Luminescence Chiral Exciplexes with Sky-Blue and Green Circularly Polarized -Thermally Activated Delayed Fluorecence.

Luminescent exciplexes based on a chiral electron donor molecule and achiral acceptor ones are reported as a new approach to design circularly polarized (CP) and thermally activated delayed fluorescence (TADF) emitters.  This innovative strategy results in rather high CP luminescence values with g lum up to 7 ´ 10 -3 , almost one order of magnitude higher in comparison to the CPL signal recorded for the chiral donor alone ( g lum ~ 8 ´ 10 -4 ). This increase occurs concomitantly to a CPL sign inversion, as a result of the strong charge-transfer emission character, as experimentally and theoretically rationalized using a covalent chiral Donor-Acceptor model. Interestingly, blue, green-yellow and red chiral luminescent exciplexes can be obtained by playing with the electron accepting character of the achiral unit while keeping the same chiral donor unit. These results bring new (inter)molecular guidelines to obtain simply and efficiently multi-color CP-TADF emitters.