Patent Publication Number: US-2022216434-A1

Title: Light-emitting device and an electronic apparatus comprising the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2020-0181184, filed on Dec. 22, 2020, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     Field 
     Embodiments of the invention relate generally to display devices, and more particularly, to a light-emitting device and an electronic apparatus including the same. 
     Discussion of the Background 
     Organic light-emitting devices (OLEDs) are self-emission devices that, as compared with devices of the related art, have wide viewing angles, high contrast ratios, short response times, and excellent characteristics in terms of luminance, driving voltage, and response speed, and produce full-color images. 
     OLEDs may include a first electrode located on a substrate, and a hole transport region, an emission layer, an electron transport region, and a second electrode sequentially stacked on the first electrode. Holes provided from the first electrode 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, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state, thereby generating light. 
     The above information disclosed in this Background section is only for understanding of the background of the inventive concepts, and, therefore, it may contain information that does not constitute prior art. 
     SUMMARY 
     Light-emitting devices and electronic apparatuses including the same constructed according to the principles and illustrative implementations of the invention include a spacing layer that prevents deterioration of an emission layer, and therefore have improved lifespan characteristics. For example, a spacing layer in an emission area of an emission layer may provide a distance between excitons, which thus reduces or prevents deterioration of the material of the emission layer by preventing overcrowding of emission zones where an actual emission phenomenon occurs. 
     Additional features of the inventive concepts will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the inventive concepts. 
     According to one aspect of the invention, a touch sensor for a display device, includes: a light-emitting device having a first electrode, a second electrode facing the first electrode, an interlayer which is between the first electrode and the second electrode and includes an emission area, wherein the emission area includes: an emission layer including a host and a dopant; and a first layer including a first compound, wherein the host and the first compound are different materials, and a bandgap of the first compound is about 3.5 eV or more. 
     The lowest excitation triplet energy level of the first compound may be about 2.8 eV or more. 
     The first compound may include a compound represented by one of Formulae 1 to 3, as defined herein. 
     The variables L 10 , L 20 , L 30 , L 40 , L 50 , and L 60  may each be, independently from one another, a group represented by one of Formulae 3-1 to 3-26, as defined herein. 
     The first compound may include at least one of Compounds 1 to 49, as defined herein. 
     The first compound may be a spacing compound, and the first layer may be a spacing layer consisting of the spacing compound. 
     The first layer may have a thickness of about 1 nm to about 10 nm. 
     The emission area may include two or more emission layers, and the first layer may be between the two or more emission layers. 
     The first layer may include a spacing layer, and the emission area may include one to five spacing layers. 
     The host may include a hole transport host, an electron transport host, a bipolar host, or any combination thereof. 
     The host may be a compound represented by one of Formulae 311-1 to 311-5, 312-1, 312-2, and 313, or a combination thereof, as defined herein. 
     The host may include at least one of Compounds H-01 to H-21 and E-01 to E-18, as described herein. 
     The dopant may include a phosphorescent dopant and a delayed fluorescent dopant. 
     The phosphorescent dopant may include a compound represented by Formula 411 or 412, as defined herein, and the delayed fluorescent dopant may include a compound represented by Formula 511 or 512, as defined herein. 
     The phosphorescent dopant may include at least one of Compounds S-1 to S-36, and S-101 to S-184, as described herein, and the delayed fluorescent dopant may include at least one of Compounds D-01 to D-26, DA-01 to DA-30, and DF1 to DF10, as described herein. 
     The first electrode of the light-emitting device may include an anode, the second electrode of the light-emitting device may include a cathode, the interlayer may further include a hole transport region between the first electrode and the emission area and an electron transport region between the emission area and the second electrode, the hole transport region may include a hole injection layer, a hole transport layer, an emission auxiliary layer, an electron blocking layer, or any combination thereof, and the electron transport region may include a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     The first layer may not directly contact the electron transport region. 
     The first layer may be closer to the hole transport region than the electron transport region. 
     An electronic apparatus may include the light-emitting device, as described above. 
     The electronic apparatus may further include a thin-film transistor, wherein the thin-film transistor may include a source electrode and a drain electrode, and the first electrode of the light-emitting device may be electrically connected to the source electrode or the drain electrode. 
     It is to be understood that both the foregoing general description and the following detailed description are illustrative and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate illustrative embodiments of the invention, and together with the description serve to explain the inventive concepts. 
         FIG. 1  is a schematic cross-sectional view of an embodiment of a light-emitting device constructed according to the principles of the invention. 
         FIG. 2  is a cross-sectional view of an embodiment of a light-emitting apparatus including a light-emitting device constructed according to the principles of the invention. 
         FIG. 3  is a cross-sectional view of another embodiment of a light-emitting apparatus including a light-emitting device constructed according to the principles of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various embodiments or implementations of the invention. As used herein “embodiments” and “implementations” are interchangeable words that are non-limiting examples of devices or methods employing one or more of the inventive concepts disclosed herein. It is apparent, however, that various embodiments may be practiced without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring various embodiments. Further, various embodiments may be different, but do not have to be exclusive. For example, specific shapes, configurations, and characteristics of an embodiment may be used or implemented in another embodiment without departing from the inventive concepts. 
     Unless otherwise specified, the illustrated embodiments are to be understood as providing illustrative features of varying detail of some ways in which the inventive concepts may be implemented in practice. Therefore, unless otherwise specified, the features, components, modules, layers, films, panels, regions, and/or aspects, etc. (hereinafter individually or collectively referred to as “elements”), of the various embodiments may be otherwise combined, separated, interchanged, and/or rearranged without departing from the inventive concepts. 
     The use of cross-hatching and/or shading in the accompanying drawings is generally provided to clarify boundaries between adjacent elements. As such, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, dimensions, proportions, commonalities between illustrated elements, and/or any other characteristic, attribute, property, etc., of the elements, unless specified. Further, in the accompanying drawings, the size and relative sizes of elements may be exaggerated for clarity and/or descriptive purposes. When an embodiment may be implemented differently, a specific process order may be performed differently from the described order. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to the described order. Also, like reference numerals denote like elements. Thus, components of one illustrated embodiment that are the same or correspond to components of another illustrated embodiment may have the same reference numeral, and redundant explanations are omitted to avoid redundancy. 
     When an element, such as a layer, is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it may be directly on, connected to, or coupled to the other element or layer or intervening elements or layers may be present. When, however, an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. To this end, the term “connected” may refer to physical, electrical, and/or fluid connection, with or without intervening elements. Further, the D1-axis, the D2-axis, and the D3-axis are not limited to three axes of a rectangular coordinate system, such as the x, y, and z-axes, and may be interpreted in a broader sense. For example, the D1-axis, the D2-axis, and the D3-axis may be perpendicular to one another, or may represent different directions that are not perpendicular to one another. For the purposes of this disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be construed as X only, Y only, Z only, or any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms “first,” “second,” etc. may be used herein to describe various types of elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the teachings of the disclosure. 
     Spatially relative terms, such as “beneath,” “below,” “under,” “lower,” “above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), and the like, may be used herein for descriptive purposes, and, thereby, to describe one elements relationship to another element(s) as illustrated in the drawings. Spatially relative terms are intended to encompass different orientations of an apparatus in use, operation, and/or manufacture in addition to the orientation depicted in the drawings. For example, if the apparatus in the drawings is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and, as such, the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, the singular forms, “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Moreover, the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It is also noted that, as used herein, the terms “substantially,” “about,” and other similar terms, are used as terms of approximation and not as terms of degree, and, as such, are utilized to account for inherent deviations in measured, calculated, and/or provided values that would be recognized by one of ordinary skill in the art. 
     Various embodiments are described herein with reference to sectional and/or exploded illustrations that are schematic illustrations of idealized embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments disclosed herein should not necessarily be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. In this manner, regions illustrated in the drawings may be schematic in nature and the shapes of these regions may not reflect actual shapes of regions of a device and, as such, are not necessarily intended to be limiting. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is a part. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
     A light-emitting device according to an embodiment may include: a first electrode; a second electrode facing the first electrode; an interlayer which is located between the first electrode and the second electrode and may include an emission area. The emission area may include: an emission layer including a host and a dopant; and a first layer in the form of spacing layer including a first compound in the form of a spacing compound. The light-emitting device according to an embodiment may, by including a spacing layer in an emission area, provide a distance between excitons in the emission area, and thus reduce or prevent deterioration of the material of the emission layer by preventing overcrowding of emission zones where an actual emission phenomenon occurs. In an embodiment, the host and the spacing compound may be different materials. In an embodiment, the band gap of the spacing compound may be about 3.5 eV or more. 
     The spacing compound may have a band gap of about 3.5 eV or more, and in this case, the spacing compound may be referred to as a wide band gap compound. In an embodiment, the spacing compound may have a minimum excitation triplet energy (T1 energy) of about 2.8 eV or more. As described herein, the lowest excitation triplet energy, for example, the “lowest excitation triplet energy level,” is a sample prepared by depositing 1,000 Å of a compound on a quartz substrate, and by obtaining a photoluminescence spectrum at a temperature of 4K in regard to the above sample, the first peak (a peak having the shortest wavelength) of the photoluminescence spectrum is analyzed, and the lowest excitation triplet energy may be calculated therefrom. 
     When the spacing compound satisfies the above-described energy characteristics, the distribution of excitons is spatially lowered in the emission area of the light-emitting device to effectively prevent overcrowding of excitons, and even within the emission area, the places where actual emission phenomenon occur may be evenly distributed. In addition, when the spacing compound is a material having a triplet energy of about 2.8 eV or more, the triplet exciton loss is suppressed, so that it is suitably applied to a next-generation deep blue light-emitting device, thereby preventing a decrease in efficiency. 
     In an embodiment, the spacing compound may include a compound represented by one of Formulae 1 to 3: 
     
       
         
         
             
             
         
       
     
     In Formulae 1 to 3, 
     Y 1  may be a single bond, N[(L 30 ) a30 -(R 30 ) b30 ], C[(L 30 ) a30 -(R 30 ) b30 ][(L 40 ) a40 -(R 40 ) b40 ], Si[(L 30 ) a30 -(R 30 ) b30 ][(L 40 ) a40 -(R 40 ) b40 ], O, or S, 
     Y 2  may be N[(L 50 ) a50 -(R 50 ) b50 ], C[(L 50 ) a50 -(R 50 ) b50 ][(L 60 ) a60 -(R 60 ) b60 ], Si[(L 50 ) a50 -(R 50 ) b50 ][(L 60 ) a60 -(R 60 ) b60 ], O, or S, 
     X 1  may be N or C[(L 40 ) a40 -(R 40 ) b40 ], 
     X 2  may be N or C[(L 50 ) a50 -(R 50 ) b50 ], 
     X 3  may be N or C[(L 60 ) a60 -(R 60 ) b60 ], 
     L 10 , L 20 , L 30 , L 40 , L 50 , and L 60  may each independently be a single bond, a C 1 -C 20  alkylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkenylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkynylene group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkylene group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkenylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkenylene group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroarylene group unsubstituted or substituted with at least one R 10a , a divalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , or a divalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , 
     a10, a20, a30, a40, a50 and a60 may each independently be 0, 1, 2, or 3, R 10 , R 20 , R 30 , R 40 , R 50 , and R 60  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkyl group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkenyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkenyl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryl group is unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryloxy group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroarylthio group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), —B(Q 1 )(Q 2 ), —N(Q 1 )(Q 2 ), —P(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O)(Q 1 ), —S(═O) 2 (Q 1 ), —P(═O)(Q 1 )(Q 2 ), or —P(═S)(Q 1 )(Q 2 ), 
     two or more neighboring groups selected from R 10 , R 20 , R 30 , R 40 , R 50 , and R 60  may optionally be linked to form a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     b10, b20, b30, b40, b50, and b60 may each independently be 1, 2, 3, 4, 5, 6, 7, or 8, 
     c10 and c20 may each independently be 1, 2, 3, or 4, 
     R 10a  may be: 
     deuterium (-D), —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof; 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, or a C 2 -C 60  heteroaryl alkyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 )(Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), 
     —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ), 
     wherein Q 1  to Q 3 , Q 11  to Q 13 , Q 21  to Q 23 , and Q 31  to Q 33  are each independently: hydrogen; deuterium; —F; —Cl; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 60  alkyl group; a C 2 -C 60  alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; or a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a biphenyl group, or any combination thereof. 
     In an embodiment, in Formula 3, at least one of X 1  to X 3  may be N, or at least one of L 10 , L 20 , L 30 , L 40 , L 50 , L 60 , R 10 , R 20 , R 30 , R 40 , R 50 , and R 60  may include a π electron-deficient nitrogen-containing ring. 
     In an embodiment, in Formulae 1 to 3, L 10 , L 20 , L 30 , L 40 , L 50 , and L 60  may each independently be a phenylene group, a pentalenylene group, an indenylene group, a naphthylene is group, an azulenylene group, a heptalenylene group, an indacenylene group, an acenaphthylene group, a fluorenylene group, a spiro-bifluorenylene group, a spiro-fluorene-benzofluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, a pentaphenylene group, a hexacenylene group, a pentacenylene group, a rubicenylene group, a coronenylene group, an ovalenylene group, a pyrrolylene group, a thiophenylene group, a furanylene group, an imidazolylene group, a pyrazolylene group, a thiazolylene group, an isothiazolylene group, an oxazolylene group, an isoxazolylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, an isoindolylene group, an indolylene group, an indazolylene group, a purinylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a phthalazinylene group, a naphthyridinylene group, a quinoxalinylene group, a quinazolinylene group, a cinnolinylene group, a carbazolylene group, a phenanthridinylene group, an acridinylene group, a phenanthrolinylene group, a phenazinylene group, a benzimidazolylene group, a benzofuranylene group, a benzothiophenylene group, a benzoisothiazolylene group, a benzoxazolylene group, an isobenzoxazolylene group, a triazolylene group, a tetrazolylene group, an oxadiazolylene group, a triazinylene group, a dibenzofuranylene group, a io dibenzothiophenylene group, dibenzosilolylene group, a benzocarbazolylene group, a dibenzocarbazolylene group, a thiadiazolylene group, an imidazopyridinylene group or an imidazopyrimidinylene group; or 
     a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an indacenylene group, an acenaphthylene is group, a fluorenylene group, a spiro-bifluorenylene group, a spiro-fluorene-benzofluorenylene group, a benzofluorenylene group, a dibenzofluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, a pentaphenylene group, a hexacenylene group, a pentacenylene group, a rubicenylene group, a coronenylene group, an ovalenylene group, a pyrrolylene group, a thiophenylene group, a furanylene group, an imidazolylene group, a pyrazolylene group, a thiazolylene group, an isothiazolylene group, an oxazolylene group, an isoxazolylene group, a pyridinylene group, a pyrazinylene group, a pyrimidinylene group, a pyridazinylene group, an isoindolylene group, an indolylene group, an indazolylene group, a purinylene group, a quinolinylene group, an isoquinolinylene group, a benzoquinolinylene group, a phthalazinylene group, a naphthyridinylene group, a quinoxalinylene group, a quinazolinylene group, a cinnolinylene group, a carbazolylene group, a phenanthridinylene group, an acridinylene group, a phenanthrolinylene group, a phenazinylene group, a benzimidazolylene group, a benzofuranylene group, a benzothiophenylene group, an isobenzothiazolylene group, a benzoxazolylene group, an isobenzoxazolylene group, a triazolylene group, a tetrazolylene group, an oxadiazolylene group, a triazinylene group, a dibenzofuranylene group, a dibenzothiophenylene group, a dibenzosilolylene group, a benzocarbazolylene group, a dibenzocarbazolylene group, a thiadiazolylene group, an imidazopyridinylene group, and an imidazopyrimidinylene group, each substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a biphenyl group, a terphenyl group, a pentalenyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptalenyl group, an indacenyl group, an acenaphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a naphthacenyl group, a picenyl group, a perylenyl group, a pentaphenyl group, a hexacenyl group, a pentacenyl group, a rubicenyl group, a coronenyl group, an ovalenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a 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, 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 dibenzosilolylene group, a benzocarbazolyl group, a dibenzocarbazolyl group, a thiadiazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), —P(═O)(Q 31 )(Q 32 ), or any combination thereof, 
     wherein Q 31  to Q 33  may each independently be a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, a phenyl group, a phenyl group substituted with a C 1 -C 10  alkyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, a pyrimidyl group, a triazinyl group, a quinolinyl group, or an isoquinolinyl group. 
     In an embodiment, L 10 , L 20 , L 30 , L 40 , L 50 , and L 60  may each independently be a group represented by one of Formulae 3-1 to 3-26: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 3-1 to 3-26, 
     Z 11  to Z 14  may each independently be 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 C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a spiro-bifluorenyl 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 dibenzofuranyl group, a dibenzothiophenyl group, a triazinyl group, a benzimidazolyl group, a phenanthrolinyl group, or —Si(Q 31 )(Q 32 )(Q 33 ), 
     Q 31  to Q 33  may each independently be a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group, and 
     d3 may be an integer from 0 to 3, 
     d4 may be an integer from 0 to 4, 
     d5 may be an integer from 0 to 5, 
     d6 may be an integer from 0 to 6, 
     d8 may be an integer from 0 to 8, and 
     * and *′ each indicate a binding site to a neighboring atom. 
     In an embodiment, a10, a20, a30, a40, a50, and a60 in Formulae 1 to 3 may each independently be 0, 1, or 2. 
     For example, a10, a20, a30, a40, a50, and a60 may each independently be 0 or 1. 
     In an embodiment, R 10 , R 20 , R 30 , R 40 , R 50,  and R 60  in Formulae 1 to 3 may each independently be: 
     hydrogen, deuterium, —F —Cl, —Br, —I, a hydroxyl group, or a cyano group; 
     a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, or a C 1 -C 20  alkoxy group; 
     a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, or a C 1 -C 20  alkoxy group, each substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), —P(═O)(Q 31 )(Q 32 ), or any combination thereof; 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a pentalenyl group, an indenyl group, a naphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a furanyl group, a thiophenyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a 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 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, a dibenzocarbazolyl group, an imidazopyridinyl group, or an imidazopyrimidinyl group; or 
     a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a pentalenyl group, an indenyl group, a naphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a furanyl group, a thiophenyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a 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 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, a dibenzocarbazolyl group, an imidazopyridinyl group, or an imidazopyrimidinyl group, each substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, a C 1 -C 20  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a pentalenyl group, an indenyl group, a naphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a furanyl group, a thiophenyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a 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 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, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), —P(═O)(Q 31 )(Q 32 ), or any combination thereof, 
     wherein Q 31  to Q 33  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a cyano group, a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, a C 1 -C 20  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 20  aryl group, a C 1 -C 20  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, a biphenyl group, or a terphenyl group. 
     In an embodiment, R 10 , R 20 , R 30 , R 40 , R 50 , and R 60  may each independently be a C 1 -C 20  alkyl group or C 1 -C 20  alkoxy group; or a group represented by one of Formulae 5-1 to 5-26 and Formulae 6-1 to 6-55, each substituted with hydrogen, deuterium, —F —Cl, —Br, —I, a hydroxyl group, a cyano group; deuterium, —F, —Cl, —Br, —I, a cyano group, a phenyl group, a biphenyl group, or any combination thereof. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 5-1 to 5-26 and 6-1 to 6-55, 
     Y 31  and Y 32  may each independently be O, S, C(Z 33 )(Z 34 ), N(Z 33 ), or Si(Z 33 )(Z 34 ), 
     Z 31  to Z 34  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a C 1 -C 20  alkyl group, a C 2 -C 20  alkenyl group, a C 2 -C 20  alkynyl group, a C 1 -C 20  alkoxy group, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a spiro-bifluorenyl group, a phenanthrenyl group, an anthracenyl group, a triphenylenyl group, a pyridinyl group, a pyrimidinyl group, a carbazolyl group, or a triazinyl group, 
     e2 may be 1 or 2, 
     e3 may be an integer from 1 to 3, 
     e4 may be an integer from 1 to 4, 
     e5 may be an integer from 1 to 5, 
     e6 may be an integer from 1 to 6, 
     e7 may be an integer from 1 to 7, 
     e9 may be an integer from 1 to 9, and 
     * indicates a binding site to a neighboring atom. 
     In an embodiment, b10, b20, b30, b40, b50, and b60 in Formulae 1 to 3 may each independently be 1, 2, 3, 4, 5, or 6. 
     For example, b10, b20, b30, b40, b50, and b60 may each independently be 1, 2, 3, or 4. 
     For example, b10, b20, b30, b40, b50, and b60 may each independently be 1 or 2. 
     For example, the spacing layer may include at least one of Compounds 1 to 49, but is not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The above-described spacing compounds have a large band gap and high triplet energy, thereby providing a sufficient distance between excitons in the emission area to reduce or prevent deterioration of the emission layer material. In an embodiment, the spacing compound may consist of C, H, Si, or a combination thereof In an embodiment, the spacing layer may consist of the spacing compound. For example, the spacing layer may be a non-doping layer that does not include materials other than the spacing compound. 
     In an embodiment, the spacing layer may have a thickness of about 0.1 nm to about 20 nm, for example, about 0.5 nm to about 15 nm, or about 1 nm to about 10 nm. In an embodiment the emission area may include two or more emission layers. In an embodiment, the spacing layer may be located between two emission layers. In an embodiment, the emission area may include one to five spacing layer(s). For example, the emission area may include a first emission layer, a first spacing layer, and a second emission layer, which are sequentially stacked. 
     For example, the emission area may include a first emission layer, a first spacing layer, a second emission layer, a second spacing layer, and a third emission layer, which are sequentially stacked. For example, the emission area may include a first emission layer, a first spacing layer, and a second emission layer, a second spacing layer, a third emission layer, a third spacing layer, and a fourth emission layer, which are sequentially stacked. The emission area io including one, two, or three spacing layers are described as examples above, but the stacked structure of the emission area is not limited thereto, and may further include emission layers and spacing layers. 
     In an embodiment, when the emission area includes two or more spacing layers, spacing compounds included in each spacing layer may be the same or different from each other. is In an embodiment, when the emission area includes two or more emission layers, hosts and/or dopants included in each emission layer may be the same or different from each other. In an embodiment, the host may include a hole transport host, an electron transport host, a bipolar host, or any combination thereof. 
     For example, the host may be a compound represented by one of Formulae 311-1 to 311-5, 312-1, 312-2, and 313, or a combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae 311-1 to 311-5, 312-1, 312-2, 313, and 313A, 
     Ar 301  may be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocylic group unsubstituted or substituted with at least one R 10a , 
     xb11 may be 1, 2, or 3, 
     A 301  to A 304  may each independently be a benzene group, a naphthalene group, a phenanthrene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene is group, an indene group, a fluorene group, a spiro-bifluorene group, a benzofluorene group, a dibenzofluorene group, an indole group, a pyridine group, a pyrimidine group, a carbazole group, a benzocarbazole group, a dibenzocarbazole group, a furan group, a benzofuran group, a dibenzofuran group, a naphthofuran group, a benzonaphthofuran group, a dinaphthofuran group, a thiophene group, a benzothiophene group, a dibenzothiophene group, a naphthothiophene group, a benzonaphthothiophene group, or a dinaphthothiophene group, 
     X 301  may be O, S, N-[(L 304 ) xb4 -R 304 ], C[(L 304 ) xb4 -R 304 ][(L 305 ) xb5 -R 305 ], or Si[(L 304 ) xb4 -R 304 ][(L 305 ) xb5 -R 305 ], 
     X 302 , Y 301 , and Y 302  may each independently be a single bond, O, S, N-[(L 305 ) xb5 -R 305 ], C[(L 304 ) xb4 -R 304 ][(L 305 ) xb5 -R 305 ], Si[(L 304 ) xb4 -R 304 ][(L 305 ) xb5 -R 305 ], or S(═O) 2 , 
     xb1 to xb5 may be 0, 1, 2, 3, 4, or 5, 
     xb6 may be 1, 2, 3, 4, or 5, 
     X 321  to X 327  may each independently be N or C[(L 324 ) xb24 -R 324 ], 
     xb21 to xb24 may each independently be 0, 1, 2, 3, 4, or 5, 
     A 31 , A 32 , and A 34  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 30  heterocyclic group, 
     A 33  may be a group represented by Formula 313A, 
     X 31  may be N[(L 335 ) xb35 -(R 335 )], O, S, Se, C[(L 335 ) xb35 —(R 335 )][(L 336 ) xb36 -(R 336 )], or Si[(L 335 ) xb35 -(R 335 )][(L 336 ) xb36 -(R 336 )], 
     xb31 to xb36 may each independently be 0, 1, 2, 3, 4, or 5, 
     xb42 to xb44 may each independently be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, 
     L 301  to L 306 , L 321  to L 324 , and L 331  to L 336  may each independently be a single bond, a C 1 -C 20  alkylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkenylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkynylene group unsubstituted or substituted with at least one R 10a , a C3-C 10  cycloalkylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkylene group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkenylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkenylene group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylene group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroarylene group unsubstituted or substituted with at least one R 10a , a divalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , or a divalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , R 301  to R 305 , R 311  to R 314 , R 321  to R 324 , and R 331  to R 336  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkyl group unsubstituted or is substituted with at least one R 10a , a C 1 -C 10  heterocycloalkyl group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkenyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkenyl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryloxy group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroarylthio group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 1 )(Q 2 )(Q 3 ), —B(Q 1 )(Q 2 ),  13  N(Q 1 )(Q 2 ), —P(Q 1 )(Q 2 ), —C(═O)(Q 1 ), —S(═O)(Q 1 ), —S(═O) 2 (Q 1 ), —P(═O)(Q 1 )(Q 2 ), or —P(═S)(Q 1 )(Q 2 ), 
     two or more neighboring groups of R 321  to R 324  are optionally linked to form a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     Q 301  and Q 302  may each independently be: hydrogen; deuterium; —F; —Cl; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 60  alkyl group; a C 2 -C 60  alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; or a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a biphenyl group, or any combination thereof, 
     R 10a  may be: 
     deuterium (-D), —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof; 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, or a C 2 -C 60  heteroaryl alkyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 )(Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ), 
     wherein Q 1  to Q 3 , Q 11  to Q 13 , Q 21  to Q 23 , and Q 31  to Q 33  may each independently be: hydrogen; deuterium; —F; —Cl; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 60  alkyl group; a C 2 -C 60  alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; or a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a is biphenyl group, or any combination thereof. 
     In an embodiment, the hole transport host may be a compound represented by any one of Formulae 3 1 1-1 to 3 1 1-5, and 313, or a combination thereof In an embodiment, the electron transport host may be a compound represented by any one of Formulae 312-1, 313-2, and 313, or a combination thereof In an embodiment, the bipolar host may be a compound represented by any one of Formulae 3 1 1-1 to 3 1 1-5, 312-1, 312-2, and 313, or a combination thereof. 
     In an embodiment, the host may include at least one of Compounds H-01 to H-21 and E-01 to E-18: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In an embodiment, the host may include at least one of Compounds H-01 to H-21 and at least one of Compounds E-01 to E-18. In an embodiment, the dopant may include a phosphorescent dopant and a delayed fluorescent dopant. 
     In an embodiment, the phosphorescent dopant may be a compound represented by Formula 411 or 412, and the delayed fluorescent dopant may be a compound represented by Formula 511 or 512: 
     
       
         
         
             
             
         
       
     
     In Formulae 411, 412, 511, 512, 512A, and 512B, 
     M 41  and M 42  may each independently be platinum (Pt), palladium (Pd), copper(Cu), silver (Ag), gold (Au), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), or thulium (Tm), 
     n41 may be 1, 2, or 3, 
     Ln 42  may be an organic ligand, n42 may be 0, 1, or 2, 
     Y 41  to Y 46  may each independently be N or C, Y 51  and Y 52  may each independently be a single bond, —O—, —S—, —C(R 57 )(R 58 )—,—N(R 57 )—, Si(R 57 )(R 58 )—, —C(═O)—, —S(═O) 2 —, —B(R 57 )—, —P(R 57 )—, or —P(═O)(R 57 )—, 
     Y 53  may be N, B, P, P(═O), or P(═S), 
     L 51  may be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, 
     n51 and n52 may each independently be 0, 1, 2, or 3, and may satisfy n51+n52&gt;1, 
     m51 may be 0, 1, 2, 3, 4, or 5, 
     Ar 51  and Ar 52  may each independently be a group represented by Formula 511A or 511B, 
     k51 and k52 may each independently be 0 or 1, and may satisfy k51+k52&gt;1, 
     X 51  to X 53  may each independently be C or N, 
     A 41  to A 46,  and A 51  to A 55  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, 
     T 41  to T 46  may each independently be a single bond, *—O—*′, or *—S—*′, 
     L 41  to L 45  may each independently be a single bond, *—O—*′, *—S—*′, *—C(R 47 )(R 48 )—*′, *—C(R 47 )═*′, *═C(R 47 )—*′, *—C(R 47 )═C(R 48 )—*═, *—C(═O)—*′, *—C(═S)—*′, *—C≡C—*′, *—B(R 47 )—*′, *—N(R 47 )—*′, *—P(R 47 )—*′, *—Si(R 47 )(R 48 )—*′, *—P(═O)(R 47 )—*′, or *—Ge(R 47 )(R 48 )—*′, 
     m41 to m45 may be 0, 1, 2, or 3, 
     R 41  to R 48 , and R 51  to R 58  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine zo group, a hydrazone group, a substituted or unsubstituted C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkyl group unsubstituted or substituted with at least one R 10a , a C 3 -C 10  cycloalkenyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 10  heterocycloalkenyl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryl group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  aryloxy group unsubstituted or substituted with at least one R 10a , a C 6 -C 60  arylthio group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryl group, unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroaryloxy group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heteroarylthio group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed polycyclic group unsubstituted or substituted with at least one R 10a , a monovalent non-aromatic condensed heteropolycyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 41 )(Q 42 )(Q 43 ), —N(Q 41 )(Q 42 ), —B(Q 41 )(Q 42 ), —C(═O)(Q 41 ), —S(═O) 2 (Q 41 ), or —P(═O)(Q 41 )(Q 42 ), 
     R 47  and R 41 ; R 47  and R 42 ; R 47  and R 43 ; or R 47  and R 44  may optionally be linked to form a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     b41 to b46 and b51 to b55 may each independently be 1, 2, 3, 4, 5, 6, 7, or 8, 
     b56 may be 1, 2, 3, 4, 5, or 6, 
     * and *′ each indicate a binding site to a neighboring atom, 
     R 10a  may be: 
     deuterium (-D), —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof; 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, or a C 2 -C 60  heteroaryl alkyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 (Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ), 
     wherein Q 11  to Q 13 , Q 21  to Q 23 , Q 31  to Q 33 , and Q 41  to Q 43  may each independently is be: hydrogen; deuterium; —F; —Cl; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 60  alkyl group; a C 2 -C 60  alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; or a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a biphenyl group, or any combination thereof. 
     In an embodiment, the phosphorescent dopant may include at least one of Compounds S-1 to S-36 and S-101 to S-184: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In an embodiment, the delayed fluorescence dopant may include at least one of Compounds D-01 to D-26 and DA-01 to DA-30: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In an embodiment, the first electrode of the light-emitting device may be an anode, the second electrode of the light-emitting device may be a cathode, and the interlayer may further include a hole transport region located between the first electrode and the emission area and an electron transport region located between the emission area and the second electrode, the hole transport region includes a hole injection layer, a hole transport layer, an emission auxiliary layer, an electron blocking layer, or any combination thereof, and the electron transport region may include a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, an electron injection layer, or any combination thereof In an embodiment, the spacing layer may not directly contact the electron transport region. In an embodiment, the spacing layer may be closer to the hole transport region than the electron transport region. 
     Another aspect provides an electronic apparatus including the light-emitting device. The electronic apparatus may further include a thin-film transistor. In an embodiment, the electronic apparatus may further include a thin-film transistor including a source electrode and a drain electrode, and the first electrode of the light-emitting device may be electrically connected to the source electrode or the drain electrode. In an embodiment, the electronic apparatus may further include a color filter, a color conversion layer, a touch screen layer, a polarizing layer, or any combination thereof. More details on the electronic apparatus are the same as described herein. 
     Description of FIG.  1   
       FIG. 1  is a schematic cross-sectional view of an embodiment of a light-emitting device constructed according to the principles of the invention. 
     The light-emitting device  10  includes a first electrode  110 , an interlayer  130 , and a second electrode  150 . Hereinafter, the structure of the light-emitting device  10  according to an embodiment and an illustrative method of manufacturing the light-emitting device  10  will be described in connection with  FIG. 1 . 
     First Electrode  110   
     In  FIG. 1 , a substrate may be additionally located under the first electrode  110  or above the second electrode  150 . As the substrate, a glass substrate or a plastic substrate may be used. In an embodiment, the substrate may be a flexible substrate, and may include plastics with excellent heat resistance and durability, such as a polyimide, a polyethylene terephthalate (PET), a polycarbonate, a polyethylene naphthalate, a polyarylate (PAR), a polyetherimide, or any combination thereof. 
     The first electrode  110  may be formed by, for example, depositing or sputtering a material for forming the first electrode  110  on the substrate. When the first electrode  110  is an anode, a material for forming the first electrode  110  may be a high work function material that facilitates injection of holes. 
     The first electrode  110  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. When the first electrode  110  is a transmissive electrode, a material for forming the first electrode  110  may include an indium tin oxide (ITO), an indium zinc oxide (IZO), a tin oxide (SnO 2 ), a zinc oxide (ZnO), or any combinations thereof. In an embodiment, when the first electrode 110 is a semi-transmissive electrode or a reflective electrode, magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), or any combinations thereof may be used as a material for forming a first electrode. The first electrode  110  may have a single layer consisting of a single-layered structure or a multilayer structure including a plurality of layers. For example, the first electrode  110  may have a three-layered structure of an ITO/Ag/ITO. 
     Interlayer  130   
     The interlayer  130  may be located on the first electrode  110 . The interlayer  130  may include an emission layer. The interlayer  130  may further include a hole transport region between the first electrode  110  and the emission layer and an electron transport region between the emission layer and the second electrode  150 . The interlayer  130  may further include metal-containing compounds such as organometallic compounds, inorganic materials such as quantum dots, and the like, in addition to various organic materials. 
     In an embodiment, the interlayer  130  may include, i) two or more emitting units sequentially stacked between the first electrode  110  and the second electrode  150  and ii) a charge generation layer located between the two or more emitting units. When the interlayer  130  includes the emitting unit and the charge generation layer as described above, the light-emitting device  10  may be a tandem light-emitting device. 
     Hole Transport Region in Interlayer  130   
     The hole transport region may have: i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer consisting of a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. The hole transport region may include a hole injection layer, a hole transport layer, an emission auxiliary layer, an electron blocking layer, or any combination thereof. 
     For example, the hole transport region may have a multi-layered structure including a hole injection layer/hole transport layer structure, a hole injection layer/hole transport layer/emission auxiliary layer structure, a hole injection layer/emission auxiliary layer structure, a hole transport layer/emission auxiliary layer structure, or a hole injection layer/hole transport layer/electron blocking layer structure, wherein, in each structure, layers are stacked sequentially is from the first electrode  110 . 
     The hole transport region may include a compound represented by Formula  201 , a compound represented by Formula  202 , or any combination thereof: 
     
       
         
         
             
             
         
       
     
     In Formulae 201 and 202, 
     L 201  to L 204  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     L 205  may be *—O—*′, *—S—*′, *—N(Q 201 )—*′, a C 1 -C 20  alkylene group unsubstituted or substituted with at least one R 10a , a C 2 -C 20  alkenylene group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xa1 to xa4 may each independently be an integer from 0 to 5, 
     xa5 may be an integer from 1 to 10, 
     R 201  to R 204  and Q 201  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     R 201  and R 202  may optionally be linked to each other, via a single bond, a C 1 -C 5  alkylene group unsubstituted or substituted with at least one R 10a , or a C 2 -C 5  alkenylene group unsubstituted or substituted with at least one R 10a , to form a C 8 -C 60  polycyclic group (for example, a carbazole group or the like) unsubstituted or substituted with at least one R 10a  (for example, Compound HT16), 
     R203 and R 204  may optionally be linked to each other, via a single bond, a C 1 -C 5  alkylene group unsubstituted or substituted with at least one R 10a , or a C2-C 5  alkenylene group unsubstituted or substituted with at least one R 10a , to form a C 8 -C 60  polycyclic group unsubstituted or substituted with at least one R 10a , and 
     na1 may be an integer from 1 to 4. 
     In an embodiment, each of Formulae 201 and 202 may include at least one of groups represented by Formulae CY201 to CY217. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     R 10b  and R 10c  in Formulae CY201 to CY217 are the same as described in connection with R 10a , ring CY201 to ring CY204 may each independently be a C 3 -C 20  carbocyclic io group or a C 1 -C 20  heterocyclic group, and at least one hydrogen in Formulae CY201 to CY217 may be unsubstituted or substituted with R 10a . 
     In an embodiment, ring CY 201  to ring CY 204  in Formulae CY201 to CY217 may each independently be a benzene group, a naphthalene group, a phenanthrene group, or an anthracene group. In an embodiment, each of Formulae 201 and 202 may include at least one of is groups represented by Formulae CY201 to CY203. 
     In an embodiment, Formula 201 may include at least one of groups represented by Formulae CY201 to CY203 and at least one of groups represented by Formulae CY204 to CY217. In an embodiment, xa1 in Formula 201 is 1, R201 is a group represented by one of Formulae CY201 to CY203, xa2 may be 0, and Itzoz may be a group represented by one of Formulae CY204 to CY207. 
     In an embodiment, each of Formulae 201 and 202 may not include a group represented by one of Formulae CY201 to CY203. In an embodiment, each of Formulae 201 and 202 may not include a group represented by one of Formulae CY201 to CY203, and may include at least one of groups represented by Formulae CY204 to CY217. In an embodiment, each of Formulae 201 and 202 may not include a group represented by one of Formulae CY201 to CY217. 
     In an embodiment, the hole transport region may include one of Compounds HT1 to HT46, 4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA), 1-N,1-N-bis[4-(diphenylamino)phenyl]-4-N,4-N-diphenylbenzene-1,4-diamine (TDATA), 4,4′,4″-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB or NPD), N4,N4′-di(naphthalen-2-yl)-N4,N4′-diphenyl-[1,1′-biphenyl]-4,4′-diamine (β-NPB), N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), N,N′-bis(3-methylphenyl)-N,N′-diphenyl-9,9-spirobifluorene-2,7-diamine (Spiro-TPD), N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9,9′-spirobi[9H-fluorene]-2,7-diamine (Spiro-NPB), N,N′-di(1-naphthyl)-N,N-diphenyl-2,2′-dimethyl-(1,1′-biphenyl)-4,4′-diamine (methylated NPB), 4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), N,N,N′,N′-tetrakis(3-methylphenyl)-3,3′-dimethylbenzidine (HMTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzenesulfonic acid (PANT/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The thickness of the hole transport region may be in a range of about 50 Å to about 10,000 Å, for example, about 100 Å to about 4,000 Å. When the hole transport region includes the hole injection layer, the hole transport layer, or any combination thereof, the thickness of the hole injection layer may be in a range of about 100 Å to about 9,000 Å, for example, about 100 Å to about 1,000 Å, and 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 these ranges, satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The emission auxiliary layer may increase light-emission efficiency by compensating for an optical resonance distance according to the wavelength of light emitted by an emission layer, and the electron blocking layer may block the leakage of electrons from an emission layer to a hole transport region. Materials that may be included in the hole transport region may be included in the emission auxiliary layer and the electron blocking layer. 
     p-Dopant 
     The hole transport region may further include, in addition to these materials, a charge generation material for the improvement of conductive properties. The charge generation material may be uniformly or non-uniformly dispersed in the hole transport region (for example, in the form of a single layer consisting of a charge generation material). The charge generation material may be, for example, a p-dopant. In an embodiment, the lowest unoccupied molecular orbital (LUMO) energy level of the p-dopant may be about −3.5 eV or less. In an embodiment, the p-dopant may include a quinone derivative, a cyano group-containing compound, a compound containing element EL1 and element EL2, or any combination thereof. 
     Examples of the quinone derivative are tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), etc. Examples of the cyano group-containing compound are 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) and a compound represented by Formula 221 below. 
     
       
         
         
             
             
         
       
     
     In Formula 221, 
     R 221  to R 223  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , and 
     at least one of R 221  to R 223  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each substituted with a cyano group; —F; —Cl; —Br; —I; a C 1 -C 20  alkyl group substituted with a cyano group, —F, —Cl, —Br, —I, or any combination thereof; or any combination thereof. In the compound containing element EL1 and element EL2, element EL1 may be a metal, a metalloid, or a combination thereof, and element EL2 may be a non-metal, a metalloid, or a combination thereof. 
     Examples of the metal are an alkali metal (for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), etc.); an alkaline earth metal (for example, beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), etc.); a transition metal (for example, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), etc.); a post-transition metal (for example, zinc (Zn), indium (In), tin (Sn), etc.); and a lanthanide metal (for example, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.). Examples of the metalloid are silicon (Si), antimony (Sb), and tellurium (Te). Examples of the non-metal are oxygen (O) and a halogen (for example, F, Cl, Br, I, etc.). 
     In an embodiment, examples of the compound containing element EL1 and element EL2 are a metal oxide, a metal halide (for example, a metal fluoride, a metal chloride, a is metal bromide, or a metal iodide), a metalloid halide (for example, a metalloid fluoride, a metalloid chloride, a metalloid bromide, or a metalloid iodide), a metal telluride, or any combination thereof. 
     Examples of the metal oxide are a tungsten oxide (for example, WO, W 2 O 3 , WO 2 , WO 3 , W 2 O 5 , etc.), a vanadium oxide (for example, VO, V 2 O 3 , VO 2 , V 2 O 5 , etc.), a molybdenum oxide (MoO, Mo 2 O 3 , MoO 2 , MoO 3 , Mo 2 O 5 , etc.), and a rhenium oxide (for example, ReO 3 , etc.). 
     Examples of the metal halide are an alkali metal halide, an alkaline earth metal halide, a transition metal halide, a post-transition metal halide, and a lanthanide metal halide. Examples of the alkali metal halide are LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. Examples of the alkaline earth metal halide are BeF 2 , MgF 2 , CaF 2 , SrF 2 , BaF 2 , BeCl 2 , MgCl 2 , CaCl 2 , SrCl 2 , BaCl 2 , BeBr 2 , MgBr 2 , CaBr 2 , SrBr 2 , BaBr 2 , BeI 2 , MgI 2 , CaI 2 , SrI 2 , and BaI 2 . 
     Examples of the transition metal halide are a titanium halide (for example, TiF 4 , TiCl 4 , TiBr 4 , TiI 4 , etc.), a zirconium halide (for example, ZrF 4 , ZrCl 4 , ZrBr 4 , ZrI 4 , etc.), a hafnium halide (for example, HfF 4 , HfCl 4 , HfBr 4 , HfI 4 , etc.), a vanadium halide (for example, VF 3 , VCl 3 , VBr 3 , VI 3 , etc.), a niobium halide (for example, NbF 3 , NbCl 3 , NbBr 3 , NbI 3 , etc.), a tantalum halide (for example, TaF 3 , TaCl 3 , TaBr 3 , TaI 3 , etc.), a chromium halide (for example, CrF 3 , CrCl 3 , CrBr 3 , CrI 3 , etc.), a molybdenum halide (for example, MoF 3 , MoCl 3 , MoBr 3 , MoI 3 , etc.), a tungsten halide (for example, WF 3 , WCl 3 , WBr 3 , WI 3 , etc.), a manganese halide (for example, MnF 2 , MnCl 2 , MnBr 2 , MnI 2 , etc.), a technetium halide (for example, TcF 2 , TcCl 2 , TcBr 2 , TcI 2 , etc.), a rhenium halide (for example, ReF 2 , ReCl 2 , ReBr 2 , ReI 2 , etc.), an iron halide (for example, FeF 2 , FeCl 2 , FeBr 2 , FeI 2 , etc.), a ruthenium halide (for example, RuF 2 , RuCl 2 , RuBr 2 , RuI 2 , etc.), an osmium halide (for example, OsF 2 , OsCl 2 , OsBr 2 , OsI 2 , etc.), a cobalt halide (for example, CoF 2 , CoCl 2 , CoBr 2 , CoI 2 , etc.), a rhodium halide (for example, RhF 2 , RhCl 2 , RhBr 2 , RhI 2 , etc.), an iridium halide (for example, IrF 2 , IrCl 2 , IrBr 2 , IrI 2 , etc.), a nickel halide (for example, NiF 2 , NiCl 2 , NiBr 2 , NiI 2 , etc.), a palladium halide (for example, PdF 2 , PdCl 2 , PdBr 2 , PdI 2 , etc.), a platinum halide (for example, PtF 2 , PtCl 2 , PtBr 2 , PtI 2 , etc.), a copper halide (for example, CuF, CuCl, CuBr, CuI, etc.), a silver halide (for example, AgF, AgCl, AgBr, AgI, etc.), and a gold halide (for example, AuF, AuCl, AuBr, AuI, etc.). 
     Examples of the post-transition metal halide are a zinc halide (for example, ZnF 2 , ZnCl 2 , ZnBr 2 , ZnI 2 , etc.), an indium halide (for example, InI 3 , etc.), and a tin halide (for example, SnI 2 , etc.). Examples of the lanthanide metal halide are YbF, YbF 2 , YbF 3 , SmF 3 , YbCl, YbCl 2 , YbCl 3 , SmCl 3 , YbBr, YbBr 2 , YbBr 3 , SmBr 3 , YbI, YbI 2 , YbI 3 , and SmI 3 . An example of the metalloid halide is an antimony halide (for example, SbCl 5 , etc.). 
     Examples of the metal telluride are an alkali metal telluride (for example, Li 2 Te, Na 2 Te, K 2 Te, Rb 2 Te, Cs 2 Te, etc.), an alkaline earth metal telluride (for example, BeTe, MgTe, CaTe, SrTe, BaTe, etc.), a transition metal telluride (for example, TiTe 2 , ZrTe 2 , Hfre 2 , V 2 Te 3 , Nb 2 Te 3 , Ta 2 Te 3 , Cr 2 Te 3 , Mo 2 Te 3 , W 2 Te 3 , MnTe, TcTe, ReTe, FeTe, RuTe, OsTe, CoTe, RhTe, IrTe, NiTe, PdTe, PtTe, Cu 2 Te, CuTe, Ag 2 Te, AgTe, Au 2 Te, etc.), a post-transition metal telluride (for example, ZnTe, etc.), and a lanthanide metal telluride (for example, LaTe, CeTe, PrTe, NdTe, PmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, etc.). 
     Emission Area in Interlayer  130   
     The light-emitting device according to an embodiment includes an emission area in an interlayer, and the emission area includes an emission layer and a spacing layer. The emission area may be the same as described above and in connection with a light-emitting device to be described later. 
     When the light-emitting device  10  is a full-color light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and/or a blue emission layer, according to a sub-pixel. In an embodiment, the emission layer may have a stacked structure of two or more layers of the red emission layer, the green emission layer, and the blue emission layer, in which the two or more layers contact each other or are separated from each other. In an embodiment, the emission layer may include two or more materials of the red light-emitting material, the green light-emitting material, and the blue light-emitting material, in which the two or more materials are mixed with each other in a single layer to emit white light. 
     The emission layer may include a host and a dopant. The dopant may include a phosphorescent dopant, a fluorescent dopant, or any combination thereof. The amount of the dopant in the emission layer may be from about 0.01 to about 15 parts by weight based on 100 parts by weight of the host. In an embodiment, the emission layer may include a quantum dot. The emission layer may include a delayed fluorescent material. The delayed fluorescent dopant may act as a host or a dopant in the emission layer. 
     The 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 these ranges, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Host 
     In an embodiment, the host may include a compound represented by Formula 301 below: 
       [Ar 301 ] xb11 -[(L 301 ) xb1 -R 301 ] xb21    Formula 301
 
     In Formula 301, 
     Ar 301  and L 301  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xb11 may be 1, 2, or 3, 
     xb1 may be an integer from 0 to 5, 
     R 301  may be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 301 )(Q 302 )(Q 303 ), —N(Q 301 )(Q 302 ), —B(Q 301 )(Q 302 ), —C(═O)(Q 301 ), —S(═O) 2 (Q 301 ), or —P(═O)(Q 301 )(Q 302 ), 
     xb21 may be an integer from 1 to 5, and 
     Q 301  to Q 303  are the same as described in connection with Q 1 . 
     For example, when xb11 in Formula 301 is 2 or more, two or more of Ar 301 (s) may be linked to each other via a single bond. 
     In an embodiment, the host may include a compound represented by Formula 301-1, a compound represented by Formula 301-2, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     In Formulae 301-1 and 301-2, 
     ring A 301  to ring A 304  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     X 301  may be O, S, N-[(L 304 ) xb4 -R 304 ], C(R 304 )(R 305 ), or Si(R 304 )(R 305 ), 
     xb22 and xb23 may each independently be 0, 1, or 2, 
     L 301 , xb1, and R 301  are the same as described herein, 
     L 302  to L 304  may each independently be the same as described in connection with L 301 , 
     xb2 to xb4 may each independently be the same as described in connection with xb1, and 
     R 302  to R 305  and R 311  to R 314  are the same as described in connection with R 301 . 
     In an embodiment, the host may include an alkali earth metal complex, a post-transition metal complex, or a combination thereof. In an embodiment, the host may include a Be complex (for example, Compound H55), an Mg complex, a Zn complex, or a combination thereof. 
     In an embodiment, the host may include one of Compounds H1 to H124, 9,10-di(2-naphthyl)anthracene (ADN), 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN), 9,10-di-(2-naphthyl)-2-t-butyl-anthracene (TBADN), 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), 1,3-di-9-carbazolylbenzene (mCP), 1,3,5-tri(carbazol-9-yl)benzene (TCP), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Phosphorescent Dopant 
     In an embodiment, the phosphorescent dopant may include at least one transition metal as a central metal. The phosphorescent dopant may include a monodentate ligand, a bidentate ligand, a tridentate ligand, a tetradentate ligand, a pentadentate ligand, a hexadentate ligand, or any combination thereof. The phosphorescent dopant may be electrically neutral. For example, the phosphorescent dopant may include an organometallic compound represented by Formula 401: 
     
       
         
         
             
             
         
       
     
     In Formulae 401 and 402, 
     M may be a transition metal (for example, iridium (Ir), platinum (Pt), palladium (Pd), osmium (Os), titanium (Ti), gold (Au), hafnium (Hf), europium (Eu), terbium (Tb), rhodium (Rh), rhenium (Re), or thulium (Tm)), 
     L 401  may be a ligand represented by Formula 402, and xcl may be 1, 2, or 3, wherein when xc1 is two or more, two or more of L 401 (s) may be identical to or different from each other, 
     L 402  may be an organic ligand, and xc2 may be 0, 1, 2, 3, or 4, and when xc2 is 2 or more, two or more of L 402 (s) may be identical to or different from each other, 
     X 401  and X 402  may each independently be nitrogen or carbon, 
     ring A 401  and ring A 402  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, 
     T 401  may be a single bond, *—O—*′, *—S—*′, *—C(═O)—*′, *—N(Q 411 )—*′, *—C(Q 411 )(Q 412 )—*′, *—C(Q 411 )═C(Q 412 )—*′, *—C(Q 411 )═*′, or *═C═*′, 
     X 403  and X 404  may each independently be a chemical bond (for example, a covalent bond or a coordination bond), O, S, N(Q 413 ), B(Q 413 ), P(Q 413 ), C(Q 413 )(Q 414 ), or Si(Q 413 )(Q 414 ), 
     Q 411  to Q 414  are the same as described in connection with Q 1 , 
     R 401  and R 402  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 401 )(Q 402 )(Q 403 ), —N(Q 401 )(Q 402 ), —B(Q 401 )(Q 402 ), —C(═O)(Q 401 ), —S(═O) 2 (Q 401 ), or —P(═O)(Q 401 )(Q 402 ), 
     Q 401  to Q 403  are the same as described in connection with Q 1 , 
     xc11 and xc12 may each independently be an integer from 0 to 10, and 
     * and *′ in Formula 402 each indicates a binding site to M in Formula 401. 
     For example, in Formula 402, i) X 401  is nitrogen, and X 402  is carbon, or ii) each of X 401  and X 402  is nitrogen. 
     In an embodiment, when xcl in Formula 402 is 2 or more, two ring A 401  in two or more of L 401 (s) may be optionally linked to each other via T 402 , which is a linking group, and two ring A 402  may optionally be linked to each other via T 403 , which is a linking group (see Compounds PD1 to PD4 and PD7). T 402  and T 403  are the same as described in connection with T 401  as described herein. 
     The variable L 402  in Formula 401 may be an organic ligand. For example, L 402  may include a halogen group, a diketone group (for example, an acetylacetonate group), a carboxylic acid group (for example, a picolinate group), a —C(═O) group, an isonitrile group, a —CN group, a phosphorus group (for example, a phosphine group, a phosphite group, etc.), or any combination thereof. 
     The phosphorescent dopant may include, for example, one of compounds PD1 to PD25, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Fluorescent Dopant 
     The fluorescent dopant may include an amine group-containing compound, a styryl group-containing compound, or any combination thereof. In an embodiment, the fluorescent dopant may include a compound represented by Formula 501: 
     
       
         
         
             
             
         
       
     
     In Formula 501, 
     Ar 501 , L 501  to L 503 , R 501 , and R 502  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one Rioa or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xd1 to xd3 may each independently be 0, 1, 2, or 3, and 
     xd4 may be 1, 2, 3, 4, 5, or 6. 
     In an embodiment, Ar 501  in Formula 501 may be a condensed cyclic group (for example, an anthracene group, a chrysene group, or a pyrene group) in which three or more monocyclic groups are condensed together. 
     In an embodiment, xd4 in Formula 501 may be 2. 
     In an embodiment, the fluorescent dopant may include: one of Compounds FD1 to FD36; DPVBi; DPAVBi; or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Delayed Fluorescent Dopant 
     The emission layer may include a delayed fluorescent dopant. As described herein, the delayed fluorescent dopant may be selected from compounds capable of emitting delayed fluorescence based on the delayed fluorescence emission mechanism. The delayed fluorescent dopant included in the emission layer may act as a host or a dopant depending on the type of other materials included in the emission layer. 
     In an embodiment, the difference between the triplet energy level (eV) of the delayed fluorescent dopant and the singlet energy level (eV) of the delayed fluorescent dopant may be greater than or equal to about 0 eV and less than or equal to about 0.5 eV. When the difference between the triplet energy level (eV) of the delayed fluorescent dopant and the singlet energy level (eV) of the delayed fluorescent dopant satisfies the above-described range, up-conversion from the triplet state to the singlet state of the delayed fluorescent dopant may effectively occur, and thus, the emission efficiency of the light-emitting device  10  may be improved. 
     In an embodiment, the delayed fluorescent dopant may include i) a material including at least one electron donor (for example, a π electron-rich C 3 -C 60  cyclic group, such as a carbazole group) and at least one electron acceptor (for example, a sulfoxide group, a cyano group, or a π electron-deficient nitrogen-containing C 1 -C 60  cyclic group), and ii) a material including a C 8 -C 60  polycyclic group in which two or more cyclic groups are condensed while sharing boron (B). 
     In an embodiment, the delayed fluorescent material may include at least one of the following Compounds DF1 to DF10: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Quantum Dot 
     The emission layer may include a quantum dot. As described herein, a quantum dot refers to a crystal of a semiconductor compound, and may include any material capable of emitting light of various emission wavelengths according to the size of the crystal. The diameter of the quantum dot may be, for example, in a range of about 1 nm to about 10 nm. The quantum dot may be synthesized by a wet chemical process, a metal organic chemical vapor deposition (MOCVD) process, a molecular beam epitaxy (MBE) process, or any process similar thereto. 
     According to the wet chemical process, a precursor material is mixed with an organic solvent to grow a quantum dot particle crystal. When the crystal grows, the organic solvent naturally acts as a dispersant coordinated on the surface of the quantum dot crystal and controls the growth of the crystal so that the growth of quantum dot particles can be controlled through a process which is more easily performed than vapor deposition methods, such as MOCVD or MBE, and which requires low costs. 
     The quantum dot may include a semiconductor compound of Groups II-VI, a semiconductor compound of Groups III-V, a semiconductor compound of Groups a semiconductor compound of Groups I, III, and VI, a semiconductor compound of Groups IV-VI, an element or a compound of Group IV; or any combination thereof. 
     Examples of the semiconductor compound of Groups II-VI are a binary compound, such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, or MgS; a ternary compound, such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, or MgZnS; a quaternary compound, such as CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, or HgZnSTe; or any combination thereof. 
     Examples of the semiconductor compound of Groups III-V are a binary compound, such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or the like; a ternary compound, such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InAlP, InNAs, InNSb, InPAs, InPSb, or the like; a quaternary compound, such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or the like; or any combination thereof. The semiconductor compound of Groups III-V may further include Group II elements. Examples of the semiconductor compound of Groups III-V further including Group II elements are InZnP, InGaZnP, InAlZnP, etc. 
     Examples of the semiconductor compound of Groups III-VI are a binary compound, such as GaS, GaSe, Ga 2 Se 3 , GaTe, InS, InSe, In 2 S 3 , In 2 Se 3 , or InTe; a ternary compound, such as InGaS 3  or InGaSe 3 ; or any combination thereof. Examples of the semiconductor compound of Groups I, III, and VI are a ternary compound, such as AgInS, AgInS 2 , CuInS, CuInS 2 , CuGaO 2 , AgGaO 2 , or AgAlO 2 ; or any combination thereof. 
     Examples of the semiconductor compound of Groups IV-VI are a binary compound, such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or the like; a ternary compound, such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or the like; a quaternary compound, such as SnPbSSe, SnPbSeTe, SnPbSTe, or the like; or any combination thereof. The Group IV element or compound may include a single element compound, such as Si or Ge; a binary compound, such as SiC or SiGe; or any combination thereof. 
     Each element included in a multi-element compound such as the binary compound, ternary compound and quaternary compound, may exist in a particle with a uniform concentration or non-uniform concentration. The quantum dot may have a single structure or a dual core-shell structure. In the case of the quantum dot having a single structure, the concentration of each element included in the corresponding quantum dot is uniform. In an embodiment, the material contained in the core and the material contained in the shell may be different from each other. 
     The shell of the quantum dot may act as a protective layer to prevent chemical degeneration of the core to maintain semiconductor characteristics and/or as a charging layer to impart electrophoretic characteristics to the quantum dot. The shell may be a single layer or a multi-layer. The interface between the core and the shell may have a concentration gradient that decreases toward the center of the element present in the shell. 
     Examples of the shell of the quantum dot may be an oxide of a metal, a metalloid, or a non-metal, a semiconductor compound, and any combination thereof. Examples of the oxide of a metal, a metalloid, or a non-metal are a binary compound, such as SiO 2 , Al 2 O 3 , TiO 2 , ZnO, MnO, Mn 2 O 3 , Mn 3 O 4 , CuO, FeO, Fe 2 O 3 , Fe 3 O 4 , CoO, CO 3 O 4 , or NiO; a ternary compound, such as MgAl 2 O 4 , CoFe 2 O 4 , NiFe 2 O 4 , or CoMn 2 O 4 ; and any combination thereof. Examples of the semiconductor compound are, as described herein, a semiconductor compound of Groups II-VI; a semiconductor compound of Groups III-V; a semiconductor compound of Groups III-VI; a semiconductor compound of Groups I, III, and VI; a semiconductor compound of Groups IV-VI; and any combination thereof In addition, the semiconductor compound may include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AlAs, AlP, AlSb, or any combination thereof. 
     The full width at half maximum (FWHM) of an emission wavelength spectrum of the quantum dot may be about 45 nm or less, for example, about 40 nm or less, for example, about 30 nm or less, and within these ranges, color purity or color gamut may be increased. In addition, since the light emitted through the quantum dot is emitted in all directions, the wide viewing angle can be improved. 
     In addition, the quantum dot may be a generally spherical particle, a generally pyramidal particle, a generally multi-armed particle, a generally cubic nanoparticle, a generally nanotube-shaped particle, a generally nanowire-shaped particle, a generally nanofiber-shaped particle, or a generally nanoplate-shaped particle. 
     Because the energy band gap can be adjusted by controlling the size of the quantum dot, light having various wavelength bands can be obtained from the quantum dot emission layer. Therefore, by using quantum dots of different sizes, a light-emitting device that emits light of various wavelengths may be implemented. In an embodiment, the size of the quantum dot may be selected to emit red, green and/or blue light. In addition, the size of the quantum dot may be configured to emit white light by combining light of various colors. 
     Electron Transport Region in Interlayer  130   
     The electron transport region may have: i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer consisting of a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. 
     The electron transport region may include a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     In an embodiment, the electron transport region may have an electron transport layer/electron injection layer structure, a hole blocking layer/electron transport layer/electron injection layer structure, an electron control layer/electron transport layer/electron injection layer structure, or a buffer layer/electron transport layer/electron injection layer structure, wherein, for each structure, constituting layers are sequentially stacked from an emission layer. 
     In an embodiment, the electron transport region (for example, the buffer layer, the hole blocking layer, the electron control layer, or the electron transport layer in the electron transport region) may include a metal-free compound including at least one π electron-deficient nitrogen-containing C 1 -C 60  cyclic group. 
     In an embodiment, the electron transport region may include a compound represented by Formula 601 below: 
       [Ar 601 ] xe11 -[(L 601 ) xe1 -R 601 ] xe21    Formula 601
 
     wherein, in Formula 601, 
     Ar 601  and L601 may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xe11 may be 1, 2, or 3, 
     xe1 may be 0, 1, 2, 3, 4, or 5, 
     R 601  may be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 601 )(Q 602 )(Q 603 ), —C(═O)(Q 601 ), —S(═O) 2 (Q 601 ), or —P(═O)(Q 601 )(Q 602 ), 
     Q 601  to Q 603  are the same as described in connection with Q 1 , 
     xe21 may be 1, 2, 3, 4, or 5, 
     at least one of Ar 601 , L 601 , and R 601  may each independently be a π electron-deficient nitrogen-containing C 1 -C 60  cyclic group unsubstituted or substituted with at least one R 10a . 
     For example, when xe11 in Formula 601 is 2 or more, two or more of Ar 601 (s) may be linked via a single bond. 
     In an embodiment, Ar 601  in Formula 601 may be a substituted or unsubstituted anthracene group. 
     In an embodiment, the electron transport region may include a compound represented by Formula 601-1: 
     
       
         
         
             
             
         
       
     
     In Formula 601-1, 
     X 614  may be N or C(R 614 ), X 615  may be N or C(R 615 ), X 616  may be N or C(R 616 ), at least one of X 614  to X 616  may be N, 
     L 611  to L 613  are the same as described in connection with L 601 , 
     xe611 to xe613 are the same as described in connection with xe1, 
     R 611  to R 613  are the same as described in connection with R 601 , 
     R 614  to R 616  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a . 
     For example, xe1 and xe611 to xe613 in Formulae 601 and 601-1 may each independently be 0, 1, or 2. 
     The electron transport region may include one of Compounds ET1 to ET45, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), tris-(8-hydroxyquinoline)aluminum (AlQ 3 ), bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)aluminum (BAlq), 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), 4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The thickness of the electron transport region may be from about 160 Å to about 5,000 Å, for example, from about 100 Å to about 4,000 Å. When the electron transport region includes a buffer layer, a hole blocking layer, an electron control layer, an electron transport layer, or any combination thereof, the thickness of the buffer layer, the hole blocking layer, or the electron control layer may each independently be from about 20 Å to about 1000 Å, for example, about 30 Å to about 300 Å, and the thickness of the electron transport layer may be from about 100 Å to about 1000 Å, for example, about 150 Å to about 500 Å. When the thicknesses of the buffer layer, hole blocking layer, electron control layer, electron transport layer and/or electron transport layer are within these ranges, satisfactory electron transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport region (for example, the electron transport layer in the electron transport region) may further include, in addition to the materials described above, a metal-containing material. 
     The metal-containing material may include an alkali metal complex, alkaline io earth metal complex, or any combination thereof. The metal ion of an alkali metal complex may be a Li ion, a Na ion, a K ion, a Rb ion, or a Cs ion, and the metal ion of alkaline earth metal complex may be a Be ion, a Mg ion, a Ca ion, a Sr ion, or a Ba ion. A ligand coordinated with the metal ion of the alkali metal complex or the alkaline earth-metal complex may include a hydroxyquinoline, a hydroxyisoquinoline, a hydroxybenzoquinoline, a hydroxyacridine, a hydroxyphenanthridine, a hydroxyphenyloxazole, a hydroxyphenylthiazole, a hydroxyphenyloxadiazole, a hydroxyphenylthiadiazole, a hydroxyphenylpyridine, a hydroxyphenylbenzimidazole, a hydroxyphenylbenzothiazole, a bipyridine, a phenanthroline, a cyclopentadiene, or any combination thereof. 
     For example, the metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (lithium quinolate, LiQ) or ET-D2: 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer that facilitates the injection of electrons from the second electrode  150 . The electron injection layer may directly contact the second electrode  150 . 
     The electron injection layer may have: i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer consisting of a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. 
     The electron injection layer may include an alkali metal, alkaline earth metal, a rare earth metal, an alkali metal-containing compound, alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof. 
     The alkali metal may include Li, Na, K, Rb, Cs, or any combination thereof. The alkaline earth metal may include Mg, Ca, Sr, Ba, or any combination thereof. The rare earth metal may include Sc, Y, Ce, Tb, Yb, Gd, or any combination thereof. 
     The alkali metal-containing compound, the alkaline earth metal-containing compound, and the rare earth metal-containing compound may be oxides, halides (for example, fluorides, chlorides, bromides, or iodides), or tellurides of the alkali metal, the alkaline earth metal, and the rare earth metal, or any combination thereof. 
     The alkali metal-containing compound may include alkali metal oxides, such as Li 2 O, Cs 2 O, or K 2 O, alkali metal halides, such as LiF, NaF, CsF, KF, LiI, NaI, CsI, or KI, or any combination thereof. The alkaline earth metal-containing compound may include an alkaline earth metal compound, such as BaO, SrO, CaO, Ba x Sr 1−x O (x is a real number satisfying the condition of 0&lt;x&lt;1), Ba x Ca 1-x O (x is a real number satisfying the condition of 0&lt;x&lt;1), or the like. The rare earth metal-containing compound may include YbF 3 , ScF 3 , Sc 2 O 3 , Y 2 O 3 , Ce 2 O 3 , GdF 3 , TbF 3 , YbI 3 , ScI 3 , TbI 3 , or any combination thereof. In an embodiment, the rare earth metal-containing compound may include a lanthanide metal telluride. Examples of the lanthanide metal telluride are LaTe, CeTe, PrTe, NdTe, PmTe, SmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, La 2 Te 3 , Ce 2 Te 3 , Pr 2 Te 3 , Nd 2 Te 3 , Pm 2 Te 3 , Sm 2 Te 3 , Eu 2 Te 3 , Gd 2 Te 3 , Tb 2 Te 3 , Dy 2 Te 3 , Ho 2 Te 3 , Er 2 Te 3 , Tm 2 Te 3 , Yb 2 Te 3 , and Lu 2 Te 3 . 
     The alkali metal complex, the alkaline earth-metal complex, and the rare earth metal complex may include i) one of ions of the alkali metal, the alkaline earth metal, and the rare earth metal and ii), as a ligand bonded to the metal ion, for example, a hydroxyquinoline, a hydroxyisoquinoline, a hydroxybenzoquinoline, a hydroxyacridine, a hydroxyphenanthridine, a hydroxyphenyloxazole, a hydroxyphenylthiazole, a hydroxyphenyloxadiazole, a hydroxyphenylthiadiazole, a hydroxyphenylpyridine, a hydroxyphenyl benzimidazole, a hydroxyphenylbenzothiazole, a bipyridine, a phenanthroline, a cyclopentadiene, or any combination thereof. 
     The electron injection layer may consist of an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof, as described above. In an embodiment, the electron injection layer may further include an organic material (for example, a compound represented by Formula 601). 
     In an embodiment, the electron injection layer may consist of i) an alkali metal-containing compound (for example, an alkali metal halide), ii) a) an alkali metal-containing compound (for example, an alkali metal halide); and b) an alkali metal, an alkaline earth metal, a rare earth metal, or any combination thereof. In an embodiment, the electron injection layer may be a KI:Yb co-deposited layer, an RbI:Yb co-deposited layer, or the like. 
     When the electron injection layer further includes an organic material, an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth-metal complex, a rare earth metal complex, or any combination thereof may be homogeneously or non-homogeneously dispersed in a matrix including the organic material. 
     The thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, and, for example, about 3 Å to about 90 Å. When the thickness of the electron injection layer is within the range described above, the electron injection layer may have satisfactory electron injection characteristics without a substantial increase in driving voltage. 
     Second Electrode  150   
     The second electrode  150  may be located on the interlayer  130  having such a structure. The second electrode  150  may be a cathode, which is an electron injection electrode, and as the material for the second electrode  150 , a metal, an alloy, an electrically conductive compound, or any combination thereof, each having a low work function, may be used. 
     In an embodiment, the second electrode  150  may include lithium (Li), silver (Ag), magnesium (Mg), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), ytterbium (Yb), silver-ytterbium (Ag—Yb), an ITO, an IZO, or a combination thereof. The second electrode  150  may be a transmissive electrode, a semi-transmissive electrode, or a reflective electrode. The second electrode  150  may have a single-layered structure or a multi-layered structure including two or more layers. 
     Capping Layer 
     A first capping layer may be located outside the first electrode  110 , and/or a second capping layer may be located outside the second electrode  150 . In detail, the light-emitting device  10  may have a structure in which the first capping layer, the first electrode  110 , the interlayer  130 , and the second electrode  150  are sequentially stacked in this stated order, a structure in which the first electrode  110 , the interlayer  130 , the second electrode  150 , and the second capping layer are sequentially stacked in this stated order, or a structure in which the first capping layer, the first electrode  110 , the interlayer  130 , the second electrode  150 , and the second capping layer are sequentially stacked in this stated order. 
     Light generated in an emission layer of the interlayer  130  of the light-emitting device  10  may be extracted toward the outside through the first electrode  110 , which is a semi-transmissive electrode or a transmissive electrode, and the first capping layer or light generated in an emission layer of the interlayer  130  of the light-emitting device  10  may be extracted toward the outside through the second electrode  150 , which is a semi-transmissive electrode or a transmissive electrode, and the second capping layer. 
     The first capping layer and the second capping layer may increase external emission efficiency according to the principle of constructive interference. Accordingly, the light extraction efficiency of the light-emitting device  10  is increased, so that the emission efficiency of the light-emitting device  10  may be improved. Each of the first capping layer and second capping layer may include a material having a refractive index (at 589 nm) of about 1.6 or more. 
     The first capping layer and the second capping layer may each independently be an organic capping layer including an organic material, an inorganic capping layer including an inorganic material, or an organic-inorganic composite capping layer including an organic material and an inorganic material. 
     At least one selected from the first capping layer and the second capping layer may each independently include carbocyclic compounds, heterocyclic compounds, amine group-containing compounds, porphyrin derivatives, phthalocyanine derivatives, naphthalocyanine derivatives, alkali metal complexes, alkaline earth metal complexes, or any combination thereof. The carbocyclic compound, the heterocyclic compound, and the amine group-containing compound may be optionally substituted with a substituent containing O, N, S, Se, Si, F, Cl, Br, I, or any combination thereof. 
     In an embodiment, at least one of the first capping layer and the second capping layer may each independently include an amine group-containing compound. In an embodiment, at least one of the first capping layer and the second capping layer may each independently include a compound represented by Formula 201, a compound represented by Formula 202, or any combination thereof. 
     In an embodiment, at least one of the first capping layer and the second capping layer may each independently include one of Compounds HT28 to HT33, one of Compounds CP1 to CP6, N4,N4′-di(naphthalen-2-yl)-N4,N4′-diphenyl-[1,1′-biphenyl]-4,4′-diamine (β-NPB), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Film 
     A condensed cyclic compound represented by Formula 1 may be included in various films. Accordingly, in an embodiment, a film including the condensed cyclic compound represented by Formula 1 may be provided. The film may be, for example, an optical member or light control means, e.g., a color filter, a color conversion member, a capping layer, a light extraction efficiency enhancement layer, a selective light absorption layer, a polarizing layer, a quantum dot-containing layer, etc., a light blocking member, e.g., a light reflecting layer, a light absorbing layer, etc., a protective member, e.g., an insulating layer, a dielectric layer, etc., and the like. 
     Electronic Apparatus 
     The light-emitting device may be included in various electronic apparatuses. In an embodiment, the electronic apparatus including the light-emitting device may be a light-emitting apparatus, an authentication apparatus, or the like. 
     The electronic apparatus (for example, light-emitting apparatus) may further include, in addition to the light-emitting device, i) a color filter, ii) a color conversion layer, or iii) a color filter and a color conversion layer. The color filter and/or the color conversion layer may be located in at least one traveling direction of light emitted from the light-emitting device. In an embodiment, the light emitted from the light-emitting device may be blue light or white light. The light-emitting device may be the same as described above. In an embodiment, the color conversion layer may include quantum dots. The quantum dot may be, for example, a quantum dot as described herein. 
     The electronic apparatus may include a first substrate. The first substrate may include a plurality of subpixel areas, the color filter may include a plurality of color filter areas respectively corresponding to the subpixel areas, and the color conversion layer may include a plurality of color conversion areas respectively corresponding to the subpixel areas. 
     A pixel-defining film may be located among the subpixel areas to define each of the subpixel areas. The color filter may further include a plurality of color filter areas and light-shielding patterns located among the color filter areas, and the color conversion layer may include a plurality of color conversion areas and light-shielding patterns located among the color conversion areas. 
     The color filter areas (or the color conversion areas) may include a first area emitting first color light, a second area emitting second color light, and/or a third area emitting third color light, and the first color light, the second color light, and/or the third color light may have different maximum emission wavelengths from one another. In an embodiment, the first color light may be red light, the second color light may be green light, and the third color light may be blue light. In an embodiment, the color filter areas (or the color conversion areas) may include quantum dots. In detail, the first area may include a red quantum dot, the second area may include a green quantum dot, and the third area may not include a quantum dot. The quantum dot is the same as described herein. The first area, the second area, and/or the third area may each include a scatter. 
     In an embodiment, the light-emitting device may emit first light, the first area may absorb the first light to emit first first-color light, the second area may absorb the first light to emit second first-color light, and the third area may absorb the first light to emit third first-color light. In this regard, the first first-color light, the second first-color light, and the third first-color light may have different maximum emission wavelengths. In detail, the first light may be blue light, the first first-color light may be red light, the second first-color light may be green light, and the third first-color light may be blue light. 
     The electronic apparatus may further include a thin-film transistor in addition to the light-emitting device 10 as described above. The thin-film transistor may include a source electrode, a drain electrode, and an activation layer, wherein any one of the source electrode and the drain electrode may be electrically connected to any one of the first electrode and the second electrode of the light-emitting device. The thin-film transistor may further include a gate electrode, a gate insulating film, etc. The activation layer may include a crystalline silicon, an amorphous silicon, an organic semiconductor, an oxide semiconductor, or the like. 
     The electronic apparatus may further include a sealing portion for sealing the light-emitting device. The sealing portion and/or the color conversion layer may be placed between the color filter and the light-emitting device. The sealing portion allows light from the light-emitting device to be extracted to the outside, while simultaneously preventing ambient air and moisture from penetrating into the light-emitting device. The sealing portion may be a sealing substrate including a transparent glass substrate or a plastic substrate. The sealing portion may be a thin-film encapsulation layer including at least one layer of an organic layer and/or an inorganic layer. When the sealing portion is a thin film encapsulation layer, the electronic apparatus may be flexible. 
     Various functional layers may be additionally located on the sealing portion, in addition to the color filter and/or the color conversion layer, according to the use of the electronic apparatus. The functional layers may include a touch screen layer, a polarizing layer, and the like. The touch screen layer may be a pressure-sensitive touch screen layer, a capacitive touch screen layer, or an infrared touch screen layer. The authentication apparatus may be, for example, a biometric authentication apparatus that authenticates an individual by using biometric information of a living body (for example, fingertips, pupils, etc.). 
     The authentication apparatus may further include, in addition to the light-emitting device, a biometric information collector. The electronic apparatus may take the form of or be applied to various displays, light sources, lighting, personal computers (for example, a mobile personal computer), mobile phones, digital cameras, electronic organizers, electronic dictionaries, electronic game machines, medical instruments (for example, electronic thermometers, sphygmomanometers, blood glucose meters, pulse measurement devices, pulse wave measurement devices, electrocardiogram displays, ultrasonic diagnostic devices, or endoscope displays), fish finders, various measuring instruments, meters (for example, meters for a vehicle, an aircraft, and a vessel), projectors, and the like. 
     Description of FIGS.  2  and  3   
       FIG. 2  is a cross-sectional view of an embodiment of a light-emitting apparatus including a light-emitting device constructed according to the principles of the invention. 
     The light-emitting apparatus  180  of  FIG. 2  includes a substrate  100 , a thin-film transistor (TFT)  200 , a light-emitting device  10 , and an encapsulation portion  300  that seals the light-emitting device  10 . 
     The substrate  100  may be a flexible substrate, a glass substrate, or a metal substrate. A buffer layer  210  may be formed on the substrate  100 . The buffer layer  210  may prevent penetration of impurities through the substrate  100  and may provide a substantially flat surface on the substrate  100 . 
     The TFT  200  may be located on the buffer layer  210 . The TFT  200  may include an activation layer  220 , a gate electrode  240 , a source electrode  260 , and a drain electrode  270 . The activation layer  220  may include an inorganic semiconductor such as a silicon or a polysilicon, an organic semiconductor, or an oxide semiconductor, and may include a source region, a drain region and a channel region. A gate insulating film  230  for insulating the activation layer  220  from the gate electrode  240  may be located on the activation layer  220 , and the gate electrode  240  may be located on the gate insulating film  230 . 
     An interlayer insulating film  250  is located on the gate electrode  240 . The interlayer insulating film  250  may be placed between the gate electrode  240  and the source electrode  260  to insulate the gate electrode  240  from the source electrode  260  and between the gate electrode  240  and the drain electrode  270  to insulate the gate electrode  240  from the drain electrode  270 . 
     The source electrode  260  and the drain electrode  270  may be located on the interlayer insulating film  250 . The interlayer insulating film  250  and the gate insulating film  230  may be formed to expose the source region and the drain region of the activation layer  220 , and the source electrode  260  and the drain electrode  270  may be in contact with the exposed portions of the source region and the drain region of the activation layer  220 . 
     The TFT  200  is electrically connected to a light-emitting device to drive the light-emitting device  10 , and is covered by a passivation layer  280 . The passivation layer  280  may include an inorganic insulating film, an organic insulating film, or a combination thereof. The light-emitting device  10  is provided on the passivation layer  280 . The light-emitting device  10  may include a first electrode  110 , an interlayer  130 , and a second electrode  150 . 
     The first electrode  110  may be formed on the passivation layer  280 . The passivation layer  280  does not completely cover the drain electrode  270  and exposes a portion of the drain electrode  270 , and the first electrode  110  is connected to the exposed portion of the drain electrode  270 . 
     A pixel defining layer  290  containing an insulating material may be located on the first electrode  110 . The pixel defining layer  290  exposes a region of the first electrode  110 , and an interlayer  130  may be formed in the exposed region of the first electrode  110 . The pixel defining layer  290  may be a polyimide or a polyacrylic organic film. At least some layers of the interlayer  130  may extend beyond the upper portion of the pixel defining layer  290  to be located in the form of a common layer. The second electrode  150  may be located on the interlayer  130 , and a capping layer  170  may be additionally formed on the second electrode  150 . The capping layer  170  may be formed to cover the second electrode  150 . 
     The encapsulation portion  300  may be located on the capping layer  170 . The encapsulation portion  300  may be located on a light-emitting device to protect the light-emitting device from moisture or oxygen. The encapsulation portion  300  may include: an inorganic film including a silicon nitride (SiN x ), a silicon oxide (SiO x ), an indium tin oxide, an indium zinc oxide, or any combination thereof; an organic film including a polyethylene terephthalate, a polyethylene naphthalate, a polycarbonate, a polyimide, a polyethylene sulfonate, a polyoxymethylene, a polyarylate, a hexamethyldisiloxane, an acrylic resin (for example, a polymethyl methacrylate, a polyacrylic acid, or the like), an epoxy-based resin (for example, an aliphatic glycidyl ether (AGE), or the like), or a combination thereof; or a combination of the inorganic film and the organic film. 
       FIG. 3  is a cross-sectional view of another embodiment of a light-emitting apparatus including a light-emitting device constructed according to the principles of the invention. 
     The light-emitting apparatus  190  of  FIG. 3  is substantially the same as the light-emitting apparatus  180  of  FIG. 2 , except that a light-shielding pattern  500  and a functional region  400  are additionally located on the encapsulation portion  300 . The functional region  400  may be a combination of i) a color filter area, ii) a color conversion area, or iii) a combination of the color filter area and the color conversion area. In an embodiment, the light-emitting device  10  included in the light-emitting apparatus  190  of  FIG. 3  may be a tandem light-emitting device. 
     Manufacture Method 
     Respective layers included in the hole transport region, the emission layer, and respective layers included in the electron transport region may be formed in a certain region by using one or more suitable methods selected from vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) deposition, ink-jet printing, laser-printing, and laser-induced thermal imaging. 
     When layers constituting the hole transport region, an emission layer, and layers constituting the electron transport region are formed by vacuum deposition, the deposition may be performed at a deposition temperature of about 100° C. to about 500° C., a vacuum degree of about 10 −8  torr to about 10 −3  torr, and a deposition speed of about 0.01 Å/sec to about 100 Å/sec, depending on a material to be included in a layer to be formed and the structure of a layer to be formed. 
     Definition of Terms 
     As used herein, the term “interlayer” refers to a single layer and/or all layers between a first electrode and a second electrode of a light-emitting device. 
     As used herein, the term “band gap” of a compound refers to the gap between the highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level. 
     As used herein, the terms “HOMO energy level” and “LUMO energy level” may be measured by, for example, a differential pulse voltammetry using ferrocene as a reference material, or a cyclic voltammetry and an optical band gap. 
     As used herein, the term “atom” may mean an element or its corresponding radical bonded to one or more other atoms. 
     The terms “hydrogen” and “deuterium” refer to their respective atoms and corresponding radicals with the deuterium radical abbreviated “-D”, and the terms “—F, —Cl, —Br, and —I” are radicals of, respectively, fluorine, chlorine, bromine, and iodine. 
     As used herein, a substituent for a monovalent group, e.g., alkyl, may also be, independently, a substituent for a corresponding divalent group, e.g., alkylene. 
     As used herein, the term “C 3 -C 60  carbocyclic group” refers to a cyclic group consisting of carbon only as a ring-forming atom and having three to sixty carbon atoms, and the term “C 1 -C 60  heterocyclic group” as used herein refers to a cyclic group that has one to sixty carbon atoms and further has, in addition to carbon, a heteroatom as a ring-forming atom. The C 3 -C 60  carbocyclic group and the C 1 -C 60  heterocyclic group may each be a monocyclic group consisting of one ring or a polycyclic group in which two or more rings are fused with each other. For example, the C 1 -C 60  heterocyclic group has 3 to 61 ring-forming atoms. 
     As used herein, the “cyclic group” may include the C 3 -C 60  carbocyclic group, and the C 1 -C 60  heterocyclic group. 
     As used herein, the term “π electron-rich C 3 -C 60  cyclic group” refers to a cyclic group that has three to sixty carbon atoms and does not include *—N═*′ as a ring-forming moiety, and the term “π electron-deficient nitrogen-containing C 1 -C 60  cyclic group” as used herein refers to a heterocyclic group that has one to sixty carbon atoms and includes *—N═*′ as a ring-forming moiety. 
     For example, the C 3 -C 60  carbocyclic group may be i) a group TG1 or ii) a fused cyclic group in which two or more groups TG1 are fused with each other, for example, a cyclopentadiene group, an adamantane group, a norbornane group, a benzene group, a pentalene group, a naphthalene group, an azulene group, an indacene group, an acenaphthylene group, a phenalene group, a phenanthrene group, an anthracene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a perylene group, a pentaphene group, a heptalene group, a naphthacene group, a picene group, a hexacene group, a pentacene group, a rubicene group, a coronene group, an ovalene group, an indene group, a fluorene group, a spiro-bifluorene group, a benzofluorene group, an indenophenanthrene group, or an indenoanthracene group. 
     The C 1 -C 60  heterocyclic group may be i) a group TG2, ii) a fused cyclic group in which two or more groups TG2 are fused with each other, or iii) a fused cyclic group in which at least one group TG2 and at least one group TG1 are fused with each other, for example, a pyrrole group, a thiophene group, a furan group, an indole group, a benzoindole group, a naphthoindole group, an isoindole group, a benzoisoindole group, a naphthoisoindole group, a benzosilole group, a benzothiophene group, a benzofuran group, a carbazole group, a dibenzosilole group, a dibenzothiophene group, a dibenzofuran group, an indenocarbazole group, an indolocarbazole group, a benzofurocarbazole group, a benzothienocarbazole group, a benzosilolocarbazole group, a benzoindolocarbazole group, a benzocarbazole group, a benzonaphthofuran group, a benzonaphthothiophene group, a benzonaphthosilole group, a benzofurodibenzofuran group, a benzofurodibenzothiophene group, a benzothienodibenzothiophene group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzoisoxazole group, a benzothiazole group, a benzoisothiazole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a benzoquinoline group, a benzoisoquinoline group, a quinoxaline group, a benzoquinoxaline group, a quinazoline group, a benzoquinazoline group, a phenanthroline group, a cinnoline group, a phthalazine group, a naphthyridine group, an imidazopyridine group, an imidazopyrimidine group, an imidazotriazine group, an imidazopyrazine group, an imidazopyridazine group, an azacarbazole group, an azafluorene group, an azadibenzosilole group, an azadibenzothiophene group, an azadibenzofuran group, etc. 
     The π electron-rich C 3 -C 60  cyclic group may be i) a group TG1, ii) a fused cyclic group in which two or more groups TG1 are fused with each other, iii) a group TG3, iv) a fused cyclic group in which two or more groups TG3 are fused with each other, or v) a fused cyclic group in which at least one group TG3 and at least one group TG1 are fused with each other, for example, the C 3 -C 60  carbocyclic group, a 1H-pyrrole group, a silole group, a borole group, a 2H-pyrrole group, a 3H-pyrrole group, a thiophene group, a furan group, an indole group, a benzoindole group, a naphthoindole group, an isoindole group, a benzoisoindole group, a naphthoisoindole group, a benzosilole group, a benzothiophene group, a benzofuran group, a carbazole group, a dibenzosilole group, a dibenzothiophene group, a dibenzofuran group, an indenocarbazole group, an indolocarbazole group, a benzofurocarbazole group, a benzothienocarbazole group, a benzosilolocarbazole group, a benzoindolocarbazole group, a benzocarbazole group, a benzonaphthofuran group, a benzonaphthothiophene group, a benzonaphthosilole group, a benzofurodibenzofuran group, a benzofurodibenzothiophene group, a benzothienodibenzothiophene group, etc. 
     The π electron-deficient nitrogen-containing C 1 -C 60  cyclic group may be i) a group TG4, ii) a fused cyclic group in which two or more group TG4 are fused with each other, iii) a fused cyclic group in which at least one group TG4 and at least one group TG1 are fused with each other, iv) a fused cyclic group in which at least one group TG4 and at least one group TG3 are fused with each other, or v) a fused cyclic group in which at least one group TG4, at least one group TG1, and at least one group TG3 are fused with one another, for example, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzoisoxazole group, a benzothiazole group, a benzoisothiazole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a benzoquinoline group, a benzoisoquinoline group, a quinoxaline group, a benzoquinoxaline group, a quinazoline group, a benzoquinazoline group, a phenanthroline group, a cinnoline group, a phthalazine group, a naphthyridine group, an imidazopyridine group, an imidazopyrimidine group, an imidazotriazine group, an imidazopyrazine group, an imidazopyridazine group, an azacarbazole group, an azafluorene group, an azadibenzosilole group, an azadibenzothiophene group, an azadibenzofuran group, etc. 
     The group TG1 may be a cyclopropane group, a cyclobutane group, a cyclopentane group, a cyclohexane group, a cycloheptane group, a cyclooctane group, a cyclobutene group, a cyclopentene group, a cyclopentadiene group, a cyclohexene group, a cyclohexadiene group, a cycloheptene group, an adamantane group, a norbornane (or a bicyclo[2.2.1]heptane) group, a norbornene group, a bicyclo[1.1.1]pentane group, a bicyclo[2.1.1]hexane group, a bicyclo[2.2.2]octane group, or a benzene group, 
     the group TG2 may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, a borole group, a 2H-pyrrole group, a 3H-pyrrole group, an imidazole group, a pyrazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, an azasilole group, an azaborole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a tetrazine group, a pyrrolidine group, an imidazolidine group, a dihydropyrrole group, a piperidine group, a tetrahydropyridine group, a dihydropyridine group, a hexahydropyrimidine group, a tetrahydropyrimidine group, a dihydropyrimidine group, a piperazine group, a tetrahydropyrazine group, a dihydropyrazine group, a tetrahydropyridazine group, or a dihydropyridazine group, 
     the group TG3 may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, or a borole group, and 
     the group TG4 may be a 2H-pyrrole group, a 3H-pyrrole group, an imidazole group, a pyrazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, an azasilole group, an azaborole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, or a tetrazine group. 
     The term “the cyclic group, the C 3 -C 60  carbocyclic group, the C 1 -C 60  heterocyclic group, the π electron-rich C 3 -C 60  cyclic group, or the π electron-deficient nitrogen-containing C 1 -C 60  cyclic group” as used herein refer to a group fused to any cyclic group or a polyvalent group (for example, a divalent group, a trivalent group, a tetravalent group, etc.), depending on the structure of a formula in connection with which the terms are used. In an embodiment, “a benzene group” may be a benzo group, a phenyl group, a phenylene group, or the like, which may be easily understand by one of ordinary skill in the art according to the structure of a formula including the “benzene group.” 
     Examples of the monovalent C 3 -C 60  carbocyclic group and the monovalent C 1 -C 60  heterocyclic group are a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic fused polycyclic group, and a monovalent non-aromatic fused heteropolycyclic group, and examples of the divalent C 3 -C 60  carbocyclic group and the monovalent C 1 -C 60  heterocyclic group are a C 3 -C 10  cycloalkylene group, a C 1 -C 10  heterocycloalkylene group, a C 3 -C 10  cycloalkenylene group, a C 1 -C 10  heterocycloalkenylene group, a C 6 -C 60  arylene group, a C 1 -C 60  heteroarylene group, a divalent non-aromatic fused polycyclic group, and a substituted or unsubstituted divalent non-aromatic fused heteropolycyclic group. 
     The term “C 1 -C 60  alkyl group” as used herein refers to a linear or branched aliphatic hydrocarbon monovalent group that has one to sixty carbon atoms, and examples thereof are a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. The term “C 1 -C 60  alkylene group” as used herein refers to a divalent group having a structure corresponding to the C 1 -C 60  alkyl group. 
     The term “C 2 -C 60  alkenyl group” as used herein refers to a monovalent hydrocarbon group having at least one carbon-carbon double bond in the middle or at the terminus of the C 2 -C 60  alkyl group, and examples thereof are an ethenyl group, a propenyl group, and a butenyl group. The term “C 2 -C 60  alkenylene group” as used herein refers to a divalent group having a structure corresponding to the C 2 -C 60  alkenyl group. 
     The term “C 2 -C 60  alkynyl group” as used herein refers to a monovalent hydrocarbon group having at least one carbon-carbon triple bond in the middle or at the terminus of the C 2 -C 60  alkyl group, and examples thereof include an ethynyl group and a propynyl group. The term “C 2 -C 60  alkynylene group” as used herein refers to a divalent group having a structure corresponding to the C 2 -C 60  alkynyl group. 
     The term “C 1 -C 60  alkoxy group” as used herein refers to a monovalent group represented by —OA101 (wherein A 101  is the C 1 -C 60  alkyl group), and examples thereof include a methoxy group, an ethoxy group, and an isopropyloxy group. 
     The term “C 3 -C 10  cycloalkyl group” as used herein refers to a monovalent saturated hydrocarbon cyclic group having 3 to 10 carbon atoms, and examples thereof are a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group (or bicyclo[2.2.1]heptyl group), a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, and a bicyclo[2.2.2]octyl group. The term “C 3 -C 10  cycloalkylene group” as used herein refers to a divalent group having a structure corresponding to the C 3 -C 10  cycloalkyl group. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent cyclic group that further includes, in addition to a carbon atom, at least one heteroatom as a ring-forming atom and has 1 to 10 carbon atoms, and examples thereof are a 1,2,3,4-oxatriazolidinyl group, a tetrahydrofuranyl group, and a tetrahydrothiophenyl group. The term “C 1 -C 10  heterocycloalkylene group” as used herein refers to a divalent group having a structure corresponding to the C 1 -C 10  heterocycloalkyl group. 
     The term C 3 -C 10  cycloalkenyl group used herein refers to a monovalent cyclic group that has three to ten carbon atoms and at least one carbon-carbon double bond in the ring thereof and no aromaticity, and examples thereof are a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. The term “C 3 -C 10  cycloalkenylene group” as used herein refers to a divalent group having a structure corresponding to the C 3 -C 10  cycloalkenyl group. 
     The term “C 1 -C 10  heterocycloalkenyl group” as used herein refers to a monovalent cyclic group that has, in addition to a carbon atom, at least one heteroatom as a ring-forming atom, 1 to 10 carbon atoms, and at least one carbon-carbon double bond in the cyclic structure thereof. Examples of the C 1 -C 10  heterocycloalkenyl group include a 4,5-dihydro-1,2,3,4-oxatriazolyl group, a 2,3-dihydrofuranyl group, and a 2,3-dihydrothiophenyl group. The term “C 1 -C 10  heterocycloalkenylene group” as used herein refers to a divalent group having a structure corresponding to the C 1 -C 10  heterocycloalkenyl group. 
     The term “C 6 -C 60  aryl group” as used herein refers to a monovalent group having a carbocyclic aromatic system having six to sixty carbon atoms, and the term “C 6 -C 60  arylene group” as used herein refers to a divalent group having a carbocyclic aromatic system having six to sixty carbon atoms. Examples of the C 6 -C 60  aryl group are a phenyl group, a pentalenyl group, a naphthyl group, an azulenyl group, an indacenyl group, an acenaphthyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a perylenyl group, a pentaphenyl group, a heptalenyl group, a naphthacenyl group, a picenyl group, a hexacenyl group, a pentacenyl group, a rubicenyl group, a coronenyl group, and an ovalenyl group. When the C 6 -C 60  aryl group and the C 6 -C 60  arylene group each include two or more rings, the rings may be fused with each other. 
     The term “C 1 -C 60  heteroaryl group” as used herein refers to a monovalent group having a heterocyclic aromatic system that has, in addition to a carbon atom, at least one heteroatom as a ring-forming atom, and 1 to 60 carbon atoms. The term “C 1 -C 60  heteroarylene group” as used herein refers to a divalent group having a heterocyclic aromatic system that has, in addition to a carbon atom, at least one heteroatom as a ring-forming atom, and 1 to 60 carbon atoms. Examples of the C 1 -C 60  heteroaryl group are a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, a benzoquinolinyl group, an isoquinolinyl group, a benzoisoquinolinyl group, a quinoxalinyl group, a benzoquinoxalinyl group, a quinazolinyl group, a benzoquinazolinyl group, a cinnolinyl group, a phenanthrolinyl group, a phthalazinyl group, and a naphthyridinyl group. When the C 1 -C 60  heteroaryl group and the C 1 -C 60  heteroarylene group each include two or more rings, the rings may be fused with each other. 
     The term “monovalent non-aromatic fused polycyclic group” as used herein refers to a monovalent group (for example, having 8 to 60 carbon atoms) having two or more rings fused to each other, only carbon atoms as ring-forming atoms, and no aromaticity in its entire molecular structure. Examples of the monovalent non-aromatic fused polycyclic group are an indenyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, an indenophenanthrenyl group, and an indeno anthracenyl group. The term “divalent non-aromatic fused polycyclic group” as used herein refers to a divalent group having a structure corresponding to a monovalent non-aromatic fused polycyclic group. 
     The term “monovalent non-aromatic fused heteropolycyclic group” as used herein refers to a monovalent group (for example, having 1 to 60 carbon atoms) having two or more rings fused to each other, at least one heteroatom other than carbon atoms, as a ring-forming atom, and non-aromaticity in its entire molecular structure. Examples of the monovalent non-aromatic fused heteropolycyclic group are a pyrrolyl group, a thiophenyl group, a furanyl group, an indolyl group, a benzoindolyl group, a naphtho indolyl group, an isoindolyl group, a benzoisoindolyl group, a naphthoisoindolyl group, a benzosilolyl group, a benzothiophenyl group, a benzofuranyl group, a carbazolyl group, a dibenzosilolyl group, a dibenzothiophenyl group, a dibenzofuranyl group, an azacarbazolyl group, an azafluorenyl group, an azadibenzosilolyl group, an azadibenzothiophenyl group, an azadibenzofuranyl group, a pyrazolyl group, an imidazolyl group, a triazolyl group, a tetrazolyl group, an oxazolyl group, an isoxazolyl group, a thiazolyl group, an isothiazolyl group, an oxadiazolyl group, a thiadiazolyl group, a benzopyrazolyl group, a benzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzoxadiazolyl group, a benzothiadiazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, an imidazotriazinyl group, an imidazopyrazinyl group, an imidazopyridazinyl group, an indenocarbazolyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, a benzoindolocarbazolyl group, a benzocarbazolyl group, a benzonaphthofuranyl group, a benzonaphthothiophenyl group, a benzonaphthosilolyl group, a benzofurodibenzofuranyl group, a benzofurodibenzothiophenyl group, and a benzothienodibenzothiophenyl group. The term “divalent non-aromatic heterofused polycyclic group” as used herein refers to a divalent group having a structure corresponding to a monovalent non-aromatic heterofused polycyclic group. 
     The term “C 6 -C 60  aryloxy group” as used herein indicates —OA 102  (wherein A 102  is the C 6 -C 60  aryl group), and the term “C 6 -C 60  arylthio group” as used herein indicates —SA 103  (wherein A 103  is the C 6 -C 60  aryl group). The term “C 7 -C 60  aryl alkyl group” used herein refers to -A 104 A 105  (wherein A 104  may be a C 1 -C 54  alkylene group, and A 105  may be a C 6 -C 59  aryl group), and the term C 2 -C 60  heteroaryl alkyl group” used herein refers to -A 106 A 107  (wherein A 106  may be a C 1 -C 59  alkylene group, and A 107  may be a C 1 -C 59  heteroaryl group). 
     The term “C 1 -C 60  heteroaryloxy group” used herein indicates —OA 104  (wherein A 108  is the C 1 -C 60  heteroaryl group), and the C 1 -C 60  heteroarylthio group indicates —SA 105  (wherein A 109  is the C 1 -C 60  heteroaryl group). 
     The term “R 10a ” as used herein refers to: 
     deuterium (-D), —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof; 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, or a C 2 -C 60  heteroaryl alkyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group, a C2-C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 )(Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ), 
     wherein Q 11  to Q 13 , Q 21  to Q 23 , and Q 31  to Q 33  may each independently be: hydrogen; deuterium; —F; —Cl; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 60  alkyl group; a C 2 -C 60  alkenyl group; a C 2 -C 60  alkynyl group; a C 1 -C 60  alkoxy group; a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, each unsubstituted or substituted with zo deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 60  alkoxy group, a phenyl group, a biphenyl group, or any combination thereof; a C 7 -C 60  aryl alkyl group; or a C 2 -C 60  heteroaryl alkyl group. 
     The term “heteroatom” as used herein refers to any atom other than a carbon atom. Examples of the heteroatom are O, S, N, P, Si, B, Ge, Se, and any combination thereof. 
     The term “the third-row transition metal” used herein includes hafnium (Hf), tantalum (Ta), tungsten(W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), etc. 
     As used herein, the term “Ph” refers to a phenyl group, the term “Me” refers to a methyl group, the term “Et” refers to an ethyl group, the term “tert-Bu”, “ter-Bu” or “But” refers to a tert-butyl group, the term “OMe” refers to a methoxy group, and the term “Iso-Pr” refers to an isopropyl group. 
     The term “biphenyl group” as used herein refers to “a phenyl group substituted with a phenyl group.” In other words, the “biphenyl group” is a substituted phenyl group having a C 6 -C 60  aryl group as a substituent. 
     The term “terphenyl group” as used herein refers to “a phenyl group substituted with a biphenyl group.” In other words, the “terphenyl group” is a substituted phenyl group having, as a substituent, a C 6 -C 60  aryl group substituted with a C 6 -C 60  aryl group. 
     * and *′ as used herein, unless defined otherwise, each refer to a binding site to a neighboring atom in a corresponding formula or moiety. 
     Hereinafter, a compound and a light-emitting device including the same made according to the principles and certain embodiments of the invention will be described in detail with reference to Examples. Comparative Examples that differ from the Examples also will be described. The wording “B was used instead of A” used in describing Examples refers to that an identical molar equivalent of B was used in place of A. 
     EXAMPLES 
     Evaluation Example 1 
     Evaluation of Energy Characteristics 
     Triplet (T1) energy levels and band gap energy of the compounds of Table 1 were measured using low temperature photoluminescence (PL) and differential pulse voltammetry (DPV), and results thereof are shown in Table 1. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Compound 
                 T 1  (eV) 
                 Band gap (eV) 
               
               
                   
               
             
            
               
                 Compound 1  
                 3.08 
                 4.12 
               
               
                 Compound 6  
                 3.14 
                 3.58 
               
               
                 Compound 9  
                 2.89 
                 3.66 
               
               
                 Compound 19 
                 3.07 
                 4.12 
               
               
                 Compound 35 
                 3.04 
                 3.68 
               
               
                 Compound 38 
                 3.11 
                 3.91 
               
               
                 Compound 40 
                 3.24 
                 4.27 
               
               
                 Compound 41 
                 3.10 
                 4.01 
               
               
                   
               
            
           
         
       
     
     Example 1 
     An ITO glass substrate (25×25 mm, 15 Ω/□), which is an organic light-emitting device (OLED) glass (manufactured by Samsung-Corning of Asan, Republic of Korea) substrate, was subjected to ultrasonic cleaning sequentially using distilled water and isopropanol, followed by UV ozone cleaning for 30 minutes. The cleaned glass substrate, to which a transparent electrode line is attached, was mounted on a substrate holder of a vacuum deposition apparatus, and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HATCN) was deposited on the ITO electrode (anode) to form a hole injection layer having a thickness of 10 nm. Then, N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) was deposited on the hole injection layer to form a hole transport layer having a thickness of 40 nm. 
     9,9′,9″-triphenyl-9H,9′H,9″H-3,3′:6′3″-tercarbazole (TrisPCz) was deposited on the hole transport layer to form an electron blocking layer having a thickness of 10 nm, and Compound H-08 and E-10 (host), Compound S-13 (phosphorescent dopant) and Compound D-11 (delayed fluorescent dopant) were co-deposited to a weight ratio of 44.5:44.5:0.1:0.01 to form a first emission layer having a thickness of 25 nm. 
     Compound 1 was deposited on the first emission layer to form a spacing layer having a thickness of 0.5 nm, and the same material as that of the first emission layer was deposited on the spacing layer to form a second emission layer having a thickness of 5 nm. 
     9,9′-(2,8-dibenzothiophenediyl)bis-9H-carbazole (mCBT) was deposited on the second emission layer to a hole blocking layer having a thickness of 10 nm, and 2,7-di(2,2′-bipyridin-5-yl)triphenylene (BByTP) was deposited on the hole blocking layer to form an electron transport layer having a thickness of 40 nm. 
     LiF was deposited on the electron transport layer to form an electron injection layer having a thickness of 1 nm, and then Al was deposited on the electron injection layer to form a cathode having a thickness of 100 nm, thereby completing the manufacture of a light-emitting device. 
     
       
         
         
             
             
         
       
     
     Examples 2 to 4 and Comparative Examples 1 and 2 
     The light-emitting device of Examples 2 to 4 and Comparative Examples 1 and 2 were manufactured in the same manner as in Example 1, except that the compounds of Table 2 were each used to form an emission layer. In Comparative Example 1, a spacing layer was not formed. 
     Comparative Example 3 
     The light-emitting device of Comparative Example 3 was manufactured in the same manner as in Example 1, except that the spacing layer was deposited between the second emission layer and the hole blocking layer, not between the first emission layer and the second emission layer. 
     Example 5 
     A light-emitting device was manufactured in the same manner as in Example 1, except that the configurations of the first emission layer and the second emission layer were changed as below when the forming the emission layer. 
     Compound H-08 and E-10 (host), Compound S-13 (phosphorescent dopant) and Compound D-11 (delayed fluorescent dopant) were co-deposited to a weight ratio of 44.5:44.5:0.1:0.01 on an electron blocking layer to form a first emission layer having a thickness of 20 nm. 
     Compound 1 was deposited on the first emission layer to form a first spacing layer having a thickness of 1 nm, and the same material as that of the first emission layer was deposited on the first spacing layer to form a second emission layer having a thickness of 1 nm. Compound 1 was deposited on the second emission layer to form a second spacing layer having a thickness of 1 nm, and the same material as that of the first emission layer was deposited on the second layer to form a third emission layer having a thickness of 1 nm. Compound 1 was deposited on the third emission layer to form a third spacing layer having a thickness of 1 nm, and the same material as that of the first emission layer was deposited on the third spacing layer to form a fourth emission layer having a thickness of 5 nm. 
     Examples 6 to 8 
     A light-emitting device was manufactured in the same manner as in Example 5, except that the compounds of Table 2 were each used to form an emission layer. 
     Evaluation Example 2 
     The driving voltage, emission efficiency, lifespan (T95), and maximum emission wavelength (λmax) of the light-emitting devices manufactured according to Examples 1 to 8 and Comparative Examples 1 to 3 were measured using a source-measure unit sold under the trade designation SMU 236 from Keithley Instrument by Tektronix, Inc., of Beaverton, Oregon and a luminance meter sold under the trade designation PR650 from Konica Minolta, Inc. of Tokyo, Japan, and results thereof are shown in Table 2. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                 Driving 
                 Emission 
                   
                   
               
               
                   
                   
                   
                 Spacing 
                 voltage 
                 efficiency 
                 T 95   
                 λ max   
               
               
                   
                 Host 
                 Dopant 
                 Compound  
                 (V) 
                 (cd/A) 
                 (hr) 
                 (nm) 
               
               
                   
               
             
            
               
                 Example 1 
                 H-08, 
                 S-13, 
                 Compound 1 
                 4.7 
                 20 
                 140 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 2 
                 H-08, 
                 S-13, 
                 Compound 6 
                 4.6 
                 21 
                 120 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 3 
                 H-08, 
                 S-13, 
                 Compound 9 
                 4.6 
                 19 
                 130 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 4 
                 H-08, 
                 S-13, 
                 Compound 19 
                 4.8 
                 16 
                 110 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 5 
                 H-08, 
                 S-13, 
                 Compound 1 
                 4.7 
                 23 
                 160 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 6 
                 H-08, 
                 S-13, 
                 Compound 35 
                 4.8 
                 27 
                 150 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 7 
                 H-08, 
                 S-13, 
                 Compound 38 
                 4.9 
                 25 
                 140 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Example 8 
                 H-08, 
                 S-13, 
                 Compound 40 
                 4.7 
                 25 
                 130 
                 460 
               
               
                   
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 H-01, 
                 Compound  
                 No spacing layer 
                 4.5 
                 15 
                 100 
                 460 
               
               
                 Example 1 
                 E-01 
                 1 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 H-08, 
                 S-13, 
                 H-08 
                 4.7 
                 14 
                  80 
                 460 
               
               
                 Example 2 
                 E-10 
                 D-11 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 H-08, 
                 S-13, 
                 Compound 1 
                 5.5 
                 17 
                  80 
                 460 
               
               
                 Example 3 
                 E-10 
                 D-11 
               
               
                   
               
            
           
         
       
     
     Table 2 shows that the light-emitting devices constructed according to the principles and certain embodiment had significant and unexpectedly excellent emission efficiency and lifespan characteristics, and lower or equivalent driving voltage compared to the light-emitting devices of Comparative Examples 1 to 3. 
     Light-emitting devices constructed according to the principles and embodiments of the invention reduce or prevent deterioration of the emission layer material and have excellent lifespan characteristics. 
     Although certain embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concepts are not limited to such embodiments, but rather to the broader scope of the appended claims and various obvious modifications and equivalent arrangements as would be apparent to a person of ordinary skill in the art.