Optoelectronic and Dielectric investigation in Ferroelectric Liquid Crystal composites doped with TGA caped CdSe Quantum Dots

Abstract

The quantum confined II-VI semiconductor material becomes interesting area of research due to its large photonic band gap. A series of thiol capped CdSe quantum dot has been synthesized at different temperature in aqueous solution using thioglycollic acid (HSCH2COOH, TGA) as stabilizer and optimized reaction temperature 85oC for the growth of CdSe quantum dots, heaving high quantum yield corresponding to photoluminescence. The overall growth mechanism of CdSe quantum dots depends upon the various factors affecting the experimental conditions, including the Se-to-Cd ratio, temperature, time, and precursor concentration, which was optimized with the help of different set of experiments and getting characterized for their optical properties with the help of UV-Vis and Photoluminescence spectroscopy.

Fluorescence spectroscopy revealed that the valence band of CdSe quantum dot is situated at higher energies with respect to the radox level of most thiols, and hence inhibiting hole trapping as a result of that maintains a high luminescence efficiency. The average size (7nm) of TGA capped CdSe quantum dots prepared at 85oC was confirmed by Transmission Electron Microscopy (TEM) and getting dispersed into ferroelectric liquid crystal for improvement in electro-optic switching and molecular relaxation behaviour of CdSe quantum dot doped FLC composites with the help of polarization rewersal technique and dielectric spectroscopy. Temperature dependent dielectric properties of dielectric properties of 0, 0.25, 0.5,1 weight % CdSe doped FLC was investigated, which shows the phase transition behaviour in CdSe doped FLC composites. Polarization switching current response of these composites shows the improvement in electrical switching, which reflects the switching response time.