Excitation‐Dependent Circularly Polarized Luminescence Inversion Driven by Dichroic Competition of Achiral Dyes in Cholesteric Liquid Crystals

The development of stimuli‐responsive chiral cholesteric liquid crystals (CLCs) materials holds significant potential for achieving three‐dimensional (3D) anti‐counterfeiting and multi‐level information encryption. However, constructing phototunable CLCs systems with easy fabrication and fast response remains a great challenge. Herein, we exploit an excitation‐dependent CLCs ( ExD‐CLCs ) material by establishing dynamically photoresponsive dichroic competition between two achiral dyes: a negative dichroic dye ( SP‐COOH ) and a positive dichroic dye (Nile Red, NR ) within a CLCs medium. The ExD‐CLCs exhibits a negative circularly polarized luminescence (CPL) signal ( g lum =−0.16) at 625 nm when excited at 365 nm. Remarkably, under excitation at 430 nm, the CPL signal is inverted, and the g lum value increases to +0.26. Notably, the helical superstructure and handedness of the ExD‐CLCs remain unchanged during this reversal process. The CPL signal reversal is driven by the dichroic competition between the SP‐COOH dimer, which displays strong negative dichroism in its open‐ring isomer form and silent negative dichroism in its closed‐ring isomer form, and the NR dye, which exhibits static positive dichroism. Leveraging these excitation‐dependent CPL properties, the quadruplex numerical anti‐counterfeiting using ExD‐CLCs is achieved.