Analysis of photoluminescence, UV absorbance, optical band gap and threshold voltage of TiO2 nanoparticles dispersed in high birefringence nematic liquid crystal towards its application in display and photovoltaic devices

Abstract

In the present work anatase TiO2 nanoparticles (NPs) have been dispersed into the pure nematic liquid crystal (NLC) 2020 which is consisted of fluorinated 4'-alkylphenyl-4-isothiocyanatotolanes, in different concentration. The dispersion of TiO2 NPs in NLC induces photoluminescence what is an important finding of this study. It has also been found that the dispersion of TiO2 NPs reduces the UV absorbance of pure NLC. Optical band gap has been calculated and found to be decreased for the dispersed system as compared to pure NLC. The presence of TiO2 NPs affects the molecular dynamics of the NLC molecules, which has been proved by the Fourier transformed infrared spectroscopy (FTIR). Relative electric permittivity and dielectric anisotropy have been found to be decreased for the dispersed system as compared to the pure NLC. The trapping capability of TiO2 NPs is also confirmed by the independent measurement of threshold voltage. The value of threshold voltage has decreased after dispersion of NPs in the pure NLC. This decrement is due to the property of TiO2 NPs to reduce the ionic contribution, thereby, increasing the net field of the system. The induction of photoluminescence in a non photoluminescent material with the help of TiO2 nanoparticle along with reduced band gap are the main findings of the present work. It is suggested that the output of the present work may be very useful in various display and photonic applications as well as in photovoltaic devices.