Patent Publication Number: US-2023136207-A1

Title: Organometallic compound, organic light-emitting device including organometallic compound, and electronic apparatus including organic light-emitting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority to Korean Patent Application No. 10-2021-0127542, filed on Sep. 27, 2021, in the Korean Intellectual Property Office, and all benefits under 35 U.S.C. § 119, the content of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to an organometallic compound, an organic light-emitting device including the organometallic compound, and an electronic apparatus including the organic light-emitting device. 
     2. Description of the Related Art 
     Organic light-emitting devices (OLEDs) are self-emissive devices which produce full-color images. In addition, OLEDs have wide viewing angles and exhibit excellent driving voltage and response speed characteristics. 
     OLEDs include an anode, a cathode, and an organic layer located between the anode and the cathode and including an emission layer. A hole transport region may be located between the anode and the emission layer, and an electron transport region may be located between the emission layer and the cathode. Holes provided from the anode may move toward the emission layer through the hole transport region, and electrons provided from the cathode may move toward the emission layer through the electron transport region. The holes and the electrons recombine in the emission layer to produce excitons. The excitons may transition from an excited state to a ground state, thus generating light. 
     SUMMARY 
     Provided are an organometallic compound, an organic light-emitting device including the organometallic compound, and an electronic apparatus including the organic light-emitting device. 
     Additional aspects will be set forth in part in the detailed description which follows and, in part, will be apparent from the detailed description, or may be learned by practice of the presented exemplary embodiments of the present disclosure. 
     According to an aspect, an organometallic compound is represented by Formula 1: 
       M 1 (Ln 1 ) n1 (Ln 2 ) n2    Formula 1
 
     wherein, in Formula 1, 
     M 1  is a transition metal, 
     Ln 1  is a ligand represented by Formula 1A, 
     Ln 2  is a ligand represented by Formula 1B, 
     n1 is 1 or 2, and 
     n2 is 1 or 2: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 1A and 1B, 
     X 1  is C or N, and X 2  is C or N, 
     CY 1  and CY 2  are each independently a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group, 
     CY 3  is a 6-membered N-containing heterocyclic group, a 6-membered N-containing heterocyclic group condensed with a C 5 -C 30  carbocyclic group, or a 6-membered N-containing heterocyclic group condensed with a C 1 -C 30  heterocyclic group, 
     CY 41  is a 5-membered carbocyclic group or a 5-membered heterocyclic group, 
     R 10 , R 20  to R 30 , and R 40  to R 42  are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10 , heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 2 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkyl aryl group, a substituted or unsubstituted C 7 -C 60  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 1 )(Q 2 )(Q 3 ), —Ge(Q 1 )(Q 2 )(Q 3 ), —N(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(Q 8 )(Q 9 ), or —P(═O)(Q 8 )(Q 9 ), 
     two or more of a plurality of R 10 (s) are optionally bonded together to form a substituted or unsubstituted C 5 -C 30  carbocyclic group or a substituted or unsubstituted C 1 -C 30  heterocyclic group, 
     two or more of a plurality of R 20 (s) are optionally bonded together to form a substituted or unsubstituted C 5 -C 30  carbocyclic group or a substituted or unsubstituted C 1 -C 30  heterocyclic group, 
     two or more of a plurality of R 30 (s) are optionally bonded together to form a substituted or unsubstituted C 5 -C 30  carbocyclic group or a substituted or unsubstituted C 1 -C 30  heterocyclic group, 
     two or more of a plurality of R 40 (s) are optionally bonded together to form a substituted or unsubstituted C 5 -C 30  carbocyclic group or a substituted or unsubstituted C 1 -C 30  heterocyclic group, 
     two or more adjacent groups of R 10 , R 20 , R 30 , and R 40  to R 42  are optionally bonded together to form a substituted or unsubstituted C 5 -C 30  carbocyclic group or a substituted or unsubstituted C 1 -C 30  heterocyclic group, 
     b10, b20, and b30 are each independently 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, 
     b40 is 1, 2, 3, 4, 5, or 6, and 
     at least one substituent of the substituted C 5 -C 30  carbocyclic group, the substituted C 1 -C 30  heterocyclic group, the substituted C 1 -C 60  alkyl group, the substituted C 2 -C 60  alkenyl group, the substituted C 2 -C 60  alkynyl group, the substituted C 1 -C 60  alkoxy group, the substituted C 1 -C 60  alkylthio group, the substituted C 3 -C 10  cycloalkyl group, the substituted C 1 -C 10  heterocycloalkyl group, the substituted C 3 -C 10  cycloalkenyl group, the substituted C 1 -C 10  heterocycloalkenyl group, the substituted C 6 -C 60  aryl group, the substituted C 7 -C 60  alkyl aryl group, the substituted C 7 -C 60  aryl alkyl group, the substituted C 6 -C 60  aryloxy group, the substituted C 6 -C 60  arylthio group, the substituted C 1 -C 60  heteroaryl group, the substituted C 2 -C 60  alkyl heteroaryl group, the substituted C 2 -C 60  heteroaryl alkyl group, the substituted F heteroaryloxy group, the substituted C 1 -C 60  heteroarylthio group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is: 
     deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 11 )(Q 12 )(Q 13 ), —Ge(C) 11 )(Q 12 )(Q 13 ), —N(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), —P(Q 18 )(Q 19 ), —P(═O)(Q 18 )(Q 19 ), or a combination thereof; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 7 -C 60  aryl alkyl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 2 -C 60  heteroaryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 21 )(Q 22 )(Q 23 ), —Ge(Q 21 )(Q 22 )(Q 23 ), —N(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(Q 28 )(Q 29 ), —P(═O)(Q 28 )(Q 29 ), or a combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —Ge(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), —P(Q 38 )(Q 39 ), or —P(═O)(Q 38 )(Q 39 ), 
     wherein Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkyl aryl group, a substituted or unsubstituted C 7 -C 60  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     According to another aspect, an organic light-emitting device includes: a first electrode; a second electrode; and an organic layer located between the first electrode and the second electrode, wherein the organic layer includes an emission layer, and wherein the organic layer further includes at least one of the organometallic compound. 
     The organometallic compound may be included in the emission layer of the organic layer, and the organometallic compound included in the emission layer may serve as a dopant. 
     According to still another aspect, an electronic apparatus includes the organic light-emitting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other aspects, features, and advantages of certain exemplary embodiments of the disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawing, in which the FIGURE is a schematic cross-sectional view of an organic light-emitting device according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawing, wherein like reference numerals refer to like elements throughout. In this regard, the present exemplary embodiment may have different forms and should not be construed as being limited to the detailed descriptions set forth herein. Accordingly, the exemplary embodiments are merely described below, by referring to the figure, to explain particular aspects. 
     The terminology used herein is for the purpose of describing one or more exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “or” means “and/or.” It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present embodiments. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly in contact with the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this general inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within±30%, 20%, 10%, 5% of the stated value. 
     According to an aspect, an organometallic compound is represented by Formula 1. 
       M 1 (Ln 1 ) n1 (Ln 2 ) n2    Formula 1
 
     wherein, in Formula 1, M 1  is a transition metal. 
     In one or more embodiments, M 1  may be a first-row transition metal of the Periodic Table of Elements, a second-row transition metal of the Periodic Table of Elements, or a third-row transition metal of the Periodic Table of Elements. 
     In one or more embodiments, M 1  may be iridium (Ir), platinum (Pt), osmium (Os), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), thulium (Tm), or rhodium (Rh). 
     In one or more embodiments, M 1  may be Ir, Pt, Os, or Rh. 
     In one or more embodiments, M 1  may be Ir. 
     In Formula 1, n1 is 1 or 2, and n2 is 1, 2, or 3. 
     In one or more embodiments, a sum of n1 and n2 may be 2 or 3 (i.e., n1+n2 may be 2 or 3). 
     In one or more embodiments, M 1  may be Ir, and a sum of n1 and n2 may be 2 or 3 (i.e., n1+n2 may be 2 or 3). 
     In one or more embodiments, M 1  may be Pt, and a sum of n1 and n2 may be 2 (i.e., n1+n2 may be 2). 
     In Formula 1, Ln 1  is a ligand represented by Formula 1A: 
     
       
         
         
             
             
         
       
     
     In Formula 1, Ln 2  is a ligand represented by Formula 1B: 
     
       
         
         
             
             
         
       
     
     In Formula 1A, X 1  is C or N, and X 2  is C or N. 
     In Formula 1A, CY 1  and CY 2  are each independently a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group. 
     In one or more embodiments, CY 1  may be i) a first ring, ii) a second ring, iii) a condensed ring in which at least two first rings are condensed, iv) a condensed ring in which at least two second rings are condensed, or v) a condensed ring in which at least one first ring and at least one second ring are condensed, 
     wherein the first ring may be a cyclopentane group, a cyclopentadiene group, a furan group, a thiophene group, a pyrrole group, a silole group, an indene group, a benzofuran group, a benzothiophene group, an indole group, a benzosilole group, an oxazole group, an isoxazole group, an oxadiazole group, an isoxadiazole group, an oxatriazole group, an isoxatriazole group, a thiazole group, an isothiazole group, a thiadiazole group, an iso-thiadiazole group, a thiatriazole group, an isothiatriazole group, a pyrazole group, an imidazole group, a triazole group, a tetrazole group, an azasilole group, a diazasilole group, or a triazasilole group, and 
     the second ring may be an adamantane group, a norbornane group, a norbornene group, a cyclohexane group, a cyclohexene group, a benzene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, or a triazine group. 
     In one or more embodiments, CY 1  and CY 2  may each independently be a cyclopentane group, a cyclohexane group, a cycloheptane group, a cyclopentene group, a cyclohexene group, a cycloheptene group, a benzene group, a naphthalene group, an anthracene group, a phenanthrene group, a triphenylene group, a pyrene group, a chrysene group, a cyclopentadiene group, a 1,2,3,4-tetrahydronaphthalene group, a thiophene group, a furan group, an indole group, a benzoborole group, a benzophosphole group, an indene group, a benzosilole group, a benzogermole group, a benzothiophene group, a benzoselenophene group, a benzofuran group, a carbazole group, a dibenzoborole group, a dibenzophosphole group, a fluorene group, a dibenzosilole group, a dibenzogermole group, a dibenzothiophene group, a dibenzoselenophenegroup, a dibenzofuran group, a dibenzothiophene 5-oxide group, a 9H-fluoren-9-one group, a dibenzothiophene 5,5-dioxide group, an azaindole group, an azabenzoborole group, an azabenzophosphole group, an azaindene group, an azabenzosilole group, an azabenzogermole group, an azabenzothiophene group, an azabenzoselenophene group, an azabenzofuran group, an azacarbazole group, an azadibenzoborole group, an azadibenzophosphole group, an azafluorene group, an azadibenzosilole group, an azadibenzogermole group, an azadibenzothiophene group, an azadibenzoselenophene group, an azadibenzofuran group, an azadibenzothiophene 5-oxide group, an aza-9H-fluoren-9-one group, an azadibenzothiophene 5,5-dioxide group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a pyrrole group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isooxazole group, a thiazole group, an isothiazole group, an oxadiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzothiazole group, a benzoxadiazole group, a benzothiadiazole group, a 5,6,7,8-tetrahydroisoquinoline group, or a 5,6,7,8-tetrahydroquinoline group. 
     In one or more embodiments, CY 1  and CY 2  may each independently be a benzene group, a naphthalene group, a 1,2,3,4-tetrahydronaphthalene group, a phenanthrene group, a pyridine group, a pyrimidine group, a pyrazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a benzofuran group, a benzothiophene group, a fluorene group, a carbazole group, a dibenzofuran group, a dibenzothiophene group, a dibenzosilole group, an azafluorene group, an azacarbazole group, an azadibenzofuran group, an azadibenzothiophene group, or an azadibenzosilole group. 
     In one or more embodiments, CY 1  may be a pyridine group, a pyrimidine group, a pyrazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, or a quinazoline group. 
     In one or more embodiments, CY 2  may be a benzene group, a naphthalene group, a pyridine group, a pyrimidine group, a pyrazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a fluorene group, a carbazole group, a dibenzofuran group, a dibenzothiophene group, or a dibenzosilole group. 
     In Formula 1B, CY 3  is a 6-membered N-containing heterocyclic group, a 6-membered N-containing heterocyclic group condensed with a C 5 -C 30  carbocyclic group, or a 6-membered N-containing heterocyclic group condensed with a C 1 -C 30  heterocyclic group. 
     In one or more embodiments, CY 3  may be a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a benzoquinoline group, a benzoisoquinoline group, a phenanthroline group, a quinoxaline group, or a quinazoline group. 
     In Formula 1B, CY 41  is a 5-membered carbocyclic group or a 5-membered heterocyclic group. 
     In one or more embodiments, CY 41  may be a cyclopentadiene group, a furan group, a thiophene group, a selenophene group, a pyrrole group, a borole group, an oxazole group, a thiazole group, a selenazole group, an imidazole group, an azaborole group, an oxaborole group, a thiaborole group, a selenaborole group, or a diborole group. 
     In one or more embodiments, in Formula 1A, CY 1  may be represented by one of Formulae 1-1 to 1-16: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 1-1 to 1-16, 
     R 11  to R 14  may each independently be understood by referring to the description of R 10  provided herein, provided that R 11  to R 14  may not each be hydrogen, and 
     * indicates a binding site to M 1 , and 
     *′ indicates a binding site to an adjacent atom. 
     In one or more embodiments, in Formula 1A, CY 2  may be represented by one of Formulae 2-1 to 2-16: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 2-1 to 2-16, 
     R 21  to R 24  may each independently be understood by referring to the description of R 20  provided herein, provided that R 21  to R 24  may not each be hydrogen, and 
     * indicates a binding site to M 1 , and 
     *″ indicated a binding site to an adjacent atom. 
     In one or more embodiments, in Formula 1 B, CY 3  may be represented by one of Formulae 3-1 to 3-16: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 3-1 to 3-16, 
     R 31  to R 34  may each independently be understood by referring to the description of R 30  provided herein, provided that R 31  to R 34  may not each be hydrogen, and 
     * indicates a binding site to M 1 , and 
     *′ indicates a binding site to an adjacent atom. 
     In Formula 1, R 10 , R 20 , R 30 , and R 41  to R 50  are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 2 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkyl aryl group, a substituted or unsubstituted C 7 -C 60  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(Q 8 )(Q 9 ), or —P(═O)(Q 8 )(Q 9 ). 
     In Formula 1, b10, b20, and b30 are each independently 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10. 
     In one or more embodiments, b10, b20, and b30 may each independently be 1, 2, 3, 4, 5, 6, 7, or 8. 
     In one or more embodiments, b10, b20, and b30 may each independently be 1, 2, 3, or 4. 
     In one or more embodiments, b10, b20, and b30 may each independently be 1 or 2. 
     In one or more embodiments, b10, b20, and b30 may each independently be 1. 
     In one or more embodiments, R 10 , R 20 , R 30 , and R 40  to R 42  may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2,  a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF 5 , C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, or a C 1 -C 20  alkylthio group; 
     a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, or a C 1 -C 20  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbomanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a benzene group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbomanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a benzene group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a qjinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzolhiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, or an imidazopyrimidinyl group; 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbomanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a benzene group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a qjinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzolhiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, or an imidazopyrimidinyl group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 1 -C 20  alkylthio group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a benzene group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, or a combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ), —Ge(Q 1 )(Q 2 )(Q 3 ), —N(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(Q 8 )(Q 9 ), or —P(═O)(Q 8 )(Q 9 ). 
     In one or more embodiments, R 10 , R 20 , R 30 , and R 40  to R 42  may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 20  alkylthio group; or 
     a group represented by one of Formulae 9-1 to 9-61, 9-201 to 9-237, 10-1 to 10-129, or 10-201 to 10-350: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 9-1 to 9-61, 9-201 to 9-237, 10-1 to 10-129, and 10-201 to 10-350, * represents a binding site to an adjacent atom, “Ph” represents a benzene group, “TMS” represents a trimethylsilyl group, and “TMG” represents a trimethylgermyl group. 
     In Formulae 1A and 1B, two or more of a plurality of R 10 (s); two or more of a plurality of R 20 (s); two or more of a plurality of R 30 (s); and two or more adjacent groups of R 10 , R 20 , and R 30  are optionally bonded together to form a substituted or unsubstituted C 5 -C 30  carbocyclic group or a substituted or unsubstituted C 1 -C 30  heterocyclic group. 
     In one or more embodiments, two or more of a plurality of R 10 (s); two or more of a plurality of R 20 (s); two or more of a plurality of R 30 (s); and two or more adjacent groups of R 10 , R 20 , and R 30  may optionally be bonded together to form, via a single bond, a double bond, or a first linking group, a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a  (e.g., a fluorene group, a xanthene group, or an acridine group, each unsubstituted or substituted with at least one R 10a ). R 10a  may be understood by referring to the description of R 10  provided herein. 
     The first linking group may be *—N(R 8 )—*′, *—B(R 8 )—*′, *—P(R 8 )—*′, *—C(R 8 )(R 9 )—*′, *—Si(R 8 )(R 9 )—*′, *—Ge(R 8 )(R 9 )—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O) 2 —*′, *—C(R 8 )═*′, *═C(R 8 )—*′, *—C(R 8 )═C(R 9 )—*′, *—C(═S)—*′, and *—CEC—*′, wherein R 8  and R 9  may each be understood by referring to the description of R 10  provided herein, and * and *′ may each be a binding site to an adjacent atom. 
     In one or more embodiments, Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  may each independently be: 
     deuterium, —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CH 2 CH 3 , —CH 2 CD 3 , —CH 2 CD 2 H, —CH 2 CDH 2 , —CHDCH 3 , —CHDCD 2 H, —CHDCDH 2 , —CHDCD 3 , —CD 2 CD 3 , —CD 2 CD 2 H, or —CD 2 CDH 2 , 
     an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an iso-pentyl group, a sec-pentyl group, a tert-pentyl group, a benzene group, or a naphthyl group; or 
     an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tent-butyl group, an n-pentyl group, an iso-pentyl group, a sec-pentyl group, a tent-pentyl group, a benzene group, or a naphthyl group, each substituted with at least one of deuterium, a C 1 -C 10  alkyl group, a benzene group, or a combination thereof. 
     In one or more embodiments, Ln 2  may be represented by Formula 21-1 or Formula 21-2: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 21-1 and 21-2, 
     CY 3 , R 30 , R 41 , R 42 , and b30 may respectively be understood by referring to the descriptions of CY 3 , R 30 , R 41 , R 42 , and b30 provided herein, 
     X 41  may be N, B, or C(R 44 ), 
     X 42  may be O, S, Se, N(R 45 ), B(R 46 ), or C(R 45 )(R 46 ), 
     R 43  to R 46  may each independently be understood by referring to the description of R 40  provided herein, and 
     * and *′ each indicate a binding site to M 1 . 
     In one or more embodiments, the organometallic compound may be a compound represented by Formula 31-1 or Formula 31-2: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 31-1 and 31-2, 
     M 1 , n1, n2, R 41 , and R 42  may respectively be understood by referring to the descriptions of M 1 , n1, n2, R 41 , and R 42  provided herein, 
     X 11  may be C(R 11 ) or N, X 12  may be C(R 12 ) or N, X 13  may be C(R 13 ) or N, and X 14  may be C(R 14 ) or N, 
     X 21  may be C(R 21 ) or N, X 22  may be C(R 22 ) or N, X 23  may be C(R 23 ) or N, and X 24  may be C(R 24 ) or N, 
     X 31  may be C(R 31 ) or N, X 32  may be C(R 32 ) or N, X 33  may be C(R 33 ) or N, and X 34  may be C(R 34 ) or N, 
     X 41  may be N, B, or C(R 44 ), 
     X 42  may be O, S, Se, N(R 45 ), B(R 46 ), or C(R 45 )(R 46 ), 
     R 11  to R 14  may each independently be understood by referring to the description of R 10  provided herein, 
     R 21  to R 24  may each independently be understood by referring to the description of R 20  provided herein, 
     R 31  to R 34  may each independently be understood by referring to the description of R 30  provided herein, 
     R 43  to R 46  may each independently be understood by referring to the description of R 40  provided herein, 
     at least two of R 11  to R 14  may optionally be bonded together to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     at least two of R 21  to R 24  may optionally be bonded together to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     at least two of R 31  to R 34  may optionally be bonded together to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , and 
     R 10a  may be understood by referring to the description of R 10  provided herein. 
     In one or more embodiments, examples of the ″C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a ″ include a benzene group, a naphthalene group, a cyclopentane group, a cyclopentadiene group, a cyclohexane group, a cycloheptane group, a bicyclo[2.2.1]heptane group, a furan group, a thiophene group, a pyrrole group, a silole group, an indene group, a benzofuran group, a benzothiophene group, an indole group, or a benzosilole group, each unsubstituted or substituted with at least one R 10a . R 10a  may be understood by referring to the description of R 10  provided herein. The C 5 -C 30  carbocyclic group and the C 1 -C 30  heterocyclic group may respectively be understood by referring to the descriptions of the C 5 -C 30  carbocyclic group and the C 1 -C 30  heterocyclic group provided herein. 
     In one or more embodiments, at least one of R 10 (s) in the number of b10, R 20 (s) in the number of b20, R 30 (s) in the number of b30, R 30 (s) in the number of b40, R 41 , and R 42  may be a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tent-butyl group, an n-pentyl group, an isopentyl group, a 2-methylbutyl group, a sec-pentyl group, a tert-pentyl group, a neo-pentyl group, a 3-pentyl group, a 3-methyl-2-butyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a benzene group, a biphenyl group, a C 1 -C 20  alkylphenyl group, a naphthyl group, —Si(Q 1 )(Q 2 )(Q 3 ), or —Ge(Q 1 )(Q 2 )(Q 3 ), each unsubstituted or substituted with deuterium. 
     In one or more embodiments, the ligand represented by Formula 1A may include a silyl group ora germyl group, and the ligand represented by Formula 1B may not include a silyl group or a germyl group. 
     In one or more embodiments, the organometallic compound may be represented by one or more of Compounds 1 to 132: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In one or more embodiments, the organometallic compound may be electrically neutral. 
     The organometallic compound represented by Formula 1 may satisfy Formula 1, and the ligand represented by Formula 1B may include a benzene group, to which CY 41 , which is a 5-membered carbocyclic group or a 5-membered heterocyclic group, is condensed. Due to this structure, the organometallic compound represented by Formula 1 may have improved emission characteristics. In particular, the organometallic compound may have suitable characteristics for use in high colorimetric purity emission material by controlling emission wavelength. 
     In addition, the organometallic compound represented by Formula 1 may have excellent electrical mobility. Thus, an electronic device including the organometallic compound, e.g., an organic light-emitting device may have a low driving voltage, high efficiency, long lifespan, and reduced occurrence of roll-off. 
     In addition, the organometallic compound represented by Formula 1 may have improved photochemical stability. Thus, and electronic device, e.g., an organic light-emitting device, including the organometallic compound may have improved emission efficiency, lifespan, and colorimetric purity. 
     The highest occupied molecular orbital (HOMO) energy level, lowest unoccupied molecular orbital (LUMO) energy level, lowest singlet (S 1 ) energy level, and lowest triplet (T 1 ) energy level of organometallic compounds represented by Formula 1 were evaluated by density functional theory (DFT) using Gaussian 09 that performs molecular structure optimizations at a degree of B3LYP. The results thereof are shown in Table 1, where the energy levels are reported as electron Volts (eV). 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 HOMO 
                 LUMO 
                 S 1   
                 T 1   
               
               
                   
                 Compound 
                 (eV) 
                 (eV) 
                 (eV) 
                 (eV) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Compound 1 
                 −4.857 
                 −1.365 
                 2.859 
                 2.420 
               
               
                   
                 Compound 25 
                 −4.798 
                 −1.199 
                 2.862 
                 2.573 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
         
             
             
         
       
     
     Referring to the results of Table 1, the organometallic compound represented by Formula 1 was found to have suitable electrical characteristics for use as a dopant in an electronic device, e.g., an organic light-emitting device. 
     In one or more embodiments, a full width at half maximum (FWHM, nm) in the photoluminescence (PL) spectrum and/or electroluminescence (EL) spectrum of the organometallic compound may be 70 nanometers (nm) or less. For example, a FWHM in the PL spectrum and/or EL spectrum of the organometallic compound may be in a range of about 30 nm to about 65 nm, about 40 nm to about 63 nm, or about 45 nm to about 62 nm. 
     A maximum emission wavelength (emission peak maximum wavelength, λ max ) in the photoluminescence spectrum or electroluminescence spectrum of the organometallic compound may be in a range of about 490 nm to about 550 nm. 
     A method of synthesizing the organometallic compound represented by Formula 1 may be apparent to one of ordinary skill in the art by referring to Synthesis Examples provided herein. 
     The organometallic compound represented by Formula 1 may be suitable for use in an organic layer of an organic light-emitting device, e.g., as a dopant in an emission layer of the organic layer. Thus, according to another aspect, there is provided an organic light-emitting device that may include a first electrode; a second electrode; and an organic layer between the first electrode and the second electrode, wherein the organic layer includes an emission layer and at least one organometallic compound represented by Formula 1. 
     As the organic light-emitting device may include an organic layer including the organometallic compound represented by Formula 1, the organic light-emitting device may have excellent driving voltage, current efficiency, power efficiency, external quantum yield, lifespan, and/or colorimetric purity characteristics. In addition, occurrence of roll-off may be reduced, and thus, a relatively narrow FWHM in the EL spectrum emission peak may be shown. 
     The organometallic compound represented by Formula 1 may be used in a pair of electrodes of an organic light-emitting device. For example, the organometallic compound represented by Formula 1 may be included in the emission layer. In this embodiment, the organometallic compound may serve as a dopant and the emission layer may further include a host (that is, an amount of the organometallic compound represented by Formula 1 may be smaller than that of the host in the emission layer). 
     In one or more embodiments, the emission layer may emit green light. In one or more embodiments, the emission layer may emit green light having a maximum emission wavelength in a range of about 490 nm to about 550 nm. 
     As used herein, “(for example, the organic layer) including at least one organometallic compound” means that “(the organic layer) including an organometallic compound of Formula 1, or at least two different organometallic compounds of Formula 1”. 
     For example, Compound 1 may only be included in the organic layer as an organometallic compound. In this embodiment, Compound 1 may be included in the emission layer of the organic light-emitting device. In one or more embodiments, Compounds 1 and 2 may be included in the organic layer as organometallic compounds. In this embodiment, Compounds 1 and 2 may both be included in the same layer (for example, both Compounds 1 and 2 may be included in the emission layer). 
     The first electrode may be an anode, which is a hole injection electrode, and the second electrode may be a cathode, which is an electron injection electrode. In one or more embodiments, the first electrode may be a cathode, which is an electron injection electrode, and the second electrode may be an anode, which is a hole injection electrode. 
     For example, in the organic light-emitting device, the first electrode may be an anode, the second electrode may be a cathode, and the organic layer may further include a hole transport region between the first electrode and the emission layer and an electron transport region between the emission layer and the second electrode, wherein the hole transport region may include a hole injection layer, a hole transport layer, an electron blocking layer, a buffer layer, or a combination thereof, and the electron transport region may include a hole blocking layer, an electron transport layer, an electron injection layer, or a combination thereof. 
     The term “organic layer” as used herein refers to a single and/or a plurality of layers between the first electrode and the second electrode in an organic light-emitting device. The “organic layer” may include not only organic compounds but also organometallic complexes including metals. 
     The FIGURE illustrates a schematic cross-sectional view of an organic light-emitting device  10  according to one or more embodiments. Hereinafter, a structure of an organic light-emitting device according to one or more embodiments and a method of manufacturing the organic light-emitting device will be described with reference to the FIGURE. The organic light-emitting device  10  may include a first electrode  11 , an organic layer  15 , and a second electrode  19 , which may be sequentially layered in this stated order. 
     A substrate may be additionally disposed under the first electrode  11  or on the second electrode  19 . The substrate may be a conventional substrate used in organic light-emitting devices, e.g., a glass substrate or a transparent plastic substrate, each having excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and/or water repellency. 
     The first electrode  11  may be produced by depositing or sputtering, onto the substrate, a material for forming the first electrode  11 . The first electrode  11  may be an anode. The material for forming the first electrode  11  may be selected from materials with a high work function for easy hole injection. The first electrode  11  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. The material for forming the first electrode  11  may be indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), or zinc oxide (ZnO). In one or more embodiments, the material for forming the first electrode  11  may be a metal, such as magnesium (Mg), aluminum (Al), silver (Ag), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), or magnesium-silver (Mg—Ag). 
     The first electrode  11  may have a single-layered structure or a multi-layered structure including a plurality of layers. In one or more embodiments, the first electrode  11  may have a triple-layered structure of ITO/Ag/ITO, but embodiments are not limited thereto. 
     The organic layer  15  may be disposed on or located on the first electrode  11 . 
     The organic layer  15  may include a hole transport region, an emission layer, and an electron transport region. 
     The hole transport region may be located between the first electrode  11  and the emission layer. 
     The hole transport region may include a hole injection layer, a hole transport layer, an electron blocking layer, a buffer layer, or a combination thereof. 
     The hole transport region may include a hole injection layer only, or a hole transport layer only. In one or more embodiments, the hole transport region may include a hole injection layer and a hole transport layer which are sequentially stacked on the first electrode  11 . In one or more embodiments, the hole transport region may include a hole injection layer, a hole transport layer, and an electron blocking layer, which are sequentially stacked on the first electrode  11 . 
     When the hole transport region includes a hole injection layer, the hole injection layer may be formed on the first electrode  11  by using one or more suitable methods, such as vacuum deposition, spin coating, casting, and Langmuir-Blodgett (LB) deposition. 
     When a hole injection layer is formed by vacuum deposition, for example, the vacuum deposition may be performed at a deposition temperature in a range of about 100° C. to about 500° C., at a vacuum degree in a range of about 10 −8  torr to about 10 −3  torr, and at a deposition rate in a range of about 0.01 Angstroms per second (Å/sec) to about 100 Å/sec, though the conditions may vary depending on a compound that is used as a hole injection material and a structure and thermal properties of a desired hole injection layer, but conditions for the vacuum deposition are not limited thereto. 
     When a hole injection layer is formed by spin coating, the spin coating may be performed at a coating rate in a range of about 2,000 revolutions per minute (rpm) to about 5,000 rpm, and at a temperature in a range of about 80° C. to 200° C., to facilitate removal of a solvent after the spin coating, though the conditions may vary depending on a compound that is used as a hole injection material and a structure and thermal properties of a desired hole injection layer, but conditions for the spin coating are not limited thereto. 
     The conditions for forming a hole transport layer and an electron blocking layer may be inferred from the conditions for forming the hole injection layer. 
     The hole transport region may include at least one of 4,4′,4″-tris(3-methylphenylphenylarnino)triphenylarnine (m-MTDATA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4′,4″-tris{N-(2-naphthyl)-N-phenylamino}-triphenylamine (2-TNATA), N,N′-di(1-naphthyl)-N,N 1 -diphenylbenzidine (NPB), β-NPB, N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD), spiro-TPD, spiro-NPB, methylated NPB, 4,4′-cyclohexylidene bis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), 4,4′-bis[N,N′-(3-tolyl)amino]-3,3′-dimethylbiphenyl (HMTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecyl benzenesulfonic acid (PANI/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), (polyaniline)/poly(4-styrenesulfonate) (PANI/PSS), a compound represented by Formula 201, a compound represented by Formula 202, or a combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formula 201, Ar 101  and Ar 102  may each independently be: 
     a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, or a pentacenylene group; or 
     a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, or a pentacenylene group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a C 3 -C 10  cycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 7 -C 60  aryl alkyl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 2 -C 60  heteroaryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or a combination thereof. 
     In Formula 201, xa and xb may each independently be an integer from 0 to 5. In one or more embodiments, xa and xb may each independently be 0, 1, or 2. In one or more embodiments, xa may be 1, and xb may be 0, but embodiments are not limited thereto. 
     In Formulae 201 and 202, R 101  to R 108 , R 111  to R 119 , and R 121  to R 124  may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, pentyl group, or a hexyl group), a C 1 -C 10  alkoxy group (e.g., a methoxy group, an ethoxy group, a propoxy group, a butoxy group, ora pentoxy group), or a C 1 -C 10  alkylthio group; 
     a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, or a C 1 -C 10  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, or a combination thereof; 
     a benzene group, a naphthyl group, an anthracenyl group, a fluorenyl group, or a pyrenyl group; or 
     a benzene group, a naphthyl group, an anthracenyl group, a fluorenyl group, or a pyrenyl group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, C 1 -C 10  alkylthio group, or a combination thereof, but embodiments are not limited thereto. 
     In Formula 201, R 109  may be: 
     a benzene group, a naphthyl group, an anthracenyl group, or a pyridinyl group; or 
     a benzene group, a naphthyl group, an anthracenyl group, or a pyridinyl group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 1 -C 20  alkylthio group, a benzene group, a naphthyl group, an anthracenyl group, or a pyridinyl group. 
     In one or more embodiments, the compound represented by Formula 201 may be represented by Formula 201A, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 201A, R 101 , R 111 , R 112 , and R 109  may respectively be understood by referring to the descriptions of R 101 , R 111 , R 112 , and R 109  provided herein. 
     In one or more embodiments, the compounds represented by Formulae 201 and 202 may include one or more of Compounds HT1 to HT20, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The thickness of the hole transport region may be in a range of about 100 Angstroms (Å) to about 10,000 Å, and in one or more embodiments, about 100 Å to about 1,000 Å. When the hole transport region includes at least one of a hole injection layer and a hole transport layer, the thickness of the hole injection layer may be in a range of about 100 Å to about 10,000 Å, and in one or more embodiments, about 100 Å to about 1,000 Å, and the thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, and in one or more embodiments, about 100 Å to about 1,500 Å. When the thicknesses of the hole transport region, the hole injection layer, and the hole transport layer are within any of these ranges, excellent hole transport characteristics may be obtained without a substantial increase in driving voltage. 
     The hole transport region may include a charge generating material as well as the aforementioned materials, to improve conductive properties of the hole transport region. The charge generating material may be substantially homogeneously or non-homogeneously dispersed in the hole transport region. 
     The charge generating material may include, for example, a p-dopant. The p-dopant may include one of a quinone derivative, a metal oxide, and a compound containing a cyano group, but embodiments are not limited thereto. For example, non-limiting examples of the p-dopant include a quinone derivative, such as tetracyanoquinodimethane (TCNQ) or 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ); a metal oxide, such as a tungsten oxide or a molybdenum oxide; or a compound containing a cyano group, such as Compound HT-D1 or Compound F12, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
     
     The hole transport region may further include a buffer layer. 
     The buffer layer may compensate for an optical resonance distance depending on a wavelength of light emitted from the emission layer to improve the efficiency of an organic light-emitting device. 
     An emission layer may be formed on the hole transport region by using one or more suitable methods, such as vacuum deposition, spin coating, casting, or LB deposition. When the emission layer is formed by vacuum deposition or spin coating, vacuum deposition and coating conditions for forming the emission layer may be generally similar to those conditions for forming a hole injection layer, though the conditions may vary depending on a compound that is used. 
     When the hole transport region includes an electron blocking layer, a material for forming the electron blocking layer may be selected from the materials for forming a hole transport region and host materials described herein, but embodiments are not limited thereto. In one or more embodiments, when the hole transport region includes an electron blocking layer, mCP described herein may be used for forming the electron blocking layer. 
     The emission layer may include a host and a dopant, and the dopant may include the organometallic compound represented by Formula 1. 
     The host may include at least one of 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TP Bi), 3-tert-butyl-9,10-di(naphth-2-yl)anthracene (TBADN), 9,10-di(naphthalene-2-yl)anthracene (ADN, also known as “DNA”), 4,4′-bis(N-carbazolyI)-1,1′-biphenyl (CBP), 4,4′-bis(9-carbazolyl)-2,2′-dimethyl-biphenyl (CDBP), N,N′N″-1, 3,5-tricarbazoloylbenzene (TCP), 1,3-bis(carbazol-9-yl)benzene (mCP), Compound H50, Compound H51, or a combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In one or more embodiments, the host may further include a compound represented by Formula 301: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 301, Ar 111  and Ar 112  may each independently be: 
     a phenylene group, a naphthylene group, a phenanthrenylene group, or a pyrenylene group; or 
     a phenylene group, a naphthylene group, a phenanthrenylene group, or a pyrenylene group, each substituted with at least one of a benzene group, a naphthyl group, an anthracenyl group, or a combination thereof. 
     In Formula 301, Ar 113  to Ar 116  may each independently be: 
     a C 1 -C 10  alkyl group, a benzene group, a naphthyl group, a phenanthrenyl group, or a pyrenyl group; or 
     a benzene group, a naphthyl group, a phenanthrenyl group, or a pyrenyl group, each substituted with at least one of a benzene group, a naphthyl group, an anthracenyl group, or a combination thereof. 
     In Formula 301, g, h, i, and j may each independently be an integer from 0 to 4. In one or more embodiments, g, h, i, and j may each independently be 0, 1, or 2. 
     In Formula 301, Ar 113  to Ar 116  may each independently be: 
     a C 1 -C 10  alkyl group substituted with at least one of a benzene group, a naphthyl group, an anthracenyl group, or a combination thereof; 
     a benzene group, a naphthyl group, an anthracenyl group, a pyrenyl group, a phenanthrenyl group, or a fluorenyl group; 
     a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, a phenanthrenyl group, or a fluorenyl group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, a phenanthrenyl group, a fluorenyl group, or a combination thereof; or 
     a moiety represented by: 
     
       
         
         
             
             
         
       
     
     In one or more embodiments, the host may include a compound represented by Formula 302: 
     
       
         
         
             
             
         
       
     
     In Formula 302, Ar 122  to Ar 125  may each be understood by referring to the description of Ar 113  in Formula 301. 
     In Formula 302, Ar 126  and Ar 127  may each independently be a C 1 -C 10  alkyl group, e.g., a methyl group, an ethyl group, or a propyl group. 
     In Formula 302, k and l may each independently be an integer from 0 to 4. In one or more embodiments, k and l may each be 0, 1, or 2. 
     When the organic light-emitting device  10  is a full-color organic light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and a blue emission layer. In one or more embodiments, the emission layer may have a structure in which the red emission layer, the green emission layer, and/or the blue emission layer are layered to emit white light. In one or more embodiments, the structure of the emission layer may vary. 
     When the emission layer includes the host and the dopant, an amount of the dopant may be from a range of about 0.01 parts to about 15 parts by weight based on about 100 parts by weight of the host, but embodiments are not limited thereto. 
     The thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, and in one or more embodiments, about 200 Å to about 600 Å. When the thickness of the emission layer is within any of these ranges, improved luminescence characteristics may be obtained without a substantial increase in driving voltage. 
     Next, an electron transport region may be formed on the emission layer. 
     The electron transport region may include a hole blocking layer, an electron transport layer, an electron injection layer, or a combination thereof. 
     In one or more embodiments, the electron transport region may have a hole blocking layer/an electron transport layer/an electron injection layer structure or an electron transport layer/an electron injection layer structure, but embodiments are not limited thereto. The electron transport layer may have a single-layered structure or a multi-layered structure including two or more different materials. 
     The conditions for forming a hole blocking layer, an electron transport layer, and an electron injection layer may be inferred based on the conditions for forming the hole injection layer. 
     When the electron transport region includes a hole blocking layer, the hole blocking layer may include, for example, at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), or bis(2-methyl-8-quinolinolato-N1,08)-(1,1′-biphenyl-4-olato)aluminum (BAlq), but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
     
     The thickness of the hole blocking layer may be in a range of about 20 Å to about 1,000 Å, and in one or more embodiments, about 30 Å to about 300 Å. When the thickness of the hole blocking layer is within any of these ranges, excellent hole blocking characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport layer may further include at least one of BCP, Bphen, tris(8-hydroxyquinolinato)aluminum (Alq 3 ), BAlq, 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), and 4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ): 
     
       
         
         
             
             
         
       
     
     In one or more embodiments, the electron transport layer may include at least one of Compounds ET1 to ET25, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The thickness of the electron transport layer may be in a range of about 100 Å to about 1,000 Å, and in one or more embodiments, about 150 Å to about 500 Å. When the thickness of the electron transport layer is within any of these ranges, excellent electron transport characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport layer may further include a material containing metal, in addition to the materials described above. 
     The material containing metal may include a Li complex. The Li complex may include, e.g., Compound ET-D1 (LiQ) or Compound ET-D2 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer that facilitates electron injection from the second electrode  19 . 
     The electron injection layer may include at least one of LiF, NaCl, CsF, Li 2 O, BaO, or a combination thereof. 
     The thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, for example, about 3 Å to about 90 Å. When the thickness of the electron injection layer is within any of these ranges, excellent electron injection characteristics may be obtained without a substantial increase in driving voltage. 
     The second electrode  19  may be on the organic layer  15 . The second electrode 19 may be a cathode. A material for forming the second electrode  19  may be a material with a relatively low work function, such as a metal, an alloy, an electrically conductive compound, and a mixture thereof. Examples of the material for forming the second electrode  19  may include lithium (Li), magnesium (Mg), aluminum (Al), silver (Ag), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), and magnesium-silver (Mg—Ag). In one or more embodiments, ITO or IZO may be used to form a transmissive second electrode  19  to manufacture a top emission light-emitting device. In one or more embodiments, the material for forming the second electrode  19  may vary. 
     Hereinbefore the organic light-emitting device  10  has been described with reference to the FIGURE, but embodiments are not limited thereto. 
     According to another aspect, a diagnostic composition may include at least one organometallic compound represented by Formula 1. 
     Since the organometallic compound represented by Formula 1 provides high luminescence efficiency, the diagnostic efficiency of the diagnostic composition that includes the organometallic compound represented by Formula 1 may be excellent. 
     The diagnostic composition may be applied in various ways, such as in a diagnostic kit, a diagnostic reagent, a biosensor, or a biomarker. 
     The term “C 1 -C 60  alkyl group” as used herein refers to a linear or branched saturated aliphatic hydrocarbon monovalent group having 1 to 60 carbon atoms. Examples thereof include a methyl group, an ethyl group, a propyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an iso-amyl group, and a hexyl group. The term “C 1 -C 60  alkylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 60  alkyl group. 
     The term “C 1 -C 60  alkoxy group” as used herein refers to a monovalent group represented by —OA 101  (wherein A 101  is a C 1 -C 60  alkyl group). Examples thereof include a methoxy group, an ethoxy group, and an isopropyloxy group. 
     The term “C 1 -C 60  alkylthio group” as used herein refers to a monovalent group represented by —SA 101′  (wherein A 101′  is a C 1 -C 60  alkyl group). 
     The term “C 2 -C 60  alkenyl group” as used herein refers to a group formed by including at least one carbon-carbon double bond in the middle or at the terminus of the C 2 -C 60  alkyl group. Examples thereof include an ethenyl group, a propenyl group, and a butenyl group. The term “C 2 -C 60  alkenylene group” as used herein refers to a divalent group having the same structure as the C 2 -C 60  alkenyl group. 
     The term “C 2 -C 60  alkynyl group” as used herein refers to a group formed by including at least one carbon-carbon triple bond in the middle or at the terminus of the C 2 -C 60  alkyl group. Examples thereof include an ethenyl group and a propenyl group. The term “C 2 -C 60  alkynylene group” as used herein refers to a divalent group having the same structure as the C 2 -C 60  alkynyl group. 
     The term “C 3 -C 10  cycloalkyl group” as used herein refers to a monovalent monocyclic saturated hydrocarbon group including 3 to 10 carbon atoms. Examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. The term “C 3 -C 10  cycloalkylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkyl group. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent monocyclic group including at least one heteroatom selected from N, O, P, Si, Ge, Se, and S as a ring-forming atom(s) and 1 to 10 carbon atoms as ring forming atom(s). Examples thereof include a tetrahydrofuranyl group and a tetrahydrothiophenyl group. The term “C 1 -C 10  heterocycloalkylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkyl group. 
     The term “C 3 -C 10  cycloalkenyl group” as used herein refers to a monovalent monocyclic group including 3 to 10 carbon atoms and at least one carbon-carbon double bond in its ring, wherein the molecular structure as a whole is non-aromatic. Examples thereof include a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. The term “C 3 -C 10  cycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkenyl group. 
     The term “C 2 -C 10  heterocycloalkenyl group” as used herein refers to a monovalent monocyclic group including at least one heteroatom selected from N, O, P, Si, Ge, Se, and S as a ring-forming atom(s), 2 to 10 carbon atoms as ring forming atoms, and at least one double bond in its ring. Examples of the C 1 -C 10  heterocycloalkenyl group include a 2,3-dihydrofuranyl group and a 2,3-dihydrothiophenyl group. The term “C 2 -C 10  heterocycloalkylene group” as used herein refers to a divalent group having the same structure as the C 2 -C 10  heterocycloalkenyl group. 
     The term “C 6 -C 60  aryl group” as used herein refers to a monovalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms only. The term “C 6 -C 60  arylene group” as used herein refers to a divalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms only. Examples of the C 6 -C 60  aryl group include a benzene group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, and a chrysenyl group. When the C 6 -C 60  aryl group and a C 6 -C 60  arylene group each include at least two rings, the at least two rings may be fused. 
     The term “C 7 -C 60  alkyl aryl group” as used herein refers to a C 6 -C 60  aryl group substituted with at least one C 1 -C 60  alkyl group. The term “C 7 -C 60  aryl alkyl group” as used herein refers to a C 1 -C 60  alkyl group substituted with at least one C 6 -C 60  aryl group. 
     The term “C 1 -C 60  heteroaryl group” as used herein refers to a monovalent group having a heterocyclic aromatic system having at least one heteroatom of N, O, P, and S as a ring-forming atom(s) and 1 to 60 carbon atom(s) as ring-forming atoms. The term “C 1 -C 60  heteroarylene group” as used herein refers to a divalent group having a heterocyclic aromatic system having at least one heteroatom of N, O, P, Si, and S as a ring-forming atom(s) and 1 to 60 carbon atom(s) as ring-forming atoms. Examples of the C 1 -C 60  heteroaryl group include a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, and an isoquinolinyl group. When the C 1 -C 60  heteroaryl group and the C 1 -C 60  heteroarylene group each include at least two rings, the at least two rings may be fused. 
     The term “C 2 -C 60  alkyl heteroaryl group” as used herein refers to a C 1 -C 60  heteroaryl group substituted with at least one C 1 -C 60  alkyl group. The term “C 2 -C 60  heteroaryl alkyl group” as used herein refers to a C 1 -C 60  alkyl group substituted with at least one C 1 -C 60  heteroaryl group. 
     The term “C 6 -C 60  aryloxy group” as used herein refers to —OA 102  (wherein A 102  is a C 6 -C 60  aryl group). The term “C 6 -C 60  arylthio group” as used herein refers to —SA 103  (wherein A 103  is a C 6 -C 60  aryl group). 
     The term “C 1 -C 60  heteroaryloxy group” as used herein indicates —OA 104  (wherein A 104  is a C 1 -C 60  heteroaryl group). The term “C 1 -C 60  heteroarylthio group” as used herein indicates —SA 105  (wherein A 105  is a C 1 -C 60  heteroaryl group). 
     The term “monovalent non-aromatic condensed polycyclic group” as used herein refers to a monovalent group that has two or more condensed rings and only carbon atoms (e.g., the number of carbon atoms may be in a range of 8 to 60) as ring-forming atoms, wherein the molecular structure as a whole is non-aromatic. Examples of the monovalent non-aromatic condensed polycyclic group include a fluorenyl group. The term “divalent non-aromatic condensed polycyclic group” as used herein refers to a divalent group having substantially the same structure as the monovalent non-aromatic condensed polycyclic group. 
     The term “monovalent non-aromatic condensed heteropolycyclic group” as used herein refers to a monovalent group that has two or more condensed rings and a at least one heteroatom selected from N, O, P, Si, Se, Ge, and S as a ring forming atom(s) and carbon atoms (e.g., the number of carbon atoms may be in a range of 1 to 60) as ring-forming atoms, wherein the molecular structure as a whole is non-aromatic. Examples of the monovalent non-aromatic condensed heteropolycyclic group include a carbazolyl group. The term “divalent non-aromatic condensed heteropolycyclic group” as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed heteropolycyclic group. 
     The term “C 5 -C 30  carbocyclic group” as used herein refers to a saturated or unsaturated cyclic group including 5 to 30 carbon atoms only as ring-forming atoms. The C 5 -C 30  carbocyclic group may be a monocyclic group or a polycyclic group. 
     The term “C 1 -C 30  heterocyclic group” as used herein refers to saturated or unsaturated cyclic group including at least one heteroatom selected from N, O, P, Si, Se, Ge, and S as a ring-forming atom(s) and 1 to 30 carbon atom(s) as ring-forming atom(s). The C 1 -C 30  heterocyclic group may be a monocyclic group or a polycyclic group. 
     The term “TMS” as used herein represents *—Si(CH 3 ) 3 , and the term “TMG” as used herein represents *—Ge(CH 3 ) 3 . 
     At least one substituent of the substituted C 5 -C 30  carbocyclic group, the substituted C 1 -C 30  heterocyclic group, the substituted C 1 -C 60  alkyl group, the substituted C 2 -C 60  alkenyl group, the substituted C 2 -C 60  alkynyl group, the substituted C 1 -C 60  alkoxy group, the substituted C 1 -C 60  alkylthio group, the substituted C 3 -C 10  cycloalkyl group, the substituted C 1 -C 10  heterocycloalkyl group, the substituted C 3 -C 10  cycloalkenyl group, the substituted C 1 -C 10  heterocycloalkenyl group, the substituted C 6 -C 60  aryl group, the substituted C 7 -C 60  alkyl aryl group, the substituted C 7 -C 60  aryl alkyl group, the substituted C 6 -C 60  aryloxy group, the substituted C 6 -C 60  arylthio group, the substituted C 1 -C 60  heteroaryl group, the substituted C 2 -C 60  alkyl heteroaryl group, the substituted C 2 -C 60  heteroaryl alkyl group, the substituted C 1 -C 60  heteroaryloxy group, the substituted C 1 -C 60  heteroarylthio group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group may be: 
     deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 11 )(Q 12 )(Q 13 ), —Ge(Q 11 )(Q 12 )(Q 13 ), —N(Q 14 )(Q 15 ),—B(Q 16 )(Q 17 ), —P(═O)(Q 18 )(Q 19 ), or a combination thereof; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 7 -C 60  aryl alkyl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 21 )(Q 22 )(Q 23 ), —Ge(Q 21 )(Q 22 )(Q 23 ), —N(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(Q 28 )(Q 29 ), —P(═O)(Q 28 )(Q 29 ), or a combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —Ge(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), —P(Q 38 )(Q 39 ), or —P(═O)(Q 38 )(Q 39 ), 
     wherein Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group ora salt thereof, a sulfonic acid group ora salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkyl aryl group, a substituted or unsubstituted C 7 -C 60  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     Hereinafter, exemplary compounds and organic light-emitting devices according to one or more embodiments will be described in further detail with reference to Synthesis Examples and Examples, however, the present disclosure is not limited thereto. The wording “B was used instead of A” used in describing Synthesis Examples means that an identical molar equivalent of B was used in place of A. 
     EXAMPLES 
     Synthesis Example 1: Synthesis of Compound 1 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     (1) Synthesis of Compound 1A(1) 
     5.2 grams (g) (33.1 millimole (mmol)) of 2-a phenylpyridine and 5.2 g (14.7 mmol) of iridium chloride were mixed with 120 milliliters (mL) of 2-ethoxyethanol and 40 mL of deionized water (DI water). Then, the mixture was stirred under reflux for about 24 hours to carry out a reaction, and then the temperature was allowed to cool to room temperature. A solid formed therefrom was separated by filtration. The solid was washed sufficiently with DI water, methanol, and hexanes in the stated order and dried in a vacuum oven to thereby obtain 8.2 g of Compound 1A (yield: 92%). The resulting Compound 1A was used in the following reaction without any further purification. 
     (2) Synthesis of Compound 1A 
     1.6 g (1.5 mmol) of Compound 1A was mixed with 45 mL of methylene chloride, and a solution, in which 0.8 g (3.1 mmol) of silver trifluoromethanesulfonate (AgOTf) was dissolved in 15 mL of methanol, was added thereto. Then, the mixture was stirred for 18 hours at room temperature while blocking light by using an aluminum foil. The resultant was filtered through CELITE™ to remove a solid formed therefrom and filtered under reduced pressure to thereby obtain a solid (Compound 1A). The solid was used in the following reaction without any further purification. 
     (3) Synthesis of Compound 1B 
     In a nitrogen atmosphere, 1.2 grams (g) (4.8 mmol) of 2-chloro-4-isopropyl pyridine and 3.1 g (7.8 mmol) of 2,4-diphenyl-6-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2-yl)benzo[d]oxazole were dissolved in 90 mL of 1,4-dioxane. Then, 2.3 g (21.2 mmol) of potassium carbonate (K 2 CO 3 ) was dissolved in 40 mL of DI water, followed by addition of the reaction mixture and 0.41 g (0.35 mmol) of a palladium catalyst (tetrakis(triphenylphosphine)palladium(0), Pd(PPh 3 ) 4 ). Then, the resulting mixture was stirred at 110° C. under reflux. The resulting solid underwent flash column chromatography (eluent: ethyl acetate (EA) and hexanes) to thereby obtain 2.1 g of Compound 1A 6-(4-isopropyl pyridin-1-yl)-2,4-diphenylbenzo[d]oxazole (yield: 76%). The resulting compound was identified by high resolution mass spectroscopy (HRMS) using matrix assisted laser desorption ionization (MALDI) and by high-performance liquid chromatography (HPLC) analysis. 
     HRMS (MALDI) calcd for C 27 H 22 N 2 O: m/z: 390.49 Found: 391.37. 
     (4) Synthesis of Compound 1 
     20 mL of 2-ethoxyethanol was mixed with 1.2 g (1.7 mmol) of Compound 1A and 0.7 g (1.9 mmol) of 6-(4-isopropyl pyridin-2-yl)-2,4-diphenylbenzo[d] oxazole. The mixture was stirred under reflux for 24 hours. Then, the temperature was then reduced. The thus obtained mixture was concentrated under reduced pressure by evaporating the solvent to obtain a solid which then was subjected to flash column chromatography (eluent: MC and hexanes) to thereby obtain 0.7 g of Compound 1 (yield: 43%). The resulting compound was identified by HRMS and HPLC analysis. 
     HRMS (MALDI) calcd for C 49 H 37 lrN 4 O: m/z: 890.08 Found: 891.07. 
     Synthesis Example 2: Compound 2 (Representative Synthesis Example) 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     0.6 g of Compound 2 was synthesized in a similar manner as in Synthesis of Compound 1, except that 5-(methyl-d3)-2-phenylpyridine was used instead of 2-phenylpyridine (yield: 38%). The resulting compound was identified by HRMS and HPLC analysis. 
     HRMS (MALDI) calcd for C 51 H 35 D 6 lrN 4 O: m/z: 924.17 Found: 925.31. 
     Example 1 
     A glass substrate, on which ITO is patterned as an anode, was cut to a size of 50 millimeters (mm)×50 mm×0.5 mm, sonicated in isopropyl alcohol and DI water for 5 minutes each, and cleaned by exposure to ultraviolet (UV) rays and ozone for 30 minutes. Subsequently, the ITO-patterned glass substrate was mounted on a vacuum-deposition device. 
     Compound HT3 and Compound F12 (p-dopant) were co-vacuum-deposited on the anode at a weight ratio of 98:2 to form a hole injection layer having a thickness of 100 Å. Compound HT3 was then vacuum-deposited on the hole injection layer to form a hole transport layer having a thickness of 1,650 Å to thereby form a hole transport layer. 
     Subsequently, Compound GH3 (as a host) and Compound 1 (as a dopant) were co-deposited on the hole transport layer at a weight ratio of 92:8 to form an emission layer having a thickness of 400 Å. 
     Compound ET3 and LiQ (n-dopant) were co-deposited at a volume ratio of 50:50 on the emission layer to form an electron transport layer having a thickness of 350 Å, LiQ was vacuum-deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and Al was vacuum-deposited on the electron injection layer to form a cathode having a thickness of 1,000 Å, thereby completing the manufacture of an organic light-emitting device. 
     
       
         
         
             
             
         
       
     
     Example 2 and Comparative Examples 1 to 3 
     Organic light-emitting devices (OLEDs) were manufactured in a similar manner as in Example 1, except that the compounds shown in Table 2 were used instead of Compound 1 as a dopant in the formation of an emission layer. 
     The driving voltage (Volts, V), maximum emission wavelength (λ max , nm) of the emission spectrum, maximum external quantum efficiency (max EQE, relative value), and roll-off ratio (%) of the OLEDs manufactured in Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated. The results thereof are shown in Table 2. A Keithley 2400 current voltmeter and a luminance meter (Minolta Cs-1000A) were used in evaluation. The roll-off ratio was calculated according to Equation 20. 
       Roll-off ratio={1−(efficiency/maximum luminescence efficiency)}×100%   Equation 20
 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Driving 
                   
                   
                   
               
               
                   
                 Molecular 
                 voltage 
                 λ max   
                 Max EQE 
                 Roll-off 
               
               
                 No. 
                 structure 
                 (V) 
                 (nm) 
                 (%) 
                 (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 1 
                 Compound 1 
                 4.5 
                 526 
                 22 
                 14 
               
               
                 Example 2 
                 Compound 2 
                 4.4 
                 527 
                 22 
                 13 
               
               
                 Comparative 
                 Compound A 
                 4.8 
                 529 
                 19 
                 17 
               
               
                 Example 1 
               
               
                 Comparative 
                 Compound B 
                 5.2 
                 522 
                 18 
                 22 
               
               
                 Example 2 
               
               
                 Comparative 
                 Compound C 
                 5.4 
                 509 
                 17 
                 21 
               
               
                 Example 3 
               
               
                   
               
            
           
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Referring to the results of Table 2, the organic light-emitting devices of Examples 1 and 2 were found to have an excellent external quantum efficiency, low driving voltage, and low roll-off ratio. In addition, the organic light-emitting devices of Examples 1 and 2 were each found to have a lower driving voltage and lower roll-off ratio and a higher external quantum efficiency than the organic light-emitting devices of Comparative Examples 1 to 3. 
     The organometallic compound may have excellent electrical characteristics and thermal stability. In particular, crystallization of the organometallic compound may be prevented due to a high glass transition temperature, and electrical mobility may be improved. Accordingly, an electronic device, e.g., an organic light-emitting device, including the organometallic compound may have a low driving voltage, a high efficiency, a long lifespan, a reduced roll-off ratio, and a relatively narrow FWHM of an emission peak in an EL spectrum. 
     Accordingly, by using the organometallic compound, an organic light-emitting device with excellent quality may be realized. In addition, an electronic apparatus including the organic light-emitting device may be provided. 
     It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other exemplary embodiments. While one or more exemplary embodiments have been described with reference to the examples and figure, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.