Heterocyclic compound and organic light-emitting device including the same

1. An organic light-emitting device comprising:

a first electrode;

a second electrode facing the first electrode;

an organic layer between the first electrode and the second electrode and comprising an emission layer; and

at least one heterocyclic compound represented by one of Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, and 1-4B:

wherein, in Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, and 1-4B,

in Formula 1-1A, 1-1B, 1-3A, 1-3B, 1-4A, and 1-4B, Ar 1 is selected from groups represented by Formulae 6-1 to 6-35, and

in Formula 1-2A, Ar 1 is selected from groups represented by Formulae 6-1 to 6-33 and 6-35:

wherein, in Formulae 6-1 to 6-35,

Ph indicates a phenyl group, t-Bu indicates a tert-butyl group, and Cz indicates a carbazolyl group, and

* indicates a binding site to a neighboring atom,

D 1a and D 1b are each independently a group represented by Formula 2, and

D 1a and D 1b are identical to or different from each other:

wherein, in Formula 2,

X 1 is selected from a single bond, C(R 5 )(R 6 ), Si(R 5 )(R 6 ), N(R 5 ), O, and S,

A 1 and A 2 are each independently a C 5 -C 60 carbocyclic group or a C 1 -C 60 heterocyclic group,

a1 is 0,

* indicates a binding site to a neighboring atom,

in Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, 1-4B, and 2,

R 1 to R 6 are each independently selected from hydrogen, deuterium, —F —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 10 cycloalkyl group, a substituted or unsubstituted C 1 -C 10 heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10 cycloalkenyl group, a substituted or unsubstituted C 1 -C 10 heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 1 -C 60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —S(═O) 2 (Q 1 ), and —P(═O)(Q 1 )(Q 2 ),

except that

in Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, and 1-4B, R 1 is not a C 1 -C60 alkyl group substituted with three —F, and R 2 is not a C 1 -C 60 alkyl group substituted with three —F, and

in Formulae 1-3A, 1-3B, 1-4A, and 1-4B, R 1 and

R 2 are each hydrogen,

c1 is an integer from 1 to 3,

c2 is an integer from 1 to 4,

c3 and c4 are each independently an integer from 1 to 5,

at least one substituent of the substituted C 3 -C 10 cycloalkylene group, the substituted C 1 -C 10 heterocycloalkylene group, the substituted C 3 -C 10 cycloalkenylene group, the substituted C 1 -C 10 heterocycloalkenylene group, the substituted C 6 -C 60 arylene group, the substituted C 1 -C 60 heteroarylene group, the substituted divalent non-aromatic condensed polycyclic group, the substituted divalent non-aromatic condensed heteropolycyclic group, the substituted C 1 -C 60 alkyl group, the substituted C 2 -C 60 alkenyl group, the substituted C 2 -C 60 alkynyl group, the substituted C 1 -C 60 alkoxy group, the substituted C 3 -C 10 cycloalkyl group, the substituted C 1 -C 10 heterocycloalkyl group, the substituted C 3 -C 10 cycloalkenyl group, the substituted C 1 -C 10 heterocycloalkenyl group, the substituted C 6 -C 60 aryl group, the substituted C 6 -C 60 aryloxy group, the substituted C 6 -C 60 arylthio group, the substituted C 1 -C 60 heteroaryl group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is selected from:

deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, and a C 1 -C 60 alkoxy group;

a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, and a C 1 -C 60 alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C 3 -C 10 cycloalkyl group, a C 1 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 1 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —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 ), and —P(═O)(Q 11 )(Q 12 );

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 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group;

a C 3 -C 10 cycloalkyl group, a C 1 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 1 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono 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 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 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —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 ), and —P(═O)(Q 21 )(Q 22 ), and

—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 ), and —P(═O)(Q 31 )(Q 32 ), and

Q 1 to Q 3 , Q 11 to Q 13 , Q 21 to Q 23 , and Q 31 to Q 33 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono 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 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, a monovalent non-aromatic condensed heteropolycyclic group, a biphenyl group, and a terphenyl group.

2. The organic light-emitting device of claim 1 , wherein

the first electrode is an anode,

the second electrode is a cathode,

the organic layer comprises the at least one heterocyclic compound,

the organic layer further comprises 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 comprises 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 comprises a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof.

3. The organic light-emitting device of claim 2 , wherein

the hole transport region comprises a hole transport layer, and

the hole transport layer comprises a first hole transport layer and a second hole transport layer.

4. The organic light-emitting device of claim 2 , wherein

the electron transport region comprises at least one selected from a phosphine oxide-containing compound, a silyl-containing compound, and a silyl-substituted phosphine oxide-containing compound.

5. The organic light-emitting device of claim 1 , wherein

the emission layer comprises the at least one heterocyclic compound.

6. The organic light-emitting device of claim 5 , wherein

the emission layer emits blue light having a wavelength of maximum emission in a range of about 390 nm to about 440 nm.

7. The organic light-emitting device of claim 5 , wherein

the emission layer further comprises a phosphorescent dopant or a fluorescent dopant.

8. The organic light-emitting device of claim 7 , wherein

the phosphorescent dopant comprises an organometallic complex represented by Formula 401:

wherein, in Formulae 401 and 402,

M is selected from iridium (Ir), platinum (Pt), palladium (Pd), osmium (Os), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), rhodium (Rh), and thulium (Tm),

L 401 is selected from ligands represented by Formula 402, and xc1 is 1, 2, or 3, wherein, when xc1 is 2 or more, two or more L 401 (s) are identical to or different from each other,

L 402 is an organic ligand, and xc2 is an integer from 0 to 4, wherein, when xc2 is 2 or more, two or more L 402 (s) are identical to or different from each other,

X 401 to X 404 are each independently nitrogen or carbon,

X 401 and X 403 are linked via a single bond or a double bond, and X 402 and X 404 are linked via a single bond or a double bond,

A 401 and A 402 are each independently a C 5 -C 60 carbocyclic group or a C 1 -C 60 heterocyclic group,

X 405 is a single bond, *—O—*′, *—S—*′, *—C(═O)—*′, *—N(Q 411 )-*′, *—C(Q 411 )(Q 412 )-*′, *—C(Q 411 )═C(Q 412 )-*′, *—C(Q 411 )=*′, or *═C(Q 411 )=*′, wherein Q 411 and Q 412 are each independently hydrogen, deuterium, a C 1 -C 20 alkyl group, a C 1 -C 20 alkoxy group, a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group,

X 406 is a single bond, O, or S,

R 401 and R 402 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a substituted or unsubstituted C 1 -C 20 alkyl group, a substituted or unsubstituted C 1 -C 20 alkoxy group, a substituted or unsubstituted C 3 -C 10 cycloalkyl group, a substituted or unsubstituted C 1 -C 10 heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10 cycloalkenyl group, a substituted or unsubstituted C 1 -C 10 heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 1 -C 60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —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 ), and —P(═O)(Q 401 )(Q 402 ), wherein Q 401 to Q 403 are each independently selected from a C 1 -C 10 alkyl group, a C 1 -C 10 alkoxy group, a C 6 -C 20 aryl group, and a C 1 -C 20 heteroaryl group,

xc11 and xc12 are each independently an integer from 0 to 10, and

* and *′ in Formula 402 each indicate a binding site to M in Formula 401.

9. A heterocyclic compound represented by one of Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, and 1-4B:

wherein, in Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, and 1-4B,

in Formulae 1-1A, 1-1B, 1-3A, 1-3B, 1-4A, and 1-4B, Ar 1 is selectee from groups represented by Formulae 6-1 to 6-35, and

in Formula 1-2A, Ar 1 is selected from groups represented by Formulae 6-1 to 6-33 and 6-35:

wherein, in Formulae 6-1 to 6-35,

Ph indicates a phenyl group, t-Bu indicates a tert-butyl group, and Cz indicates a carbazolyl group, and

* indicates a binding site to a neighboring atom,

D 1a and D 1b are each independently a group represented by Formula 2, and

D 1a and D 1b are identical to or different from each other:

wherein, in Formula 2,

X 1 is selected from a single bond, C(R 5 )(R 6 ), Si(R 5 )(R 6 ), N(R 5 ), O, and S,

A 1 and A 2 are each independently a C 5 -C 60 carbocyclic group or a C 1 -C 60 heterocyclic group,

a1 is 0,

* indicates a binding site to a neighboring atom,

in Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, 1-4B, and 2,

R 1 to R 6 are each independently selected from hydrogen, deuterium, —F —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 10 cycloalkyl group, a substituted or unsubstituted C 1 -C 10 heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10 cycloalkenyl group, a substituted or unsubstituted heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 1 -C 60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —Si(Q 1 )(Q 2 )(Q 3 ), —N(Q 1 )(Q 2 ), —B(Q 1 )(Q 2 ), —S(═O) 2 (Q 1 ), and —P(═O)(Q 1 )(Q 2 ),

except that

in Formulae 1-1A, 1-1B, 1-2A, 1-3A, 1-3B, 1-4A, and 1-4B, R 1 is not a C 1 -C 60 alkyl group substituted with three —F, and R 2 is not a C 1 -C 60 alkyl group substituted with three —F, and

in Formulae 1-3A, 1-3B, 1-4A, and 1-4B, R 1 and

R 2 are each hydrogen,

c1 is an integer from 1 to 3,

c2 is an integer from 1 to 4,

c3 and c4 are each independently an integer from 1 to 5,

at least one substituent of the substituted C 3 -C 10 cycloalkylene group, the substituted C 1 -C 10 heterocycloalkylene group, the substituted C 3 -C 10 cycloalkenylene group, the substituted C 1 -C 10 heterocycloalkenylene group, the substituted C 6 -C 60 arylene group, the substituted C 1 -C 60 heteroarylene group, the substituted divalent non-aromatic condensed polycyclic group, the substituted divalent non-aromatic condensed heteropolycyclic group, the substituted C 1 -C 60 alkyl group, the substituted C 2 -C 60 alkenyl group, the substituted C 2 -C 60 alkynyl group, the substituted C 1 -C 60 alkoxy group, the substituted C 3 -C 10 cycloalkyl group, the substituted C 1 -C 10 heterocycloalkyl group, the substituted C 3 -C 10 cycloalkenyl group, the substituted C 1 -C 10 heterocycloalkenyl group, the substituted C 6 -C 60 aryl group, the substituted C 6 -C 60 aryloxy group, the substituted C 6 -C 60 arylthio group, the substituted C 1 -C 60 heteroaryl group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is selected from:

deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, and a C 1 -C 60 alkoxy group;

a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, and a C 1 -C 60 alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C 3 -C 10 cycloalkyl group, a C 1 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 1 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —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 ), and —P(═O)(Q 11 )(Q 12 );

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 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group;

a C 3 -C 10 cycloalkyl group, a C 1 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 1 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono 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 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 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —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 ), and —P(═O)(Q 21 )(Q 22 ); and

—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 ), and —P(═O)(Q 31 )(Q 32 ), and

Q 1 to Q 3 , Q 11 to Q 13 , Q 21 to Q 23 , and Q 31 to Q 33 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono 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 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, a monovalent non-aromatic condensed heteropolycyclic group, a biphenyl group, and a terphenyl group.

10. The heterocyclic compound of claim 9 , wherein

D 1a and D 1b are each independently selected from:

a carbazolyl group, a 9,10-dihydroacridinyl group, a phenoxazinyl group, a phenothiazinyl group, a benzocarbazolyl group, and a dibenzocarbazolyl group; and

a carbazolyl group, a 9,10-dihydroacridinyl group, a phenoxazinyl group, a phenothiazinyl group, a benzocarbazolyl group, and a dibenzocarbazolyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono 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 naphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a spiro-fluorene-benzofluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a triazinyl group, a dibenzofuranyl group, and a dibenzothiophenyl group.

11. The heterocyclic compound of claim 9 , wherein

D 1a and D 1b are each independently a group represented by Formula 2-1:

wherein, in Formula 2-1,

c3 and c4 are each independently an integer from 1 to 4,

X 1 , R 3 , and R 4 , are each independently the same as described in Formula 2, and

* indicates a binding site to a neighboring atom.

12. The heterocyclic compound of claim 9 , wherein

D 1a and D 1b are each independently selected from groups represented by Formulae 2-2 to 2-5:

wherein, in Formulae 2-2 to 2-5,

R 5 and R 6 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, a phenyl group, and a biphenyl group, and

* indicates a binding site to a neighboring atom.

13. A heterocyclic compound that is selected from Compounds 1 to 39: