ORGANIC LIGHT EMITTING DIODE COMPRISING ORGANOMETALLIC COMPOUND AND VARIOUS TYPES OF HOST MATERIALS

An emission material layer has a dopant material containing an organometallic compound represented by Chemical Formula 1 and host materials with a compound represented by Chemical Formula 2 and a compound represented by Chemical Formula 3, and an organic light emitting diode including the same. The organic light emitting diode has characteristics such as high luminous efficiency and long lifetime.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2023-0144049, filed Oct. 25, 2023, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND

The present disclosure relates to an organic light emitting diode including an organometallic compound and various types of host materials.

Interest in display devices is increasing according to the application to various fields. As one of the display devices, a technology of an organic light emitting display devices including an organic light emitting diode (OLED) is developing rapidly.

The OLED is an element for emitting energies of excitons as light after forming electrons and holes in pair to form excitons when charges are injected into an emission material layer formed between an anode and a cathode. Compared to conventional display technologies, the OLED can implement a low voltage, consume relatively less power, have excellent colors, can be applied to a flexible substrate to be used variously, and can allow a display device to be freely adjusted in size.

The OLED can have a wide viewing angle and a high contrast ratio compared to liquid crystal display (LCD) devices and does not require a backlight, making it lightweight and ultra-thin. The OLED is formed by arranging a plurality of organic layers, such as a hole injection layer, a hole transport layer, a hole transport auxiliary layer, an electron blocking layer, an emission material layer, an electron transport layer, an electron injection layer, and the like between the cathode (electron injection layer) and the anode (hole injection layer).

In the structure of the OLED, when a voltage is applied between two electrodes, electrons and holes are injected from the cathode and the anode, respectively, and excitons generated from the emission material layer fall to a ground state to emit light.

Organic materials used in the OLED may be largely classified into a light emitting material and a charge transport material. The light emitting material is an important factor in determining the luminous efficiency of the OLED, and the light emitting material should have high quantum efficiency, excellent mobility of electrons and holes, and be uniformly and stably present in the emission material layer. The light emitting material is classified into light emitting materials, such as blue, red, and green, depending on colored light and is used as hosts and dopants to increase color purity and increase luminous efficiency through energy transfer as color materials.

In the case of fluorescent materials, while only a singlet of about 25% of the excitons formed in the emission material layer is used to generate light, and a triplet of 75% is mostly lost as heat, phosphorescent materials has a luminous mechanism that converts both the singlet and the triplet into light.

So far, organic metal compounds have been used as phosphorescent materials used in the OLED. There is still a technical need to improve the performance of the OLED by deriving high-efficiency phosphorescent dopant materials and applying hosts with optimal photophysical characteristics to improve the efficiency and lifetime of the element compared to conventional OLEDS.

SUMMARY

Therefore, the present disclosure is directed to providing an organic light emitting diode (OLED) in which an organometallic compound and various types of host materials, which are capable of increasing a driving voltage, efficiency, and a lifetime, are applied to an organic emission material layer.

The objects of the present disclosure are not limited to the above-described object, and other objects and advantages of the present embodiments which are not mentioned can be understood by the following description and more clearly understood by embodiments of the present disclosure. In addition, it can be easily seen that the objects and advantages of the present disclosure can be achieved by means and combinations thereof which are described in the claims.

To achieve the object, the present disclosure may provide an organic light emitting diode including a first electrode, a second electrode facing the first electrode, and an intermediate layer disposed between the first electrode and the second electrode, wherein the intermediate layer includes an emission material layer, and the emission material layer includes a dopant material and a host material, the dopant material includes an organometallic compound represented by Chemical Formula 1 below, and the host material includes a mixture of a compound represented by Chemical Formula 2 below and a compound represented by Chemical Formula 3 below:

In Chemical Formula 2,

In Chemical Formula 3,

According to another aspect of the present disclosure, there may be provided an organic light emitting diode including a first electrode, a second electrode facing the first electrode, and one or more light emitting parts positioned between the first electrode and the second electrode, wherein at least one of the light emitting parts includes a green phosphorescent layer, the green phosphorescent layer includes a dopant material and a host material, the dopant material includes an organometallic compound represented by Chemical Formula 1 below, and the host material includes a compound represented by Chemical Formula 2 below and a compound represented by Chemical Formula 3 below, and the definition of Chemical Formulas 1 to 3 are the same as those defined in one aspect of the present embodiment.

DETAILED DESCRIPTION

The above-described objects, features, and advantages will be described below in detail with reference to the accompanying drawings, and thus those skilled in the art to which the present disclosure pertains will be able to easily carry out the technical spirit of the present embodiment. In describing the present embodiment, when it is determined that a detailed description of the known technology related to the present disclosure may unnecessarily obscure the gist of the present disclosure, a detailed description thereof will be omitted. Hereinafter, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to denote the same or similar components.

In the specification, when terms “including,” “having,” “consisting of,” “arranging,” “providing,” and the like are used, other portions can be added unless “only” is used. When a component is expressed in the singular, it includes a case in which the component is provided as a plurality of components unless specifically stated otherwise.

In construing a component in the specification, the component is construed as including the margin of error even when there is no separate explicit description.

In the specification, the arrangement of an arbitrary component on an “upper portion (or a lower portion)” of a component or “above (or under)” the component may not only mean that the arbitrary component is disposed in contact with an upper surface (or a lower surface) of the component, but also mean that other components may be interposed between the component and the arbitrary component disposed above (or under) the component.

The term “halo” or “halogen” used herein includes fluorine, chlorine, bromine, and iodine.

The term “alkyl group” used herein indicates both linear alkyl radicals and branched alkyl radicals. Unless otherwise specified, the linear alkyl group contains 1 to 20 carbon atoms, the branched alkyl group contains 3 to 20 carbon atoms and methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and the like, and additionally, the alkyl group may be substituted arbitrarily.

The term “cycloalkyl group” used therein indicates cyclic alkyl radicals. Unless otherwise specified, the cycloalkyl group contains 3 to 20 carbon atoms and cyclopropyl, cyclopentyl, cyclohexyl, and the like, and additionally, the cycloalkyl group may be substituted arbitrarily.

The term “alkenyl group” used herein indicates both linear alkene radicals and branched alkene radicals. Unless otherwise specified, the alkenyl group contains 2 to 20 carbon atoms, and additionally, the alkenyl group may be substituted arbitrarily.

The term “cycloalkenyl group” used therein indicates cyclic alkenyl radicals. Unless otherwise specified, the cycloalkenyl group contains 3 to 20 carbon atoms, and additionally, the cycloalkenyl group may be substituted arbitrarily.

The term “alkynyl group” used herein indicates both linear alkyne radicals and branched alkyne radicals. Unless otherwise specified, the alkynyl group contains 2 to 20 carbon atoms. Additionally, the alkynyl group may be substituted arbitrarily.

The term “cycloalkynyl group” used therein indicates cyclic alkynyl radicals. Unless otherwise specified, the cycloalkynyl group contains 3 to 20 carbon atoms, and additionally, the cycloalkynyl group may be substituted arbitrarily.

The terms “aralkyl group” and “arylalkyl group” used herein are used interchangeably and indicate an alkyl group having an aryl group as a substituent, and unless otherwise specified, for the aryl group and the alkyl group in the aralkyl group (arylalkyl group), reference may be made to the above definition. And additionally, the aralkyl group (arylalkyl group) may be substituted arbitrarily.

The term “aryl group” or “aromatic group” used herein is used with the same meaning, and the aryl group includes both single ring groups and polycyclic ring groups. The polycyclic ring may include “condensed ring,” which are two or more rings in which two carbons are common to two adjacent rings. Unless otherwise specified, the aryl group contains 5 to 60 carbon atoms, and additionally, the aryl group may be substituted arbitrarily.

The term “heterocyclic group” used herein indicates that one or more of the carbon atoms constituting the aryl group, the cycloalkyl group, the cycloalkenyl group, the cycloalkynyl group, the aralkyl group (arylalkyl group), the arylamino group, and the like is substituted with a heteroatom, such as oxygen (O), nitrogen (N), or sulfur(S), and with reference to the above definition, includes the heteroaryl group, the heterocycloalkyl group, the heterocycloalkenyl group, the heterocycloalkynyl group, the heteroarylalkyl group (heteroarylalkyl group), heteroarylamino group, and the like, and the heteroaryl group contains 2 to 60 carbon atoms and additionally, may be substituted arbitrarily.

Unless otherwise specified, the term “carbon ring” used herein may be used as the term including all of “cycloalkyl group,” “cycloalkenyl group,” and “cycloalkynyl group,” which are alicyclic ring groups, and “aryl group (aromatic group),” which is an aromatic ring group.

The terms “heteroalkyl group,” “heteroalkenyl group,” “heteroalkynyl group,” and “heteroaralkyl group (heteroarylalkyl group)” used herein indicate that one or more of the carbon atoms constituting the same are substituted with heteroatoms, such as oxygen (O), nitrogen (N), and sulfur(S), and additionally, the heteroalkyl group, the heteroalkenyl group, the heteroalkynyl group, and heteroaralkyl group (heteroarylalkyl group) may be substituted arbitrarily.

The terms “alkylamino group,” “aralkyl amino group,” “arylamino group,” and “heteroarylamino group” used herein indicate that the amine group is substituted with the alkyl group, the aralkyl group, the aryl group, and the heteroaryl group that is a hetero ring and include all of primary, secondary, and tertiary amines, and additionally, the alkylamino group, the aralkylamino group, the arylamino group, and the heteroarylamino group may be substituted arbitrarily.

The terms “alkylsilyl group,” “arylsilyl group,” “alkoxy group,” “aryloxy group,” “alkylthio group,” and “arylthio group” indicate that the silyl group, the oxy group, or the thio group are substituted with, and additionally, the alkylsilyl group, the arylsilyl group, the alkoxy group, the aryloxy group, the alkylthio group, and the arylthio group may be substituted arbitrarily.

The term “substituted” used herein indicates that a substituent other than hydrogen (H) is bonded to the corresponding carbon, and when a plurality of substituents are provided, the substituents may be the same as or different from each other.

Herein, “deuterated” may indicate substitution with deuterium instead of light hydrogen in a compound. The “partially deuterated” may include a substituent in which all hydrogen or a part of hydrogen in alkyl groups are deuterated.

Unless otherwise specified herein, a position to be substituted is not limited as long as it is a position where a hydrogen atom is substituted, that is, a position where a substituent may be substituted, and when two or more substituents are provided, the substituents may be the same as or different from each other.

The objects and substituents defined herein may be the same as or different from each other unless otherwise specified.

Hereinafter, a structure of an organometallic compound and an organic light emitting diode (OLED) including the same according to the present disclosure will be described in detail.

Conventionally, organometallic compounds have been used as dopants in phosphorescent layers, and for example, structures such as 2-phenylpyridine are known as main ligand structures of the organometallic compounds. However, since the conventional light emitting dopants have limitations in increasing the efficiency and lifetime of OLEDs, it is necessary to develop new light emitting dopant materials. The present disclosure was completed by experimentally confirming that by mixing a hole transport type host and an electron transport type host as host materials together with the dopant material, it was possible to further increase the efficiency and lifetime of the OLED and decrease the driving voltage, thereby improving the characteristics of the OLED.

Specifically, referring to FIG. 1 according to one embodiment of the present disclosure, there may be provided an OLED 100 including a first electrode 110, a second electrode 120 facing the first electrode 110, and an intermediate layer 130 disposed between the first electrode 110 and the second electrode 120. The intermediate layer 130 may include an emission material layer 160, the emission material layer 160 may include a dopant material 160′ and host materials 160″ and 160′″. The emission material layer 160 may include the organometallic compound 160′ represented by Chemical Formula 1 below as the dopant material, and the host material may include two types of the compound 160″ represented by Chemical Formula 2 below as the hole transport type host and the compound 160′″ represented by Chemical Formula 3 below as the electron transport type host.

In Chemical Formula 1,

In Chemical Formula 2,

In Chemical Formula 3,

According to some embodiments of the present disclosure, the organometallic compound represented by Chemical Formula 1 may have a homoleptic or heteroleptic structure, for example, have a homoleptic structure in which n is 0, a heteroleptic structure in which n is 1, or a heteroleptic structure in which n is 2 in Chemical Formula 1, and n may be, for example, 2.

According to some embodiments of the present disclosure, n in Chemical Formula 1 may be an integers from 0 to 2, and n may be, for example, 2.

According to some embodiments of the present disclosure, X in Chemical Formula 1 may be oxygen (O) or sulfur(S), and X may be, for example, oxygen (O).

According to some embodiments of the present disclosure, m in Chemical Formula 1 may be 1 or more, for example, may be an integer of 1 to 3, and for example, may be an integer of 1 or 2.

According to some embodiments of the present disclosure, (R1)a and (R2)b in Chemical Formula 1 may, each independently, be at least one selected from the group consisting of hydrogen, deuterium, a C1-C10 alkyl group, a C5-C30 aryl group, a C3-C30 heteroaryl group, and a C6-C40 arylalkyl group, and a and b, each independently, may be an integer of 1 or 2.

According to some embodiments of the present disclosure, at least one of R1 or at least one of R2 in Chemical Formula 1 may be a C1-C3 alkyl group, and in this case, the C1-C3 alkyl group as R1 or R2 may be substituted with deuterium.

According to some embodiments of the present disclosure, at least one R3 in Chemical Formula 1 may be a C1-C3 linear alkyl group, and in this case, R3 may be substituted with deuterium.

According to some embodiments of the present disclosure, R4 in Chemical Formula 1 may be all hydrogen.

According to some embodiments of the present disclosure, e of R5 in Chemical Formula 1 may be all hydrogen, or otherwise, 1 or 2 of R5 may not be hydrogen.

According to some embodiments of the present disclosure, when 1 or 2 of R5 are not hydrogen, R5 that are not hydrogen may be at least one selected from the group consisting of deuterium, a C1-C10 linear alkyl group, and a C3-C10 branched alkyl group, and R5 may be substituted with deuterium.

According to some embodiments of the present disclosure, R6 in Chemical Formula 1 may be all hydrogen.

According to some embodiments of the present disclosure, a moiety including Ry and Re attached to a pyridine ring in Chemical Formula 1 may form an aralkyl group. According to some embodiments of the present disclosure, R7 and R8, may, each independently, be deuterium, a C1-C3 linear alkyl group, and a C3-C6 branched alkyl group, and optionally, the C1-C3 linear alkyl group or the C3-C6 branched alkyl group, and R7 and R8 may, each independently, be substituted with deuterium.

According to some embodiments of the present disclosure, the organometallic compound represented by Chemical Formula 1 may be one of Compounds GD1 to GD20 below, but is not limited thereto as long as it is included in the definition of Chemical Formula 1.

According to some embodiments of the present disclosure, Ra and Rb in Chemical Formula 2 may be a C3-C40 monocyclic or polycyclic aryl group or heteroaryl group, and optionally, the C3-C40 aryl groups may, each independently, be substituted with one or more substituents of an alkyl group, an aryl group, a cyano group, an alkylsilyl group, and an arylsilyl group, and when a plurality of substituents are provided, the substituents may be the same or different from each other.

According to some embodiments of the present disclosure, Ra and Rb may be a C3-C40 monocyclic or polycyclic aryl group, and for example, Ra and Rb may, each independently, be at least one selected from the group consisting of a phenyl group, a naphthyl group, an anthracene group, a chrysene group, a pyrene group, a phenanthrene group, a triphenylene group, a fluorene group, 9,9′-spirofluorene group, a biphenyl group, a terphenyl group, and a 9,9-dimethyfluorene group, but is not limited thereto.

According to some embodiments of the present disclosure, Rc and Rd in Formula 2 may each be one of hydrogen, deuterium, halogen, a cyano group, and an alkyl group, which may be the same or different from each other, and, Rc and Ra may all be hydrogen.

According to some embodiments of the present disclosure, the compound represented by Chemical Formula 2 may be at least one selected from the group consisting of Compounds GHH1 to GHH30 below, but is not limited thereto as long as it is included in the definition of Chemical Formula 2.

According to some embodiments of the present disclosure, p and q in Chemical Formula 3 may, each independently, be 0 or 1.

According to some embodiments of the present disclosure, Ar1 and Ar2 in Chemical Formula 3 may, each independently, be hydrogen or a C6-C50 aryl group.

According to some embodiments of the present disclosure, Ar3 in Chemical Formula 3 may be at least one selected from the group consisting of a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, an anthracenyl group, a phenanthryl group, a pyrenyl group, a perylenyl group, a chrysenyl group, a triphenylene group, a 9,9′-spirofluorene group, and a substituted or unsubstituted fluorenyl group such as a 9,9-dimethylfluorenyl group and a 9,9-diphenylfluorenyl group.

According to some embodiments of the present disclosure, Ar3 may be substituted with one or more substituents of a C1-C3 alkyl group and a C6-C10 aryl group, and when a plurality of substituents for Ar3 are provided, the substituents may be the same or different from each other.

According to some embodiments of the present disclosure, the organometallic compound represented by Chemical Formula 3 may be one of Compounds GEH1 to GEH30 below, but is not limited thereto as long as it is included in the definition of Chemical Formula 3.

In addition, in the OLED 100, the intermediate layer 130 disposed between the first electrode 110 and the second electrode 120 may have a structure including a hole injection layer (HIL) 140, a hole transport layer (HTL) 150, the emission material layer (EML) 160, an electron transport layer (ETL) 170, and an electron injection layer (EIL) 180 sequentially disposed from the first electrode 110. The second electrode 120 may be formed on the electron injection layer 180, and a protective film (not shown) may be formed on the second electrode 120.

In addition, although not shown in FIG. 1, one or more of a hole transport auxiliary layer and an electron blocking layer may be further added between the hole transport layer 150 and the emission material layer 160.

The hole transport auxiliary layer may contain a compound with good hole transport characteristics and adjust the hole injection characteristics by reducing an HOMO energy level difference between the hole transport layer 150 and the emission material layer 160, thereby reducing the accumulation of holes at an interface between the hole transport auxiliary layer and the emission material layer 160. Therefore, it is possible to reduce a quenching phenomenon that excitons are annihilated by polarons at the interface. Therefore, it is possible to reduce a degradation phenomenon of the element, thereby stabilizing the element and increasing efficiency and lifetime thereof.

The electron blocking layer can prevent the introduction of electrons into the hole transport layer by adjusting the movement of electrons and the recombination with holes, thereby increasing the efficiency and lifetime of the OLED. A material forming the electron blocking layer may include at least on selected from the group consisting of TCTA, tris[4-(diethylamino)phenyl]amine, N-(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine, TAPC, MTDATA, mCP, mCBP, CuPC, DNTPD, TDAPB, DCDPA, 2,8-bis(9-phenyl-9H-carbazol-3-yl)dibenzo[b,d]thiophene, and the like. In addition, the electron blocking layer may include an inorganic compound. The inorganic compound may include at least one selected from the group consisting of halide compounds, such as LiF, NaF, KF, RbF, CsF, FrF, MgF2, CaF2, SrF2, BaF2, LiCl, NaCl, KCl, RbCl, CsCl, and FrCl, and oxides, such as Li2O, Li2O2, Na2O, K2O, Rb2O, Rb2O2, Cs2O, Cs2O2, LiAlO2, LiBO2, LiTaO3, LiNbO3, LiWO4, Li2CO, NaWO4, KAlO2, K2SiO3, B2O5, Al2O3, and SiO2, but is not necessarily limited thereto.

The first electrode 110 may be an anode and may be made of ITO, IZO, tin-oxide, or zinc-oxide, which is a conductive material with a relatively high work function value, but is not limited thereto.

The second electrode 120 may be a cathode and may include Al, Mg, Ca, Ag, or an alloy or combination thereof, which is a conductive material with a relatively low work function value, but is not limited thereto.

The hole injection layer 140 may be positioned between the first electrode 110 and the hole transport layer 150. The hole injection layer 140 may have a function of improving the interface characteristics between the first electrode 110 and the hole transport layer 150 and may be selected as a material with appropriate conductivity. The hole injection layer 140 may include a compound, such as MTDATA, CuPc, TCTA, HATCN, TDAPB, PEDOT/PSS, or N1,N1′-([1,1′-bipheny]-4,4′-diyl)bis(N1,N4,N4-triphenylbenzene-1,4-diamine), preferably, N1,N1′-([1,1′-biphenyl]-4,4′-diyl)bis(N1,N4,N4-triphenylbenzene-1,4-diamine), but is not limited thereto.

The hole transport layer 150 may be positioned adjacent the emission material layer between the first electrode 110 and the emission material layer 160. The hole transport layer 150 may include a compound, such as TPD, NPB, CBP, N-(biphenyl-4-yl)-9,9-dimethyl-N-((4-9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine, or N-(biphenyl-4-yl)-N-(((4-9-phenyl-9H-carbazol-3-yl)phenyl)biphenyl)-4-amine, preferably, NPB, but is not limited thereto.

According to some embodiments of the present disclosure, the emission material layer 160 may be formed by being doped with the organometallic compound represented by Chemical Formula 1 as the dopant 160′ to increase the luminous efficiency and the like of the hosts 160″ and 160′″ and the element, and the dopant 160′ may be used as a material that emits light of green or red and for example, can be used as a green phosphorescent material.

According to some embodiments of the present disclosure, a doping concentration of the dopant 160′ may be adjusted in the range of 1 to 30 wt % based on the total weight of the two types of hosts 160″ and 160′″ and is not limited thereto, but for example, the doping concentration may be 2 to 20 wt %, for example, 3 to 15 wt %, for example, 5 to 10 wt %, for example, 3 to 8 wt %, for example, 2 to 7 wt %, for example, 5 to 7 wt %, and for example, 5 to 6 wt %.

According to some embodiments of the present disclosure, a mixing ratio of the two types of hosts 160″ and 160′″ is not particularly limited, and the host 160″, which is the compound represented by Chemical Formula 2, may have the hole transport characteristics and the host 160′″, which is the compound represented by Chemical Formula 3, may have the electron transport characteristics. Therefore, when the two types of hosts are mixed, it is possible to increase the lifetime characteristics, and the mixing ratio of the two types of hosts may be adjusted appropriately. Therefore, the mixing ratio of the two hosts in which the compound represented by Chemical Formula 2 and the compound represented by Chemical Formula 3 are mixed is not particularly limited, and the ratio (based on the weight) of the compound represented by Chemical Formula 2 and the compound represented by Chemical Formula 3 may be, for example, in the range of 1:9 to 9:1, for example, 2:8, for example, 3:7, for example, 4:6, for example, 5:5, for example, 6:4, for example 7:3, and for example, 8:2.

In addition, the electron transport layer 170 and the electron injection layer 180 may be sequentially stacked between the emission material layer 160 and the second electrode 120. A material of the electron transport layer has high electron mobility, and electrons may be stably supplied to the emission material layer through smooth electron transport.

For example, the material of the electron transport layer 170 is used in the art and may include, for example, a compound, such as Alq3(tris(8-hydroxyquinolino)aluminum), Liq(8-hydroxyquinolinolatolithium), PBD(2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4oxadiazole), TAZ(3-(4-biphenyl)4-phenyl-5-tert-butylphenyl-1,2,4-triazole), spiro-PBD, BALq(bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminium), SAlq, TPBi(2,2′,2-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), oxadiazole, triazole, phenanthroline, benzoxazole, benzthiazole, or 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo[d]imidazole, preferably 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo[d]imidazole, but is not limited thereto.

The electron injection layer 180 serves to allow electrons to be smoothly injected, and a material of the electron injection layer is used in the art and may include, for example, Alq3(tris(8-hydroxyquinolino)aluminum), PBD, TAZ, spiro-PBD, BAlq, SAlq, or the like, but is not limited thereto. Alternatively, the electron injection layer 180 may be made of a metal compound, and the metal compound may include, for example, Liq, LiF, NaF, KF, RbF, CsF, FrF, BeF2, MgF2, CaF2, SrF2, BaF2, RaF2, or the like, but is not limited thereto.

The OLED according to the present disclosure may be a white OLED with a tandem structure. In the tandem OLED according to some embodiments of the present disclosure, a single light emitting stack (or a light emitting part) may be formed in a structure in which two or more light emitting stacks (or light emitting parts) are connected by the charge generation layer CGL. The OLED may include two or more light emitting stacks (light emitting parts), which include the first and second electrodes that face each other on the substrate and the emission material layer stacked between the first and second electrodes to emit light in a specific wavelength band. The plurality of light emitting stacks (light emitting parts) may be applied to emit the same color or different colors. In addition, one light emitting stack (light emitting part) may include one or more emission material layers, and the plurality of light emitting layers may be light emitting layers of the same color or different colors.

In this case, one or more of the emission material layers included in the plurality of light emitting parts may include the organometallic compound represented by Chemical Formula 1 according to the present embodiment as a dopant material. The plurality of light emitting parts in the tandem structure may be connected to the charge generation layer CGL formed of an N-type charge generation layer and a P-type charge generation layer.

FIGS. 2 and 3, which are exemplary embodiments of the present disclosure, are cross-sectional views schematically showing OLEDs in tandem structures having two light emitting parts and three light emitting parts, respectively.

As shown in FIG. 2, the OLED 100 of the present embodiment includes the first electrode 110 and the second electrode 120 that face each other, and an intermediate layer 230 positioned between the first electrode 110 and the second electrode 120. The intermediate layer 230 includes a first light emitting part ST1 positioned between the first electrode 110 and the second electrode 120 and including a first emission material layer 261, a second light emitting part ST2 positioned between the first light emitting part ST1 and the second electrode 120 and including a second emission material layer 262, and the charge generation layer CGL positioned between the first and second light emitting parts ST1 and ST2. The charge generation layer CGL may include an N-type charge generation layer 291 and a P-type charge generation layer 292. One or more of the first emission material layer 261 and the second emission material layer 262 may include the organometallic compound represented by Chemical Formula 1 according to the present embodiment as a dopant 262′. For example, as shown in FIG. 2, the second emission material layer 262 of the second light emitting part ST2 may contain the compound 262′ represented by Chemical Formula 1 as the dopant, a compound 262″ represented by Chemical Formula 2 as the hole transport type host, and a compound 262′″ represented by Chemical Formula 3 as an electron transport type host. Although not shown in FIG. 2, each of the first and second light emitting parts ST1 and ST2 may further include an additional emission material layer in addition to the first emission material layer 261 and the second emission material layer 262. The contents described above in relation to the hole transport layer 150 of FIG. 1 may be applied to the first hole transport layer 251 and the second hole transport layer 252 of FIG. 2 in the same or similar manner. In addition, the contents described above in relation to the electron transport layer 170 of FIG. 1 may be applied to the first electron transport layer 271 and the second electron transport layer 272 of FIG. 2 in the same or similar manner.

As shown in FIG. 3, the OLED 100 of the present embodiment includes the first electrode 110 and the second electrode 120 that face each other, and an intermediate layer 330 positioned between the first electrode 110 and the second electrode 120. The intermediate layer 330 includes the first light emitting part ST1 positioned between the first electrode 110 and the second electrode 120 and including the first emission material layer 261, the second light emitting part ST2 including the second emission material layer 262, a third light emitting part ST3 including a third emission material layer 263, a first charge generation layer CGL1 positioned between the first and second light emitting parts ST1 and ST2, and a second charge generation layer CGL2 positioned between the second and third light emitting parts ST2 and ST3. The first and second charge generation layers CGL1 and CGL2 may include the N-type charge generation layers 291 and 293 and the P-type charge generation layers 292 and 294, respectively. One or more of the first emission material layer 261, the second emission material layer 262, and the third emission material layer 263 may include the organometallic compound represented by Chemical Formula 1 according to the present embodiment as the dopant. For example, as shown in FIG. 3, the second emission material layer 262 of the second light emitting part ST2 may contain the compound 262′ represented by Chemical Formula 1 as the dopant, the compound 262″ represented by Chemical Formula 2 as the hole transport type host, and the compound 262′″ represented by Chemical Formula 3 as the electron transport type host. Although not shown in FIG. 3, in addition to the first emission material layer 261, the second emission material layer 262, and the third emission material layer 263, each of the first, second, and third light emitting parts ST1, ST2, and ST3 may be formed as a plurality of emission material layers by including an additional emission material layer. The contents described above in relation to the hole transport layer 150 of FIG. 1 may be applied to the first hole transport layer 251, the second hole transport layer 252, and the third hole transport layer 253 of FIG. 3 in the same or similar manner. In addition, the contents described above in relation to the electron transport layer 170 of FIG. 1 may be applied to the first electron transport layer 271, the second electron transport layer 272, and the third electron transport layer 273 of FIG. 3 in the same or similar manner.

Furthermore, the OLED according to one embodiment of the present disclosure may include a tandem structure in which four or more light emitting parts and three or more charge generation layers are disposed between the first electrode and the second electrode.

The OLED according to the present embodiment may be used in OLED display devices and lighting devices using OLEDs. In one embodiment, FIG. 4 is a cross-sectional view schematically showing an OLED display device to which the OLED according to some exemplary embodiments of the present disclosure is applied.

As shown in FIG. 4, an OLED display device 3000 may include a substrate 3010, an OLED 4000, and an encapsulation film 3900 covering the OLED 4000. On the substrate 3010, a driving thin film transistor Td, which is a driving element, and the OLED 4000 connected to the driving thin film transistor Td are positioned.

Although not explicitly shown in FIG. 4, on the substrate 3010, a gate line and a data line that intersect each other to define a pixel area, a power line spaced apart from any one of the gate line and the data line and extending in parallel, a switching thin film transistor connected to the gate line and the data line, and a storage capacitor connected to the power line and one electrode of the switching thin film transistor are further formed.

The driving thin film transistor Td is connected to the switching thin film transistor and includes a semiconductor layer 3100, a gate electrode 3300, a source electrode 3520, and a drain electrode 3540.

The semiconductor layer 3100 may be formed on the substrate 3010 and may be made of an oxide semiconductor material or polycrystalline silicon. When the semiconductor layer 3100 is made of the oxide semiconductor material, a light blocking pattern (not shown) may be formed under the semiconductor layer 3100, and the light blocking pattern prevents light incident on the semiconductor layer 3100, thereby preventing the degradation of the semiconductor layer 3100 caused by the light. Alternatively, the semiconductor layer 3100 may be made of polycrystalline silicon, and in this case, both edges of the semiconductor layer 3100 may be doped with impurities.

A gate insulating film 3200 made of an insulating material is formed on the entire surface of the substrate 3010 and the semiconductor layer 3100. The gate insulating film 3200 may be made of an inorganic insulating material, such as silicon oxide or silicon nitride.

A gate electrode 3300 made of a conductive material, such as a metal, is formed above the gate insulating film 3200 to correspond to the center of the semiconductor layer 3100. The gate electrode 3300 is connected to the switching thin film transistor.

An interlayer insulating film 3400 made of an insulating material is formed on the entire surface of the substrate 3010 and the gate electrode 3300. The interlayer insulating film 3400 may be made of an inorganic insulating material, such as silicon oxide or silicon nitride, or made of an organic insulating material, such as benzocyclobutene or photo-acryl.

The interlayer insulating film 3400 has first and second semiconductor layer contact holes 3420 and 3440 that expose both sides of the semiconductor layer 3100. The first and second semiconductor layer contact holes 3420 and 3440 are positioned to be spaced apart from the gate electrode 3300 at both sides of the gate electrode 3300.

The source electrode 3520 and the drain electrode 3540 made of the conductive material, such as a metal, are formed on the interlayer insulating film 3400. The source electrode 3520 and the drain electrode 3540 are positioned to be spaced apart from each other with respect to the gate electrode 3300 and are in contact with both sides of the semiconductor layer 3100 through the first and second semiconductor layer contact holes 3420 and 3440, respectively. The source electrode 3520 is connected to the power line (not shown).

The semiconductor layer 3100, the gate electrode 3300, the source electrode 3520, and the drain electrode 3540 form the driving thin film transistor Td, and the driving thin film transistor Td has a coplanar structure in which the gate electrode 3300, the source electrode 3520, and the drain electrode 3540 are positioned above the semiconductor layer 3100.

Alternatively, the driving thin film transistor Td may have an inverted staggered structure in which the gate electrode is positioned under the semiconductor layer and the source electrode and the drain electrode are positioned above the semiconductor layer. In this case, the semiconductor layer may be made of amorphous silicon. Meanwhile, the switching thin film transistor (not shown) may have substantially the same structure as the driving thin film transistor Td.

Meanwhile, the OLED display device 3000 may include a color filter 3600 that absorbs light generated by the OLED 4000. For example, the color filter 3600 may absorb light of red (R), green (G), blue (B), and white (W). In this case, red, green, and blue color filter patterns that absorb light may be formed separately in each pixel area, and each of the color filter patterns may be disposed to overlap each intermediate layer 4300 of the OLED 4000 that emits light in a wavelength band to be absorbed. By adopting the color filter 3600, the OLED display device 3000 can implement full-color.

For example, when the OLED display device 3000 is a bottom-emission type, the color filter 3600 that absorbs light may be positioned above the interlayer insulating film 3400 corresponding to the OLED 4000. In an exemplary embodiment, when the OLED display device 3000 is a top-emission type, the color filter may be positioned above the OLED 4000, that is, above a second electrode 4200. For example, the color filter 3600 may be formed to have a thickness of 2 to 5 μm.

Meanwhile, a planarization layer 3700 with a drain contact hole 3720 that exposes the drain electrode 3540 of the driving thin film transistor Td is formed to cover the driving thin film transistor Td.

On the planarization layer 3700, a first electrode 4100 connected to the drain electrode 3540 of the driving thin film transistor Td through the drain contact hole 3720 is formed separately in each pixel area.

The first electrode 4100 may be an anode and may be made of a conductive material with a relatively high work function value. For example, the first electrode 4100 may be made of a transparent conductive material, such as ITO, IZO, or ZnO.

Meanwhile, when the OLED display device 3000 is a top-emission type, a reflective electrode or a reflective layer may be further formed under the first electrode 4100. For example, the reflective electrode or the reflective layer may be made of any one of aluminum (Al), silver (Ag), nickel (Ni), or an aluminum-palladium-copper (APC) alloy.

A bank layer 3800 covering an edge of the first electrode 4100 is formed on the planarization layer 3700. The bank layer 3800 exposes the center of the first electrode 4100 corresponding to the pixel area.

The intermediate layer 4300 is formed on the first electrode 4100, and if necessary, the OLED 4000 may have a tandem structure, and regarding the tandem structure, reference is made to FIGS. 2 to 3 showing the exemplary embodiments of the present disclosure and the above description thereof.

The second electrode 4200 is formed above the substrate 3010 on which the intermediate layer 4300 is formed. The second electrode 4200 may be positioned on the entire surface of the display area and may be made of a conductive material with a relatively low work function value to be used as a cathode. For example, the second electrode 4200 may be made of any one of aluminum (Al), magnesium (Mg), and aluminum-magnesium alloy (Al—Mg).

The first electrode 4100, the intermediate layer 4300, and the second electrode 4200 form the OLED 4000.

On the second electrode 4200, the encapsulation film 3900 is formed to prevent the permeation of external moisture into the OLED 4000. Although not explicitly shown in FIG. 4, the encapsulation film 3900 may have a triple-layer structure in which a first inorganic layer, an intermediate layer, and an inorganic layer are sequentially stacked, but is not limited thereto.

Hereinafter, examples of the present embodiments will be described. However, the following examples are only examples of the present embodiments, and the present disclosure is not limited thereto.

A glass substrate coated with a thin film of ITO in a thickness of 1,000 Å was washed, then ultrasonic cleaned with a solvent, such as isopropyl alcohol, acetone, and methanol, and dried.

After HI-1 as a hole injection material was thermally deposited in vacuum in a thickness of 100 nm above the provided ITO transparent electrode, HT-1 as a hole transport material was thermally deposited in vacuum in a thickness of 350 nm. Then, in an emission material layer, GD1 as a dopant and a mixture of GHH1 and GEH1 as hosts (GHH1:GEH1=7:3, based on the weight) were used, a doping concentration of the dopant was 10%, and the thickness of the emission material layer was 400 nm. Subsequently, after ET-1 and Liq compounds as materials for an electron transport layer and an electron injection layer, respectively, were thermally deposited in vacuum, aluminum of 100 nm was deposited to form a cathode, and thus an organic OLED was manufactured.

The materials used in Example 1 are as follows.

Comparative Examples 1 to 5 and Examples 2 to 200

OLEDs of Comparative Examples 1 to 5 and Examples 2 to 200 were manufactured in the same manner as Example 1, except that the dopant materials and host materials shown in Tables 1 to 15 below were used in Example 1. Comparative Examples 1 to 5 each used “CBP” (4,4′-Bis(N-carbazolyl)-1,1′-biphenyl) as the sole type with a structure below for the host of the emission material layer.

EXPERIMENTAL EXAMPLE

The OLEDs manufactured in Examples 1 to 200 and Comparative Examples 1 to 5 were each connected to an external power source, and element characteristics were evaluated at room temperature using a current source and a photometer.

Specifically, a driving voltage (V), external quantum efficiency (EQE), and lifetime (LT95) characteristics were measured with a current of 10 mA/cm2, and measured values of Examples 1 to 200 were calculated as relative values (percentage, %) for any one of Comparative Examples 1 to 5, and the results are shown in Tables 1 to 15 below.

LT95 lifetime indicates the time it takes for an OLED to lose 5% of an initial brightness. LT95 is the most difficult element characteristic specification to meet, and whether an image burn-in phenomenon occurs in an OLED is determined using LT95.

emission material layer
voltage
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As can be seen from the results of Tables 1 to 15, it could be seen that the OLEDs that adopted the organometallic compound satisfying the structure represented by Chemical Formula 1 of the present disclosure used in Examples 1 to 200 as the dopant of the emission material layer and adopted the mixture of the compound represented by Chemical Formula 2 and the compound represented by Chemical Formula 3 as the hosts had low driving voltages and increased external quantum efficiency (EQE) and lifetime (LT95) compared to the OLEDs of Comparative Examples 1 to 5 that used the single material as the host.

In the organic light emitting diode (OLED) according to the present disclosure, by adopting the organometallic compound represented by Chemical Formula 1 as the phosphorous dopant and adopting a mixture of a compound represented by Chemical Formula 2 and a compound represented by Chemical Formula 3 as the phosphorous host, it is possible to improve the efficiency and lifetime characteristics and secure the low-power characteristics by decreasing the driving voltage.

The effects obtainable from the present disclosure are not limited to the above-described effects, and other effects that are not mentioned will be able to be clearly understood by those skilled in the art to which the present disclosure pertains from the following description.

Although the embodiments of the present specification have been described in more detail with reference to the accompanying drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be carried out without departing from the technical spirit of the present specification. Therefore, the embodiments disclosed in the present specification are not intended to limit the technical spirit of the present specification, but are intended to describe the same, and the scope of the technical spirit of the present specification is not limited by these embodiments. Therefore, it should be understood that the above-described embodiments are illustrative and not restrictive in all aspects.

DESCRIPTION OF REFERENCE NUMERALS