Thermally Invertible Full-Color Circularly Polarized Luminescence with High Dissymmetry Factors and High Quantum...

Deliberately targeted emission wavelengths, high quantum yields (QYs), and high luminescence dissymmetry factors (g_lum) are essential for chiral materials exhibiting circularly polarized luminescence (CPL). The addition of achiral luminophores to chiral nematic liquid crystals (N*-LCs) is a promising way to generate CPLs. We aimed to generate red-green-blue (RGB)- and white-colored CPLs by adding each of three types of fluorene-based luminescent molecules and their mixtures to N*-LCs. Herein, achiral fluorene-based derivatives with RGB emission colors were synthesized and added to N*-LCs containing alkylcyanobiphenyl- and alkylcyanoterphenyl-based N-LCs and an axially chiral binaphthyl dopant. A mixture of the RGB fluorene derivatives was subsequently prepared at an optimum mixing ratio and added to the N*-LCs. The fluorene-based derivatives dissolved in the N*-LCs exhibited induced CPLs of RGB and white colors with QY values of 60-90% and g_lum values of 0.5-1.0. The g_lum value of 1.0 is the highest among white CPLs reported thus far, and there are no examples that simultaneously exhibit both high QY and high g_lum. Furthermore, a mixture of the RGB fluorene derivatives was added to a temperature-responsive N*-LC containing a thermally invertible chiral compound, resulting in reversible thermal inversion of white CPL.