BINOL induces chirality in polyfluorene-based electroluminescent polymers in solid state

Abstract

Nowadays circularly polarized luminescence (CPL) gains much attraction because it can be applied to a variety of fields. An efficient method to achieve CPL is blending achiral emissive polymers with chiral small-molecule additives as a chiral inducer. In this work, we demonstrate that 1,1′-Bi-2-naphthol (BINOL) acts as a chiral-inducer for poly (9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) in a thin film. In the thin films of F8BT/BINOL before annealing, only circular dichroism (CD) signals of BINOL were observed. After the annealing at 120 °C, clear CD signals of F8BT were observed indicating that the chiroptical property was induced on the F8BT thin films. The CD signal intensity was enhanced by increasing the annealing temperature up to 200 °C. By optimizing the concentration of BINOL and the annealing temperature, we obtained a dissymmetry CD value of 0.012. Photoluminescence quantum yield of the F8BT/BINOL thin films was also increased after the annealing.