Effect of hole mobilities through the emissive layer on space charge limited currents of phosphorescent organic light-emitting diodes
In this letter, we used space charge limited current measurements to evaluate the hole mobilities of candidate host materials with or without doped phosphorescent guests through a study of hole only devices. We found different impacts to hole mobility in each material when the dopant concentration changes. We postulated that the guest/host energy level matching in the light emissive layer plays an important role in the performance of organic light emitting devices. A number of white organic light emitting devices were designed to prove the supposition. Using guest/host energy level matching a device was fabricated which demonstrated higher efficiency, lower efficiency roll-off and lower driving voltage compared to a non-level-matched device.
hole mobilities space charge limited currents phosphorescent organic light-emitting diodes