Excitation-dependent circularly polarized luminescence triggered by selective excitation of achiral dichroic dyes in cholesterol liquid crystals

Excitation-dependent (ExD) circularly polarized luminescence (CPL) holds great potential for applications in anti-counterfeiting and information encryption due to its low cost, ease of operation, and reversibility. In this study, we propose a strategy to obtain ExD CPL by selective excitation of dyes with distinct dichroism and excitation wavelengths in a chiral liquid crystal (CLC) host. R/S-CLC-PG doped with the green-emitting dye EG (negative dichroism, S F = -0.31) and red-emitting PTZ (positive dichroism, S F = 0.15) can emit green CPL (-0.48/0.37 at 530 nm) at 365 nm excitation and inverted red CPL (0.53/-0.53 at 620 nm) at 420 nm excitation. In addition, R/S-CLC-PR doped with PTZ and red-emitting dye ER (negative dichroism, S F = -0.30) can emit red CPL (-0.16/0.13 at 620 nm) at 365 nm excitation and inverted red CPL (0.52/-0.55 at 620 nm) at 420 nm excitation. This work presents a versatile platform for developing ExD CPL materials with potential applications in anti-counterfeiting devices.