论文部分内容阅读
Phosphorescent materials are of much interest as the emitter for organic light emitting diode (OLED) because of higher emission efficiency than organic fluorescent materials.In fact the internal and external quantum efficiencies are about four times higher than the fluorescent materials.The electronic transition probability from the spin singlet S1 state to the ground state S0 is much higher than the probability from the triplet T1 state.Therefore,the fluorescence from fluorescent materials gives higher luminance than the phosphorescence from phosphorescent material.The fluorescent materials,however,give very weak or no phosphorescence from the T1 state because of considerably weak spin-orbit coupling.It is usually difficult to find the T1 state for the fluorescent materials exactly.If we could enhance the phosphorescence from the fluorescent materials,these materials would be useful as new high efficient emitters for OLEDs since the fluorescent materials are more stable in the OLED operation than the phosphorescent ones.