Patent Publication Number: US-2023157152-A1

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

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority to and the benefit of Korean Patent Application No. 10-2021-0157102, filed on Nov. 15, 2021, in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The present subject matter relates to an organometallic compound, a light-emitting device including the same, and an electronic apparatus including the light-emitting device. 
     2. Description of the Related Art 
     From among light-emitting devices, organic light-emitting devices (OLEDs) are self-emissive devices, which have improved characteristics in terms of viewing angles, response time, luminance, driving voltage, and response speed. OLEDS can also produce full-color images. 
     In a typical example, an organic light-emitting device includes an anode, a cathode, and an organic layer arranged between the anode and the cathode, wherein the organic layer includes an emission layer. A hole transport region may be arranged between the anode and the emission layer, and an electron transport region may be arranged between the emission layer and the cathode. Holes provided from the anode move toward the emission layer through the hole transport region, and electrons provided from the cathode move toward the emission layer through the electron transport region. The holes and the electrons recombine in the emission layer to produce excitons. The excitons may transition from an excited state to a ground state, thereby generating light (for example, a visible light). 
     SUMMARY 
     Provided are an organometallic compound, a light-emitting device including the same, and an electronic apparatus including the light-emitting device. 
     Additional aspects will be set forth in part in the detailed description that follows and, in part, will be apparent from the detailed description, or may be learned by practice of the presented exemplary embodiments herein. 
     According to an aspect, provided is an organometallic compound represented by Formula 1. 
     
       
         
         
             
             
         
       
     
     In Formula 1, 
     Y 1  to Y 4  are each independently C or N, 
     one of Y 1  to Y 4  is N bonded to iridium (Ir) in Formula 1, and another of Y 1  to Y 4  is C bonded to ring CY 2  in Formula 1, 
     Y 9  is O, S, N(R 19 ), C(R 19a )(R 19b ), or Si(R 19a )(R 19b ), 
     X 2  is C, 
     ring CY 1  and ring CY 2  are each independently a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group, 
     R 1 , R 19 , R 19a , R 19b , R 2 , R 30a , R 30b , and R 37  are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 0  alkyl aryl group, a substituted or unsubstituted C 7 -C 0  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(═O)(Q 8 )(Q 9 ), or —P(Q 8 )(Q 9 ), 
     a1 and a2 are each independently an integer from 0 to 20, with the proviso that i) a1 is not 0, and at least one of R 1  is —Ge(Q 3 )(Q 4 )(Q 5 ), ii) a2 is not 0, and at least one of R 2  is —Ge(Q 3 )(Q 4 )(Q 5 ), or iii) a1 is not 0, and at least one of R 1  is —Ge(Q 3 )(Q 4 )(Q 5 ), and a2 is not 0, and at least one of R 2  is —Ge(Q 3 )(Q 4 )(Q 5 ), two or more of a plurality of R 1  are optionally linked to each other 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 2  are optionally linked to each other 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 1  and R 2  are optionally linked to each other 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 30a , R 30b , and R 37  are optionally linked to each other 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  is the same as described in connection with R 1 , 
     at least one 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 1 -C 10 heterocycloalkenyl group, the substituted C 6 -C 60  aryl group, the substituted C 7 -C 0  alkyl aryl group, the substituted C 7 -C 0  aryl alkyl group, the substituted C 6 -C 60  aryloxy group, the substituted C 6 -C 60  arylthio group, the substituted C 1 -C 60  heteroaryl group, the substituted C 2 -C 60  alkyl heteroaryl group, the substituted C 2 -C 60  heteroaryl alkyl group, the substituted C 1 -C 60  heteroaryloxy group, the substituted C 1 -C 60  heteroarylthio group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is: 
     deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Si(Q 13 )(Q 14 )(Q 15 ), —Ge(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), —P(═O)(Q 18 )(Q 19 ), —P(Q 18 )(Q 19 ), or a combination thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 0  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each unsubstituted or substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 7 -C 60  aryl alkyl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 2 -C 60  heteroaryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Si(Q 23 )(Q 24 )(Q 25 ), —Ge(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(═O)(Q 28 )(Q 29 ), —P(Q 28 )(Q 29 ), or a combination thereof, 
     —N(Q 31 )(Q 32 ), —Si(Q 33 )(Q 34 )(Q 35 ), —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 
     a combination thereof, and 
     Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 0  alkyl aryl group, a substituted or unsubstituted C 7 -C 0  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     According to another aspect, provided is a light-emitting device including a first electrode, a second electrode, and an organic layer arranged between the first electrode and the second electrode, wherein the organic layer includes an emission layer, and wherein the organic layer further includes at least one organometallic compound represented by Formula 1. 
     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. 
     According to another aspect, provided is an electronic apparatus including the light-emitting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other aspects, features, and advantages of certain exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the FIGURE, which is a schematic cross-sectional view of a light-emitting device according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in further detail to exemplary embodiments, examples of which are illustrated in the accompanying drawing, wherein like reference numerals refer to like elements throughout the specification. In this regard, the present exemplary embodiments may have different forms and should not be construed as being limited to the detailed descriptions set forth herein. Accordingly, the exemplary embodiments are merely described in further detail below, and by referring to the drawing, to explain certain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the same associated listed items. As used herein, the expression “at least one of a, b or c” indicates only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. 
     The terminology used herein is for the purpose of describing one or more exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “or” means “and/or.” It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present embodiments. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly in contact with the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this general inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value. 
     Hereinafter, a work function or a highest occupied molecular orbital (HOMO) energy level is expressed as an absolute value from a vacuum level. In addition, when the work function or the HOMO energy level is referred to be “deep,” “high” or “large,” the work function or the HOMO energy level has a large absolute value based on “0 electron Volts (eV)” of the vacuum level, while when the work function or the HOMO energy level is referred to be “shallow,” “low,” or “small,” the work function or HOMO energy level has a small absolute value based on “0 eV” of the vacuum level. 
     Provided is an organometallic compound that is represented by Formula 1: 
     
       
         
         
             
             
         
       
     
     Y 1  to Y 4  in Formula 1 are each independently C or N. One of Y 1  to Y 4  is N bonded to iridium (Ir) in Formula 1, and another of Y 1  to Y 4  is C bonded to ring CY 2  in Formula 1. 
     In one or more embodiments, 
     1) Y 2  may be N bonded to iridium in Formula 1, and Y 1  may be C bonded to ring CY 2  in Formula 1, 
     2) Y 1  may be N bonded to iridium in Formula 1, and Y 2  may be C bonded to ring CY 2  in Formula 1, 
     3) Y 3  may be N bonded to iridium in Formula 1, and Y 2  may be C bonded to ring CY 2  in Formula 1, 
     4) Y 2  may be N bonded to iridium in Formula 1, and Y 3  may be C bonded to ring CY 2  in Formula 1, 
     5) Y 4  may be N bonded to iridium in Formula 1, and Y 3  may be C bonded to ring CY 2  in Formula 1, or 
     6) Y 3  may be N bonded to iridium in Formula 1, and Y 4  may be C bonded to ring CY 2  in Formula 1. 
     In Formula 1, Y 9  is O, S, N(R 19 ), C(R 19a )(R 19b ), or Si(R 19a )(R 19b ). R 19 , R 19a , and R 19b  are each as described herein. 
     In one or more embodiments, Y 9  may be O, S, or N(R 19 ). 
     In one or more embodiments, Y 9  may be O or S. 
     In Formula 1, X 2  is C. 
     In Formula 1, ring CY 1  and ring CY 2  are each independently a C 5 -C 30  carbocyclic group or a C 1 -C 30  heterocyclic group. 
     In one or more embodiments, ring CY 2  in Formula 1 may be a polycyclic group in which two or more cyclic groups are condensed with each other, and each of the two or more cyclic groups may be a C 5 -C 1  carbocyclic group or a C 1 -C 15  heterocyclic group. 
     In one or more embodiments, ring CY 1  and ring CY 2  in Formula 1 may each independently be i) a first ring, ii) a second ring, iii) a condensed cyclic ring group in which two or more first rings are condensed with each other, iv) a condensed cyclic ring group in which two or more second rings are condensed with each other, or v) a condensed cyclic ring group in which one or more first rings and one or more second rings are condensed with each other, 
     the first ring may be a cyclopentane group, a cyclopentene group, a furan group, a thiophene group, a pyrrole group, a silole group, a germole group, a borole group, a selenophene group, a phosphole group, an oxazole group, an oxadiazole group, an oxatriazole group, a thiazole group, a thiadiazole group, a thiatriazole group, a pyrazole group, an imidazole group, a triazole group, a tetrazole group, an azasilole group, an azagermole group, an azaborole group, an azaselenophene group, or an azaphosphole group, and 
     the second ring may be an adamantane group, a norbornane group, a norbornene group, a bicyclo[1.1.1]pentane group, a bicyclo[2.1.1]hexane group, a bicyclo[2.2.2]octane group, a cyclohexane group, a cyclohexene group, a benzene group, pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, or a triazine group. 
     In one or more embodiments, ring CY 1  in Formula 1 may be i) a first ring, ii) a second ring, iii) a condensed cyclic ring group in which two or more first rings are condensed with each other, iv) a condensed cyclic ring group in which two or more second rings are condensed with each other, or v) a condensed cyclic ring group in which one or more first rings and one or more second rings are condensed with each other, and ring CY 2  may be a) a condensed cyclic ring group in which two or more first rings are condensed with each other, b) a condensed cyclic ring group in which two or more second rings are condensed with each other, or c) a condensed cyclic ring group in which one or more first rings and one or more second rings are condensed with each other. The first ring and the second ring may each be as described herein. 
     In one or more embodiments, ring CY 1  and ring CY 2  in Formula 1 may each independently be 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, a thiophene group, a furan group, a pyrrole group, a cyclopentadiene 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 fluorene group, a dibenzosilole group, a dibenzoborole group, a dibenzophosphole group, a dibenzoselenophene group, a dibenzogermole group, a dibenzothiophene 5-oxide group, a 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 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 adamantane group, a norbornane group, or a norbornene group. 
     In one or more embodiments, ring CY 1  and ring CY 2  in Formula 1 may each independently be a benzene group, a naphthalene group, a phenanthrene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a benzoquinoline group, a benzoisoquinoline group, a benzoquinoxaline group, a benzofuran group, or a benzothiophene group. 
     In one or more embodiments, in Formula 1, ring CY 1  may be a benzene group, a naphthalene group, a phenanthrene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a benzoquinoline group, a benzoisoquinoline group, a benzoquinoxaline group, a benzofuran group, or a benzothiophene group, and ring CY 2  may be a naphthalene group, a phenanthrene group, a quinoline group, an isoquinoline group, a quinoxaline group, a benzoquinoline group, a benzoisoquinoline group, a benzoquinoxaline group, a benzofuran group, or a benzothiophene group. 
     R 1 , R 19 , R 19a , R 19b , R 2 , R 30a , R 30b , and R 37  in Formula 1 are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 0  alkyl aryl group, a substituted or unsubstituted C 7 -C 0  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(═O)(Q 8 )(Q 9 ), or —P(Q 8 )(Q 9 ). Q 1  to Q 9  are each as described herein. 
     In one or more embodiments, R 30a  in Formula 1 may be a group represented by *—C(R 31 )(R 32 )(R 33 ). R 31  to R 33  may each be as defined for R 30a . 
     R 30b  in Formula 1 may be a group represented by *—C(R 34 )(R 35 )(R 36 ). R 34  to R 36  may each be as defined for R 30b . 
     For example, R 1 , R 19 , R 19a , R 19b , R 2 , R 30a , R 30b , and R 31  to R 37  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, —SF 5 , a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl 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 2 -C 20  alkenyl group, a C 1 -C 20  alkoxy group, or a C 1 -C 20  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a 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 a 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 benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoisothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, an azacarbazolyl group, an azadibenzofuranyl group, or an azadibenzothiophenyl group, each unsubstituted or substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a deuterated C 2 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 1 -C 20  alkylthio group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a 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 benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoisothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, an azacarbazolyl group, an azadibenzofuranyl group, an azadibenzothiophenyl group, or a combination thereof; or 
     —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —Ge(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), —P(═O)(Q 8 )(Q 9 ), or —P(Q 8 )(Q 9 ). 
     Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group; a substituted or unsubstituted C 2 -C 60  alkynyl group; a substituted or unsubstituted C 1 -C 60  alkoxy group; a substituted or unsubstituted C 1 -C 60  alkylthio group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 0  alkyl aryl group, a substituted or unsubstituted C 7 -C 0  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     For example, Q 1  to Q 9  may each independently be: 
     deuterium, —F, —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, —CD 2 CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , —CH 2 CF 3 , —CH 2 CF 2 H, —CH 2 CFH 2 , —CHFCH 3 , —CHFCF 2 H, —CHFCFH 2 , —CHFCF 3 , —CF 2 CF 3 , —CF 2 CF 2 H, or —CF 2 CFH 2 ; or 
     an n-propyl group, an iso-propyl 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 at least one of deuterium, —F, a C 1 -C 10  alkyl group, a phenyl group, or a combination thereof. 
     In one or more embodiments, R 1 , R 19 , R 19a , R 19b , R 2 , R 30a , R 30b , and R 31  to R 37  may each independently be: 
     hydrogen, deuterium, —F, or a cyano group; 
     a C 1 -C 20  alkyl group that is unsubstituted or substituted with at least one of deuterium, —F, a cyano group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a fluorinated 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 fluorinated C 1 -C 10  heterocycloalkyl group, a (C 1 -C 20  alkyl)C 1 -C 10  heterocycloalkyl group, a phenyl group, a deuterated phenyl group, a fluorinated phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a fluorinated biphenyl group, a (C 1 -C 20  alkyl)biphenyl group, a dibenzofuranyl group, a deuterated dibenzofuranyl group, a fluorinated dibenzofuranyl group, a (C 1 -C 20  alkyl)dibenzofuranyl group, a dibenzothiophenyl group, a deuterated dibenzothiophenyl group, a fluorinated dibenzothiophenyl group, a (C 1 -C 20  alkyl)dibenzothiophenyl group, or a combination thereof; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a phenyl group, a biphenyl group, a naphthyl group, a pyridinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with at least one of deuterium, —F, a cyano group, a C 1 -C 20  alkyl group, a deuterated C 1 -C 20  alkyl group, a fluorinated C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 1 -C 20  alkylthio group, a deuterated C 1 -C 20  alkoxy group, a fluorinated C 1 -C 20  alkoxy group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a fluorinated 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 fluorinated C 1 -C 10  heterocycloalkyl group, a (C 1 -C 20  alkyl)C 1 -C 10  heterocycloalkyl group, a phenyl group, a deuterated phenyl group, a fluorinated phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a fluorinated biphenyl group, a (C 1 -C 20  alkyl)biphenyl group, a dibenzofuranyl group, a deuterated dibenzofuranyl group, a fluorinated dibenzofuranyl group, a (C 1 -C 20  alkyl)dibenzofuranyl group, a dibenzothiophenyl group, a deuterated dibenzothiophenyl group, a fluorinated dibenzothiophenyl group, a (C 1 -C 20  alkyl)dibenzothiophenyl group, or a combination thereof; or 
     —Si(Q 3 )(Q 4 )(Q 5 ) or —Ge(Q 3 )(Q 4 )(Q 5 ). 
     In one or more embodiments, R 37  in Formula 1 may be hydrogen, deuterium, a substituted or unsubstituted C 1 -C 60  alkyl 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 7 -C 0  alkyl aryl group, a substituted or unsubstituted C 7 -C 0  aryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     In one or more embodiments, at least one of R 1 , at least one of R 2 , R 30a , R 30b , R 37 , or a combination thereof may each independently be: 
     deuterium, —F, or a cyano group; 
     a C 1 -C 20  alkyl group that is unsubstituted or substituted with at least one of deuterium, —F, a cyano group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a fluorinated 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 fluorinated C 1 -C 10  heterocycloalkyl group, a (C 1 -C 20  alkyl)C 1 -C 10  heterocycloalkyl group, a phenyl group, a deuterated phenyl group, a fluorinated phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a fluorinated biphenyl group, a (C 1 -C 20  alkyl)biphenyl group, a dibenzofuranyl group, a deuterated dibenzofuranyl group, a fluorinated dibenzofuranyl group, a (C 1 -C 20  alkyl)dibenzofuranyl group, a dibenzothiophenyl group, a deuterated dibenzothiophenyl group, a fluorinated dibenzothiophenyl group, a (C 1 -C 20  alkyl)dibenzothiophenyl group, or a combination thereof; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a phenyl group, a biphenyl group, a naphthyl group, a pyridinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with at least one of deuterium, —F, a cyano group, a C 1 -C 20  alkyl group, a deuterated C 1 -C 20  alkyl group, a fluorinated C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 1 -C 20  alkylthio group, a deuterated C 1 -C 20  alkoxy group, a fluorinated C 1 -C 20  alkoxy group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a fluorinated 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 fluorinated C 1 -C 10  heterocycloalkyl group, a (C 1 -C 20  alkyl)C 1 -C 10  heterocycloalkyl group, a phenyl group, a deuterated phenyl group, a fluorinated phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a fluorinated biphenyl group, a (C 1 -C 20  alkyl)biphenyl group, a dibenzofuranyl group, a deuterated dibenzofuranyl group, a fluorinated dibenzofuranyl group, a (C 1 -C 20  alkyl)dibenzofuranyl group, a dibenzothiophenyl group, a deuterated dibenzothiophenyl group, a fluorinated dibenzothiophenyl group, a (C 1 -C 20  alkyl)dibenzothiophenyl group, or a combination thereof; or 
     —Si(Q 3 )(Q 4 )(Q 5 ) or —Ge(Q 3 )(Q 4 )(Q 5 ). 
     In one or more embodiments, R 1 , R 19 , R 19a , R 19b , R 2 , R 30a , R 30b , and R 31  to R 37  may each independently be hydrogen, deuterium, —F, —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a C 2 -C 10  alkenyl group, a C 1 -C 10  alkoxy group, a C 1 -C 10  alkylthio group, a group represented by one of Formulae 9-1 to 9-39, a group represented by one of Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with deuterium, a group represented by Formulae one of 9-1 to 9-39 in which at least one hydrogen is substituted with —F, a group represented by one of Formulae 9-201 to 9-237, a group represented by one of Formulae 9-201 to 9-237 in which at least one hydrogen is substituted with deuterium, a group represented by one of Formulae 9-201 to 9-237 in which at least one hydrogen is substituted with —F, a group represented by one of Formulae 10-1 to 10-129, a group represented by one of Formulae 10-1 to 10-129 in which at least one hydrogen is substituted with deuterium, a group represented by one of Formulae 10-1 to 10-129 in which at least one hydrogen is substituted with —F, a group represented by one of Formulae 10-201 to 10-350, a group represented by one of Formulae 10-201 to 10-350 in which at least one hydrogen is substituted with deuterium, a group represented by one of Formulae 10-201 to 10-350 in which at least one hydrogen is substituted with —F, —Si(Q 3 )(Q 4 )(Q 5 ), or —Ge(Q 3 )(Q 4 )(Q 5 ) (wherein Q 3  to Q 5  may each be the same as described herein): 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 9-1 to 9-39, 9-201 to 9-237, 10-1 to 10-129, and 10-201 to 10-350, * indicates a binding site to a neighboring atom, “Ph” indicates a phenyl group, “TMS” indicates a trimethylsilyl group, and “TMG” indicates a trimethylgermyl group. 
     The “group represented by one of Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with deuterium” and the “group represented by one of Formulae 9-201 to 9-237 in which at least one hydrogen is substituted with deuterium” may each be, for example, a group represented by one of Formulae 9-501 to 9-514 or 9-601 to 9-636: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The “group represented by one of Formulae 9-1 to 9-39 in which at least one hydrogen is substituted with —F” and the “group represented by one of Formulae 9-201 to 9-237 in which at least one hydrogen is substituted with —F” may each be, for example, a group represented by one of Formulae 9-701 to 9-710: 
     
       
         
         
             
             
         
       
     
     The “group represented by one of Formulae 10-1 to 10-129 in which at least one hydrogen is substituted with deuterium” and the “group represented by one of Formulae 10-201 to 10-350 in which at least one hydrogen is substituted with deuterium” may each be, for example, a group represented by one of Formulae 10-501 to 10-553: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The “group represented by one of Formulae 10-1 to 10-129 in which at least one hydrogen is substituted with —F” and the “group represented by one of Formulae 10-201 to 10-350 in which at least one hydrogen is substituted with —F” may each be, for example, a group represented by one of Formulae 10-601 to 10-617: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     a1 and a2 in Formula 1 each indicates the number of R 1  groups and the number of R 2  groups, respectively, and are each independently an integer from 0 to 20. For example, a1 and a2 may each independently be 0, 1, 2, or 3. 
     In Formula 1, the following proviso applies to a1 and a2: 
     i) a1 is not 0, and at least one of R 1  is —Ge(Q 3 )(Q 4 )(Q 5 ). 
     i) a2 is not 0, and at least one of R 2  is —Ge(Q 3 )(Q 4 )(Q 5 ); or 
     iii) a1 is not 0, and at least one of R 1  is —Ge(Q 3 )(Q 4 )(Q 5 ), and a2 is not 0, and at least one of R 2  is —Ge(Q 3 )(Q 4 )(Q 5 ). In other words, the organometallic compound represented by Formula 1 includes at least one group represented by the formula —Ge(Q 3 )(Q 4 )(Q 5 ). 
     In one or more embodiments, a1 in Formula 1 may not be 0, and at least one of R 1  may be —Ge(Q 3 )(Q 4 )(Q 5 ). 
     In one or more embodiments, a2 in Formula 1 may not be 0, and at least one of R 2  may be —Ge(Q 3 )(Q 4 )(Q 5 ). 
     In one or more embodiments, the organometallic compound represented by Formula 1 may include two groups represented by the formula —Ge(Q 3 )(Q 4 )(Q 5 ). 
     Meanwhile, the number of carbon atoms included in each of R 30a  and R 30b  in Formula 1 may each independently be 4 or greater, 5 or greater, or 6 or greater. 
     In one or more embodiments, R 30a  in Formula 1 may not be a methyl group. 
     In one or more embodiments, R 30b  in Formula 1 may not be a methyl group. 
     In one or more embodiments, R 30a  and R 30b  in Formula 1 may each not be a methyl group, simultaneously. 
     In one or more embodiments, R 30a  in Formula 1 may not be a tertiary butyl (tert-butyl) group. 
     In one or more embodiments, R 30b  in Formula 1 may not be a tert-butyl group. 
     In one or more embodiments, R 30a  and R 30b  in Formula 1 may not be a tert-butyl group, simultaneously. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may satisfy one of Condition A1 to Condition A6: 
     Condition A1 
     R 30a  in Formula 1 is a group represented by *—C(R 31 )(R 32 )(R 33 ), and 
     each of R 31  to R 33  includes one or more carbon atoms; 
     Condition A2 
     R 30a  in Formula 1 is a group represented by *—C(R 31 )(R 32 )(R 33 ), and 
     each of R 31  and R 33  includes one or more carbon atoms, and 
     R 32  is hydrogen, deuterium, or —F; 
     Condition A3 
     R 30a  in Formula 1 is a group represented by *—C(R 31 )(R 32 )(R 33 ), and 
     each of R 31  to R 33  includes at least one carbon atom, wherein at least one of R 31  to R 33  includes two or more carbon atoms; 
     Condition A4 
     R 30a  in Formula 1 is a group represented by *—C(R 31 )(R 32 )(R 33 ), 
     each of R 31  and R 33  includes one or more carbon atoms, wherein at least one of R 31  and R 33  includes two or more carbon atoms; and 
     R 32  is hydrogen, deuterium, or —F; 
     Condition A5 
     R 30a  in Formula 1 is a group represented by *—C(R 31 )(R 32 )(R 33 ); and 
     R 31  to R 33  are each independently hydrogen, deuterium, or —F, wherein at least one of R 31  to R 33  is deuterium or —F; 
     Condition A6 
     R 30a  in Formula 1 is a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 60  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkyl aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl 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, the organometallic compound represented by Formula 1 may satisfy one of Condition B1 to Condition B6: 
     Condition B1 
     R 30b  in Formula 1 is a group represented by *—C(R 34 )(R 35 )(R 36 ), and 
     each of R 34  to R 36  includes one or more carbon atoms; 
     Condition B2 
     R 30b  in Formula 1 is a group represented by *—C(R 34 )(R 35 )(R 36 ); 
     each of R 34  and R 36  includes one or more carbon atoms, and 
     R 35  is hydrogen, deuterium, or —F; 
     Condition B3 
     R 30b  in Formula 1 is a group represented by *—C(R 34 )(R 35 )(R 36 ); and 
     each of R 34  to R 36  includes one or more carbon atoms, wherein at least one of R 34  to R 36  includes two or more carbon atoms; 
     Condition B4 
     R 30b  in Formula 1 is a group represented by *—C(R 34 )(R 35 )(R 36 ), 
     each of R 34  and R 36  includes one or more carbon atoms, wherein at least one of R 34  and R 36  includes two or more carbon atoms, and 
     R 35  is hydrogen, deuterium, or —F; 
     Condition B5 
     R 30b  in Formula 1 is a group represented by *—C(R 34 )(R 35 )(R 36 ), and 
     R 34  to R 36  are each independently hydrogen, deuterium, or —F, wherein at least one of R 34  to R 36  is deuterium or —F; 
     Condition B6 
     R 30b  in Formula 1 is 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 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkyl aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl 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, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 1 may be a group represented by one of Formulae CY1(1) to CY1(6): 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae CY1(1) to CY1(6), 
     Y 9  and ring CY 1  may each be as described herein, 
     Y 1  to Y 4  may each independently be C or N, 
     * may indicate a binding site to iridium in Formula 1, and 
     *″ may indicate a binding site to ring CY 2  in Formula 1. 
     For example, Y 1  to Y 4  in Formulae CY1(1) to CY1(6) may each be C. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 1 may be a group represented by one of Formulae CY1-1 to CY1-6: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae CY1-1 to CY1-6, 
     Y 9  may be as described in the present specification, 
     R 11  to R 18  may each be as described in connection with R 1 , 
     R 11  and R 12  may optionally be linked to each other 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 13  and R 14  may optionally be linked to each other 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 15  to R 18  may optionally be linked to each other 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 as described in connection with R 1 , 
     * may indicate a binding site to iridium in Formula 1, and 
     *″ may indicate a binding site to ring CY 2  in Formula 1. 
     For example, 
     at least one of R 13 , R 14 , R 15 , R 16 , R 17 , and R 18  in Formulae CY1-1 and CY1-6 may be —Ge(Q 3 )(Q 4 )(Q 5 ), 
     at least one of R 11 , R 12 , R 15 , R 16 , R 17 , and R 18  in Formulae CY1-2 and CY1-5 may be —Ge(Q 3 )(Q 4 )(Q 5 ), and 
     at least one of R 11 , R 14 , R 15 , R 16 , R 17 , and R 18  in Formulae CY1-3 and CY1-4 may be —Ge(Q 3 )(Q 4 )(Q 5 ). 
     As another example, R 15  in Formulae CY1-1 to CY1-6 may not be hydrogen. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 1 may be a group represented by one of Formulae CY2(1) to CY2(22) (for example, a group represented by one of Formulae CY2(1) to CY2(21)): 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae CY2(1) to CY2(22), 
     X 2  may be as described herein, 
     * may indicate a binding site to iridium in Formula 1, and 
     *″ may indicate a binding site to one of Y 1  to Y 4  in Formula 1. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 1 may be a group represented by one of Formulae CY2-1 to CY2-6: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae CY2-1 to CY2-6, 
     X 2  may be as described herein, 
     R 21  to R 26  may each be as described in connection with R 2 , 
     two or more of R 21  to R 26  may optionally be linked to each other 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  a may be as described in connection with R 1 , 
     * may indicate a binding site to iridium in Formula 1, and 
     *″ may indicate a binding site to one of Y 1  to Y 4  in Formula 1. 
     For example, 
     at least one of R 21  to R 26  in Formula CY2-1 may be —Ge(Q 3 )(Q 4 )(Q 5 ), and 
     at least one of R 21  to R 24  in Formulae CY2-2 to CY2-6 may be —Ge(Q 3 )(Q 4 )(Q 5 ). 
     In one or more embodiments, 
     at least one of R 21  to R 26  in Formula CY2-1 may not be hydrogen, and 
     at least one of R 21  to R 24  in Formulae CY2-2 to CY2-6 may not be hydrogen. 
     In one or more embodiments, a group represented by 
     
       
         
         
             
             
         
       
     
     in Formula 1 may be a group represented by one of Formulae CY2-A to CY2-E: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae CY2-A to CY2-E, 
     X 2  may be as described in the present specification, and 
     R 22  may be: 
     a C 1 -C 20  alkyl group that is unsubstituted or substituted with at least one of deuterium, —F, a cyano group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a fluorinated C 3 -C 10  cycloalkyl group, a (C 1 -C 20  alkyl)C 3 -C 10  cycloalkyl group, or a combination thereof; 
     a C 3 -C 10  cycloalkyl group, a phenyl group, or a biphenyl group, each unsubstituted or substituted with at least one of deuterium, —F, a cyano group, a C 1 -C 20  alkyl group, a deuterated C 1 -C 20  alkyl group, a fluorinated C 1 -C 20  alkyl group, a C 3 -C 10  cycloalkyl group, a deuterated C 3 -C 10  cycloalkyl group, a fluorinated C 3 -C 10  cycloalkyl group, a (C 1 -C 20  alkyl)C 3 -C 10  cycloalkyl group, or a combination thereof; or 
     —Si(Q 3 )(Q 4 )(Q 5 ) or —Ge(Q 3 )(Q 4 )(Q 5 ), 
     * may indicate a binding site to iridium in Formula 1, and 
     *″ may indicate a binding site to one of Y 1  to Y 4  in Formula 1. 
     In one or more embodiments, the organometallic compound may be represented by at least one of Formulae 1-1 or 1-2: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 1-1 and 1-2, 
     Y 9 , R 30a , R 30b , and R 37  may each be as described in the present specification, 
     R 11  to R 18  may each be as described in connection with R 1 , 
     R 21  to R 26  may each be as described in connection with R 2 , 
     at least one of R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 21 , R 22 , R 23 , R 24 , R 25 , and R 26  in Formula 1-1 may be —Ge(Q 3 )(Q 4 )(Q 5 ), 
     at least one of R 11 , R 12 , R 15 , R 16 , R 17 , R 18 , R 21 , R 22 , R 23 , R 24 , R 25 , and R 26  in Formula 1-2 may be —Ge(Q 3 )(Q 4 )(Q 5 ), 
     two or more of R 11  to R 18  may optionally be linked to each other 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 21  to R 26  may optionally be linked to each other 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 30a , R 30b , and R 37  may optionally be linked to each other 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 as described in connection with R 1  herein. 
     In one or more embodiments, R 37  in Formula 1 may be hydrogen or deuterium. 
     In one or more embodiments, R 30a  and R 30b  in Formula 1 may be identical to each other. 
     In one or more embodiments, R 30a  and R 30b  in Formula 1 may be different from each other. 
     In one or more embodiments, Formula 1 may include at least one deuterium. 
     In one or more embodiments, Formula 1 may include at least one fluoro group (—F). 
     In one or more embodiments, at least one of R 1 (s) in the number of a1 in Formula 1 may include a fluoro group (—F). 
     In one or more embodiments, R 1  in Formula 1 may not include a fluoro group (—F). 
     In one or more embodiments, at least one of R 2  in Formula 1 may include a fluoro group (—F). 
     In one or more embodiments, R 2  in Formula 1 may not include a fluoro group (—F). 
     In Formulae, i) two or more of a plurality of R 1  are optionally be linked to each other 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 R 2  are optionally linked to each other 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 R 1  and R 2  are optionally linked to each other 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/or iv) two or more of R 30a , R 30b , and R 37  are optionally linked to each other 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 . In some embodiments, two or more of R 31  to R 33  may optionally be linked to each other 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/or two or more of R 34  to R 36  may optionally be linked to each other 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 as described in connection with R 1 . 
     In one or more embodiments, the organometallic compound represented by Formula 1 may emit a red light or a green light, for example, a red light or a green light having a maximum emission wavelength of about 500 nanometers (nm) or greater, or about 500 nm to about 730 nm. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may emit a red light, for example, a red light having a maximum emission wavelength of about 580 nm to about 730 nm, or about 600 nm to about 730 nm. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may emit a light having a maximum emission wavelength of about 525 nm to about 650 nm, about 550 nm to about 650 nm, about 575 nm to about 650 nm, about 600 nm to about 650 nm, about 610 nm to about 645 nm, or about 620 nm to about 645 nm. 
     In one or more embodiments, the organometallic compound represented by Formula 1 may emit a light having a full width at half maximum (FWHM) of about 25 nm to about 50 nm, about 30 nm to about 45 nm, or about 30 nm to about 43 nm. 
     In one or more embodiments, the organometallic compound may be at least one of Compounds 1 to 33: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     “TMG” in Compounds 1 to 33 may be trimethylgermyl group. 
     The organometallic compound represented by Formula 1 includes a group represented by 
     
       
         
         
             
             
         
       
     
     as described herein. In addition, in Formula 1, 
     i) a1 is not 0, and at least one of R 1  is —Ge(Q 3 )(Q 4 )(Q 5 ). 
     i) a2 is not 0, and at least one of R 2  is —Ge(Q 3 )(Q 4 )(Q 5 ); or 
     iii) a1 is not 0, and at least one of R 1  is —Ge(Q 3 )(Q 4 )(Q 5 ), and a2 is not 0, and at least one of R 2  is —Ge(Q 3 )(Q 4 )(Q 5 ). Accordingly, due to increase in hyper-conjugation of a pi-bond of a ligand represented by 
     
       
         
         
             
             
         
       
     
     and Ge in a group represented by —Ge(Q 3 )(Q 4 )(Q 5 ), the amount of metal to ligand charge transfer may be increased. Accordingly, the PLQY and degree of orientation of the organometallic compound represented by Formula 1 may be increased and non-emission transition may be decreased, thereby increasing out-coupling, which is an external emission efficiency factor. Thus, emission efficiency of an electronic device, for example, a light-emitting device, including the organometallic compound may be improved. 
     A highest occupied molecular orbital (HOMO) energy level, a lowest unoccupied molecular orbital (LUMO) energy level, and a triplet (T 1 ) energy level of some compounds of the organometallic compound represented by Formula 1 were calculated using a density functional theory (DFT) method of the Gaussian 09 program with the molecular structure optimized at the B3LYP level, and results thereof are shown in Table 1. The energy levels are expressed in electron volts (eV). 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 HOMO 
                 LUMO 
                 T 1   
               
               
                   
                 Compound No. 
                 (eV) 
                 (eV) 
                 (eV) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 1 
                 −5.220 
                 −2.092 
                 1.991 
               
               
                   
                 4 
                 −5.194 
                 −2.022 
                 1.995 
               
               
                   
                 7 
                 −5.289 
                 −2.132 
                 2.016 
               
               
                   
                 8 
                 −5.203 
                 −2.109 
                 1.977 
               
               
                   
                 10 
                 −5.175 
                 −1.982 
                 1.978 
               
               
                   
                 14 
                 −5.203 
                 −2.103 
                 1.978 
               
               
                   
                 15 
                 −5.238 
                 −2.121 
                 1.987 
               
               
                   
                 18 
                 −5.189 
                 −2.094 
                 1.972 
               
               
                   
                 19 
                 −5.311 
                 −2.206 
                 2.001 
               
               
                   
                 22 
                 −5.188 
                 −2.073 
                 1.982 
               
               
                   
                   
               
            
           
         
       
     
     From Table 1, it was confirmed that the organometallic compound represented by Formula 1 has suitable electrical characteristics for use as a dopant in an electronic device, for example, a light-emitting device. 
     For example, in one or more embodiments, an absolute value of a HOMO energy level of the organometallic compound represented by Formula 1 may be about 5.100 eV to about 5.400 eV, for example, about 5.175 eV to about 5.311 eV. 
     In one or more embodiments, an absolute value of a LUMO energy level of the organometallic compound represented by Formula 1 may be about 1.900 eV to about 2.300 eV, for example, about 1.982 eV to about 2.206 eV. 
     For example, a T 1  energy level of the organometallic compound represented by Formula 1 may be about 1.900 eV to about 2.100 eV, for example, about 1.972 eV to about 2.016 eV. 
     A method of synthesizing the organometallic compound represented by Formula 1 may be apparent to one of ordinary skill in the art and by referring to Synthesis Examples provided herein. 
     Therefore, the organometallic compound represented by Formula 1 may be suitable for use as a dopant in an organic layer of an organic light-emitting device, for example, an emission layer in the organic layer. Thus, according to one or more embodiments, there is provided a light-emitting device (for example, an organic light-emitting device) including a first electrode; a second electrode; and an organic layer arranged between the first electrode and the second electrode, wherein the organic layer includes an emission layer, and wherein the organic layer further includes at least one organometallic compound represented by Formula 1. 
     The light-emitting device has the organic layer including at least one of the organometallic compounds represented by Formula 1 as described herein, and thus, may have excellent driving voltage, excellent external quantum efficiency, FWHM of a relatively narrow EL spectrum emission peak, and excellent lifespan characteristics. 
     The organometallic compound represented by Formula 1 may be used between a pair of electrodes of the light-emitting device. For example, the emission layer may include at least one of the organometallic compounds represented by Formula 1. For example, the organometallic compound may serve as a dopant and the emission layer may further include a host (in other words, an amount (for example, a weight) of the at least one organometallic compound represented by Formula 1 in the emission layer may be less than an amount (for example, a weight) of the host in the emission layer). For example, an amount of the host in the emission layer may be greater than an amount of the at least one organometallic compound represented by Formula 1 in the emission layer. 
     The emission layer (or the light-emitting device including the emission layer) including the at least one organometallic compound represented by Formula 1 may emit a red light or a green light, for example, a red light or a green light having a maximum emission wavelength of about 500 nm or greater, for example, about 500 nm to about 730 nm. For example, the emission layer may emit a red light, for example, a red light having a maximum emission wavelength of about 580 nm to about 730 nm, or about 600 nm to about 730 nm. 
     In one or more embodiments, the emission layer (or the light-emitting device including the emission layer) including the at least one organometallic compound represented by Formula 1 may emit a light having a maximum emission wavelength of about 525 nm to about 650 nm, about 550 nm to about 650 nm, about 575 nm to about 650 nm, about 600 nm to about 650 nm, about 610 nm to about 645 nm, or about 620 nm to about 645 nm. 
     In one or more embodiments, the emission layer (or the light-emitting device including the emission layer) including the at least one organometallic compound represented by Formula 1 may emit a light having FWHM of about 25 nm to about 50 nm, about 30 nm to about 45 nm, or about 30 nm to about 43 nm. 
     The maximum emission wavelength and FWHM may be evaluated from an EL spectrum of the light-emitting device. 
     In one or more embodiments, the emission layer (or the light-emitting device including the emission layer) including the at least one organometallic compound represented by Formula 1 may emit a red light. 
     The wording “(organic layer) includes at least one organometallic compound(s)” used herein may be to mean that the (organic layer) may include one kind of organometallic compound represented by Formula 1 or two or more different kinds of organometallic compound, each represented by Formula 1. 
     For example, the organic layer may include Compound 1 only as the organometallic compound. In this regard, Compound 1 may be present in the emission layer of the light-emitting device. Alternatively, the organic layer may include Compound 1 and Compound 2 as the organometallic compound. At this time, Compound 1 and Compound 2 may be present in an identical layer (for example, both Compound 1 and Compound 2 may be present in the emission layer). 
     The first electrode may be an anode, which is a hole injection electrode, and the second electrode may be a cathode, which is an electron injection electrode. Alternatively, 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 light-emitting device, the first electrode may be an anode, the second electrode may be a cathode, the organic layer may further include a hole transport region arranged between the first electrode and the emission layer and an electron transport region arranged between the emission layer and the second electrode, the hole transport region may include a hole injection layer, a hole transport layer, an electron blocking layer, a buffer layer, or a combination thereof, and the electron transport region may include a hole blocking layer, an electron transport layer, an electron injection layer, or a combination thereof. 
     The term “organic layer” as used herein refers to a single layer and/or a plurality of layers arranged between the first electrode and the second electrode of the light-emitting device. The “organic layer” may include not only organic compounds but also may include organometallic complexes including metals. 
     The FIGURE is a schematic cross-sectional view of an organic light-emitting device  10  which is a light-emitting device, according to one or more embodiments. Hereinafter, the structure and manufacturing method of the organic light-emitting device  10  according to one or more embodiments will be described in further detail with reference to the FIGURE. The organic light-emitting device  10  has a structure in which a first electrode  11 , an organic layer  15 , and a second electrode  19  are sequentially stacked in this stated order. 
     A substrate may be additionally disposed under the first electrode  11  or on the second electrode  19 . For use as the substrate, any substrate that is used in organic light-emitting devices available in the art may be used, and for example, a glass substrate or a transparent plastic substrate, each having excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and/or water resistance, may be used. 
     The first electrode  11  may be, for example, 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 materials with a high work function to facilitate hole injection. The first electrode  11  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. The material for forming the first electrode  11  may include indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), zinc oxide (ZnO), or a combination thereof. Alternatively, the material for forming the first electrode  11  may include magnesium (Mg), aluminum (Al), silver (Ag), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), or a combination thereof. 
     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, an electron transport region, or a combination thereof. 
     The hole transport region may be arranged between the first electrode  11  and the emission layer. 
     The hole transport region may include a hole injection layer, a hole transport layer, an electron blocking layer, a buffer layer, or a combination thereof. 
     The hole transport region may include a hole injection layer only or a hole transport layer only. Alternatively, 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, wherein, for each structure, respective layer are sequentially stacked in this stated order from the first electrode  11 . 
     When the hole transport region includes a hole injection layer, the hole injection layer may be formed on the first electrode  11  by using various methods, such as vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) deposition, or the like. 
     When the hole injection layer is formed by vacuum deposition, the deposition conditions may vary depending on 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 degree in a range of about 10 −8  torr to about 10-3 torr, and a deposition rate of about 0.01 angstroms per second (Å/sec) to about 100 Å/sec. 
     When the hole injection layer is formed by spin coating, the coating conditions may vary depending on 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 coating conditions may include a coating speed of about 2,000 revolutions per minute (rpm) to about 5,000 rpm and a heat treatment of about 80° C. to about 200° C. for removing a solvent after coating. 
     Conditions for forming the hole transport layer and the electron blocking layer may be similar to or the same as the conditions for forming the hole injection layer. 
     The hole transport region may include at least one of 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4′,4″-tris{N-(2-naphthyl)-N-phenylamino}-triphenylamine (2-TNATA), N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (NPB), p-NPB, N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD), spiro-TPD, spiro-NPB, methylated NPB, 4,4′-cyclohexylidene bis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), 4,4′-bis[N,N′-(3-tolyl)amino]-3,3′-dimethylbiphenyl (HMTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzenesulfonic acid (PANI/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), a compound represented by Formula 201, a compound represented by Formula 202, or a combination thereof, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formula 201, Ar 101  and Ar 102  may each independently be a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, or a pentacenylene group, each unsubstituted or substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a C 3 -C 10  cycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 0  alkyl aryl group, a C 7 -C 60  aryl alkyl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 7 -C 0  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or a combination thereof. 
     In Formula 201, xa and xb may each independently be an integer from 0 to 5, or may each independently be 0, 1, or 2. For example, xa may be 1, and xb may be 0. 
     In Formulae 201 and 202, R 101  to R 108 , R 111  to R 119 , and R 121  to R 124  may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, etc.), a C 1 -C 10  alkoxy group (for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, etc.), or a C 1 -C 10  alkylthio group; 
     a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, or a C 1 -C 10  alkylthio group, each unsubstituted or substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, or a combination thereof; or 
     a phenyl group, a naphthyl group, an anthracenyl group, a fluorenyl group, or a pyrenyl group, each unsubstituted or substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, a C 1 -C 10  alkylthio group, or a 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 at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 1 -C 20  alkylthio group, a phenyl group, a naphthyl group, an anthracenyl group, a pyridinyl group, or a combination thereof. 
     In one or more embodiments, a compound represented by Formula 201 may be represented by Formula 201A: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 201A, R 101 , R 111 , R 112 , and R 109  may each be as described herein. 
     For example, the hole transport region may include one of Compounds HT1 to HT21, or a combination thereof, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the hole transport region may be 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 a combination thereof, a thickness of the hole injection layer may be about 100 Å to about 10,000 Å, for example, about 100 Å to about 1,000 Å, and a thickness of the hole transport layer may be about 50 Å to about 2,000 Å, for example, about 100 Å to about 1,500 Å. Without wishing to be bound to theory, when thicknesses of the hole transport region, the hole injection layer, and the hole transport layer are within the ranges as described herein, satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The hole transport region may further include, in addition to the materials as described herein, a charge-generation material for improving 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 include a quinone derivative, a metal oxide, a cyano group-containing compound, or a combination thereof. For example, the p-dopant may include a quinone derivative such as tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ), 1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F6-TCNNQ), or the like; a metal oxide, such as a tungsten oxide, a molybdenum oxide, or the like; a cyano group-containing compound, such as Compound HT-D1 or the like; or a combination thereof, but embodiments are not limited thereto. 
     
       
         
         
             
             
         
       
     
     The hole transport region may further include a buffer layer. 
     The buffer layer may compensate for an optical resonance distance according to a wavelength of light emitted from the emission layer, thereby increasing the efficiency. 
     Meanwhile, when the hole transport region includes an electron blocking layer, a material for forming the electron blocking layer may include a material that may be used in the hole transport region as described herein, a host material as described herein, or a combination thereof. For example, when the hole transport region includes an electron blocking layer, mCP, Compound HT21 described herein, or a combination thereof may be used as the material for forming the electron blocking layer. 
     The emission layer may be formed on the hole transport region by using various methods, such as vacuum deposition, spin coating, casting, or LB deposition. 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 material that is used. 
     The emission layer may include a host and a dopant, and the dopant may include at least one of the organometallic compounds represented by Formula 1 as described herein. 
     In one or more embodiments, the host may include at least one of 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), 3-tert-butyl-9,10-di(naphth-2-yl)anthracene (TBADN), 9,10-di(naphthalen-2-yl)anthracene (ADN) (also referred to as “DNA”), 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), 4,4′-bis(9-carbazolyl)-2,2′-dimethylbiphenyl (CDBP), 1,3,5-tris(carbazol-9-yl)benzene (TCP), 1,3-bis(N-carbazolyl)benzene (mCP), Compound H50, Compound H51, Compound H52, or a combination thereof, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     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. Alternatively, 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 a white light, and various modifications are possible. 
     When the emission layer includes a host and a dopant, an amount of a dopant may be 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 about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. Without wishing to be bound to theory, when the thickness of the emission layer is within the range, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Next, the 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 a 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. 
     The conditions for forming a hole blocking layer, an electron transport layer, and an electron injection layer of the electron transport region may be similar 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, at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)aluminum (BAlq), or a combination thereof, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
     
     Alternatively, the hole blocking layer may include the host, a material for forming the electron transport layer, a material for forming the electron injection layer, or a combination thereof. 
     A thickness of the hole blocking layer may be about 20 Å to about 1,000 Å, for example, about 30 Å to about 600 Å. Without wishing to be bound to theory, when the thickness of the hole blocking layer is within the range, excellent hole blocking characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport layer may include 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), tris(8-hydroxy-quinolinato)aluminum (Alq 3 ), bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)aluminum (BAlq), 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ), or a combination thereof, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
     
     Alternatively, the electron transport layer may include at least one of Compounds ET1 to ET25, or a combination thereof, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the electron transport layer may be about 100 Å to about 1,000 Å, for example, about 150 Å to about 500 Å. Without wishing to be bound to theory, when the thickness of the electron transport layer is within the range, excellent electron transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport layer may include, in addition to the materials described herein, a metal-containing material. 
     The metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 or ET-D2, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
     
     In one or more embodiments, the electron transport region may include an electron injection layer that facilitates electron injection from the second electrode  19 . 
     The electron injection layer may include at least one of LiF, NaCl, CsF, Li 2 O, BaO, or a combination thereof. 
     A thickness of the electron injection layer may be about 1 Å to about 100 Å, for example, about 3 Å to about 90 Å. Without wishing to be bound to theory, when the thickness of the electron injection layer is within the range described above, satisfactory electron injection characteristics may be obtained without a 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 metal, an alloy, an electrically conductive compound, or a combination thereof, which have a relatively low work function. Examples of the material for forming the second electrode  19  may include lithium (Li), magnesium (Mg), aluminum (Al), silver (Ag), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), and magnesium-silver (Mg—Ag). Alternatively, to obtain a top-emission type light-emitting device, various modifications are possible, and for example, a transmissive electrode formed using ITO or IZO may be used as the second electrode  19 . 
     Hereinbefore, the light-emitting device has been described in further detail with reference to the FIGURE, but the embodiments are not limited thereto. 
     According to one or more embodiments, the light-emitting device may be included in an electronic apparatus. Therefore, also provided is an electronic apparatus including the light-emitting device. The electronic apparatus may include, for example, a display, lighting, a sensor, or the like, but embodiments are not limited thereto. 
     According to one or more embodiments, there is provided a diagnostic composition including at least one organometallic compound represented by Formula 1. 
     The organometallic compound represented by Formula 1 provides a high emission efficiency, and thus, the diagnostic composition including the at least one organometallic compound may have a high diagnostic efficiency. 
     The diagnostic composition may be used in various applications including a diagnosis kit, a diagnosis reagent, a biosensor, a biomarker, or the like, but embodiments are not limited thereto. 
     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 may include a methyl group, an ethyl group, an n-propyl group, an iso-propyl 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 iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, or a tert-decyl group, each unsubstituted or substituted with at least one of a methyl group, an ethyl group, an n-propyl group, an iso-propyl 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 iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, or the like, or a combination thereof. For example, Formula 9-33 is a branched C 6  alkyl group, for example, a tert-butyl group that is substituted with two methyl groups. 
     The term “C 1 -C 60  alkoxy group” as used herein refers to a monovalent group having the formula of —OA 101  (where 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 as used herein may include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, or the like. 
     The term “C 2 -C 60  alkenyl group” as used herein has a structure including at least one carbon-carbon double bond in the middle or at the terminus of the C 2 -C 60  alkyl group, and non-limiting examples thereof include an ethenyl group, a propenyl group, a butenyl group, or the like. 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 has a structure including at least one carbon-carbon triple bond in the middle or at the terminus of the C 2 -C 60  alkyl group, and non-limiting examples thereof include an ethynyl group, a propynyl group, or the like. 
     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 cyclic 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 may include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group (a bicyclo[2.2.1]heptyl group), a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.2]octyl group, or the like. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent saturated cyclic group that includes at least one heteroatom selected from N, O, P, Si, S, Se, Ge, and B as a ring-forming atom, and 1 to 10 carbon atoms as ring-forming 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 may include a silolanyl group, a silinanyl group, tetrahydrofuranyl group, a tetrahydro-2H-pyranyl group, a tetrahydrothiophenyl group, or the like. 
     The term “C 3 -C 10  cycloalkenyl group” as used herein refers to a monovalent monocyclic group including 3 to 10 carbon atoms, at least one carbon-carbon double bond in its ring, and no aromaticity, and non-limiting examples thereof include a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, or the like. 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 1 -C 10  heterocycloalkenyl group” as used herein refers to a monovalent monocyclic group that has at least one heteroatom selected from N, O, P, Si, S, Se, Ge, and B as a ring-forming atom, 1 to 10 carbon atoms as ring-forming atoms, and at least one double bond in its ring. Non-limiting examples of the C 1 -C 10  heterocycloalkenyl group include a 2,3-dihydrofuranyl group, a 2,3-dihydrothiophenyl group, or the like. The term “C 1 -C 10  heterocycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkenyl group. 
     The term “C 6 -C 60  aryl group” as used herein refers to a monovalent group that includes 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 that includes a carbocyclic aromatic system having 6 to 60 carbon atoms. Non-limiting examples of the C 6 -C 60  aryl group may include a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, a chrysenyl group, or the like. When the C 6 -C 60  aryl group and the C 6 -C 60  arylene group each include at least two rings, the at least two rings may be fused to each other. 
     The term “C 7 -C 0  alkyl aryl group” as used herein refers to a C 6 -C 60  aryl group that is substituted with at least one C 1 -C 60  alkyl group. 
     The term “C 7 -C 0  aryl alkyl group” as used herein refers to a C 1 -C 60  alkyl group that is substituted with at least one C 6 -C 60  aryl group. 
     The term “C 1 -C 60  heteroaryl group” as used herein refers to a monovalent group having at least one heteroatom selected from N, O, P, Si, S, Se, Ge, and B as a ring-forming atom and a cyclic aromatic system having 1 to 60 carbon atoms, and the term “C 1 -C 60  heteroarylene group” as used herein refers to a divalent group having at least one heteroatom selected from N, O, P, Si, S, Se, Ge, and B as a ring-forming atom and a cyclic aromatic system having 1 to 60 carbon atoms. Non-limiting examples of the C 1 -C 60  heteroaryl group may include a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, an isoquinolinyl group, or the like. 
     When the C 1 -C 60  heteroaryl group and the C 1 -C 60  heteroarylene group each include at least two rings, the at least two rings may be fused to each other. 
     The term “C 2 -C 60  alkyl heteroaryl group” as used herein refers to a C 1 -C 60  heteroaryl group that is substituted with at least one C 1 -C 60  alkyl group. 
     The term “C 2 -C 60  heteroaryl alkyl group” as used herein refers to a C 1 -C 60  alkyl group that is substituted with at least one C 1 -C 60  heteroaryl group. 
     The term “C 6 -C 60  aryloxy group” as used herein indicates —OA 102  (wherein A 102  is the C 6 -C 60  aryl group), the term “C 6 -C 60  arylthio group” as used herein indicates —SA 103  (wherein A 103  is the C 6 -C 60  aryl group), and the term “C 1 -C 60  alkylthio group” as used herein indicates —SA 104  (wherein A 104  is the C 1 -C 60  alkyl group). 
     The term “C 1 -C 60  heteroaryloxy group” as used herein indicates —OA 102′  (wherein A 102′  is the C 1 -C 60  heteroaryl group), and the term “C 1 -C 60  heteroarylthio group” as used herein indicates —SA 103′  (wherein A 103′  is the C 1 -C 60  heteroaryl group). 
     The term “monovalent non-aromatic condensed polycyclic group” as used herein refers to a monovalent group having two or more rings condensed with each other, only carbon atoms (for example, having 8 to 60 carbon atoms) as ring-forming atoms, and no aromaticity in its molecular structure. Non-limiting examples of the monovalent non-aromatic condensed polycyclic group may include a fluorenyl group or the like. The term “divalent non-aromatic condensed polycyclic group” as used herein refers to a divalent group having the same structure as a monovalent non-aromatic condensed polycyclic group. 
     The term “monovalent non-aromatic condensed heteropolycyclic group” as used herein refers to a monovalent group having two or more rings condensed with each other, a heteroatom selected from N, O, P, Si, S, Se, Ge, and B, other than carbon atoms as a ring-forming atom, and no aromaticity in its molecular structure. Non-limiting examples of the monovalent non-aromatic condensed heteropolycyclic group may include a carbazolyl group or the like. The term “divalent non-aromatic condensed heteropolycyclic group” as used herein refers to a divalent group having the same structure as a monovalent non-aromatic condensed heteropolycyclic group. 
     The term “C 5 -C 30  carbocyclic group” as used herein refers to a saturated or unsaturated cyclic group including 5 to 30 carbon atoms only as ring-forming atoms. The C 5 -C 30  carbocyclic group may be a monocyclic group or a polycyclic group. Non-limiting examples of the “C 5 -C 30  carbocyclic group (unsubstituted or substituted with at least one R 10a )” may include an adamantane group, a norbornane group (a bicyclo[2.2.1]heptane group), a norbornene group, a bicyclo[1.1.1]pentane group, a bicyclo[2.1.1]hexane 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, a cyclopentadiene group, a fluorene group, or the like (each 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 heteroatom selected from N, O, P, Si, Se, Ge, B, and S, other than 1 to 30 carbon atoms. The C 1 -C 30  heterocyclic group may be a monocyclic group or a polycyclic group. Non-limiting examples of the “C 1 -C 30  heterocyclic group (unsubstituted or substituted with at least one R 10a )” may include 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, 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, a 9H-fluoren-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-fluoren-9-one group, an azadibenzothiophene 5,5-dioxide group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a 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, or the like (each unsubstituted or substituted with at least one R 10a ). 
     The terms “fluorinated C 1 -C 60  alkyl group (or fluorinated C 1 -C 20  alkyl group or the like),” “fluorinated C 3 -C 10  cycloalkyl group,” “fluorinated C 1 -C 10  heterocycloalkyl group,” and “fluorinated phenyl group” as used herein respectively refer to a C 1 -C 60  alkyl group (or a C 1 -C 20  alkyl group or the like), a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, and a phenyl group, each substituted with at least one fluoro group (—F). For example, the term “fluorinated C 1  alkyl group (that is, fluorinated methyl group)” includes —CF 3 , —CF 2 H, and —CFH 2 . The terms “fluorinated C 1 -C 60  alkyl group (or fluorinated C 1 -C 20  alkyl group or the like),” “fluorinated C 3 -C 10  cycloalkyl group,” “fluorinated C 1 -C 10  heterocycloalkyl group,” or “fluorinated phenyl group” as used herein may respectively refer to, i) a fully fluorinated C 1 -C 60  alkyl group (or a fully fluorinated C 1 -C 20  alkyl group or the like), a fully fluorinated C 3 -C 10  cycloalkyl group, a fully fluorinated C 1 -C 10  heterocycloalkyl group, or a fully fluorinated a phenyl group, wherein, in each group, all hydrogen atoms included therein are substituted with a fluoro group, or ii) a partially fluorinated C 1 -C 60  alkyl group (or a partially fluorinated C 1 -C 20  alkyl group or the like), a partially fluorinated C 3 -C 10  cycloalkyl group, a partially fluorinated C 1 -C 10  heterocycloalkyl group, or a partially fluorinated phenyl group, wherein, in each group, at least one but not all of the hydrogen atoms included therein are substituted with a fluoro group. 
     The terms “deuterated C 1 -C 60  alkyl group (or deuterated C 1 -C 20  alkyl group or the like),” “deuterated C 3 -C 10  cycloalkyl group,” “deuterated C 1 -C 10  heterocycloalkyl group,” and “deuterated phenyl group” as used herein respectively refer to a C 1 -C 60  alkyl group (or a C 1 -C 20  alkyl group or the like), a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, and a phenyl group, each substituted with at least one deuterium. For example, the “deuterated C 1  alkyl group (that is, a deuterated methyl group)” may include —CD 3 , —CD 2 H, and —CDH 2 , and examples of the “deuterated C 3 -C 10  cycloalkyl group” are, for example, Formula 10-501 and the like. The “deuterated C 1 -C 60  alkyl group (or deuterated C 1 -C 20  alkyl group or the like),” “deuterated C 3 -C 10  cycloalkyl group,” “deuterated C 1 -C 10  heterocycloalkyl group,” or “deuterated phenyl group” may respectively refer to i) a fully deuterated C 1 -C 60  alkyl group (or a fully deuterated C 1 -C 20  alkyl group or the like), a fully deuterated C 3 -C 10  cycloalkyl group, a fully deuterated C 1 -C 10  heterocycloalkyl group, or a fully deuterated phenyl group, wherein, in each group, all hydrogen atoms included therein are substituted with deuterium, or ii) a partially deuterated C 1 -C 60  alkyl group (or a partially deuterated C 1 -C 20  alkyl group or the like), a partially deuterated C 3 -C 10  cycloalkyl group, a partially deuterated C 1 -C 10  heterocycloalkyl group, or a partially deuterated phenyl group, wherein, in each group, at least one but not all of the hydrogen atoms included therein are substituted with deuterium. 
     The term “(C 1 -C 20  alkyl) ‘X’ group” as used herein refers to an ‘X’ group that is 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  cycloalkyl group that is 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 phenyl group that is substituted with at least one C 1 -C 20  alkyl group. Examples of the term “(C 1  alkyl)phenyl group” include 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 hetero rings having the same backbones 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, a 9H-fluorene-9-one group, and a dibenzothiophene 5,5-dioxide group,” in which, in each group, at least one carbon selected from ring-forming carbons is substituted with nitrogen. 
     Substituents of the substituted C 5 -C 30  carbocyclic group, the substituted C 1 -C 30  heterocyclic group, the substituted C 1 -C 60  alkyl group, the substituted C 2 -C 60  alkenyl group, the substituted C 2 -C 60  alkynyl group, the substituted C 1 -C 60  alkoxy group, the substituted C 1 -C 60  alkylthio group, the substituted C 3 -C 10  cycloalkyl group, the substituted C 1 -C 10  heterocycloalkyl group, the substituted C 3 -C 10  cycloalkenyl group, the substituted C 1 -C 10 heterocycloalkenyl group, the substituted C 6 -C 60  aryl group, the substituted C 7 -C 60  alkyl aryl group, the substituted C 7 -C 0  aryl alkyl group, the substituted C 6 -C 60  aryloxy group, the substituted C 6 -C 60  arylthio group, the substituted C 1 -C 60  heteroaryl group, the substituted C 2 -C 60  alkyl heteroaryl group, the substituted C 2 -C 60  heteroaryl alkyl group, the substituted C 1 -C 60  heteroaryloxy group, the substituted C 1 -C 60  heteroarylthio group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group may each independently be: 
     deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, or a C 1 -C 60  alkylthio group, each substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Si(Q 13 )(Q 14 )(Q 15 ), —Ge(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), —P(═O)(Q 18 )(Q 19 ), —P(Q 18 )(Q 19 ), or a combination thereof; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 0  alkyl aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, or a monovalent non-aromatic condensed heteropolycyclic group, each unsubstituted or substituted with at least one of deuterium, —F, —Cl, —Br, —I, —SF 5 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 1 -C 60  alkylthio group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkyl aryl group, a C 7 -C 60  aryl alkyl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a C 2 -C 60  alkyl heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Si(Q 23 )(Q 24 )(Q 25 ), —Ge(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(═O)(Q 28 )(Q 29 ), —P(Q 28 )(Q 29 ), or a combination thereof; 
     —N(Q 31 )(Q 32 ), —Si(Q 33 )(Q 34 )(Q 35 ), —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 
     a combination thereof. 
     Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  as used herein 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 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 0  alkyl aryl group, a substituted or unsubstituted C 7 -C 0  aryl alkyl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 2 -C 60  alkyl heteroaryl group, a substituted or unsubstituted C 2 -C 60  heteroaryl alkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     Hereinafter, a compound and an organic light-emitting device according to one or more exemplary embodiments will be described in further detail with reference to Synthesis Examples and Examples, but embodiments are not limited thereto. The wording “B was used instead of A” used in describing Synthesis Examples means that an amount of B used was identical to an amount of A used based on molar equivalence. 
     EXAMPLES 
     Synthesis Example 1 (Compound 1) 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate L1-1 
     1.5 grams (g) (5.0 millimoles (mmol)) of 8-bromo-1-chlorobenzo[4,5]thieno[2,3-c]pyridine was mixed with 20 milliliters (mL) of anhydrous tetrahydrofuran (THF) and 40 mL of diethyl ether, and then 3.4 mL (5.5 mmol) of butyl lithium (BuLi, as a 1.6 Molar (M) solution in hexane) was slowly added thereto at −78° C. After about an hour, 0.8 mL (6.5 mmol) of chlorotrimethylgermane was slowly added dropwise thereto, followed by stirring at room temperature for 12 hours. After completion of the reaction, an organic layer was obtained by extraction with 40 mL of deionized (DI) water and ethyl acetate, the organic layer was separated and dried using anhydrous magnesium sulfate, the organic layer was isolated by filtration, and the solvent was removed from the product under a reduced pressure. The resultant product was further purified by liquid chromatography to obtain 1.4 g of Intermediate L1-1 (yield of 92%). 
     Liquid chromatography-mass spectrometry (LC-MS): m/z=337 (M+H) + . 
     Synthesis of Intermediate L1 
     1.51 g (4.5 mmol) of Intermediate L1-1 was dissolved in 60 mL of 1,4-dioxane and 15 mL of DI water, 1.7 g (5.4 mmol) of 2-(4-(tert-butyl)naphthalen-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.4 g (0.35 mmol) of tetrakis(triphenylphosphine)palladium(0) (Pd(PPh 3 ) 4 ), and 1.7 g (12.5 mmol) of K 2 CO 3  were added thereto, followed by heating at reflux while stirring for 24 hours. After completion of the reaction, the reaction contents were allowed to cool to room temperature, an organic layer was obtained by extraction with ethyl acetate and DI water, the organic layer was separated and dried using anhydrous magnesium sulfate, the product was filtered, and the solvents were removed under a reduced pressure. The resultant product was further purified by liquid chromatography to obtain 1.8 g of Intermediate L1 (yield of 83%). 
     LC-MS: m/z=485 (M+H) + . 
     Synthesis of Intermediate L1 Dimer 
     1.0 g (2.1 mmol) of Intermediate L1 and 0.34 g (1.0 mmol) of iridium chloride hydrate were mixed with 60 mL of ethoxyethanol and 15 mL of DI water, followed by heating at reflux while stirring for 24 hours. When the reaction was completed, the temperature was allowed to lower to room temperature, and a solid material formed therefrom was filtered and washed sufficiently with DI water, methanol, and hexane, in this stated order. The obtained solid was dried in a vacuum oven to obtain 1.1 g of Intermediate L1 Dimer. 
     Synthesis of Compound 1 
     1.0 g (0.42 mmol) of Intermediate L1 Dimer, 0.25 g (1.1 mmol) of 3,7-diethyl-3,7-dimethylnonane-4,6-dione, and 0.15 g (1.1 mmol) of K 2 CO 3  were mixed with 50 mL of ethoxyethanol, followed by stirring at room temperature for 24 hours to proceed a reaction. When the reaction was completed, a solid was produced by adding DI water, the solid was filtered, and the resulting product was further purified by liquid chromatography to obtain 0.8 g of Compound 1 (yield of 76%). 
     LC-MS: m/z=1399 (M+H) + . 
     Synthesis Example 2 (Compound 7) 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate L7-3 
     1.0 g (3.3 mmol) of 8-bromo-1-chlorobenzo[4,5]thieno[2,3-c]pyridine was dissolved in 40 mL of THF and 10 mL of DI water, and 0.4 g (3.9 mmol) of isobutyl boronic acid, 0.07 g (0.33 mmol) of palladium(II) acetate (Pd(OAc) 2 ), 0.27 g (0.66 mmol) of 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (S-phos), 1.2 g (8.3 mmol) of K 2 CO 3  were added thereto, followed by heating at refluxing while stirring for 24 hours. After completion of the reaction, an organic layer was obtained by extraction with ethyl acetate and DI water, the organic layer was dried using anhydrous magnesium sulfate, the product was filtered, and the solvent was removed under a reduced pressure. The resultant product was further purified by liquid chromatography to obtain 0.65 g of Intermediate L7-3 (yield of 71%). 
     LC-MS: m/z=277 (M+H) + . 
     Synthesis of Intermediate L7-2 
     2.5 g (7.4 mmol) of 1-bromo-3-iodonaphthalene was mixed with 60 mL of anhydrous THF, and then 4.8 mL (7.4 mmol) of BuLi (1.6 M solution in hexane) was slowly added thereto at −78° C. After about an hour, 1.8 mL (8.9 mmol) of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was slowly added dropwise thereto, and the reaction mixture was stirred at room temperature for 14 hours. After completion of the reaction, an organic layer was obtained by extraction with 50 mL of DI water and ethyl acetate, the organic layer was dried using anhydrous magnesium sulfate, the product was filtered, and the solvent was removed under a reduced pressure. The resultant product was further purified by liquid chromatography to obtain 2.2 g of Intermediate L7-2 (yield of 90%). 
     LC-MS: m/z=334 (M+H) + . 
     Synthesis of Intermediate L7-1 
     0.6 g (2.2 mmol) of Intermediate L7-3 was dissolved in 40 mL of THF and 15 mL of DI water, and 0.9 g (2.6 mmol) of 2-(4-bromonaphthalen-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (Intermediate L7-2), 0.18 g (0.15 mmol) of Pd(PPh 3 ) 4 , and 0.35 g (5.5 mmol) of K 2 CO 3  were added thereto, followed by heating at reflux while stirring for 24 hours. After completion of the reaction, an organic layer was obtained by extraction with ethyl acetate and DI water, the organic layer was dried using anhydrous magnesium sulfate, the product was filtered, and the solvent was removed under a reduced pressure. 
     The resultant product was further purified by liquid chromatography to obtain 0.8 g of Intermediate L1 (yield of 84%). 
     LC-MS: m/z=447 (M+H) + . 
     Synthesis of Intermediate L7 
     0.8 g (1.8 mmol) of Intermediate L7-1 was mixed with 40 mL of anhydrous THF, and 1.2 ml (2.0 mmol) of BuLi (1.6 M solution in hexane) was slowly added thereto at −78° C. After about an hour, 0.3 mL (2.7 mmol) of chlorotrimethylgermane was slowly added dropwise thereto, followed by stirring at room temperature for 16 hours. After completion of the reaction, an organic layer was obtained by extraction with 20 mL of DI water and ethyl acetate, the organic layer was dried using anhydrous magnesium sulfate, the product was filtered, and the solvent was removed under a reduced pressure. The resultant product was further purified by liquid chromatography to obtain 0.5 g of Intermediate L7 (yield of 54%). 
     LC-MS: m/z=485 (M+H) + . 
     Synthesis of Intermediate L7 Dimer 
     Intermediate L7 Dimer was obtained in a similar manner as used to obtain Intermediate L1 Dimer of Synthesis Example 1, except that Intermediate L7 was used instead of Intermediate L1. 
     Synthesis of Compound 7 
     0.25 g of Compound 7 (yield of 42%) was obtained in a similar manner as used to obtain Compound 1 of Synthesis Example 1, except that Intermediate L7 Dimer was used instead of Intermediate L1 Dimer. 
     LC-MS: m/z=1399 (M+H) + . 
     Synthesis Example 3 (Compound 14) 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate L14-1 
     1-chloro-7-fluorobenzo[4,5]thieno[2,3-c]pyridine (1.81 g, 7.62 mmol) was dissolved in 30 mL of THF, followed by stirring at −78° C. n-BuLi (1.6 M solution in hexane) (5.23 ml, 8.38 mmol) was added dropwise thereto for 30 minutes, followed by stirring at −78° C. for an hour. Trimethylgermyl chloride (1.13 ml, 9.14 mmol) was added dropwise thereto for 30 minutes, and then the temperature was slowly raised to room temperature. An organic layer was extracted using ethyl acetate, anhydrous magnesium sulfate was added thereto to remove moisture, the product was filtered, and the solvent was removed under a reduced pressure. The product was further purified by column chromatography using ethyl acetate and hexane as eluents (1:5, v/v) to obtain 1.20 g of Intermediate L14-1 (yield of 44%). 
     LC-MS: m/z=355 (M+H) + . 
     Synthesis of Intermediate L14 
     1-chloro-7-fluoro-6-(trimethylgermyl)benzo[4,5]thieno[2,3-c]pyridine (Intermediate L14-1) (0.92 g, 2.59 mmol), 2-(4-(tert-butyl)naphthalen-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.84 g, 2.72 mmol), Pd(PPh 3 ) 4  (0.15 g, 0.13 mmol), and K 2 CO 3  (0.72 g, 5.18 mmol) were mixed with 20 mL of THF and 5 mL of DI water, followed by stirring while heating at reflux for 18 hours. After the temperature was allowed to lower to room temperature, an organic layer was extracted using methylene chloride, anhydrous magnesium sulfate (MgSO 4 ) was added thereto to remove moisture, and a residue was obtained by removing the solvent under a reduced pressure. The product was further purified by column chromatography using ethyl acetate and hexane as eluents (1:5, v/v) to obtain 1.20 g of Intermediate L14 (yield of 92%). 
     LC-MS: m/z=503 (M+H) + . 
     Synthesis of Intermediate L14 Dimer 
     Intermediate L14 (1.24 g, 2.47 mmol) and iridium chloride hydrate (0.43 g, 1.22 mmol) were mixed with 20 mL of 2-ethoxyethanol and 5 mL of DI water, followed by stirring while heating at reflux for 24 hours to proceed a reaction, and then the temperature was allowed to lower to room temperature. A solid thus produced therefrom was separated by filtration, washed sufficiently with DI water, methanol, and hexane in this stated order, and then dried in a vacuum oven to obtain Intermediate L14 Dimer (1.0 g, yield of 67%). 
     Synthesis of Compound 14 
     Intermediate L14 Dimer (1.0 g, 0.42 mmol), 3,7-diethyl-3,7-dimethylnonane-4,6-dione (0.24 g, 1.0 mmol), and K 2 CO 3  (0.14 g, 0.1 mmol) were mixed with 20 mL of 2-ethoxyethanol, followed by stirring for 24 hours to proceed a reaction. A solid was obtained by filtering the mixture and washed with methanol and hexane. The product was purified by column chromatography using dichloromethane and n-hexane as eluents (1:1, v/v) to obtain Compound 14 (1.0 g, yield of 83%). Compound 14 was identified by LC-MS. 
     LC-MS: m/z=1435 (M+H) + . 
     Synthesis Example 4 (Compound 15) 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate L15 
     1-chloro-7-fluoro-8-(trimethylgermyl)benzo[4,5]thieno[2,3-c]pyridine (Intermediate L15-1) (0.92 g, 2.59 mmol), 2-(4-(tert-butyl)naphthalen-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.84 g, 2.72 mmol), Pd(PPh 3 ) 4  (0.15 g, 0.13 mmol), and K 2 CO 3  (0.72 g, 5.18 mmol) were mixed with 20 mL of THF and 5 mL of DI water, followed by stirring while heating at reflux for 18 hours. After the temperature was allowed to lower to room temperature, an organic layer was extracted using methylene chloride, anhydrous magnesium sulfate (MgSO 4 ) was added thereto to remove moisture, the product was filtered, and a residue was obtained by removing the solvent under a reduced pressure. The product was further purified by column chromatography using ethyl acetate and hexane as eluents (1:5, v/v) to obtain 1.20 g of Compound L15 (yield of 92%). 
     LC-MS: m/z=503 (M+H) + . 
     Synthesis of Intermediate L15 Dimer 
     Intermediate L15 (1.24 g, 2.47 mmol) and iridium chloride hydrate (0.43 g, 1.22 mmol) were mixed with 20 mL of 2-ethoxyethanol and 5 mL of DI water, followed by stirring while heating at reflux for 24 hours to proceed a reaction, and then the temperature was allowed to lower to room temperature. A solid thus produced therefrom was separated by filtration, washed sufficiently with DI water, methanol, and hexane in this stated order, and then dried in a vacuum oven to obtain Intermediate L15 Dimer (1.0 g, yield of 67%). 
     Synthesis of Compound 15 
     Intermediate L15 Dimer (1.0 g, 0.42 mmol), 3,7-diethyl-3,7-dimethylnonane-4,6-dione (0.24 g, 1.0 mmol), and K 2 CO 3  (0.14 g, 0.1 mmol) were mixed with 20 mL of 2-ethoxyethanol, followed by stirring for 24 hours to proceed a reaction. A solid was obtained by filtering the mixture and washed with methanol and hexane. The product was further purified by column chromatography using dichloromethane and n-hexane (1:1, v/v) to obtain Compound 15 (1.0 g, yield of 83%). Compound 15 was identified by LC-MS. 
     LC-MS: m/z=1435 (M+H) + . 
     Synthesis Example 5 (Compound 22) 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate L22 
     Intermediate L22 was obtained in a similar manner as was used to obtain Intermediate L1 of Synthesis Example 1, except that 6-bromo-1-chlorobenzo[4,5]thieno[2,3-c]pyridine was used instead of Intermediate 8-bromo-1-chlorobenzo[4,5]thieno[2,3-c]pyridine. 
     LC-MS: m/z=485 (M+H) + . 
     Synthesis of Intermediate L22 Dimer 
     Intermediate L22 Dimer was obtained in a similar manner as was used to obtain Intermediate L1 Dimer of Synthesis Example 1, except that Intermediate L22 was used instead of Intermediate L1. 
     Synthesis of Compound 22 
     0.61 g of Compound 22 (yield of 51%) was obtained in a similar manner as was used to obtain Compound 1 of Synthesis Example 1, except that Intermediate L22 Dimer was used instead of Intermediate L1 Dimer. 
     LC-MS: m/z=1399 (M+H) + . 
     Evaluation Example 1: Evaluation of Photoluminescence Quantum Yields (PLQY) 
     Compound H52 and Compound 1 were co-deposited under vacuum (10-7 torr) at a weight ratio of 98:2 to produce a film having a thickness of 40 nm. 
     The PLQY in film was evaluated using a Hamamatsu Photonics absolute PL quantum yield measurement system equipped with a xenon light source, a monochromator, a photonic multichannel analyzer, and an integrating sphere and employing PLQY measurement software (Hamamatsu Photonics, Ltd., Shizuoka, Japan) to identify the PLQY in film of Compound 1. The results are shown in Table 2. 
     The PLQY measurement was performed on each of Compounds 7, 14, 15, 22, A, B1, and B2, and the results are shown in Table 2. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Compound No. 
                 PLQY in film (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1 
                 91 
               
               
                   
                 7 
                 92 
               
               
                   
                 14 
                 92 
               
               
                   
                 15 
                 92 
               
               
                   
                 22 
                 91 
               
               
                   
                 A 
                 88 
               
               
                   
                 B1 
                 83 
               
               
                   
                 B2 
                 90 
               
               
                   
                   
               
               
                   
                 
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                 
               
            
           
         
       
     
     From Table 2, it was determined that Compounds 1, 7, 14, 15, and 22 had superior PLQY characteristics compared to those of Compounds A, B1, and B2. 
     Evaluation Example 2: Evaluation of Horizontal Orientation Ratio (Optical Orientation Ratio) 
     In a vacuum deposition apparatus having a vacuum degree of 1×10 −7  torr, Compound H52 and Compound 1 were co-deposited at a weight ratio of 98:2 on a fused silica layer (having a thickness of 1 mm) to form a film having a thickness of 40 nm, and then sealed with glass and glue under a nitrogen atmosphere. 
     Meanwhile, an angle-dependent PL measurement apparatus having the same structure as that shown in FIG. 3 of Korean Patent Application Publication No. 2013-0150834 was prepared. Detailed specifications are as follows: 
     Excitation light wavelength: 325 nm 
     Source of excitation light: He—Cd laser of Melles Griot Inc. 
     Excitation light irradiation member: Optical fiber having a diameter of 1 mm of Thorlabs Inc. 
     Semi-cylindrical prism: Fused silica having a diameter of 100 mm and a length of 30 mm 
     Emitted light detection member: Photomultiplier tube of Acton Inc. 
     Polarizer mounted on emitted light detection member: Linear polarizer of Thorlabs Inc. 
     Recorder: SpectraSense of Acton Inc. 
     Incidence angle of excitation light: θP=45°, θH=0 0    
     Distance from a sample to the emitted light detection member (or a radius of a movement path of the emitted light detection member): 900 mm 
     Subsequently, the film was fixed on a semi-cylindrical lens and 325 nm laser was irradiated thereto to emit a light. The emitted light passed through a polarization film, and then, to measure a p-polarized photoluminescence intensity with respect to light at a Max wavelength of a spectrum in a range of 90 degrees to 0 degree, the semi-cylindrical lens, on which the sample was fixed, was rotated by 1 degree with respect to an axis of the semi-cylindrical lens by using a charge-coupled device (CCD). 
     The p-polarized photoluminescence intensity (a first p-polarized photoluminescence intensity) in a case where each compound was vertically aligned and the p-polarized photoluminescence intensity (a second p-polarized photoluminescence intensity) in a case where each compound was horizontally aligned were each calculated within a range of 0 degree to 90 degrees. The p-polarized photoluminescence intensity obtained by multiplying the first p-polarized photoluminescence intensity and the second p-polarized photoluminescence intensity respectively by a weight value were obtained to obtain a weight value corresponding to the measured p-polarized photoluminescence intensity. Then, the horizontal orientation ratio of each compound shown in Table 3 was measured and the results are shown in Table 3. The angle-dependent photoluminescence spectra were analyzed using a classical dipole model that regards light emitted from excitons as dissipated power from an oscillating dipole, and the horizontal orientation ratio for Compound 1 was evaluated. 
     This was performed on each of Compounds 7, 14, 15, 22, A, B1, and B2, and the results are shown in Table 3. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Horizontal orientation ratio 
               
               
                   
                   
                 (optical orientation ratio) 
               
               
                   
                 Co-deposition material 
                 (%) 
               
               
                   
                   
               
             
            
               
                   
                 H52 : Compound 1 (2 wt %) 
                 92 
               
               
                   
                 H52 : Compound 7 (2 wt %) 
                 92 
               
               
                   
                 H52 : Compound 14 (2 wt %) 
                 94 
               
               
                   
                 H52 : Compound 15 (2 wt %) 
                 93 
               
               
                   
                 H52 : Compound 22 (2 wt %) 
                 94 
               
               
                   
                 H52 : Compound A (2 wt %) 
                 89 
               
               
                   
                 H52 : Compound B1 (2 wt %) 
                 80 
               
               
                   
                 H52 : Compound B2 (2 wt %) 
                 91 
               
               
                   
                   
               
            
           
         
       
     
     From Table 3, it was determined that Compounds 1, 7, 14, 15, and 22 had superior horizontal orientation ratio characteristics compared to those of Compounds A, B1, and B2. 
     Example 1 
     A glass substrate on which an ITO as an anode was patterned was cut to a size of 50 millimeters (mm)×50 mm×0.5 mm, sonicated with isopropyl alcohol and DI water each for 5 minutes, and then cleaned by irradiation of ultraviolet rays and exposure of ozone thereto for 30 minutes each. The resultant glass substrate was loaded onto a vacuum deposition apparatus. 
     HT3 and F6-TCNNQ were vacuum-co-deposited on the ITO anode at a weight ratio of 98:2 to form a hole injection layer having a thickness of 100 Å, HT3 was vacuum-deposited on the hole injection layer to form a hole transport layer having a thickness of 1,350 Å, and then, HT21 was vacuum-deposited on the hole transport layer to form an electron blocking layer having a thickness of 300 Å. 
     Subsequently, H52 (host) and Compound 1 (dopant) were co-deposited at a weight ratio of 98:2 on the electron blocking layer to form an emission layer having a thickness of 400 Å. 
     Afterwards, ET3 and ET-D1 were co-deposited at a volume ratio of 50:50 on the emission layer to form an electron transport layer having a thickness of 350 Å, ET-D1 was vacuum-deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and A1 was vacuum-deposited on the electron injection layer to form a cathode having a thickness of 1,000 Å, thereby completing the manufacture of an organic light-emitting device having a structure of ITO (1,500 Å)/HT3+F6-TCNNQ (2 wt %) (100 Å)/HT3 (1,350 Å)/HT21 (300 Å)/H52+Compound 1 (2 wt %) (400 Å)/ET3+ET-D1 (50%) (350 Å)/ET-D1 (10 Å)/A1 (1,000 Å). 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Examples 2 to 5 and Comparative Examples A, B1, and B2 
     Organic light-emitting devices were manufactured in a similar manner as was used in Example 1, except that compounds shown in Table 4 were each used instead of Compound 1 as a dopant in forming the emission layer. 
     Evaluation Example 3: Evaluation of Device Characteristics 
     The driving voltage (V), current density (mA/cm 2 ), maximum value of external quantum efficiency (Max EQE, relative %), FWHM (nm) of an emission peak of an EL spectrum, maximum emission wavelength (nm), and lifespan (LT 97 , relative %) of the organic light-emitting devices manufactured according to Examples 1 to 5 and Comparative Examples A, B1, and B2 were evaluated. The results are shown in Table 4. As an evaluation device, a current-voltmeter (Keithley 2400) and a luminance meter (Minolta Cs-1000A) were used, and the lifespan (LT 97 ) (at 3,500 candela per square meter (cd/m 2 ) was evaluated as the time (hours, hr) taken for luminance to reach 97% relative to 100% of the initial luminance. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Compound  
                   
                   
                   
                   
                 Maximum 
                   
               
               
                   
                 No. as 
                 Driving 
                 Current 
                 Max  
                   
                 emission 
                   
               
               
                   
                 a dopant in 
                 voltage 
                 density 
                 EQE 
                 FWHM 
                 wavelength 
                 LT 97   
               
               
                   
                 emission layer 
                 (V) 
                 (mA/cm 2 ) 
                 (relative %) 
                 (nm) 
                 (nm) 
                 (relative %) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 1 
                 4.1 
                 10 
                 28 
                 34 
                 626 
                 115 
               
               
                 Example 2 
                 7 
                 4.2 
                 10 
                 27 
                 35 
                 622 
                 120 
               
               
                 Example 3 
                 14 
                 4.0 
                 10 
                 30 
                 34 
                 625 
                 150 
               
               
                 Example 4 
                 15 
                 4.0 
                 10 
                 29 
                 34 
                 624 
                 170 
               
               
                 Example 5 
                 22 
                 4.3 
                 10 
                 29 
                 33 
                 623 
                 150 
               
               
                 Comparative 
                 A 
                 4.3 
                 10 
                 25 
                 35 
                 626 
                 100 
               
               
                 Example A 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 B1 
                 4.5 
                 10 
                 21 
                 71 
                 535 
                 150 
               
               
                 Example B1 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 B2 
                 4.3 
                 10 
                 26 
                 51 
                 626 
                 110 
               
               
                 Example B2 
                   
                   
                   
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                 
               
            
           
         
       
     
     From Table 4, it was determined that the organic light-emitting devices of Examples 1 to 5 had improved driving voltages, improved external quantum efficiencies, and improved lifespan characteristics compared to those of the organic light-emitting devices of Comparative Examples A, B1, and B2, and at the same time, emitted a light having a relatively small or narrow FWHM. 
     The organometallic compound has excellent thermal stability and electrical characteristics. Accordingly, an electronic device, for example, a light-emitting device, including at least one of the organometallic compounds may have improved driving voltage, improved external quantum efficiency, and improved lifespan characteristics, and may emit a light having a relatively small or narrow FWHM. 
     It should be understood that exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more exemplary embodiments have been described with reference to the FIGURE, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.