Configurationally Stable Platinahelicene Enantiomers for Efficient Circularly Polarized Phosphorescent Organic Light-Emitting Diodes.

Abstract

Chiral materials with circularly polarized luminescence (CPL) are potentially applicable for 3D displays. In this study, by decorating the pyridinyl-helicene ligands with -CF3 and -F groups, the platinahelicene enantiomers featured superior configurational stability, as well as high sublimation yield (>90 %) and clear CPPL properties, with dissymmetry factors (|gPL |) of approximately 3.7×10-3 in solution and about 4.1×10-3 in doped film. The evaporated circularly polarized phosphorescent organic light-emitting diodes (CP-PhOLEDs) with two enantiomers as emitters exhibited symmetric CPEL signals with |gEL | of (1.1-1.6)×10-3 and decent device performances, achieving a maximum brightness of 11 590 cd m-2 , a maximum external quantum efficiency up to 18.81 %, which are the highest values among the reported devices based on chiral phosphorescent PtII complexes. To suppress the effect of reverse CPEL signal from the cathode reflection, the further implementation of semitransparent aluminum/silver cathode successfully boosts up the |gEL | by over three times to 5.1×10-3 .