Excitonic-coupling enhancement in double π-helical dimers for highly efficient and robust circularly polarized...

Developing circularly polarized luminescence (CPL) materials with high brightness (BCPL) remains a central challenge, as it demands the synergistic optimization of both chiral response and luminescence efficiency. Through a comparative study of an N-annulated double π-helical perylene diimide dimer and its unmodified counterpart, this work demonstrates that strong excitonic coupling serves as a key strategy for achieving bright and robust CPL. The enhanced excitonic coupling promotes BCPL through a dual pathway: statically, it elevates the luminescence dissymmetry factor (glum) by markedly suppressing the electric transition dipole moment under H-aggregation while keeping the rotational strength essentially unchanged; dynamically, it suppresses excited-state symmetry-breaking charge transfer in polar dielectric environments, thereby sustaining a high photoluminescence quantum yield (ΦPL). Consequently, this work establishes the targeted enhancement of excitonic coupling as an effective design paradigm for developing high-brightness CPL materials with concurrently high glum and ΦPL.