Light-emitting element

1 . A light-emitting element comprising:

an anode;

a cathode facing the anode;

a light-emitting layer including quantum dots, the light-emitting layer being provided between the anode and the cathode;

a hole injection layer and a hole transport layer provided in this order from the anode side between the anode and the light-emitting layer; and

a monolayer film provided between the hole injection layer and the hole transport layer,

wherein the hole injection layer includes nanoparticles made from an inorganic material.

2 . The light-emitting element according to claim 1 ,

wherein the hole injection layer includes a compound including a metal element,

the compound includes at least one selected from Ni, Mg, Al, Zn, Fe, Sn, Cu, Cr, Ta, Mo, W, and Re, and

the compound includes at least one type of metal oxide.

3 . The light-emitting element according to claim 2 ,

wherein the metal element included in the hole injection layer includes Ni,

Ni included in the hole injection layer forms a compound, and

the compound includes at least one selected from oxygen, a hydroxyl group, carbon, and nitrogen and includes at least one selected from nickel (I) oxide, nickel (II) oxide, nickel (III) oxide, nickel hydroxide, nickel nitrate, and nickel carbonate.

4 . The light-emitting element according to claim 3 ,

wherein Ni included in the hole injection layer includes Ni having at least two types of valences.

5 . The light-emitting element according to claim 1 ,

wherein the nanoparticles included in the hole injection layer are substantially spherical bodies or spheroids.

6 . The light-emitting element according to claim 1 ,

wherein molecules included in the monolayer film have hole transport properties.

7 . The light-emitting element according to claim 1 ,

wherein molecules included in the monolayer film include a functional group at one end.

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

wherein molecules included in the monolayer film include a functional group, and

the molecules include at least one molecule selected from R—SH, RS—SR′, R—RSCN, R—SeH, R—TeH, RSe—SeR′, R—NC, R—NCO, R—SiH 3 , R—Si(CH 3 ) 2 H, R—Si(CH 3 ) 3 , R—COOH, dye-COOH, R—PO 3 H 2 , RO—PO 3 H 2 , R—SiX 2 [X=Cl, OCH 3 , OC 2 H 5 ], R—NH 2 , R—OH, [R—C(O)O] 2 , R—CH═CH 2 , R—C≡CH, R—MgBr 2 , R—Li, Ar—N 2 + X − , and R—BrR—CH═CH 2 , where R and R′ represent the functional group.

9 . The light-emitting element according to claim 1 ,

wherein the monolayer film includes at least one selected from MeO-2PACz, BA-CF 3 , 2PACz, and Me-4PACz.

10 . The light-emitting element according to claim 1 ,

wherein the monolayer film is provided only on a face side of the hole injection layer facing the light-emitting layer.

11 . The light-emitting element according to claim 1 ,

wherein in the monolayer film, a plurality of same molecules are arranged adjacent to one another.

12 . The light-emitting element according to claim 1 ,

wherein the hole transport layer includes a compound including a C-H bond at a part of the molecular structure, and

a thickness of the hole transport layer is from 1 nm to 50 nm.

13 . The light-emitting element according to claim 1 ,

wherein a thickness of the hole injection layer is from 1 nm to 50 nm.