Evolution of emission manners of organic light-emitting diodes: From emission of singlet exciton to emission of doublet exciton

The emission manners of organic light-emitting diodes (OLEDs) have evolved from emission of singlet exciton, then emission of triplet exciton, then emission of singlet exciton converted from triplet exciton, finally to emission of doublet exciton during the three-decades development.86