Light-emitting element, display device, and method for manufacturing display device

A method for manufacturing a display device, comprising the steps of:

• forming a first electrode;
• forming a hole transport layer including a step of forming a hole-transport-material-mixed solution containing a plurality of molecules each including a hole-transportability skeleton and at least two thermosetting functional groups, and containing a plurality of hole-transportability molecules and a solvent onto the first electrode, followed by a heat treatment to join together the plurality of molecules including the hole-transportability skeleton and the at least two thermosetting functional groups, to constitute a 3D-mesh-structured high molecular material;
• forming a light-emitting layer onto the hole transport layer;
• forming a second electrode onto the light-emitting layer-, wherein
• a plurality of light-emitting elements including the first electrode, the hole transport layer, the light-emitting layer, and the second electrode are provided on a substrate,
• the plurality of light-emitting elements include a first light-emitting element, a second light-emitting element, and a third light-emitting element,
• the first light-emitting element includes a first light-emitting layer as the light-emitting layer,
• the second light-emitting element includes, as the light-emitting layer, a second light-emitting layer different in emission peak wavelength from the first light-emitting layer,
• the third light-emitting element includes, as the light-emitting layer, a third light-emitting layer different in emission peak wavelength from the first light-emitting layer and the second light-emitting layer, and
• the step of forming the light-emitting layer includes
• a step of forming a first resist layer onto at least the hole transport layer of the first light-emitting element, the hole transport layer of the second light-emitting element, and the hole transport layer of the third light-emitting element, followed by subjecting a first region of the first resist layer overlapping the hole transport layer of the first light-emitting element in a plan view to exposure and development to form a first opening in the first region of the first resist layer,
• a step of forming the first light-emitting layer onto the hole transport layer in the first opening, and the first resist layer, followed by removal of the first resist layer to form the first light-emitting layer of the first light-emitting element,
• a step of forming a second resist layer onto at least the first light-emitting layer of the first light-emitting element, the hole transport layer of the second light-emitting element, and the hole transport layer of the third light-emitting element, followed by subjecting a second region of the second resist layer overlapping the hole transport layer of the second light-emitting element in a plan view to exposure and development to form a second opening in the second region of the second resist layer,
• a step of forming the second light-emitting layer onto the hole transport layer in the second opening, and the second resist layer, followed by removal of the second resist layer to form the second light-emitting layer of the second light-emitting element,
• a step of forming a third resist layer onto at least the first light-emitting layer of the first light-emitting element, the second light-emitting layer of the second light-emitting element, and the hole transport layer of the third light-emitting element, followed by subjecting a third region of the third resist layer overlapping the hole transport layer of the third light-emitting element in a plan view to exposure and development to form a third opening in the third region of the third resist layer, and
• a step of forming the third light-emitting layer onto the hole transport layer in the third opening, and the third resist layer, followed by removal of the third resist layer to form the third light-emitting layer of the third light-emitting element.

A light-emitting element comprising:

• a first electrode;
• a hole transport layer formed on the first electrode;
• a light-emitting layer formed on the hole transport layer;
• and
• a second electrode formed on the light-emitting layer,
• wherein the hole transport layer contains a first hole transport material having a 3D mesh structure with molecules including a hole-transportability skeleton and at least two thermosetting functional groups being joined together to constitute a high molecule and contains a second hole transport material including a plurality of molecules having hole transportability,
• the at least two thermosetting functional groups are a phosphonate group (—PO3H2) and a hydroxy group (—OH), or a carboxyl group (—COOH) and a hydroxy group (—OH).