include forming at least one of a hole injection layer and a hole transport layer between the first electrode and the organic light emitting layers to supply holes generated from the first electrode to the organic light emitting layers, and forming at least one of an electron injection layer and an electron transport layer between the second electrode and the organic light emitting layers to supply electrons generated from the second electrode to the organic light emitting layers. The hole transport layer, the hole injection layer, the electron transport layer and the electron injection layer have been already described in conjunction with the organic light emitting display, and a more detailed description will be omitted. 
     The manufacturing method of an organic light emitting display may further include forming a buffer layer including one or more of WO 3 , MoO x , or HATCN below the second electrode. The second electrode may be formed using the above-mentioned materials forming the second electrode by a sputtering method. The organic layers located between the first electrode and the second electrode may be damaged. By forming the buffer layer, in a process of forming the second electrode, it may be possible to prevent damage or performance degradation of various organic layers located between the first electrode and the second electrode, for example, due to the material forming the second electrode. 
     The manufacturing method of an organic light emitting display may further include preparing a sealing substrate on which at least two color filters including quantum dot materials are formed, and laminating the substrate and the sealing substrate while the color filters are located to face, e.g., be separated from, the second electrode. The quantum dot materials, the color filters, and the sealing substrate, for example, have been already described, and a redundant description will be omitted. 
     By way of summation and review, an organic light emitting display may be a self-luminous type display for displaying an image by using an organic light emitting diode that emits light. The organic light emitting display may be configured such that holes and electrons are injected by a first electrode and a second electrode, the injected holes and electrons are coupled in a light emitting layer located between the first electrode and the second electrode, and light may be generated by energy generated when exitons formed by the coupling fall to the ground state. 
     The organic light emitting diode may include, for example, a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer, in addition to an organic light emitting layer between an anode and a cathode. 
     An organic light emitting diode that emits white light may be referred to as a white organic light emitting diode. 
     According to embodiments, it may be possible to provide an organic light emitting display that may be capable of improving color purity while preventing a change in color according to a viewing angle. 
     Also, it may be possible to provide a manufacturing method of an organic light emitting display, that may be capable of facilitating the manufacture and reducing the manufacturing cost. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.