Light emitting element, light emitting device, and display device

A light-emitting element, comprising:

• a first electrode that is an anode;
• a second electrode that is a cathode;
• a light-emitting layer provided between the first electrode and the second electrode;
• a hole injection layer provided between the first electrode and the light-emitting layer;
• and
• a hole transport layer provided between the hole injection layer and the light-emitting layer,
• wherein an insulator layer is provided between the hole injection layer and the hole transport layer, the insulator layer being in contact with the hole injection layer and the hole transport layer,
• each of the hole injection layer, the insulator layer, and the hole transport layer comprises a compound independently including one or more types of a cation and one or more types of an anion,
• the anion includes a group 15 or a group 16 element of the periodic table,
• an average oxidation number of cations in the insulator layer is greater than an average oxidation number of cations in the hole transport layer and less than an average oxidation number of cations in the hole injection layer,
• an entirety of a surface of the insulator layer disposed between the hole injection layer and the hole transport layer is in direct contact with an entirety of a surface of the hole injection layer, and
• an entirety of another surface of the insulator layer disposed between the hole injection layer and the hole transport layer is in direct contact with an entirety of a surface of the hole transport layer.