Highly Efficient Blue/Deep‐blue Circularly Polarized Electroluminescence with Small Efficiency Roll‐Offs

Abstract

AbstractDeveloping efficient blue/deep‐blue circularly polarized organic light‐emitting diodes (CP‐OLEDs) with small efficiency roll‐off remains a great challenge for wide color gamut and high contrast 3D displays. Here, two pairs of chiral stable enantiomers, (R/S)‐PPI‐OBN‐CN and (R/S)‐PyI‐OBN‐CN, composed of imidazole derivatives phenanthroimidazole (PPI) and pyrenoimidazole (PyI) donors, and chiral group of (R/S)‐octahydro‐binaphthol (OBN‐CN) acceptor are designed. These new blue/deep‐blue molecular architectures exhibit excellent thermal and electrochemical stabilities, hybrid local and charge transfer (HLCT) excited state, and clear CPL characteristics with dissymmetry factors (|gPL|) of 1.57 × 10−3/2.49 × 10−3 in the neat films. Moreover, the CP‐OLEDs based on (R/S)‐PPI‐OBN‐CN and (R/S)‐PyI‐OBN‐CN exhibit the deep‐blue/pure‐blue emission with the CIE coordinates of (0.15, 0.08) and (0.15, 0.14), the maximum external quantum efficiencies (EQEs) of 7.25% and 8.11% and very small efficiency roll‐offs of 17.6% and 1.8% at the luminescence of 1000 cd m−2, respectively. Even when the brightness is increased to 10000 cd m−2, (R/S)‐PyI‐OBN‐CN‐based device could still maintain as high as 6.68%. Obvious circularly polarized electroluminescence (CPEL) activities with the EL dissymmetry factors (gEL) of +1.54 × 10−3/−1.63 × 10−3 and +1.95 × 10−3/−1.72 × 10−3 are also recorded. These are the first highly efficient blue/deep‐blue CP‐OLEDs based on “hot exciton” enantiomers.