New Host Materials Containing Carbazole and Naphthyl Moieties for Green Dopant in Phosphorescence Organic Light-Emitting Diodes(OLEDs)

摘要

Much effort on the development of new host materials has been devoted to increase the emission efficiency of organic light-emitting diodes(OLEDs).In particular,the use of phosphorescent molecules as guest emitters,which harvests both singlet and triplet excitons,leads to internal quantum efficiency(ETA_(INT))approaching 100%.Energy transfer from a host to a dopant in OLEDs can result in high external quantum efficiency(eta_(ext)).Therefore,the development of suitable hosts for blue,green and red phosphorescent emitters has been one of the major issues in the field of OLEDs.In general,host materials should have a higher triplet energy than that of the dopant molecules due to the energy transfer from the host to the guest while prohibits the energy transfer of triplet excitons from the guest to the host material.From the point of this consideration,carbazole derivatives are often use as host materials,because they have high triplet energies(2.9 eV or less).