Asymmetric aggregation-induced emission materials with double stable configurations toward promoted performance in non-doped organic light-emitting diodes

Three novel aggregation induced emission (AIE) active molecules TriPE-PA, TriPE-α-NA and TriPE-β-NA were designed and successfully synthesized through a simple synthetic route. The position 9 of chromophore anthracene was introduced with the phenyl, 1-naphthyl and 2-naphthyl group, respectively, and afterwards the triphenylethylene was embedded as an AIE active group at position 10, thus generating two kinds of stable asymmetric configurations in the latter two compounds. These materials display sky-blue emission and typical AIE characteristics, among which TriPE-PA presents the best AIE phenomenon with an αAIE value (ΦF(Film)/ΦF(THF)) of 63. Subsequent studies show that they exhibit very similar photophysical and electrochemical properties. However, it was observed that the TriPE-α-NA and TriPE-β-NA performances were much superior to TriPE-PA when they all functioned as the non-doped emitting layers in OLEDs, among which TriPE-β-NA presented an over six times higher EQE value in comparison to TriPE-PA. This probably resulted from the support of double stable asymmetric configurations in TriPE-α-NA and TriPE-β-NA, which gives them a better membrane morphology and thermodynamic stability. The theories of energy traps at grain boundaries were employed to explain such a causal relationship. Such results reemphasize a neglected strategy which may be helpful for the design of new AIE materials with high stability of efficiency.