Tunable CPL Inversion Driven by Transition Dipole Moment Engineering of Achiral Dichroic Pyrenes in Cholesteric Liquid Crystals

Decoupling circularly polarized luminescence (CPL) inversion from host supramolecular structural variations in cholesteric liquid crystals (CLCs) has long been a major challenge restricting the development of flexible optical devices. In this work, we tackle this challenge by implementing a transition dipole moment (TDM) engineering strategy. By tailoring the substitution patterns of achiral pyrene emitters to control TDM orientation along the molecular long axis, CPL inversion is realized in doped CLCs systems without affecting the supramolecular pitch or handedness. In R5011-doped SLC1717 systems, mono- and disubstituted pyrene derivatives (Py-1, Py-2, Py-4, and Py-5) exhibit positive fluorescence order parameters (SF), yielding positive CPL signals. In contrast, tetra-substituted dyes (Py-3 and Py-6) display negative SF values, resulting in inverted CPL signals. Notably, this inversion behavior persists across three commercial liquid crystal (LC) hosts (5CB, E7, and SLC1717).