CdTe quantum dot dispersed ferroelectric liquid crystal: Transient memory with faster optical response and quenching of photoluminescence

Abstract

In the present study, the effect of dispersing Octadecylamine capped Cadmium Telluride quantum dots (CdTe QDs) on the memory behaviour, physical parameters and dielectric relaxations of ferroelectric liquid crystal (FLC) W-327 with the variation of dopant concentration and applied voltage has been examined. Significant changes have been observed in visible light absorbance, photoluminescence (PL), spontaneous polarization, optical response and relative permittivity of the FLC material with the addition of QDs. An average of 19% (Mix.1) and 28% (Mix.2) fastening of optical response in QDs dispersed FLC mixtures was one of the remarkable findings. Enhancement in visible absorbance along with the quenching in PL intensity has also been noticed in FLC/QD mixtures in comparison to pure FLC. The study of tan δ curves confirms the reduction of ionic impurities in the presence of QDs. Pure FLC as well as FLC/QD mixtures show time dependent memory effects. The memory behaviour of mixtures significantly depends upon the concentration of dopant CdTe. The memory effect was confirmed with the help of dielectric spectroscopy, polarizing optical micrographs and electro-optical study. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges. The QDs dispersed FLC plays a major role to enhance memory effects by trapping the impurity ions under the application of bias voltage. These studies would be helpful to provide an idea for ionic impurity free memory devices having micro-second optical response and in security coded transmission.