Electroluminescence of intra-molecular exciplexes based on novel Lewis acid borane acceptors and a high triplet level donor

Abstract When a Lewis acid borane such as tris(pentafluorophenyl)borane (B(C6F5)3) or triphenylborane (B(C6H5)3) is used for an electron acceptor in a new supramolecular exciplex system, a high triplet electron donor 3,5-bis(3-(carbazol-9-yl)phenyl)pyridine (35DCzPPy) can form inter-molecular charge-transfer excited state complex with Lewis acid. Photoluminescence and X-ray photoelectron spectra showed that 35DCzPPy exhibited stronger interactions with B(C6F5)3 than with B(C6H5)3. By introducing Lewis base to the exciplex system, the fluorescence of 35CzPPy:B(C6F5)3 faded and the intrinsic emission of 35DCzPPy itself appeared in the blended solvent, from that the recovery of exciplex emission is achievable. In addition, organic light-emitting diodes were developed based on these 35DCzPPy:B(C6F5)3 exciplex emitters. These devices exhibited a maximum external quantum efficiency of ∼6.2 % at 1.97 mA/cm2. This result demonstrates that the electroluminescence of exciplex based on Lewis acid borane acceptors is promising.