Red Fluorenes as the efficient host emitter for non-doped red organic light-emitting diodes

Abstract

Crystallinic red fluorophores based on donor-acceptor substituted spirofluorene, i.e., PhSPDCV show strong fluorescence in solution (phi(f) similar to 70%) as well as in solid state (phi(f) > 30%). Non-doped red OLEDs fabricated with PhSPDCV exhibit Authentic red (CIE, x = 0.65, y = 0.35) electroluminescence with brightness over 12,000 cd m(-2) (or > 600 cd m(-2) at 20 mA cm(-2)) and remarkable external quantum efficiency as high as 3.6%. On the other hand, the bis-substituted derivatives of spirofluorene BisPhSPDCV show relatively weak fluorescence both in solution (phi(f) < 20%) and in solid state (phi(f) < 10%). Although saturated red electroluminescence (CIE, x = 0.65, y = 0.35) is observed, non-doped red OLED containing BisPhSPDCV exhibit much worse performance compared with that of PhSPDCV OLEDs.