Bismuth Trifluoride as a low-temperature-evaporable insulating dopant for efficient and stable organic light-emitting diodes

Abstract

Bismuth Trifluoride (BiF3), with a high thermal stability and a low deposition temperature, has been studied as a novel dopant for the conventional hole transporting material of N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB). The efficiency and lifetime of organic light-emitting diodes (OLEDs) have been remarkably improved by using BiF3 doped NPB. For an optimized green device, a current efficiency of 21.6cd/A is reached, 40% higher than the control device without BiF3. And the lifetime is increased from 115h to 222h at room temperature. The enhanced efficiency and lifetime are attributed to the improved balance of holes and electrons in the emissive layer. Most importantly, the thermal stability at an elevated temperature of the OLEDs with BiF3 doped NPB is largely improved, showing an order of magnitude longer lifetime than the control device at 80°C.