Achiral Dichroic Dyes-mediated Circularly Polarized Emission Regulated by Orientational Order Parameter through...

It is noteworthy that cholesteric liquid crystal (CLC) platforms have been witnessed in high-performance circularly polarized luminescence (CPL) behaviors through the highly organized chiral co-assembled arrangement of achiral dyes. However, most CPL-active design strategies are closely relative to the helix co-assembly structure of CLC rather than achiral dyes. Herein, we developed an intriguing regulation strategy for CPL-active CLC materials. They were regulated using the orientational order parameter (S_F ) of achiral dichroic dyes as an incisive probe for the order arrangement degree of achiral dyes in CLC media. The I-shaped phenothiazine derivative PHECN dye (S_F =0.30) emitted a strong CPL signal (|g_lum |=0.47). In contrast, the T-shaped derivative (PHEBen) dye (S_F =0.09) showed a weak circular polarization level (|g_lum |=0.07) at similar CLC textures. Most interestingly, this kind of dichroic PHECN dye with a higher S_F could greatly improve the contrast ratio of CPL (Δg_lum =0.47) and emission intensity (ΔFL=46.0 %) at direct-current electric field compared with the T-shaped PHEBen (Δg_lum =0.07 and ΔFL=1.0 %) in CLC. This work demonstrates that an induced CPL emission can be mediated using achiral dichroic dye, which will open a new avenue for developing excellent CPL-active display materials.