Patent Publication Number: US-2023140120-A1

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

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0132684, filed on Oct. 6, 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 heterocyclic compound, a light-emitting device including the same, and an electronic apparatus including the light-emitting device. 
     2. Description of the Related Art 
     From among light-emitting devices, self-emissive devices have wide viewing angles, high contrast ratios, short response times, and excellent characteristics in terms of luminance, driving voltage, and response speed. 
     In a light-emitting device, a first electrode is located on a substrate, and a hole transport region, an emission layer, an electron transport region, and a second electrode are sequentially arranged 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. These excitons transition from an excited state to a ground state to thereby generate light. 
     SUMMARY 
     One or more embodiments include a heterocyclic compound, a light-emitting device including the same, and an electronic apparatus including the light-emitting device. 
     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, a light-emitting device includes 
     a first electrode, 
     a second electrode facing the first electrode, 
     an interlayer located between the first electrode and the second electrode and comprising an emission layer, and 
     a heterocyclic compound represented by Formula 1. 
     
       
         
         
             
             
         
       
     
     In Formula 1, 
     Moiety A may be a group represented by Formula 2, 
     Moiety B may be a group represented by Formula 3, 
     n may be an integer from 1 to 3, and 
     m may be an integer from 1 to 4, 
     wherein, in Formula 2, 
     Y 5  may be C(R 5a )(R 5b ), Si(R 5a )(R 5b ), O, S, or N(R 5a ), 
     Y 6  may be C(R 6a )(R 6b ), Si(R 6a )(R 6b ), O, S, or N(R 6a ), 
     ring CY1 to ring CY4 may each be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, 
     T 1  may be * or —(L 1 ) b1 —(R 1 ) c1 , 
     T 2  may be * or —(L 2 ) b2 —(R 2 ) c2 , 
     T 3  may be * or —(L 3 ) b3 —(R 3 ) c3 , 
     T 4  may be * or —(L 4 ) b4 —(R 4 ) c4 , 
     at least one of T 1  to T 4  may be *, and 
     a1 to a4 may be an integer from 0 to 10, 
     wherein, in Formula 3, 
     X 11  may be C(R 11 ), Si(R 11 ), or N, 
     X 12  may be C(R 12 ), Si(R 12 ), or N, 
     X 13  may be C(R 13 ), Si(R 13 ), or N, 
     T 14  may be *′ or —(L 14 ) b14 —(R 14 ) c14 , 
     T 15  may be *′ or —(L 15 ) b15 —(R 15 ) c15 , 
     T 16  may be *′ or —(L 16 ) b16 —(R 16 ) c16 , and 
     at least one of T 14  to T 16  may be *′, 
     wherein, in Formulae 1 to 3, 
     L 1  to L 4  and L 14  to L 16  may each independently be a single bond, a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , 
     b1 to b4 and b14 to b16 may be an integer from 0 to 3, 
     R 1  to R 4 , R 5a , R 5b , R 6a , R 6b , R 11  to R 16  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 , a C 7 -C 60  aryl alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  heteroaryl alkyl 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 ), 
     c1 to c4 and c14 to c16 may each independently be an integer from 0 to 10, 
     * indicates a binding site to moiety B, 
     *′ indicates a binding site to moiety A, and 
     R 10a  may be 
     deuterium (-D), —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  aryl alkyl group, a C 2 -C 60  heteroaryl alkyl 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 6  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, or a C 2 -C 60  heteroaryl alkyl 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  aryl alkyl group, a C 2 -C 60  heteroaryl alkyl 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 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ), 
     wherein Q 1  to Q 3 , Q 11  to Q 13 , Q 21  to Q 23  and Q 31  to Q 33  are each independently: 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, a C 1 -C 60  alkoxy group, a C 3 -C 60  carbocyclic group or a C 1 -C 6  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 6  alkoxy group, a phenyl group, a biphenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or any combination thereof; a C 7 -C 60  aryl alkyl group; or a C 2 -C 60  heteroaryl alkyl group. 
     One or more embodiments include an electronic apparatus including the light-emitting device. 
    
    
     
       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    shows a schematic cross-sectional view of a light-emitting device according to an embodiment; 
         FIG.  2    shows a schematic cross-sectional view of an electronic apparatus according to an embodiment; and 
         FIG.  3    shows a schematic cross-sectional 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 disclosure. 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 and 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 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, 
     Moiety A may be a group represented by Formula 2, and 
     Moiety B may be a group represented by Formula 3. 
     In relation to Formula 1, n may be an integer from 1 to 3, and m may be an integer from 1 to 4. For example, n is an integer of 2 or more, two or more moiety A may each be bonded as a substituent for moiety B. For example, m is an integer of 2 or more, two or more moiety B may each be bonded as a substituent for moiety A. For example, in relation to Formula 1, n may be 1 and m may be an integer from 1 to 4. In relation to Formula 1, n may be an integer from 1 to 3, and m may be 1. 
     In an embodiment, in relation to Formula 1, n may be an integer from 1 to 3, and m may be 1 or 2. For example, in relation to Formula 1, n may be 1, and m may be 1 or 2. In relation to Formula 1, n may be an integer from 1 to 3, and m may be 1. 
     In an embodiment, Formula 1 may be represented by any one of Formulae 1-1 to 1-6: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 1-1 to 1-6, 
     moiety A and moiety B are the same as described above. 
     In an embodiment, Formula 1 may be represented by any one of Formulae 1-1 to 1-4. 
     In relation to Formula 2, Y 5  may be C(R 5a )(R 5b ), Si(R 5a )(R 5b ), O, S, or N(R 5a ), and Y 6  may be C(R 6a )(R 6b ), Si(R 6a )(R 6b ), O, S, or N(R 6a ). 
     In an embodiment, in relation to Formula 2, Y 5  may be O or S, and Y 6  may be O or S. 
     In an embodiment, Y 5  and Y 6  in Formula 2 may be different from each other. 
     In an embodiment, Y 5  and Y 6  in Formula 2 may be identical to each other. 
     In one or more embodiments, Y 5  and Y 6  in Formula 2 may each be oxygen (O). 
     Ring CY1 to ring CY4 may be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group. 
     In relation to Formula 2, T 1  may be * or —(L 1 ) b1 —(R 1 ) c1 , T 2  may be * or —(L 2 ) b2 -(R 2 ) c2 , T 3  may be * or —(L 3 ) b3 —(R 3 ) c3 , T 4  may be * or —(L 4 ) b4 —(R 4 ) c4 , at least one of T 1  to T 4  may be *, and * may be a binding site to B. 
     In an embodiment, T 1  may be * or —(L 1 ) b1 —(R 1 ) c1 , T 2  may be * or —(L 2 ) b2 —(R 2 ) c2 , T 3  may be * or —(L 3 ) b3 —(R 3 ) c3 , T 4  may be * or —(L 4 ) b4 —(R 4 ) c4 , at least one of T 2  and T 3  may be *, and * may be a binding site to B. 
     a1 to a4 in Formula 2 may be an integer from 0 to 10. a1 to a4 indicate the numbers of T 1  to T 4 , respectively. For example, if a1 is the integer of 2 or more, two or more of T 1  may be identical to or different from each other. If a2 is an integer of 2 or greater, at least two of T 2 (s) may be identical to or different from each other. If a3 is an integer of 2 or greater, at least two of T 3 (s) may be identical to or different from each other. If a4 is an integer of 2 or greater, at least two of T 4 (s) may be identical to or different from each other. 
     In an embodiment, a1 to a4 in Formula 2 may be an integer from 0 to 4. 
     In an embodiment, ring CY1 to ring CY4 may each independently be a benzene group, a naphthalene group, a carbazole group, a dibenzofuran group, a fluorene group, a dibenzothiophene group, or a dibenzosilole group. 
     In an embodiment, ring CY1 to ring CY4 in Formula 2 may be different from each other. 
     In one or more embodiments, ring CY1 to ring CY4 in Formula 2 may be identical to each other. 
     In one or more embodiments, in relation to Formula 2, ring CY1 to ring CY4 may each be a benzene group, and a1 to a4 may each be an integer from 0 to 4. 
     In one or more embodiments, Formula 2 may be represented by Formula 2-1: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 2-1, 
     CY1, CY3, CY4, T 1 , T 3 , T 4 , a1, a3, a4, Y 5 , and Y 6  are the same as described in the present disclosure, and 
     T 21  to T 24  are the same as described in connection with T 2 , and at least one of T 21  to T 24  may be *, and * indicates a binding site to B. 
     In one or more embodiments, at least one of T 22  and T 23  in Formula 2-1 is * and * indicates a binding site to B. 
     In an embodiment, Formula 2 is represented by Formula 2-2, and satisfies Condition 2-1 or Condition 2-2. 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 2-2, 
     CY1, CY4, T 1 , T 4 , a1, a4, Y 5 , and Y 6  are the same as described in the present disclosure, 
     T 21  to T 24  are the same as described in connection with T 2 , and 
     T 31  to T 34  are the same as described in connection with T 3 , 
     Condition 2-1 
     At least one of T 21  to T 24  is *, and * indicates a binding site to B. 
     Condition 2-2 
     At least one of T 21  to T 24  is *, and at least one of T 31  to T 34  is *, and two or more * in Formula 2-2 respectively indicate binding sites to B(s). 
     In an embodiment, Formula 2 is represented by Formula 2-2, and satisfies Condition 2-3 or Condition 2-4. 
     Condition 2-3 
     At least one of T 22  and T 23  is * and * indicates a binding site to B. 
     Condition 2-4 
     At least one of T 22  and T 23  is *, and at least one of T 32  and T 33  is *, and two or more * in Formula 2-2 respectively indicate binding sites to B(s). 
     In relation to Formula 3, X 11  may be C(R 11 ), Si(R 11 ), or N, X 12  may be C(R 12 ), Si(R 12 ), or N, and X 13  may be C(R 13 ), Si(R 13 ), or N. 
     In an embodiment, in relation to Formula 3, X 11  may be C(R 11 ) or N, X 12  may be C(R 12 ) or N, and X 13  may be C(R 13 ) or N. 
     In an embodiment, Formula 3 may satisfy any one of Conditions 3-1 to 3-4: 
     Condition 3-1 
     X 11  may be N, X 12  may be N, and X 13  may be N. 
     Condition 3-2 
     X 11  may be C(R 11 ), X 12  may be N, and X 13  may be N. 
     Condition 3-3 
     X 11  may be C(R 11 ), X 12  may be C(R 12 ), and X 13  may be N. 
     Condition 3-4 
     X 11  may be C(R 11 ), X 12  may be C(R 12 ), and X 13  may be C(R 13 ). 
     In an embodiment, Formula 3 may satisfy any one of Conditions 3-1 to Condition 3-3. 
     In relation to Formula 3, T 14  may be *′ or —(L 14 ) b14 —(R 14 ) c14 , T 15  may be *′ or —(L 15 ) b15 —(R 15 ) c15 , T 16  may be *′ or —(L 16 ) b16 —(R 16 ) c16 , and at least one of T 14  to T 16  may be *′. 
     In an embodiment, Formula 3 may be represented by one of Formula 3-1 to Formula 3-3: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 3-1 to 3-3, 
     X 11  to X 13 , T 14 , T 15 , and *′ are the same as described in the present application, 
     two or more *′ in Formula 3-2 and Formula 3-3 respectively indicate binding sites to A(s). 
     L 1  to L 4  and L 14  to L 16  in Formulae 1 to 3 may each independently be a single bond, a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a , or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a , and b1 to b4 and b14 to b16 may each be an integer from 0 to 3. b1 to b4 and b14 to b16 may indicate numbers of L 1  to L 4  and L 14  to L 16 , respectively. 
     For example, if b1 is the integer of 2 or more, two or more of L 1  may be identical to or different from each other. For example, if b2 is the integer of 2 or more, two or more of L 2  may be identical to or different from each other. For example, if b3 is the integer of 2 or more, two or more of L 3  may be identical to or different from each other. For example, if b4 is the integer of 2 or more, two or more of L 4  may be identical to or different from each other. For example, if b14 is the integer of 2 or more, two or more of L 14  may be identical to or different from each other. For example, if b15 is the integer of 2 or more, two or more of L 15  may be identical to or different from each other. For example, if b16 is the integer of 2 or more, two or more of L 16  may be identical to or different from each other. 
     In an embodiment, in Formulae 1 to 3, 
     L 1  to L 4  and L 14  to L 16  may each independently be: a single bond; or 
     a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, a spiro-anthracenefluorenylene group, a phenanthrolinylene group, an azulenylene group, a heptalenylene group, an indacenylene group, an acenaphthylene group, a fluorenylene group, a spiro-bifluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, a pentaphenylene group, a hexacenylene group, a pentacenylene group, a rubicenylene group, a coronenylene group, an ovalenylene group, a thiophenylene group, a furanylene group, a carbazolylene group, an indolylene group, an isoindolylene group, a benzofuranylene group, a benzothiophenylene group, a dibenzofuranylene group, a dibenzothiophenylene group, a benzocarbazolylene group, a dibenzocarbazolylene group, a dibenzosilolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a benzoisoquinolinylene group, a dibenzoquinolinylene group, a dibenzoisoquinolinylene group, a biphenylene group, a phenylpyridinylene group, a phenanthrolinylene group, a dibenzoquinoline group, a bipyridinylene group, or a pyridinylene group; or a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, a spiro-anthracenefluorenylene group, a phenanthrolinylene group, an azulenylene group, a heptalenylene group, an indacenylene group, an acenaphthylene group, a fluorenylene group, a spiro-bifluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, a pentaphenylene group, a hexacenylene group, a pentacenylene group, a rubicenylene group, a coronenylene group, an ovalenylene group, a thiophenylene group, a furanylene group, a carbazolylene group, an indolylene group, an isoindolylene group, a benzofuranylene group, a benzothiophenylene group, a dibenzofuranylene group, a dibenzothiophenylene group, a benzocarbazolylene group, a dibenzocarbazolylene group, a dibenzosilolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a benzoisoquinolinylene group, a dibenzoquinolinylene group, a dibenzoisoquinolinylene group, a biphenylene group, a phenylpyridinylene group, a phenanthrolene group, a bipyridinylene group, a dibenzoquinoline group, or a pyridinylene group, each unsubstituted or substituted with 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 cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a biphenyl group, a terphenyl group, a pentalenyl group, an indenyl group, a naphthyl group, a spiro-anthracenefluorenylene group, a phenanthrolinylene group, an azulenyl group, a heptalenyl group, an indacenyl group, an acenaphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a naphthacenyl group, a picenyl group, a perylenyl group, a pentaphenyl group, a hexacenyl group, a pentacenyl group, a rubicenyl group, a coronenyl group, an ovalenyl group, a thiophenyl group, a furanyl group, a carbazolyl group, an indolyl group, an isoindolyl group, a benzofuranyl group, a benzothiophenyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, a dibenzosilolyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a benzoisoquinolinyl group, a dibenzoquinolinyl group, a dibenzoisoquinolinyl group, a biphenyl group, a phenylpyridinyl group, a phenanthronyl group, a dibenzoquinolinyl group, bipyridinyl group, a pyridinyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), —P(═O)(Q 31 )(Q 32 ), or any combination thereof. 
     In one or more embodiments, in Formulae 1 to 3, 
     L 1  to L 4  and L 14  to L 16  may each independently be: a single bond; or 
     a phenylene group, a naphthylene group, a spiro-anthracenefluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, a thiophenylene group, a furanylene group, a carbazolylene group, a benzofuranylene group, a benzothiophenylene group, a dibenzofuranylene group, a dibenzothiophenylene group, a benzocarbazolylene group, a dibenzocarbazolylene group, a dibenzosilolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a benzoisoquinolinylene group, a dibenzoquinolinylene group, a dibenzoisoquinolinylene group, a biphenylene group, a phenylpyridinylene group, a phenanthrolinylene group, a dibenzoquinoline group, a bipyridinylene group or a pyridinylene group; and a phenylene group, a naphthylene group, a spiro-anthracenefluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, a thiophenylene group, a furanylene group, a carbazolylene group, a benzofuranylene group, a benzothiophenylene group, a dibenzofuranylene group, a dibenzothiophenylene group, a benzocarbazolylene group, a dibenzocarbazolylene group, a dibenzosilolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a benzoisoquinolinylene group, a dibenzoquinolinylene group, a dibenzoisoquinolinylene group, a biphenylene group, a phenylpyridinylene group, a phenanthrolinylene group, a dibenzoquinoline group, a bipyridinylene group, or a pyridinylene group, each unsubstituted or substituted with 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 cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a spiro-anthracenefluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a naphthacenyl group, a picenyl group, a perylenyl group, a thiophenyl group, a furanyl group, a carbazolyl group, a benzofuranyl group, a benzothiophenyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, a dibenzosilolyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a benzoisoquinolinyl group, a dibenzoquinolinyl group, a dibenzoisoquinolinyl group, a biphenyl group, a phenylpyridinyl group, a phenanthrolinyl group, a dibenzoquinoline group, a bipyridinyl group, a pyridinyl group, or any combination thereof. 
     In one or more embodiments, in relation to Formulae 1 to 3, 
     L 1  to L 4  and L 14  to L 16  may each independently be: a single bond; or 
     a phenylene group, a naphthylene group; and a phenylene group or a naphthylene group, each unsubstituted or substituted with 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 cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, or any combination thereof. 
     In one or more embodiments, L 1  to L 4  and L 14  to L 16  may each independently be a single bond; or a group represented by one of Formulae 4-1 to 4-9. 
     
       
         
         
             
             
         
       
     
     * and *′ in Formulae 4-1 to 4-9 each indicate a binding site to a neighboring atom. 
     In Formulae 1 to 3, 
     R 1  to R 4 , R 5a , R 5b , R 6a , R 6b , R 11  to R 16  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 , a C 7 -C 60  aryl alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  heteroaryl alkyl 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 c1 to c4 and c14 to c16 may each independently be an integer from 0 to 10. 
     c1 to c4 and c14 to c16 indicate numbers of R 1  to R 4  and R 14  to R 16 , respectively. If c1 is an integer of 2 or greater, at least two of R 1 (s) may be identical to or different from each other. If c2 is an integer of 2 or greater, at least two of R 2 (s) may be identical to or different from each other. If c3 is an integer of 2 or greater, at least two of R 3 (s) may be identical to or different from each other. When c4 is an integer of 2 or greater, at least two of R 4 (s) may be identical to or different from each other. If c14 is an integer of 2 or greater, at least two of R 14 (s) may be identical to or different from each other. If c15 is an integer of 2 or greater, at least two of R 15 (s) may be identical to or different from each other. If c16 is an integer of 2 or greater, at least two of R 16 (s) may be identical to or different from each other. 
     In an embodiment, c1 to c4 and c14 to c16 may each independently be an integer from 0 to 4. 
     In an embodiment, in Formulae 1 to 3, 
     R 1  to R 4 , R 5a , R 5b , R 6a , R 6b , and R 11  to R 16  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, —CD 3 , 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 20  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a tert-butyl group, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or any combination thereof; 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a biphenyl group, a terphenyl group, a C 1 -C 20  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 indenyl 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 benzosilolyl 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 dibenzosilolyl group, a benzofluorenyl group, a benzocarbazolyl group, a naphthobenzofuranyl group, a naphthobenzothiophenyl group, a naphthobenzosilolyl group, a dibenzofluorenyl group, a dibenzocarbazolyl group, a dinaphthofuranyl group, a dinaphthothiophenyl group, a dinaphthosilolyl group, an indenocarbazolyl group, an indolocarbazolyl group, a benzofuranocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, an azafluorenyl group, an azacarbazolyl group, an azadibenzofuranyl group, an azadibenzothiophenyl 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 tert-butyl group, a phenyl group, a biphenyl group, a terphenyl group, a C 1 -C 20  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 indenyl 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 benzosilolyl 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 dibenzosilolyl group, a benzofluorenyl group, a benzocarbazolyl group, a naphthobenzofuranyl group, a naphthobenzothiophenyl group, a naphthobenzosilolyl group, a dibenzofluorenyl group, a dibenzocarbazolyl group, a dinaphthofuranyl group, a dinaphthothiophenyl group, a dinaphthosilolyl group, an indenocarbazolyl group, an indolocarbazolyl group, a benzofuranocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(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 ), 
     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 CD3, —CH 2 CD2H, —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 iso-propyl 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, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with deuterium, a cyano group, —CD 3 , a tert-butyl group, a C 1 -C 20  alkyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, or any combination thereof. 
     In one or more embodiments, in Formulae 1 to 3, 
     R 1  to R 4 , R 5a , R 5b , R 6a , R 6b , and R 11  to R 16  may each independently be hydrogen, deuterium, —F, a cyano group, —CD 3 , 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, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a cyano 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 tert-butyl group, a phenyl group, a biphenyl group, a terphenyl group, a C 1 -C 20  alkylphenyl group, a naphthyl group, a tetrahydronaphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a thiophenyl group, a furanyl group, an indenyl group, an isoindolyl group, an indolyl group, a carbazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzosilolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzofluorenyl group, a benzocarbazolyl group, a naphthobenzofuranyl group, a naphthobenzothiophenyl group, a naphthobenzosilolyl group, a dibenzofluorenyl group, a dibenzocarbazolyl group, a dinaphthofuranyl group, a dinaphthothiophenyl group, a dinaphthosilolyl group, an indeno carbazolyl group, an indolocarbazolyl group, a benzofuranocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, or a triazinyl group, unsubstituted or substituted with deuterium, —F, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a cyano 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 tert-butyl group, a phenyl group, a biphenyl group, a terphenyl group, a C 1 -C 20  alkylphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a thiophenyl group, a furanyl group, an indenyl group, an isoindolyl group, an indolyl group, a carbazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzosilolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzofluorenyl group, a benzocarbazolyl group, a naphthobenzofuranyl group, a naphthobenzothiophenyl group, a naphthobenzosilolyl group, a dibenzofluorenyl group, a dibenzocarbazolyl group, a dinaphthofuranyl group, a dinaphthothiophenyl group, a dinaphthosilolyl group, an indeno carbazolyl group, an indolocarbazolyl group, a benzofuranocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a triazinyl group, or any combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ), 
     Q 1  to Q 3  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 iso-propyl 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, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with deuterium, a cyano group, a tert-butyl group, a C 1 -C 20  alkyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group or any combination thereof. 
     In one or more embodiments, in relation to Formulae 1 to 3, 
     R 1  to R 4 , R 5a , R 5b , R 6a , R 6b , and R 11  to R 16  may each independently be: hydrogen, deuterium, —F, a tert-butyl group, or a cyano group; 
     a phenyl group, a biphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with deuterium, —F, a tert-butyl group, a cyano group, a C 1 -C 20  alkyl group, a phenyl group, a biphenyl group, a naphthyl group, a C 1 -C 20  alkylphenyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, or any combination thereof; or 
     —Si(Q 1 )(Q 2 )(Q 3 ), 
     Q 1  to Q 3  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 iso-propyl 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, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, or a dibenzothiophenyl group, each unsubstituted or substituted with deuterium, a cyano group, a tert-butyl group, a C 1 -C 20  alkyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, a triazinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group or any combination thereof. 
     In an embodiment, the heterocyclic compound represented by Formula 1 may be any one selected from Compounds 1 to 56: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The light-emitting device may include the heterocyclic compound represented by Formula 1. 
     Although not intended to be limited by any particular mechanism or theory, the light-emitting device as described above may include the heterocyclic compound represented by Formula 1. 
     For example, the heterocyclic compound represented by Formula 1 can easily implement high triplet energy due to a steric hindrance effect, due to the inclusion of bipolar groups with enhanced electron transport characteristics. Accordingly, the heterocyclic compound represented by Formula 1 can be easily applied to an emission layer or an electron transport region in a blue phosphorescent and thermally activated delayed fluorescence (TADF) device. 
     Thus, an electronic device, e.g., a light-emitting device, including the heterocyclic compound represented by Formula 1 may have a low driving voltage, improved (increased) luminance, improved (increased) luminescence efficiency, and/or improved (increased) lifespan. 
     Synthesis methods of the heterocyclic compound represented by Formula 1 should be apparent to one of ordinary skill in the art by referring to Synthesis Examples and/or Examples provided below. 
     At least one heterocyclic compound represented by Formula 1 may be utilized in a light-emitting device (for example, an organic light-emitting device). Thus, provided is a light-emitting device including: a first electrode; a second electrode facing the first electrode; an interlayer located between the first electrode and the second electrode and including an emission layer; and the heterocyclic compound represented by Formula 1. 
     In some embodiments, 
     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. 
     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 of, for example, about 400 nm to about 490 nm. 
     For example, the emission layer may include the heterocyclic compound represented by Formula 1. 
     For example, the emission layer contains a host and dopant, and the heterocyclic compound represented by Formula 1 may be a host. 
     According to an embodiment, the heterocyclic compound represented by Formula 1 may be included in the electron transport region. 
     For example, the heterocyclic compound represented by Formula 1 may be included in the buffer layer. 
     In an embodiment, the emission layer may include a host other than the heterocyclic compound represented by Formula 1. 
     For example, the dopant may include a phosphorescent dopant, a fluorescent dopant, a delayed fluorescence material, or any combination thereof, which will be further described herein below. 
     In an embodiment, the emission layer may further include a phosphorescent dopant, delayed fluorescence material or any combination thereof. For example, the emission layer may include a phosphorescent dopant in addition to a host and a dopant. 
     In some embodiments, 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 (which may also be referred to as a coordinate covalent bond or a dative bond). In some embodiments, at least one of the ligand(s) in the number of m may be a carbene ligand (e.g., Ir(pmp) 3  and/or the like). The transition metal may be, for example, iridium, platinum, osmium, palladium, rhodium, or gold. The emission layer and the dopant may be the same as described in the present disclosure. 
     
       
         
         
             
             
         
       
     
     In an embodiment, the light-emitting device may include a capping layer located outside the first electrode or outside the second electrode. For example, the heterocyclic compound represented by Formula 1 may be included in the capping layer. 
     In one or more embodiments, the light-emitting device may further include at least one of a first capping layer located outside a first electrode and a second capping layer located outside a 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 for the first capping layer and/or second capping layer are the same as described in the present disclosure. 
     The expression that an “(interlayer and/or a capping layer) includes a heterocyclic compound” as used herein may be construed as meaning that the “(interlayer and/or the capping layer) may include one heterocyclic compound represented by Formula 1 or two or more different heterocyclic compounds represented by Formula 1”. 
     For example, the interlayer and/or capping layer may include the heterocyclic compound represented by Formula 1. 
     In one or more embodiments, the heterocyclic compound represented by Formula 1 may be included in the interlayer. 
     The term “interlayer” as used herein refers to a single layer and/or all of a plurality of layers located between the first electrode and the second electrode of the light-emitting device. 
     Another aspect of an embodiment 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, wherein the first electrode of the light-emitting device may be electrically connected to the source electrode or the drain electrode. In an embodiment, the electronic apparatus may further include a color filter, a color conversion layer, a touch screen layer, a polarizing layer, or any combination thereof. For more details on the electronic apparatus, related descriptions provided herein may be referred to. 
     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  includes 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 located under the first electrode  110  or on the second electrode  150 . As the substrate, a glass substrate and/or a plastic substrate may be utilized. 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 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. If 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, if 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 located on the first electrode  110 . The interlayer  130  may include an emission layer. 
     The interlayer  130  may further include a hole transport region located between the first electrode  110  and the emission layer, and an electron transport region located 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. 
     In one or more embodiments of the present disclosure, 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 located between the two or more emitting units. If 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 and/or the like) unsubstituted or substituted with at least one R 10a  (for example, Compound HT16), 
     R 2O3  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. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY201 to CY217, R 10b  and R 10c  may each be the same as described with respect to R 10a , ring CY 201  to ring CY 204  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 above. 
     In an embodiment, ring CY 201  to ring CY 204  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 the groups represented by Formulae CY201 to CY203 and at least one of the groups represented by Formulae CY204 to CY217. 
     In one or more embodiments, in Formula 201, xa1 may be 1, R 201  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 the 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 HT50, m-MTDATA, TDATA, 2-TNATA, NPB(NPD), β-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), CzSi(9-(4-tert-Butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole), 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. If 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. If the thicknesses of the hole transport region, the hole injection layer, and the hole transport layer are within these ranges, satisfactory (suitable) 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 an emission layer, and the electron-blocking layer may block (reduce) the leakage of electrons from an emission layer to a 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 these materials, a charge-generation material for the improvement of 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 one or more embodiments, the p-dopant may include a quinone derivative, a cyano group-containing compound, a compound including element EL1 and element EL2, or any combination thereof. 
     Examples of the quinone derivative are TCNQ, F4-TCNQ, etc. 
     Examples of the cyano group-containing compound are HAT-CN, and a compound represented by Formula 221 below. 
     
       
         
         
             
             
         
       
     
     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 including element EL1 and element EL2, element EL1 may be metal, metalloid, or any combination thereof, and element EL2 may be non-metal, metalloid, or any combination thereof. 
     Examples of the metal are 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.); 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.); post-transition metal (for example, zinc (Zn), indium (In), tin (Sn), etc.); and 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 are silicon (Si), antimony (Sb), and tellurium (Te). 
     Examples of the non-metal are oxygen (O) and halogen (for example, F, Cl, Br, I, etc.). 
     Examples of the compound including element EL1 and element EL2 are 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 are 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.), rhenium oxide (for example, ReO 3 , etc.), or any combination thereof. 
     Examples of the metal halide are alkali metal halide, alkaline earth metal halide, transition metal halide, post-transition metal halide, lanthanide metal halide, or any combination thereof. 
     Examples of the alkali metal halide are LiF, NaF, KF, RbF, CsF, LiCI, NaCl, KCl, RbCI, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, Lil, NaI, KI, RbI, CsI, or any combination thereof. 
     Examples of the alkaline earth metal halide are BeF 2 , MgF 2 , CaF 2 , SrF 2 , BaF 2 , BeCl 2 , MgCl 2 , CaCl 2 ), SrCl 2 , BaCI 2 , BeBr 2 , MgBr 2 , CaBr 2 , SrBr 2 , BaBr 2 , Be 12 , Mg 12 , CaI 2 , Sr 12 , BaI 2 , or any combination thereof. 
     Examples of the transition metal halide are titanium halide (for example, TiF 4 , TiCl 4 , TiBr 4 , TiI 4 , etc.), zirconium halide (for example, ZrF 4 , ZrC 14 , ZrBr 4 , ZrI 4 , etc.), hafnium halide (for example, HfF 4 , HfC 14 , HfBr 4 , Hfl 4 , etc.), vanadium halide (for example, VF 3 , VCl 3 , VBr 3 , V 13 , etc.), niobium halide (for example, NbF 3 , NbC 13 , NbBr 3 , NbI 3 , etc.), tantalum halide (for example, TaF 3 , TaCI 3 , TaBr 3 , TaI 3 , etc.), chromium halide (for example, CrF 3 , CrC 13 , CrBr 3 , Cr 13 , etc.), molybdenum halide (for example, MoF 3 , MoCI 3 , MoBr 3 , MoI 3 , etc.), tungsten halide (for example, WF 3 , WCl3, WBr 3 , WI 3 , etc.), manganese halide (for example, MnF 2 , MnCl 2 , MnBr 2 , Mn 12 , etc.), technetium halide (for example, TcF 2 , TcCl 2 , TcBr 2 , TcI 2 , etc.), rhenium halide (for example, ReF 2 , ReCl 2 , ReBr 2 , Re 12 , etc.), iron halide (for example, FeF 2 , FeCl 2 , FeBr 2 , FeI 2 , etc.), ruthenium halide (for example, RuF 2 , RuCl 2 , RuBr 2 , Rul 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 , CO 12 , etc.), rhodium halide (for example, RhF 2 , RhCl 2 , RhBr 2 , Rhl 2 , etc.), iridium halide (for example, IrF 2 , IrCl 2 , IrBr 2 , Ir 12 , etc.), nickel halide (for example, NiF 2 , NiCl 2 , NiBr 2 , Nil 2 , etc.), palladium halide (for example, PdF 2 , PdCI 2 , PdBr 2 , Pd 12 , 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, AgCI, AgBr, AgI, etc.), gold halide (for example, AuF, AuCI, AuBr, AuI, etc.), or any combination thereof. 
     Examples of the post-transition metal halide are zinc halide (for example, ZnF 2 , ZnCl 2 , ZnBr 2 , ZnI 2 , etc.), indium halide (for example, Inlk, etc.), tin halide (for example, SnI 2 , etc.), or any combination thereof. 
     Examples of the lanthanide metal halide are 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 , SmI 3 , or any combination thereof. 
     An example of the metalloid halide is antimony halide (for example, SbCI5, etc.). 
     Examples of the metal telluride are 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.), lanthanide metal telluride (for example, LaTe, CeTe, PrTe, NdTe, PmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, etc.), or any combination thereof. 
     Emission Layer in Interlayer  130   
     If 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 of the present disclosure, 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 each other or are separated from each other to emit white light. In one or more embodiments of the present disclosure, 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 with each other in a single layer to emit white light. For example, the emission layer may emit blue light. 
     In an embodiment, the emission layer may include the heterocyclic compound represented by Formula 1. 
     For example, the emission layer contains a host and dopant, and the heterocyclic compound represented by Formula 1 may be a host. For example, the emission layer includes a host and a dopant, and may include a host other than the heterocyclic compound represented by Formula 1. 
     In an embodiment, the dopant may include a phosphorescent dopant, a fluorescent dopant, a delayed fluorescence material, or a combination thereof. 
     The phosphorescent dopant or the fluorescent dopant that may be included in the emission layer may be understood by referring to the descriptions of the phosphorescent dopant or the fluorescent dopant provided herein. 
     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 act 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. If the thickness of the emission layer is within these ranges, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Host 
     The host may include the heterocyclic compound represented by Formula 1. The host may further include, in addition to the heterocyclic compound represented by Formula 1, a carbazole-containing compound, an anthracene-containing compound, a triazine-containing compound, or any combination thereof. The host may further include, for example, a carbazole-containing compound and a triazine-containing compound. 
     In one or more embodiments, the host may further 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 each the same as described herein with respect to Q 1 . 
     For example, if 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 other embodiments, the host may further include a compound represented by Formula 301-1, a compound represented by Formula 301-2, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     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  may each be the same as described herein, 
     L 302  to L 304  may each independently be the same as described herein with respect to with L 301 , 
     xb2 to xb4 may each independently be the same as described herein with respect to xb1, and 
     R 302  to R 305  and R 311  to R 314  may each be the same as described herein with respect to 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 some embodiments, the host may include at least one of Compounds H1 to H131, 9,10-di(2-naphthyl)anthracene (DNA), 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 
     In one or more embodiments, 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 if xc1 is two 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, and if 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═*′, 
     X 403  and X 404  may each independently be a chemical bond (for example, a covalent bond or a coordination bond), O, S, N(Q 413 ), B(Q 413 ), P(Q 413 ), C(C 413 )(C 414 ), or Si(Q 413 )(Q 414 ), 
     Q 411  to Q 414  may each be the same as described herein with respect to 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  may each be the same as described herein with respect to 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, if xc1 in Formula 402 is 2 or more, two ring A 401  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  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  may each be the same as described herein with respect to 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) group, an isonitrile group, —CN group, a phosphorus-containing 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 PD25, 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 disclosure, the delayed fluorescence material may be selected from compounds capable of emitting delayed fluorescent light based on a delayed fluorescence emission mechanism. 
     The delayed fluorescence material further included in the emission layer may act as a host or a dopant, depending on the kind of other materials included in the emission layer. 
     In one or more embodiments, 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. If 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 the following 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 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 less, 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 Group II-VI semiconductor compounds, Group III-V semiconductor compounds, Group III-VI semiconductor compounds, Group I-III-VI semiconductor compounds, Group IV-VI semiconductor compounds, a Group IV element or compound, or any combination thereof. 
     Examples of the Group II-VI semiconductor compound are 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, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InAlP, InNAs, InNSb, InPAs, or InPSb; a quaternary compound such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GalnNSb, GaInPAs, GalnPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, or InAlPSb; or any combination thereof. The Group III-V semiconductor compound may further include a Group II element. Examples of the Groups III-V semiconductor compound further including a Group II element are InZnP, InGaZnP, InAlZnP, etc. 
     Examples of the Group III-VI semiconductor compound are: a binary compound, such as GaS, GaSe, Ga 2 Se 3 , GaTe, InS, InSe, In 2 S 3 , In 2 Se 3 , or InTe; a ternary compound, such as InGaS 3 , or InGaSe 3 ; and any combination thereof. 
     Examples of the Group I-III-VI semiconductor compound are: a ternary compound, such as AgInS, AgInS 2 , CulnS, CuInS 2 , CuGaO 2 , AgGaO 2 , or AgAlO 2 ; or any combination thereof. 
     Examples of the Group IV-VI semiconductor compound are: 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 (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 (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 be an oxide of metal, metalloid, or non-metal, a semiconductor compound, and any combination thereof. Examples of the oxide of metal, metalloid, or non-metal are 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 ; and any combination thereof. Examples of the semiconductor compound are, as described herein, Group II-VI semiconductor compounds; Group III-V semiconductor compounds; Group III-VI semiconductor compounds; Group I-III-VI semiconductor compounds; Group IV-VI semiconductor compounds; and 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, AlP, AISb, or any combination thereof. 
     A full width at half maximum (FWHM) of the 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 (increased). 
     In addition, the quantum dot may be in the form of a spherical particle, a pyramidal particle, a multi-arm particle, a cubic nanoparticle, a nanotube particle, a nanowire particle, a nanofiber particle, and/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 the combination of 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-transporting region may include a buffer layer, a hole-blocking layer, an electron control layer, an electron-transporting 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. 
     In an embodiment, 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. 
     In an embodiment, the electron transport region may include the heterocyclic compound represented by Formula 1. 
     In an embodiment, the electron transport region may further include a compound represented by Formula 601 in addition to the heterocyclic compound represented by Formula 1. 
     For example, the buffer layer may include the heterocyclic compound represented by Formula 1. 
       [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  may each be the same as described herein with respect to Q 1 , 
     xe21 may be 1, 2, 3, 4, or 5, 
     at least one of Ar 601 , L 601 , and R 601  may each independently be a π electron-deficient nitrogen-containing C 1 -C 60  cyclic group unsubstituted or substituted with at least one R 10a . 
     For example, if 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 other embodiments, Ar 601  in Formula 601 may be a substituted or unsubstituted anthracene group. 
     In one or more embodiments, the electron transport region may further 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  may each be the same as described herein with respect to L 601 , 
     xe611 to xe613 may each be the same as described herein with respect to xe1, 
     R 611  to R 613  may each be the same as described herein with respect to 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 further 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 , BAIq, TAZ, NTAZ, TSPO1, TPBI, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the electron transport region may be from about 100 Å to about 5,000 Å, for example, about 160 Å to about 4,000 Å. If the electron transport region includes a buffer layer, a hole-blocking layer, an electron control layer, an electron transport layer, or any combination thereof, the thickness of the buffer layer, the hole-blocking layer, or the electron control layer may each independently be from about 20 Å to about 1000 Å, for example, about 30 Å to about 300 Å, and the thickness of the electron transport layer may be from about 100 Å to about 1000 Å, for example, about 150 Å to about 500 Å. if the thickness of the buffer layer, the hole-blocking layer, the electron control layer, the electron transport layer, and/or the electron transport layer are within these ranges, satisfactory (suitable) 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. The metal ion of an alkali metal complex may be a Li ion, a Na ion, a K ion, a Rb ion, or a Cs ion, and the metal ion of an 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 a hydroxyquinoline, a hydroxyisoquinoline, a hydroxybenzoquinoline, a hydroxyacridine, a hydroxyphenanthridine, a hydroxyphenyloxazole, a hydroxyphenylthiazole, a hydroxyphenyloxadiazole, a hydroxyphenylthiadiazole, a hydroxyphenylpyridine, a hydroxyphenylbenzimidazole, a hydroxyphenylbenzothiazole, a bipyridine, a phenanthroline, a 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 directly contact 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, alkaline earth metal, a rare earth metal, an alkali metal-containing compound, 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, a 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 be 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, Lil, 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), BaxCai-xO (wherein x is a real number satisfying the condition of 0&lt;x&lt;1), and/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 are 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 , Lu 2 Te 3 , or any combination thereof. 
     The alkali metal complex, the alkaline earth-metal complex, and the rare earth metal complex may include i) one of metal ions of the alkali metal, the alkaline earth metal, and the rare earth metal and ii), 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 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 one or more embodiments, the electron injection layer may consist of: i) an alkali metal-containing compound (for example, an alkali metal halide); or 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. 
     If the electron injection layer further includes an organic material, alkali metal, alkaline earth metal, rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, alkali metal complex, alkaline earth-metal complex, 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. If the thickness of the electron injection layer is within the ranges described above, satisfactory (suitable) electron injection characteristics may be obtained without a substantial increase in driving voltage. 
     Second Electrode  150   
     The second electrode  150  may be located on the interlayer  130  having a structure as described above. The second electrode  150  may be a cathode, which is an electron injection electrode, and as the 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 utilized. 
     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 located outside the first electrode  110 , and/or a second capping layer may be located outside the second electrode  150 . In particular, 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 the 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 the 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 the 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 emission efficiency according to the principle of constructive interference. Accordingly, the light extraction efficiency of the light-emitting device  10  is increased, so that the luminescence efficiency of the light-emitting device  10  may be improved (increased). 
     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). 
     Each of the first capping layer and the second capping layer may include the heterocyclic compound represented by Formula 1. 
     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 carbocyclic compounds, heterocyclic compounds, amine group-containing compounds, porphyrin derivatives, phthalocyanine derivatives, naphthalocyanine derivatives, alkali metal complexes, alkaline earth metal complexes, or any combination thereof. Optionally, the carbocyclic compound, the heterocyclic compound, and the amine group-containing compound may be substituted with a substituent including O, N, S, Se, Si, F, Cl, Br, I, or any combination thereof. In one or more embodiments, 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 and 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 an embodiment, at least one of the first capping layer and the second capping layer may each independently include one of Compounds HT28 to HT33, one of Compounds CP1 to CP6, β-NPB, P4, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     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 located in at least one traveling direction of light emitted from the light-emitting device. For example, the light emitted from the light-emitting device may be blue light or white light. For more details on the light-emitting device, related description provided above may be referred to. In one or more embodiments, 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 located 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 located among the color filter areas, and the color conversion layer may further include a plurality of color conversion areas and light-shielding patterns located among the color conversion areas. 
     The plurality of color filter areas (or the plurality of color conversion areas) may include a first area emitting first color light, a second area emitting second color light, and/or a third area emitting 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 some embodiments, 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. For more details on the quantum dot, related descriptions provided herein may be referred to. The first area, the second area, and/or the third area may each include a scatterer. 
     For example, the light-emitting device may emit first light, the first area may absorb the first light to emit first-first color light, the second area may absorb the first light to emit second-first color light, and the third area may absorb the first light to emit 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 some embodiments, 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, an organic semiconductor, an 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 located between the color conversion layer and/or color filter and the light-emitting device. The sealing portion allows light from the light-emitting device to be extracted to the outside, and concurrently (e.g., simultaneously) prevents (reduces) ambient air and moisture from penetrating 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. If the sealing portion is a thin film encapsulation layer, the electronic apparatus may be flexible. 
     Various suitable functional layers may be additionally located 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/or 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, or endoscope displays), fish finders, various suitable 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 showing a light-emitting apparatus according to an embodiment of the present disclosure. 
     The electronic apparatus  180  of  FIG.  2    includes a substrate  100 , a thin-film transistor (TFT)  200 , 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 located on the substrate  100 . The buffer layer  210  may prevent (reduce) penetration of impurities through the substrate  100  and may provide a flat surface on the substrate  100 . 
     A TFT  200  may be located on the buffer layer  210 . The TFT  200  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 located on the active layer  220 , and the gate electrode  240  may be located on the gate insulating film  230 . 
     An interlayer insulating film  250  may be located on the gate electrode  240 . The interlayer insulating film  250  may be located between the gate electrode  240  and the source electrode  260  and between the gate electrode  240  and the drain electrode  270 , to insulate from one another. 
     The source electrode  260  and the drain electrode  270  may be located 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 located in contact with the exposed portions of the source region and the drain region of the active layer  220 . 
     The TFT  200  is electrically connected to a light-emitting device to drive the light-emitting device, and is covered and protected by a passivation layer  280 . The passivation layer  280  may include an inorganic insulating film, an organic insulating film, or any 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 located on the passivation layer  280 . The passivation layer  280  may be located to expose a portion of the drain electrode  270 , not fully covering the drain electrode  270 , and the first electrode  110  may be located to be connected to the exposed portion of the drain electrode  270 . 
     A pixel defining layer  290  including an insulating material may be located on the first electrode  110 . The pixel defining layer  290  may expose a certain region of the first electrode  110 , and an interlayer  130  may be formed in the exposed region of the first electrode  110 . The pixel defining layer  290  may be a polyimide and/or polyacrylic organic film. At least some layers of the interlayer  130  may extend beyond the upper portion of the pixel defining layer  290  to be located in the form of a common layer. 
     The second electrode  150  may be located 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 located on the capping layer  170 . The encapsulation portion  300  may be located 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 any combination of the inorganic films and the organic films. 
       FIG.  3    shows a cross-sectional view showing a light-emitting apparatus according to an embodiment of the present disclosure. 
     The electronic apparatus  190  of  FIG.  3    is the same as the electronic apparatus  180  of  FIG.  2   , except that a light-shielding pattern  500  and a functional region  400  are additionally located 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 electronic apparatus  190  of  FIG.  3    may be a tandem light-emitting device. 
     Manufacturing Method 
     The layers included in the hole transport region, the emission layer, and the layers included in the electron transport region may be formed in a certain region by using various suitable methods such as vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) deposition, ink-jet printing, laser-printing, laser-induced thermal imaging, and/or the like. 
     If layers constituting the hole transport region, an 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 three to sixty carbon atoms, and the term “C 1 -C 60  heterocyclic group” as used herein refers to a cyclic group that has one to sixty 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 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 three to sixty 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 one to sixty carbon atoms and includes *—N═*′ as a ring-forming moiety. 
     For example, 
     the C 3 -C 60  carbocyclic group may be i) group T 1  or ii) a condensed cyclic group in which two or more groups T 1  are condensed 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 T 2 , ii) a condensed cyclic group in which two or more groups T 2  are condensed with each other, or iii) a condensed cyclic group in which at least one group T 2  and at least one group T 1  are condensed 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 π electron-rich C 3 -C 60  cyclic group may be i) group T 1 , ii) a condensed cyclic group in which two or more groups T 1  are condensed with each other, iii) group T 3 , iv) a condensed cyclic group in which two or more groups T 3  are condensed with each other, or v) a condensed cyclic group in which at least one group T 3  and at least one group T 1  are condensed 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 groups T4 are condensed with each other, iii) a condensed cyclic group in which at least one group T4 and at least one group T1 are condensed with each other, iv) a condensed cyclic group in which at least one group T4 and at least one group T3 are condensed 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 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 T 3  may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, or a borole group, and 
     group T 4  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 terms “the cyclic group, the C 3 -C 60  carbocyclic group, the C 1 -C 60  heterocyclic group, the π electron-rich C 3 -C 60  cyclic group, or the π electron-deficient nitrogen-containing C 1 -C 60  cyclic group” as used herein refer 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.) according to the structure of a formula for which the corresponding term is used. For example, the “benzene group” may be a benzo group, a phenyl group, a phenylene group, and/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 6  heterocyclic group are 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. Examples of the divalent C 3 -C 60  carbocyclic group and the divalent C 1 -C 6  heterocyclic group are 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 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 specific examples thereof are 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 the same structure as the C 1 -C 6  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 in the middle or at the terminus of the C 2 -C 60  alkyl group, and examples thereof are an ethenyl group, a propenyl group, and a butenyl group. The term “C 2 -C 60  alkenylene group” as used herein refers to a divalent group having the same structure as the C 2 -C 60  alkenyl group. 
     The term “C 2 -C 60  alkynyl group” as used herein refers to a monovalent hydrocarbon group having at least one carbon-carbon triple bond in the middle or at 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 6  alkynylene group” as used herein refers to a divalent group having the same structure as the C 2 -C 60  alkynyl group. 
     The term “C 1 -C 60  alkoxy group” as used herein refers to a monovalent group represented by —OA 101  (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 are 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 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 10  cycloalkylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkyl group. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent cyclic group of 1 to 10 carbon atoms, further including, in addition to carbon atoms, at least one heteroatom, as ring-forming atoms, and specific examples are a 1,2,3,4-oxatriazolidinyl group, a tetrahydrofuranyl group, and a tetrahydrothiophenyl group. The term “C 1 -C 10  heterocycloalkylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkyl group. 
     The term “C 3 -C 10  cycloalkenyl group” as used herein refers to a monovalent cyclic group that has three to ten carbon atoms and at least one carbon-carbon double bond in the ring thereof and no aromaticity, and specific examples thereof are a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. The term “C 3 -C 10  cycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkenyl group. 
     The term “C 1 -C 10  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 10  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 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 are 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. if 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 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 are 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. If the C 1 -C 6  heteroaryl group and the C 1 -C 60  heteroarylene group each include two or more rings, the rings may be condensed 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. Examples of the monovalent non-aromatic condensed polycyclic group are an indenyl group, a fluorenyl 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 the same structure as the monovalent non-aromatic condensed polycyclic group described above. 
     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 the same structure as the monovalent non-aromatic condensed heteropolycyclic group described above. 
     The term “C 6 -C 60  aryloxy group” as used herein indicates —OA 102  (wherein A 102  is a C 6 -C 60  aryl group), and the term “C 6 -C 60  arylthio group” as used herein indicates —SA 103  (wherein A 103  is a 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 (-D), —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  aryl alkyl group, a C 2 -C 60  heteroaryl alkyl 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 6  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, or a C 2 -C 60  heteroaryl alkyl 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  aryl alkyl group, a C 2 -C 60  heteroaryl alkyl 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 ), —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  as 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, a C 1 -C 60  alkoxy group, 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 carbazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or any combination thereof; a C 7 -C 60  aryl alkyl group; or a C 2 -C 60  heteroaryl alkyl group. 
     The term “heteroatom” as used herein refers to any atom other than a carbon atom. Examples of the heteroatom are O, S, N, P, Si, B, Ge, Se, and any combinations 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/or 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, “ter-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 of Compound 1 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 1-1 
     20 g of 2,2′-Oxybis(bromobenzene) (CAS=51452-87-0) was dissolved in 200 mL of diethyl ether solvent and then stirred at a temperature of −78° C. After stabilization, 48.78 mL of 2.5 M n-BuLi was slowly added dropwise thereto. After 1 hour, 7 mL of SiCl 4  was dissolved in 30 mL of diethyl ether solvent and slowly added dropwise thereto at −78° C. to form reaction solution  1 . 
     22 g of 2-Bromo-1-(2-bromophenoxy)-4-chlorobenzene (CAS=1674380-83-6) was dissolved in tetrahydrofuran (THF), and at a temperature of −78° C., stirred. Once stabilized, 48.78 mL of 2.5 M n-BuLi was slowly added dropwise thereto to form reaction solution  2 . After 1 hour, reaction solution  1  was added to reaction solution  2  at −78° C. using a cannula and reacted at room temperature for 8 hours. After the reaction was completed, the resultant organic layer was extracted and dried. After separation and purification of the residue by column chromatography, 12.16 g (yield of 50%) of Intermediate 1-1 was obtained. Intermediate 1-1 was confirmed by MS/FAB. (C24H15ClO2Si: M+1 398.92) 
     Synthesis of Intermediate 1-2 
     12.16 g of Intermediate 1-1, 7.74 g of bis(pinacolato)diboron, 4.49 g of KoAc, and 1.07 g of Pd(PPh 3 ) 2 Cl 2  were dissolved in 200 mL of toluene solvent, and then stirred at a temperature of 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residual was subjected to separation and purification by column chromatography to obtain 11.06 g (yield of 74%) of Intermediate 1-2. Intermediate 1-2 was confirmed by MS/FAB. (C 30 H 27 BO 4 Si: M+1 490.44) 
     Synthesis of Compound 1 
     2 g of 2-Chloro-4,6-diphenyl-1,3,5-triazine (CAS=3842-55-5), 3.67 g of Intermediate 1-2, 7.47 mL of 2 M K 2 CO 3 , and 0.43 g of Pd(PPh 3 ) 4  were dissolved in 40 mL of toluene/ethanol (4:1) solvent, and then stirred at a temperature of 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residue was separated and purified by column chromatography, followed by recrystallization and sublimation purification to obtain 4.07 g (yield of 81%) of Compound 1 with high purity. Compound 1 was identified by MS/FAB and  1 H-NMR. 
     Synthesis Example of Compound 2 
     
       
         
         
             
             
         
       
     
     Synthesis of Compound 2 
     2 g of 9-(4-chloro-6-phenyl-1,3,5-triazin-2-yl)-9H-carbazole (CAS=1268244-56-9), 2.75 g of Intermediate 1-2, 5.61 mL of 2 M K 2 CO 3 , and 0.32 g of Pd(PPh 3 ) 4  were dissolved in 40 mL of toluene/ethanol (4:1) solvent, and then stirred at a temperature of 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residue was separated and purified by column chromatography, followed by recrystallization and sublimation purification to obtain 3.15 g (yield of 82%) of Compound 2 with high purity. Compound 2 was confirmed by MS/FAB and  1 H-NMR. 
     Synthesis Example of Compound 3 
     
       
         
         
             
             
         
       
     
     Synthesis of Compound 3 
     2 g of 9,9′-(6-chloro-1,3,5-triazine-2,4-diyl)bis(9H-carbazole) (CAS=877615-05-9), 2.2 g of Intermediate 1-2, 4.49 mL of 2 M K 2 CO 3 , and 0.3 g of Pd(PPh 3 ) 4  were dissolved in 40 mL of toluene/ethanol (4:1) solvent, and then stirred at a temperature of 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residue was separated and purified by column chromatography, followed by recrystallization and sublimation purification to obtain 2.95 g (yield of 82%) of Compound 3 with high purity. Compound 3 was confirmed by MS/FAB and  1 H-NMR. 
     Synthesis Example of Compound 7 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 7-1 
     10 g of 2-Bromo-1-(2-bromophenoxy)-4-chlorobenzene (CAS=1674380-83-6) was dissolved in 150 mL of diethyl ether solvent, and then, stirred at a temperature of −78° C. After stabilization, 22.07 mL of 2.5 M n-BuLi was slowly added dropwise thereto. After 1 hour, 3.17 mL of SiCl 4  was dissolved in 15 mL of diethyl ether solvent and slowly added dropwise thereto at −78° C. to form reaction solution  1 . 
     10 g of 2-Bromo-1-(2-bromophenoxy)-4-chlorobenzene (CAS=1674380-83-6) was dissolved in 150 mL of THF solvent and 22.07 mL of 2.5 M n-BuLi was slowly added dropwise thereto while stirring at a temperature of −78° C. to form reaction solution  2 . After 1 hour, reaction solution  1  was added to reaction solution  2  at −78° C. using a cannula. The reaction was carried out at room temperature for 8 hours. After the reaction was completed, the resultant organic layer was extracted and dried. After separation and purification of the residue by column chromatography, 5.38 g (yield of 45%) of Intermediate 7-1 was obtained. Intermediate 7-1 was confirmed by MS/FAB. (C 24 H 14 Cl 2 O 2 Si: M+1 433.36) 
     Synthesis of Intermediate 7-2 
     5.38 g of Intermediate 7-1, 3.15 g of bis(pinacolato)diboron, 1.83 g of KoAc, and 0.43 g of Pd(PPh 3 ) 2 Cl 2  were dissolved in 60 mL toluene solvent and stirred at 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residual was subjected to separation and purification by column chromatography to obtain 5.74 g (yield of 75%) of Intermediate 7-2. Intermediate 7-2 was confirmed by MS/FAB. (C 36 H 38 B 2 O 6 Si: M+1 616.4) 
     Synthesis of Compound 7 
     2 g of 2-Chloro-4,6-diphenyl-1,3,5-triazine (CAS=3842-55-5), 9.2 g of Intermediate 7-2, 11.21 mL of 2 M K 2 CO 3 , and 0.43 of Pd(PPh 3 ) 4  were dissolved in 60 mL of toluene/ethanol (4:1) solvent, and then stirred at a temperature of 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residue was separated and purified by column chromatography, followed by recrystallization and sublimation purification to obtain 4.7 g (yield of 76%) of Compound 7 with high purity. Compound 7 was confirmed by MS/FAB and  1 H-NMR. 
     Synthesis Example of Compound 27 
     
       
         
         
             
             
         
       
     
     Synthesis of Compound 27 
     2 g of 9,9′-(6-chloropyrimidine-2,4-diyl)bis(9H-carbazole) (CAS=604786-70-1), 2.2 g of Intermediate 1-2, 4.5 mL of 2 M K 2 CO 3 , and 0.26 got Pd(PPh 3 ) 4  were dissolved in 40 mL of toluene/ethanol (4:1) solvent, and then, stirred at a temperature of 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residue was separated and purified by column chromatography, followed by recrystallization and sublimation purification to obtain 3.02 g (yield of 87%) of Compound 27 with high purity. Compound 27 was confirmed by MS/FAB and  1 H-NMR. 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 31-1 
     2 g of 4-Chloro-2,6-diphenylpyrimidine (CAS=29509-91-9), 4.62 g of Intermediate 7-2, 0.43 g of Pd(PPh 3 ) 4 , 5.62 mL of 2 M K 2 CO 3 , and 50 mg of Pd(PPh 3 ) 4  were dissolved in 60 mL of toluene/ethanol (4:1) solvent, and then, stirred at a temperature of 110° C. for 12 hours. The residual was subjected to separation and purification by column chromatography to obtain 1.89 g (yield of 30%) of Intermediate 31-1. Intermediate 31-1 was confirmed by MS/FAB. (C 46 H 37 BN 2 O 4 Si: M+1 720.26) 
     Synthesis of Compound 31 
     1.89 g of Intermediate 31-1, 0.7 g of 2-chloro-4,6-diphenyl-1,3,5-triazine (CAS=3842-55-5), 1.96 mL of 2 M K 2 CO 3 , and 93 mg of Pd(PPh 3 ) 4  were dissolved in 60 mL of toluene/ethanol (4:1) solvent, followed by stirring at 110° C. for 12 hours. After the reaction was completed, the resultant reaction solution was extracted and the obtained organic layer was dried. The residue was separated and purified by column chromatography, followed by recrystallization and sublimation purification to obtain 1.99 g (yield of 90%) of Compound 31 with high purity. Compound 31 was confirmed by MS/FAB and  1 H-NMR. 
       1 H NMR and MS/FAB of the compounds synthesized according to 6 Synthesis Examples above are shown in Table 1. Synthesis methods for compounds other than the compounds shown in Table 1 may be easily recognized by those skilled in the technical field by referring to the synthesis paths and source material materials described above. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Com- 
                   
                 MS/FAB 
               
            
           
           
               
               
               
               
            
               
                 pound 
                 H NMR (δ) 
                 Calc 
                 found 
               
               
                   
               
               
                  1 
                 8.36(d, 4H), 8.14(d, 1H), 7.84(s, 1H),  
                 595.17 
                 595.73 
               
               
                   
                 7.50(m, 6H), 7.45(m, 3H), 7.42(m, 3H),  
                   
                   
               
               
                   
                 7.29(d, 1H), 7.09-7.10(m, 6H) 
                   
                   
               
               
                  2 
                 8.55(d, 1H), 8.36(d, 2H), 8.14-8.19(m,  
                 684.20 
                 684.83 
               
               
                   
                 2H), 7.94(d, 1H), 7.84(s, 1H), 7.58(d,  
                   
                   
               
               
                   
                 1H), 7.50(m, 4H), 7.42-7.45(m, 6H),  
                   
                   
               
               
                   
                 7.35(t, 1H), 7.09-7.29 (m, 9H) 
                   
                   
               
               
                  3 
                 8.55(d, 2H), 8.19(m, 2H), 8.14(d, 1H),  
                 773.22 
                 773.93 
               
               
                   
                 7.94(d, 2H), 7.84(s, 1H), 7.58(d, 2H),  
                   
                   
               
               
                   
                 7.45-7.50(m, 7H), 7.35(d, 2H), 7.29(d,  
                   
                   
               
               
                   
                 1H), 7.09-7.26(m, 11H) 
                   
                   
               
               
                  7 
                 8.36(d, 8H), 8.14(d, 2H), 7.84(d, 2H),  
                 826.25 
                 826.99 
               
               
                   
                 7.50(m, 14H), 7.45(m, 4H), 7.09-  
                   
                   
               
               
                   
                 7.10(m, 4H) 
                   
                   
               
               
                 27 
                 8.55(d, 2H), 8.19(d, 2H), 7.94(d, 2H),  
                 772.23 
                 772.94 
               
               
                   
                 7.84(s, 1H), 7.50-7.61 (m, 6H), 7.42-  
                   
                   
               
               
                   
                 7.45(m, 11H), 7.14-7.29(m, 5H),  
                   
                   
               
               
                   
                 7.09-7.10(m, 3H) 
                   
                   
               
               
                 31 
                 8.35-8.36(m, 6H), 8.23(s, 1H), 8.14(d,  
                 825.26 
                 826.00 
               
               
                   
                 1H), 7.94(d, 2H), 7.84(d, 2H), 7.42- 
                   
                   
               
               
                   
                 7.61 (m, 17H), 7.29(d, 2H), 7.09- 
                   
                   
               
               
                   
                 7.10(m, 4H) 
               
               
                   
               
            
           
         
       
     
     Example 1 
     As an anode, a glass substrate (product of Corning Inc.) with a 15 Ω/cm 2  (1,200 Å) ITO electrode formed thereon 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 resultant glass substrate was mounted on a vacuum deposition apparatus. 
     NPD(NPB) was deposited on the anode to form a hole injection layer having a thickness of 300 Å, TCTA was deposited on the hole injection layer to form a hole transport layer having a thickness of 200 Å, and CzSi was deposited on the hole transport layer to form an emission auxiliary layer having a thickness of 100 Å. 
     Compound 1 (host) and Ir (pmp) 3  (dopant) were co-deposited on the emission auxiliary layer at a weight ratio of 92:8 to form an emission layer with a thickness of 250 Å. 
     TSPO1 was deposited on the emission layer to form a hole blocking layer having a thickness of 200 Å, TPBI was deposited on the hole blocking layer to form an electron transport layer having a thickness of 300 Å, LiF was deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and then, Al was deposited on the electron injection layer to form a cathode having a thickness of 3,000 Å thereby completing the manufacture of a light-emitting device 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Examples 2 to 6 and Comparative Examples 1 and 2 
     Light-emitting devices were manufactured in the same manner as in Example 1, except that the compounds shown in Table 1 were utilized as the host for forming the emission layer. 
     Evaluation Example 2 
     The driving voltage (V) at 1,000 cd/m 2 , luminescence efficiency (cd/A), external maximum quantum efficiency (%), and emission color of each of the light-emitting devices manufactured in Examples 1 to 6 and Comparative Examples 1 and 2 were measured using a Keithley MU 236 and luminance meter PR650, and results thereof are shown in Table 2. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Lumi- 
                   
                   
                 Maximum 
                   
               
               
                   
                 nescent 
                 Driving 
                   
                 quantum 
                   
               
               
                   
                 material 
                 voltage 
                 Efficiency 
                 efficiency 
                 Emission 
               
               
                   
                 (host) 
                 (V) 
                 (cd/A) 
                 (%) 
                 color 
               
               
                   
               
             
            
               
                 Example 1 
                 Compound 
                 4.2 
                 22.5 
                 22.1 
                 Blue 
               
               
                   
                 1 
                   
                   
                   
                   
               
               
                 Example 2 
                 Compound 
                 4.1 
                 22.4 
                 21.6 
                 Blue 
               
               
                   
                 2 
                   
                   
                   
                   
               
               
                 Example 3 
                 Compound 
                 4.2 
                 25.8 
                 24.7 
                 Blue 
               
               
                   
                 3 
                   
                   
                   
                   
               
               
                 Example 4 
                 Compound 
                 4.2 
                 22.7 
                 21.7 
                 Blue 
               
               
                   
                 7 
                   
                   
                   
                   
               
               
                 Example 5 
                 Compound 
                 4.1 
                 22.4 
                 21.8 
                 Blue 
               
               
                   
                 27 
                   
                   
                   
                   
               
               
                 Example 6 
                 Compound 
                 4.0 
                 22.3 
                 21.3 
                 Blue 
               
               
                   
                 31 
                   
                   
                   
                   
               
               
                 Comparative 
                 RE1 
                 4.5 
                 16.3 
                 15.2 
                 Blue 
               
               
                 Example 1 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 RE2 
                 5.3 
                 10.2 
                 16.9 
                 Blue 
               
               
                 Example 2 
               
               
                   
               
            
           
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Referring to Table 2, the light-emitting devices of Examples 1 to 6, including the compound represented by Formula 1 as a host in the emission layer, have improved driving voltage, improved efficiency, and improved maximum quantum efficiency compared to those of Comparative Examples 1 and 2. 
     As apparent from the foregoing description, as the light-emitting device may include the heterocyclic compound represented by Formula 1, the light-emitting device may have excellent luminescence efficiency and excellent emission lifespan. Thus, a high-quality electronic apparatus may be manufactured by using 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 suitable changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims, and equivalents thereof.