Tandem organic light emitting device with increased emission efficiency and display apparatus including the same

1 . A light emitting device comprising:

a first electrode;

a first light emitting stack disposed on the first electrode, the first light emitting stack comprising a first hole transport layer;

a charge generation layer disposed on the first light emitting stack, the charge generation layer comprising a p-type charge generation layer;

a second light emitting stack disposed on the charge generation layer, the second light emitting stack comprising a second hole transport layer; and

a second electrode disposed on the second light emitting stack, wherein,

a hole mobility of the p-type charge generation layer is lower than a hole mobility of the first hole transport layer and a hole mobility of the second hole transport layer, and

the p-type charge generation layer includes a highest occupied molecular orbital (HOMO) energy level that is equal to or lower than a HOMO energy level of the second hole transport layer.

2 . The light emitting device of claim 1 , wherein a material included in the hole transport layer is different from a material included in the charge generation layer.

3 . The light emitting device of claim 1 , wherein the hole mobility of the charge generation layer is in a range of about 50% to about 80% of the hole mobility of the hole transport layer.

4 . The light emitting device of claim 1 , wherein:

the charge generation layer comprises:

an n-type charge generation layer doped with an n-dopant; and

a p-type charge generation layer doped with a p-dopant, and

a hole mobility of the p-type charge generation layer is lower than the hole mobility of the hole transport layer.

5 . The light emitting device of claim 4 , wherein:

the p-type charge generation layer includes a thickness in a range of about 10 Å to about 100 Å; and

the hole transport layer includes a thickness in a range of about 100 Å to about 700 Å.

6 . The light emitting device of claim 1 , wherein the hole mobility of the charge generation layer is lower than a hole mobility of the second hole transport layer.

7 . The light emitting device of claim 1 , wherein the second hole transport layer is disposed directly on the charge generation layer.

8 . The light emitting device of claim 1 , wherein:

the first light emitting stack comprises a first light emitting layer disposed on the first hole transport layer; and

the second light emitting stack comprises a second light emitting layer disposed on the second hole transport layer.

9 . The light emitting device of claim 8 , wherein:

The first light emitting layer emits light having a first wavelength, and

the first wavelength is in a range of about 410 nm to about 480 nm.

10 . The light emitting device of claim 8 , wherein:

the second light emitting layer emits light having a first wavelength or a second wavelength,

the first wavelength is in a range of about 410 nm to about 480 nm, and

the second wavelength is in a range of about 500 nm to about 600 nm.

11 . The light emitting device of claim 1 , wherein:

the charge generation layer comprises:

an n-type charge generation layer disposed on the first light emitting stack; and

the p-type charge generation layer disposed on the n-type charge generation layer.

12 . The light emitting device of claim 11 , wherein a hole mobility of the p-type charge generation layer is lower than a hole mobility of the second hole transport layer.

13 . The light emitting device of claim 11 , wherein the second hole transport layer is disposed directly on the p-type charge generation layer.

14 . The light emitting device of claim 11 , wherein the HOMO energy level of each of the p-type charge generation layer and the second hole transport layer is in a range of about −5.3 eV to about −5.1 eV.

15 . A display apparatus comprising:

a base layer including:

a first pixel region emitting light having a first wavelength;

a second pixel region emitting light having a second wavelength different from the first wavelength; and

a third pixel region emitting light having a third wavelength different from the first wavelength and the second wavelength;

a light emitting device overlapping the first to third pixel regions and disposed on the base layer; and

a light control layer disposed on the light emitting device and including:

a first light control unit overlapping the first pixel region;

a second light control unit overlapping the second pixel region; and

a third light control unit overlapping the third pixel region,

wherein the light emitting device comprises:

a first electrode,

a first light emitting stack disposed on the first electrode, the first light emitting stack comprising a first hole transport layer,

a charge generation layer disposed on the first light emitting stack, the charge generation layer comprising a p-type charge generation layer,

a second light emitting stack disposed on the charge generation layer, the second light emitting stack comprising a second hole transport layer, and

a second electrode disposed on the second light emitting stack,

each of the first light emitting stack and the second light emitting stack includes a hole transport layer, and

a hole mobility of the p-type charge generation layer is lower than a hole mobility of the first hole transport layer and a hole mobility of the second hole transport layer, and

the p-type charge generation layer includes a highest occupied molecular orbital (HOMO) energy level that is equal to or lower than a HOMO energy level of the second hole transport layer.

16 . The display apparatus of claim 15 , wherein:

the second light control unit comprises a quantum dot that converts the light having the first wavelength into the light having the second wavelength; and

the third light control unit comprises a quantum dot that converts the light having the first wavelength or the light having the second wavelength into the light having the third wavelength.

17 . The display apparatus of claim 15 , further comprising a color filter layer disposed on the light control layer.

18 . The display apparatus of claim 15 , wherein:

the first electrode is a reflective electrode;

the second electrode is a transflective electrode or a transmissive electrode; and the light having the first wavelength is emitted in a direction from the first electrode to the second electrode.