Light-emitting device, light-emitting apparatus, electronic appliance, and lighting device

1 . A light-emitting device comprising:

a first electrode;

a second electrode;

an EL layer; and

an insulating layer,

wherein the EL layer is positioned between the first electrode and the second electrode,

wherein the EL layer comprises at least a hole-injection layer, a hole-transport layer, a light-emitting layer, an electron-transport layer, and an electron-injection layer,

wherein the electron-transport layer is positioned over the light-emitting layer,

wherein the electron-injection layer is positioned over the electron-transport layer and surrounds both side surfaces of the hole-injection layer, and

wherein the electron-injection layer comprises an alkali metal compound and a reducing agent.

2 . The light-emitting device according to claim 1 , wherein the electron-injection layer is a mixed film of the alkali metal compound and the reducing agent.

3 . The light-emitting device according to claim 2 , wherein a percentage of the reducing agent in the mixed film is more than or equal to 20 vol % and less than or equal to 80 vol %.

4 . The light-emitting device according to claim 1 , wherein the electron-injection layer is a stacked-layer film of a first layer comprising the alkali metal compound and a second layer comprising the reducing agent.

5 . The light-emitting device according to claim 4 , wherein the second layer is positioned between the first layer and the second electrode.

6 . The light-emitting device according to claim 1 , wherein the electron-injection layer has a thickness of more than or equal to 0.5 nm and less than or equal to 5 nm.

7 . The light-emitting device according to claim 1 , wherein the reducing agent is a material having a work function of higher than or equal to 2.5 eV and lower than 4.0 eV.

8 . The light-emitting device according to claim 1 ,

wherein the electron-injection layer is in contact with the insulating layer, and

wherein the insulating layer is positioned between an end portion of the light-emitting layer and a part of the electron-injection layer.

9 . A light-emitting device comprising:

a first electrode;

a second electrode; and

an EL layer,

wherein the EL layer is positioned between the first electrode and the second electrode,

wherein the EL layer comprises at least a hole-injection layer, a hole-transport layer, a light-emitting layer, an electron-transport layer, and an electron-injection layer,

wherein the electron-transport layer is positioned over the light-emitting layer,

wherein the electron-injection layer comprises a portion positioned over the electron-transport layer and a portion in contact with a side surface of the hole-injection layer, and

wherein the electron-injection layer comprises an alkali metal compound and a reducing agent.

10 . The light-emitting device according to claim 9 , wherein the electron-injection layer is a mixed film of the alkali metal compound and the reducing agent.

11 . The light-emitting device according to claim 10 , wherein a percentage of the reducing agent in the mixed film is more than or equal to 20 vol % and less than or equal to 80 vol %.

12 . The light-emitting device according to claim 9 , wherein the electron-injection layer is a stacked-layer film of a first layer comprising the alkali metal compound and a second layer comprising the reducing agent.

13 . The light-emitting device according to claim 12 , wherein the second layer is positioned between the first layer and the second electrode.

14 . The light-emitting device according to claim 9 , wherein the electron-injection layer has a thickness of more than or equal to 0.5 nm and less than or equal to 5 nm.

15 . The light-emitting device according to claim 9 , wherein the reducing agent is a material having a work function of higher than or equal to 2.5 eV and lower than 4.0 eV.

16 . A light-emitting apparatus comprising:

the light-emitting device according to claim 9 ; and

a transistor or a substrate.

17 . A light-emitting apparatus comprising:

a first light-emitting device; and

a second light-emitting device,

wherein the first light-emitting device comprises a first electrode, a second electrode, a first EL layer, and a first insulating layer,

wherein the first EL layer is positioned between the first electrode and the second electrode,

wherein the first EL layer comprises at least a first hole-injection layer, a first hole-transport layer, a first light-emitting layer, a first electron-transport layer, and an electron-injection layer,

wherein the first electron-transport layer is positioned over the first light-emitting layer,

wherein the electron-injection layer is positioned over the first electron-transport layer and surrounds both side surfaces of the first hole-injection layer,

wherein the second light-emitting device comprises a third electrode, the second electrode, a second EL layer, and a second insulating layer,

wherein the second EL layer is positioned between the third electrode and the second electrode,

wherein the second EL layer comprises at least a second hole-injection layer, a second hole-transport layer, a second light-emitting layer, a second electron-transport layer, and the electron-injection layer,

wherein the second electron-transport layer is positioned over the second light-emitting layer,

wherein the electron-injection layer is positioned over the second electron-transport layer and surrounds both side surfaces of the second hole-injection layer, and

wherein the electron-injection layer comprises an alkali metal compound and a reducing agent.

18 . An electronic appliance comprising:

the light-emitting apparatus according to claim 17 ; and

a sensor unit, an input unit, or a communication unit.

19 . A lighting device comprising:

the light-emitting apparatus according to claim 17 ; and

a housing.

20 . The light-emitting apparatus according to claim 17 ,

wherein the electron-injection layer is in contact with the first insulating layer,

wherein the first insulating layer is positioned between an end portion of the first light-emitting layer and a first part of the electron-injection layer,

wherein the electron-injection layer is in contact with the second insulating layer, and

wherein the second insulating layer is positioned between an end portion of the second light-emitting layer and a second part of the electron-injection layer.

21 . A light-emitting apparatus comprising:

a first light-emitting device; and

a second light-emitting device,

wherein the first light-emitting device comprises a first electrode, a second electrode, and a first EL layer,

wherein the first EL layer is positioned between the first electrode and the second electrode,

wherein the first EL layer comprises at least a first hole-injection layer, a first hole-transport layer, a first light-emitting layer, a first electron-transport layer, and an electron-injection layer,

wherein the first electron-transport layer is positioned over the first light-emitting layer,

wherein the electron-injection layer comprises a portion positioned over the first electron-transport layer and a portion in contact with a side surface of the first hole-injection layer,

wherein the second light-emitting device comprises a third electrode, the second electrode, and a second EL layer,

wherein the second EL layer is positioned between the third electrode and the second electrode,

wherein the second EL layer comprises at least a second hole-injection layer, a second hole-transport layer, a second light-emitting layer, a second electron-transport layer, and the electron-injection layer,

wherein the second electron-transport layer is positioned over the second light-emitting layer,

wherein the electron-injection layer comprises a portion positioned over the second electron-transport layer and a portion in contact with a side surface of the second hole-injection layer, and

wherein the electron-injection layer comprises an alkali metal compound and a reducing agent.

22 . An electronic appliance comprising:

the light-emitting apparatus according to claim 21 ; and

a sensor unit, an input unit, or a communication unit.