Metal-assisted delayed fluorescent materials as co-host materials for fluorescent OLEDS

A light emitting device comprising:

• a first electrode;
• a hole transporting layer in contact with the first electrode;
• a second electrode;
• an electron transporting layer in contact with the second electrode;
• and
• an emissive layer between the hole transporting layer and the electron transporting layer, wherein the emissive layer comprises a donor, an acceptor, and a host,
• wherein:
• the donor is a metal-assisted delayed fluorescent (MADF) emitter that demonstrates an emission spectrum consisting of dual emission characteristics from delayed fluorescence and phosphorescence,
• the acceptor is a fluorescent emitter,
• the delayed fluorescence emission energy of the donor is greater than the emission energy of the acceptor and the phosphorescence emission energy of the donor is greater than or less than the emission energy of the acceptor, such that an emission spectrum of the donor partially overlaps in wavelength with an absorption spectrum of the acceptor, and
• dipole coupling between the donor in an excited state and the acceptor in a ground state allows a transfer of energy from the donor to the acceptor.