Patent Publication Number: US-2023140767-A1

Title: Light-emitting device and electronic apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0132692, filed on Oct. 6, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     One or more embodiments relate to a light-emitting device and an electronic apparatus including the same. 
     2. Description of the Related Art 
     Light-emitting devices are self-emissive devices that, as compared with devices of the related art, have wide viewing angles, high contrast ratios, short response times, and/or excellent or suitable characteristics in terms of luminance, driving voltage, and/or response speed. 
     In a light-emitting device, a first electrode is located on a substrate, and a hole transport region, an emission layer, an electron transport region, and a second electrode are sequentially formed 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 the holes and electrons, recombine in the emission layer to produce light. 
     SUMMARY 
     An aspect according to embodiments of the present disclosure is directed toward a device having improved efficiency compared to a related art device. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure. 
     According to an embodiment, a light-emitting device includes 
     a first electrode, 
     a second electrode facing the first electrode, and 
     an interlayer between the first electrode and the second electrode and including an emission layer, 
     wherein the second electrode includes a first layer including a first metal having a work function with an absolute value of 5.2 eV or less and a second metal having an electrical conductivity of 1×10 7  S/m or more, and a second layer consisting of the second metal having the electrical conductivity of 1×10 7  S/m or more, 
     the first metal and the second metal are different from each other, 
     a thickness of the first layer is from 1 Å to 30 Å, and 
     a thickness of the second layer is from 10 Å to 110 Å. 
     According to another embodiment, 
     an electronic apparatus includes the light-emitting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and enhancements of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a schematic view of a structure of a light-emitting device according to an embodiment; 
         FIG.  2    is a cross-sectional view of a light-emitting apparatus according to an embodiment; 
         FIG.  3    is a cross-sectional view of a light-emitting apparatus according to another embodiment; and 
         FIG.  4    is a graph showing sheet resistance values of electrodes of Example devices and Comparative Example devices. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in more detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout, and duplicative descriptions thereof may not be provided. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the drawings, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Throughout the disclosure, the expression “at least one of a, b or c” indicates only a, only b, only c, both (e.g., simultaneously) a and b, both (e.g., simultaneously) a and c, both (e.g., simultaneously) b and c, all of a, b, and c, or variations thereof. 
     In an electrode of a light-emitting device of the related art, because there is a trade-off relationship between an sheet resistance of the electrode and an absorption rate of the electrode, there is a limit to an increase in device efficiency. 
     Low sheet resistance is desirable or required to improve efficiency and IR drop (ohmic drop or voltage drop), and for this purpose, a thicker electrode is preferred (e.g., the electrode needs to be thick). However, a thick electrode leads to an increase in an absorption rate, thereby resulting in a decrease in light extraction efficiency. 
     In order to lower the absorption rate, there has been a method of reducing the electrode thickness, for example, by doping a small amount of Mg in the electrode. However, this has caused an increase in sheet resistance due to a decrease in the electrode thickness or instability of electrode film quality, thereby causing reliability issues. For example, when a ratio of Mg is reduced to approach pure Ag (e.g., for an Ag based electrode), sheet resistance is increased due to the deterioration of the film quality due to the absence (or insufficient amount) of Mg, and because Ag causes thermal aggregation and/or electro migration issues under high temperature and/or electric field. 
     In order to improve device efficiency, an electrode having a low sheet resistance and a low absorption rate even with a small thickness or, for example, a low Mg ratio, and having a reliability due to non-deterioration of film quality is desired or required. 
     A light-emitting device according to an embodiment includes: 
     a first electrode; 
     a second electrode facing the first electrode; and 
     an interlayer located between the first electrode and the second electrode and including an emission layer, 
     wherein the second electrode may include: a first layer including a first metal having a work function with an absolute value of 5.2 eV or less and a second metal having an electrical conductivity of 1×10 7  S/m or more; and a second layer including (e.g., consisting of) the second metal having the electrical conductivity of 1×10 7  S/m or more, 
     the first metal and the second metal may be different from each other, 
     a thickness of the first layer may be from 1 Å to 30 Å, and 
     a thickness of the second layer may be from 10 Å to 110 Å. 
     The first layer of the second electrode of the light-emitting device according to an embodiment may include a first metal having a work function with an absolute value of 5.2 eV or less and a second metal having an electrical conductivity of 1×10 7  S/m or more. In some embodiments, the first layer of the second electrode may consist of a first metal having a work function with an absolute value of 5.2 eV or less and a second metal having an electrical conductivity of 1×10 7  S/m or more. In an embodiment, the first metal and the second metal may be substantially uniformly mixed in the first layer. 
     The first layer ensures the film quality of a thin film of the second layer by improving the initial roughness. For example, the first layer serves as a seed layer of the second layer. 
     In an embodiment, the first metal may be selected from Mg, Ca, Li, Au, Al, Yb, Cu, Sm, and combinations thereof. 
     In an embodiment, the second metal may be selected from Ag, Au, Cu, Al, Mg, and combinations thereof. 
     In an embodiment, the first metal may be Mg, and the second metal may be Ag, Au, Cu, Al, or any combination thereof. 
     In an embodiment, the second metal may be Ag, and the first metal may be Mg, Ca, Li, Au, Al, Yb, Cu, Sm, or any combination thereof. 
     In an embodiment, the first metal may be Mg, and the second metal may be Ag. 
     A thickness of the first layer of the second electrode may be from about 1 Å to about 30 Å, and a thickness of the second layer may be from about 10 Å to about 110 Å. When the first layer includes a first metal having a work function with an absolute value of about 5.2 eV or less and a second metal having an electrical conductivity of about 1×10 7  S/m or more and is within the thickness range, and when the second layer includes (e.g., consists of) the second metal having an electrical conductivity of about 1×10 7  S/m or more and is within the thickness range, the first layer may sufficiently serve as a seed layer of the second layer to improve the initial roughness, thereby ensuring film quality of a thin film of the second layer. 
     In an embodiment, a sufficient thickness is desirable or required for the second layer (for example, a pure silver layer) formed in a plurality of nucleus sites formed on the first layer to have sufficient or high conductivity, and may be from about 10 Å to about 110 Å. 
     In an embodiment, a thickness of the second electrode may be from about 10 Å to about 130 Å. When a thickness of the second electrode is less than about 10 Å, substantially continuous film formation is difficult, and thus sheet resistance may increase, and when a thickness of the second electrode is greater than about 130 Å, an absorption rate may increase, and thus device efficiency may decrease. 
     In an embodiment, an amount (vol %) of the second metal in the first layer may be greater than an amount (vol %) of the first metal. When an amount (vol %) of the first metal in the first layer is greater than or equal to an amount (vol %) of the second metal, sheet resistance may increase or an absorption rate may increase, and as a result, efficiency may decrease. 
     In an embodiment, an amount of the second metal in the first layer may be equal to or greater than about 50 vol % and less than 100 vol %, and an amount of the first metal may be greater than 0 vol % and less than or equal to about 50 vol %, based on a total of 100 vol % of the first layer. In an embodiment, an amount of the second metal in the first layer may be about 98 vol %, and an amount of the first metal may be about 2 vol %. In an embodiment, an amount of the second metal in the first layer may be about 95 vol %, and an amount of the first metal may be about 5 vol %. In an embodiment, an amount of the second metal in the first layer may be about 93 vol %, and an amount of the first metal may be about 7 vol %. In an embodiment, an amount of the second metal in the first layer may be about 90 vol %, and an amount of the first metal may be about 10 vol %. In an embodiment, an amount of the second metal in the first layer may be about 50 vol %, and an amount of the first metal may be about 50 vol %. 
     In an embodiment, the first electrode may be an anode, the second electrode may be a cathode, the light-emitting device may further include: a hole transport region located between the first electrode and the emission layer and including a hole injection layer, a hole transport layer, an electron blocking layer, or any combination thereof; and/or an electron transport region located between the second electrode and the emission layer and including a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     The light-emitting device according to an embodiment may further include an electron injection layer between the second electrode and the emission layer. 
     In an embodiment, the electron injection layer may be in contact with the first layer of the second electrode. 
     In an embodiment, the electron injection layer may include an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof. 
     In an embodiment, the electron injection layer may include Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Y, Ce, Tb, Yb, Gd, or any combination thereof. 
     In an embodiment, the electron injection layer may include an organic material. 
     In an embodiment, the organic material may be a compound represented by Formula 601. 
       [Ar 601 ] xe11 -[(L 601 ) xe1 -R 601 ] xe21   Formula 601
 
     In Formula 601, 
     Ar 601  and L 601  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xe11 may be 1, 2, or 3, 
     xe1 may be 0, 1, 2, 3, 4, or 5, 
     R 601  may be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 601 )(Q 602 )(Q 603 ), —C(═O)(Q 601 ), —S(═O) 2 (Q 601 ), or —P(═O)(Q 601 )(Q 602 ), 
     Q 601  to Q 603  may each independently be the same as those described in connection with Q 1 , 
     xe21 may be 1, 2, 3, 4, or 5, and 
     at least one of Ar 601 , L 601 , or 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 . 
     In an embodiment, 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 organic material that may be included in the electron injection layer may be the following compound. 
     
       
         
         
             
             
         
       
     
     In an embodiment, a thickness of the electron injection layer may be from about 1 Å to about 100 Å. In an embodiment, a thickness of the electron injection layer may be from about 3 Å to about 90 Å. When the thickness of the electron injection layer is within the range described above, satisfactory electron injection characteristics may be obtained without a substantial increase in driving voltage. 
     When the electron injection layer includes an organic material and an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof, the alkali metal, the alkaline earth metal, the rare earth metal, the alkali metal-containing compound, the alkaline earth metal-containing compound, the rare earth metal-containing compound, the alkali metal complex, the alkaline earth metal complex, the rare earth metal complex, or any combination thereof may be uniformly or non-uniformly distributed in a matrix including the organic material. For more information on the electron injection layer, reference may be made to the following description. 
     In an embodiment, the second layer and the first layer of the second electrode may be in contact (e.g., in direct contact) with each other. The light-emitting device according to an embodiment may include a structure of an electron injection layer/first layer/second layer. In this case, the electron injection layer may be in contact with the electron transport layer, and the second layer may be in contact with the capping layer. The electron transport layer and the capping layer are described below. 
     In an embodiment, the interlayer may include m light-emitting units and m−1 charge-generating unit(s) between neighboring light-emitting units. Here, m may be a natural number from 1 to 10. 
     In an embodiment, the light-emitting device may include m−1 charge-generating unit(s), each between two neighboring light-emitting units among the m light-emitting units. 
     In an embodiment, when m is 2, a first electrode, a first light-emitting unit, a first charge-generating unit, a second charge-generating unit, and a second electrode may be sequentially arranged. In this case, the first light-emitting unit may be to emit a first-color light, the second light-emitting unit may be to emit a second-color light, and a maximum emission wavelength of the first-color light and a maximum emission wavelength of the second-color light may be identical to or different from each other. 
     In an embodiment, when m is 3, a first electrode, a first electrode, a first light-emitting unit, a first charge-generating unit, a second light-emitting unit, a second charge-generating unit, a third light-emitting unit, and a second electrode may be sequentially arranged. In this case, the first light-emitting unit may be to emit a first-color light, the second light-emitting unit may be to emit a second-color light, the third light-emitting unit may be to emit a third-color light, and a maximum emission wavelength of the first-color light, a maximum emission wavelength of the second-color light, and a maximum emission wavelength of the third-color light may be identical to or different from each other. 
     In an embodiment, when m is 4, a first electrode, a first light-emitting unit, a first charge-generating unit, a second light-emitting unit, a second charge-generating unit, a third light-emitting unit, a third charge-generating unit, a fourth light-emitting unit, and a second electrode may be sequentially arranged. In this case, the first light-emitting unit may be to emit a first-color light, the second light-emitting unit may be to emit a second-color light, the third light-emitting unit may be to emit a third-color light, the fourth light-emitting unit may be to emit a fourth-color light, and a maximum emission wavelength of the first-color light, a maximum emission wavelength of the second-color light, a maximum emission wavelength of the third-color light, and a maximum emission wavelength of the fourth-color light may be identical to or different from each other. 
     An electronic apparatus according to one or more embodiments may include the light-emitting device. 
     In an embodiment, the electronic apparatus may further include a thin-film transistor, 
     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 of the thin-film transistor. 
     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. 
     In an embodiment, the electronic apparatus may further include quantum dots. In an embodiment, the electronic apparatus may include a color conversion layer, and the color conversion layer may include quantum dots. 
     The term “interlayer” as utilized herein refers to a single layer and/or all of a plurality of layers located between the first electrode and the second electrode of the light-emitting device. 
     Description of FIG.  1   
       FIG.  1    is a schematic cross-sectional view of a light-emitting device  10  according to an embodiment. The light-emitting device  10  includes a first electrode  110 , an interlayer  130 , and a second electrode  150 . 
     Hereinafter, a structure of the light-emitting device  10  according to an embodiment and a 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 and/or a plastic substrate may be utilized. In an embodiment, the substrate may be a flexible substrate, and may include plastics with excellent or suitable heat resistance and durability, such as polyimide, polyethylene terephthalate (PET), polycarbonate, polyethylene naphthalate, polyarylate (PAR), polyetherimide, or any combination thereof. 
     The first electrode  110  may be formed by, for example, depositing or sputtering a material for forming the first electrode  110  on the substrate. When the first electrode  110  is an anode, a material for forming the first electrode  110  may be a high work function material that can suitably facilitate injection of holes. 
     The first electrode  110  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. When the first electrode  110  is a transmissive electrode, a material for forming the first electrode  110  may include indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), zinc oxide (ZnO), or any combination thereof. In one or more embodiments, when the first electrode  110  is a semi-transmissive electrode or a reflective electrode, magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), magnesium-silver (Mg—Ag), or any combination thereof may be utilized as a material for forming the first electrode  110 . 
     The first electrode  110  may have a single-layered structure consisting of a single layer or a multilayer structure including a plurality of layers. For example, the first electrode  110  may have a three-layered structure of ITO/Ag/ITO. 
     Interlayer  130   
     The interlayer  130  may be located on the first electrode  110 . The interlayer  130  may include an emission layer. 
     In an embodiment, 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 . 
     In an embodiment, the interlayer  130  may further include one or more metal-containing compounds such as one or more organometallic compounds, one or more inorganic materials such as quantum dots, and/or the like, in addition to one or more suitable organic materials. 
     In an embodiment, the interlayer  130  may include, i) two or more light-emitting units sequentially stacked between the first electrode  110  and the second electrode  150 , and ii) a charge generation layer between two adjacent light-emitting units. When the interlayer  130  includes the two or more emitting units 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 including (e.g., 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. 
     In an embodiment, 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, constituting layers are sequentially stacked from the first electrode  110  in the respective stated order. 
     The hole transport region may include a compound represented by Formula 201, a compound represented by Formula 202, or any combination thereof: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 201 and 202, 
     L 201  to L 204  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     L 205  may be *—O—*′, *—S—*′, *—N(Q 201 )-*′, a C 1 -C 20  alkylene group unsubstituted or substituted with at least one R 10a , a C 2 -C 20  alkenylene group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xa1 to xa4 may each independently be an integer from 0 to 5, 
     xa5 may be an integer from 1 to 10, 
     R 201  to R 204  and Q 201  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     R 201  and R 202  may optionally be linked to each other, via a single bond, a C 1 -C 5  alkylene group unsubstituted or substituted with at least one R 10a , or a C 2 -C 5  alkenylene group unsubstituted or substituted with at least one R 10a , to form a C 8 -C 60  polycyclic group (for example, a carbazole group and/or the like) unsubstituted or substituted with at least one R 10a  (for example, Compound HT16), 
     R 203  and R 204  may optionally be linked to each other, via a single bond, a C 1 -C 5  alkylene group unsubstituted or substituted with at least one R 10a , or a C 2 -C 5  alkenylene group unsubstituted or substituted with at least one R 10a , to form a C 8 -C 60  polycyclic group unsubstituted or substituted with at least one R 10a , and 
     na1 may be an integer from 1 to 4. 
     In an embodiment, each of Formulae 201 and 202 may include at least one of the groups represented by Formulae CY201 to CY217. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     R 10b  and R 10c  in Formulae CY201 to CY217 are respectively the same as those described in connection with R 10a , ring CY 201  to ring CY 204  may each independently be a C 3 -C 20  carbocyclic group or a C 1 -C 20  heterocyclic group, and at least one hydrogen in Formulae CY201 to CY217 may be unsubstituted or substituted with R 10a  as described above. 
     In an embodiment, ring CY 201  to ring CY 204  in Formulae CY201 to CY217 may each independently be a benzene group, a naphthalene group, a phenanthrene group, or an anthracene group. 
     In an embodiment, each of Formulae 201 and 202 may include at least one of the groups represented by Formulae CY201 to CY203. 
     In an embodiment, Formula 201 may include at least one of the groups represented by Formulae CY201 to CY203 and at least one of the groups represented by Formulae CY204 to CY217. 
     In an embodiment, xa1 in Formula 201 may be 1, R 201  may be a group represented by one of Formulae CY201 to CY203, xa2 may be 0, and R 202  may be a group represented by one of Formulae CY204 to CY207. 
     In an embodiment, each of Formulae 201 and 202 may not include (e.g., may exclude) any of the groups represented by Formulae CY201 to CY203. 
     In an embodiment, each of Formulae 201 and 202 may not include (e.g., may exclude) any of the groups represented by Formulae CY201 to CY203, and may include at least one of the groups represented by Formulae CY204 to CY217. 
     In an embodiment, each of Formulae 201 and 202 may not include (e.g., may exclude) any of the groups represented by Formulae CY201 to CY217. 
     In an embodiment, the hole transport region may include one of Compounds HT1 to HT46, m-MTDATA, TDATA, 2-TNATA, NPB(NPD), p-NPB, TPD, Spiro-TPD, Spiro-NPB, methylated NPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzenesulfonic acid (PANI/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), polyaniline/poly(4-styrenesulfonate) (PANI/PSS), or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the hole transport region may be in a range of about 50 Å to about 10,000 Å, for example, about 100 Å to about 4,000 Å. When the hole transport region includes a hole injection layer, a hole transport layer, or any combination thereof, a thickness of the hole injection layer may be in a range of about 100 Å to about 9,000 Å, for example, about 100 Å to about 1,000 Å, and a thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, for example, about 100 Å to about 1,500 Å. When the thicknesses of the hole transport region, the hole injection layer and the hole transport layer are within 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 from the emission layer, and the electron blocking layer may block or reduce the leakage of electrons from the emission layer to the hole transport region. Materials that may be included in the hole transport region may be included in the emission auxiliary layer and the electron blocking layer. 
     p-Dopant 
     The hole transport region may further include, in addition to 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 including (e.g., consisting of) a charge-generation material). 
     The charge-generation material may be, for example, a p-dopant. 
     In an embodiment, a 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 (to be described in more detail below), or any combination thereof. 
     Non-limiting examples of the quinone derivative may include TCNQ, F4-TCNQ, and the like. 
     Non-limiting examples of the cyano group-containing compound may include HAT-CN, a compound represented by Formula 221 below, and the like. 
     
       
         
         
             
             
         
       
     
     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; —CI; —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. 
     Non-limiting examples of the metal may include an alkali metal (for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and/or the like.); an alkaline earth metal (for example, beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and/or the like); 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), and/or the like); a post-transition metal (for example, zinc (Zn), indium (In), tin (Sn), and/or the like); 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), and/or the like). 
     Non-limiting examples of the metalloid may include silicon (Si), antimony (Sb), and tellurium (Te). 
     Non-limiting examples of the non-metal may include oxygen (O) and halogen (for example, F, Cl, Br, I, etc.). 
     In an embodiment, non-limiting examples of the compound containing element EL1 and element EL2 may include a metal oxide, a metal halide (for example, a metal fluoride, a metal chloride, a metal bromide, and/or a metal iodide), a metalloid halide (for example, a metalloid fluoride, a metalloid chloride, a metalloid bromide, and/or a metalloid iodide), a metal telluride, or any combination thereof. 
     Non-limiting examples of the metal oxide may include tungsten oxide (for example, WO, W 2 O 3 , WO 2 , WO 3 , W 2 O 5 , etc.), vanadium oxide (for example, VO, V 2 O 3 , VO 2 , V 2 O 5 , etc.), molybdenum oxide (MoO, Mo 2 O 3 , MoO 2 , MoO 3 , Mo 2 O 5 , etc.), and rhenium oxide (for example, ReO 3 , etc.). 
     Non-limiting examples of the metal halide may include alkali metal halide, alkaline earth metal halide, transition metal halide, post-transition metal halide, and lanthanide metal halide. 
     Non-limiting examples of the alkali metal halide may include LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. 
     Non-limiting examples of the alkaline earth metal halide may include BeF 2 , MgF 2 , CaF 2 , SrF 2 , BaF 2 , BeCl 2 , MgCl 2 , CaCl 2 , SrCl 2 , BaCl 2 , BeBr 2 , MgBr 2 , CaBr 2 , SrBr 2 , BaBr 2 , BeI 2 , MgI 2 , CaI 2 , SrI 2 , and BaI 2 . 
     Non-limiting examples of the transition metal halide may include titanium halide (for example, TiF 4 , TiCl 4 , TiBr 4 , Til 4 , etc.), zirconium halide (for example, ZrF 4 , ZrCl 4 , ZrBr 4 , ZrI 4 , etc.), hafnium halide (for example, HfF 4 , HfCl 4 , HfBr 4 , Hfl 4 , etc.), vanadium halide (for example, VF 3 , VCl 3 , VBr 3 , VI 3 , etc.), niobium halide (for example, NbF 3 , NbCl 3 , NbBr 3 , NbI 3 , etc.), tantalum halide (for example, TaF 3 , TaCl 3 , TaBr 3 , TaI 3 , etc.), chromium halide (for example, CrF 3 , CrCl 3 , CrBr 3 , CrI 3 , etc.), molybdenum halide (for example, MoF 3 , MoCl 3 , MoBr 3 , MoI 3 , etc.), tungsten halide (for example, WF 3 , WCl 3 , WBr 3 , WI 3 , etc.), manganese halide (for example, MnF 2 , MnCl 2 , MnBr 2 , MnI 2 , etc.), technetium halide (for example, TcF 2 , TcCl 2 , TcBr 2 , TcI 2 , etc.), rhenium halide (for example, ReF 2 , ReCl 2 , ReBr 2 , ReI 2 , etc.), iron halide (for example, FeF 2 , FeCl 2 , FeBr 2 , FeI 2 , etc.), ruthenium halide (for example, RuF 2 , RuCl 2 , RuBr 2 , RuI 2 , etc.), osmium halide (for example, OsF 2 , OsCl 2 , OsBr 2 , OsI 2 , etc.), cobalt halide (for example, CoF 2 , CoCl 2 , CoBr 2 , CoI 2 , etc.), rhodium halide (for example, RhF 2 , RhCl 2 , RhBr 2 , RhI 2 , etc.), iridium halide (for example, IrF 2 , IrCl 2 , IrBr 2 , IrI 2 , etc.), nickel halide (for example, NiF 2 , NiCl 2 , NiBr 2 , NiI 2 , etc.), palladium halide (for example, PdF 2 , PdCl 2 , PdBr2, Pd12, etc.), platinum halide (for example, PtF 2 , PtCl 2 , PtBr 2 , PtI 2 , etc.), copper halide (for example, CuF, CuCl, CuBr, CuI, etc.), silver halide (for example, AgF, AgCl, AgBr, AgI, etc.), and gold halide (for example, AuF, AuCl, AuBr, AuI, etc.). 
     Non-limiting examples of the post-transition metal halide may include zinc halide (for example, ZnF 2 , ZnCl 2 , ZnBr 2 , ZnI 2 , etc.), indium halide (for example, InI3, etc.), and tin halide (for example, SnI 2 , etc.). 
     Non-limiting examples of the lanthanide metal halide may include YbF, YbF 2 , YbF 3 , SmF 3 , YbCl, YbCl 2 , YbCl 3  SmCl 3 , YbBr, YbBr 2 , YbBr 3 , SmBr 3 , YbI, YbI 2 , YbI 3 , and SmI 3 . 
     Non-limiting examples of the metalloid halide may include antimony halide (for example, SbCl 5 , etc.). 
     Non-limiting examples of the metal telluride may include alkali metal telluride (for example, Li 2 Te, Na 2 Te, K 2 Te, Rb 2 Te, Cs 2 Te, etc.), alkaline earth metal telluride (for example, BeTe, MgTe, CaTe, SrTe, BaTe, etc.), transition metal telluride (for example, TiTe 2 , ZrTe 2 , HfTe 2 , V 2 Te 3 , Nb 2 Te 3 , Ta 2 Te 3 , Cr 2 Te 3 , Mo 2 Te 3 , W 2 Te 3 , MnTe, TcTe, ReTe, FeTe, RuTe, OsTe, CoTe, RhTe, IrTe, NiTe, PdTe, PtTe, Cu 2 Te, CuTe, Ag 2 Te, AgTe, Au 2 Te, etc.), post-transition metal telluride (for example, ZnTe, etc.), and lanthanide metal telluride (for example, LaTe, CeTe, PrTe, NdTe, PmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, etc.). 
     Emission Layer in Interlayer  130   
     When the light-emitting device  10  is a full-color light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and/or a blue emission layer, according to a sub-pixel. In an embodiment, the emission layer may have a stacked structure of two or more layers of a red emission layer, a green emission layer, and a blue emission layer, in which the two or more layers contact each other or are separated from each other. In one or more embodiments, the emission layer may include two or more materials of a red light-emitting material, a green light-emitting material, and a blue light-emitting material, in which the two or more materials are mixed 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. 
     An amount of the dopant in the emission layer may be from about 0.01 parts by weight to about 15 parts by weight based on 100 parts by weight of the host. 
     In an embodiment, the emission layer may include a delayed fluorescence material. The delayed fluorescence material may act as a host or a dopant in the emission layer. 
     A thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. When the thickness of the emission layer is within these ranges, excellent or suitable light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Host 
     The host may include a compound represented by Formula 301: 
       [Ar 301 ] xb11 -[(L 301 ) xb1 -R 301 ] xb21   Formula 301
 
     wherein, in Formula 301, 
     Ar 301  and L 301  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xb11 may be 1, 2, or 3, 
     xb1 may be an integer from 0 to 5, 
     R 301  may be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkenyl group unsubstituted or substituted with at least one R 10a , a C 2 -C 60  alkynyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 301 )(Q 302 )(Q 303 ), —N(Q 301 )(Q 302 ), —B(Q 301 )(Q 302 ), —C(═O)(Q 301 ), —S(═O) 2 (Q 301 ), or —P(═O)(Q 301 )(Q 302 ), 
     xb21 may be an integer from 1 to 5, and 
     Q 301  to Q 303  may each independently be the same as described in connection with Q 1 . 
     In an embodiment, 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: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 301-1 and 301-2, 
     ring A 301  to ring A 304  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     X 301  may be O, S, N-[(L 304 ) xb4 -R 304 ], C(R 304 )(R 305 ), or Si(R 304 )(R 305 ), 
     xb22 and xb23 may each independently be 0, 1, or 2, 
     L 301 , xb1, and R 301  may respectively be the same as those described in the present specification, 
     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  may each independently be the same as described in connection with R 301 . 
     In an embodiment, the host may include an alkaline 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), a 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, but embodiments are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Phosphorescent Dopant 
     The phosphorescent dopant may include at least one transition metal as a central metal (e.g., a central metal atom). 
     The phosphorescent dopant may include a monodentate ligand, a bidentate ligand, a tridentate ligand, a tetradentate ligand, a pentadentate ligand, a hexadentate ligand, or any combination thereof. 
     The phosphorescent dopant may be electrically neutral. 
     In an embodiment, the phosphorescent dopant may include an organometallic compound represented by Formula 401: 
     
       
         
         
             
             
         
       
     
     wherein, in Formulae 401 and 402, 
     M may be a transition metal (for example, iridium (Ir), platinum (Pt), palladium (Pd), osmium (Os), titanium (Ti), gold (Au), hafnium (Hf), europium (Eu), terbium (Tb), rhodium (Rh), rhenium (Re), or thulium (Tm)), 
     L 401  may be a ligand represented by Formula 402, and xc1 may be 1, 2, or 3, wherein, when xc1 is 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, wherein, when xc2 is 2 or more, two or more of L 402 (s) may be identical to or different from each other, 
     X 401  and X 402  may each independently be nitrogen or carbon, 
     ring A 401  and ring A 402  may each independently be a C 3 -C 60  carbocyclic group or a C 1 -C 60  heterocyclic group, 
     T 401  may be a single bond, —O—, —S—, —C(═O)—, —N(Q 411 )-, —C(Q 411 )(Q 412 )-, —C(Q 411 )=C(Q 412 )-, —C(Q 411 )=, or =C═, 
     X 403  and X 404  may each independently be a chemical bond (for example, a covalent bond or a coordinate bond), O, S, N(Q 413 ), B(Q 413 ), P(Q 413 ), C(Q 413 )(Q 414 ), or Si(Q 413 )(Q 414 ), 
     Q 411  to Q 414  may each independently be the same as described in connection with Q 1  (to be described in more detail below), 
     R 401  and R 402  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group unsubstituted or substituted with at least one R 10a , a C 1 -C 20  alkoxy group unsubstituted or substituted with at least one R 10a , a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 401 )(Q 402 )(Q 403 ), —N(Q 401 )(Q 402 ), —B(Q 401 )(Q 402 ), —C(═O)(Q 401 ), —S(═O) 2 (Q 401 ), or —P(═O)(Q 401 )(Q 402 ), 
     Q 401  to Q 403  may each independently be the same as those described in connection with Q 1 , 
     xc11 and xc12 may each independently be an integer from 0 to 10, and 
     * and *′ in Formula 402 each indicate a binding site to M in Formula 401. 
     In an embodiment, in Formula 402, i) X 401  may be nitrogen, and X 402  may be carbon, or ii) each of X 401  and X 402  may be nitrogen. 
     In an embodiment, when xc1 in Formula 401 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  in two or more of L 401 (s) 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  may each independently be the same as described in connection with T 401 . 
     L 402  in Formula 401 may be an organic ligand. In an embodiment, L 402  may include a halogen group, a diketone group (for example, an acetylacetonate group), a carboxylic acid group (for example, a picolinate group), —C(═O), an isonitrile group, a —CN group, a phosphorus group (for example, a phosphine group, a phosphite group, etc.), or any combination thereof. 
     The phosphorescent dopant may include, for example, one of Compounds PD1 to PD39, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Fluorescent Dopant 
     The fluorescent dopant may include an amine group-containing compound, a styryl group-containing compound, or any combination thereof. 
     In an embodiment, the fluorescent dopant may include a compound represented by Formula 501: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 501, 
     Ar 501 , L 501  to L 503 , R 501 , and R 502  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xd1 to xd3 may each independently be 0, 1, 2, or 3, and 
     xd4 may be 1, 2, 3, 4, 5, or6. 
     In an embodiment, Ar 501  in Formula 501 may be a condensed cyclic group (for example, an anthracene group, a chrysene group, and/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 Fluorescence Material 
     The emission layer may include a delayed fluorescence material. 
     In some embodiments, the delayed fluorescence material may be selected from compounds capable of emitting delayed fluorescence based on a delayed fluorescence emission mechanism. 
     The delayed fluorescence material included in the emission layer may act (e.g., serve) as a host or a dopant, depending on the type or kind of other materials included in the emission layer. 
     In an embodiment, a difference between the triplet energy level (eV) of the delayed fluorescence material and the singlet energy level (eV) of the delayed fluorescence material may be equal to or greater than 0 eV and equal to or less than 0.5 eV. When the difference between the triplet energy level (eV) of the delayed fluorescence material and the singlet energy level (eV) of the delayed fluorescence material satisfies the above-described range, up-conversion from the triplet state to the singlet state in the delayed fluorescence materials may effectively occur, and thus, the luminescence efficiency of the light-emitting device  10  may be improved. 
     In an embodiment, the delayed fluorescence material may include i) a material including at least one electron donor (for example, a π electron-rich C 3 -C 60  cyclic group, such as a carbazole group) and at least one electron acceptor (for example, a sulfoxide group, a cyano group, and/or a π electron-deficient nitrogen-containing C 1 -C 60  cyclic group), and/or ii) a material including a C 8 -C 60  polycyclic group in which two or more cyclic groups are condensed while sharing boron (B). 
     Non-limiting examples of the delayed fluorescence material may include at least one of the following Compounds DF1 to DF9: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Quantum Dot 
     In the present specification, the term “quantum dot” refers to a crystal of a semiconductor compound, and the quantum dot may include any suitable material capable of emitting light of one or more suitable emission wavelengths according to the size of the crystal. 
     A diameter of the quantum dot may be, for example, in a range of about 1 nm to about 10 nm. 
     The quantum dot may be synthesized by a wet chemical process, a metal organic (e.g., organometallic) chemical vapor deposition process, a molecular beam epitaxy 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. Accordingly, through a process which is more easily performed at low costs compared to a vapor deposition methods (such as a metal organic chemical vapor deposition (MOCVD) process and/or a molecular beam epitaxy (MBE) process), the growth of quantum dot particles may be controlled. 
     The quantum dot may include: a Group II-VI semiconductor compound; a Group III-V semiconductor compound; a Group III-VI semiconductor compound; a Group I-III-VI semiconductor compound; a Group IV-VI semiconductor compound; a Group IV element or compound; or any combination thereof. 
     Non-limiting examples of the Group II-VI semiconductor compound may include: a binary compound, such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, and/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, and/or MgZnS; a quaternary compound, such as CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and/or HgZnSTe; and any combinations thereof. 
     Non-limiting examples of the Group III-V semiconductor compound may include: a binary compound, such as GaN, GaP, GaAs, GaSb, AlN, AIP, AIAs, AISb, InN, InP, InAs, and/or InSb; a ternary compound, such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AINP, AINAs, AINSb, AIPAs, AIPSb, InGaP, InNP, InAIP, InNAs, InNSb, InPAs, and/or InPSb; a quaternary compound, such as GaAINP, GaAINAs, GaAINSb, GaAIPAs, GaAIPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GalnPSb, InAINP, InAINAs, InAINSb, InAIPAs, and/or InAIPSb; and any combinations thereof. In an embodiment, the Group III-V semiconductor compound may further include one or more Group II elements. Non-limiting examples of the Group III-V semiconductor compound further including one or more Group II elements may include InZnP, InGaZnP, InAIZnP, and the like. 
     Non-limiting examples of the Group III-VI semiconductor compound may include: a binary compound, such as GaS, GaSe, Ga 2 Se 3 , GaTe, InS, InSe, In 2 S 3 , In 2 Se 3 , InTe, and/or the like; a ternary compound, such as InGaS 3 , InGaSe 3 , and/or the like; and any combinations thereof. 
     Non-limiting examples of the Group I-III-VI semiconductor compound may include: a ternary compound, such as AgInS, AgInS 2 , CuInS, CuInS 2 , CuGaO 2 , AgGaO 2 , and/or AgAlO 2 ; and any combinations thereof. 
     Non-limiting examples of the Group IV-VI semiconductor compound may include: a binary compound, such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, and/or the like; a ternary compound, such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and/or the like; a quaternary compound, such as SnPbSSe, SnPbSeTe, SnPbSTe, and/or the like; and any combinations thereof. 
     The Group IV element or compound may include: a single element compound, such as Si and/or Ge; a binary compound, such as SiC and/or SiGe; or any combination thereof. 
     Each element included in a multi-element compound such as the binary compound, the ternary compound and/or the quaternary compound, may exist in a particle with a substantially uniform concentration or non-uniform concentration (e.g., substantially non-uniform concentration). 
     In an embodiment, the quantum dot may have a single structure or a dual core-shell structure. When the quantum dot has a single structure, the concentration of each element included in the corresponding quantum dot is substantially uniform. In an embodiment, when the quantum dot has the dual core-shell structure, a material contained in the core and a material contained in the shell may be different from each other. 
     The shell of the quantum dot may act (e.g., serve) as a protective layer to prevent or reduce 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 element presented in the interface between the core and the shell of the quantum dot may have a concentration gradient that decreases toward the center of the quantum dot. 
     Non-limiting examples of the shell of the quantum dot may be an oxide of metal, metalloid, or non-metal, a semiconductor compound, and any combinations thereof. Non-limiting examples of the oxide of metal, metalloid, or non-metal may include: a binary compound, such as SiO 2 , Al 2 O 3 , TiO 2 , ZnO, MnO, Mn 2 O 3 , Mn 3 O 4 , CuO, FeO, Fe 2 O 3 , Fe 3 O 4 , CoO, Co 3 O 4 , and/or NiO; a ternary compound, such as MgAl 2 O 4 , CoFe 2 O 4 , NiFe 2 O 4 , and/or CoMn 2 O 4 ; and any combinations thereof. Non-limiting examples of the semiconductor compound may include, as described herein, a Group II-VI semiconductor compound, a Group III-V semiconductor compound, a Group III-VI semiconductor compound, a Group I-III-VI semiconductor compound, a Group IV-VI semiconductor compound, and any combinations thereof. In some embodiments, the semiconductor compound may include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AIAs, AIP, AISb, or any combination thereof. 
     A full width at half maximum (FWHM) of an emission wavelength spectrum of the quantum dot may be about 45 nm or less, for example, about 40 nm or less, or, about 30 nm or less, and within these ranges, color purity and/or color reproducibility may be increased. In some embodiments, because the light emitted through the quantum dot is emitted in all directions, a wide viewing angle can be obtained. 
     In some embodiments, the quantum dot may be a spherical particle, a pyramidal particle, a multi-arm particle, a cubic nanoparticle, a nanotube particle, a nanowire particle, a nanofiber particle, or a nanoplate particle. 
     Because the energy band gap can be adjusted by controlling the size of the quantum dot, light having one or more suitable wavelength bands can be obtained from the quantum dot emission layer. Therefore, by utilizing quantum dots of different sizes, a light-emitting device that emits light of one or more suitable 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 some embodiments, the size of the quantum dot may be configured to emit white light by combining light of one or more suitable colors. 
     Electron Transport Region in Interlayer  130   
     The electron transport region may have: i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer including (e.g., 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 hole blocking 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 or a hole blocking layer/electron transport layer/electron injection layer structure, wherein, in each structure, constituting layers are sequentially stacked from the emission layer in the respective stated order. 
     The electron transport region (for example, the hole blocking 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 L 601  may each independently be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , 
     xe11 may be 1, 2, or 3, 
     xe1 may be 0, 1, 2, 3, 4, or 5, 
     R 601  may be a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a , —Si(Q 601 )(Q 602 )(Q 603 ), —C(═O)(Q 601 ), —S(═O) 2 (Q 601 ), or —P(═O)(Q 601 )(Q 602 ), 
     Q 601  to Q 603  may each independently be the same as described in connection with Q 1 , 
     xe21 may be 1, 2, 3, 4, or 5, and 
     at least one of Ar 601 , L 601 , or 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 . 
     In an embodiment, when xe11 in Formula 601 is 2 or more, two or more of Ar 601 (s) may be linked to each other via a single bond. 
     In 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: 
     
       
         
         
             
             
         
       
     
     wherein, in Formula 601-1, 
     X 614  may be N or C(R 614 ), X 615  may be N or C(R 615 ), X 616  may be N or C(R 616 ), and at least one of X 614  to X 616  may be N, 
     L 611  to L 613  may each independently be the same as described in connection with L 601 , 
     xe611 to xe613 may each independently be the same as described in connection with xe1, 
     R 611  to R 613  may each independently be the same as described in connection with R 601 , and 
     R 614  to R 616  may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a C 3 -C 60  carbocyclic group unsubstituted or substituted with at least one R 10a , or a C 1 -C 60  heterocyclic group unsubstituted or substituted with at least one R 10a . 
     In an embodiment, xe1 and xe611 to xe613 in Formulae 601 and 601-1 may each independently be 0, 1, or 2. 
     The electron transport region may include one of Compounds ET1 to ET45, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), Alq 3 , BAIq, TAZ, NTAZ, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The thickness of the electron transport region may be in a range of about 100 Angstroms (Å) to about 5,000 Å, for example, about 160 Å to about 4,000 Å. When the electron transport region includes a hole blocking layer, an electron transport layer, or any combination thereof, a thickness of the hole blocking layer may be from about 20 Å to about 1,000 Å, for example, from about 30 Å to about 300 Å, and a thickness of the electron transport layer may be from about 100 Å to about 1,000 Å, for example, from about 150 Å to about 500 Å. When the thicknesses of the hole blocking layer and/or electron transport layer are within the ranges described above, satisfactory electron-transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The electron transport region (for example, the electron transport layer in the electron transport region) may further include, in addition to the materials described above, a metal-containing material. 
     The metal-containing material may include an alkali metal complex, an alkaline earth metal complex, or any combination thereof. A metal ion of the alkali metal complex may be a Li ion, a Na ion, a K ion, a Rb ion, or a Cs ion, and a metal ion of the alkaline earth metal complex may be a Be ion, a Mg ion, a Ca ion, a Sr ion, or a Ba ion. A ligand coordinated with the metal ion of the alkali metal complex or the alkaline earth-metal complex may include 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. 
     In an embodiment, the metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (LiQ) or ET-D2: 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer that facilitates the injection of electrons from the second electrode  150 . The electron injection layer may be in direct contact with the second electrode  150 . 
     The electron injection layer may have: i) a single-layered structure consisting of a single layer consisting of a single material, ii) a single-layered structure consisting of a single layer including (e.g., consisting of) a plurality of different materials, or iii) a multi-layered structure including a plurality of layers including different materials. 
     As described above, the electron injection layer may include an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof. 
     The alkali metal-containing compound, the alkaline earth metal-containing compound, and the rare earth metal-containing compound may include oxide(s), halide(s) (for example, fluoride(s), chloride(s), bromide(s), and/or iodide(s)), and/or telluride(s) 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 oxide(s) (such as Li 2 O, Cs 2 O, and/or K 2 O), alkali metal halide(s) (such as LiF, NaF, CsF, KF, LiI, NaI, CsI, and/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), and/or the like. The rare earth metal-containing compound may include YbF 3 , ScF 3 , Sc 2 O 3 , Y 2 O 3 , Ce 2 O 3 , GdF 3 , TbF 3 , YbI 3 , ScI 3 , TbI 3 , or any combination thereof. In an embodiment, the rare earth metal-containing compound may include lanthanide metal telluride. Non-limiting examples of the lanthanide metal telluride may include LaTe, CeTe, PrTe, NdTe, PmTe, SmTe, EuTe, GdTe, TbTe, DyTe, HoTe, ErTe, TmTe, YbTe, LuTe, La 2 Te 3 , Ce 2 Te 3 , Pr 2 Te 3 , Nd 2 Te 3 , Pm 2 Te 3 , Sm 2 Te 3 , Eu 2 Te 3 , Gd 2 Te 3 , Tb 2 Te 3 , Dy 2 Te 3 , Ho 2 Te 3 , Er 2 Te 3 , Tm 2 Te 3 , Yb 2 Te 3 , and Lu 2 Te 3 . 
     The alkali metal complex, the alkaline earth-metal complex, and the rare earth metal complex may include i) one of ions of the alkali metal, the alkaline earth metal, or 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 include (e.g., consist exclusively) of an alkali metal, an alkaline earth metal, a rare earth metal, an alkali metal-containing compound, an alkaline earth metal-containing compound, a rare earth metal-containing compound, an alkali metal complex, an alkaline earth metal complex, a rare earth metal complex, or any combination thereof, as described above. In one or more embodiments, the electron injection layer may further include an organic material (for example, a compound represented by Formula 601). 
     In an embodiment, the electron injection layer may include (e.g., consist of) i) an alkali metal-containing compound (for example, an alkali metal halide), or ii) a) an alkali metal-containing compound (for example, an alkali metal halide); and b) an alkali metal, an alkaline earth metal, a rare earth metal, or any combination thereof. In an embodiment, the electron injection layer may be a KI:Yb co-deposited layer, an RbI:Yb co-deposited layer, and/or the like. 
     A thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, and, for example, about 3 Å to about 90 Å. When the thickness of the electron injection layer is within the ranges described above, satisfactory electron injection characteristics may be obtained without a substantial increase in driving voltage. 
     Second Electrode  150   
     The second electrode  150  may be located on the interlayer  130  having such a structure. The second electrode  150  may be a cathode, which is an electron injection electrode, and is the same as described above. 
     Capping Layer 
     A first capping layer may be located outside the first electrode  110  (e.g., on the side opposite to the second electrode  150 ), and/or a second capping layer may be located outside the second electrode  150  (e.g., on the side opposite to the first electrode  110 ). In one embodiment, 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 emitted or 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 emitted or extracted toward the outside through the second electrode  150 , which is a semi-transmissive electrode or a transmissive electrode, and the second capping layer. 
     The first capping layer and the second capping layer may increase external luminescence efficiency according to the principle of constructive interference. Accordingly, the light extraction efficiency of the light-emitting device  10  may be increased, so that the emission efficiency of the light-emitting device  10  may be improved. 
     Each of the first capping layer and the second capping layer may include a material having a refractive index (at 589 nm) of about 1.5 to about 2.0 (for example, 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 a composite capping layer including an organic material and an inorganic material. 
     At least one of the first capping layer or the second capping layer may each independently include one or more carbocyclic compounds, one or more heterocyclic compounds, one or more amine group-containing compounds, one or more porphyrin derivatives, one or more phthalocyanine derivatives, one or more naphthalocyanine derivatives, one or more alkali metal complexes, one or more 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 or the second capping layer may (e.g., each independently) include an amine group-containing compound. 
     In an embodiment, at least one of the first capping layer or the second capping layer may (e.g., 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 or the second capping layer may (e.g., each independently) include one of Compounds HT28 to HT33, one of Compounds CP1 to CP6, β-NPB, or any combination thereof: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Electronic Apparatus 
     The light-emitting device may be included in one or more suitable electronic apparatuses. In an embodiment, the electronic apparatus including the light-emitting device may be a light-emitting apparatus, an authentication apparatus, and/or the like. 
     The electronic apparatus (for example, 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 plurality of subpixel areas, and the color conversion layer may include a plurality of color conversion areas respectively corresponding to the plurality of subpixel areas. 
     A pixel-defining layer 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 plurality of color filter areas (or the plurality of color conversion areas) may include a first area emitting a first color light, a second area emitting a second color light, and/or a third area emitting a 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 plurality of color filter areas (or the plurality of color conversion areas) may include quantum dots. In one embodiment, 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 (e.g., may exclude) a quantum dot. The quantum dot is the same as described in the present specification. The first area, the second area, and/or the third area may each further include a scatterer. 
     In an embodiment, the light-emitting device may be to emit a first light, the first area may be to absorb the first light to emit a first first-color light, the second area may be to absorb the first light to emit a second first-color light, and the third area may be to absorb the first light to emit a third first-color light. In this regard, the first first-color light, the second first-color light, and the third first-color light may have different maximum emission wavelengths. In one embodiment, the first light may be blue light, the first first-color light may be red light, the second first-color light may be green light, and the third first-color light may be blue light. 
     The electronic apparatus may further include a thin-film transistor in addition to the light-emitting device as described above. The thin-film transistor may include a source electrode, a drain electrode, and an activation layer, wherein the source electrode or the drain electrode may be electrically connected to the first electrode or 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 crystalline silicon, amorphous silicon, organic semiconductor, oxide semiconductor, and/or the like. 
     The electronic apparatus may further include a sealing portion for sealing the light-emitting device. The sealing portion and/or the color conversion layer may be located 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 concurrently (e.g., simultaneously) preventing or reducing ambient air and/or 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 or an inorganic layer. When the sealing portion is a thin film encapsulation layer, the electronic apparatus may be flexible. 
     Various suitable functional layers may be additionally located on the sealing portion, in addition to the color filter and/or the color conversion layer, according to the utilize of the electronic apparatus. The functional layers may include a touch screen layer, a polarizing layer, and/or the like. The touch screen layer may be a pressure-sensitive touch screen layer, a capacitive touch screen layer, or an infrared touch screen layer. 
     The authentication apparatus may be, for example, a biometric authentication apparatus that authenticates an individual by utilizing 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 be applied to one or more suitable displays, light sources, lighting apparatuses, personal computers (for example, a mobile personal computer), mobile phones, digital cameras, electronic diaries (e.g., organizers), electronic dictionaries, electronic game machines, medical instruments (for example, electronic thermometers, sphygmomanometers, blood glucose meters, pulse measurement devices, pulse wave measurement devices, electrocardiogram (ECG) displays, ultrasonic diagnostic devices, and/or endoscope displays), fish finders, one or more suitable measuring instruments, meters (for example, meters for a vehicle, an aircraft, and/or a vessel), projectors, and/or the like. 
     Description of FIGS.  2  and  3   
       FIG.  2    is a cross-sectional view of an electronic apparatus according to an embodiment. 
     The electronic apparatus of  FIG.  2    includes a substrate  100 , a thin-film transistor (TFT), a light-emitting device, and an encapsulation portion  300  that seals the light-emitting device. 
     The substrate  100  may be a flexible substrate, a glass substrate, or a metal substrate. A buffer layer  210  may be formed on the substrate  100 . The buffer layer  210  may prevent or reduce penetration of impurities through the substrate  100  and may provide a flat surface on the substrate  100 . 
     A TFT may be located on the buffer layer  210 . The TFT 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 silicon and/or polysilicon, an organic semiconductor, and/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 may be electrically connected to a light-emitting device to drive the light-emitting device, and may be covered by a passivation layer  280 . The passivation layer  280  may include an inorganic insulating film, an organic insulating film, or a combination thereof. A light-emitting device may be provided on the passivation layer  280 . The light-emitting device may include a first electrode  110 , an interlayer  130 , and a second electrode  150 . 
     The first electrode  110  may be 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 polyacrylic organic film. In one or more embodiments, one or more 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 silicon nitride (SiNx), silicon oxide (SiOx), indium tin oxide, indium zinc oxide, or any combination thereof; an organic film including polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, polyethylene sulfonate, polyoxymethylene, polyarylate, hexamethyldisiloxane, an acrylic resin (for example, polymethyl methacrylate, polyacrylic acid, and/or the like), an epoxy-based resin (for example, aliphatic glycidyl ether (AGE), and/or the like), or a combination thereof; or a combination of the inorganic film and the organic film. 
       FIG.  3    is a cross-sectional view of an electronic apparatus according to another embodiment. 
     The electronic apparatus of  FIG.  3    is the same as the light-emitting apparatus of  FIG.  2   , except that a light-shielding pattern  500  and a functional region  400  are additionally located on the encapsulation portion  300 . The functional region  400  may be i) a color filter area, ii) a color conversion area, or iii) a combination of the color filter area and the color conversion area. In an embodiment, the light-emitting device included in the light-emitting apparatus of  FIG.  3    may be a tandem light-emitting device. 
     Manufacture Method 
     Respective layers included in the hole transport region, the emission layer, and respective layers included in the electron transport region may be formed in a certain region by utilizing 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, the emission layer, and layers constituting the electron transport region are formed by vacuum deposition, the deposition may be performed at a deposition temperature of about 100° C. to about 500° C., a vacuum degree of about 10 −8  torr to about 10 −3  torr, and a deposition speed of about 0.01 Å/sec to about 100 Å/sec, depending on a material to be included in a layer to be formed and the structure of the layer to be formed. 
     When layers constituting the hole transport region, the emission layer, and layers constituting the electron transport region are formed by spin coating, the spin coating may be performed at a coating speed of about 2,000 rpm to about 5,000 rpm and at a heat treatment temperature of about 80° C. to 200° C. by taking into account a material to be included in a layer to be formed and the structure of the layer to be formed. 
     Definition of Terms 
     The term “C 3 -C 60  carbocyclic group” as used herein refers to a cyclic group including only carbon atoms as ring-forming atoms 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 atoms, a heteroatom as a ring-forming atom. The C 3 -C 60  carbocyclic group and the C 1 -C 60  heterocyclic group may each be a monocyclic group consisting of one ring or a polycyclic group in which two or more rings are condensed with each other. In an embodiment, the C 1 -C 60  heterocyclic group has 3 to 61 ring-forming atoms. 
     The term “cyclic group” as used herein may include the C 3 -C 60  carbocyclic group and the C 1 -C 60  heterocyclic group. 
     The term “π electron-rich C 3 -C 60  cyclic group” as used herein refers to a cyclic group (e.g., a carbocyclic group or a heterocyclic 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. 
     In an embodiment, 
     the C 3 -C 60  carbocyclic group may be i) a group T1 or ii) a condensed cyclic group in which two or more groups T1 are condensed with each other (for example, the C 3 -C 60  carbocyclic group may be 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 T2, ii) a condensed cyclic group in which two or more groups T2 are condensed with each other, or iii) a condensed cyclic group in which at least one group T2 and at least one group T1 are condensed with each other (for example, the C 1 -C 60  heterocyclic group may be 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 benzisoxazole 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 T1, ii) a condensed cyclic group in which two or more groups T1 are condensed with each other, iii) a group T3, iv) a condensed cyclic group in which two or more groups T3 are condensed with each other, or v) a condensed cyclic group in which at least one group T3 and at least one group T1 are condensed with each other (for example, the π electron-rich C 3 -C 60  cyclic group may be the C 3 -C 60  carbocyclic group, a 1H-pyrrole group, a silole group, a borole group, a 2H-pyrrole group, a 3H-pyrrole group, a thiophene group, a furan group, an indole group, a benzoindole group, a naphthoindole group, an isoindole group, a benzoisoindole group, a naphthoisoindole group, a benzosilole group, a benzothiophene group, a benzofuran group, a carbazole group, a dibenzosilole group, a dibenzothiophene group, a dibenzofuran group, an indenocarbazole group, an indolocarbazole group, a benzofurocarbazole group, a benzothienocarbazole group, a benzosilolocarbazole group, a benzoindolocarbazole group, a benzocarbazole group, a benzonaphthofuran group, a benzonaphthothiophene group, a benzonaphthosilole group, a benzofurodibenzofuran group, a benzofurodibenzothiophene group, a benzothienodibenzothiophene group, etc.), 
     the π electron-deficient nitrogen-containing C 1 -C 60  cyclic group may be i) group T4, ii) a condensed cyclic group in which two or more group T4 are condensed with each other, iii) a condensed cyclic group in which at least one group T4 and at least one group T1 are condensed with each other, iv) a condensed cyclic group in which at least one group T4 and at least one group T3 are condensed with each other, or v) a condensed cyclic group in which at least one group T4, at least one group T1, and at least one group T3 are condensed with one another (for example, the π electron-deficient nitrogen-containing C 1 -C 60  cyclic group may be 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 benzisothiazole 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 T1 may be a cyclopropane group, a cyclobutane group, a cyclopentane group, a cyclohexane group, a cycloheptane group, a cyclooctane group, a cyclobutene group, a cyclopentene group, a cyclopentadiene group, a cyclohexene group, a cyclohexadiene group, a cycloheptene group, an adamantane group, a norbornane (or a bicyclo[2.2.1]heptane) group, a norbornene group, a bicyclo[1.1.1]pentane group, a bicyclo[2.1.1]hexane group, a bicyclo[2.2.2]octane group, or a benzene group, 
     the group T2 may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, a borole group, a 2H-pyrrole group, a 3H-pyrrole group, an imidazole group, a pyrazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, an azasilole group, an azaborole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a tetrazine group, a pyrrolidine group, an imidazolidine group, a dihydropyrrole group, a piperidine group, a tetrahydropyridine group, a dihydropyridine group, a hexahydropyrimidine group, a tetrahydropyrimidine group, a dihydropyrimidine group, a piperazine group, a tetrahydropyrazine group, a dihydropyrazine group, a tetrahydropyridazine group, or a dihydropyridazine group, 
     the group T3 may be a furan group, a thiophene group, a 1H-pyrrole group, a silole group, or a borole group, and 
     the group T4 may be a 2H-pyrrole group, a 3H-pyrrole group, an imidazole group, a pyrazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, an oxadiazole group, a thiazole group, an isothiazole group, a thiadiazole group, an azasilole group, an azaborole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, or a tetrazine group. 
     The term “cyclic group”, “C 3 -C 60  carbocyclic group”, “C 1 -C 60  heterocyclic group”, “π electron-rich C 3 -C 60  cyclic group”, or “π electron-deficient nitrogen-containing C 1 -C 60  cyclic group” as used herein each refers to a group condensed to any cyclic group, or a monovalent or multivalent 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, and/or the like, which may be easily understood by one of ordinary skill in the art according to the structure of a formula including the “benzene group.” 
     In an embodiment, non-limiting examples of the monovalent C 3 -C 60  carbocyclic group and the monovalent C 1 -C 6  heterocyclic group may include a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, and non-limiting examples of the divalent C 3 -C 60  carbocyclic group and the divalent C 1 -C 6  heterocyclic group may include a C 3 -C 10  cycloalkylene group, a C 1 -C 10  heterocycloalkylene group, a C 3 -C 10  cycloalkenylene group, a C 1 -C 10  heterocycloalkenylene group, a C 6 -C 60  arylene group, a C 1 -C 60  heteroarylene group, a divalent non-aromatic condensed polycyclic group, and a divalent non-aromatic condensed heteropolycyclic group. 
     The term “C 1 -C 60  alkyl group” as used herein refers to a linear or branched aliphatic hydrocarbon monovalent group that has one to sixty carbon atoms, and examples thereof may include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. The term “C 1 -C 60  alkylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 60  alkyl group. 
     The term “C 2 -C 60  alkenyl group” as used herein refers to a monovalent hydrocarbon group having at least one carbon-carbon double bond in the middle or at a terminal end (e.g., the terminus) of a C 2 -C 60  alkyl group, and examples thereof may include an ethenyl group, a propenyl group, and a butenyl group. The term “C 2 -C 60  alkenylene group” as used herein refers to a divalent group having the same structure as the C 2 -C 60  alkenyl group. 
     The term “C 2 -C 60  alkynyl group” as used herein refers to a monovalent hydrocarbon group having at least one carbon-carbon triple bond in the middle or at a terminal end (e.g., the terminus) of a C 2 -C 60  alkyl group, and examples thereof may 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 the same structure as the C 2 -C 60  alkynyl group. 
     The term “C 1 -C 60  alkoxy group” as used herein refers to a monovalent group represented by —OA 101  (wherein A 101  is the C 1 -C 60  alkyl group), and examples thereof may 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 may include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group (or a bicyclo[2.2.1]heptyl group), a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, and a bicyclo[2.2.2]octyl group. The term “C 3 -C 10  cycloalkylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkyl group. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent cyclic group that further includes, in addition to 1 to 10 carbon atoms, at least one heteroatom as a ring-forming atom, and examples thereof may include a 1,2,3,4-oxatriazolidinyl group, a tetrahydrofuranyl group, and a tetrahydrothiophenyl group. The term “C 1 -C 10  heterocycloalkylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkyl group. 
     The term “C 3 -C 10  cycloalkenyl group” as used herein refers to a monovalent cyclic group that has three to ten carbon atoms, at least one carbon-carbon double bond in the ring thereof, and no aromaticity, and examples thereof may include a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. The term “C 3 -C 10  cycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkenyl group. 
     The term “C 1 -C 10  heterocycloalkenyl group” as used herein refers to a monovalent cyclic group that has, in addition to 1 to 10 carbon atoms, at least one heteroatom as a ring-forming atom, and at least one carbon-carbon double bond in the cyclic structure thereof. Non-limiting examples of the C 1 -C 10  heterocycloalkenyl group may include a 4,5-dihydro-1,2,3,4-oxatriazolyl group, a 2,3-dihydrofuranyl group, and a 2,3-dihydrothiophenyl group. The term “C 1 -C 10  heterocycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkenyl group. 
     The term “C 6 -C 60  aryl group” as used herein refers to a monovalent group having a carbocyclic aromatic system 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. Non-limiting examples of the C 6 -C 60  aryl group may include a phenyl group, a pentalenyl group, a naphthyl group, an azulenyl group, an indacenyl group, an acenaphthyl group, a phenalenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a perylenyl group, a pentaphenyl group, a heptalenyl group, a naphthacenyl group, a picenyl group, a hexacenyl group, a pentacenyl group, a rubicenyl group, a coronenyl group, a fluorenyl 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 two or more rings may be condensed with each other. 
     The term “C 1 -C 60  heteroaryl group” as used herein refers to a monovalent group having a heterocyclic aromatic system that has, in addition to 1 to 60 carbon atoms, at least one heteroatom as a ring-forming atom. 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 1 to 60 carbon atoms, at least one heteroatom as a ring-forming atom. Non-limiting examples of the C 1 -C 60  heteroaryl group may include a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, a benzoquinolinyl group, an isoquinolinyl group, a benzoisoquinolinyl group, a quinoxalinyl group, a benzoquinoxalinyl group, a quinazolinyl group, a benzoquinazolinyl group, a cinnolinyl group, a phenanthrolinyl group, a phthalazinyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiofuranyl 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 two or more rings may be condensed with each other. 
     The term “monovalent non-aromatic condensed polycyclic group” as used herein refers to a monovalent group having two or more rings condensed to each other, only carbon atoms (for example, having 8 to 60 carbon atoms) as ring-forming atoms, and no aromaticity in its molecular structure when considered as a whole (e.g., the entire molecular structure is not aromatic). Non-limiting examples of the monovalent non-aromatic condensed polycyclic group may include an indenyl group, a fluorenyl group, a spiro-bifluorenyl group, a benzofluorenyl group, an indenophenanthrenyl group, an adamantyl group, and an indeno anthracenyl group. 
     The term “divalent non-aromatic condensed polycyclic group” as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed polycyclic group. 
     The term “monovalent non-aromatic condensed heteropolycyclic group” as used herein refers to a monovalent group (for example, having 1 to 60 carbon atoms) having two or more rings condensed to each other, at least one heteroatom other than carbon atoms, as a ring-forming atom, and no aromaticity in its molecular structure when considered as a whole (e.g., the entire molecular structure is not aromatic). Non-limiting examples of the monovalent non-aromatic condensed heteropolycyclic group may include a pyrrolyl group, a thiophenyl group, a furanyl group, an indolyl group, a benzoindolyl group, a naphtho indolyl group, an isoindolyl group, a benzoisoindolyl group, a naphthoisoindolyl group, a benzosilolyl group, a benzothiophenyl group, a benzofuranyl group, a carbazolyl group, a dibenzosilolyl group, a dibenzothiophenyl group, a dibenzofuranyl group, an azacarbazolyl group, an azafluorenyl group, an azadibenzosilolyl group, an azadibenzothiophenyl group, an azadibenzofuranyl group, a pyrazolyl group, an imidazolyl group, a triazolyl group, a tetrazolyl group, an oxazolyl group, an isoxazolyl group, a thiazolyl group, an isothiazolyl group, an oxadiazolyl group, a thiadiazolyl group, a benzopyrazolyl group, a benzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzoxadiazolyl group, a benzothiadiazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, an imidazotriazinyl group, an imidazopyrazinyl group, an imidazopyridazinyl group, an indenocarbazolyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a benzosilolocarbazolyl group, a benzoindolocarbazolyl group, a benzocarbazolyl group, a benzonaphthofuranyl group, a benzonaphthothiophenyl group, a benzonaphthosilolyl group, a benzofurodibenzofuranyl group, a benzofurodibenzothiophenyl group, an azaadamantyl group, and a benzothienodibenzothiophenyl group. The term “divalent non-aromatic condensed heteropolycyclic group” as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed heteropolycyclic group. 
     The term “C 6 -C 60  aryloxy group” as used herein refers to a monovalent group represented by —OA 102  (wherein A 102  is the C 6 -C 60  aryl group), and the term “C 6 -C 60  arylthio group” as used herein refers to a monovalent group represented by —SA 103  (wherein A 103  is the C 6 -C 60  aryl group). 
     The term “C 7 -C 60  aryl alkyl group” as used herein refers to a monovalent group represented by -A 104 A 105  (where A 104  is a C 1 -C 54  alkylene group, and A 105  is a C 6 -C 59  aryl group), and the term “C 2 -C 60  heteroaryl alkyl group” as used herein refers to a monovalent group represented by -A 106 A 107  (where A 106  is a C 1 -C 59  alkylene group, and A 107  is a C 1 -C 59  heteroaryl group). 
     R 10a  may be: 
     deuterium (-D), —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, or a nitro group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, or a C 1 -C 60  alkoxy group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  aryl alkyl group, a C 2 -C 60  heteroaryl alkyl group, —Si(Q 11 )(Q 12 )(Q 13 ), —N(Q 11 )(Q 12 ), —B(Q 11 )(Q 12 ), —C(═O)(Q 11 ), —S(═O) 2 (Q 11 ), —P(═O)(Q 11 )(Q 12 ), or any combination thereof; 
     a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, or a C 2 -C 60  heteroarylalkyl group, each unsubstituted or substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 60  carbocyclic group, a C 1 -C 60  heterocyclic group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 2 -C 60  heteroarylalkyl group, —Si(Q 21 )(Q 22 )(Q 23 ), —N(Q 21 )(Q 22 ), —B(Q 21 )(Q 22 ), —C(═O)(Q 21 ), —S(═O) 2 (Q 21 ), —P(═O)(Q 21 )(Q 22 ), or any combination thereof; or 
     —Si(Q 31 )(Q 32 )(Q 33 ), —N(Q 31 )(Q 32 ), —B(Q 31 )(Q 32 ), —C(═O)(Q 31 ), —S(═O) 2 (Q 31 ), or —P(═O)(Q 31 )(Q 32 ). 
     Q 1  to Q 3 , Q 11  to Q 13 , Q 21  to Q 23 , and Q 31  to Q 33  as used herein may each independently be: hydrogen; deuterium; —F; —CI; —Br; —I; a hydroxyl group; a cyano group; a nitro group; a C 1 -C 6  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 unsubstituted or substituted with deuterium, —F, a cyano group, a C 1 -C 60  alkyl group, a C 1 -C 6  alkoxy group, a phenyl group, a biphenyl group, or any combination thereof; a C 1 -C 60  heterocyclic group; a C 7 -C 60  aryl alkyl group; or a C 2 -C 60  heteroaryl alkyl group. 
     The term “hetero atom” as used herein refers to any atom other than a carbon atom. Non-limiting examples of the heteroatom may include O, S, N, P, Si, B, Ge, Se, or any combination thereof. 
     The term “third-row transition metal” as used herein includes hafnium (Hf), tantalum (Ta), tungsten(W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), or gold (Au). 
     The term “Ph” as used herein refers to a phenyl group, the term “Me” as used herein refers to a methyl group, the term “Et” as used herein refers to an ethyl group, the term “ter-Bu” or “Bu t ” as used herein refers to a tert-butyl group, and the term “OMe” as used herein refers to a methoxy group. 
     The term “biphenyl group” as used herein refers to “a phenyl group substituted with a phenyl group.” In other words, the “biphenyl group” is a substituted phenyl group having a C 6 -C 60  aryl group as a substituent. 
     The term “terphenyl group” as used herein refers to “a phenyl group substituted with a biphenyl group”. 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. 
     The maximum number of carbon atoms in this substituent definition section is an example only. In an embodiment, the maximum carbon number of 60 in the C 1 -C 60  alkyl group is an example, and the definition of the alkyl group equally applies to a C 1 -C 20  alkyl group. The same also applies to other cases. 
     * and *′ as used herein, unless defined otherwise, each refer to a binding site to a neighboring atom in a corresponding formula. 
     Hereinafter, compounds according to embodiments and light-emitting devices according to embodiments will be described in more detail with reference to the following synthesis examples and examples. The wording “B was utilized instead of A” used in describing Synthesis Examples refers to that an identical molar equivalent of B was utilized in place of A. 
     EXAMPLE 
     Comparative measurement of electrode absorption rate and sheet resistance 
     Comparative Example 1 
     A glass substrate was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically cleaned with isopropyl alcohol and pure water each for 10 minutes, and then cleaned by irradiation of ultraviolet rays and exposure to ozone for 30 minutes. Then, the glass substrate was loaded onto a vacuum deposition apparatus. 
     ET1 as an electron transport compound was vacuum-deposited on the substrate to form an electron transport layer having a thickness of 300 Å. 
     Yb was vacuum-deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å. 
     Subsequently, Ag and Mg were vacuum-deposited (e.g., co-deposited) on the electron injection layer at a volume ratio of 95%: 5% to form an electrode having a thickness of 100 Å. CPL was deposited on the electrode to form a capping layer having a thickness of 500 Å, thereby completing the manufacture of an evaluation structure. 
     Example 1 
     An evaluation structure was manufactured in substantially the same manner as in Comparative Example 1, except that Ag (electrical conductivity: 6.3×10 7  S/m) and Mg (work function: −3.70 eV) were vacuum-deposited (e.g., co-deposited) on the electron injection layer at a volume ratio of 95%:5% to form a first layer of the electrode, which has a thickness of 10 Å, and then Ag was vacuum-deposited on the first layer to form a second layer of the electrode, which has a thickness of 50 Å. 
     Example 2 
     An evaluation structure was manufactured in substantially the same manner as in Comparative Example 1, except that Ag and Mg were vacuum-deposited (e.g., co-deposited) on the electron injection layer at a volume ratio of 95%:5% to form a first layer of the electrode, which has a thickness of 10 Å, and then Ag was vacuum-deposited on the first layer to form a second layer of the electrode, which has a thickness of 70 Å. 
     Example 3 
     An evaluation structure was manufactured in substantially the same manner as in Comparative Example 1, except that Ag and Mg were vacuum-deposited (e.g., co-deposited) on the electron injection layer at a volume ratio of 95%:5% to form a first layer of the electrode, which has a thickness of 10 Å, and then Ag was vacuum-deposited on the first layer to form a second layer of the electrode, which has a thickness of 90 Å. 
     Light of 450 nm, 540 nm, and 640 nm were irradiated to each of the evaluation structures of Comparative Example 1 and Examples 1 to 3, and transmittance, reflectance, and absorption rate were measured. The transmittance was measured utilizing Lambda 950 UV/Vis spectrometer of Perkin-Elmer Company. 
     Results are shown in Table 1. 
     
       
         
         
             
             
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Comparative Example 1 
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Transmission 
                 450 nm 
                 63.3 
                 70.7[7.4%]  
                 69.1[5.8%]  
                 65.8[2.5%]  
               
               
                   
                 540 nm 
                 77.5 
                 84.2[6.7%]  
                 83.5[6.0%]  
                 80.7[3.2%]  
               
               
                   
                 640 nm 
                 77.2 
                 86.9[9.7%]  
                 84.2[7.0%]  
                 78.9[1.7%]  
               
               
                 Reflection 
                 450 nm 
                 22.9 
                 19.5[−3.4%] 
                 21.4[−1.5%] 
                 23.1[0.2%]  
               
               
                   
                 540 nm 
                 10.0 
                  8.1[−1.9%] 
                  9.0[−1.0%] 
                 10.5[0.5%]  
               
               
                   
                 640 nm 
                 9.4 
                  5.1[−4.3%] 
                  7.8[−1.6%] 
                 12.3[2.9%]  
               
               
                 Absorption 
                 450 nm 
                 13.8 
                  9.8[−4.0%] 
                  9.4[−4.4%] 
                 11.1[−2.7%] 
               
               
                   
                 540 nm 
                 12.5 
                  7.7[−4.8%] 
                  7.5[−5.0%] 
                  8.8[−3.7%] 
               
               
                   
                 640 nm 
                 13.4 
                  8.1[−5.3%] 
                  8.0[−5.4%] 
                  8.8[−4.6%] 
               
               
                   
               
            
           
         
       
     
     In Table 1, a value in a square bracket refers to a value indicting a relative increase (positive value) or decrease (negative value) with respect to Comparative Example 1. 
     Referring to Table 1, in each of the structures of Examples 1 to 3, the absorption rate was lower than that of Comparative Example 1. 
     Comparative Example 2 
     An evaluation structure was manufactured in substantially the same manner as in Comparative Example 1, except that Compound nCGL_1 and Yb were vacuum-deposited (e.g., co-deposited) on the electron transport layer at a volume ratio of 90:10 to form an electron injection layer having a thickness of 10 Å. 
     Example 4 
     An evaluation structure was manufactured in substantially the same manner as in Example 2, except that Compound nCGL_1 and Yb were vacuum-deposited (e.g., co-deposited) on the electron transport layer at a volume ratio of 90:10 to form an electron injection layer having a thickness of 10 Å. 
     Example 5 
     An evaluation structure was manufactured in substantially the same manner as in Example 3, except that Compound nCGL_1 and Yb were vacuum-deposited (e.g., co-deposited) on the electron transport layer at a volume ratio of 90:10 to form an electron injection layer having a thickness of 10 Å. 
     
       
         
         
             
             
         
       
     
     With respect to evaluation structures of Comparative Examples 1 and 2 and Examples 2 to 5, a value of sheet resistance (Ω/□) of each electrode was measured at room temperature, and then heat treatment was performed for 9 hours at 80° C. and a value of sheet resistance (Ω/□) of each heat-treated electrode was measured. For the sheet resistance, a 4-point probe-based sheet resistance measuring instrument was utilized. 
     Measured values are shown in  FIG.  4   . 
     Referring to  FIG.  4   , in all cases, it may be confirmed that the electrode sheet resistance values of evaluation structures of Example 2 to 3 are lower than those of Comparative Example 1, and the electrode sheet resistance values of evaluation structures of Example 4 to 5 are lower than those of Comparative Example 2. 
     Manufacture of Light-Emitting Device 
     Comparative Example 3 
     A glass substrate with a 15 Ω/cm 2  (800 Å) ITO/Ag/ITO anode formed thereon (a product of Corning Inc.) was cut to a size of 50 mm×50 mm×0.7 mm, sonicated with isopropyl alcohol and pure water each for 5 minutes, and then cleaned by irradiation of ultraviolet rays and exposure of ozone thereto for 15 minutes. The resultant glass substrate was loaded onto a vacuum deposition apparatus. 
     NBP and F4-TCNQ were deposited on the ITO/Ag/ITO anode of the glass substrate at a weight ratio of 1:1 to form a hole injection layer having a thickness of 50 Å, NPB was deposited on the hole injection layer to form a first hole transport layer having a thickness of 300 Å, TCTA was deposited on the first hole transport layer to form a second hole transport layer having a thickness of 300 Å, BH3 and Compound 100 were co-deposited on the second hole transport layer at a weight ratio of 97:3 to form a first emission layer (blue) having a thickness of 200 Å, T2T was deposited on the first emission layer to form a second electron transport layer having a thickness of 100 Å, and TPM-TAZ and LiQ were co-deposited thereon at a weight ratio of 1:1 to form a first electron transport layer having a thickness of 100 Å. 
     Subsequently, nCGL_1 and Li were co-deposited thereon at a weight ratio of 99:1 to form an n-type or kind charge generation layer having a thickness of 150 Å, and NBP and F4-TCNQ were deposited (e.g., co-deposited) on the n-type or kind charge generation layer at a weight ratio of 1:1 to form a p-type or kind charge generation layer having a thickness of 50 Å. 
     NPB was deposited on the p-type or kind charge generation layer to form a first hole transport layer having a thickness of 300 Å, TCTA was deposited on the first hole transport layer to form a second hole transport layer having a thickness of 300 Å, BH3 and Compound 100 were co-deposited on the second hole transport layer at a weight ratio of 97:3 to form a second emission layer (blue) having a thickness of 200 Å, T2T was deposited on the second emission layer to form a second electron transport layer having a thickness of 100 Å, and subsequently, TPM-TAZ and LiQ were co-deposited thereon at a weight ratio of 1:1 to form a first electron transport layer having a thickness of 100 Å. 
     Subsequently, nCGL_1 and Li were co-deposited thereon at a weight ratio of 99:1 to form an n-type or kind charge generation layer having a thickness of 150 Å, and NBP and F4-TCNQ were deposited (e.g., co-deposited) on the n-type or kind charge generation layer at a weight ratio of 1:1 to form a p-type or kind charge generation layer having a thickness of 50 Å. 
     Subsequently, NPB was deposited thereon to form a first hole transport layer having a thickness of 300 Å, TCTA was deposited on the first hole transport layer to form a second hole transport layer having a thickness of 300 Å, BH3 and Compound 100 were co-deposited on the second hole transport layer at a weight ratio of 97:3 to form a third emission layer (blue) having a thickness of 200 Å, T2T was deposited on the third emission layer to form a second electron transport layer having a thickness of 100 Å, and subsequently, TPM-TAZ and LiQ were co-deposited thereon at a weight ratio of 1:1 to form a first electron transport layer having a thickness of 100 Å. 
     Subsequently, Yb was deposited thereon to form an electron injection layer having a thickness of 10 Å, and then Ag and Mg were co-deposited thereon at a volume ratio of 90:10 to form a cathode having a thickness of 100 Å. CPL was deposited on the cathode to form a capping layer having a thickness of 500 Å, thereby completing the manufacture of a tandem light-emitting device. 
     Comparative Example 4 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 10:90 to form a cathode having a thickness of 100 Å. 
     Comparative Example 5 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 10:90 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 50 Å. 
     Comparative Example 6 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 10:90 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 70 Å. 
     Example 6 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 50 Å. 
     Example 7 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 70 Å. 
     Example 8 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 90 Å. 
     Example 9 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 110 Å. 
     Example 10 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 120 Å. 
     Example 11 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 20 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 110 Å. 
     Example 12 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 30 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 100 Å. 
     Comparative Example 7 
     A tandem light-emitting device was manufactured in substantially the same manner as in Comparative Example 3, except that, in forming a cathode, Ag and Mg were co-deposited on the electron injection layer at a volume ratio of 90:10 to form a first layer of the cathode, which has a thickness of 10 Å, and Ag was deposited thereon to form a second layer of the cathode, which has a thickness of 140 Å. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     To evaluate the characteristics of the light-emitting devices manufactured according to each of Comparative Examples 3 to 7 and Examples 6 to 12, the driving voltage, efficiency, and lifespan at a current density of 10 mA/cm 2  were measured, and results are shown in Table 2. 
     The driving voltage and the current density of the light-emitting devices were measured utilizing a source meter (2400 series, Keithley Instruments Inc.), and the efficiency of the light-emitting devices was measured utilizing a measurement system (C9920-2-12 of Hamamatsu Photonics Inc.), 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Cathode[volume 
                 Driving voltage 
                 Efficiency 
                   
               
               
                   
                 ratio](thickness) 
                 (V) 
                 (Cd/A) 
                 Lifespan (T97, Hr) 
               
               
                   
               
             
            
               
                 Comparative 
                 AgMg[90:10](100 Å) 
                 14.8 
                 60.3 
                 280 
               
               
                 Example 3 
                   
                   
                   
                   
               
               
                 Comparative 
                 AgMg[10:90](100 Å) 
                 15.4 
                 51.0 
                 149 
               
               
                 Example 4 
                   
                   
                   
                   
               
               
                 Comparative 
                 AgMg[10:90](10 Å)/Ag(50 Å) 
                 15.3 
                 52.3 
                 150 
               
               
                 Example 5 
                   
                   
                   
                   
               
               
                 Comparative 
                 AgMg[10:90](10 Å)/Ag(70 Å) 
                 15.3 
                 52.0 
                 150 
               
               
                 Example 6 
                   
                   
                   
                   
               
               
                 Example 6 
                 AgMg[90:10](10 Å)/Ag(50 Å) 
                 14.7 
                 62.2 
                 280 
               
               
                 Example 7 
                 AgMg[90:10](10 Å)/Ag(70 Å) 
                 14.7 
                 62.0 
                 280 
               
               
                 Example 8 
                 AgMg[90:10](10 Å)/Ag(90 Å) 
                 14.8 
                 61.1 
                 280 
               
               
                 Example 9 
                 AgMg[90:10](10 Å)/Ag(110 Å) 
                 14.8 
                 60.3 
                 280 
               
               
                 Example 10 
                 AgMg[90:10](10 Å)/Ag(120 Å) 
                 14.8 
                 60.5 
                 280 
               
               
                 Example 11 
                 AgMg[90:10](20 Å)/Ag(110 Å) 
                 14.7 
                 60.3 
                 280 
               
               
                 Example 12 
                 AgMg[90:10](30 Å)/Ag(100 Å) 
                 14.7 
                 60.0 
                 280 
               
               
                 Comparative 
                 AgMg[90:10](10 Å)/Ag(140 Å) 
                 14.7 
                 57.6 
                 250 
               
               
                 Example 7 
               
               
                   
               
            
           
         
       
     
     In Table 2, Comparative Example 3 shows a result in the case of a cathode having a single layer structure of AgMg, and Comparative Examples 4 to 6 each show results in which an amount of Mg as a first metal in the cathode is greater than an amount of Ag as a second metal. Comparative Example 7 shows a result in which a total thickness of the cathode is greater than 130 Å. 
     From Table 2, it may be confirmed that all of the light-emitting devices of Examples 6 to 12 show excellent or suitable results in terms of efficiency, compared to the light-emitting devices of Comparative Examples 3 to 7. 
     These results are consistent with Table 1 and  FIG.  4   , which are results of the absorption rate and sheet resistance of the cathode. 
     A light-emitting device according to an embodiment includes an electrode having a low sheet resistance and a low absorption rate, and thus, has improved efficiency compared to that of the related art. 
     As used herein, the terms “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Also, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of “1.0 to 10.0” is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. 
     The display device and/or any other relevant devices or components according to embodiments of the present disclosure described herein may be implemented utilizing any suitable hardware, firmware (e.g. an application-specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the one or more suitable components of the device may be formed on one integrated circuit (IC) chip or on separate IC chips. Further, the one or more suitable components of the device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on one substrate. Further, the one or more suitable components of the device may be a process or thread, running on one or more processors, in one or more computing devices, executing computer program instructions and interacting with other system components for performing the one or more suitable functionalities described herein. The computer program instructions are stored in a memory which may be implemented in a computing device utilizing a standard memory device, such as, for example, a random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media such as, for example, a CD-ROM, flash drive, and/and/or the like. Also, a person of skill in the art should recognize that the functionality of one or more suitable computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of the embodiments of the present disclosure. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the drawings, it will be understood by those of ordinary skill in the art that one or more suitable changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims and equivalents thereof.