The Influence of quantum dots on the optical properties of a room temperature cholesteric liquid crystal

In the present investigation, we have undertaken photoluminescence, UV-Vis absorbance, transmission and polarised light microscopy of the composites of a cholesteric liquid crystal (CLC) doped with quantum dots (QDs). The locally formed QDs clusters may distort the CLC's helix to induce an imperfect planar texture and cause broadening of CLC's photonic band gap. This broadening is accompanied by a change of the wavelength positions of the central and both the long and short band-edges of the photonic band gap as the concentration of the doped QDs increases. A remarkable enhancement in the photoluminescence intensity of CLC materials is observed by doping with QDs. A decrement in the FWHM parameter also supports this increased photoluminescence intensity. The UV absorbance increases for the QDs dispersed CLC material and is followed by a slight red shift when compared to the pure CLC. The optical band gap obtained by the Tauc plot method suggests that the observed optical band gap narrows after the dispersion of QDs into the CLC. The outcome of these investigations proves that the dispersion of QDs in CLC is beneficial and may be useful in liquid crystal displays and other opto-electronic devices, which require less band gap materials.