Samsung Advanced Institute of Technology

Much effort has been dedicated to increase the operational lifetime of blue phosphorescent materials in organic light-emitting diodes (OLEDs), but the reported device lifetimes are still too short for the industrial applications. An attractive method for increasing the lifetime of a given emitter without making any chemical change is exploiting the kinetic isotope effect, where key C？H bonds are deuterated. A computer model identifies that the most vulnerable molecular site in an Ir-phenylimidazole dopant is the benzylic C？H bond and predicted that deuteration may lower the deactivation pathway involving C？H/D cleavage notably. Experiments show that the device lifetime (T₇₀) of a prototype phosphorescent OLED device can be doubled to 355 hours with a maximum external quantum efficiency of 25.1 ％ at 1000 cd m^？2. This is one of the best operational performances of blue phosphorescent OLEDs observed to date in a single stacked cell.