Organic light-emitting device comprising host, phosphorescent dopant and fluorescent dopant

An organic light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• and
• an emission layer disposed between the first electrode and the second electrode and comprising a delayed fluorescent host and a dopant,
• wherein the delayed fluorescent host comprises:
• an exciplex host which is a combination of a hole transporting host and an electron transporting host that combine together to form an exciplex;
• or
• a delayed fluorescent organic compound in the form of D-C-A (an electron donation group:
• D—a connecting group:
• C—an electron accepting group:
• A), in the form of D-C-A-C-D, or in the form of A-C-D-C-A, and
• the dopant comprises both a phosphorescent dopant and a fluorescent dopant
• wherein a triplet excited state energy level of the phosphorescent dopant is higher than a singlet excited state energy level and a triplet excited state energy level of the fluorescent dopant, and
• wherein a photoluminescence spectrum of the delayed fluorescent host overlaps an absorption spectrum of the fluorescent dopant, and a photoluminescence spectrum of the phosphorescent dopant overlaps an absorption spectrum of the fluorescent dopant.