Multifunctional electron-transporting indolizine derivatives for highly efficient blue fluorescence, orange phosphorescence host and two-color based white OLEDs

Abstract

In this work, derivatives of indolizine are first used as electron-transporting host materials for hybrid fluorescence/phosphorescence white organic light-emitting devices (F/P-WOLED). Of the indolizine derivatives, a blue fluorescent material BPPI (3-(4,4′-biphenyl)-2-diphenylindolizine) was found to have: (1) blue emission with high quantum yields, (2) good morphological and thermal stabilities, (3) electron-transporting properties, and (4) a sufficiently high triplet energy level to act as a host for red or yellow-orange phosphorescent dopants. The multifunctional BPPI enables adaptation of several simplified device configurations. For example, a non-doped blue fluorescent device exhibits good performance with an external quantum efficiency of 3.16% and Commission Internationale de l'Eclairage coordinates of (0.15, 0.07). A high-performance orange phosphorescent device was found to have a high current efficiency of 23.9 cd A⁻¹. Using BPPI, we also demonstrate a F/P-WOLED with a simplified structure, stable emissions and respectable performance (current and external quantum efficiencies of 17.8 cd A⁻¹ and 10.7%, respectively).