Light-Emitting Element, Light-Emitting Device, and Electronic Device

A light-emitting element comprising:

• an anode;
• a cathode;
• a first light-emitting layer between the anode and the cathode;
• and
• a second light-emitting layer between the anode and the first light-emitting layer, the second light-emitting layer being in contact with the first light-emitting layer,
• wherein the first light-emitting layer includes a host material, a hole-transporting material, and a light-emitting material, and
• wherein the second light-emitting layer includes the host material, the hole-transporting material at lower concentration than the first light-emitting layer, and the light-emitting material.

A light-emitting element comprising:

• an anode;
• a cathode;
• a first light-emitting layer between the anode and the cathode;
• and
• a second light-emitting layer between the anode and the first light-emitting layer,
• wherein the first light-emitting layer includes a host material, a hole-transporting material, and a light-emitting material, and
• wherein the second light-emitting layer includes the host material, the hole-transporting material at lower concentration than the first light-emitting layer, and the light-emitting material.