Abstract: An organic light emitting device, comprising an anode; a cathode; and an emissive layer between the anode and the cathode, wherein the emissive layer comprises a first material which is an organic semiconductor compound and a second material which is a different organic semiconductor compound that has a spin doublet ground state; and wherein a lowest spin singlet excitation energy of the first material and a lowest spin triplet excitation energy of the first material are greater than a lowest spin doublet excitation energy of the second material; a method of fabricating an organic light emitting device, comprising: forming an emissive layer between an anode and a cathode, wherein the emissive layer comprises a first material which is an organic semiconductor compound and a second material which is a different organic semiconductor compound that has a spin doublet ground state; and wherein a lowest spin singlet excitation energy of the first material and a lowest spin triplet excitation energy of the first mat