Light-emitting device and electronic apparatus including same

1 . A light-emitting device comprising:

a first electrode;

a second electrode facing the first electrode; and

an emission layer between the first electrode and the second electrode,

wherein the emission layer comprises: i) a first emission layer and ii) a second emission layer between the first emission layer and the second electrode,

the first emission layer is in direct contact with the second emission layer,

the first emission layer comprises a first dopant, a first hole-transporting compound, and a first electron-transporting compound,

the second emission layer comprises a second dopant, a second hole-transporting compound, and a second electron-transporting compound,

the first dopant is identical to the second dopant,

the first electron-transporting compound is different from the second electron-transporting compound,

the first electron-transporting compound is a compound represented by Formula 7S and the second electron-transporting compound is a compound represented by Formula 7F,

wherein, in Formulae 7S and 7F,

Ar 71 to Ar 76 are each independently a benzene group or a carbazole group, each unsubstituted or substituted with deuterium, a C 1 -C 20 alkyl group, a phenyl group, a deuterated phenyl group, a (C 1 -C 20 alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a (C 1 -C 20 alkyl) biphenyl group, or any combination thereof,

a71 to a76 may each independently be 1, 2, or 3,

R 71 to R 76 may each independently be hydrogen, deuterium, a C 1 -C 20 _alkyl group, a phenyl group, a deuterated phenyl group, a (C 1 -C 20 alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a (C 1 -C 20 alkyl) biphenyl group, a carbazolyl group, a deuterated carbazolyl group, a (C 1 -C 20 alkyl) carbazolyl group, a di(C 1 -C 20 alkyl) carbazolyl group, or a (phenyl) carbazolyl group,

an electron mobility of the second electron-transporting compound is greater than an electron mobility of the first electron-transporting compound,

and

the electron mobility of the first electron-transporting compound and the electron mobility of the second electron-transporting compound are respectively evaluated by using a time versus current graph of a time of flight (TOF) device comprising the first electron-transporting compound or the second electron-transporting compound,

wherein Equation 3 is satisfied:

Con(ET2)>Con(ET1)  Equation 3

wherein, in Equation 3,

Con (ET2) indicates the parts by weight of the second electron-transporting compound, based on 100 parts by weight of the total weight of the second dopant, the second hole-transporting compound, and the second electron-transporting compound, and

Con (ET1) indicates the parts by weight of the first electron-transporting compound, based on 100 parts by weight of the total weight of the first dopant, the first hole-transporting compound, and the first electron-transporting compound.

2 . The light-emitting device of claim 1 , wherein the first emission layer comprises a mixture comprising the first dopant, the first hole-transporting compound, and the first electron-transporting compound, and

the second emission layer comprises a mixture comprising the second dopant, the second hole-transporting compound, and the second electron-transporting compound.

3 . The light-emitting device of claim 1 , wherein the first hole-transporting compound and the second hole-transporting compound are each a compound i) comprising at least one π electron-rich C 3 -C 60 cyclic group and ii) not including an electron-transporting group.

4 . The light-emitting device of claim 1 , wherein the electron mobility of the second electron-transporting compound is 110 percent (%) or greater of the electron mobility of the first electron-transporting compound.

5 . The light-emitting device of claim 1 , wherein the electron mobility of the second electron-transporting compound is in a range of about 110% to about 300% of the electron mobility of the first electron-transporting compound.

6 . The light-emitting device of claim 1 , wherein the electron mobility of the second electron-transporting compound is 2.0×10 −5 cm 2 /Vs or greater, and the electron mobility of the first electron-transporting compound is less than 2.8×10 −5 cm 2 /Vs.

7 . The light-emitting device of claim 1 , wherein Equation 1 is satisfied:

Con(HT1)>Con(ET1)  Equation 1

wherein, in Equation 1,

Con(HT1) indicates the parts by weight of the first hole-transporting compound, based on 100 parts by weight of the total weight of the first dopant, the first hole-transporting compound, and the first electron-transporting compound, and

Con (ET1) indicates the parts by weight of the first electron-transporting compound, based on 100 parts by weight of the total weight of the first dopant, the first hole-transporting compound, and the first electron-transporting compound.

8 . The light-emitting device of claim 7 , wherein a ratio of Con(HT1) to Con (ET1) is in a range of about 8:2 to about 5.2:4.8.

9 . The light-emitting device of claim 1 , wherein Equation 2 is satisfied:

Con(HT2)>Con(ET2)  Equation 2

wherein, in Equation 2,

Con(HT2) indicates the parts by weight of the second hole-transporting compound, based on 100 parts by weight of the total weight of the second dopant, the second hole-transporting compound, and the second electron-transporting compound, and

Con (ET2) indicates the parts by weight of the second electron-transporting compound, based on 100 parts by weight of the total weight of the second dopant, the second hole-transporting compound, and the second electron-transporting compound.

10 . The light-emitting device of claim 9 , wherein a ratio of Con(HT2) to Con (ET2) is in a range of about 8:2 to about 5.2:4.8.

11 . A light-emitting device comprising:

a first electrode;

a second electrode facing the first electrode; and

an emission layer between the first electrode and the second electrode,

wherein the emission layer comprises: i) a first emission layer and ii) a second emission layer between the first emission layer and the second electrode,

the first emission layer is in direct contact with the second emission layer,

the first emission layer comprises a first dopant, a first hole-transporting compound, and a first electron-transporting compound,

the second emission layer comprises a second dopant, a second hole-transporting compound, and a second electron-transporting compound,

the first dopant is identical to the second dopant,

the first electron-transporting compound is different from the second electron-transporting compound,

the first electron-transporting compound is a compound represented by Formula 7S and the second electron-transporting compound is a compound represented by Formula 7F,

wherein, in Formulae 7S and 7F,

Ar 71 to Ar 76 are each independently a benzene group or a carbazole group, each unsubstituted or substituted with deuterium, a C 1 -C 20 alkyl group, a phenyl group, a deuterated phenyl group, a (C 1 -C 20 alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a (C 1 -C 20 alkyl) biphenyl group, or any combination thereof,

a71 to a76 may each independently be 1, 2, or 3,

R 71 to R 76 may each independently be hydrogen, deuterium, a C 1 -C 20 alkyl group, a phenyl group, a deuterated phenyl group, a (C 1 -C 20 alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a (C 1 -C 20 alkyl) biphenyl group, a carbazolyl group, a deuterated carbazolyl group, a (C 1 -C 20 alkyl) carbazolyl group, a di(C 1 -C 20 alkyl) carbazolyl group, or a (phenyl) carbazolyl group,

an electron mobility of the second electron-transporting compound is greater than an electron mobility of the first electron-transporting compound, and

the electron mobility of the first electron-transporting compound and the electron mobility of the second electron-transporting compound are respectively evaluated by using a time versus current graph of a time of flight (TOF) device comprising the first electron-transporting compound or the second electron-transporting compound,

wherein Equation 4 is satisfied:

Con(ET2)<Con(ET1)  Equation 4

wherein, in Equation 4,

Con (ET2) indicates the parts by weight of the second electron-transporting compound, based on 100 parts by weight of the total weight of the second dopant, the second hole-transporting compound, and the second electron-transporting compound, and

Con (ET1) indicates the parts by weight of the first electron-transporting compound, based on 100 parts by weight of the total weight of the first dopant, the first hole-transporting compound, and the first electron-transporting compound.

12 . The light-emitting device of claim 1 , wherein a ratio of a thickness of the second emission layer to a thickness of the first emission layer is in a range of about 9:1 to about 1:9.

13 . The light-emitting device of claim 1 , wherein light which is emitted from the emission layer and passes through at least one of the first electrode and the second electrode to the outside of the device is not white light.

14 . The light-emitting device of claim 1 , wherein light which is emitted from the emission layer and passes through at least one of the first electrode and the second electrode to the outside of the device is green light having a maximum emission wavelength in a range of about 500 nanometers (nm) to about 580 nm.

15 . The light-emitting device of claim 1 , further comprising a hole transport region between the first electrode and the emission layer, wherein the hole transport region does not comprise a charge-generation layer and an emission layer.

16 . The light-emitting device of claim 1 , further comprising an electron transport region between the emission layer and the second electrode, wherein the electron transport region does not comprise a charge-generation layer and an emission layer.

17 . An electronic apparatus comprising the light-emitting device of claim 1 .

18 . A light-emitting device comprising:

a first electrode;

a second electrode facing the first electrode; and

an emission layer between the first electrode and the second electrode,

wherein the emission layer comprises: i) a first emission layer and ii) a second emission layer between the first emission layer and the second electrode,

the first emission layer is in direct contact with the second emission layer,

the first emission layer comprises a first dopant, a first hole-transporting compound, and a first electron-transporting compound,

the second emission layer comprises a second dopant, a second hole-transporting compound, and a second electron-transporting compound,

the first dopant is identical to the second dopant,

the first electron-transporting compound is different from the second electron-transporting compound,

the first electron-transporting compound is a compound represented by Formula 7S and the second electron-transporting compound is a compound represented by Formula 7F,

wherein, in Formulae 7S and 7F,

Ar 71 to Ar 76 are each independently a benzene group or a carbazole group, each unsubstituted or substituted with deuterium, a C 1 -C 20 alkyl group, a phenyl group, a deuterated phenyl group, a (C 1 -C 20 alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a (C 1 -C 20 alkyl) biphenyl group, or any combination thereof,

a71 to a76 may each independently be 1, 2, or 3,

R 71 to R 76 may each independently be hydrogen, deuterium, a C 1 -C 20 alkyl group, a phenyl group, a deuterated phenyl group, a (C 1 -C 20 alkyl)phenyl group, a biphenyl group, a deuterated biphenyl group, a (C 1 -C 20 alkyl) biphenyl group, a carbazolyl group, a deuterated carbazolyl group, a (C 1 -C 20 alkyl) carbazolyl group, a di(C 1 -C 20 alkyl) carbazolyl group, or a (phenyl) carbazolyl group,

an electron mobility of the second electron-transporting compound is greater than an electron mobility of the first electron-transporting compound, and

the electron mobility of the first electron-transporting compound and the electron mobility of the second electron-transporting compound are respectively evaluated by using a time versus current graph of a time of flight (TOF) device comprising the first electron-transporting compound or the second electron-transporting compound, and

the electron mobility is measured in the time of flight (TOF) device having a 1 um neat film of the respective compound between ITO and aluminum electrodes under a field strength of 2×10 5 V/cm.