Patent Publication Number: US-2016225992-A1

Title: Organic light-emitting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0008263, filed on Jan. 16, 2015, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     One or more aspects of embodiments of the present invention relate to an organic light-emitting device. 
     2. Description of the Related Art 
     Organic light emitting devices are self-emission devices that have wide viewing angles, high contrast ratios, short response times, and excellent brightness, driving voltage, and response speed characteristics, and can produce full-color images. 
     The organic light-emitting device may include a first electrode positioned on a substrate, and a hole transport region, an emission layer, an electron transport region, and a second electrode, sequentially positioned on the first electrode. Holes provided from the first electrode may move toward the emission layer through the hole transport region, and electrons provided from the second electrode may move toward the emission layer through the electron transport region. Carriers (e.g., holes and electrons), are then recombined in the emission layer to produce excitons. These excitons change from an excited state to a ground state, thereby generating light. 
     SUMMARY 
     One or more aspects of embodiments of the present invention are directed to an organic light-emitting device. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to one or more embodiments of the present invention, an organic light-emitting device includes an organic layer including a first electrode, a second electrode, and an emission layer between the first electrode and the second electrode; and 
     an electron transport region between the emission layer and the second electrode; 
     wherein the emission layer includes a first material represented by Formula 1 below; and 
     the electron transport region includes a second material represented by Formula 2 below: 
     
       
         
         
             
             
         
       
     
     wherein in Formulae 1, 2 and 2A to 2D, 
     L 11  is selected from a substituted or unsubstituted C 6 -C 60  arylene group and a substituted or unsubstituted C 1 -C 60  heteroarylene group; 
     a11 is an integer selected from 0, 1, 2 and 3; 
     R 11  is selected from a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group; 
     b11 is an integer selected from 1, 2 and 3; 
     R 12  to R 19  are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid (herein, also referring to a carboxylic acid group) or a salt thereof, a sulfonic acid (herein, also referring to a sulfonic acid group) or a salt thereof, a phosphoric acid (herein, also referring to 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, and —Si(Q 1 )(Q 2 )(Q 3 ); 
     R 20  is selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof and a substituted or unsubstituted C 1 -C 60  alkyl group; 
     b20 is selected from 1, 2, 3, 4 and 5; 
     A 21  and A 22  are each independently selected from groups represented by Formulae 2A to 2D, a substituted or unsubstituted C 6 -C 60  arene group and a substituted or unsubstituted C 1 -C 60  heteroarene group, wherein at least one selected from A 21  and A 22  is selected from groups represented by Formulae 2A to 2D, and A 21  and A 22  are different from each other; 
     X 21  is selected from oxygen (O), sulfur (S), N-[(L 21 ) a21 -(R 24 ) b24 ], and C(R 25 )(R 26 ); 
     L 21  and L 22  are each independently selected from a substituted or unsubstituted C 6 -C 60  arylene group, a substituted or unsubstituted C 1 -C 60  heteroarylene group, a substituted or unsubstituted divalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted divalent non-aromatic condensed heteropolycyclic group; 
     a21 and a22 are each independently selected from 0, 1, 2 and 3; 
     R 21  and R 24  are each independently a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group; 
     b21 and b24 are each independently selected from 1, 2 and 3; 
     R 22 , R 23 , R 25  and R 26  are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid 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, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group; 
     b22 and b23 are each independently selected from 1, 2, 3, 4, 5 and 6; and 
     at least one substituent of the substituted C 6 -C 60  arene group, substituted C 1 -C 60  heteroarene group, substituted C 6 -C 60  arylene group, substituted C 1 -C 60  heteroarylene group, substituted divalent non-aromatic condensed polycyclic group, substituted divalent non-aromatic condensed heteropolycyclic group, substituted C 1 -C 60  alkyl group, substituted C 2 -C 60  alkenyl group, substituted C 2 -C 60  alkynyl group, substituted C 1 -C 60  alkoxy group, substituted C 3 -C 10  cycloalkyl group, substituted C 1 -C 10  heterocycloalkyl group, substituted C 3 -C 10  cycloalkenyl group, substituted C 1 -C 10  heterocycloalkenyl group, substituted C 6 -C 60  aryl group, substituted C 6 -C 60  aryloxy group, substituted C 6 -C 60  arylthio group, substituted C 1 -C 60  heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group, and 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     wherein Q 1  to Q 3 , Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  are each independently selected from a C 1 -C 60  alkyl 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. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawing, which illustrates a schematic view of a structure of an organic light-emitting device according to one or more embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in more detail to embodiments, examples of which are illustrated in the accompanying drawing, 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 drawing, to explain aspects of the present description. Expressions such as “at least one of” or “at least one selected from”, when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     Hereinafter, like reference numerals in the drawing denote like elements and duplicative descriptions thereof will not be provided. 
     As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. 
     It will be understood that when a layer, region, or component is referred to as being “formed on,” another layer, region, or component, it can be directly or indirectly formed on the other layer, region, or component. That is, for example, intervening layers, regions, or components may be present. 
     Sizes of elements in the drawing may be exaggerated for convenience of explanation. In other words, since sizes and thicknesses of components in the drawing are arbitrarily illustrated for convenience of explanation, the following embodiments of the present invention are not limited thereto. 
     The expression “(organic layer) may include a first material” used herein may be interpreted as: “(organic layer) may include one or more identical first materials represented by Formula 1 or two or more different first materials represented by Formula 1”. 
     The term “organic layer” used herein refers to a single layer and/or a plurality of layers between the first electrode and the second electrode of an organic light-emitting device. A material included in the “organic layer” is not limited to an organic material. 
     A substrate may be additionally positioned under a first electrode  110  or on a second electrode  190 . A glass substrate or transparent plastic substrate, each with excellent mechanical strength, thermal stability, transparency, surface planarity, ease of handling and/or water resistance, may be used (utilized). 
     The first electrode  110  may be formed, for example, by depositing or sputtering a material for forming the first electrode on the substrate. When the first electrode  10  is an anode, the material for forming the first electrode may be selected from materials with a high work function so as to facilitate hole injection. The first electrode  110  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. The material for the first electrode may be a transparent and highly conductive material, and non-limiting examples of such material include indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), and zinc oxide (ZnO). When the first electrode  110  is a semi-transmissive electrode or a reflective electrode, the material for forming the first electrode may include at least one selected from magnesium (Mg), aluminum(Al), aluminum-lithium(Al—Li), calcium (Ca), magnesium-indium(Mg—In), and magnesium-silver (Mg—Ag). 
     The first electrode  110  may have a single-layered structure, or a multi-layered structure including two or more layers. For example, the first electrode  110  may have a three-layered structure of ITO/Ag/ITO, but the structure of the first electrode  110  is not limited thereto. 
     In some embodiments, an organic layer  150  is positioned on the first electrode  110 . The organic layer  150  may include an emission layer. 
     The organic layer  150  may further include a hole transport region between the first electrode and the emission layer. The organic layer  150  may further include an electron transport region between the emission layer and the second electrode. 
     The hole transport region may include at least one selected from a hole injection layer (HIL), a hole transport layer (HTL), a buffer layer, and an electron blocking layer (EBL), and the electron transport region may include at least one selected from a buffer layer (BL), an electron transport layer (ETL), and an electron injection layer (EIL), but embodiments of the present invention are not limited thereto. 
     The hole transport region may have a single-layered structure formed of a single material, a single-layered structure formed of a plurality of different materials, or a multi-layered structure having a plurality of layers formed of a plurality of different materials. 
     For example, the hole transport region may have a single-layered structure formed of a plurality of different materials, or a structure of hole injection layer/hole transport layer, a structure of hole injection layer/hole transport layer/buffer layer, a structure of hole injection layer/buffer layer, a structure of hole transport layer/buffer layer, or a structure of hole injection layer/hole transport layer/electron blocking layer, wherein the layers of each structure are sequentially stacked on the first electrode  110  in the stated order, but embodiments of the present invention are not limited thereto. 
     When the hole transport region includes a hole injection layer, the hole injection layer may be formed on the first electrode  110  by using (utilizing) one or more suitable methods, such as vacuum deposition, spin coating, casting, a Langmuir-Blodgett (LB) method, ink-jet printing, laser-printing, and/or laser-induced thermal imaging (LITI). 
     When the hole injection layer is formed by vacuum deposition, for example, the vacuum deposition may be performed at a deposition temperature of about 100° C. to about 500° C., at a vacuum degree of about 10 −8  torr to about 10 −3  torr, and at a deposition rate of about 0.01 Å/sec to about 100 Å/sec, depending on the compound for forming the hole injection layer to be deposited, and the structure of the hole injection layer to be formed. 
     When the hole injection layer is formed by spin coating, the spin coating may be performed at a coating rate of about 2000 rpm to about 5000 rpm, and at a temperature of about 80° C. to about 200° C., depending on the compound for forming the hole injection layer to be deposited, and the structure of the hole injection layer to be formed. 
     When the hole transport region includes a hole transport layer, the hole transport layer may be formed on the first electrode  110  or on the hole injection layer by using one or more suitable methods, such as vacuum deposition, spin coating, casting, a Langmuir-Blodgett (LB) method, ink-jet printing, laser-printing, and/or laser-induced thermal imaging (LITI). When the hole transport layer is formed by vacuum deposition and/or spin coating, deposition and coating conditions for the hole transport layer may be similar to the deposition and coating conditions for the hole injection layer. 
     The hole transport region may include at least one selected from m-MTDATA, TDATA, 2-TNATA, NPB, 3-NPB, TPD, Spiro-TPD, Spiro-NPB, methylated-NPB, TAPC, HMTPD, TCTA(4,4′,4″-tris(N-carbazolyl)triphenylamine(4,4′,4″-tris(N-carbazolyl)triphenylamine)), Pani/DBSA (polyaniline/dodecylbenzenesulfonic acid:polyaniline/dodecylbenzenesulfonic acid), PEDOT/PSS(poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate):poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)), Pani/CSA (polyaniline/camphor sulfonic acid:polyaniline/camphor sulfonic acid), PANI/PSS (polyaniline)/poly(4-styrenesulfonate):polyaniline)/poly(4-styrenesulfonate)), a compound represented by Formula 201, and a compound represented by Formula 202: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 201 and 202, 
     L 201  to L 205  may be each independently selected from a substituted or unsubstituted C 3 -C 10  cycloalkylene group, a substituted or unsubstituted C 1 -C 10  heterocycloalkylene group, a substituted or unsubstituted C 3 -C 10  cycloalkenylene group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenylene group, a substituted or unsubstituted C 6 -C 60  arylene group, a substituted or unsubstituted C 1 -C 60  heteroarylene group, a substituted or unsubstituted divalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted divalent non-aromatic condensed heteropolycyclic group, 
     at least one substituent of the substituted C 3 -C 10  cycloalkylene group, substituted C 1 -C 10  heterocycloalkylene group, substituted C 3 -C 10  cycloalkenylene group, substituted C 1 -C 10  heterocycloalkenylene group, substituted C 6 -C 60  arylene group, substituted C 1 -C 60  heteroarylene group, substituted divalent non-aromatic condensed polycyclic group, and substituted divalent non-aromatic condensed heteropolycyclic group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 201 )(Q 202 ), —Si(Q 203 )(Q 204 )(Q 205 ) and —B(Q 206 )(Q 207 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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, —N(Q 211 )(Q 212 ), —Si(Q 213 )(Q 214 )(Q 215 ) and —B(Q 216 )(Q 217 ); and 
     —N(Q 221 )(Q 222 ), —Si(Q 223 )(Q 224 )(Q 225 ) and —B(Q 226 )(Q 227 ); 
     xa1 to xa4 may be each independently selected from 0, 1, 2 and 3; 
     xa5 may be selected from 1, 2, 3, 4 and 5; and 
     R 201  to R 204  may be each independently selected from 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 231 )(Q 232 ), —Si(Q 233 )(Q 234 )(Q 235 ) and —B(Q 236 )(Q 237 ); 
     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; and 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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, —N(Q 241 )(Q 242 ), —Si(Q 243 )(Q 244 )(Q 245 ) and —B(Q 246 )(Q 247 ); 
     where Q 201  to Q 207 , Q 211  to Q 217 , Q 221  to Q 227 , Q 231  to Q 237 , and Q 241  to Q 247  may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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; and 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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. 
     For example, in Formulae 201 and 202, 
     L 201  to L 205  may be each independently selected from a phenylene group, a naphthylene group, a fluorenylene group, a spiro-fluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenanthrenylene group, an anthracenylene group, a pyrenylene group, a chrysenylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, a quinolinylene group, an isoquinolinylene group, a quinoxalinylene group, a quinazolinylene group, a carbazolylene group and a triazinylene group; and 
     a phenylene group, a naphthylene group, a fluorenylene group, a spiro-fluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenanthrenylene group, an anthracenylene group, a pyrenylene group, a chrysenylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, a quinolinylene group, an isoquinolinylene group, a quinoxalinylene group, a quinazolinylene group, a carbazolylene group and a triazinylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and a triazinyl group; 
     xa1 to xa4 may each independently be 0, 1 or 2; 
     xa5 may be 1, 2 or 3; and 
     R 201  to R 204  may be each independently selected from a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, an azulenyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group, but embodiments of the present invention are not limited thereto. 
     The compound represented by Formula 201 may be represented by Formula 201A: 
     
       
         
         
             
             
         
       
     
     For example, the compound represented by Formula 201 may be represented by Formula 201A-1, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
     
     The compound represented by Formula 202 may be represented by Formula 202A, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
     
     L 201  to L 203 , xa1 to xa3, xa5 and R 202  to R 204  in Formulae 201A, 201A-1 and 202A are the same as defined herein with respect to Formulae 201 and 202, descriptions of R 211  and R 212  are the same as the description of R 203 , and R 213  to R 216  may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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. 
     For example, L 201  to L 203  in Formulae 201A, 201A-1 and 202A may be each independently selected from a phenylene group, a naphthylene group, a fluorenylene group, a spiro-fluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenanthrenylene group, an anthracenylene group, a pyrenylene group, a chrysenylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, a quinolinylene group, an isoquinolinylene group, a quinoxalinylene group, a quinazolinylene group, a carbazolylene group and a triazinylene group; and 
     a phenylene group, a naphthylene group, a fluorenylene group, a spiro-fluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenanthrenylene group, an anthracenylene group, a pyrenylene group, a chrysenylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, a quinolinylene group, an isoquinolinylene group, a quinoxalinylene group, a quinazolinylene group, a carbazolylene group and a triazinylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; 
     xa1 to xa3 may be each independently 0 or 1; 
     R 202  to R 204 , R 211  and R 212  may be each independently selected from a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; 
     R 213  and R 214  may be each independently selected from a C 1 -C 20  alkyl group and a C 1 -C 20  alkoxy group; 
     a C 1 -C 20  alkyl group and a C 1 -C 20  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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; 
     R 215  and R 216  may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, 
     a C 1 -C 20  alkyl group and a C 1 -C 20  alkoxy group; 
     a C 1 -C 20  alkyl group and a C 1 -C 20  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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group and a triazinyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group and a triazinyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a triazinyl group; and 
     xa5 may be selected from 1 and 2. 
     R 213  and R 214  in Formulae 201A and 201A-1 may bind to each other to form a saturated or unsaturated ring. 
     The compound represented by Formula 201 and the compound represented by Formula 202 may each independently include Compounds HT1 to HT20, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the hole transport region may be in a range of about 100 Å to about 10,000 Å, for example, about 100 Å to about 1,000 Å. When the hole transport region includes the hole injection layer and the hole transport layer, a thickness of the hole injection layer may be in a range of about 100 Å to about 10,000 Å, for example, about 100 Å to about 1,000 Å, and the thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, for example about 100 Å to about 1,500 Å. When the thicknesses of the hole transport region, the hole injection layer, and the hole transport layer are within any of these ranges, satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The hole transport region may further include, in addition to the above-described materials, a charge-generation material for the improvement of conductive properties. The charge-generation material may be homogeneously or unhomogeneously dispersed in the hole transport region. 
     The charge-generation material may be, for example, a p-dopant. The p-dopant may be one selected from a quinone derivative, a metal oxide, and a cyano group-containing compound, but embodiments of the present invention are not limited thereto. Non-limiting examples of the p-dopant include quinone derivatives, such as tetracyanoquinonedimethane (TCNQ) and/or 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ); metal oxides, such as tungsten oxide and/or molybdenum oxide, and Compound HT-D1 illustrated below, but embodiments of the present invention are not limited thereto. 
     
       
         
         
             
             
         
       
     
     The hole transport region may further include, in addition to the hole injection layer and the hole transport layer, at least one selected from a buffer layer and an electron blocking layer. Since the buffer layer may compensate for an optical resonance distance according to a wavelength of light emitted from the emission layer, light-emission efficiency of the formed organic light-emitting device may be improved. As a material included in the buffer layer, materials that are included in the hole transport region may be used (utilized). The electron blocking layer prevents (or substantially blocks) the injection of electrons from the electron transport region. 
     An emission layer is formed on the first electrode  110  or the hole transport region by using one or more suitable methods, such as vacuum deposition, spin coating, casting, a LB method, ink-jet printing, laser-printing, and/or laser-induced thermal imaging (LITI). When the emission layer is formed by vacuum deposition and/or spin coating, deposition and coating conditions for the emission layer may be similar to the deposition and coating conditions for the hole injection layer. 
     When the organic light-emitting device  10  is a full color organic light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, or a blue emission layer, according to (or as defined by) a sub pixel. In some embodiments, the emission layer may have a stacked structure of a red emission layer, a green emission layer, and a blue emission layer, or may include a red-light emission material, a green-light emission material, and a blue-light emission material, which are mixed with each other in a single layer, to emit white light. In some embodiments, the emission layer may emit white light, and may further include a color converting layer (which converts white light to light of a desired color) or a color filter. 
     The emission layer may include a host and a dopant. 
     The host may include a first material represented by Formula 1: 
     
       
         
         
             
             
         
       
     
     L 11  in Formula 1 may be selected from a substituted or unsubstituted C 6 -C 60  arylene group and a substituted or unsubstituted C 1 -C 60  heteroarylene group; 
     at least one substituent of the substituted C 6 -C 60  arylene group and substituted C 1 -C 60  heteroarylene group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, L 11  in Formula 1 may be selected from a phenylene group, a naphthylene group, a phenanthrenylene group, an anthracenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a pyrrolylene group, a thiophenylene group, a furanylene group, an imidazolylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, an indolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a phenanthridinylene group, an acridinylene group, a phenanthrolinylene group, a benzofuranylene group, a benzothiophenylene group, a triazolylene group, a tetrazolylene group, a triazinylene group, a dibenzofuranylene group and a dibenzothiophenylene group; and 
     a phenylene group, a naphthylene group, a phenanthrenylene group, an anthracenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a pyrrolylene group, a thiophenylene group, a furanylene group, an imidazolylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, an indolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a phenanthridinylene group, an acridinylene group, a phenanthrolinylene group, a benzofuranylene group, a benzothiophenylene group, a triazolylene group, a tetrazolylene group, a triazinylene group, a dibenzofuranylene group and a dibenzothiophenylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl 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 hexacenyl group, a pentacenyl 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 indolyl group, an indazolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group and a dibenzocarbazolyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, L 11  in Formula 1 may be selected from a phenylene group and a naphthylene group; and 
     a phenylene group and a naphthylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a phenyl group and a naphthyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, L 11  in Formula 1 may be selected from groups represented by Formulae 3-1 to 3-15, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 3-1 to 3-15, 
     R 31  may be selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a phenyl group and a naphthyl group; 
     b31 may be selected from 1, 2, 3 and 4; 
     b32 may be selected from 1, 2, 3, 4, 5, and 6; and 
     each of * and *′ indicates a binding site to a neighboring atom. 
     In some embodiments, L 11  in Formula 1 may be represented by one selected of Formulae 4-1 to 4-11, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
     
     In Formulae 4-1 to 4-11, 
     each of * and *′ indicates a binding site to a neighboring atom. 
     a11 in Formula 1 indicates the number of L 11 , and may be selected from 0, 1, 2 and 3. When a11 is 0, (L 11 ) a11  may be a single bond. When a11 is 2 or more, a plurality of L 11  may be identical to or different from each other. For example, in Formula 1, a11 may be selected from 0 and 1, but embodiments of the present invention are not limited thereto. 
     R 11  in Formula 1 may be selected from a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group; 
     at least one substituent of the substituted C 6 -C 60  aryl group, substituted C 1 -C 60  heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, R 11  in Formula 1 may be selected from a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl 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 hexacenyl group, a pentacenyl 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 indolyl group, an indazolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group and a dibenzocarbazolyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl 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 hexacenyl group, a pentacenyl 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 indolyl group, an indazolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl 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 hexacenyl group, a pentacenyl 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 indolyl group, an indazolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group and a dibenzocarbazolyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 11  in Formula 1 may be selected from a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a dibenzofuranyl group and a dibenzothiophenyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a dibenzofuranyl group and a dibenzothiophenyl group, each substituted with at least one selected from a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, a phenyl group and a naphthyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 11  in Formula 1 is represented by one of Formulae 5-1 to 5-26, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 5-1 to 5-26, 
     Ph may be a phenyl group; and 
     * indicates a binding site to a neighboring atom. 
     b11 in Formula 1 indicates the number of R 11 , and may be selected from 1, 2 and 3. When b11 is 2 or more, a plurality of R 11  may be identical to or different from each other. For example, b11 in Formula 1 may be 1, but embodiments of the present invention are not limited thereto. 
     R 12  to R 19  in Formula 1 may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid 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 and —Si(Q 1 )(Q 2 )(Q 3 ); 
     at least one substituent of the substituted C 1 -C 60  alkyl group, substituted C 2 -C 60  alkenyl group, substituted C 2 -C 60  alkynyl group, substituted C 1 -C 60  alkoxy group, substituted C 3 -C 10  cycloalkyl group, substituted C 1 -C 10  heterocycloalkyl group, substituted C 3 -C 10  cycloalkenyl group, substituted C 1 -C 10  heterocycloalkenyl group, substituted C 6 -C 60  aryl group, substituted C 6 -C 60  aryloxy group, substituted C 6 -C 60  arylthio group, substituted C 1 -C 60  heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 1  to Q 3 , Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, R 12  to R 19  in Formula 1 may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a C 1 -C 60  alkyl group, a C 6 -C 60  aryl group, a C 1 -C 60  heteroaryl group and —Si(Q 1 )(Q 2 )(Q 3 ); 
     where Q 1  to Q 3  may be each independently selected from a C 1 -C 60  alkyl group and a C 6 -C 60  aryl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 12  to R 19  in Formula 1 may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, a phenyl group, a naphthyl group, a pyridinyl group and —Si(Q 1 )(Q 2 )(Q 3 ); 
     where Q 1  to Q 3  may be each independently selected from a methyl group, an ethyl group, an n-propyl group, an iso-propyl group and a phenyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 12  to R 19  in Formula 1 may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, a phenyl group and —Si(CH 3 ) 3 , but embodiments of the present invention are not limited thereto. 
     R 20  in Formula 1 may be selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof and a substituted or unsubstituted C 1 -C 60  alkyl group; and 
     at least one substituent of the substituted substituted C 1 -C 60  alkyl group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ), 
     where Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, R 20  in Formula 1 may be selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group and a tert-butyl group, but embodiments of the present invention are not limited thereto. 
     b20 in Formula 1 indicates the number of R 20 , and may be selected from 1, 2, 3, 4, and 5. When b20 is 2 or more, a plurality of R 20  may be identical to or different from each other. 
     In some embodiments, the first material of Formula 1 may be selected from compounds illustrated below, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In related organic light-emitting devices, an anthracene-based compound (included, for example, as a host in an emission layer) typically has a symmetric structure that is easily crystallized, and thus the possibility of film formation on such anthracene-based compound is low. However, the first material represented by Formula 1 has an asymmetric structure, and thus can increase the possibility of film formation. 
     In some embodiments, in the first material represented by Formula 1, a ninth carbon of an anthracene moiety is substituted with a phenyl group, and thus electrons may move at a slower rate than those of a comparative compound in which a ninth carbon of the anthracene moiety is substituted with a naphthyl group. Accordingly, an organic light-emitting device including the first material represented by Formula 1 may have a longer lifespan. 
     The dopant may include at least one selected from a fluorescent dopant and a phosphorescent dopant. 
     For example, the fluorescent dopant may include at least one selected from DPAVBi, BDAVBi, TBPe, DCM, DCJTB, Coumarin 6, and C545T: 
     
       
         
         
             
             
         
       
     
     In some embodiments, the fluorescent dopant may include a compound represented by Formula 501: 
     
       
         
         
             
             
         
       
     
     In Formula 501, 
     Ar 501  may be selected from a naphthalene group, a heptalene group, a fluorene group, a spiro-fluorene group, a benzofluorene group, a dibenzofluorene group, a phenalene group, a phenanthrene group, an anthracene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, naphthacene group, a picene group, a perylene group, a pentaphene group and an indenoanthracene group; and 
     a naphthalene group, a heptalene group, a fluorene group, a spiro-fluorene group, a benzofluorene group, a dibenzofluorene group, a phenalene group, a phenanthrene group, an anthracene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a naphthacene group, a picene group, a perylene group, a pentaphene group and an indenoanthracene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 and —Si(Q 501 )(Q 502 )(Q 503 ) (where Q 501  to Q 503  may be each independently selected from hydrogen, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 6 -C 60  aryl group and a C 1 -C 60  heteroaryl group); 
     L 501  to L 503  may be the same as defined in connection with L 201 ; 
     R 501  and R 502  may be each independently selected from: 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a triazinyl group, a dibenzofuranyl group and a dibenzothiophenyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a triazinyl group and a dibenzofuranyl group and a dibenzothiophenyl group, each substituted with at least one selected from deuterium, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a triazinyl group, a dibenzofuranyl group and a dibenzothiophenyl group; 
     xd1 to xd3 may be each independently selected from 0, 1, 2 and 3; and 
     xd4 may be selected from 1, 2, 3 and 4. 
     The fluorescent host may include at least one selected from Compounds FD1 to FD8: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     An amount of the dopant in the emission layer may be, for example, in a range of about 0.01 parts by weight to about 15 parts by weight based on 100 parts by weight of the host, but embodiments of the present invention are not limited thereto. 
     A thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. When the thickness of the emission layer is within any of these ranges, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     An electron transport region may be positioned on the emission layer. 
     The electron transport region may include at least one selected from a hole blocking layer (HBL), an electron transport layer (ETL), and an electron injection layer, but embodiments of the present invention are not limited thereto. 
     For example, the electron transport region may have a structure of electron transport layer/electron injection layer or a structure of hole blocking layer/electron transport layer/electron injection layer, where the layers of each structure are sequentially stacked on the emission layer in the stated order, but embodiments of the present invention are not limited thereto. 
     The electron transport region may include a second material represented by Formula 2: 
     
       
         
         
             
             
         
       
     
     In Formula 2, A 21  and A 22  may be each independently selected from groups represented by Formulae 2A to 2D, a substituted or unsubstituted C 6 -C 60  arene group and a substituted or unsubstituted C 1 -C 60  heteroarene group, at least one selected from A 21  and A 22  may be selected from groups represented by Formulae 2A to 2D, and A 21  and A 22  may be different from each other: 
     
       
         
         
             
             
         
       
     
     wherein R 22 , R 23 , b22, b23 and X 21  in Formulae 2A to 2D will be described later; and 
     at least one substituent of the substituted C 6 -C 60  arene group and substituted C 1 -C 60  heteroarene group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, A 21  in Formula 2 may be selected from a substituted or unsubstituted C 6 -C 60  arene group and a substituted or unsubstituted C 1 -C 60  heteroarene group; 
     A 22  may be selected from groups represented by Formulae 2A to 2D; and 
     A 21  and A 22  may be different from each other, but embodiments of the present invention are not limited thereto. 
     In some embodiments, A 21  in Formula 2 may be selected from a benzene group, a naphthalene group, an anthracene group, a pyridine group, a pyrimidine group, a pyrazine group, a quinoline group, an isoquinoline group, a 2,6-naphthyridine group, a 1,8-naphthyridine group, a 1,5-naphthyridine group, a 1,6-naphthyridine group, a 1,7-naphthyridine group, a 2,7-naphthyridine group, a quinoxaline group and a quinazoline group; 
     A 22  may be selected from groups represented by Formulae 2A to 2D; and 
     A 21  and A 22  may be different from each other, but embodiments of the present invention are not limited thereto. 
     In some embodiments, A 21  in Formula 2 may be selected from a benzene group and a naphthalene group; 
     A 22  may be selected from groups represented by Formulae 2A to 2D; and 
     A 21  and A 22  may be different from each other, but embodiments of the present invention are not limited thereto. 
     In some embodiments, in Formula 2, A 21  may be a benzene group; and 
     A 22  may be selected from groups represented by Formulae 2A to 2D, but embodiments of the present invention are not limited thereto. 
     For example, A 22  in Formula 2 may be selected from groups represented by Formulae 2A-1, 2A-2, 2B-1 to 2B-7, 2C-1 to 2C-6 and 2D-1 to 2D-7, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 2A-1, 2A-2, 2B-1 to 2B-7, 2C-1 to 2C-6, and 2D-1 to 2D-7, 
     X 21 , R 22 , R 23 , b22 and b23 are as described herein; and 
     C 1  and C 2  may each independently be a carbon atom in Formula 2. 
     In some embodiments, A 22  in Formula 2 may be selected from groups represented by Formulae 2A-1, 2A-2, 2B-4 to 2B-7, 2C-4, and 2D-4 to 2D-7, but embodiments of the present invention are not limited thereto. 
     In Formulae 2A to 2D, X 21  may be selected from O, S, N-[(L 21 ) a21 -(R 24 ) b24 ], and C(R 25 )(R 26 ); and L 21 , a21, R 24 , R 25 , R 26 , and b24 may be as described herein. 
     L 21  and L 22  in Formulae 2 and 2A to 2D may be each independently selected from a substituted or unsubstituted C 6 -C 60  arylene group, a substituted or unsubstituted C 1 -C 60  heteroarylene group, a substituted or unsubstituted divalent non-aromatic condensed polycyclic group and a substituted or unsubstituted divalent non-aromatic condensed heteropolycyclic group; and 
     at least one substituent of the substituted C 6 -C 60  arylene group, substituted C 1 -C 60  heteroarylene group, substituted divalent non-aromatic condensed polycyclic group and substituted divalent non-aromatic condensed heteropolycyclic group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, L 21  and L 22  in Formulae 2 and 2A to 2D may be each independently selected from a phenylene group, a naphthylene group, a phenanthrenylene group, an anthracenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a pyrrolylene group, a thiophenylene group, a furanylene group, an imidazolylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, an indolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a phenanthridinylene group, an acridinylene group, a phenanthrolinylene group, a benzofuranylene group, a benzothiophenylene group, a triazolylene group, a tetrazolylene group, a triazinylene group, a dibenzofuranylene group and a dibenzothiophenylene group; and 
     a phenylene group, a naphthylene group, a phenanthrenylene group, an anthracenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a pyrrolylene group, a thiophenylene group, a furanylene group, an imidazolylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, an indolylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a phenanthridinylene group, an acridinylene group, a phenanthrolinylene group, a benzofuranylene group, a benzothiophenylene group, a triazolylene group, a tetrazolylene group, a triazinylene group, a dibenzofuranylene group and a dibenzothiophenylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl 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 hexacenyl group, a pentacenyl 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 indolyl group, an indazolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group and a dibenzocarbazolyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, L 21  and L 22  in Formulae 2 and 2A to 2D may be each independently selected from: 
     a phenylene group and a naphthylene group; and 
     a phenylene group and a naphthylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a phenyl group and a naphthyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, L 21  and L 22  Formulae 2 and 2A to 2D may be each independently selected from groups represented by Formulae 3-1 to 3-15, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 3-1 to 3-15, 
     R 31  may be selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a phenyl group and a naphthyl group; 
     b31 may be selected from 1, 2, 3 and 4; 
     b32 may be selected from 1, 2, 3, 4, 5, and 6; and 
     each of * and *′ indicates a binding site to a neighboring atom. 
     In some embodiments, L 21  and L 22  in Formulae 2 and 2A to 2D may be each independently represented by any one of Formulae 4-1 to 4-11, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
     
     In Formulae 4-1 to 4-11, 
     each of * and *′ indicates a binding site to a neighboring atom. 
     a21 in Formula 2 indicates the number of L 21  and may be selected from 0, 1, 2 and 3. When a21 is 0, (L 21 ) a21  may be a single bond. When a21 is 2 or more, a plurality of L 21  may be identical to or different from each other. For example, a21 in Formula 2 may be selected from 0 and 1, but embodiments of the present invention are not limited thereto. 
     a22 in Formulae 2A to 2D indicates the number of L 22  and may be selected from 0, 1, 2 and 3. When a22 is 0, (L 22 ) a22  may be a single bond. When a22 is 2 or more, a plurality of L 22  may be identical to or different from each other. For example, a22 in Formulae 2A to 2D may be selected from 0 and 1, but embodiments of the present invention are not limited thereto. 
     R 21  and R 24  in Formulae 2 and 2A to 2D may be each independently selected from a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group; and 
     at least one substituent of the substituted C 6 -C 60  aryl group, substituted C 1 -C 60  heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ) and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 11  to Q 17 , Q 21  to Q 27 , and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, R 21  and R 24  in Formulae 2 and 2A to 2D may be each independently selected from a phenyl group, a pentalenyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptalenyl group, an indacenyl group, an acenaphthyl group, a fluorenyl group, a spiro-fluorenyl 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 pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isooxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a phenanthridinyl group, an acridinyl(acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzothiazolyl group, an isobenzothiazolyl 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 benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, a pyridobenzofuranyl group, a pyrimidobenzofuranyl group, a pyridobenzothiophenyl group, and a pyrimidobenzothiophenyl group; and 
     a phenyl group, a pentalenyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptalenyl group, an indacenyl group, an acenaphthyl group, a fluorenyl group, a spiro-fluorenyl 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 pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzothiazolyl group, an isobenzothiazolyl 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 benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, a pyridobenzofuranyl group, a pyrimidobenzofuranyl group, a pyridobenzothiophenyl group and a pyrimidobenzothiophenyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a pentalenyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptalenyl group, an indacenyl group, an acenaphthyl group, a fluorenyl group, a spiro-fluorenyl 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 pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a phthalazinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a benzothiazolyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group and a dibenzocarbazolyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 21  and R 24  in Formulae 2 and 2A to 2D may be each independently selected from a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl 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 oxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, an indolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a triazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, a pyridobenzofuranyl group, a pyrimidobenzofuranyl group, a pyridobenzothiophenyl group and a pyrimidobenzothiophenyl group; and 
     a phenyl group, a naphthyl group, a fluorenyl group, a spiro-fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthrenyl group, an anthracenyl 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 oxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, an indolyl group, a quinolinyl group, an isoquinolinyl group, a carbazolyl group, a benzoquinolinyl group, a naphthyridinyl group, a quinoxalinyl group, a quinazolinyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, a triazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, a pyridobenzofuranyl group, a pyrimidobenzofuranyl group, a pyridobenzothiophenyl group and a pyrimidobenzothiophenyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a phenyl group and a naphthyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 21  and R 24  in Formulae 2 and 2A to 2D may be each independently selected from groups represented by Formulae 6-1 to 6-75, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 6-1 to 6-75, 
     X 61  may be selected from O, S, N(R 64 ), and C(R 64 )(R 65 ); 
     R 61  to R 65  may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a phenyl group and a naphthyl group; 
     b61 may be selected from 1, 2, 3, 4 and 5; 
     b62 may be selected from 1, 2, 3, 4, 5, 6 and 7; 
     b63 may be selected from 1, 2 and 3; 
     b64 may be selected from 1, 2, 3 and 4; 
     b65 may be selected from 1, 2, 3, 4, 5 and 6; and 
     * indicates a binding site to a neighboring atom. 
     In some embodiments, R 21  and R 24  in Formulae 2 and 2A to 2D may be each independently represented by any one of Formulae 7-1 to 7-182, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 7-1 to 7-182, 
     Ph may be a phenyl group; and 
     * indicates a binding site to a neighboring atom. 
     b21 in Formula 2 indicates the number of R 21  and may be selected from 1, 2 and 3. When b21 is 2 or more, a plurality of R 21  may be identical to or different from each other, but embodiments of the present invention are not limited thereto. For example, b21 in Formula 2 may be selected from 1 and 2, but embodiments of the present invention are not limited thereto. In some embodiments, b21 in Formula 2 may be 1, but embodiments of the present invention are not limited thereto. 
     b24 in Formulae 2A to 2D indicates the number of R 24  and may be selected from 1, 2 and 3. When b24 is 2 or more, a plurality of R 24  may be identical to or different from each other, but embodiments of the present invention are not limited thereto. For example, b24 in Formulae 2A to 2D may be selected from 1 and 2, but embodiments of the present invention are not limited thereto. In some embodiments, b24 in Formulae 2A to 2D may be 1, but embodiments of the present invention are not limited thereto. 
     R 22 , R 23 , R 25  and R 26  in Formulae 2 and 2A to 2D may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid 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 and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group; and 
     at least one substituent of the substituted C 1 -C 60  alkyl group, substituted C 2 -C 60  alkenyl group, substituted C 2 -C 60  alkynyl group, substituted C 1 -C 60  alkoxy group, substituted C 3 -C 10  cycloalkyl group, substituted C 1 -C 10  heterocycloalkyl group, substituted C 3 -C 10  cycloalkenyl group, substituted C 1 -C 10  heterocycloalkenyl group, substituted C 6 -C 60  aryl group, substituted C 6 -C 60  aryloxy group, substituted C 6 -C 60  arylthio group, substituted C 1 -C 60  heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group may be selected from: 
     deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group 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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 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 14 )(Q 15 ), and —B(Q 16 )(Q 17 ); 
     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 amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 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 24 )(Q 25 ) and —B(Q 26 )(Q 27 ); and 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 34 )(Q 35 ) and —B(Q 36 )(Q 37 ); 
     where Q 11  to Q 17 , Q 21  to Q 27  and Q 31  to Q 37  may be each independently selected from a C 1 -C 60  alkyl 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. 
     For example, R 22 , R 23 , R 25  and R 26  in Formulae 2A to 2D may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a C 1 -C 60  alkyl group, a C 6 -C 60  aryl group and a C 1 -C 60  heteroaryl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 22 , R 23 , R 25  and R 26  in Formulae 2A to 2D may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, a phenyl group, a naphthyl group and a pyridinyl group, but embodiments of the present invention are not limited thereto. 
     In some embodiments, R 22 , R 23 , R 25  and R 26  in Formulae 2A to 2D may be each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group and a phenyl group, but embodiments of the present invention are not limited thereto. 
     b22 in Formulae 2A to 2D indicates the number of R 22  and may be selected from 1, 2, 3, 4, 5 and 6. When b22 is 2 or more, a plurality of R 22  may be identical to or different from each other. 
     b23 in Formulae 2A to 2D indicates the number of R 23  and may be selected from 1, 2, 3, 4, 5 and 6. When b23 is 2 or more, a plurality of R 23  may be identical to or different from each other. 
     For example, the second material of Formula 2 may be selected from groups represented by Formulae 2-1 to 2-43, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 2-1 to 2-43, 
     descriptions of A 21 , L 21 , a21, R 21  to R 23 , b21 to b23 and X 21  may be the same as those provided in connection with Formulae 2 and 2A to 2D. 
     In some embodiments, the second material may be selected from groups represented by Formulae 2-51 to 2-93, but embodiments of the present invention are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     An energy level T1 of the second material represented by Formula 2 may be high. For example, the energy level T1 of the second material may be 2.2 eV or more. When the energy level T1 of the second material is within this range, an organic light-emitting device including the second material represented by Formula 2 may effectively hold excitons in the emission layer. 
     In addition, when the second material represented by Formula 2 has a relatively high energy level T1, a band gap thereof may be large and a LUMO energy level thereof may be low. Accordingly, electrons may be effectively captured in the emission layer of the organic light-emitting device including the second material. 
     In one or more embodiments of the present invention, the organic light-emitting device including the second material represented by Formula 2 may have a high efficiency and long lifespan. 
     The electron transport region may further include a buffer layer. The buffer layer may be formed to prevent (or substantially block) electrons from being injected into the emission layer too fast. Accordingly, an organic light-emitting device including the buffer layer may have a high efficiency and long lifespan. 
     When the electron transport region includes the buffer layer, the buffer layer may be formed on the emission layer by using (utilizing) one or more suitable methods, such as vacuum deposition, spin coating, casting, a LB method, ink-jet printing, laser-printing, and/or LITI. When the buffer layer is formed by vacuum deposition and/or spin coating, deposition and coating conditions for the buffer layer may be similar to the deposition and coating conditions for the hole injection layer. 
     The buffer layer may include, for example, the second material represented by Formula 2. When the buffer layer includes the second material, the buffer layer may be adjacent to the emission layer including the first material. 
     In some embodiments, the buffer layer may include at least one selected from BCP and Bphen: 
     
       
         
         
             
             
         
       
     
     A thickness of the buffer layer may be in a range of about 20 Å to about 1,000 Å, for example, about 30 Å to about 300 Å. When the thickness of the buffer layer is within any of the ranges described above, excellent hole blocking characteristics may be obtained without a substantial increase in driving voltage. 
     In some embodiments, the electron transport region may include an electron transport layer. The electron transport layer may be formed on the emission layer or on the buffer layer by using one or more suitable methods, such as vacuum deposition, spin coating, casting, a LB method, ink-jet printing, laser-printing, and/or LITI. When the electron transport layer is formed by vacuum deposition and/or spin coating, deposition and coating conditions for the electron transport layer may be similar to the deposition and coating conditions for the hole injection layer. 
     In some embodiments, the electron transport layer may include the second material represented by Formula 2. When the electron transport layer includes the second material, the electron transport layer may be adjacent to the emission layer including the first material. 
     In some embodiments, the electron transport layer may include at least one selected from BCP, Bphen, Alq 3 , Balq, TAZ and NTAZ. 
     
       
         
         
             
             
         
       
     
     A thickness of the electron transport layer may be in a range of about 100 Å to about 1,000 Å, for example, about 150 Å to about 500 Å. When the thickness of the electron transport layer is within any of the ranges described above, excellent electron transport characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport layer may further include a metal-containing material, in addition to the materials described above. 
     The metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (lithium quinolate, LiQ) and/or ET-D2. 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer (EIL) that facilitates electron injection from the second electrode  190 . 
     The electron injection layer may be formed on the electron transport layer by using one or more suitable methods, such as vacuum deposition, spin coating, casting, a LB method, ink-jet printing, laser-printing, and/or LITI. When the electron injection layer is formed by vacuum deposition and/or spin coating, deposition and coating conditions for the electron injection layer may be similar to the deposition and coating conditions for the hole injection layer. 
     The electron injection layer may include at least one selected from LiF, NaCl, CsF, Li 2 O, BaO and LiQ. 
     A thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, for example, about 3 Å to about 90 Å. When the thickness of the electron injection layer is within any of the ranges described above, the electron injection layer may have satisfactory electron injection characteristics without a substantial increase in driving voltage. 
     The second electrode  190  is positioned on the organic layer  150  having the structure as described herein. The second electrode  190  may be a cathode that is an electron injection electrode, and in this regard, a material for forming the second electrode  190  may be a material having a low work function, for example, a metal, an alloy, an electrically conductive compound, or a mixture thereof. Non-limiting examples of material for forming the second electrode  190  include lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), and magnesium-silver (Mg—Ag). In some embodiments, the material for forming the second electrode  190  may be ITO or IZO. The second electrode  190  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. 
     The organic light-emitting device may include the first material represented by Formula 1 and the second material represented by Formula 2, so that the carrier balance in the emission layer may be improved. Accordingly, the organic light-emitting device may have a high efficiency and long lifespan. 
     Hereinbefore, the organic light-emitting device was described by referring to the drawing, but embodiments of the present invention are not limited thereto. 
     A C 1 -C 60  alkyl group used herein refers to a linear or branched aliphatic hydrocarbon monovalent group having 1 to 60 carbon atoms in the main chain, and non-limiting examples thereof include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an iso-amyl group, and a hexyl group. A C 1 -C 60  alkylene group used herein refers to a divalent group having the same structure as the C 1 -C 60  alkyl group. 
     A C 1 -C 60  alkoxy group used herein refers to a monovalent group represented by —OA 101  (where A 101  is the C 1 -C 60  alkyl group), and non-limiting examples thereof include a methoxy group, an ethoxy group, and an isopropyloxy group. 
     A C 2 -C 60  alkenyl group used herein refers to a hydrocarbon group having at least one carbon-carbon double bond at one or more positions along a carbon chain of the C 2 -C 60  alkyl group (e.g., in the middle or at either terminal end of the C 2 -C 60  alkyl group), and non-limiting examples thereof include an ethenyl group, a propenyl group, and a butenyl group. A C 2 -C 60  alkenylene group used herein refers to a divalent group having the same structure as the C 2 -C 60  alkenyl group. 
     A C 2 -C 60  alkynyl group used herein refers to a hydrocarbon group having at least one carbon-carbon triple bond at one or more positions along a carbon chain of the C 2 -C 60  alkyl group (e.g., in the middle or at either terminal end of the C 2 -C 60  alkyl group), and non-limiting examples thereof include an ethynyl group and a propynyl group. A C 2 -C 60  alkynylene group used herein refers to a divalent group having the same structure as the C 2 -C 60  alkynyl group. 
     A C 3 -C 10  cycloalkyl group used herein refers to a monovalent hydrocarbon monocyclic group having 3 to 10 carbon atoms as ring-forming atoms, and non-limiting examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. A C 3 -C 10  cycloalkylene group used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkyl group. 
     A C 1 -C 10  heterocycloalkyl group used herein refers to a monovalent monocyclic group having at least one hetero atom selected from N, O, P, and S as a ring-forming atom, and 1 to 10 carbon atoms as the remaining ring-forming atoms, and non-limiting examples thereof include a tetrahydrofuranyl group and a tetrahydrothiophenyl group. A C 1 -C 10  heterocycloalkylene group used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkyl group. 
     A C 3 -C 10  cycloalkenyl group used herein refers to a monovalent monocyclic group that has 3 to 10 carbon atoms as ring-forming atoms and at least one double bond in the ring thereof, and does not have aromaticity. Non-limiting examples of the C 3 -C 10  cycloalkenyl group include a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. A C 3 -C 10  cycloalkenylene group used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkenyl group. 
     A C 1 -C 10  heterocycloalkenyl group used herein refers to a monovalent monocyclic group that has at least one hetero atom selected from N, O, P, and S as a ring-forming atom, 1 to 10 carbon atoms as the remaining ring-forming atoms, and at least one double bond in its ring. Non-limiting examples of the C 1 -C 10  heterocycloalkenyl group include a 2,3-hydrofuranyl group and a 2,3-hydrothiophenyl group. A C 1 -C 10  heterocycloalkenylene group used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkenyl group. 
     A C 6 -C 60  aryl group used herein refers to a monovalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms as ring-forming atoms, and a C 6 -C 60  arylene group used herein refers to a divalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms as ring-forming atoms. Non-limiting examples of the C 6 -C 60  aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, and a chrysenyl group. When the C 6 -C 60  aryl group and/or the C 6 -C 60  arylene group include two or more rings, the rings may be respectively fused to each other. 
     A C 1 -C 60  heteroaryl group used herein refers to a monovalent group having a carbocyclic aromatic system that has at least one hetero atom selected from N, O, P, and S as a ring-forming atom, and 1 to 60 carbon atoms as the remaining ring-forming atoms. A C 1 -C 60  heteroarylene group used herein refers to a divalent group having a carbocyclic aromatic system that has at least one hetero atom selected from N, O, P, and S as a ring-forming atom, and 1 to 60 carbon atoms as the remaining ring-forming atoms. Non-limiting examples of the C 1 -C 60  heteroaryl group include a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, and an isoquinolinyl group. When the C 1 -C 60  heteroaryl group and/or the C 1 -C 60  heteroarylene group include two or more rings, the rings may be respectively fused to each other. 
     A C 6 -C 60  aryloxy group used herein refers to a monovalent group represented by —OA 102  (where A 102  is the C 6 -C 60  aryl group), and a C 6 -C 60  arylthio group used herein refers to a monovalent group represented by —SA 103  (where A 103  is the C 6 -C 60  aryl group). 
     A monovalent non-aromatic condensed polycyclic group used herein refers to a monovalent group that has two or more rings condensed to each other, only carbon atoms as ring-forming atoms, and does not have overall aromaticity. Non-limiting example of the monovalent non-aromatic condensed polycyclic group is a fluorenyl group. A divalent non-aromatic condensed polycyclic group used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed polycyclic group. 
     A monovalent non-aromatic condensed heteropolycyclic group used herein refers to a monovalent group that has two or more rings condensed to each other, has at least one hetero atom selected from N, O P, and S as a ring-forming atom, and carbon atoms as the remaining ring-forming atoms, and does not have overall aromaticity. Non-limiting example of the monovalent non-aromatic condensed heteropolycyclic group is a carbazolyl group. A divalent non-aromatic condensed heteropolycyclic group used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed heteropolycyclic group. 
     A C 6 -C 60  arene group used herein refers to a carbocyclic aromatic system that has 6 to 60 carbon atoms. When the C 6 -C 60  arene group includes two or more rings, the rings may be respectively fused to each other. 
     A C 1 -C 60  heteroarene group used herein refers to a carbocyclic aromatic system that has at least one hetero atom selected from N, O, P and S as a ring-forming atom, and 1 to 60 carbon atoms. When the C 1 -C 60  heteroarene group includes two or more rings, the rings may be respectively fused to each other. 
     The term “Ph” used herein refers to a phenyl group, the term “Me” used herein refers to a methyl group, the term “Et” used herein refers to an ethyl group, and the term “ter-Bu” or “Bu t ” used herein refers to a tert-butyl group. 
     EXAMPLE 
     Example 1-1 
     A glass substrate (a product of Corning Co., Ltd) with an ITO anode layer having a thickness of 15 Ω/cm2 (1200 Å) thereon was cut to a size of 50 mm×50 mm×0.7 mm, and then, sonicated by using isopropyl alcohol and pure water, each for 5 minutes, and cleaned by exposing to ultraviolet rays for 30 minutes, and then ozone, and the resulting ITO glass substrate was mounted on a vacuum deposition apparatus. 
     HT13 was vacuum deposited on the ITO anode layer to form a hole injection layer having a thickness of 500 Å, and then HT3 as a hole transport compound was vacuum deposited to form a hole transport layer having a thickness of 450 Å, thereby forming a hole transport region. 
     Compound H1 (host) and FD1 (dopant) were co-deposited on the hole transport region in a volume ratio of 95:5 to form an emission layer having a thickness of 300 Å. 
     Next, Compound E1 was deposited on the emission layer to form a buffer layer having a thickness of 100 Å, and then Alq 3  was deposited on the buffer layer to form an electron transport layer having a thickness of 150 Å. LiF was further deposited on the electron transport layer to form an electron injection layer having a thickness of 5 Å, thereby forming an electron transport region. Then, Al was vacuum deposited to form a cathode having a thickness of 1500 Å, thereby manufacturing an organic light-emitting device. 
     Examples 1-2 to 1-28 and Comparative Examples 1-1 to 1-5 
     Organic light-emitting devices were manufactured in the same (or substantially the same) manner as in Example 1-1, except that, in forming respective emission layers and buffer layers, compounds in Table 1 were used instead of Compounds H1 and E1. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Electron 
               
               
                   
                   
                 Emission 
                 Buffer 
                 transport 
               
               
                   
                 Example 
                 layer host 
                 layer 
                 layer 
               
               
                   
                   
               
             
            
               
                   
                 Example 
                 H1 
                 E1 
                 Alq 3   
               
               
                   
                 1-1 
               
               
                   
                 Example 
                 H1 
                 E2 
                 Alq 3   
               
               
                   
                 1-2 
               
               
                   
                 Example 
                 H1 
                 E3 
                 Alq 3   
               
               
                   
                 1-3 
               
               
                   
                 Example 
                 H1 
                 E4 
                 Alq 3   
               
               
                   
                 1-4 
               
               
                   
                 Example 
                 H1 
                 E5 
                 Alq 3   
               
               
                   
                 1-5 
               
               
                   
                 Example 
                 H1 
                 E6 
                 Alq 3   
               
               
                   
                 1-6 
               
               
                   
                 Example 
                 H1 
                 E7 
                 Alq 3   
               
               
                   
                 1-7 
               
               
                   
                 Example 
                 H1 
                 E8 
                 Alq 3   
               
               
                   
                 1-8 
               
               
                   
                 Example 
                 H1 
                 E9 
                 Alq 3   
               
               
                   
                 1-9 
               
               
                   
                 Example 
                 H1 
                 E10 
                 Alq 3   
               
               
                   
                 1-10 
               
               
                   
                 Example 
                 H1 
                 E11 
                 Alq 3   
               
               
                   
                 1-11 
               
               
                   
                 Example 
                 H1 
                 E12 
                 Alq 3   
               
               
                   
                 1-12 
               
               
                   
                 Example 
                 H2 
                 E1 
                 Alq 3   
               
               
                   
                 1-13 
               
               
                   
                 Example 
                 H3 
                 E1 
                 Alq 3   
               
               
                   
                 1-14 
               
               
                   
                 Example 
                 H4 
                 E1 
                 Alq 3   
               
               
                   
                 1-15 
               
               
                   
                 Example 
                 H5 
                 E1 
                 Alq 3   
               
               
                   
                 1-16 
               
               
                   
                 Example 
                 H6 
                 E1 
                 Alq 3   
               
               
                   
                 1-17 
               
               
                   
                 Example 
                 H7 
                 E1 
                 Alq 3   
               
               
                   
                 1-18 
               
               
                   
                 Example 
                 H8 
                 E1 
                 Alq 3   
               
               
                   
                 1-19 
               
               
                   
                 Example 
                 H9 
                 E1 
                 Alq 3   
               
               
                   
                 1-20 
               
               
                   
                 Example 
                 H2 
                 E3 
                 Alq 3   
               
               
                   
                 1-21 
               
               
                   
                 Example 
                 H4 
                 E3 
                 Alq 3   
               
               
                   
                 1-22 
               
               
                   
                 Example 
                 H5 
                 E3 
                 Alq 3   
               
               
                   
                 1-23 
               
               
                   
                 Example 
                 H7 
                 E3 
                 Alq 3   
               
               
                   
                 1-24 
               
               
                   
                 Example 
                 H2 
                 E5 
                 Alq 3   
               
               
                   
                 1-25 
               
               
                   
                 Example 
                 H4 
                 E5 
                 Alq 3   
               
               
                   
                 1-26 
               
               
                   
                 Example 
                 H5 
                 E5 
                 Alq 3   
               
               
                   
                 1-27 
               
               
                   
                 Example 
                 H7 
                 E5 
                 Alq 3   
               
               
                   
                 1-28 
               
               
                   
                 Example 
                 H2 
                 E7 
                 Alq 3   
               
               
                   
                 1-29 
               
               
                   
                 Example 
                 H4 
                 E7 
                 Alq 3   
               
               
                   
                 1-30 
               
               
                   
                 Example 
                 H5 
                 E7 
                 Alq 3   
               
               
                   
                 1-31 
               
               
                   
                 Example 
                 H7 
                 E7 
                 Alq 3   
               
               
                   
                 1-32 
               
               
                   
                 Example 
                 H2 
                 E9 
                 Alq 3   
               
               
                   
                 1-33 
               
               
                   
                 Example 
                 H4 
                 E9 
                 Alq 3   
               
               
                   
                 1-34 
               
               
                   
                 Example 
                 H5 
                 E9 
                 Alq 3   
               
               
                   
                 1-35 
               
               
                   
                 Example 
                 H7 
                 E9 
                 Alq 3   
               
               
                   
                 1-36 
               
               
                   
                 Comparative 
                 Compound1 
                 E1 
                 Alq 3   
               
               
                   
                 Example 1-1 
               
               
                   
                 Comparative 
                 Compound2 
                 E1 
                 Alq 3   
               
               
                   
                 Example 1-2 
               
               
                   
                 Comparative 
                 Compound1 
                 Compound 
                 Alq 3   
               
               
                   
                 Example 1-3 
                   
                 A 
               
               
                   
                 Comparative 
                 Compound2 
                 Compound 
                 Alq 3   
               
               
                   
                 Example 1-4 
                   
                 A 
               
               
                   
                 Comparative 
                 Compound 
                 Compound 
                 Alq 3   
               
               
                   
                 Example1-5 
                 B 
                 C 
               
               
                   
                   
                   
                   
                 Alq 3   
               
               
                   
                   
               
            
           
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Example 2-1 
     A glass substrate (a product of Corning Co., Ltd) with an ITO anode layer having a thickness of 15 Ω/cm2 (1200 Å) thereon was cut to a size of 50 mm×50 mm×0.7 mm, and then, sonicated by using isopropyl alcohol and pure water, each for 5 minutes, and cleaned by exposing to ultraviolet rays for 30 minutes, and then ozone, and the resulting ITO glass substrate was mounted on a vacuum deposition apparatus. 
     HT13 was vacuum deposited on the ITO anode layer to form a hole injection layer having a thickness of 500 Å, and then HT3 as a hole transport compound was vacuum deposited to form a hole transport layer having a thickness of 450 Å, thereby forming a hole transport region. 
     Compound H1 (host) and FD1 (dopant) were co-deposited on the hole transport region in a volume ratio of 95:5 to form an emission layer having a thickness of 300 Å. 
     Next, Compound E1 was deposited on the emission layer to form a buffer layer having a thickness of 100 Å, and then Bphen and Liq were co-deposited on the buffer layer in a volume ratio of 50:50 to form an electron transport layer having a thickness of 150 Å. LiF was further deposited on the electron transport layer to form an electron injection layer having a thickness of 5 Å, thereby forming an electron transport region, and Al was vacuum deposited thereon to form a cathode having a thickness of 1500 Å, thereby manufacturing an organic light-emitting device. 
     Example 2-2 to 2-28 and Comparative Example 2-1 to 2-5 
     Organic light-emitting devices were manufactured in the same (or substantially the same) manner as in Example 2-1, except that, in forming respective emission layers and buffer layers, compounds in Table 2 were used instead of Compounds H1 and E1. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Electron 
               
               
                   
                   
                 Emission 
                 Buffer 
                 transport 
               
               
                   
                 Example 
                 layer host 
                 layer 
                 layer 
               
               
                   
                   
               
             
            
               
                   
                 Example 
                 H1 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-1 
               
               
                   
                 Example 
                 H1 
                 E2 
                 Bphen:Liq 
               
               
                   
                 2-2 
               
               
                   
                 Example 
                 H1 
                 E3 
                 Bphen:Liq 
               
               
                   
                 2-3 
               
               
                   
                 Example 
                 H1 
                 E4 
                 Bphen:Liq 
               
               
                   
                 2-4 
               
               
                   
                 Example 
                 H1 
                 E5 
                 Bphen:Liq 
               
               
                   
                 2-5 
               
               
                   
                 Example 
                 H1 
                 E6 
                 Bphen:Liq 
               
               
                   
                 2-6 
               
               
                   
                 Example 
                 H1 
                 E7 
                 Bphen:Liq 
               
               
                   
                 2-7 
               
               
                   
                 Example 
                 H1 
                 E8 
                 Bphen:Liq 
               
               
                   
                 2-8 
               
               
                   
                 Example 
                 H1 
                 E9 
                 Bphen:Liq 
               
               
                   
                 2-9 
               
               
                   
                 Example 
                 H1 
                 E10 
                 Bphen:Liq 
               
               
                   
                 2-10 
               
               
                   
                 Example 
                 H1 
                 E11 
                 Bphen:Liq 
               
               
                   
                 2-11 
               
               
                   
                 Example 
                 H1 
                 E12 
                 Bphen:Liq 
               
               
                   
                 2-12 
               
               
                   
                 Example 
                 H2 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-13 
               
               
                   
                 Example 
                 H3 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-14 
               
               
                   
                 Example 
                 H4 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-15 
               
               
                   
                 Example 
                 H5 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-16 
               
               
                   
                 Example 
                 H6 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-17 
               
               
                   
                 Example 
                 H7 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-18 
               
               
                   
                 Example 
                 H8 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-19 
               
               
                   
                 Example 
                 H9 
                 E1 
                 Bphen:Liq 
               
               
                   
                 2-20 
               
               
                   
                 Example 
                 H2 
                 E3 
                 Bphen:Liq 
               
               
                   
                 2-21 
               
               
                   
                 Example 
                 H4 
                 E3 
                 Bphen:Liq 
               
               
                   
                 2-22 
               
               
                   
                 Example 
                 H5 
                 E3 
                 Bphen:Liq 
               
               
                   
                 2-23 
               
               
                   
                 Example 
                 H7 
                 E3 
                 Bphen:Liq 
               
               
                   
                 2-24 
               
               
                   
                 Example 
                 H2 
                 E5 
                 Bphen:Liq 
               
               
                   
                 2-25 
               
               
                   
                 Example 
                 H4 
                 E5 
                 Bphen:Liq 
               
               
                   
                 2-26 
               
               
                   
                 Example 
                 H5 
                 E5 
                 Bphen:Liq 
               
               
                   
                 2-27 
               
               
                   
                 Example 
                 H7 
                 E5 
                 Bphen:Liq 
               
               
                   
                 2-28 
               
               
                   
                 Example 
                 H2 
                 E7 
                 Bphen:Liq 
               
               
                   
                 2-29 
               
               
                   
                 Example 
                 H4 
                 E7 
                 Bphen:Liq 
               
               
                   
                 2-30 
               
               
                   
                 Example 
                 H5 
                 E7 
                 Bphen:Liq 
               
               
                   
                 2-31 
               
               
                   
                 Example 
                 H7 
                 E7 
                 Bphen:Liq 
               
               
                   
                 2-32 
               
               
                   
                 Example 
                 H2 
                 E9 
                 Bphen:Liq 
               
               
                   
                 2-33 
               
               
                   
                 Example 
                 H4 
                 E9 
                 Bphen:Liq 
               
               
                   
                 2-34 
               
               
                   
                 Example 
                 H5 
                 E9 
                 Bphen:Liq 
               
               
                   
                 2-35 
               
               
                   
                 Example 
                 H7 
                 E9 
                 Bphen:Liq 
               
               
                   
                 2-36 
               
               
                   
                 Comparative 
                 Compound1 
                 E1 
                 Bphen:Liq 
               
               
                   
                 Example 2-1 
               
               
                   
                 Comparative 
                 Compound2 
                 E1 
                 Bphen:Liq 
               
               
                   
                 Example 2-2 
               
               
                   
                 Comparative 
                 Compound1 
                 Compound 
                 Bphen:Liq 
               
               
                   
                 Example 2-3 
                   
                 A 
               
               
                   
                 Comparative 
                 Compound2 
                 Compound 
                 Bphen:Liq 
               
               
                   
                 Example 2-4 
                   
                 A 
               
               
                   
                 Comparative 
                 Compound 
                 Compound 
                 Bphen:Liq 
               
               
                   
                 Example 2-5 
                 B 
                 C 
               
               
                   
                   
                   
                   
                 Bphen:Liq 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Evaluation Example 
     In Examples 1-1 to 1-36 and 2-1 to 2-36, and Comparative Examples 1-1 to 1-5 and 2-1 to 2-5, efficiency (at a current density of 10 mA/cm 2 ) and lifespan T 90  (at a current density of 50 mA/cm 2 ) of each of the organic light-emitting devices were measured by using a Keithley 2400 SourceMeter® and a Minolta Cs-1000 Å Spectroradiometer. T 90  denotes an amount of time it took for the luminance of the organic light-emitting device to decrease to 90% of an initial luminance. The results are shown in Tables 3 and 4. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                   
                 Electron 
                   
                   
               
               
                   
                 Emission 
                 Buffer 
                 transport 
                 Efficiency 
                 T 90   
               
               
                 Example 
                 layer host  
                 layer 
                 layer 
                 (cd/A) 
                 (hour) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 1-1 
                 H1 
                 E1 
                 Alq 3   
                 5.4 
                 140 
               
               
                 Example 1-2 
                 H1 
                 E2 
                 Alq 3   
                 5.5 
                 130 
               
               
                 Example 1-3 
                 H1 
                 E3 
                 Alq 3   
                 5.5 
                 140 
               
               
                 Example 1-4 
                 H1 
                 E4 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-5 
                 H1 
                 E5 
                 Alq 3   
                 5.3 
                 130 
               
               
                 Example 1-6 
                 H1 
                 E6 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-7 
                 H1 
                 E7 
                 Alq 3   
                 5.5 
                 120 
               
               
                 Example 1-8 
                 H1 
                 E8 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-9 
                 H1 
                 E9 
                 Alq 3   
                 5.4 
                 140 
               
               
                 Example 1-10 
                 H1 
                 E10 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-11 
                 H1 
                 E11 
                 Alq 3   
                 5.5 
                 120 
               
               
                 Example 1-12 
                 H1 
                 E12 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-13 
                 H2 
                 E1 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-14 
                 H3 
                 E1 
                 Alq 3   
                 5.3 
                 140 
               
               
                 Example 1-15 
                 H4 
                 E1 
                 Alq 3   
                 5.5 
                 120 
               
               
                 Example 1-16 
                 H5 
                 E1 
                 Alq 3   
                 5.3 
                 130 
               
               
                 Example 1-17 
                 H6 
                 E1 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-18 
                 H7 
                 E1 
                 Alq 3   
                 5.4 
                 140 
               
               
                 Example 1-19 
                 H8 
                 E1 
                 Alq 3   
                 5.3 
                 150 
               
               
                 Example 1-20 
                 H9 
                 E1 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-21 
                 H2 
                 E3 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-22 
                 H4 
                 E3 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-23 
                 H5 
                 E3 
                 Alq 3   
                 5.3 
                 140 
               
               
                 Example 1-24 
                 H7 
                 E3 
                 Alq 3   
                 5.3 
                 140 
               
               
                 Example 1-25 
                 H2 
                 E5 
                 Alq 3   
                 5.3 
                 120 
               
               
                 Example 1-26 
                 H4 
                 E5 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-27 
                 H5 
                 E5 
                 Alq 3   
                 5.3 
                 130 
               
               
                 Example 1-28 
                 H7 
                 E5 
                 Alq 3   
                 5.2 
                 120 
               
               
                 Example 1-29 
                 H2 
                 E7 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-30 
                 H4 
                 E7 
                 Alq 3   
                 5.5 
                 120 
               
               
                 Example 1-31 
                 H5 
                 E7 
                 Alq 3   
                 5.4 
                 130 
               
               
                 Example 1-32 
                 H7 
                 E7 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-33 
                 H2 
                 E9 
                 Alq 3   
                 5.4 
                 120 
               
               
                 Example 1-34 
                 H4 
                 E9 
                 Alq 3   
                 5.6 
                 120 
               
               
                 Example 1-35 
                 H5 
                 E9 
                 Alq 3   
                 5.5 
                 130 
               
               
                 Example 1-36 
                 H7 
                 E9 
                 Alq 3   
                 5.3 
                 110 
               
               
                 Comparative 
                 Com- 
                 E1 
                 Alq 3   
                 4.6 
                 50 
               
               
                 Example 1-1 
                 pound1 
                   
                   
                   
                   
               
               
                 Comparative 
                 Com- 
                 E1 
                 Alq 3   
                 4.5 
                 60 
               
               
                 Example 1-2 
                 pound2 
                   
                   
                   
                   
               
               
                 Comparative 
                 Com- 
                 Com- 
                 Alq 3   
                 4.5 
                 60 
               
               
                 Example 1-3 
                 pound1  
                 pound A 
                   
                   
                   
               
               
                 Comparative 
                 Com- 
                 Com- 
                 Alq 3   
                 4.6 
                 60 
               
               
                 Example 1-4 
                 pound2 
                 pound A 
                   
                   
                   
               
               
                 Comparative 
                 Com- 
                 Com- 
                 Alq 3   
                 4.9 
                 90 
               
               
                 Example 1-5 
                 pound B 
                 pound C 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                   
                   
                   
                 Electron 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Emission 
                 Buffer 
                 transport 
                 Efficiency 
                 T 90   
               
               
                 Example 
                 layer host 
                 layer 
                 layer 
                 (cd/A) 
                 (hour) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 2-1 
                 H1 
                 E1 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-2 
                 H1 
                 E2 
                 Bphen:Liq 
                 5.4 
                 140 
               
               
                 Example 2-3 
                 H1 
                 E3 
                 Bphen:Liq 
                 5.5 
                 150 
               
               
                 Example 2-4 
                 H1 
                 E4 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-5 
                 H1 
                 E5 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-6 
                 H1 
                 E6 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-7 
                 H1 
                 E7 
                 Bphen:Liq 
                 5.4 
                 140 
               
               
                 Example 2-8 
                 H1 
                 E8 
                 Bphen:Liq 
                 5.3 
                 130 
               
               
                 Example 2-9 
                 H1 
                 E9 
                 Bphen:Liq 
                 5.4 
                 140 
               
               
                 Example 2-10 
                 H1 
                 E10 
                 Bphen:Liq 
                 5.3 
                 130 
               
               
                 Example 2-11 
                 H1 
                 E11 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-12 
                 H1 
                 E12 
                 Bphen:Liq 
                 5.4 
                 120 
               
               
                 Example 2-13 
                 H2 
                 E1 
                 Bphen:Liq 
                 5.2 
                 130 
               
               
                 Example 2-14 
                 H3 
                 E1 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-15 
                 H4 
                 E1 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-16 
                 H5 
                 E1 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-17 
                 H6 
                 E1 
                 Bphen:Liq 
                 5.2 
                 130 
               
               
                 Example 2-18 
                 H7 
                 E1 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-19 
                 H8 
                 E1 
                 Bphen:Liq 
                 5.2 
                 150 
               
               
                 Example 2-20 
                 H9 
                 E1 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-21 
                 H2 
                 E3 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-22 
                 H4 
                 E3 
                 Bphen:Liq 
                 5.5 
                 140 
               
               
                 Example 2-23 
                 H5 
                 E3 
                 Bphen:Liq 
                 5.4 
                 150 
               
               
                 Example 2-24 
                 H7 
                 E3 
                 Bphen:Liq 
                 5.4 
                 140 
               
               
                 Example 2-25 
                 H2 
                 E5 
                 Bphen:Liq 
                 5.3 
                 130 
               
               
                 Example 2-26 
                 H4 
                 E5 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-27 
                 H5 
                 E5 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-28 
                 H7 
                 E5 
                 Bphen:Liq 
                 5.2 
                 120 
               
               
                 Example 2-29 
                 H2 
                 E7 
                 Bphen:Liq 
                 5.3 
                 140 
               
               
                 Example 2-30 
                 H4 
                 E7 
                 Bphen:Liq 
                 5.5 
                 120 
               
               
                 Example 2-31 
                 H5 
                 E7 
                 Bphen:Liq 
                 5.3 
                 130 
               
               
                 Example 2-32 
                 H7 
                 E7 
                 Bphen:Liq 
                 5.2 
                 130 
               
               
                 Example 2-33 
                 H2 
                 E9 
                 Bphen:Liq 
                 5.3 
                 130 
               
               
                 Example 2-34 
                 H4 
                 E9 
                 Bphen:Liq 
                 5.5 
                 120 
               
               
                 Example 2-35 
                 H5 
                 E9 
                 Bphen:Liq 
                 5.4 
                 130 
               
               
                 Example 2-36 
                 H7 
                 E9 
                 Bphen:Liq 
                 5.3 
                 120 
               
               
                 Comparative 
                 Compound1 
                 E1 
                 Bphen:Liq 
                 4.6 
                 50 
               
               
                 Example 2-1 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 Compound2 
                 E1 
                 Bphen:Liq 
                 4.5 
                 60 
               
               
                 Example 2-2 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 Compound1 
                 Compound 
                 Bphen:Liq 
                 4.5 
                 50 
               
               
                 Example 2-3 
                   
                 A 
                   
                   
                   
               
               
                 Comparative 
                 Compound2 
                 Compound 
                 Bphen:Liq 
                 4.6 
                 50 
               
               
                 Example 2-4 
                   
                 A 
                   
                   
                   
               
               
                 Comparative  
                 Compound 
                 Compound  
                 Bphen:Liq 
                 4.9 
                 100 
               
               
                 Example 2-5 
                 B 
                 C 
               
               
                   
               
            
           
         
       
     
     As illustrated in Table 3, the organic light-emitting devices in Examples 1-1 to 1-36 exhibited better efficiency and longer lifespan than the organic light-emitting devices in Comparative Examples 1-1 to 1-5. 
     As illustrated in Table 4, the organic light-emitting devices in Examples 2-1 to 2-36 exhibited better efficiency and longer lifespan than the organic light-emitting devices in Comparative Examples 2-1 to 2-5. 
     As described above, according to one or more embodiments of the present invention, an organic light-emitting device including the first material of Formula 1 in the emission layer and the second material of Formula 2 in the electron transport region may have excellent efficiency and long lifespan. 
     It should be understood that the embodiments described therein 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. 
     In addition, as used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively. Also, the term “exemplary” is intended to refer to an example or illustration. 
     As used herein, the term “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. 
     Also, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of “1.0 to 10.0” is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. All such ranges are intended to be inherently described in this specification such that amending to expressly recite any such subranges would comply with the requirements of 35 U.S.C. §1 12, first paragraph, and 35 U.S.C. §132(a). 
     While one or more embodiments of the present invention have been described with reference to the drawing, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims and equivalents thereof.