Patent Publication Number: US-2023159570-A1

Title: Light-emitting device including heterocyclic compound, electronic apparatus including the light-emitting device, and the heterocyclic compound

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0153304, filed on Nov. 9, 2021, in the Korean Intellectual Property Office, the entire content of which is hereby incorporated by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments of the present disclosure relate to a light-emitting device including a heterocyclic compound, an electronic apparatus including the light-emitting device, and the heterocyclic compound. 
     2. Description of the Related Art 
     From among light-emitting devices, organic light-emitting devices are self-emissive devices that, as compared with other devices of the related art, have wide viewing angles, high contrast ratios, short response times, and excellent characteristics in terms of luminance, driving voltage, and response speed. 
     Organic light-emitting devices may include a first electrode on a substrate, and a hole transport region, an emission layer, an electron transport region, and a second electrode sequentially stacked on the first electrode. Holes provided from the first electrode move toward the emission layer through the hole transport region, and electrons provided from the second electrode move toward the emission layer through the electron transport region. Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. The excitons may transition from an excited state to a ground state, thereby generating light. 
     SUMMARY 
     One or more embodiments include a light-emitting device including a heterocyclic compound, an electronic apparatus including the light-emitting device, and the heterocyclic compound. 
     Additional aspects of embodiments will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure. 
     According to one or more embodiments, provided is a light-emitting device including: 
     a first electrode, 
     a second electrode facing the first electrode, 
     an interlayer between the first electrode and the second electrode and including an emission layer, and 
     a heterocyclic compound represented by Formula 1. 
     
       
         
         
             
             
         
       
     
     In Formula 1, 
     L 1  and L 2  may each independently be a single bond, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     n1 and n2 may each independently be an integer from 1 to 3, 
     Ar 1  and Ar 2  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     Ar 3  to A r5  and R 1  to R 3  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), 
     a1 and a2 may each independently be an integer from 0 to 4, 
     a3 may be an integer from 0 to 2, 
     R 10a  may be: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group, 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof, 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, or a C 6 -C 60  arylthio group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro 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, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 )(Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof, or —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —P(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ), and 
     Q 1  to Q 3 , Q 11  to Q 13 , Q 21  to Q 23 , and Q 31  to Q 33  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 10  alkyl group, a phenyl group, a biphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, or any combination thereof, or a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a biphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, or any combination thereof; a C 7 -C 60  arylalkyl group; or a C 2 -C 60  heteroarylalkyl group. 
     According to one or more embodiments, provided is an electronic apparatus including the light-emitting device. 
     According to one or more embodiments, provided is the heterocyclic compound represented by Formula 1. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and features of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a schematic view of a light-emitting device according to an embodiment; 
         FIG.  2    is a schematic view of an electronic apparatus according to an embodiment; and 
         FIG.  3    is a schematic view of an electronic apparatus according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in more detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of embodiments of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Throughout the disclosure, 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. 
     A light-emitting device according to an embodiment of the present disclosure may include: a first electrode; a second electrode facing the first electrode; an interlayer between the first electrode and the second electrode and including an emission layer; and a heterocyclic compound represented by Formula 1: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 1, L 1  and L 2  may each independently be a single bond, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , wherein R 10a  is the same as described in the present specification. 
     For example, L 1  and L 2  may each independently be: a single bond; or 
     a benzene group, a naphthalene group, an anthracene group, a phenanthrene group, a triphenylene group, a pyrene group, a chrysene group, a cyclopentadiene group, a 1,2,3,4-tetrahydronaphthalene group, a thiophene group, a furan group, an indole group, a benzoborole group, a benzophosphole group, an indene group, a benzosilole group, a benzogermole group, a benzothiophene group, a benzoselenophene group, a benzofuran group, a carbazole group, a dibenzoborole group, a dibenzophosphole group, a fluorene group, a dibenzosilole group, a dibenzogermole group, a dibenzothiophene group, a dibenzoselenophene group, a dibenzofuran group, a dibenzothiophene 5-oxide group, a 9H-fluorene-9-one group, a dibenzothiophene 5,5-dioxide group, an azaindole group, an azabenzoborole group, an azabenzophosphole group, an azaindene group, an azabenzosilole group, an azabenzogermole group, an azabenzothiophene group, an azabenzoselenophene group, an azabenzofuran group, an azacarbazole group, an azadibenzoborole group, an azadibenzophosphole group, an azafluorene group, an azadibenzosilole group, an azadibenzogermole group, an azadibenzothiophene group, an azadibenzoselenophene group, an azadibenzofuran group, an azadibenzothiophene 5-oxide group, an aza-9H-fluoren-9-one group, an azadibenzothiophene 5,5-dioxide group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a pyrrole group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an 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, or a 5,6,7,8-tetrahydroquinoline group, each unsubstituted or substituted with at least one R 10a . 
     In an embodiment, L 1  and L 2  may each independently be a single bond or a phenylene group. 
     In an embodiment, L 1  and L 2  may each be a single bond. 
     n1 and n2 in Formula 1 may each independently be an integer from 1 to 3. 
     Ar 1  and Ar 2  in Formula 1 may each independently be a single bond, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , wherein R 10a  is the same as described in the present specification. 
     In an embodiment, Ar 1  and Ar 2  may each independently be a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , or a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a . 
     For example, Ar 1  and Ar 2  may each independently be a phenyl group, a biphenyl 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, an azafluorenyl group, or an azadibenzosilolyl group, each unsubstituted or substituted with at least one R 10a . 
     In an embodiment, An and Ar 2  may each independently be a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, or any combination thereof. 
     In one or more embodiments, Ar 1  and Ar 2  may each be a phenyl group unsubstituted or substituted with deuterium. 
     Ar 3  to Ar 5  in Formula 1 may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , —Si(a)(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), wherein R 10a  and Q 1  to Q 3  are the same as described in the present specification. 
     For example, Ar 3  to Ar 5  may each independently be: hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, or a C 1 -C 20  alkoxy group; 
     a C 1 -C 20  alkyl group or a C 1 -C 20  alkoxy group, each substituted with deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, 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 phenyl group, a biphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof; 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a biphenyl group, a C 1 -C 10  alkylphenyl 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, an azafluorenyl group, or an azadibenzosilolyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a biphenyl group, a C 1 -C 10  alkylphenyl 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, an azafluorenyl group, an azadibenzosilolyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —P(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), —P(═O)(Q 31 )(Q 32 ), or any combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), and 
     Q 1  to Q 3  and Q 31  to Q 33  may each independently be: —CH 3 , -CD 3 , -CD 2 H, -CDH 2 , —CH 2 CH 3 , —CH 2 CD 3 , —CH 2 CD 2 H, —CH 2 CDH 2 , —CHDCH 3 , —CHDCD 2 H, —CHDCDH 2 , —CHDCD 3 , -CD 2 CD 3 , -CD 2 CD 2 H, or -CD 2 CDH 2 ; or 
     an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, or a triazinyl group, each unsubstituted or substituted with at least one of deuterium, a C 1 -C 10  alkyl group, a phenyl group, a biphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, and a triazinyl group. 
     In an embodiment, Ar 3  to Ar 5  may each independently be a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , or a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a . 
     In an embodiment, Ar 3  to Ar 5  may each independently be a phenyl group, a biphenyl 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, an azafluorenyl group, or an azadibenzosilolyl group, each unsubstituted or substituted with at least one R 10a . 
     In an embodiment, Ar 3  to Ar 5  may each independently a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, a naphthyl group, or any combination thereof. 
     In an embodiment, the heterocyclic compound may be represented by Formula 1-1 or 1-2: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 1-1 and 1-2, 
     L 1 , L 2 , n1, n2, Ar 1  to Ar 5 , R 1  to R 3 , and a1 to a3 are the same as described in the present specification with respect to Formula 1. 
     In an embodiment, moieties represented by 
     
       
         
         
             
             
         
       
     
     in Formula 1 may each independently be one of groups represented by Formulae 1A-1 to 1A-13: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 1A-1 to 1A-13, 
     R 11  to R 14  may each independently be deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), 
     *, *′, and *″ each indicate a binding site to a neighboring atom, and 
     R 10a  and Q 1  to Q 3  are the same as described in the present specification with respect to Formula 1. 
     R 1  to R 3  in Formulae 1, 1-1, and 1-2 may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), wherein R 10a  and Q 1  to Q 3  are the same as described in the present specification. 
     For example, R 1  to R 3  may each independently be: hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, or a C 1 -C 20  alkoxy group; 
     a C 1 -C 20  alkyl group or a C 1 -C 20  alkoxy group, each substituted with deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, 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 phenyl group, a biphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof; 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a biphenyl group, a C 1 -C 10  alkylphenyl 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, an azafluorenyl group, or an azadibenzosilolyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a biphenyl group, a C 1 -C 10  alkylphenyl 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, an azafluorenyl group, an azadibenzosilolyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —P(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), —P(═O)(Q 31 )(Q 32 ), or any combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), and 
     Q 1  to Q 3  and Q 31  to Q 33  may each independently be: —CH 3 , -CD 3 , -CD 2 H, -CDH 2 , —CH 2 CH 3 , —CH 2 CD 3 , —CH 2 CD 2 H, —CH 2 CDH 2 , —CHDCH 3 , —CHDCD 2 H, —CHDCDH 2 , —CHDCD 3 , -CD 2 CD 3 , -CD 2 CD 2 H, or -CD 2 CDH 2 ; or 
     an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, or a triazinyl group, each unsubstituted or substituted with at least one of deuterium, a C 1 -C 1  alkyl group, a phenyl group, a biphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, and a triazinyl group. 
     In an embodiment, R 1  and R 2  may each independently be: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, or a C 1 -C 1  alkyl group; 
     a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, a C 1 -C 1  alkyl group, a phenyl group, a biphenyl group, a naphthyl group, or any combination thereof; or 
     one of groups represented by Formulae 2-1 to 2-3: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 2-1 to 2-3, 
     L 21  and L 22  may each independently be a single bond, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     n21 and n22 may each independently be an integer from 1 to 3, 
     X 1  may be O, S, N(R 1a ), C(R 1a )(R 1b ), or Si(R 1a )(R 1b ), 
     Y 1  may be C or Si, 
     Ar 21  to Ar 23  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     Z 1  to Z 4 , R 1a , and R 1b  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O) 2 (Q 1 ), or —P(═O)(Q 1 )(Q 2 ), 
     b1, b2, and b4 may each independently be an integer from 0 to 4, 
     b3 may be an integer from 0 to 3, 
     * indicates a binding site to a neighboring atom, and 
     R 10a  and Q 1  to Q 3  are the same as described in the present specification with respect to Formula 1. 
     In one or more embodiments, L 21  and L 22  may each independently be: a single bond; or a phenyl group unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, or any combination thereof. 
     In one or more embodiments, X 1  may be O, S, N(Ria), or Si(Ria)(Rib). 
     In one or more embodiments, Ria and Rib may each independently be a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, or any combination thereof. 
     In one or more embodiments, Z 1  to Z 4  may each independently be: hydrogen, deuterium, —F, —Cl, —Br, —I, —CDs, -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, or a C 1 -C 10  alkyl group; 
     a phenyl group, a biphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a carbazole group, a dibenzofuranyl group, a dibenzothiophenyl group, or a dibenzosilolyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, —CDs, -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, a C 1 -C 10  alkyl group, a phenyl group, a biphenyl group, a naphthyl group, or any combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ). 
     In one or more embodiments, Z 1  to Z 4  may each independently be one of groups represented by Formulae 2A-1 to 2A-4 and 2B-1 to 2B-8. 
     In an embodiment, a group represented by Formula 2-1 may be one of groups represented by Formulae 2A-1 to 2A-4, and 
     a group represented by Formula 2-2 may be one of groups represented by Formulae 2B-1 to 2B-8: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae 2A-1 to 2A-4 and 2B-1 to 2B-8, 
     X 2  may be O, S, C(R 1a )(R 1b ), or Si(R 1a )(R 1b ), 
     Z 11  to Z 15 , R 1a , and R 1b  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), or —N(Q 1 )(Q 2 ), 
     Z 16  may be a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , or a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , 
     b11, b12, b14, and b15 may each independently be an integer from 0 to 4, 
     b13 may be an integer from 0 to 3, 
     * indicates a binding site to a neighboring atom, and 
     R 10a  and Q 1  to Q 3  are the same as described in the present specification with respect to Formula 1. 
     In one or more embodiments, Z 11  to Z 14  may each independently be: hydrogen, deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, or a C 1 -C 1  alkyl group; 
     a phenyl group, a biphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a carbazole group, a dibenzofuranyl group, a dibenzothiophenyl group, or a dibenzosilolyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, -CD 3 , -CD 2 H, -CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, a C 1 -C 1  alkyl group, a phenyl group, a biphenyl group, a naphthyl group, or any combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ). 
     In one or more embodiments, Z 1  to Z 4  may each independently be one of groups represented by Formulae 2A-1 to 2A-4 and 2B-1 to 2B-8. 
     In one or more embodiments, Z 16  may be a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 1  alkyl group, a phenyl group, or any combination thereof. 
     In an embodiment, Ar 21  to Ar 23  in Formula 2-3 may each independently be a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , or a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a . 
     In one or more embodiments, Ar 1  to Ar 3  in Formula 2-3 may each independently be a phenyl group, a biphenyl group, or a naphthyl group, each unsubstituted or substituted with deuterium, a C 1 -C 10  alkyl group, a phenyl group, or any combination thereof. 
     a1 and a2 in Formula 1 may each independently be an integer from 0 to 4. 
     a3 in Formula 1 may be an integer from 0 to 2. 
     In an embodiment, the heterocyclic compound may be one of Compounds 1 to 273, 280 to 322, and 329 to 336: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The heterocyclic compound represented by Formula 1 may include a phenylene group that has a substituent at an ortho position by bonding to nitrogen (N) of carbazole, and silicon (Si) as a linking group in the compound. 
     Because the heterocyclic compound has a structure having large steric hindrance, such as the phenylene group that has a substituent at the ortho position, interaction with a dopant may be reduced. Also, because the heterocyclic compound introduces Si as a linking group, a conjugation length may be reduced, and thus, relatively high triplet energy may be obtained for the heterocyclic compound, thereby improving luminescence efficiency of an organic light-emitting device including the heterocyclic compound. In addition, because the heterocyclic compound has a large molecular weight, high thermal stability may be obtained for the heterocyclic compound. 
     Accordingly, by using the heterocyclic compound represented by Formula 1, diffusion of triplet excitons generated in an emission layer into a hole transport region may be suppressed or reduced, and thus, a driving voltage and luminescence efficiency of a light-emitting device (for example, an organic light-emitting device) including the heterocyclic compound may be improved. 
     Synthesis methods of the heterocyclic compound represented by Formula 1 may be recognizable by one of ordinary skill in the art by referring to Synthesis Examples and/or Examples provided herein below. 
     At least one heterocyclic compound represented by Formula 1 may be used in a light-emitting device (for example, an organic light-emitting device). Accordingly, provided is a light-emitting device including: a first electrode; a second electrode facing the first electrode; an interlayer between the first electrode and the second electrode and including an emission layer; and a heterocyclic compound represented by Formula 1 as described herein. 
     In an embodiment, 
     the first electrode of the light-emitting device may be an anode, 
     the second electrode of the light-emitting device may be a cathode, 
     the interlayer may further include a hole transport region between the first electrode and the emission layer and an electron transport region between the emission layer and the second electrode, 
     the hole transport region may include a hole injection layer, a hole transport layer, an emission auxiliary layer, an electron blocking layer, or any combination thereof, and 
     the electron transport region may include a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     In one or more embodiments, the heterocyclic compound may be included between the first electrode and the second electrode of the light-emitting device. Accordingly, the heterocyclic compound may be included in the interlayer of the light-emitting device, for example, in the emission layer of the interlayer. 
     In one or more embodiments, the emission layer in the interlayer of the light-emitting device may include a dopant and a host, and the heterocyclic compound may be included in the host. For example, the heterocyclic compound may serve as a host. The emission layer may emit red light, green light, blue light, and/or white light. For example, the emission layer may emit blue light. The blue light may have a maximum emission wavelength in a range of about 400 nm to about 490 nm, about 410 nm to about 490 nm, about 420 nm to about 480 nm, or about 430 nm to about 480 nm. 
     In one or more embodiments, the emission layer in the interlayer of the light-emitting device may include a dopant and a host, the heterocyclic compound may be included in the host, and the dopant may emit blue light. For example, the dopant may include a transition metal and ligand(s) in the number of m, m may be an integer from 1 to 6, the ligand(s) in the number of m may be identical to or different from each other, at least one of the ligand(s) in the number of m may be bound to the transition metal via a carbon-transition metal bond, and the carbon-transition metal bond may be a coordinate bond. For example, at least one of the ligand(s) in the number of m may be a carbene ligand (for example, Ir(pmp) 3  or the like). The transition metal may be, for example, iridium, platinum, osmium, palladium, rhodium, or gold. More details on the emission layer and the dopant are the same as described in the present specification. 
     
       
         
         
             
             
         
       
     
     In one or more embodiments, the light-emitting device may include a capping layer outside the first electrode or outside the second electrode. 
     In an embodiment, the light-emitting device may further include at least one of a first capping layer outside the first electrode and/or a second capping layer outside the second electrode, and at least one of the first capping layer and the second capping layer may include the heterocyclic compound represented by Formula 1. More details on the first capping layer and/or the second capping layer are the same as described in the present specification. 
     In an embodiment, the light-emitting device may include: 
     a first capping layer outside the first electrode and including the heterocyclic compound represented by Formula 1; 
     a second capping layer outside the second electrode and including the heterocyclic compound represented by Formula 1; or 
     the first capping layer and the second capping layer. 
     The expression “(an interlayer and/or a capping layer) includes at least one heterocyclic compound,” as used herein, may include a case in which “(an interlayer and/or a capping layer) includes identical heterocyclic compounds represented by Formula 1” and a case in which “(an interlayer and/or a capping layer) includes two or more different heterocyclic compounds represented by Formula 1.” 
     For example, the interlayer and/or capping layer may include Compound 1 only as the heterocyclic compound. In this regard, Compound 1 may be present in the emission layer of the light-emitting device. In one or more embodiments, the interlayer may include, as the heterocyclic compound, Compound 1 and Compound 2. In this regard, Compound 1 and Compound 2 may be present in the same layer (for example, both Compound 1 and Compound 2 may be present in an emission layer), or may be present in different layers (for example, Compound 1 may be present in an emission layer, and Compound 2 may be present in an electron transport region). 
     The term “interlayer,” as used herein, refers to a single layer and/or all of a plurality of layers between the first electrode and the second electrode of the light-emitting device. 
     Another aspect of embodiments of the present disclosure provides an electronic apparatus including the light-emitting device. The electronic apparatus may further include a thin-film transistor. For example, the electronic apparatus may further include a thin-film transistor including a source electrode and a drain electrode, and the first electrode of the light-emitting device may be electrically connected to the source electrode or the drain electrode. The electronic apparatus may further include a color filter, a color-conversion layer, a touch screen layer, a polarizing layer, or any combination thereof. More details on the electronic apparatus are the same as described in the present specification. 
     Description of  FIG.  1     
       FIG.  1    is a schematic cross-sectional view of a light-emitting device  10  according to an embodiment. The light-emitting device  10  may include a first electrode  110 , an interlayer  130 , and a second electrode  150 . 
     Hereinafter, the structure of the light-emitting device  10  according to an embodiment and a method of manufacturing the light-emitting device  10  will be described with reference to  FIG.  1   . 
     First Electrode  110   
     In  FIG.  1   , a substrate may be additionally under the first electrode  110  and/or on the second electrode  150 . As the substrate, a glass substrate and/or a plastic substrate may be used. In one or more embodiments, the substrate may be a flexible substrate, and may include plastics having excellent heat resistance and durability, such as polyimide, polyethylene terephthalate (PET), polycarbonate, polyethylene naphthalate, polyarylate (PAR), polyetherimide, or any combination thereof. 
     The first electrode  110  may be formed by, for example, depositing and/or sputtering a material for forming the first electrode  110  on the substrate. When the first electrode  110  is an anode, a material for forming the first electrode  110  may be a high-work function material that facilitates injection of holes. 
     The first electrode  110  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. When the first electrode  110  is a transmissive electrode, a material for forming the first electrode  110  may include indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), zinc oxide (ZnO), or any combination thereof. In one or more embodiments, when the first electrode  110  is a semi-transmissive electrode or a reflective electrode, a material for forming the first electrode  110  may include magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), or any combination thereof. 
     The first electrode  110  may have a single-layered structure consisting of a single layer or a multi-layered structure including a plurality of layers. For example, the first electrode  110  may have a three-layered structure of ITO/Ag/ITO. 
     Interlayer  130   
     The interlayer  130  may be on the first electrode  110 . The interlayer  130  may include an emission layer. 
     The interlayer  130  may further include a hole transport region between the first electrode  110  and the emission layer and an electron transport region between the emission layer and the second electrode  150 . 
     The interlayer  130  may further include, in addition to various suitable organic materials, a metal-containing compound such as an organometallic compound, an inorganic material such as quantum dots, and/or the like. 
     The interlayer  130  may include i) two or more emitting units sequentially stacked between the first electrode  110  and the second electrode  150 , and ii) a charge generation layer between the two or more emitting units. When the interlayer  130  includes emitting units and a charge generation layer as described above, the light-emitting device  10  may be a tandem light-emitting device. 
     Hole Transport Region in Interlayer  130   
     The hole transport region may have i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer consisting of a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. 
     The hole transport region may include a hole injection layer, a hole transport layer, an emission auxiliary layer, an electron blocking layer, or any combination thereof. 
     For example, the hole transport region may have a multi-layered structure including a hole injection layer/hole transport layer structure, a hole injection layer/hole transport layer/emission auxiliary layer structure, a hole injection layer/emission auxiliary layer structure, a hole transport layer/emission auxiliary layer structure, or a hole injection layer/hole transport layer/electron blocking layer structure, the layers of each structure being stacked sequentially from the first electrode  110 . 
     The hole transport region may include a compound represented by Formula 201, a compound represented by Formula 202, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 201 and 202, 
     L 201  to L 204  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     L 205  may be *—O—*′, *—S—*′, *—N(Q 201 )-*′, a C 1 -C 20  alkylene group unsubstituted or substituted with at least one R 10a , a C 2 -C 20  alkenylene group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xa1 to xa4 may each independently be an integer from 0 to 5, 
     xa5 may be an integer from 1 to 10, 
     R 201  to R 204  and Q 201  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     R 201  and R 202  may optionally be linked to each other via a single bond, a C 1 -C 5  alkylene group unsubstituted or substituted with at least one R 10a , or a C 2 -C 5  alkenylene group unsubstituted or substituted with at least one R 10a  to form a C 8 -C 60  polycyclic group (for example, a carbazole group or the like) unsubstituted or substituted with at least one R 10a  (for example, see Compound HT16), 
     R 203  and R 204  may optionally be linked to each other via a single bond, a C 1 -C 5  alkylene group unsubstituted or substituted with at least one R 10a , or a C 2 -C 5  alkenylene group unsubstituted or substituted with at least one R 10a  to form a C 8 -C 60  polycyclic group unsubstituted or substituted with at least one R 10a , and 
     na1 may be an integer from 1 to 4. 
     For example, each of Formulae 201 and 202 may include at least one of groups represented by Formulae CY201 to CY217: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein, in Formulae CY201 to CY217, R 10b  and R 10c  are the same as described in connection with R 10a , ring CY201 to ring CY204 may each independently be a C 3 -C 20  carbocyclic group or a C 1 -C 20  heterocyclic group, and at least one hydrogen in Formulae CY201 to CY217 may be unsubstituted or substituted with R 10a  as described herein. 
     In an embodiment, ring CY201 to ring CY204 in Formulae CY201 to CY217 may each independently be a benzene group, a naphthalene group, a phenanthrene group, or an anthracene group. 
     In one or more embodiments, each of Formulae 201 and 202 may include at least one of groups represented by Formulae CY201 to CY203. 
     In one or more embodiments, Formula 201 may include at least one of groups represented by Formulae CY201 to CY203 and at least one of groups represented by Formulae CY204 to CY217. 
     In one or more embodiments, in Formula 201, xa1 may be 1, R 20 1 may be a group represented by one of Formulae CY201 to CY203, xa2 may be 0, and R 202  may be a group represented by one of Formulae CY204 to CY207. 
     In one or more embodiments, each of Formulae 201 and 202 may not include a group represented by one of Formulae CY201 to CY203. 
     In one or more embodiments, each of Formulae 201 and 202 may not include a group represented by one of Formulae CY201 to CY203, and may include at least one of groups represented by Formulae CY204 to CY217. 
     In one or more embodiments, each of Formulae 201 and 202 may not include a group represented by one of Formulae CY201 to CY217. 
     For example, the hole transport region may include one of Compounds HT1 to HT46, m-MTDATA, TDATA, 2-TNATA, NPB(NPD), p-NPB, TPD, Spiro-TPD, Spiro-NPB, methylated NPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzenesulfonic acid (PANI/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the hole transport region may be in a range of about 50 Å to about 10,000 Å, for example, about 100 Å to about 4,000 Å. When the hole transport region includes a hole injection layer, a hole transport layer, or any combination thereof, a thickness of the hole injection layer may be in a range of about 100 Å to about 9,000 Å, for example, about 100 Å to about 1,000 Å, and a thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, for example, about 100 Å to about 1,500 Å. When the thicknesses of the hole transport region, the hole injection layer, and the hole transport layer are within the ranges described above, suitable or satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The emission auxiliary layer may increase light-emission efficiency by compensating for an optical resonance distance according to the wavelength of light emitted by the emission layer, and the electron blocking layer may block or reduce the leakage of electrons from the emission layer to the hole transport region. Materials that may be included in the hole transport region may be included in the emission auxiliary layer and the electron blocking layer. 
     p-Dopant 
     The hole transport region may further include, in addition to the materials as described above, a charge-generation material for improving conductive properties (e.g., electrically conductive properties). The charge-generation material may be uniformly or non-uniformly dispersed in the hole transport region (for example, in the form of a single layer consisting of a charge-generation material). 
     The charge-generation material may be, for example, a p-dopant. 
     For example, the lowest unoccupied molecular orbital (LUMO) energy level of the p-dopant may be −3.5 eV or less. 
     In an embodiment, the p-dopant may include a quinone derivative, a cyano group-containing compound, a compound containing element EL1 and element EL2, or any combination thereof. 
     Examples of the quinone derivative may include TCNQ, F4-TCNQ, and the like. 
     Examples of the cyano group-containing compound may include HAT-CN, a compound represented by Formula 221, and the like: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 221, 
     R 221  to R 223  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , and 
     at least one of R 221  to R 223  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each substituted with: a cyano group; —F; —Cl; —Br; —I; a C 1 -C 20  alkyl group substituted with a cyano group, —F, —Cl, —Br, —I, or any combination thereof; or any combination thereof. 
     In the compound containing element EL1 and element EL2, element EL1 may be metal, metalloid, or a combination thereof, and element EL2 may be non-metal, metalloid, or a combination thereof. 
     Examples of the metal may include: an alkali metal (for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), etc.); alkaline earth metal (for example, beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), etc.); a transition metal (for example, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), etc.); a post-transition metal (for example, zinc (Zn), indium (In), tin (Sn), etc.); and a lanthanide metal (for example, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.). 
     Examples of the metalloid may include silicon (Si), antimony (Sb), and tellurium (Te). 
     Examples of the non-metal may include oxygen (O) and halogen (for example, F, Cl, Br, I, etc.). 
     Examples of the compound containing element EL1 and element EL2 may include metal oxide, metal halide (for example, metal fluoride, metal chloride, metal bromide, or metal iodide), metalloid halide (for example, metalloid fluoride, metalloid chloride, metalloid bromide, or metalloid iodide), metal telluride, or any combination thereof. 
     Examples of the metal oxide may include tungsten oxide (for example, WO, W 2 O 3 , WO 2 , WO 3 , W 2 O 5 , etc.), vanadium oxide (for example, VO, V 2 O 3 , VO 2 , V 2 O 5 , etc.), molybdenum oxide (MoO, Mo 2 O 3 , MoO 2 , MoO 3 , Mo 2 O 5 , etc.), and rhenium oxide (for example, ReO 3 , etc.). 
     Examples of the metal halide may include alkali metal halide, alkaline earth metal halide, transition metal halide, post-transition metal halide, and lanthanide metal halide. 
     Examples of the alkali metal halide may include LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. 
     Examples of the alkaline earth metal halide may include BeF 2 , MgF 2 , CaF 2 , SrF 2 , BaF 2 , BeCl 2 , MgCl 2 , CaCl 2 ), SrCl 2 , BaCl 2 , BeBr 2 , MgBr 2 , CaBr 2 , SrBr 2 , BaBr 2 , BeI 2 , MgI 2 , CaI 2 , SrI 2 , and BaI 2 . 
     Examples of the transition metal halide may include titanium halide (for example, TiF 4 , TiCl 4 , TiBr 4 , TiI 4 , etc.), zirconium halide (for example, ZrF 4 , ZrCl 4 , ZrBr 4 , ZrI 4 , etc.), hafnium halide (for example, HfF 4 , HfCl 4 , HfBr 4 , HfI 4 , etc.), vanadium halide (for example, VF 3 , VCl 3 , VBr 3 , VI 3 , etc.), niobium halide (for example, NbF 3 , NbCl 3 , NbBr 3 , NbI 3 , etc.), tantalum halide (for example, TaF 3 , TaCl 3 , TaBr 3 , TaI 3 , etc.), chromium halide (for example, CrF 3 , CrO 3 , CrBr 3 , CrI 3 , etc.), molybdenum halide (for example, MoF 3 , MoCl 3 , MoBr 3 , MoI 3 , etc.), tungsten halide (for example, WF 3 , WCl 3 , WBr 3 , WI 3 , etc.), manganese halide (for example, MnF 2 , MnCl 2 , MnBr 2 , MnI 2 , etc.), technetium halide (for example, TcF 2 , TcCl 2 , TcBr 2 , TcI 2 , etc.), rhenium halide (for example, ReF 2 , ReCl 2 , ReBr 2 , ReI 2 , etc.), iron halide (for example, FeF 2 , FeCl 2 , FeBr 2 , FeI 2 , etc.), ruthenium halide (for example, RuF 2 , RuCl 2 , RuBr 2 , RuI 2 , etc.), osmium halide (for example, OsF 2 , OsCl 2 , OsBr 2 , OsI 2 , etc.), cobalt halide (for example, CoF 2 , COCl 2 , CoBr 2 , CoI 2 , etc.), rhodium halide (for example, RhF 2 , RhCl 2 , RhBr 2 , RhI 2 , etc.), iridium halide (for example, IrF 2 , IrCl 2 , IrBr 2 , IrI 2 , etc.), nickel halide (for example, NiF 2 , NiCl 2 , NiBr 2 , NiI 2 , etc.), palladium halide (for example, PdF 2 , PdCl 2 , PdBr 2 , PdI 2 , etc.), platinum halide (for example, PtF 2 , PtCl 2 , PtBr 2 , PtI 2 , etc.), copper halide (for example, CuF, CuCl, CuBr, CuI, etc.), silver halide (for example, AgF, AgCl, AgBr, AgI, etc.), and gold halide (for example, AuF, AuCl, AuBr, Aul, etc.). 
     Examples of the post-transition metal halide may include zinc halide (for example, ZnF 2 , ZnCl 2 , ZnBr 2 , ZnI 2 , etc.), indium halide (for example, InI 3 , etc.), and tin halide (for example, SnI 2 , etc.). 
     Examples of the lanthanide metal halide may include YbF, YbF 2 , YbF 3 , SmF 3 , YbCl, YbCl 2 , YbCl 3  SmCl 3 , YbBr, YbBr 2 , YbBr 3 , SmBr 3 , YbI, YbI 2 , YbI 3 , and SmI 3 . 
     Examples of the metalloid halide may include antimony halide (for example, SbCl 5 , etc.). 
     Examples of the metal telluride may include alkali metal telluride (for example, Li 2 Te, Na 2 Te, K 2 Te, Rb 2 Te, Cs 2 Te, etc.), alkaline earth metal telluride (for example, BeTe, MgTe, CaTe, SrTe, BaTe, etc.), transition metal telluride (for example, TiTe 2 , ZrTe 2 , HfTe 2 , V 2 Te 3 , Nb 2 Te 3 , Ta 2 Te 3 , Cr 2 Te 3 , Mo 2 Te 3 , W 2 Te 3 , MnTe, TcTe, ReTe, FeTe, RuTe, OsTe, CoTe, RhTe, IrTe, NiTe, PdTe, PtTe, Cu 2 Te, CuTe, Ag 2 Te, AgTe, Au 2 Te, etc.), post-transition metal telluride (for example, ZnTe, etc.), and lanthanide metal telluride (for example, LaTe, CeTe, PrTe, NdTe, PmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, etc.). 
     Emission Layer in Interlayer  130   
     When the light-emitting device  10  is a full-color light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and/or a blue emission layer, according to a sub-pixel. In one or more embodiments, the emission layer may have a stacked structure of two or more layers of a red emission layer, a green emission layer, and a blue emission layer, in which the two or more layers contact (e.g., physically contact) each other or are separated from each other to emit white light. In one or more embodiments, the emission layer may include two or more materials of a red light-emitting material, a green light-emitting material, and a blue light-emitting material, in which the two or more materials are mixed together with each other in a single layer to emit white light. 
     The emission layer may include a host and a dopant. The dopant may include a phosphorescent dopant, a fluorescent dopant, or any combination thereof. 
     The amount of the dopant in the emission layer may be from about 0.01 to about 15 parts by weight based on 100 parts by weight of the host. 
     In one or more embodiments, the emission layer may include a quantum dot. 
     The emission layer may include a delayed fluorescence material. The delayed fluorescence material may serve as a host or a dopant in the emission layer. 
     A thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. When the thickness of the emission layer is within the range described above, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Host 
     The host may include a compound represented by Formula 301: 
       [Ar 301 ] xb11 -[(L 301 ) xb1 -R 301 ] xb21   Formula 301
 
     wherein, in Formula 301, 
     Ar 301  and L 301  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xb11 may be 1, 2, or 3, 
     xb1 may be an integer from 0 to 5, 
     R 301  may be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 301 )(Q 302 )(Q 303 ), —N(Q 301 )(Q 302 ), —B(Q 301 )(Q 302 ), —C(═O)(Q 301 ), —S(═O) 2 (Q 301 ), or —P(═O)(Q 301 )(Q 302 ), 
     xb21 may be an integer from 1 to 5, and 
     Q 301  to Q 303  are the same as described in connection with Q 1 . 
     For example, when xb11 in Formula 301 is 2 or more, two or more of Ar 301  (s) may be linked to each other via a single bond. 
     In one or more embodiments, the host may include a compound represented by Formula 301-1, a compound represented by Formula 301-2, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 301-1 and 301-2, 
     ring A 301  to ring A 304  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     X 301  may be O, S, N-[(L 304 ) xb4 -R 304 ], C(R 304 )(R 305 ), or Si(R 304 )(R 305 ), 
     xb22 and xb23 may each independently be 0, 1, or 2, 
     L 301 , xb1, and R 301  are the same as described in the present specification, 
     L 302  to L 304  are each independently the same as described in connection with L 301 , 
     xb2 to xb4 are each independently the same as described in connection with xb1, and 
     R 302  to R 305  and R 311  to R 314  are the same as described in connection with R 301 . 
     In one or more embodiments, the host may include an alkali earth metal complex, a post-transition metal complex, or any combination thereof. For example, the host may include a Be complex (for example, Compound H55), an Mg complex, a Zn complex, or any combination thereof. 
     In one or more embodiments, the host may include one of Compounds H1 to H124, 9,10-di(2-naphthyl)anthracene (ADN), 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN), 9,10-di-(2-naphthyl)-2-t-butyl-anthracene (TBADN), 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), 1,3-di-9-carbazolylbenzene (mCP), 1,3,5-tri(carbazol-9-yl)benzene (TCP), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Phosphorescent Dopant 
     The phosphorescent dopant may include at least one transition metal as a central metal atom. 
     The phosphorescent dopant may include a monodentate ligand, a bidentate ligand, a tridentate ligand, a tetradentate ligand, a pentadentate ligand, a hexadentate ligand, or any combination thereof. 
     The phosphorescent dopant may be electrically neutral. 
     For example, the phosphorescent dopant may include an organometallic compound represented by Formula 401: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 401 and 402, 
     M may be a transition metal (for example, iridium (Ir), platinum (Pt), palladium (Pd), osmium (Os), titanium (Ti), gold (Au), hafnium (Hf), europium (Eu), terbium (Tb), rhodium (Rh), rhenium (Re), or thulium (Tm)), 
     L 401  may be a ligand represented by Formula 402, and xc1 may be 1, 2, or 3, wherein, when xc1 is 2 or more, two or more of L 401  (s) may be identical to or different from each other, 
     L 402  may be an organic ligand, and xc2 may be 0, 1, 2, 3, or 4, wherein, when xc2 is 2 or more, two or more of L 402 (s) may be identical to or different from each other, 
     X 401  and X 402  may each independently be nitrogen or carbon, 
     ring A 401  and ring A 402  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, 
     T 401  may be a single bond, *—O—*′, *—S—*′, *—C(═O)—*′, *—N(Q 411 )-*′, *—C(Q 411 )(Q 412 )-*′, *—C(Q 411 )=C(Q 412 )-*′, *—C(Q 411 )=*′, or *=C(Q 411 )=*′, 
     X 403  and X 404  may each independently be a chemical bond (for example, a covalent bond or a coordinate bond), O, S, N(Q 413 ), B(Q 413 ), P(Q 413 ), C(Q 413 )(Q 414 ), or Si(Q 413 )(Q 414 ), 
     Q 411  to Q 414  are the same as described in connection with Q 1 , 
     R 401  and R 402  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 401 )(Q 402 )(Q 403 ), —N(Q 401 )(Q 402 ), —B(Q 401 )(Q 402 ), —C(═O)(Q 401 ), —S(═O) 2 (Q 401 ), or —P(═O)(Q 401 )(Q 402 ), 
     Q 401  to Q 403  are the same as described in connection with Q 1 , 
     xc11 and xc12 may each independently be an integer from 0 to 10, and 
     * and *′ in Formula 402 each indicate a binding site to M in Formula 401. 
     For example, in Formula 402, i) X 401  may be nitrogen, and X 402  may be carbon, or ii) each of X 401  and X 402  may be nitrogen. 
     In one or more embodiments, when xc1 in Formula 401 is 2 or more, two ring A 401 (s) in two or more of L 401 (s) may be optionally linked to each other via T 402 , which is a linking group, and two ring A 402 (s) may be optionally linked to each other via T 403 , which is a linking group (see Compounds PD1 to PD4 and PD7). T 402  and T 403  are the same as described in connection with T 401 . 
     L 402  in Formula 401 may be an organic ligand. For example, L 402  may include a halogen group, a diketone group (for example, an acetylacetonate group), a carboxylic acid group (for example, a picolinate group), —C(═O), an isonitrile group, a —CN group, a phosphorus group (for example, a phosphine group, a phosphite group, etc.), or any combination thereof. 
     The phosphorescent dopant may include, for example, one of Compounds PD1 to PD39 or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Fluorescent Dopant 
     The fluorescent dopant may include an amine group-containing compound, a styryl group-containing compound, or any combination thereof. 
     For example, the fluorescent dopant may include a compound represented by Formula 501: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 501, 
     Ar 501 , L 501  to L 503 , R 501 , and R 502  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xd1 to xd3 may each independently be 0, 1, 2, or 3, and 
     xd4 may be 1, 2, 3, 4, 5, or 6. 
     For example, Ar 501  in Formula 501 may be a condensed cyclic group (for example, an anthracene group, a chrysene group, or a pyrene group) in which three or more monocyclic groups are condensed together. 
     In one or more embodiments, xd4 in Formula 501 may be 2. 
     For example, the fluorescent dopant may include one of Compounds FD1 to FD36, DPVBi, DPAVBi, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Delayed Fluorescence Material 
     The emission layer may include a delayed fluorescence material. 
     In the present specification, the delayed fluorescence material may be selected from compounds capable of emitting delayed fluorescence based on a delayed fluorescence emission mechanism. 
     The delayed fluorescence material included in the emission layer may act as a host or a dopant depending on the type or kind of other materials included in the emission layer. 
     In an embodiment, the difference between the triplet energy level (eV) of the delayed fluorescence material and the singlet energy level (eV) of the delayed fluorescence material may be greater than or equal to 0 eV and less than or equal to 0.5 eV. When the difference between the triplet energy level (eV) of the delayed fluorescence material and the singlet energy level (eV) of the delayed fluorescence material satisfies the above-described range, up-conversion from the triplet state to the singlet state of the delayed fluorescence materials may effectively occur, and thus, the luminescence efficiency of the light-emitting device  10  may be improved. 
     For example, the delayed fluorescence material may include i) a material including at least one electron donor (for example, a π electron-rich C 3 -C 60  cyclic group, such as a carbazole group) and at least one electron acceptor (for example, a sulfoxide group, a cyano group, or a π electron-deficient nitrogen-containing C 1 -C 60  cyclic group), and ii) a material including a C 8 -C 60  polycyclic group in which two or more cyclic groups are condensed while sharing boron (B). 
     Examples of the delayed fluorescence material may include at least one of Compounds, DF1 to DF9: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Quantum Dot 
     The emission layer may include a quantum dot. 
     The term “quantum dot,” as used herein, refers to a crystal of a semiconductor compound, and may include any suitable material capable of emitting light of various suitable emission wavelengths according to the size of the crystal. 
     A diameter of the quantum dot may be, for example, in a range of about 1 nm to about 10 nm. 
     The quantum dot may be synthesized by a wet chemical process, a metal organic chemical vapor deposition process, a molecular beam epitaxy process, or any suitable process similar thereto. 
     The wet chemical process is a method including mixing a precursor material with an organic solvent and then growing a quantum dot particle crystal. When the crystal grows, the organic solvent naturally acts as a dispersant coordinated on the surface of the quantum dot crystal and controls the growth of the crystal so that the growth of quantum dot particles can be controlled through a process which costs lower, and is easier than vapor deposition methods, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), 
     The quantum dot may include a Group II-VI semiconductor compound, a Group III-V semiconductor compound, a Group III-VI semiconductor compound, a Group I—III-VI semiconductor compound, a Group IV-VI semiconductor compound, a Group IV element or compound, or any combination thereof. 
     Examples of the Group II-VI semiconductor compound may include: a binary compound, such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, or MgS; a ternary compound, such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, or MgZnS; a quaternary compound, such as CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, or HgZnSTe; or any combination thereof. 
     Examples of the Group III-V semiconductor compound may include: a binary compound, such as GaN, GaP, GaAs, GaSb, AlN, AlP, AIAs, AISb, InN, InP, InAs, or InSb; a ternary compound, such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AINP, AINAs, AINSb, AIPAs, AIPSb, InGaP, InNP, InAIP, InNAs, InNSb, InPAs, or InPSb; a quaternary compound, such as GaAINP, GaAINAs, GaAINSb, GaAIPAs, GaAIPSb, GaInNP, GaInNAs, GalnNSb, GaInPAs, GalnPSb, InAINP, InAINAs, InAINSb, InAIPAs, or InAIPSb; or any combination thereof. The Group III-V semiconductor compound may further include a Group II element. Examples of the Group III-V semiconductor compound further including the Group II element may include InZnP, InGaZnP, InAIZnP, and the like. 
     Examples of the Group III-VI semiconductor compound may include: a binary compound, such as GaS, GaSe, Ga2Se3, GaTe, InS, InSe, In 2 S3, In 2 Se3, or InTe; a ternary compound, such as InGaS3 or InGaSes; or any combination thereof. 
     Examples of the Group I—III-VI semiconductor compound may include: a ternary compound, such as AgInS, AgInS2, CuInS, CulnS2, CuGaO2, AgGaO2, or AgAIO2; or any combination thereof. 
     Examples of the Group IV-VI semiconductor compound may include: a binary compound, such as SnS, SnSe, SnTe, PbS, PbSe, or PbTe; a ternary compound, such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, or SnPbTe; a quaternary compound, such as SnPbSSe, SnPbSeTe, or SnPbSTe; or any combination thereof. 
     The Group IV element or compound may include: a single element compound, such as Si or Ge; a binary compound, such as SiC or SiGe; or any combination thereof. 
     Each element included in a multi-element compound such as the binary compound, the ternary compound, and the quaternary compound may be present at a uniform concentration or non-uniform concentration in a particle. 
     The quantum dot may have a single structure in which the concentration of each element in the quantum dot is uniform (e.g., substantially uniform), or a core-shell dual structure. For example, the material included in the core and the material included in the shell may be different from each other. 
     The shell of the quantum dot may act as a protective layer that prevents or reduces chemical degeneration of the core to maintain semiconductor characteristics, and/or as a charging layer that imparts electrophoretic characteristics to the quantum dot. The shell may be a single layer or a multi-layer. The interface between the core and the shell may have a concentration gradient in which the concentration of an element existing in the shell decreases along a direction toward the center of the core. 
     Examples of the shell of the quantum dot may include an oxide of metal, metalloid, or non-metal, a semiconductor compound, or a combination thereof. Examples of the oxide of metal, metalloid, or non-metal may include: a binary compound, such as SiO 2 , Al 2 O 3 , TiO 2 , ZnO, MnO, Mn 2 O 3 , Mn 3 O 4 , CuO, FeO, Fe 2 O 3 , Fe 3 O 4 , CoO, Co 3 O 4 , or NiO; a ternary compound, such as MgAl 2 O 4 , CoFe 2 O 4 , NiFe 2 O 4 , or CoMn 2 O 4 ; or any combination thereof. Examples of the semiconductor compound may include, as described herein, a Group II-VI semiconductor compound, a Group III-V semiconductor compound, a Group III-VI semiconductor compound, a Group I—III-VI semiconductor compound, a Group IV-VI semiconductor compound, or any combination thereof. For example, the semiconductor compound may include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AIAs, AIP, AISb, or any combination thereof. 
     A full width at half maximum (FWHM) of an emission wavelength spectrum of the quantum dot may be about 45 nm or less, for example, about 40 nm or less, for example, about 30 nm or less, and within these ranges, color purity or color reproducibility may be increased. In addition, because the light emitted through the quantum dot is emitted in all directions, the wide viewing angle may be improved. 
     In addition, the quantum dot may be a spherical particle, a pyramidal particle, a multi-arm particle, a cubic nanoparticle, a nanotube particle, a nanowire particle, a nanofiber particle, or a nanoplate particle. 
     Because the energy band gap may be adjusted by controlling the size of the quantum dot, light having various suitable wavelength bands may be obtained from the quantum dot emission layer. Accordingly, by using quantum dots of different sizes, a light-emitting device that emits light of various suitable wavelengths may be implemented. In one or more embodiments, the size of the quantum dot may be selected to emit red, green and/or blue light. In addition, the size of the quantum dot may be configured to emit white light by combining light of various suitable colors. 
     Electron Transport Region in Interlayer  130   
     The electron transport region may have i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer consisting of a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. 
     The electron transport region may include a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     For example, the electron transport region may have an electron transport layer/electron injection layer structure, a hole blocking layer/electron transport layer/electron injection layer structure, an electron control layer/electron transport layer/electron injection layer structure, or a buffer layer/electron transport layer/electron injection layer structure, the constituting layers of each structure being sequentially stacked from an emission layer. 
     The electron transport region (for example, the buffer layer, the hole blocking layer, the electron control layer, or the electron transport layer in the electron transport region) may include a metal-free compound including at least one π electron-deficient nitrogen-containing C 1 -C 60  cyclic group. 
     For example, the electron transport region may include a compound represented by Formula 601: 
       [Ar 601 ] xe11 -[(L 601 ) xe1 -R 601 ] xe21   Formula 601
 
     wherein, in Formula 601, 
     Ar 601  and L 601  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xe11 may be 1, 2, or 3, 
     xe1 may be 0, 1, 2, 3, 4, or 5, 
     R 601  may be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 601 )(Q 602 )(Q 603 ), —C(═O)(Q 601 ), —S(═O) 2 (Q 601 ), or —P(═O)(Q 601 )(Q 602 ), 
     Q 601  to Q 603  are the same as described in connection with Q 1 , 
     xe21 may be 1, 2, 3, 4, or 5, and 
     at least one of Ar 601 , L 601 , and R 601  may each independently be a rr electron-deficient nitrogen-containing C 1 -C 60  cyclic group unsubstituted or substituted with at least one R 10a . 
     For example, when xe11 in Formula 601 is 2 or more, two or more of Ar 601 (s) may be linked to each other via a single bond. 
     In one or more embodiments, Ar 601  in Formula 601 may be a substituted or unsubstituted anthracene group. 
     In one or more embodiments, the electron transport region may include a compound represented by Formula 601-1: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 601-1, 
     X 614  may be N or C(R 614 ), X 615  may be N or C(R 615 ), X 616  may be N or C(R 616 ), and at least one of X 614  to X 616  may be N, 
     L 611  to L 613  are the same as described in connection with L 601 , 
     xe611 to xe613 are the same as described in connection with xe1, 
     R 611  to R 613  are the same as described in connection with R 601 , and 
     R 614  to R 616  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a . 
     For example, xe1 and xe611 to xe613 in Formulae 601 and 601-1 may each independently be 0, 1, or 2. 
     The electron transport region may include one of Compounds ET1 to ET45, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), Alq 3 , BAlq, TAZ, NTAZ, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the electron transport region may be in a range of about 100 Å to about 5,000 Å, for example, about 160 Å to about 4,000 Å. When the electron transport region includes a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, or any combination thereof, a thickness of the buffer layer, the hole blocking layer, or the electron control layer may each independently be from about 20 Å to about 1,000 Å, for example, about 30 Å to about 300 Å, and a thickness of the electron transport layer may be from a rag of about 100 Å, for example, about 150 Å to about 500 Å. When the thickness of the buffer layer, the hole blocking layer, the electron control layer, the electron transport layer, and/or the electron transport region are within the ranges described above, suitable or satisfactory electron transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport region (for example, the electron transport layer in the electron transport region) may further include, in addition to the materials described above, a metal-containing material. 
     The metal-containing material may include an alkali metal complex, an alkaline earth metal complex, or any combination thereof. A metal ion of the alkali metal complex may be a Li ion, a Na ion, a K ion, a Rb ion, or a Cs ion, and a metal ion of the alkaline earth metal complex may be a Be ion, a Mg ion, a Ca ion, a Sr ion, or a Ba ion. A ligand coordinated with the metal ion of the alkali metal complex or the alkaline earth-metal complex may include hydroxyquinoline, hydroxyisoquinoline, hydroxybenzoquinoline, hydroxyacridine, hydroxyphenanthridine, hydroxyphenyloxazole, hydroxyphenylthiazole, hydroxyphenyloxadiazole, hydroxyphenylthiadiazole, hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxyphenylbenzothiazole, bipyridine, phenanthroline, cyclopentadiene, or any combination thereof. 
     For example, the metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (LiQ) or ET-D2: 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer that facilitates the injection of electrons from the second electrode  150 . The electron injection layer may be in direct contact with the second electrode  150 . 
     The electron injection layer may have i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer consisting of a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. 
     The electron injection layer may include an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof. 
     The alkali metal may include Li, Na, K, Rb, Cs, or any combination thereof. The alkaline earth metal may include Mg, Ca, Sr, Ba, or any combination thereof. The rare earth metal may include Sc, Y, Ce, Tb, Yb, Gd, or any combination thereof. 
     The alkali metal-containing compound, the alkaline earth metal-containing compound, and the rare earth metal-containing compound may include oxides, halides (for example, fluorides, chlorides, bromides, or iodides), or tellurides of the alkali metal, the alkaline earth metal, and the rare earth metal, or any combination thereof. 
     The alkali metal-containing compound may include alkali metal oxides, such as Li 2 O, Cs 2 O, or K 2 O, alkali metal halides, such as LiF, NaF, CsF, KF, LiI, NaI, CsI, or KI, or any combination thereof. The alkaline earth metal-containing compound may include an alkaline earth metal oxide, such as BaO, SrO, CaO, Ba x Sr 1-x O (wherein x is a real number satisfying the condition of 0&lt;x&lt;1), Ba x Ca 1-x O (wherein x is a real number satisfying the condition of 0&lt;x&lt;1), or the like. The rare earth metal-containing compound may include YbF 3 , ScF 3 , Sc 2 O 3 , Y 2 O 3 , Ce 2 O 3 , GdF 3 , TbF 3 , YbI 3 , ScI 3 , TbI 3 , or any combination thereof. In one or more embodiments, the rare earth metal-containing compound may include lanthanide metal telluride. Examples of the lanthanide metal telluride may include LaTe, CeTe, PrTe, NdTe, PmTe, SmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, La 2 Te 3 , Ce 2 Te 3 , Pr 2 Te 3 , Nd 2 Te 3 , Pm 2 Te 3 , Sm 2 Te 3 , Eu 2 Te 3 , Gd 2 Te 3 , Tb 2 Te 3 , Dy 2 Te 3 , Ho 2 Te 3 , Er 2 Te 3 , Tm 2 Te 3 , Yb 2 Te 3 , and Lu 2 Te 3 . 
     The alkali metal complex, the alkaline earth-metal complex, and the rare earth metal complex may include i) one of ions of the alkali metal, the alkaline earth metal, and the rare earth metal and ii), as a ligand bonded to the metal ion, for example, hydroxyquinoline, hydroxyisoquinoline, hydroxybenzoquinoline, hydroxyacridine, hydroxyphenanthridine, hydroxyphenyloxazole, hydroxyphenylthiazole, hydroxyphenyloxadiazole, hydroxyphenylthiadiazole, hydroxyphenylpyridine, hydroxyphenyl benzimidazole, hydroxyphenylbenzothiazole, bipyridine, phenanthroline, cyclopentadiene, or any combination thereof. 
     The electron injection layer may include (or consist of) an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof, as described above. In one or more embodiments, the electron injection layer may further include an organic material (for example, a compound represented by Formula 601). 
     In an embodiment, the electron injection layer may include (or consist of) i) an alkali metal-containing compound (for example, an alkali metal halide), ii) a) an alkali metal-containing compound (for example, an alkali metal halide); and b) an alkali metal, an alkaline earth metal, a rare earth metal, or any combination thereof. For example, the electron injection layer may be a KI:Yb co-deposited layer, an RbI:Yb co-deposited layer, and/or the like. 
     When the electron injection layer further includes an organic material, an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth-metal complex, a rare earth metal complex, or any combination thereof may be uniformly or non-uniformly dispersed in a matrix including the organic material. 
     A thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, and, for example, about 3 Å to about 90 Å. When the thickness of the electron injection layer is within the range described above, suitable or satisfactory electron injection characteristics may be obtained without a substantial increase in driving voltage. 
     Second Electrode  150   
     The second electrode  150  may be on the interlayer  130  having such a structure. The second electrode  150  may be a cathode, which is an electron injection electrode, and as a material for the second electrode  150 , a metal, an alloy, an electrically conductive compound, or any combination thereof, each having a low-work function, may be used. 
     The second electrode  150  may include lithium (Li), silver (Ag), magnesium (Mg), aluminum (AI), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), ytterbium (Yb), silver-ytterbium (Ag—Yb), ITO, IZO, or any combination thereof. The second electrode  150  may be a transmissive electrode, a semi-transmissive electrode, or a reflective electrode. 
     The second electrode  150  may have a single-layered structure or a multi-layered structure including a plurality of layers. 
     Capping Layer 
     A first capping layer may be outside the first electrode  110 , and/or a second capping layer may be outside the second electrode  150 . In more detail, the light-emitting device  10  may have a structure in which the first capping layer, the first electrode  110 , the interlayer  130 , and the second electrode  150  are sequentially stacked in this stated order, a structure in which the first electrode  110 , the interlayer  130 , the second electrode  150 , and the second capping layer are sequentially stacked in this stated order, or a structure in which the first capping layer, the first electrode  110 , the interlayer  130 , the second electrode  150 , and the second capping layer are sequentially stacked in this stated order. 
     Light generated in an emission layer of the interlayer  130  of the light-emitting device  10  may be extracted toward the outside through the first electrode  110  which is a semi-transmissive electrode or a transmissive electrode, and the first capping layer. Light generated in an emission layer of the interlayer  130  of the light-emitting device  10  may be extracted toward the outside through the second electrode  150  which is a semi-transmissive electrode or a transmissive electrode, and the second capping layer. 
     The first capping layer and the second capping layer may increase external luminescence efficiency according to the principle of constructive interference. Accordingly, the light extraction efficiency of the light-emitting device  10  may be increased, so that the luminescence efficiency of the light-emitting device  10  may be improved. 
     Each of the first capping layer and the second capping layer may include a material having a refractive index of 1.6 or more (at a wavelength of 589 nm). 
     The first capping layer and the second capping layer may each independently be an organic capping layer including an organic material, an inorganic capping layer including an inorganic material, or an organic-inorganic composite capping layer including an organic material and an inorganic material. 
     At least one of the first capping layer and the second capping layer may each independently include a carbocyclic compound, a heterocyclic compound, an amine group-containing compound, a porphine derivative, a phthalocyanine derivative, a naphthalocyanine derivative, an alkali metal complex, an alkaline earth metal complex, or any combination thereof. The carbocyclic compound, the heterocyclic compound, and the amine group-containing compound may be optionally substituted with a substituent containing O, N, S, Se, Si, F, Cl, Br, I, or any combination thereof. In an embodiment, at least one of the first capping layer and the second capping layer may each independently include an amine group-containing compound. 
     For example, at least one of the first capping layer or the second capping layer may each independently include a compound represented by Formula 201, a compound represented by Formula 202, or any combination thereof. 
     In one or more embodiments, at least one of the first capping layer or the second capping layer may each independently include one of Compounds HT28 to HT33, one of Compounds CP1 to CP6, β-NPB, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Film 
     The heterocyclic compound represented by Formula 1 may be included in various suitable films. Accordingly, another aspect of embodiments provides a film including the heterocyclic compound represented by Formula 1. The film may be, for example, an optical member (or, a light control means) (for example, a color filter, a color conversion member, a capping layer, a light extraction efficiency enhancement layer, a selective light absorbing layer, a polarizing layer, a quantum dot-containing layer, and/or the like), a light blocking member (for example, a light reflective layer, a light absorbing layer, and/or the like), or a protective member (for example, an insulating layer, a dielectric layer, and/or the like). 
     Electronic Apparatus 
     The light-emitting device may be included in various suitable electronic apparatuses. For example, the electronic apparatus including the light-emitting device may be a light-emitting apparatus, an authentication apparatus, and/or the like. 
     The electronic apparatus (for example, a light-emitting apparatus) may further include, in addition to the light-emitting device, i) a color filter, ii) a color conversion layer, or iii) a color filter and a color conversion layer. The color filter and/or the color conversion layer may be in at least one traveling direction of light emitted from the light-emitting device. For example, light emitted from the light-emitting device may be blue light or white light. Further details on the light-emitting device are the same as described above. In an embodiment, the color conversion layer may include a quantum dot. The quantum dot may be, for example, a quantum dot as described herein. 
     The electronic apparatus may include a first substrate. The first substrate may include a plurality of subpixel areas, the color filter may include a plurality of color filter areas respectively corresponding to the subpixel areas, and the color conversion layer may include a plurality of color conversion areas respectively corresponding to the subpixel areas. 
     A pixel-defining film may be among the subpixel areas to define each of the subpixel areas. 
     The color filter may further include a plurality of color filter areas and light-shielding patterns among the color filter areas, and the color conversion layer may include a plurality of color conversion areas and light-shielding patterns among the color conversion areas. 
     The plurality of color filter areas (or the plurality of color conversion areas) may include a first area to emit a first-color light, a second area to emit a second-color light, and/or a third area emit a third-color light, wherein the first-color light, the second-color light, and/or the third-color light may have different maximum emission wavelengths from one another. For example, the first-color light may be red light, the second-color light may be green light, and the third-color light may be blue light. For example, the plurality of color filter areas (or the plurality of color conversion areas) may include quantum dots. In more detail, the first area may include a red quantum dot, the second area may include a green quantum dot, and the third area may not include a quantum dot. The quantum dot is the same as described in the present specification. The first area, the second area, and/or the third area may each further include a scatterer. 
     For example, the light-emitting device may emit first light, the first area may absorb the first light to emit a first first-color light, the second area may absorb the first light to emit a second first-color light, and the third area may absorb the first light to emit a third first-color light. In this regard, the first first-color light, the second first-color light, and the third first-color light may have different maximum emission wavelengths. In more detail, the first light may be blue light, the first first-color light may be red light, the second first-color light may be green light, and the third first-color light may be blue light. 
     The electronic apparatus may further include a thin-film transistor, in addition to the light-emitting device as described above. The thin-film transistor may include a source electrode, a drain electrode, and an active layer, wherein any one of the source electrode and the drain electrode may be electrically connected to any one of the first electrode and the second electrode of the light-emitting device. 
     The thin-film transistor may further include a gate electrode, a gate insulating film, and/or the like. 
     The active layer may include crystalline silicon, amorphous silicon, organic semiconductor, oxide semiconductor, and/or the like. 
     The electronic apparatus may further include a sealing portion for sealing the light-emitting device. The sealing portion may be between the color filter and/or color conversion layer and the light-emitting device. The sealing portion allows light from the light-emitting device to be extracted to the outside, while concurrently (e.g., simultaneously) preventing or reducing penetration of ambient air and/or moisture into the light-emitting device. The sealing portion may be a sealing substrate including a transparent glass substrate and/or a plastic substrate. The sealing portion may be a thin-film encapsulation layer including at least one layer of an organic layer and/or an inorganic layer. When the sealing portion is a thin film encapsulation layer, the electronic apparatus may be flexible. 
     Various suitable functional layers may be additionally on the sealing portion, in addition to the color filter and/or the color conversion layer, according to the use of the electronic apparatus. Examples of the functional layers may include a touch screen layer, a polarizing layer, and the like. The touch screen layer may be a pressure-sensitive touch screen layer, a capacitive touch screen layer, and/or an infrared touch screen layer. The authentication apparatus may be, for example, a biometric authentication apparatus that authenticates an individual by using biometric information of a living body (for example, fingertips, pupils, etc.). 
     The authentication apparatus may further include, in addition to the light-emitting device as described above, a biometric information collector. 
     The electronic apparatus may be applied to various suitable displays, light sources, lighting, personal computers (for example, a mobile personal computer), mobile phones, digital cameras, electronic organizers, electronic dictionaries, electronic game machines, medical instruments (for example, electronic thermometers, sphygmomanometers, blood glucose meters, pulse measurement devices, pulse wave measurement devices, electrocardiogram displays, ultrasonic diagnostic devices, and/or endoscope displays), fish finders, various measuring instruments, meters (for example, meters for a vehicle, an aircraft, and a vessel), projectors, and/or the like. 
     Description of  FIGS.  2  and  3     
       FIG.  2    is a cross-sectional view of a light-emitting apparatus according to an embodiment. 
     The light-emitting apparatus of  FIG.  2    may include a substrate  100 , a thin-film transistor (TFT), a light-emitting device, and an encapsulation portion  300  that seals the light-emitting device. 
     The substrate  100  may be a flexible substrate, a glass substrate, and/or a metal substrate. A buffer layer  210  may be on the substrate  100 . The buffer layer  210  may prevent or reduce penetration of impurities through the substrate  100  and may provide a flat surface on the substrate  100 . 
     A TFT may be on the buffer layer  210 . The TFT may include an active layer  220 , a gate electrode  240 , a source electrode  260 , and a drain electrode  270 . 
     The active layer  220  may include an inorganic semiconductor such as silicon or polysilicon, an organic semiconductor, or an oxide semiconductor, and may include a source region, a drain region, and a channel region. 
     A gate insulating film  230  for insulating the active layer  220  from the gate electrode  240  may be on the active layer  220 , and the gate electrode  240  may be on the gate insulating film  230 . 
     An interlayer insulating film  250  may be on the gate electrode  240 . The interlayer insulating film  250  may be between the gate electrode  240  and the source electrode  260  to insulate the gate electrode  240  from the source electrode  260  and between the gate electrode  240  and the drain electrode  270  to insulate the gate electrode  240  from the drain electrode  270 . 
     The source electrode  260  and the drain electrode  270  may be on the interlayer insulating film  250 . The interlayer insulating film  250  and the gate insulating film  230  may be formed to expose the source region and the drain region of the active layer  220 , and the source electrode  260  and the drain electrode  270  may be in contact (e.g., physical contact) with the exposed portions of the source region and the drain region of the active layer  220 . 
     The TFT is electrically connected to a light-emitting device to drive the light-emitting device, and is covered by a passivation layer  280 . The passivation layer  280  may include an inorganic insulating film, an organic insulating film, or a combination thereof. A light-emitting device is provided on the passivation layer  280 . The light-emitting device may include a first electrode  110 , an interlayer  130 , and a second electrode  150 . 
     The first electrode  110  may be on the passivation layer  280 . The passivation layer  280  may expose a portion of the drain electrode  270  without fully covering the drain electrode  270 , and the first electrode  110  may be connected to the exposed portion of the drain electrode  270 . 
     A pixel defining layer  290  including an insulating material may be on the first electrode  110 . The pixel defining layer  290  may expose a portion of the first electrode  110 , and an interlayer  130  may be formed in the exposed portion of the first electrode  110 . The pixel defining layer  290  may be a polyimide and/or polyacrylic organic film. In some embodiments, at least some layers of the interlayer  130  may extend beyond the upper portion of the pixel defining layer  290  in the form of a common layer. 
     The second electrode  150  may be on the interlayer  130 , and a capping layer  170  may be additionally formed on the second electrode  150 . The capping layer  170  may be formed to cover the second electrode  150 . 
     The encapsulation portion  300  may be on the capping layer  170 . The encapsulation portion  300  may be on a light-emitting device to protect the light-emitting device from moisture and/or oxygen. The encapsulation portion  300  may include: an inorganic film including silicon nitride (SiNx), silicon oxide (SiOx), indium tin oxide, indium zinc oxide, or any combination thereof; an organic film including polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, polyethylene sulfonate, polyoxymethylene, polyarylate, hexamethyldisiloxane, an acrylic resin (for example, polymethyl methacrylate, polyacrylic acid, and/or the like), an epoxy-based resin (for example, aliphatic glycidyl ether (AGE), and/or the like), or any combination thereof; or a combination of the inorganic film and the organic film. 
       FIG.  3    is a cross-sectional view of a light-emitting apparatus according to an embodiment. 
     The light-emitting apparatus of  FIG.  3    is substantially the same as the light-emitting apparatus of  FIG.  2   , except that a light-shielding pattern  500  and a functional region  400  are additionally on the encapsulation portion  300 . The functional region  400  may be i) a color filter area, ii) a color conversion area, or iii) a combination of the color filter area and the color conversion area. In an embodiment, the light-emitting device included in the light-emitting apparatus of  FIG.  3    may be a tandem light-emitting device. 
     Manufacture Method 
     Respective layers included in the hole transport region, the emission layer, and respective layers included in the electron transport region may be formed in a certain region by using one or more suitable methods selected from vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) deposition, ink-jet printing, laser-printing, laser-induced thermal imaging, and the like. 
     When layers constituting the hole transport region, the emission layer, and layers constituting the electron transport region are formed by vacuum deposition, the deposition may be performed at a deposition temperature of about 100° C. to about 500° C., a vacuum degree of about 10 −8  torr to about 10 −3  torr, and a deposition speed of about 0.01 Å/sec to about 100 Å/sec, depending on a material to be included in a layer to be formed and the structure of a layer to be formed. 
     Definition of Terms 
     The term “C 3 -C 60  carbocyclic group,” as used herein, refers to a cyclic group consisting of carbon only as a ring-forming atom and having 3 to 60 carbon atoms, and the term “C 1 -C 60  heterocyclic group,” as used herein, refers to a cyclic group that has 1 to 60 carbon atoms and further has, in addition to carbon, a heteroatom as a ring-forming atom. The C 3 -C 60  carbocyclic group and the C 1 -C 60  heterocyclic group may each be a monocyclic group consisting of one ring or a polycyclic group in which two or more rings are condensed together with each other. For example, the C 1 -C 60  heterocyclic group has 3 to 61 ring-forming atoms. 
     The term “cyclic group,” as used herein, may include the C 3 -C 60  carbocyclic group and the C 1 -C 60  heterocyclic group. 
     The term “π electron-rich C 3 -C 60  cyclic group,” as used herein, refers to a cyclic group that has 3 to 60 carbon atoms and does not include *—N═*′ as a ring-forming moiety, and the term “π electron-deficient nitrogen-containing C 1 -C 60  cyclic group,” as used herein, refers to a heterocyclic group that has 1 to 60 carbon atoms and includes *—N═*′ as a ring-forming moiety. 
     For example, 
     the C 3 -C 60  carbocyclic group may be i) group T1 or ii) a condensed cyclic group in which two or more groups T1 are condensed together with each other (for example, a cyclopentadiene group, an adamantane group, a norbornane group, a benzene group, a pentalene group, a naphthalene group, an azulene group, an indacene group, an acenaphthylene group, a phenalene group, a phenanthrene group, an anthracene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a perylene group, a pentaphene group, a heptalene group, a naphthacene group, a picene group, a hexacene group, a pentacene group, a rubicene group, a coronene group, an ovalene group, an indene group, a fluorene group, a spiro-bifluorene group, a benzofluorene group, an indenophenanthrene group, or an indenoanthracene group), 
     the C 1 -C 60  heterocyclic group may be i) group T2, ii) a condensed cyclic group in which two or more groups T2 are condensed together with each other, or iii) a condensed cyclic group in which at least one group T2 and at least one group T1 are condensed together with each other (for example, a pyrrole group, a thiophene group, a furan group, an indole group, a benzoindole group, a naphthoindole group, an isoindole group, a benzoisoindole group, a naphthoisoindole group, a benzosilole group, a benzothiophene group, a benzofuran group, a carbazole group, a dibenzosilole group, a dibenzothiophene group, a dibenzofuran group, an indenocarbazole group, an indolocarbazole group, a benzofurocarbazole group, a benzothienocarbazole group, a benzosilolocarbazole group, a benzoindolocarbazole group, a benzocarbazole group, a benzonaphthofuran group, a benzonaphthothiophene group, a benzonaphthosilole group, a benzofurodibenzofuran group, a benzofurodibenzothiophene group, a benzothienodibenzothiophene group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzoisoxazole group, a benzothiazole group, a benzoisothiazole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a benzoquinoline group, a benzoisoquinoline group, a quinoxaline group, a benzoquinoxaline group, a quinazoline group, a benzoquinazoline group, a phenanthroline group, a cinnoline group, a phthalazine group, a naphthyridine group, an imidazopyridine group, an imidazopyrimidine group, an imidazotriazine group, an imidazopyrazine group, an imidazopyridazine group, an azacarbazole group, an azafluorene group, an azadibenzosilole group, an azadibenzothiophene group, an azadibenzofuran group, etc.), 
     the rr electron-rich C 3 -C 60  cyclic group may be i) group T1, ii) a condensed cyclic group in which two or more groups T1 are condensed together with each other, iii) group T3, iv) a condensed cyclic group in which two or more groups T3 are condensed together with each other, or v) a condensed cyclic group in which at least one group T3 and at least one group T1 are condensed together with each other (for example, the C 3 -C 60  carbocyclic group, a 1H-pyrrole group, a silole group, a borole group, a 2H-pyrrole group, a 3H-pyrrole group, a thiophene group, a furan group, an indole group, a benzoindole group, a naphthoindole group, an isoindole group, a benzoisoindole group, a naphthoisoindole group, a benzosilole group, a benzothiophene group, a benzofuran group, a carbazole group, a dibenzosilole group, a dibenzothiophene group, a dibenzofuran group, an indenocarbazole group, an indolocarbazole group, a benzofurocarbazole group, a benzothienocarbazole group, a benzosilolocarbazole group, a benzoindolocarbazole group, a benzocarbazole group, a benzonaphthofuran group, a benzonaphthothiophene group, a benzonaphthosilole group, a benzofurodibenzofuran group, a benzofurodibenzothiophene group, a benzothienodibenzothiophene group, etc.), 
     the π electron-deficient nitrogen-containing C 1 -C 60  cyclic group may be i) group T4, ii) a condensed cyclic group in which two or more group T4 are condensed together with each other, iii) a condensed cyclic group in which at least one group T4 and at least one group T1 are condensed together with each other, iv) a condensed cyclic group in which at least one group T4 and at least one group T3 are condensed together with each other, or v) a condensed cyclic group in which at least one group T4, at least one group T1, and at least one group T3 are condensed together with one another (for example, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzoisoxazole group, a benzothiazole group, a benzoisothiazole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a benzoquinoline group, a benzoisoquinoline group, a quinoxaline group, a benzoquinoxaline group, a quinazoline group, a benzoquinazoline group, a phenanthroline group, a cinnoline group, a phthalazine group, a naphthyridine group, an imidazopyridine group, an imidazopyrimidine group, an imidazotriazine group, an imidazopyrazine group, an imidazopyridazine group, an azacarbazole group, an azafluorene group, an azadibenzosilole group, an azadibenzothiophene group, an azadibenzofuran group, etc.), 
     group T1 may be a cyclopropane group, a cyclobutane group, a cyclopentane group, a cyclohexane group, a cycloheptane group, a cyclooctane group, a cyclobutene group, a cyclopentene group, a cyclopentadiene group, a cyclohexene group, a cyclohexadiene group, a cycloheptene group, an adamantane group, a norbornane (or 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, or a benzene group, 
     group T2 may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, a borole group, a 2H-pyrrole group, a 3H-pyrrole group, an imidazole group, a pyrazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, an azasilole group, an azaborole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a tetrazine group, a pyrrolidine group, an imidazolidine group, a dihydropyrrole group, a piperidine group, a tetrahydropyridine group, a dihydropyridine group, a hexahydropyrimidine group, a tetrahydropyrimidine group, a dihydropyrimidine group, a piperazine group, a tetrahydropyrazine group, a dihydropyrazine group, a tetrahydropyridazine group, or a dihydropyridazine group, 
     group T3 may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, or a borole group, and 
     group T4 may be a 2H-pyrrole group, a 3H-pyrrole group, an imidazole group, a pyrazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, an azasilole group, an azaborole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, or a tetrazine group. 
     The term “cyclic group”, “C 3 -C 60  carbocyclic group”, “C 1 -C 60  heterocyclic group”, “π electron-rich C 3 -C 60  cyclic group”, or “π electron-deficient nitrogen-containing C 1 -C 60  cyclic group,” as used herein, refers to a group condensed to any cyclic group, a monovalent group, or a polyvalent group (for example, a divalent group, a trivalent group, a tetravalent group, etc.), depending on the structure of a formula in connection with which the terms are used. For example, the “benzene group” may be a benzo group, a phenyl group, a phenylene group, or the like, which may be easily understood by one of ordinary skill in the art according to the structure of a formula including the “benzene group.” 
     Examples of the monovalent C 3 -C 60  carbocyclic group and the monovalent C 1 -C 60  heterocyclic group may include 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 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, and examples of the divalent C 3 -C 60  carbocyclic group and the monovalent C 1 -C 60  heterocyclic group may include a C 3 -C 10  cycloalkylene group, a C 1 -C 10  heterocycloalkylene group, a C 3 -C 10  cycloalkenylene group, a C 1 -C 10  heterocycloalkenylene group, a C 6 -C 60  arylene group, a C 1 -C 60  heteroarylene group, a divalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted divalent non-aromatic condensed heteropolycyclic group. 
     The term “C 1 -C 60  alkyl group,” as used herein, refers to a linear or branched aliphatic hydrocarbon monovalent group that has one to sixty carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. The term “C 1 -C 60  alkylene group,” as used herein, refers to a divalent group having substantially the same structure as the C 1 -C 60  alkyl group. 
     The term “C 2 -C 60  alkenyl group,” as used herein, refers to a monovalent hydrocarbon group having at least one carbon-carbon double bond at a main chain (e.g., in the middle) or at a terminal end (e.g., the terminus) of the C 2 -C 60  alkyl group, and examples thereof include an ethenyl group, a propenyl group, and a butenyl group. The term “C 2 -C 60  alkenylene group,” as used herein, refers to a divalent group having substantially the same structure as the C 2 -C 60  alkenyl group. 
     The term “C 2 -C 60  alkynyl group,” as used herein, refers to a monovalent hydrocarbon group having at least one carbon-carbon triple bond at a main chain (e.g., in the middle) or at a terminal end (e.g., the terminus) of the C 2 -C 60  alkyl group, and examples thereof include an ethynyl group and a propynyl group. The term “C 2 -C 60  alkynylene group,” as used herein, refers to a divalent group having substantially the same structure as the C 2 -C 60  alkynyl group. 
     The term “C 1 -C 60  alkoxy group,” as used herein, refers to a monovalent group represented by -OA 11  (wherein A 101  is the C 1 -C 60  alkyl group), and examples thereof include a methoxy group, an ethoxy group, and an isopropyloxy 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 examples thereof 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 (or a bicyclo[2.2.1]heptyl group), a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, and a bicyclo[2.2.2]octyl group. The term “C 3 -C 1  cycloalkylene group” as used herein refers to a divalent group having substantially the same structure as the C 3 -C 10  cycloalkyl group. 
     The term “C 1 -C 1  heterocycloalkyl group,” as used herein, refers to a monovalent cyclic group of 1 to 10 carbon atoms, further including, in addition to carbon atoms, at least one heteroatom, as ring-forming atoms, and examples thereof include a 1,2,3,4-oxatriazolidinyl group, a tetrahydrofuranyl group, and a tetrahydrothiophenyl group. The term “C 1 -C 1  heterocycloalkylene group,” as used herein, refers to a divalent group having substantially the same structure as the C 1 -C 1 a heterocycloalkyl group. 
     The term “C 3 -C 10  cycloalkenyl group,” as used herein, refers to a monovalent cyclic group that has 3 to 10 carbon atoms and at least one carbon-carbon double bond in the ring thereof and no aromaticity (e.g., is not aromatic), and examples thereof include a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. The term “C 3 -C 10  cycloalkenylene group,” as used herein, refers to a divalent group having substantially the same structure as the C 3 -C 10  cycloalkenyl group. 
     The term “C 1 -C 1 a heterocycloalkenyl group,” as used herein, refers to a monovalent cyclic group of 1 to 10 carbon atoms, further including, in addition to carbon atoms, at least one heteroatom, as ring-forming atoms, and having at least one carbon-carbon double bond in the cyclic structure thereof. Examples of the C 1 -C 1 a heterocycloalkenyl group include a 4,5-dihydro-1,2,3,4-oxatriazolyl group, a 2,3-dihydrofuranyl group, and a 2,3-dihydrothiophenyl group. The term “C 1 -C 10  heterocycloalkenylene group,” as used herein, refers to a divalent group having substantially 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 having a carbocyclic aromatic system of 6 to 60 carbon atoms, and the term “C 6 -C 60  arylene group,” as used herein, refers to a divalent group having a carbocyclic aromatic system of 6 to 60 carbon atoms. Examples of the C 6 -C 60  aryl group include a phenyl group, a pentalenyl group, a naphthyl group, an azulenyl group, an indacenyl group, an acenaphthyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a perylenyl group, a pentaphenyl group, a heptalenyl group, a naphthacenyl group, a picenyl group, a hexacenyl group, a pentacenyl group, a rubicenyl group, a coronenyl group, and an ovalenyl group. When the C 6 -C 60  aryl group and the C 6 -C 60  arylene group each include two or more rings, the rings may be condensed together with each other. 
     The term “C 1 -C 60  heteroaryl group,” as used herein, refers to a monovalent group having a heterocyclic aromatic system of 1 to 60 carbon atoms, further including, in addition to carbon atoms, at least one heteroatom, as ring-forming atoms. The term “C 1 -C 60  heteroarylene group,” as used herein, refers to a divalent group having a heterocyclic aromatic system of 1 to 60 carbon atoms, further including, in addition to carbon atoms, at least one heteroatom, as ring-forming atoms. Examples of the C 1 -C 60  heteroaryl group include a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, a benzoquinolinyl group, an isoquinolinyl group, a benzoisoquinolinyl group, a quinoxalinyl group, a benzoquinoxalinyl group, a quinazolinyl group, a benzoquinazolinyl group, a cinnolinyl group, a phenanthrolinyl group, a phthalazinyl group, and a naphthyridinyl group. When the C 1 -C 60  heteroaryl group and the C 1 -C 60  heteroarylene group each include two or more rings, the rings may be condensed together with each other. 
     The term “monovalent non-aromatic condensed polycyclic group,” as used herein, refers to a monovalent group (for example, having 8 to 60 carbon atoms) having two or more rings condensed to each other, only carbon atoms as ring-forming atoms, and no aromaticity in its entire molecular structure (e.g., is not aromatic when considered as a whole). Examples of the monovalent non-aromatic condensed polycyclic group include an indenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, an indenophenanthrenyl group, and an indeno anthracenyl group. The term “divalent non-aromatic condensed polycyclic group,” as used herein, refers to a divalent group having substantially the same structure as the monovalent non-aromatic condensed polycyclic group. 
     The term “monovalent non-aromatic condensed heteropolycyclic group,” as used herein, refers to a monovalent group (for example, having 1 to 60 carbon atoms) having two or more rings condensed to each other, further including, in addition to carbon atoms, at least one heteroatom, as ring-forming atoms, and having non-aromaticity in its entire molecular structure. Examples of the monovalent non-aromatic condensed heteropolycyclic group include a pyrrolyl group, a thiophenyl group, a furanyl group, an indolyl group, a benzoindolyl group, a naphtho indolyl group, an isoindolyl group, a benzoisoindolyl group, a naphthoisoindolyl group, a benzosilolyl group, a benzothiophenyl group, a benzofuranyl group, a carbazolyl group, a dibenzosilolyl group, a dibenzothiophenyl group, a dibenzofuranyl group, an azacarbazolyl group, an azafluorenyl group, an azadibenzosilolyl group, an azadibenzothiophenyl group, an azadibenzofuranyl group, a pyrazolyl group, an imidazolyl group, a triazolyl group, a tetrazolyl group, an oxazolyl group, an isoxazolyl group, a thiazolyl group, an isothiazolyl group, an oxadiazolyl group, a thiadiazolyl group, a benzopyrazolyl group, a benzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzoxadiazolyl group, a benzothiadiazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, an imidazotriazinyl group, an imidazopyrazinyl group, an imidazopyridazinyl group, an indenocarbazolyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, a benzoindolocarbazolyl group, a benzocarbazolyl group, a benzonaphthofuranyl group, a benzonaphthothiophenyl group, a benzonaphthosilolyl group, a benzofurodibenzofuranyl group, a benzofurodibenzothiophenyl group, and a benzothienodibenzothiophenyl group. The term “divalent non-aromatic condensed heteropolycyclic group,” as used herein, refers to a divalent group having substantially the same structure as the monovalent non-aromatic condensed heteropolycyclic group. 
     The term “C 6 -C 60  aryloxy group,” as used herein, refers to -OA 102  (wherein A 102  is the C 6 -C 60  aryl group), and the term “C 6 -C 60  arylthio group,” as used herein, refers to -SA 103  (wherein A 103  is the C 6 -C 60  aryl group). 
     The term “C 7 -C 60  aryl alkyl group,” as used herein, refers to -A 104 A 105  (where A 104  may be a C 1 -C 54  alkylene group, and A 105  may be a C 6 -C 59  aryl group), and the term “C 2 -C 60  heteroaryl alkyl group,” as used herein, refers to -A 106 A 107  (where A 106  may be a C 1 -C 59  alkylene group, and A 107  may be a C 1 -C 59  heteroaryl group). 
     The term “R 10a ,” as used herein, refers to: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 2 -C 60  heteroarylalkyl group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof; 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, or a C 2 -C 60  heteroarylalkyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro 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, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 2 -C 60  heteroarylalkyl group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 )(Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —P(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ). 
     Q 1  to Q 3 , Q 11  to Q 13 , Q 21  to Q 23 , and Q 31  to Q 33  used herein may each independently be: hydrogen; deuterium; —F; —Cl; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 1  alkyl group, a phenyl group, a biphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, or any combination thereof; a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a biphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, or any combination thereof; a C 7 -C 60  arylalkyl group; or a C 2 -C 60  heteroarylalkyl group. 
     The term “heteroatom,” as used herein, refers to any atom other than a carbon atom. Examples of the heteroatom include O, S, N, P, Si, B, Ge, Se, or any combination thereof. 
     The term “third-row transition metal,” as used herein, includes hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and the like. 
     “Ph,” as used herein, refers to a phenyl group, “Me,” as used herein, refers to a methyl group, “Et,” as used herein, refers to an ethyl group, “tert-Bu” or “Bu t ,” as used herein, refers to a tert-butyl group, and “OMe,” as used herein, refers to a methoxy group. 
     The term “biphenyl group,” as used herein, refers to “a phenyl group substituted with a phenyl group.” In other words, the “biphenyl group” is a substituted phenyl group having a C 6 -C 60  aryl group as a substituent. 
     The term “terphenyl group,” as used herein, refers to “a phenyl group substituted with a biphenyl group.” In other words, the “terphenyl group” is a substituted phenyl group having, as a substituent, a C 6 -C 60  aryl group substituted with a C 6 -C 60  aryl group. 
     * and *′, as used herein, unless defined otherwise, each refer to a binding site to a neighboring atom in a corresponding formula or moiety. 
     Hereinafter, compounds according to embodiments and light-emitting devices according to embodiments will be described in more detail with reference to the following synthesis examples and examples. The wording “B was used instead of A” used in describing Synthesis Examples means that an identical molar equivalent of B was used in place of A. 
     EXAMPLES 
     Synthesis Example 1. Synthesis of Compound 14 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 14-1 
     3-bromo-9H-carbazole (CAS No. 1592-95-6) and phenyl-d 5 -boronic acid (CAS No. 215527-70-1) were reacted in the presence of a Pd catalyst to obtain Intermediate 14-1. In relation to Intermediate 14-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 6 H 2 D 5 BO 2 : M+1 249.14 
     Synthesis of Intermediate 14-2 
     Intermediate 14-1, 1,3-dibromo-2-fluoro-5-nitrobenzene (CAS No. 361436-26-2), and potassium phosphate were reacted to obtain Intermediate 14-2. In relation to Intermediate 14-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 24 H 9 D 5 Br 2 N 2 O 2 : M+1 525.99 
     Synthesis of Intermediate 14-3 
     Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1) were reacted in the presence of a Pd catalyst to obtain Intermediate 14-3. In relation to Intermediate 14-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 36 H 9 D 15 N 2 O 2 : M+1 532.28 
     Synthesis of Intermediate 14-4 
     Intermediate 14-3, tin, and hydrochloric acid were reacted to obtain Intermediate 14-4. In relation to Intermediate 14-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 36 H 11 D 15 N 2 : M+1 502.31 
     Synthesis of Intermediate 14-5 
     Intermediate 14-4, hydrochloric acid, sodium nitrite, and potassium iodide were reacted to obtain Intermediate 14-5. In relation to Intermediate 14-5, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 36 H 9 D 15 IN: M+1 613.20 
     Synthesis of Compound 14 
     5 g of Intermediate 14-5 was dissolved in 40 mL of THF and maintained at −78° C. 4 mL of n-BuLi was added thereto, followed by stirring at −78° C. for 1 hour. 3.5 g of chlorotriphenylsilane (CAS No. 76-86-8) dissolved in 10 mL of THF was added dropwise to the reaction vessel, followed by stirring at room temperature for 24 hours. After the reaction was completed, the resultant reaction solution was extracted with ethylacetate, the collected organic layer was dried with magnesium sulfate and a solvent was evaporated therefrom. The obtained residue was separated and purified by silica gel column chromatography to obtain 4.2 g (yield: 70%) of Compound 14. Compound 14 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 2. Synthesis of Compound 43 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 43-1 
     Intermediate 43-1 was synthesized in substantially the same manner as Intermediate 14-2, except that 3,9′-bicarbazole (CAS No. 18628-07-4) was used instead of Intermediate 14-1. In relation to Intermediate 43-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 17 Br 2 N 3 O 2 : M+1 609.98 
     Synthesis of Intermediate 43-2 
     Intermediate 43-2 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 43-1 and phenylboronic acid (CAS No. 98-80-6) were respectively used instead of Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 43-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 27 N 3 O 2 : M+1 606.23 
     Synthesis of Intermediate 43-3 
     Intermediate 43-3 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 43-2 was used instead of Intermediate 14-3. In relation to Intermediate 43-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 29 N 3 : M+1 576.25 
     Synthesis of Intermediate 43-4 
     Intermediate 43-4 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 43-3 was used instead of Intermediate 14-4. In relation to Intermediate 43-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 17 Br 2 N 3 O 2 : M+1 687.12 
     Synthesis of Compound 43 
     Compound 43 was synthesized in substantially the same manner as Compound 14, except that Intermediate 43-4 was used instead of Intermediate 14-5. 3.6 g (yield: 77%) of Compound 43 was obtained. Compound 43 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 3. Synthesis of Compound 57 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 57-1 
     Intermediate 57-1 was synthesized in substantially the same manner as Intermediate 14-1, except that phenylboronic acid (CAS No. 98-80-6) was used instead of phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 57-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 18 H 13 N: M+1 244.11 
     Synthesis of Intermediate 57-2 
     3-bromo-9H-carbazole (CAS No. 1592-95-6), potassium hydroxide, and 4-toluenesulfonyl chloride were reacted to obtain Intermediate 57-2. In relation to Intermediate 57-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 19 H 14 BrNO 2 S: M+1 399.99 
     Synthesis of Intermediate 57-3 
     Intermediate 57-2 and Intermediate 57-1 were reacted in the presence of a Pd catalyst to obtain Intermediate 57-3. In relation to Intermediate 57-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 37 H 26 N 2 O 2 S: M+1 563.18 
     Synthesis of Intermediate 57-4 
     Intermediate 57-3 and sodium hydroxide were reacted to obtain Intermediate 57-4. In relation to Intermediate 57-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 20 N 2 : M+1 409.17 
     Synthesis of Intermediate 57-5 
     Intermediate 57-5 was synthesized in substantially the same manner as Intermediate 14-2, except that Intermediate 57-4 was used instead of Intermediate 14-1. In relation to Intermediate 57-5, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 36 H 21 Br 2 N 3 O 2 : M+1 686.00 
     Synthesis of Intermediate 57-6 
     Intermediate 57-6 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 57-5 and phenylboronic acid (CAS No. 98-80-6) were respectively used instead of Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 57-6, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 N 3 O 2 : M+1 682.22 
     Synthesis of Intermediate 57-7 
     Intermediate 57-7 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 57-6 was used instead of Intermediate 14-3. In relation to Intermediate 57-7, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 33 N 3 : M+1 652.26 
     Synthesis of Intermediate 57-8 
     Intermediate 57-8 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 57-7 was used instead of Intermediate 14-4. In relation to Intermediate 57-8, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 IN 2 : M+1 763.14 
     Synthesis of Compound 57 
     Compound 57 was synthesized in substantially the same manner as Compound 14, except that Intermediate 57-8 was used instead of Intermediate 14-5. 4.2 g (yield: 73%) of Compound 57 was obtained. Compound 57 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 4. Synthesis of Compound 86 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 86-1 
     (4-bromophenyl)triphenylsilane (CAS No. 18737-40-1) and bis(pinacolato)diboron were reacted in the presence of a Pd catalyst to obtain Intermediate 86-1. In relation to Intermediate 86-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 31 BO 2 Si: M+1 463.24 
     Synthesis of Intermediate 86-2 
     Intermediate 86-1 and 1-bromo-2-nitrobenzene (CAS No. 577-19-5) were reacted in the presence of a Pd catalyst to obtain Intermediate 86-2. In relation to Intermediate 86-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 23 NO 2 Si: M+1 458.03 
     Synthesis of Intermediate 86-3 
     Intermediate 86-2 and triphenylphosphine (CAS No. 603-35-0) were reacted to obtain Intermediate 86-3. In relation to Intermediate 86-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 23 NSi: M+1 426.26 
     Synthesis of Intermediate 86-4 
     Intermediate 86-4 was synthesized in substantially the same manner as Intermediate 57-3, except that Intermediate 86-3 was used instead of Intermediate 57-1. In relation to Intermediate 86-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 49 H 36 N 2 O 2 SSi: M+1 745.22 
     Synthesis of Intermediate 86-5 
     Intermediate 86-5 was synthesized in substantially the same manner as Intermediate 57-4, except that Intermediate 86-4 was used instead of Intermediate 57-3. In relation to Intermediate 86-5, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 30 N 2 Si: M+1 591.23 
     Synthesis of Intermediate 86-6 
     Intermediate 86-6 was synthesized in substantially the same manner as Intermediate 14-2, except that Intermediate 86-5 was used instead of Intermediate 14-1. In relation to Intermediate 86-6, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 Br 2 N 3 O 2 Si: M+1 868.05 
     Synthesis of Intermediate 86-7 
     Intermediate 86-7 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 86-6 and phenylboronic acid (CAS No. 98-80-6) were respectively used instead of Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 86-7, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 60 H 41 N 3 O 2 Si: M+1 864.31 
     Synthesis of Intermediate 86-8 
     Intermediate 86-8 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 86-7 was used instead of Intermediate 14-3. In relation to Intermediate 86-8, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 60 H 43 N 3 Si: M+1 834.33 
     Synthesis of Intermediate 86-9 
     Intermediate 86-9 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 86-8 was used instead of Intermediate 14-4. In relation to Intermediate 86-9, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 60 H 41 IN 2 Si: M+1 945.22 
     Synthesis of Compound 86 
     A reactant obtained by dissolving 3 g of 3-bromobiphenyl (CAS No. 2113-57-7) in 25 mL of diethyl ether was maintained at −78° C., and 5.5 mL of n-BuLi was added thereto, followed by stirring at −78° C. for 2 hours. The reactant was transferred to a reaction vessel containing dibromodiphenylsilane (CAS No. 4072-00-8) dissolved in 15 mL of diethyl ether, and maintained at −78° C. for 2 hours. 
     At the same time, 12 g of Intermediate 86-9 and 25 mL of THF were placed in another reaction vessel, and 5.5 mL of n-BuLi was added thereto, followed by stirring at −78° C. for 1 hour. Then, the two reactants were combined together and stirred at room temperature for 24 hours. After the reaction was completed, the resultant reaction solution was extracted with ethylacetate, the collected organic layer was dried with magnesium sulfate and a solvent was evaporated therefrom. The obtained residue was separated and purified by silica gel column chromatography to 8.3 g (yield: 56%) of Compound 86. Compound 86 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 5. Synthesis of Compound 106 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 106-1 
     Intermediate 106-1 was synthesized in substantially the same manner as Intermediate 14-2, except that 9-phenyl-9H, 9′H-3,3′-bicarbazole (CAS No. 1060735-14-9) was used instead of Intermediate 14-1. In relation to Intermediate 106-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 36 H 21 Br 2 N 3 O 2 : M+1 686.01 
     Synthesis of Intermediate 106-2 
     Intermediate 106-2 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 106-1 and phenylboronic acid (CAS No. 98-80-6) were respectively used instead of Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 106-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 N 3 O 2 : M+1 682.24 
     Synthesis of Intermediate 106-3 
     Intermediate 106-3 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 106-2 was used instead of Intermediate 14-3. In relation to Intermediate 106-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 33 N 3 : M+1 652.28 
     Synthesis of Intermediate 106-4 
     Intermediate 106-4 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 106-3 was used instead of Intermediate 14-4. In relation to Intermediate 106-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 IN 2 : M+1 763.16 
     Synthesis of Compound 106 
     Compound 106 was synthesized in substantially the same manner as Compound 14, except that Intermediate 106-4 was used instead of Intermediate 14-5. 4.1 g (yield: 71%) of Compound 106 was obtained. Compound 106 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 6. Synthesis of Compound 147 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 147-1 
     Intermediate 147-1 was synthesized in substantially the same manner as Intermediate 57-2, except that 4-bromo-9H-carbazole (CAS No. 3652-89-9) was used instead of 3-bromo-9H-carbazole (CAS No. 1592-95-6). In relation to Intermediate 147-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 19 H 14 BrNO 2 S: M+1 399.99 
     Synthesis of Intermediate 147-2 
     Intermediate 147-2 was synthesized in substantially the same manner as Intermediate 57-3, except that 9H-carbazole-1,2,3,4-d 4  (CAS No. 935425-39-1) was used instead of Intermediate 57-1. In relation to Intermediate 147-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 31 H 18 D 4 N 2 O 2 S: M+1 491.18 
     Synthesis of Intermediate 147-3 
     Intermediate 147-3 was synthesized in substantially the same manner as Intermediate 57-4, except that Intermediate 147-2 was used instead of Intermediate 57-3. In relation to Intermediate 147-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 24 H 12 D 4 N 2 : M+1 337.17 
     Synthesis of Intermediate 147-4 
     Intermediate 147-4 was synthesized in substantially the same manner as Intermediate 14-2, except that Intermediate 147-3 was used instead of Intermediate 14-1. In relation to Intermediate 147-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 13 D 4 Br 2 N 3 O 2 : M+1 613.99 
     Synthesis of Intermediate 147-5 
     Intermediate 147-5 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 147-4 was used instead of Intermediate 14-2. In relation to Intermediate 147-5, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 13 D 14 N 3 O 2 : M+1 620.31 
     Synthesis of Intermediate 147-6 
     Intermediate 147-6 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 147-5 was used instead of Intermediate 14-3. In relation to Intermediate 147-6, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 15 D 14 N 3 : M+1 590.33 
     Synthesis of Intermediate 147-7 
     Intermediate 147-7 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 147-6 was used instead of Intermediate 14-4. In relation to Intermediate 147-7, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 13 D 14 IN 2 : M+1 701.22 
     Synthesis of Compound 147 
     Compound 147 was synthesized in substantially the same manner as Compound 14, except that Intermediate 147-7 was used instead of Intermediate 14-5. 3.3 g (yield: 69%) of Compound 147 was obtained. Compound 147 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 7. Synthesis of Compound 186 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 186-1 
     Intermediate 186-1 was synthesized in substantially the same manner as Intermediate 57-3, except that 1-phenyl-9H-carbazole was used instead of Intermediate 57-1. In relation to Intermediate 186-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 37 H 26 N 2 O 2S : M+1 563.18 
     Synthesis of Intermediate 186-2 
     Intermediate 186-2 was synthesized in substantially the same manner as Intermediate 57-4, except that Intermediate 186-1 was used instead of Intermediate 57-3. In relation to Intermediate 186-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 20 N 2 : M+1 409.17 
     Synthesis of Intermediate 186-3 
     Intermediate 186-3 was synthesized in substantially the same manner as Intermediate 14-2, except that Intermediate 186-2 was used instead of Intermediate 14-1. In relation to Intermediate 186-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 36 H 21 Br 2 N 3 O 2 : M+1 686.00 
     Synthesis of Intermediate 186-4 
     Intermediate 186-4 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 186-3 and phenylboronic acid (CAS No. 98-80-6) were respectively used instead of Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 186-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 N 3 O 2 : M+1 682.24 
     Synthesis of Intermediate 186-5 
     Intermediate 186-5 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 186-4 was used instead of Intermediate 14-3. In relation to Intermediate 186-5, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 33 N 3 : M+1 652.27 
     Synthesis of Intermediate 186-6 
     Intermediate 186-6 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 186-5 was used instead of Intermediate 14-4. In relation to Intermediate 186-6, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 48 H 31 IN 2 : M+1 763.18 
     Synthesis of Compound 186 
     Compound 186 was synthesized in substantially the same manner as Compound 86, except that Intermediate 186-6 and 4-bromobiphenyl (CAS No. 92-66-0) were respectively used instead of Intermediate 86-9 and 3-bromobiphenyl (CAS No. 2113-57-7). 1.7 g (yield: 44%) of Compound 186 was obtained. Compound 186 was confirmed by LC-MS and  1 H-NMR. 
     Synthesis Example 8. Synthesis of Compound 297 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 297-1 
     Intermediate 297-1 was synthesized in substantially the same manner as Intermediate 14-1, except that dibenzofuran-2-boronic acid (CAS No. 402936-15-6) was used instead of phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 297-1, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 24 H 15 NO: M+1 334.14 
     Synthesis of Intermediate 297-2 
     Intermediate 297-2 was synthesized in substantially the same manner as Intermediate 14-2, except that Intermediate 297-1 was used instead of Intermediate 14-1. In relation to Intermediate 297-2, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 30 H 16 Br 2 N 2 O 3 : M+1 610.96 
     Synthesis of Intermediate 297-3 
     Intermediate 297-3 was synthesized in substantially the same manner as Intermediate 14-3, except that Intermediate 297-2 and phenylboronic acid (CAS No. 98-80-6) were respectively used instead of Intermediate 14-2 and phenyl-d 5 -boronic acid (CAS No. 215527-70-1). In relation to Intermediate 297-3, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 26 N 2 O 3 : M+1 607.20 
     Synthesis of Intermediate 297-4 
     Intermediate 297-4 was synthesized in substantially the same manner as Intermediate 14-4, except that Intermediate 297-3 was used instead of Intermediate 14-3. In relation to Intermediate 297-4, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 28 N 2 O: M+1 577.23 
     Synthesis of Intermediate 297-5 
     Intermediate 297-5 was synthesized in substantially the same manner as Intermediate 14-5, except that Intermediate 297-4 was used instead of Intermediate 14-4. In relation to Intermediate 297-5, the following M+1 peak value was confirmed by liquid chromatography mass spectrometry (LC-MS). 
     C 42 H 26 INO: M+1 688.12 
     Synthesis of Compound 297 
     Compound 297 was synthesized in substantially the same manner as Compound 86, except that Intermediate 297-5 and 5′-bromo-1,1′:3′1″-terphenyl were respectively used instead of Intermediate 86-9 and 3-bromobiphenyl (CAS No. 2113-57-7). 3.1 g (yield: 55%) of Compound 297 was obtained. Compound 297 was confirmed by LC-MS and  1 H-NMR. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Compound 
                   
                 MS/ 
                 FAB 
               
               
                 No. 
                   1 H NMR (CDCl 3 , 500 MHz) 
                 found 
                 calc. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 14 
                 8.55(d, 1H), 8.12(s, 2H), 7.99(d, 1H),  
                 745.32 
                 744.38 
               
               
                   
                 7.94(d, 1H), 7.89 (s, 1H), 7.77 (d, 1H),  
                   
                   
               
               
                   
                 7.40-7.33 (m, 16H), 7.16 (t, 1H) 
                   
                   
               
               
                 43 
                 8.55(d, 2H), 8.19(d, 1H), 8.12(s, 2H),  
                 819.35 
                 818.31 
               
               
                   
                 7.94(d, 2H), 7.72 (d, 1H), 7.67(s, 1H),  
                   
                   
               
               
                   
                 7.58(d, 1H), 7.50-7.35(m, 21H), 7.20- 
                   
                   
               
               
                   
                 7.16(m, 11H) 
                   
                   
               
               
                 57 
                 8.55(d, 2H), 8.12(s, 2H), 7.99(d, 1H),  
                 895.36 
                 894.34 
               
               
                   
                 7.94(d, 2H), 7.89 (s, 1H), 7.77(d, 1H),  
                   
                   
               
               
                   
                 7.75-7.67(m, 4H), 7.49-7.35(m, 23H),  
                   
                   
               
               
                   
                 7.20-7.15(m, 10H) 
                   
                   
               
               
                 86 
                 8.55(d, 2H), 8.22(d, 1H), 8.12(s, 2H),  
                 1153.41 
                 1152.43 
               
               
                   
                 7.94(d, 2H), 7.88(S, 1H), 7.72-7.56(m,  
                   
                   
               
               
                   
                 6H), 7.49-7.34(m, 36H), 7.19-7.16(m,  
                   
                   
               
               
                   
                 10H) 
                   
                   
               
               
                 106 
                 8.55(d, 1H), 8.30(d, 1H), 8.19(d, 1H),  
                 895.34 
                 894.34 
               
               
                   
                 8.13(d, 1H), 8.11 (s, 2H), 7.99(d, 1H),  
                   
                   
               
               
                   
                 7.94(d, 1H), 7.89(S, 2H), 7.77(d, 1H),  
                   
                   
               
               
                   
                 7.62-7.35(m, 25H), 7.20-7.16(m, 10H) 
                   
                   
               
               
                 147 
                 8.55(d, 2H), 8.12(s, 2H), 7.94(d, 2H),  
                 833.42 
                 832.40 
               
               
                   
                 7.54-7.30(m, 20H), 7.16(t, 2H) 
                   
                   
               
               
                 186 
                 8.55(d, 2H), 8.29(d, 1H), 8.12(s, 2H),  
                 971.40 
                 970.37 
               
               
                   
                 8.06(d, 1H), 7.94(d, 2H), 7.87(d, 2H),  
                   
                   
               
               
                   
                 7.75-7.65(m, 6H), 7.49-7.35(m, 20H),  
                   
                   
               
               
                   
                 7.19-7.15(m, 14H) 
                   
                   
               
               
                 297 
                 8.55(d, 1H), 8.12(s, 2H), 8.04(s, 1H),  
                 972.33 
                 971.36 
               
               
                   
                 7.98-7.75(m, 14H), 7.54-7.35(m, 22H),  
                   
                   
               
               
                   
                 7.19-7.16(m, 9H) 
               
               
                   
               
            
           
         
       
     
     Example 1 
     As an anode, a 15 0/cm 2  (1,200 Å) ITO glass substrate (product of Corning Inc.) was cut to a size of 50 mm×50 mm×0.7 mm, sonicated using isopropyl alcohol and pure water each for 5 minutes, and then cleaned by irradiation of ultraviolet rays and exposure of ozone thereto for 30 minutes. Then, the glass substrate was mounted on a vacuum deposition apparatus. 
     NPD was vacuum-deposited on the substrate to form a hole injection layer having a thickness of 300 Å, and then, mCP as a hole transport compound was vacuum-deposited thereon to form a hole transport layer having a thickness of 200 Å. 
     Compound 14 and Ir(pmp) 3  were co-deposited at a weight ratio of 92:8 on the hole transport layer to form an emission layer having a thickness of 250 Å. 
     TAZ was deposited on the emission layer to form an electron transport layer having a thickness of 200 Å, LiF was deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and an Al electrode was vacuum-deposited to a thickness of 100 Å to form a LiF/AI electrode, thereby completing the manufacture of an organic electroluminescent device. 
     
       
         
         
             
             
         
       
     
     Examples 2 to 8 and Comparative Examples 1 to 3 
     Organic electroluminescent devices were manufactured in substantially the same manner as in Example 1, except that, in forming an emission layer, the compounds shown in Table 2 were each used instead of Compound 14. 
     Evaluation Example 1 
     The characteristics of the organic electroluminescent devices according to Examples and Comparative Examples were evaluated by measuring the driving voltage at the current density of 10 mA/cm 2 , current density, and maximum quantum efficiency thereof. The driving voltage and current density of the organic electroluminescent devices were measured using a source meter (Keithley Instrument Inc., 2400 series), and the maximum quantum efficiency was measured using the external quantum efficiency measurement apparatus C9920-2-12 of Hamamatsu Photonics Inc. In evaluating the maximum quantum efficiency, the luminance/current density was measured using a luminance meter that was calibrated for wavelength sensitivity, and the maximum quantum efficiency was converted by assuming an angular luminance distribution (Lambertian) which introduced a perfect reflecting diffuser. Table 2 shows the evaluation results of the characteristics of the organic electroluminescent devices. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Driving 
                 Current 
                 Maximum 
                   
               
               
                   
                 Emission 
                 voltage 
                 density 
                 quantum 
                 Emission 
               
               
                   
                 layer 
                 (V) 
                 (mA/cm 2 ) 
                 efficiency (%) 
                 color 
               
               
                   
               
             
            
               
                 Example 1 
                 Compound 
                 4.2 
                 2.3 
                 25.4 
                 Blue 
               
               
                   
                  14 
                   
                   
                   
                   
               
               
                 Example 2 
                 Compound 
                 4.4 
                 2.3 
                 28.1 
                 Blue 
               
               
                   
                  43 
                   
                   
                   
                   
               
               
                 Example 3 
                 Compound 
                 4.4 
                 2.3 
                 27.3 
                 Blue 
               
               
                   
                  57 
                   
                   
                   
                   
               
               
                 Example 4 
                 Compound 
                 4.5 
                 2.3 
                 27.6 
                 Blue 
               
               
                   
                  86 
                   
                   
                   
                   
               
               
                 Example 5 
                 Compound 
                 4.5 
                 2.3 
                 27.2 
                 Blue 
               
               
                   
                 106 
                   
                   
                   
                   
               
               
                 Example 6 
                 Compound 
                 4.2 
                 2.3 
                 27.3 
                 Blue 
               
               
                   
                 147 
                   
                   
                   
                   
               
               
                 Example 7 
                 Compound 
                 4.7 
                 2.3 
                 26.9 
                 Blue 
               
               
                   
                 186 
                   
                   
                   
                   
               
               
                 Example 8 
                 Compound 
                 4.8 
                 2.3 
                 25.8 
                 Blue 
               
               
                   
                 297 
                   
                   
                   
                   
               
               
                 Comparative 
                 mCP 
                 5.4 
                 2.3 
                 21.7 
                 Blue 
               
               
                 Example 1 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 CE1 
                 5.3 
                 2.3 
                 21.5 
                 Blue 
               
               
                 Example 2 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 CE2 
                 5.6 
                 2.3 
                 22.6 
                 Blue 
               
               
                 Example 3 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                   
                     
                     
                         
                         
                     
                   
                 
               
            
           
         
       
     
     From Table 2, it can be seen that the organic electroluminescent devices according to Examples 1 to 8 had characteristics of a low driving voltage and high efficiency, as compared with the organic electroluminescent devices according to Comparative Examples 1 to 3. 
     As described above, according to one or more embodiments, the inclusion of a heterocyclic compound represented by Formula 1 may enable the manufacture of a light-emitting device having a low driving voltage and high efficiency and a high-quality electronic apparatus including the light-emitting device. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims, and equivalents thereof.