Patent Publication Number: US-2020287144-A1

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

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Applications No. 10-2019-0026320, filed on Mar. 7, 2019, and 10-2020-0026887, filed on Mar. 4, 2020, in the Korean Intellectual Property Office, the contents of which are incorporated herein in their entirety by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments relate 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 are self-emission devices, which have better characteristics in terms of a viewing angle, response time, brightness, driving voltage, and response speed, and produce full-color images. 
     In an example, an organic light-emitting device includes an anode, a cathode, and an organic layer between the anode and the cathode, wherein the organic layer includes an emission layer. A hole transport region may be between the anode and the emission layer, and an electron transport region may be 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. These excitons transit from an excited state to a ground state, thereby generating light. 
     SUMMARY 
     Aspects of the present disclosure provide 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 description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     An aspect of the present disclosure provides an organometallic compound represented by Formula 1 below: 
       M(L 1 ) n1 (L 2 ) n2 .  Formula 1
 
     In Formula 1, 
     M may be a transition metal, 
     L 1  may be a ligand represented by Formula 2A, 
     L 2  may be a ligand represented by Formula 2B, 
     n1 and n2 may each independently be 1 or 2, wherein, when n1 is 2, two L 1 (s) may be identical to or different from each other and when n2 is 2, two L 2 (S) may be identical to or different from each other, 
     the sum of n1 and n2 may be 2 or 3, and 
     L 1  to L 2  may be different from each other: 
     
       
         
         
             
             
         
       
     
     In Formulae 2A and 2B, 
     Y 1  and Y 4  may each independently be C or N, 
     X 1  may be Si or Ge, 
     X 21  may be O, S, S(═O), N(Z 29 ), C(Z 29 )(Z 30 ), or Si(Z 29 )(Z 30 ), 
     T 1  to T 4  may each independently be C, N, carbon linked to ring CY 1 , or carbon linked to M in Formula 1, wherein one of T 1  to T 4  may be carbon linked to M in Formula 1, and one of the remaining T 1  to T 4  that are not linked to M in Formula 1 may be carbon linked to ring CY 1 , 
     T 5  to T 8  may each independently be C or N, 
     when X 1  is Si, at least one of the remaining T 1  to T 8  that are not carbon linked to M and ring CY 1  may be N, 
     ring CY 1  and ring CY 14  may each independently be a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group, 
     R 21  to R 23  may each independently be a C 1 -C 60  alkyl group or a C 6 -C 60  aryl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 3 -C 10  cycloalkyl group, a phenyl group, or any combination thereof, 
     Z 1 , Z 2 , and R 11  to R 14  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 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 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 monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(═O)(Q 8 )(Q 9 ) or —P(Q 8 )(Q 9 ), wherein R 12  is neither hydrogen nor a methyl group, 
     a1 and b1 may each independently be an integer from 0 to 20, wherein, when a1 is 2 or more, two or more Z 1 (s) may be identical or different, and when b1 is 2 or more, two or more R 14 (s) may be identical or different, 
     a2 may be an integer from 0 to 6, wherein, when a2 is 2 or more, two or more Z 2 (s) may be identical to or different from each other, 
     two or more of R 21  to R 23  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     two or more of a plurality of Z 1 (s) may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     two or more of a plurality of Z 2 (s) may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     R 12  and R 13  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     two or more of a plurality of R 14 (s) may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     two or more of Z 1 , Z 2  and R 11  to R 14  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     R 10a  may be the same as defined in connection with R 14 , 
     * and *′ in Formulae 2A and 2B each indicate a binding site to M in Formula 1, 
     a substituent of 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 2 -C 10  heterocycloalkenyl group, the substituted C 6 -C 60  aryl 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 monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group may each independently be: 
     deuterium, —F, —Cl, —Br, —I, —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, or a C 1 -C 60  alkoxy group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each substituted with deuterium, —F, —Cl, —Br, —I, —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 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Ge(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), —P(═O)(Q 18 )(Q 19 ), —P(Q 18 )(Q 19 ), or any 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 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Ge(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(═O)(Q 28 )(Q 29 ), —P(Q 28 )(Q 29 ), or any combination thereof; 
     —N(Q 31 )(Q 32 ), —Ge(Q 33 )(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), —P(═O)(Q 38 )(Q 39 ) or —P(Q 38 )(Q 39 ); or any combination thereof, 
     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; 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 unsubstituted or substituted with deuterium, a C 1 -C 60  alkyl group, a C 6 -C 60  aryl group, or any combination thereof; a C 2 -C 60  alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; a C 3 -C 10  cycloalkyl group; a C 1 -C 10  heterocycloalkyl group; a C 3 -C 10  cycloalkenyl group; a C 2 -C 10  heterocycloalkenyl group; a C 6 -C 60  aryl group unsubstituted or substituted with deuterium, a C 1 -C 60  alkyl group, a C 6 -C 60  aryl group, or any combination thereof; a C 6 -C 60  aryloxy group; a C 6 -C 60  arylthio group; a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group; or a monovalent non-aromatic condensed heteropolycyclic group. 
     Another aspect of the present disclosure provides an organic light-emitting device including: a first electrode, a second electrode, and an organic layer disposed between the first electrode and the second electrode and including an emission layer, wherein the organic layer including at least one 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 act as a dopant. 
     Another aspect of the present disclosure provides an electronic apparatus including the organic light-emitting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with FIGURE which is a schematic view of an organic light-emitting device according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. 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 when an element is referred to as being “on” another element, it can be directly on 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 
     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 herein. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, “a,” “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to cover both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. 
     “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items 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. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another element as illustrated in the Figures It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the FIGURE Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     “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% or 5% of the stated value. 
     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 disclosure 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. 
     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. 
     An aspect of the present disclosure provides an organometallic compound represented by Formula 1 below: 
       M(L 1 ) n1 (L 2 ) n2 .  Formula 1
 
     M in Formula 1 may be a transition metal. 
     For example, M may be a first-row transition metal, a second-row transition metal, or a third-row transition metal, of the Periodic Table of Elements. 
     For example, M 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 may be Ir, Pt, Os, or Rh. 
     L 1  in Formula 1 may be a ligand represented by Formula 2A, and n1 in Formula 1 indicates the number of L 1 (s) in Formula 1 and may be 1 or 2. When n1 is two, two L 1 (s) may be identical to or different from each other. 
     L 2  in Formula 1 may be a ligand represented by Formula 2B, and n2 in Formula 1 indicates the number of L 2 (s) in Formula 1 and may be 1 or 2. When n2 is two, two L 2 (s) may be identical to or different from each other: 
     
       
         
         
             
             
         
       
     
     Formulae 2A and 2B will be understood by referring to a detailed description thereof to be provided later. 
     L 1  and L 2  in Formula 1 may be different from each other. That is, the organometallic compound represented by Formula 1 may be a heteroleptic complex. 
     In one or more embodiments, M may be Ir, and the sum of n1 and n2 may be 3; or M may be Pt, and the sum of n1 and n2 may be 2. 
     Y 1  and Y 4  in Formulae 2A and 2B may each independently be C or N. 
     For example, Y 1  in Formula 2A may be N and Y 4  in Formula 2B may be C. 
     X 1  in Formula 2B may be Si or Ge. 
     X 21  in Formula 2A may be O, S, S(═O), N(Z 29 ), C(Z 29 )(Z 30 ), or Si(Z 29 )(Z 30 ). Z 29  and Z 30  will be understood by referring to a detailed description thereof to be provided later. 
     For example, X 21  in Formula 2A may be O or S. 
     In Formula 2A, i) T 1  to T 4  may each independently be C, N, carbon linked to ring CY 1 , or carbon linked to M in Formula 1, wherein one of T 1  to T 4  may be carbon linked to M in Formula 1, and one of the remaining T 1  to T 4  that are not linked to M in Formula 1 may be carbon linked to ring CY 1 , and ii) T 5  to T 8  may each independently be C or N. 
     In Formula 1, when X 1  in Formula 2B is Si, at least one of the remaining T 1  to T 8  that are not carbon linked to M and ring CY 1  may be N. 
     In one or more embodiments, X 1  in Formula 2B may be Si, and at least one of the remaining T 1  to T 8  that are not carbon linked to M and ring CY 1  in Formula 2A may be N. 
     In one or more embodiments, X 1  in Formula 2B may be Ge, and T 1  to T 8  in Formula 2A may be C. 
     In one or more embodiments, X 1  in Formula 2B may be Ge, and at least one of the remaining T 1  to T 8  that are not carbon linked to M and ring CY 1  in Formula 2A may be N. 
     In one or more embodiments, T 8  in Formula 2A may be N. 
     Ring CY 1  and ring CY 14  in Formulae 2A and 2B may each independently be a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group. 
     For example, ring CY 1  and ring CY 14  may each independently be i) a first ring, ii) a second ring, iii) a condensed ring in which at least two first rings are condensed with each other, iv) a condensed ring in which at least two second rings are condensed with each other, or v) a condensed ring in which at least one first ring and at least one second ring are condensed with each other. 
     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 isothiadiazole 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. 
     The second ring may be an admantane 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, in Formulae 2A and 2B, ring CY 1  and ring CY 14  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 dibenzoselenophene group, a dibenzofuran group, a dibenzothiophene 5-oxide group, a 9H-fluorene-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-fluorene-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 isoxazole 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, a 5,6,7,8-tetrahydroquinoline group, an admantane group, a norbornane group, or a norbornene group. 
     In one or more embodiments, ring CY 1  and ring CY 14  may each independently be a benzene group, a naphthalene group, 1,2,3,4-tetrahydronaphthalene group, a phenanthrene group, a pyridine group, a pyrimidine group, a pyrazine group, a triazine 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, ring CY 1  in Formula 2A may be a pyridine group, a 5,6,7,8-tetrahydroisoquinoline group, or a 5,6,7,8-tetrahydroquinoline group. 
     In one or more embodiments, ring CY 14  in Formula 2B may be a benzene group, a naphthalene group, 1,2,3,4-tetrahydronaphthalene group, a dibenzothiophene group, a dibenzofuran group, or a pyridine group. 
     In Formula 2B, R 21  to R 23  may each independently be a C 1 -C 60  alkyl group or a C 6 -C 60  aryl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 3 -C 10  cycloalkyl group, a phenyl group, or any combination thereof. 
     For example, R 21  to R 23  in Formula 2B may each independently be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 3 -C 10  cycloalkyl group, a phenyl group, or any combination thereof. 
     In one or more embodiments, R 21  to R 23  may each independently be —CH 3 , —CH 2 CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CH 2 CD 3 , or —CD 2 CH 3 . 
     In one or more embodiments, R 21  to R 23  in Formula 2B may be identical to each other. 
     In one or more embodiments, at least two of R 21  to R 23  may be different from each other. 
     Z 1 , Z 2 , and R 11  to R 14  in Formulae 2A and 2B 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 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 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 monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(═O)(Q 8 )(Q 9 ) or —P(Q 8 )(Q 9 ), and R 12  may be neither hydrogen nor a methyl group. Q 1  to Q 9  may be the same as described in this disclosure. 
     In Formulae 2A and 2B, a1 and b1 indicate the number of Z 1 (s) and the number of R 14 (s), respectively, and may each independently be an integer from 0 to 20. When a1 is two or more, two or more Z 1 (s) may be identical to or different from each other, and when b1 is two or more, two or more R 14 (s) may be identical to or different from each other. For example, a1 and b1 may each independently be an integer from 0 to 10. 
     In Formula 2A, a2 indicates the number of Z 2 (s) and may each independently be an integer from 0 to 6. When a2 is two or more, two or more Z 2 (s) may be identical to or different from each other. For example, a2 may each independently be 0, 1, 2 or 3. 
     In one or more embodiments, Z 1  in Formula 2A may be hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a substituted or unsubstituted C 1 -C 60  alkyl group, or a substituted or unsubstituted C 3 -C 10  cycloalkyl group. 
     In one or more embodiments, in Formula 2A, 
     Z 1  may be: 
     hydrogen, deuterium, —F, or a cyano group; 
     a C 1 -C 20  alkyl group unsubstituted or substituted with deuterium, —F, a cyano group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a (C 1 -C 20  alkyl)C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a deuterated C 1 -C 10  heterocycloalkyl group, a (C 1 -C 20  alkyl)C 1 -C 10  heterocycloalkyl group, or any combination thereof; or 
     a C 3 -C 10  cycloalkyl group or a C 1 -C 10  heterocycloalkyl group, unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 20  alkyl group, a deuterated C 1 -C 20  alkyl group, or any combination thereof. 
     In one or more embodiments, in Formula 2A, 
     Z 1  may be: 
     hydrogen, deuterium, —F, or a cyano group; 
     a C 1 -C 20  alkyl group unsubstituted or substituted with deuterium, —F, a cyano group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, or any combination thereof; or 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, or a bicyclo[2.2.2]octyl group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 20  alkyl group, or any combination thereof. 
     In one or more embodiments, Z 2  and R 11  to R 14  in Formulae 2A and 2B may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, 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 deuterium, —F, —Cl, —Br, —I, —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 norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)cyclopentenyl group, a (C 1 -C 20  alkyl)cyclohexenyl group, a (C 1 -C 20  alkyl)cycloheptenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof; 
     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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl 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, a benzoisothiazolyl group, a benzoxazolyl group, a benzoisoxazolyl 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, an azacarbazolyl group, an azadibenzofuranyl group, or an azadibenzothiophenyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)cyclopentenyl group, a (C 1 -C 20  alkyl)cyclohexenyl group, a (C 1 -C 20  alkyl)cycloheptenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl 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, a benzoisothiazolyl group, a benzoxazolyl group, a benzoisoxazolyl 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, an azacarbazolyl group, an azadibenzofuranyl group, an azadibenzothiophenyl group, or any combination thereof; or 
     —N(Q 1 )(Q 2 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(═O)(Q 8 )(Q 9 ), or —P(Q 8 )(Q 9 ), 
     R 12  may not be hydrogen nor a methyl group, and 
     Q 1  to Q 9  may each independently be: 
     —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 ; or 
     an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, or any combination thereof. 
     In one or more embodiments, a number of carbon included in R 12  of Formula 2B may be at least two. 
     In one or more embodiments, R 12  in Formula 2B may be: 
     a C 2 -C 20  alkyl group or a C 2 -C 20  alkoxy group; 
     a methyl group or a methoxy group, each substituted with a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 2 -C 10  heterocycloalkenyl group, a C 6 -C 14  aryl group, a C 1 -C 14  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or any combination thereof; 
     a C 2 -C 20  alkyl group or a C 2 -C 20  alkoxy group, each substituted with deuterium, —F, —Cl, —Br, —I, —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 C 1 -C 10  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 2 -C 10  heterocycloalkenyl group, a C 6 -C 14  aryl group, a C 1 -C 14  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or any 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 2 -C 10  heterocycloalkenyl group, a C 6 -C 14  aryl group, a C 1 -C 14  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 2 -C 10  heterocycloalkenyl group, a C 6 -C 14  aryl group, a C 1 -C 14  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or any combination thereof; or 
     —N(Q 1 )(Q 2 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), or —P(═O)(Q 8 )(Q 9 ). 
     In one or more embodiments, R 12  in Formula 2B may be: 
     a methyl group or a methoxy group, each substituted with 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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)cyclopentenyl group, a (C 1 -C 20  alkyl)cyclohexenyl group, a (C 1 -C 20  alkyl)cycloheptenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof; 
     a methyl group or a methoxy group, each substituted with i) 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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)cyclopentenyl group, a (C 1 -C 20  alkyl)cyclohexenyl group, a (C 1 -C 20  alkyl)cycloheptenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof, and ii) at least one deuterium; 
     a C 2 -C 20  alkyl group or a C 2 -C 20  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)cyclopentenyl group, a (C 1 -C 20  alkyl)cyclohexenyl group, a (C 1 -C 20  alkyl)cycloheptenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof; or 
     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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl 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, a benzoisothiazolyl group, a benzoxazolyl group, a benzoisoxazolyl 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, an azacarbazolyl group, an azadibenzofuranyl group, or an azadibenzothiophenyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —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 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 bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, a (C 1 -C 20  alkyl)cyclopentyl group, a (C 1 -C 20  alkyl)cyclohexyl group, a (C 1 -C 20  alkyl)cycloheptyl group, a (C 1 -C 20  alkyl)cyclooctyl group, a (C 1 -C 20  alkyl)adamantanyl group, a (C 1 -C 20  alkyl)norbornanyl group, a (C 1 -C 20  alkyl)norbornenyl group, a (C 1 -C 20  alkyl)cyclopentenyl group, a (C 1 -C 20  alkyl)cyclohexenyl group, a (C 1 -C 20  alkyl)cycloheptenyl group, a (C 1 -C 20  alkyl)bicyclo[1.1.1]pentyl group, a (C 1 -C 20  alkyl)bicyclo[2.1.1]hexyl group, a (C 1 -C 20  alkyl)bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl 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, a benzoisothiazolyl group, a benzoxazolyl group, a benzoisoxazolyl 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, an azacarbazolyl group, an azadibenzofuranyl group, an azadibenzothiophenyl group, or any combination thereof. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may satisfy at least one of Condition (1) to Condition (3) below: 
     Condition (1) 
     In Formula 2A, Z 1  is not hydrogen, and a1 is an integer of 1 to 20. 
     Condition (2) 
     In Formula 2B, R 14  is not hydrogen, and b1 is an integer of 1 to 20. 
     Condition (3) 
     In Formula 2A, Z 2  is not hydrogen, and a2 is an integer of 1 to 6. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may include at least one deuterium, at least one fluoro group (—F), at least one cyano group (—CN), or any combination thereof. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may include at least one deuterium. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may satisfy at least one of Condition A to Condition I below: 
     Condition A 
     In Formula 2A, Z 1  is not hydrogen, a1 is an integer of 1 to 20, and at least one of Z 1 (s) in the number of a1 includes deuterium. 
     Condition B 
     In Formula 2A, Z 2  is not hydrogen, a2 is an integer of 1 to 6, and at least one of Z 2 (s) in the number of a2 includes deuterium. 
     Condition C 
     In Formula 2A, Z 2  is not hydrogen, a2 is an integer of 1 to 6, and at least one of Z 2 (s) in the number of a2 includes —F. 
     Condition D 
     In Formula 2A, Z 2  is not hydrogen, a2 is an integer of 1 to 6, and at least one of Z 2 (s) in the number of a2 includes —CN. 
     Condition E 
     In Formula 2A, Z 2  is not hydrogen, a2 is an integer of 1 to 6, and at least one of Z 2 (s) in the number of a2 is a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     Condition F 
     In Formula 2B, at least one of R 21  to R 23  includes deuterium. 
     Condition G 
     In Formula 2B, R 12  includes deuterium. 
     Condition H 
     In Formula 2B, R 14  is not hydrogen, b1 is an integer of 1 to 20, and at least one of R 14 (S) in the number of b1 includes deuterium. 
     Condition I 
     In Formula 2B, R 14  is not hydrogen, b1 is an integer of 1 to 20, and at least one of R 14 (S) in the number of b1 includes —F. 
     In one or more embodiments, Z 2  in Formula 2A may not be hydrogen, a2 may be an integer from 1 to 3, and at least one of Z 2 (s) in number of a2 may each independently be a substituted or unsubstituted C 1 -C 60  alkyl 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 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     In one or more embodiments, Z 2  in Formula 2A may not be hydrogen, a2 may be an integer from 1 to 3, and at least one of Z 2 (s) in number of a2 may each independently be a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     In one or more embodiments, Z 1  in Formula 2A may be hydrogen, deuterium, —F, a cyano group, a nitro group, —SF 5 , —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , —OCH 3 , —OCDH 2 , —OCD 2 H, —OCD 3 , —SCH 3 , —SCDH 2 , —SCD 2 H, —SCD 3 , one of groups represented by Formulae 9-1 to 9-39, one of groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 9-201 to 9-233, one of groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 10-1 to 10-11, one of groups represented by Formulae 10-1 to 10-11 in which at least one hydrogen is substituted with deuterium, or one of groups represented by Formulae 10-1 to 10-11 in which at least one hydrogen is substituted with —F. 
     In one or more embodiments, Z 2  and R 11  to R 14  in Formulae 2A and 2B may each independently be hydrogen, deuterium, —F, a cyano group, a nitro group, —SF 5 , —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , —OCH 3 , —OCDH 2 , —OCD 2 H, —OCD 3 , —SCH 3 , —SCDH 2 , —SCD 2 H, —SCD 3 , one of groups represented by Formulae 9-1 to 9-39, one of groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 9-201 to 9-233, one of groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 10-1 to 10-132, one of groups represented by Formulae 10-1 to 10-132 in which at least one hydrogen is substituted with deuterium, or one of groups represented by Formulae 10-1 to 10-132 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 10-201 to 10-353, one of groups represented by Formulae 10-201 to 10-353 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 10-201 to 10-353 in which at least one hydrogen is substituted with —F, —N(Q 1 )(Q 2 ), or —Ge(Q 3 )(Q 4 )(Q 5 ) (wherein Q 1  to Q 5  are the same as described above). 
     In one or more embodiments, R 12  in Formula 2B may be one of groups represented by Formulae 9-1 to 9-39, one of groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 9-201 to 9-233, one of groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with deuterium, one of groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 10-1 to 10-132, one of groups represented by Formulae 10-1 to 10-132 in which at least one hydrogen is substituted with deuterium, or one of groups represented by Formulae 10-1 to 10-132 in which at least one hydrogen is substituted with —F, one of groups represented by Formulae 10-201 to 10-353, one of groups represented by Formulae 10-201 to 10-353 in which at least one hydrogen is substituted with deuterium, or one of groups represented by Formulae 10-201 to 10-353 in which at least one hydrogen is substituted with —F: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 9-1 to 9-39, 9-201 to 9-233, 10-1 to 10-132 and 10-201 to 10-353, 
     * indicates a binding site to a neighboring atom, 
     Ph indicates a phenyl group, 
     TMS indicates a trimethylsilyl group, 
     TMG indicates a trimethylgermyl group, and 
     OMe indicates a methoxy group. 
     The term “groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with deuterium” and “groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with deuterium” as used herein may be, for example, groups represented by Formulae 9-501 to 9-514 and 9-601 to 9-635: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The term “groups represented by Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with —F” and “groups represented by Formulae 9-201 to 9-233 in which at least one hydrogen is substituted with —F” as used herein may be, for example, groups represented by Formulae 9-701 to 9-710: 
     
       
         
         
             
             
         
       
     
     The term “groups represented by Formulae 10-1 to 10-132 in which at least one hydrogen is substituted with deuterium” and “groups represented by Formulae 10-201 to 10-353 in which at least one hydrogen is substituted with deuterium” as used herein may be, for example, groups represented by Formulae 10-501 to 10-553: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The term “groups represented by Formulae 10-1 to 10-132 in which at least one hydrogen is substituted with —F” and “groups represented by Formulae 10-201 to 10-353 in which at least one hydrogen is substituted with —F” as used herein may be, for example, groups represented by Formulae 10-601 to 10-620: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 2A and 2B, i) two or more of R 21  to R 23  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , ii) two or more of a plurality of Z 1 (s) may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , iii) two or more of a plurality of Z 2 (s) may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , iv) R 12  and R 13  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , v) two or more of a plurality of R 14 (s) may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , and vi) two or more of Z 1 , Z 2  and R 11  to R 14  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a . 
     R 10a  may be the same as defined in connection with R 14  in the present specification. 
     In Formulae 2A and 2B, * and *′ each indicate a binding site to M in Formula 1. 
     In one or more embodiments, the group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 2A may be a group represented by one of Formulae CY1-1 to CY1-28: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY1-1 to CY1-28, 
     Z 11  to Z 14  may each be the same as defined in connection with Z 1 , provided that each of Z 11  to Z 14  are not hydrogen, 
     ring CY 10a  may be a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group, 
     R 10a  may be the same as described above, 
     aa may be an integer from 0 to 10, 
     * indicates a binding site to M in Formula 1, and 
     *″ indicates a binding site to one of T 1  to T 4  in Formula 2A. 
     In one or more embodiments, the group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 2A may be a group represented by one of Formulae CY1-4, CY1-7, CY1-9, CY1-11, CY1-12, and CY1-14 to CY1-24. 
     In one or more embodiments, the group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 2A may be a group represented by one of Formulae CY2-1 to CY2-6: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY2-1 to CY2-6, 
     T 1  to T 8  may each independently be C or N, 
     X 21  may be the same as described above, 
     *″ indicates a binding site to ring CY 1  in Formula 2A, and 
     *′ indicates a binding site to M in Formula 1. 
     For example, 
     a) X 1  in Formula 2B may be Ge, and each of T 1  to T 8  in Formulae CY2-1 to CY2-6 may be C, (and/or) 
     b) X 1  in Formula 2B may be Si or Ge, and at least one of T 3  to T 8  (for example, one or two of T 3  to T 8 ) in Formulae CY2-1 and CY2-6 may be N, (and/or) 
     c) X 1  in Formula 2B may be Si or Ge, and at least one of T 1 , T 2 , and T 5  to T 8  (for example, one or two of T 1 , T 2 , and T 5  to T 8 ) in Formulae CY2-2 and CY2-5 may be N, (and/or) 
     d) X 1  in Formula 2B may be Si or Ge, and at least one of T 1  and T 4  to T 8  (for example, one or two T 1  and T 4  to T 8 ) in Formulae CY2-3 and CY2-4 may be N. 
     In one or more embodiments, 
     1) T 1  to T 8  in Formulae CY2-1 to CY2-6 may be C; 
     2) one of T 3  to T 8  in Formula CY2-1 may be N, and the remaining T 3  to T 8  that are not N in Formula CY2-1 may be C; 
     3) T 3  and T 8  in Formula CY2-1 may be N, and T 4  to T 7  in Formula CY2-1 may be C; 4) T 6  and T 8  in Formula CY2-1 may be N, and T 3  to T 5  and T 7  in Formula CY2-1 may be C; 
     5) one of T 1 , T 2  and T 8  in Formula CY2-2 may be N, and the remaining T 1 , T 2  and T 5  to T 8  that are not N in Formula CY2-2 may be C; 
     6) T 1  and T 8  in Formula CY2-2 may be N, and T 2  and T 5  to T 7  in Formula CY2-2 may be C; 
     7) T 2  and T 8  in Formula CY2-2 may be N, and T 1  and T 5  to T 7  in Formula CY2-2 may be C; 
     8) one of T 1 , T 4  and T 8  in Formulae CY2-3 and CY2-4 may be N, and the remaining T 1 , T 4  and T 5  to T 8  that are not N in Formulae CY2-3 and CY2-4 may be C; 
     9) T 1  and T 8  in Formulae CY2-3 and CY2-4 may be N, and T 4  and T 5  to T 7  in Formulae CY2-3 and CY2-4 may be C; 
     10) T 4  and T 8  in Formulae CY2-3 and CY2-4 may be N, and T 1  and T 5  to T 7  in Formulae CY2-3 and CY2-4 may be C; 
     11) one of T 1  and T 8  in Formula CY2-5 may be N, and the remaining T 1 , T 2  and T 5  to T 8  that are not N in Formula CY2-5 may be C; 
     12) T 1  and T 8  in Formula CY2-5 may be N, and T 2  and T 5  to T 7  in Formula CY2-5 may be C; 
     13) one of T 4  and T 8  in Formula CY2-6 may be N, and the remaining T 3  to T 8  that are not N in Formula CY2-6 may be C; or 
     14) T 4  and T 8  in Formula CY2-6 may be N, and T 3  and T 5  to T 7  in Formula CY2-6 may be C. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 2A may be a group represented by one of Formulae CY2-1001 to CY2-1141, CY2-2001 to CY2-2092, CY2-3001 to CY2-3092, CY2-4001 to CY2-4092, CY2-5001 to CY2-5065 and CY2-6001 to CY2-6065: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY2-1001 to CY2-1141, CY2-2001 to CY2-2092, CY2-3001 to CY2-3092, CY2-4001 to CY2-4092, CY2-5001 to CY2-5065 and CY2-6001 to CY2-6065, 
     X 21  may each be the same as described above, 
     Z 21  to Z 28  may each be the same as defined in connection with Z 2 , provided that each of Z 21  to Z 28  are not hydrogen, 
     *″ indicates a binding site to ring CY 1  in Formula 2A, and 
     *′ indicates a binding site to M in Formula 1. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 2B may be a group represented by one of Formulae CY14-1 to CY14-64: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY14-1 to CY14-64, 
     R 14  may be the same as described above, 
     X 14  may be C(R 1 )(R 2 ), N(R 1 ), O, S, or Si(R 1 )(R 2 ), 
     R 1  to R 8  may each be the same as defined in connection with R 14  in the present specification, 
     b18 may be an integer from 0 to 8, 
     b16 may be an integer from 0 to 6, 
     b15 may be an integer from 0 to 5, 
     b14 may be an integer from 0 to 4, 
     b13 may be an integer from 0 to 3, 
     b12 may be an integer from 0 to 2, 
     *″ indicates a binding site to a carbon atom of a neighboring pyridine ring in Formula 2B, and 
     *′ indicates a binding site to M in Formula 1. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 2B may be a group represented by one of Formulae CY14(1) to CY14(63): 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY14(1) to CY14(63), 
     R 14a  to R 14d  may each the same as defined in connection with R 14 , wherein each of R 14a  to R 14d  may not be hydrogen, 
     X 14  may be C(R 1 )(R 2 ), N(R 1 ), O, S or Si(R 1 )(R 2 ), 
     R 1  to R 8  may each the same as defined in connection with R 14 , wherein 
     *″ indicates a binding site to a carbon atom of a neighboring pyridine ring in Formula 2B, and 
     *′ indicates a binding site to M in Formula 1. 
     In one or more embodiments, the organometallic compound may be represented by Formula 1A: 
     
       
         
         
             
             
         
       
     
     In Formula 1A, 
     M, n1, n2, X 1 , X 21 , R 21  to R 23 , and R 11  to R 13  may each be the same as described above, 
     T 11  may be N or C(Z 11 ), T 12  may be N or C(Z 12 ), T 13  may be N or C(Z 13 ), and T 14  may be N or C(Z 14 ), wherein Z 11  to Z 14  may each be the same as defined in connection with Z 1 , 
     T 21  may be N, C(Z 21 ), carbon linked to a neighboring 6-membered ring, or carbon linked to M in Formula 1, T 22  may be N, C(Z 22 ), carbon linked to a neighboring 6-membered ring, or carbon linked to M in Formula 1, T 23  may be N, C(Z 23 ), carbon linked to a neighboring 6-membered ring, or carbon linked to M in Formula 1, T 24  may be N, C(Z 24 ), carbon linked to a neighboring 6-membered ring, or carbon linked to M in Formula 1, T 25  may be N or C(Z 25 ), T 26  may be N or C(Z 26 ), T 27  may be N or C(Z 27 ), and T 28  may be N or C(Z 28 ), wherein one of T 21  to T 24  may be carbon linked to M in Formula 1, one of the remaining T 21  to T 24  that are not linked to M in Formula 1 may be carbon linked to a neighboring 6-membered ring, and Z 21  to Z 24  may each be the same as defined in connection with Z 2 , 
     T 31  may be N or C(R 14a ), T 32  may be N or C(R 14b ), T 33  may be N or C(R 14c ), and T 24  may be N or C(R 14d ), wherein R 14a  to R 14d  may each be the same as defined in connection with R 14 , 
     two or more of Z 11  to Z 14  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     two or more of Z 21  to Z 28  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     R 12  and R 13  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     two or more of R 14a  to R 14d  may optionally be linked to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , and 
     R 10a  may be the same as defined in connection with R 14 . 
     Descriptions for Formula 1A may refer to descriptions for Formula 1 in this disclosure. 
     For example, T 13  in Formula 1A may be C(Z 13 ) and Z 13  may not be a hydrogen. 
     In one or more embodiments, the number of silicon (Si) atoms in the organometallic compound represented by Formula 1 may be 1 or 2. 
     In one or more embodiments, the organometallic compound may be one of Compounds 1 to 1620: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Compounds 1 to 1620, OMe indicates a methoxy group. 
     L 1  of the organometallic compound represented by Formula 1 may be a ligand represented by Formula 2A, and n1 which indicates the number of L 1 (s) may be 1 or 2. L 2  of the organometallic compound represented by Formula 1 may be a ligand represented by Formula 2B, and n2 which indicates the number of L 2 (S) may be 1 or 2. Here, L 1  and L 2  are different from each other. That is, the organometallic compound may be a heteroleptic complex essentially including, as ligands linked to metal M, at least one ligand represented by Formula 2A and at least one ligand represented by Formula 2B. 
     A group represented by *—X 1 (R 21 )(R 22 )(R 23 ) in Formula 1 may be linked to the fifth position of a pyridine ring in a ligand represented by Formula 2B (see Formula 2B). Accordingly, the organometallic compound including the ligand represented by Formula 2B may have excellent heat resistance and degradation resistance so that an electronic device, for example, an organic light-emitting device, including the organometallic compound may have high stability and long lifespan in production, storage, and/or operation. 
     Furthermore, when X 1  is Si, at least one of T 1  to T 8  which are not linked to M and ring CY1 in Formula 2A may be N. Accordingly, an electronic device, for example, an organic light-emitting device, including the organometallic compound represented by Formula 1 may have improved driving voltage and roll-off ratio. 
     In one or more embodiments, in Formulae 2A and 2B, R 21  to R 23 , Z 1 , Z 2 , and R 11  to R 14  do not each include a silicon (Si). Accordingly, an electronic device, for example, an organic light-emitting device, including the organometallic compound represented by Formula 1 may have improved out-coupling characteristics. 
     In addition, R 12  in Formula 2B is not hydrogen nor a methyl group. As such, the organometallic compound represented by Formula 1 may emit light that is shifted toward relatively shorter wavelengths, for example, blue light, green light, or greenish blue light, and an electronic device, for example, an organic light-emitting device, including the organometallic compound may have an excellent out-coupling effect, thereby having high luminescence efficiency. 
     A highest occupied molecular orbital (HOMO) energy level, a lowest unoccupied molecular orbital (LUMO) energy level, a singlet (S 1 ) energy level, and a triplet (T 1 ) energy level of some compounds of the organometallic compound represented by Formula 1 are evaluated by a density functional theory (DFT) of Gaussian program with molecular structure optimization based on B3LYP, and results are shown in Table 1. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Compound No. 
                 HOMO (eV) 
                 LUMO (eV) 
                 S 1  (eV) 
                 T 1  (eV) 
               
               
                   
               
             
            
               
                 123 
                 −4.773 
                 −1.203 
                 2.880 
                 2.546 
               
               
                 301 
                 −4.787 
                 −1.314 
                 2.738 
                 2.476 
               
               
                 226 
                 −4.780 
                 −1.208 
                 2.876 
                 2.529 
               
               
                 545 
                 −4.767 
                 −1.196 
                 2.879 
                 2.526 
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, it is confirmed that the organometallic compound represented by Formula 1 has such electrical characteristics that are suitable for use in an electronic device, for example, for use as a dopant for an organic light-emitting device. 
     Synthesis methods of the organometallic compound represented by Formula 1 may be recognizable by one of ordinary skill in the art by referring to Synthesis Examples provided below. 
     Therefore, the organometallic compound represented by Formula 1 may be suitable for use in an organic layer of an organic light-emitting device, for example, for use as a dopant in an emission layer of the organic layer. Another aspect of the present disclosure provides an organic light-emitting device including: a first electrode, a second electrode, and an organic layer disposed between the first electrode and the second electrode and including an emission layer, wherein the organic layer may include at least one organometallic compound represented by Formula 1. 
     The organic light-emitting device may have, due to the inclusion of an organic layer including the organometallic compound represented by Formula 1, a low driving voltage, high external quantum efficiency, a long lifespan, a low roll-off ratio, and excellent color purity. 
     The organometallic compound represented by Formula 1 may be used between 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 regard, the organometallic compound may act as a dopant, and the emission layer may further include a host (that is, an amount of the organometallic compound represented by Formula 1 is smaller than an amount of the host). The emission layer may emit, for example, green light or blue light. 
     The expression “(an organic layer) includes at least one of the organometallic compound” as used herein may include a case in which “(an organic layer) includes identical organometallic compounds represented by Formula 1” and a case in which “(an organic layer) includes two or more different organometallic compounds represented by Formula 1”. 
     For example, the organic layer may include, as the organometallic compound, only Compound 1. In this regard, Compound 1 may exist only in the emission layer of the organic light-emitting device. In one or more embodiments, the organic layer may include, as the organometallic compound, Compound 1 and Compound 2. In this regard, Compound 1 and Compound 2 may exist in an identical layer (for example, Compound 1 and Compound 2 all may exist in an 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; or 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 is an anode, and the second electrode is a cathode, and the organic layer further includes 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, and the hole transport region includes a hole injection layer, a hole transport layer, an electron blocking layer, or any combination thereof, and the electron transport region includes a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     The term “organic layer” as used herein refers to a single layer and/or a plurality of layers disposed between the first electrode and the second electrode of an organic light-emitting device. The “organic layer” may include, in addition to an organic compound, an organometallic complex including metal. 
     FIGURE is a schematic cross-sectional view of an organic light-emitting device  10  according to an embodiment. Hereinafter, the structure of an organic light-emitting device according to an embodiment and a method of manufacturing an organic light-emitting device according to an embodiment will be described in connection with the FIGURE. The organic light-emitting device  10  includes a first electrode  11 , an organic layer  15 , and a second electrode  19 , which are sequentially stacked. 
     A substrate may be additionally disposed under the first electrode  11  or above the second electrode  19 . For use as the substrate, any substrate that is used in general organic light-emitting devices may be used, and the substrate may be a glass substrate or a transparent plastic substrate, each having excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and water resistance. 
     The first electrode  11  may be formed by depositing or sputtering a material for forming the first electrode  11  on the substrate. The first electrode  11  may be an anode. The material for forming the first electrode  11  may include a material(s) with a high work function to facilitate hole injection. The first electrode  11  may be a reflective electrode, a semi-reflective electrode, or a transmissive electrode. The material for forming the first electrode may be, for example, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), and zinc oxide (ZnO). In one or more embodiments, the material for forming the first electrode  11  may be metal, such as magnesium (Mg), aluminum (Al), 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 two or more layers. For example, the first electrode  11  may have a three-layered structure of ITO/Ag/ITO. 
     The organic layer  15  is disposed 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 disposed 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 any combination thereof. 
     The hole transport region may include only either a hole injection layer or a hole transport layer. In one or more embodiments, the hole transport region may have a hole injection layer/hole transport layer structure or a hole injection layer/hole transport layer/electron blocking layer structure, which are sequentially stacked in this stated order from the first electrode  11 . 
     When the hole transport region includes a hole injection layer (HIL), the hole injection layer may be formed on the first electrode  11  by using one or more suitable methods, for example, vacuum deposition, spin coating, casting, and/or Langmuir-Blodgett (LB) deposition. 
     When a hole injection layer is formed by vacuum deposition, the deposition conditions may vary according to a material that is used to form the hole injection layer, and the structure and thermal characteristics of the hole injection layer. For example, the deposition conditions may include a deposition temperature of about 100° C. to about 500° C., a vacuum pressure of about 10 −8  to about 10 −3  torr, and a deposition rate of about 0.01 Å/sec to about 100 Å/sec. However, the deposition conditions are not limited thereto. 
     When the hole injection layer is formed using spin coating, coating conditions may vary according to the material used to form the hole injection layer, and the structure and thermal properties of the hole injection layer. For example, a coating speed may be from about 2,000 rpm to about 5,000 rpm, and a temperature at which a heat treatment is performed to remove a solvent after coating may be from about 80° C. to about 200° C. However, the coating conditions are not limited thereto. 
     Conditions for forming a hole transport layer and an electron blocking layer may be understood by referring to conditions for forming the hole injection layer. 
     The hole transport region may include m-MTDATA, TDATA, 2-TNATA, NPB, R-NPB, TPD, spiro-TPD, spiro-NPB, methylated-NPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzenesulfonic acid (PANI/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonicacid (PANI/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), a compound represented by Formula 201 below, a compound represented by Formula 202 below, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Ar 101  to Ar 102  in Formula 201 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, or a perylenylene group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, 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 3 -C 10  cycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkyl group, a C 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or any combination thereof. 
     The designations xa and xb in Formula 201 may each independently be an integer from 0 to 5, or may be 0, 1 or 2. For example, xa may be 1 and xb may be 0. 
     R 101  to R 108 , R 111  to R 119 , and R 121  to R 124  in Formulae 201 and 202 may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, 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 (for example, a methyl group, an ethyl group, a propyl group, a butyl group, pentyl group, a hexyl group, and the like), or a C 1 -C 10  alkoxy group (for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, and the like); 
     a C 1 -C 10  alkyl group or a C 1 -C 10  alkoxy group, each substituted with deuterium, —F, —Cl, —Br, —I, 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 any combination thereof; 
     a phenyl group, a naphthyl group, an anthracenyl group, a fluorenyl group, or a pyrenyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, 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, or any combination thereof 
     R 109  in Formula 201 may be: 
     a phenyl group, a naphthyl group, an anthracenyl group, or a pyridinyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, 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 phenyl group, a naphthyl group, an anthracenyl group, a pyridinyl group, or any combination thereof. 
     In one or more embodiments, the compound represented by Formula 201 may be represented by Formula 201A below: 
     
       
         
         
             
             
         
       
     
     Detailed descriptions of R 101 , R 111 , R 112 , and R 109  in Formula 201A are the same as described above. 
     For example, the hole transport region may include at least one of compounds HT1 to HT20 illustrated below: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the hole transport region may be from about 100 Å to about 10,000 Å, for example, about 100 Å to about 1,000 Å. When the hole transport region includes a hole injection layer, a hole transport layer, an electron blocking layer or combination thereof, a thickness of the hole injection layer may be in a range of about 100 Å to about 10000 Å, for example, about 100 Å to about 1,000 Å, and a thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, for example 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 these ranges, satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The hole transport region may further include, in addition to these materials, a charge-generation material for the improvement of conductive properties. The charge-generation material may be homogeneously or non-homogeneously dispersed in the hole transport region. 
     The charge-generation material may be, for example, a p-dopant. The p-dopant may be a quinone derivative, a metal oxide, a cyano group-containing compound, or any combination thereof. Non-limiting examples of the p-dopant are a quinone derivative, such as tetracyanoquinonedimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ) and F6-TCNNQ; a metal oxide, such as a tungsten oxide or a molybdenum oxide; and a cyano group-containing compound, such as Compound HT-D1 below: 
     
       
         
         
             
             
         
       
     
     The hole transport region may include a buffer layer. 
     Also, the buffer layer may compensate for an optical resonance distance according to a wavelength of light emitted from the emission layer, and thus, efficiency of a formed organic light-emitting device may be improved. 
     Meanwhile, when the hole transport region includes an electron blocking layer, a material for the electron blocking layer may be materials for the hole transport region described above, materials for a host to be explained later, or any combination thereof. However, the material for the electron blocking layer is not limited thereto. For example, when the hole transport region includes an electron blocking layer, a material for the electron blocking layer may be mCP, which will be explained later. 
     Then, an emission layer may be formed on the hole transport region by vacuum deposition, spin coating, casting, LB deposition, or the like. When the emission layer is formed by vacuum deposition or spin coating, the deposition or coating conditions may be similar to those applied in forming the hole injection layer although the deposition or coating conditions may vary according to a compound that is used to form the emission 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 TPBi, TBADN, ADN (also referred to as “DNA”), CBP, CDBP, TCP, mCP, Compounds H50, Compound H51, Compound H52, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     When the organic light-emitting device is a full-color organic light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and/or a blue emission layer. In one or more embodiments, due to a stacked structure including a red emission layer, a green emission layer, and/or a blue emission layer, the emission layer may emit white light. 
     When the emission layer includes a host and a dopant, an amount of the dopant may be in a range of about 0.01 parts by weight to about 15 parts by weight based on 100 parts by weight of the host. 
     A thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. When the thickness of the emission layer is within this range, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Then, an electron transport region may be disposed on the emission layer. 
     The electron transport region may include a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     For example, the electron transport region may have a hole blocking layer/electron transport layer/electron injection layer structure or an electron transport layer/electron injection layer structure. The electron transport layer may have a single-layered structure or a multi-layered structure including two or more different materials. 
     Conditions for forming the hole blocking layer, the electron transport layer, and the electron injection layer which constitute the electron transport region may be understood by referring to 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, BCP, Bphen, BAlq, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     A thickness of the hole blocking layer may be from about 20 Å to about 1,000 Å, for example, about 30 Å to about 600 Å. When the thickness of the hole blocking layer is within these ranges, the hole blocking layer may have excellent hole blocking characteristics without a substantial increase in driving voltage. 
     The electron transport layer may include BCP, Bphen, Alq 3 , BAIq, TAZ, NTAZ, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     In one or more embodiments, the electron transport layer may include at least one of ET1 to ET25: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the electron transport layer may be from about 100 Å to about 1,000 Å, for example, about 150 Å to about 500 Å. When the thickness of the electron transport layer is within the range described above, the electron transport layer may have satisfactory electron transport characteristics without a substantial increase in driving voltage. 
     Also, the electron transport layer may further include, in addition to the materials described above, a metal-containing material. 
     The metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (LiQ), Compound ET-D2, or combination thereof: 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer that promotes flow of electrons from the second electrode  19  thereinto. 
     The electron injection layer may include LiF, NaCl, CsF, Li 2 O, BaO, or any combination thereof. 
     A thickness of the electron injection layer may be from about 1 Å to about 100 Å, for example, about 3 Å to about 90 Å. When a thickness of the electron injection layer is within these ranges, satisfactory electron injection characteristics may be obtained without substantial increase in driving voltage. 
     The second electrode  19  is disposed on the organic layer  15 . The second electrode  19  may be a cathode. A material for forming the second electrode  19  may be a metal, an alloy, an electrically conductive compound, and a combination thereof, which have a relatively low work function. For example, lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), or magnesium-silver (Mg—Ag) may be formed as the material for forming the second electrode  19 . To manufacture a top-emission type light-emitting device, a transmissive electrode formed using ITO or IZO may be used as the second electrode  19 . 
     Hereinbefore, the organic light-emitting device according to an embodiment has been described in connection with the FIGURE. 
     In one or more embodiments, the organic light-emitting device may be included in an electronic apparatus. Accordingly, provided is an electronic apparatus including the organic light-emitting device. The electronic apparatus may include, for example, a display, an illuminator, and a sensor. 
     Another aspect of the present disclosure provides a diagnostic composition including at least one of the organometallic compound represented by Formula 1. 
     The organometallic compound represented by Formula 1 provides high luminescent efficiency. Accordingly, a diagnostic composition including the organometallic compound may have high diagnostic efficiency. 
     The diagnostic composition may be used in various applications including a diagnosis kit, a diagnosis reagent, a biosensor, and 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, and 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. 
     Non-limiting examples of the C 1 -C 60  alkyl group, the C 1 -C 20  alkyl group, and/or the C 1 -C 10  alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group, each unsubstituted or substituted with a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, or any combination thereof. For example, Formula 9-33 may be a branched C 6  alkyl group, and may be a tert-butyl group that is substituted with two methyl groups. 
     The term “C 1 -C 60  alkoxy group” used herein refers to a monovalent group represented by —OA 101  (wherein A 101  is the C 1 -C 60  alkyl group). Non-limiting examples of the C 1 -C 60  alkoxy group, the C 1 -C 20  alkoxy group, or the C 1 -C 10  alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a pentoxy group. 
     The term “C 2 -C 60  alkenyl group” as used herein refers to a hydrocarbon group having at least one carbon-carbon double bond in the middle or at the terminus of the C 2 -C 60  alkenyl group, and 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 hydrocarbon group having at least one carbon-carbon triple bond in the middle or at the terminus of the C 2 -C 60  alkynyl group, and examples thereof include an ethynyl group, and a propynyl 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 saturated hydrocarbon monocyclic group having 3 to 10 carbon atoms, and 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. 
     Non-limiting examples of the C 3 -C 10  cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group(a norbornyl group), and a bicyclo[2.2.2]octyl group. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent saturated monocyclic group having at least one N, O, P, Si, B, Se, Ge, S, or any combination thereof as a ring-forming atom and 1 to 10 carbon atoms, and 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. 
     Non-limiting examples of the C 1 -C 10  heterocycloalkyl group include a silolanyl group, a silinanyl group, a tetrahydrofuranyl group, a tetrahydro-2H-pyranyl group, and a tetrahydrothiophenyl group. 
     The term “C 3 -C 10  cycloalkenyl group” as used herein refers to a monovalent monocyclic group that has 3 to 10 carbon atoms and at least one carbon-carbon double bond in the ring thereof and no aromaticity, and non-limiting 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 that has at least one N, O, P, Si, B, Ge, Se, S, or any combination thereof as a ring-forming atom, 2 to 10 carbon atoms, and at least one double bond in its ring. Examples of the C 2 -C 10  heterocycloalkenyl group include a 2,3-dihydrofuranyl group, and a 2,3-dihydrothiophenyl group. The term “C 2 -C 10  heterocycloalkenylene 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, and 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. Non-limiting examples of the C 6 -C 60  aryl group include a phenyl 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 the C 6 -C 60  arylene group each include two or more rings, the rings may be fused to each other. 
     The term “C 7 -C 60  alkylaryl group” used herein refers to a C 6 -C 59  arylene group substituted with at least one C 1 -C 54  alkyl group. 
     The term “C 1 -C 60  heteroaryl group” as used herein refers to a monovalent group having a heterocyclic aromatic system that has at least one N, O, P, Si, B, Se, Ge, S, or any combination thereof as a ring-forming atom, in addition to 1 to 60 carbon atoms. The term “C 1 -C 60  heteroarylene group” as used herein refers to a divalent group having a heterocyclic aromatic system that has at least one heteroatom N, O, P, Si, B, Se, Ge, S, or any combination thereof as a ring-forming atom, in addition to 1 to 60 carbon atoms. Non-limiting 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 two or more rings, the rings may be fused to each other. 
     The term “C 2 -C 60  alkylheteroaryl group” used herein refers to a C 1 -C 59  heteroarylene group substituted with at least one C 1 -C 59  alkyl group. 
     The term “C 6 -C 60  aryloxy group” used herein indicates —OA 102  (wherein A 102  is the C 6 -C 60  aryl group), a C 6 -C 60  arylthio group used herein indicates —SA 103  (wherein A 103  is the C 6 -C 60  aryl group), and a C 1 -C 60  alkylthio group used herein indicates —SA 104  (wherein A 104  is the C 1 -C 60  alkyl group). 
     The term “monovalent non-aromatic condensed polycyclic group” as used herein refers to a monovalent group (for example, having 8 to 60 carbon atoms) having two or more rings condensed to each other, only carbon atoms as ring-forming atoms, and no aromaticity in its entire molecular structure. 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 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 (for example, having 2 to 60 carbon atoms) having two or more rings condensed to each other, a heteroatom N, O, P, Si, and S, other than carbon atoms, as a ring-forming atom, and no aromaticity in its entire molecular structure. Non-limiting 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 having, as a ring-forming atom, 5 to 30 carbon atoms only. The C 5 -C 30  carbocyclic group may be a monocyclic group or a polycyclic group. The term “C 5 -C 30  carbocyclic group (which is unsubstituted or substituted with at least one R 10a )” may include, for example, an adamantane group, a norbornene group, a bicyclo[1.1.1]pentane group, a bicyclo[2.1.1]hexane group, a bicyclo[2.2.1]heptane group (a norbornane group), a bicyclo[2.2.2]octane group, a cyclopentane group, a cyclohexane group, a cyclohexene group, a benzene group, a naphthalene group, an anthracene group, a phenanthrene group, a triphenylene group, a pyrene group, a chrysene group, a 1,2,3,4-tetrahydronaphthalene group, cyclopentadiene group, and a fluorene group, each being unsubstituted or substituted with at least one R 10a . 
     The term “C 1 -C 30  heterocyclic group” as used herein refers to a saturated or unsaturated cyclic group having, as a ring forming atom, at least one N, O, P, Si, Se, Ge, B, S, or any combination thereof other than 1 to 30 carbon atoms. The C 1 -C 30  heterocyclic group may be a monocyclic group or a polycyclic group. The “C 1 -C 30  heterocyclic group (which is unsubstituted or substituted with at least one R 10a )” may include, for example, a thiophene group, a furan group, a pyrrole group, a silole group, a borole group, a phosphole group, a selenophene group, a germole group, a benzothiophene group, a benzofuran group, an indole group, an indene group, a benzosilole group, a benzoborole group, a benzophosphole group, a benzoselenophene group, a benzogermole group, a dibenzothiophene group, a dibenzofuran group, a carbazole group, a dibenzosilole group, a dibenzoborole group, a dibenzophosphole group, a dibenzoselenophene group, a dibenzogermole group, a dibenzothiophene 5-oxide group, 9H-fluorene-9-one group, a dibenzothiophene 5,5-dioxide group, an azabenzothiophene group, an azabenzofuran group, an azaindole group, an azaindene group, an azabenzosilole group, an azabenzoborole group, an azabenzophosphole group, an azabenzoselenophene group, an azabenzogermole group, an azadibenzothiophene group, an azadibenzofuran group, an azacarbazole group, an azafluorene group, an azadibenzosilole group, an azadibenzoborole group, an azadibenzophosphole group, an azadibenzoselenophene group, an azadibenzogermole group, an azadibenzothiophene 5-oxide group, an aza-9H-fluorene-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 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, and a 5,6,7,8-tetrahydroquinoline group, each being unsubstituted or substituted with at least one R 10a . 
     The term “(C 1 -C 20  alkyl)‘X’ group” as used herein refers to a ‘X’ group substituted with at least one C 1 -C 20  alkyl group. For example, the term “(C 1 -C 20  alkyl)C 3 -C 10  cycloalkyl group” as used herein refers to a C 3 -C 10  cycloalkylene group substituted with at least one C 1 -C 20  alkyl group and the term “(C 1 -C 20  alkyl)phenyl group” as used herein refers to a phenylene group substituted with at least one C 1 -C 20  alkyl group. An example of a (C 1  alkyl)phenyl group is a toluyl group. 
     The terms “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-fluorene-9-one group, and an azadibenzothiophene 5,5-dioxide group” respectively refer to a heterocyclic group having the same backbone as “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 dibenzoselenophene group, a dibenzofuran group, a dibenzothiophene 5-oxide group, 9H-fluorene-9-one group, and a dibenzothiophene 5,5-dioxide group” in which at least one of the carbon atoms constituting the cyclic groups is substituted with a nitrogen. 
     A 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 2 -C 10  heterocycloalkenyl group, the substituted C 6 -C 60  aryl group, the substituted C 7 -C 60  alkylaryl 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  alkylheteroaryl group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group may each independently be: 
     deuterium, —F, —Cl, —Br, —I, —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 deuterium, —F, —Cl, —Br, —I, —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 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl 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  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Ge(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), —P(═O)(Q 18 )(Q 19 ), —P(Q 18 )(Q 19 ), or any 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 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each substituted with deuterium, —F, —Cl, —Br, —I, —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 2 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl 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  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Ge(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(═O)(Q 28 )(Q 29 ), —P(Q 28 )(Q 29 ), or any combination thereof; 
     —N(Q 31 )(Q 32 ), —Ge(Q 33 )(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), —P(═O)(Q 38 )(Q 39 ) or —P(Q 38 )(Q 39 ); or 
     any combination thereof. 
     In the present specification, 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; 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 unsubstituted or substituted with deuterium, a C 1 -C 60  alkyl group, a C 6 -C 60  aryl group, or any combination thereof; a C 2 -C 60 alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; a C 3 -C 10  cycloalkyl group; a C 1 -C 10  heterocycloalkyl group; a C 3 -C 10  cycloalkenyl group; a C 2 -C 10  heterocycloalkenyl group; a C 6 -C 60  aryl group unsubstituted or substituted with deuterium, a C 1 -C 60  alkyl group, a C 6 -C 60  aryl group, or any combination thereof; a C 6 -C 60  aryloxy group; a C 6 -C 60  arylthio group; a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group; or a monovalent non-aromatic condensed heteropolycyclic group. 
     For example, in the present specification, 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 
     —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 ; or 
     an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, or any combination thereof. 
     Hereinafter, a compound and an organic light-emitting device according to embodiments are described in detail with reference to Synthesis Example and Examples. However, the organic light-emitting device is not limited thereto. The wording “B was used instead of A” used in describing Synthesis Examples means that an amount of A used was identical to an amount of B used, in terms of a molar equivalent. 
     EXAMPLES 
     Synthesis Example 1 (Compound 125) 
     Synthesis of Compound 125A 
     
       
         
         
             
             
         
       
     
     4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine (8.0 g, 28.4 mmol) and iridium chloride (4.4 g, 12.6 mmol) were mixed with 120 mL of ethoxyethanol and 40 mL of distilled water. The mixed solution was stirred under reflux for 24 hours, and the temperature was lowered to room temperature. A solid produced therefrom was separated by filtration, and then, washed thoroughly with water/methanol/hexane in the stated order. The resulting solid was then dried in a vacuum oven, thereby obtaining 7.5 g of Compound 125A (yield of 75%). Synthesis of Compound 125B 
     
       
         
         
             
             
         
       
     
     Compound 125A (1.6 g, 1.0 mmol) was mixed with 45 ml of methylene chloride (MC), and a mixture of AgOTf (Silver trifluoromethanesulfonate) (0.5 g, 2.1 mmol) and 15 ml of methanol was added thereto. Afterwards, the mixed solution was stirred at room temperature for 18 hours while blocking the light with aluminum foil. The resulting solution was then filtered through celite to remove a solid produced therefrom, and the solvent was removed from the filtrate under reduced pressure, and a solid (Compound 125B) produced therefrom was used in the next reaction without additional purification. 
     Synthesis of Compound 125 
     
       
         
         
             
             
         
       
     
     Compound 125B (2.0 g, 2.1 mmol) and 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine (0.8 g, 2.4 mmol) were mixed with 40 ml of a mixture of MC and ethanol. The mixed solution was stirred under reflux for 18 hours, and the temperature was lowered down. The resulting solution was filtered, and a solid obtained therefrom was washed thoroughly with ethanol and hexane. The resulting product was subjected to column chromatography under the MC:hexane conditions, thereby obtaining 0.8 g of Compound 125 (yield of 36%). Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 57 H 67 IrN 4 OSi 2 : m/Z 1072.4483 Found: 1072.4490 Synthesis Example 2 (Compound 128) 
     
       
         
         
             
             
         
       
     
     0.9 g of Compound 128 (yield of 40%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that 8-(4-(cyclopentylmethyl)pyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 59 H 69 IrN 4 OSi 2 : m/Z 1098.4639, Found: 1098.4631 
     Synthesis Example 3 (Compound 163) 
     Synthesis of Compound 163A 
     
       
         
         
             
             
         
       
     
     6.5 g of Compound 163A (yield of 65%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 4-(cyclopentylmethyl)-2-phenyl-5-(trimethylsilyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 163B 
     
       
         
         
             
             
         
       
     
     Compound 163B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 163A was used instead of Compound 125 Å. Compound 163B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 163 
     
       
         
         
             
             
         
       
     
     0.65 g of Compound 163 (yield of 29%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 163B was used instead of Compound 125B and 8-(4-isopropylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 60 H 69 IrN 4 OSi 2 : m/Z 1110.4639, Found: 1110.4644. 
     Synthesis Example 4 (Compound 365) 
     
       
         
         
             
             
         
       
     
     0.85 g of Compound 365 (yield of 37%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that 6-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 57 H 67 IrN 4 OSi 2 : m/Z 1072.4483 Found: 1072.4488. 
     Synthesis Example 5 (Compound 505) 
     Synthesis of Compound 505A 
     
       
         
         
             
             
         
       
     
     7.1 g of Compound 505A (yield of 71%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 4-isobutyl-D 2 -2-phenyl-5-(trimethylsilyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 505B 
     
       
         
         
             
             
         
       
     
     Compound 505B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 505A was used instead of Compound 125A. Compound 505B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 505 
     
       
         
         
             
             
         
       
     
     0.5 g of Compound 505 (yield of 22%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 505B was used instead of Compound 125B and 8-(4-isobutylpyridin-2-yl-D 2 )-2-methyl(D 3 )benzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 57 H 58 D 9 IrN 4 OSi 2 : m/Z 1081.5048, Found: 1081.5052. 
     Synthesis Example 6 (Compound 526) 
     Synthesis of Compound 526A 
     
       
         
         
             
             
         
       
     
     6.6 g of Compound 526A (yield of 66%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 4-neopentyl(D 2 )-2-phenyl-5-(trimethylsilyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 526B 
     
       
         
         
             
             
         
       
     
     Compound 526B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 526A was used instead of Compound 125A. Compound 526B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 526 
     
       
         
         
             
             
         
       
     
     1.0 g of Compound 526 (yield of 44%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 526B was used instead of Compound 125B and 2-isopropyl(D)-8-(4-neopentyl(D 2 )pyridin-2-yl)benzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 62 H 70 D 7 IrN 4 OSi 2 : m/Z 1149.5705, Found: 1149.5700. 
     Synthesis Example 7 (Compound 676) 
     
       
         
         
             
             
         
       
     
     0.8 g of Compound 676 (yield of 41%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that 2-phenyl-8-(4-(propan-2-yl-2-d)pyridin-2-yl)benzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 61 H 66 IrN 4 OSi 2 : m/Z 1121.4545, Found: 1121.4549. 
     Synthesis Example 8 (Compound 806) 
     Synthesis of Compound 806A 
     
       
         
         
             
             
         
       
     
     3.7 g of Compound 806A (yield of 74%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 4-isobutyl-2-phenyl-5-(trimethylgermyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 806B 
     
       
         
         
             
             
         
       
     
     Compound 806B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 806A was used instead of Compound 125A. Compound 806B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 806 
     
       
         
         
             
             
         
       
     
     0.53 g of Compound 806 (yield of 35%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 806B was used instead of Compound 125B and 2-methyl(D 3 )-8-(4-neopentylpyridin-2-yl)benzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 58 H 66 D 3 Ge 2 IrN 4 O: m/z 1181.3712, Found: 1181.3706. 
     Synthesis Example 9 (Compound 865) 
     
       
         
         
             
             
         
       
     
     0.69 g of Compound 865 (yield of 31%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 806B was used instead of Compound 125B and 2-(dibenzo[b,d]furan-4-yl)-4-isobutylpyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 57 H 66 Ge 2 IrN 3 O: m/z 1149.3259, Found: 1149.3251. 
     Synthesis Example 10 (Compound 1365) 
     Synthesis of Compound 1365A 
     
       
         
         
             
             
         
       
     
     4.6 g of Compound 1365A (yield of 62%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 4-isobutyl(D 2 )-2-(p-tolyl(D 3 ))-5-(trimethylgermyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 1365B 
     
       
         
         
             
             
         
       
     
     Compound 1365B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 1365A was used instead of Compound 125A. Compound 1365B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 1365 
     
       
         
         
             
             
         
       
     
     0.43 g of Compound 1365 (yield of 28%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 1365B was used instead of Compound 125B and 2-(7-methyl(D 3 )dibenzo[b,d]thiophen-4-yl)-4-neopentyl(D 2 )pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine. Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 61 H 59 D 15 Ge 2 IrN 3 O: m/z 1236.4598, Found: 1236.4591. 
     Synthesis Example 11 (Compound 1497) 
     Synthesis of Compound 1497A 
     
       
         
         
             
             
         
       
     
     4.2 g of Compound 1497A (yield of 58%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 2-phenyl-4-(propan-2-yl-2-d)-5-(trimethylgermyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 1497B 
     
       
         
         
             
             
         
       
     
     Compound 1497B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 1497A was used instead of Compound 125A. Compound 1497B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 1497 
     
       
         
         
             
             
         
       
     
     0.53 g of Compound 1497 (yield of 34%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 1497B was used instead of Compound 125B and 2-(2,6-dimethylphenyl)-8-(4-(2,2-dimethylpropyl-1,1-d2)-5-(methyl-d3)pyridin-2-yl)benzofuro[2,3-b]pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 64 H 66 D 7 Ge 2 IrN 4 O: m/z 1261.4277, Found: 1261.4271. 
     Synthesis Example 12 (Compound 1505) 
     Synthesis of Compound 1505A 
     
       
         
         
             
             
         
       
     
     4.3 g of Compound 1505A (yield of 49%) was obtained in the same manner as in the synthesis of Compound 125A according to Synthesis Example 1, except that 4-(2,2-dimethylpropyl-1,1-d2)-2-phenyl-5-(trimethylgermyl)pyridine was used instead of 4-isobutyl-2-phenyl-5-(trimethylsilyl)pyridine. 
     Synthesis of Compound 1505B 
     
       
         
         
             
             
         
       
     
     Compound 1505B was obtained in the same manner as in the synthesis of Compound 125B according to Synthesis Example 1, except that Compound 1505A was used instead of Compound 125A. Compound 1505B thus obtained was used in the next reaction without additional purification. 
     Synthesis of Compound 1505 
     
       
         
         
             
             
         
       
     
     0.32 g of Compound 1505 (yield of 27%) was obtained in the same manner as in the synthesis of Compound 125 according to Synthesis Example 1, except that Compound 1505B was used instead of Compound 125B and 4-(2-methylpropyl-1,1-d2)-2-(8-phenyldibenzo[b,d]furan-4-yl)pyridine was used instead of 8-(4-isobutylpyridin-2-yl)-2-methylbenzofuro[2,3-b]pyridine Substances of the compound were identified by the Mass Spectrum and HPLC analysis. 
     HRMS(MALDI) calcd for C 65 H 68 D 6 Ge 2 IrN 3 O: m/z 1259.4261, Found: 1259.4255. 
     Example 1 
     As an anode, a glass substrate on which ITO/Ag/ITO was formed to a thickness of 70 Å/1,000 Å/70 Å was cut to a size of 50 mm×50 mm×0.5 mm, sonicated with isopropyl alcohol and pure water each for 5 minutes, and then, cleaned by exposure to ultraviolet rays and ozone for 30 minutes. Then, the anode was provided to a vacuum deposition apparatus. 
     2-TNATA was vacuum-deposited on the anode to form a hole injection layer having a thickness of 600 Å, and 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (hereinafter, referred to as NPB) was vacuum-deposited on the hole injection layer to form a hole transport layer having a thickness of 1,350 Å. 
     Next, CBP (as a host) and Compound 125 (as a dopant) were co-deposited at a weight ratio of 98:2 on the hole transport layer to form an emission layer having a thickness of 400 Å. 
     Then, BCP was vacuum-deposited on the emission layer to form a hole blocking layer having a thickness of 50 Å, and Alq 3  was vacuum-deposited on the hole blocking layer to form an electron transport layer having a thickness of 350 Å. LiF was vacuum-deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and Mg and Ag were co-deposited at a weight ratio of 90:10 on the electron injection layer to form a cathode having a thickness of 120 Å, thereby completing the manufacture of an organic light-emitting device. 
     
       
         
         
             
             
         
       
     
     Examples 2 to 12 and Comparative Examples A and B 
     Organic light-emitting devices were manufactured in the same manner as in Example 1, except that compounds listed in Table 2 below were each used as a dopant instead of Compound 125 in forming an emission layer. 
     Evaluation Example 1: Evaluation of Characteristics of Organic Light-Emitting Device 
     The driving voltage, maximum external quantum efficiency (Max EQE) value (%), and lifespan (LT 97 , hr) of the organic light-emitting devices manufactured according to Examples 1 to 12 and Comparative Examples A and B were evaluated, and results thereof are shown in Table 2. Here, as a device used for the evaluation, a current-voltage meter (Keithley 2400) and a luminance meter (Minolta C 5 -1000A) were used. The lifespan (LT 97 ) (at 3,500 nit) obtained by evaluating time (hr) that lapsed when luminance was 97% of initial luminance (100%), and was indicated in a relative value (%). 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                 LT 97   
               
               
                   
                 Compound No. of 
                 Driving 
                   
                 (relative value, %) 
               
               
                   
                 dopant in emission layer 
                 voltage(V) 
                 Max EQE(%) 
                 (at 3,500 nit) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Example 1 
                 125 
                 4.43 
                 23.3 
                 100 
               
               
                 Example 2 
                 128 
                 4.41 
                 23.4 
                 87 
               
               
                 Example 3 
                 163 
                 4.42 
                 24.1 
                 93 
               
               
                 Example 4 
                 365 
                 4.16 
                 22.3 
                 110 
               
               
                 Example 5 
                 505 
                 4.43 
                 23.6 
                 130 
               
               
                 Example 6 
                 526 
                 4.47 
                 25.4 
                 150 
               
               
                 Example 7 
                 676 
                 4.33 
                 25.8 
                 180 
               
               
                 Example 8 
                 806 
                 4.45 
                 23.2 
                 120 
               
               
                 Example 9 
                 865 
                 4.10 
                 23.0 
                 100 
               
               
                 Example 10 
                 1365 
                 4.38 
                 22.5 
                 110 
               
               
                 Example 11 
                 1497 
                 4.35 
                 25.1 
                 165 
               
               
                 Example 12 
                 1505 
                 4.48 
                 22.8 
                 170 
               
               
                 Comparative 
                 A 
                 4.35 
                 19.8 
                 27 
               
               
                 Example A 
                   
                   
                   
                   
               
               
                 Comparative 
                 B 
                 4.23 
                 20.5 
                 43 
               
               
                 Example B 
                   
                   
                   
                   
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                 
               
            
           
         
       
     
     Referring to Table 2, it was confirmed that the organic light-emitting device manufactured according to Examples 1 to 12 had a comparable value of driving voltage and improved external quantum efficiency and longer lifespan characteristics, as compared with the organic light-emitting device manufactured according to Comparative Examples A and B. 
     According to the one or more embodiments, the organometallic compound has excellent electronic characteristics and heat resistance, and thus, an electronic device, for example, an organic light-emitting device, including the organometallic compound may have good driving voltage, good external quantum efficiency, and good lifespan characteristics. In addition, since the organometallic compound has excellent phosphorescence characteristics, a diagnostic composition including the organometallic compound may be provided with a high diagnosis efficiency. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments have been described with reference to the figures, 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.