Nano particles induced vertical alignment of liquid crystal for display devices with augmented morphological and electro-optical characteristics

Abstract

In this work, vertically aligned electro-optical (E-O) cells were fabricated using plane Indium–Tin-Oxide (ITO) substrates without any surface treatment of ITO for the alignment of liquid crystal (LC) molecules. Experimentally, using a specific amount (0.3% wt/wt) of Zinc oxide (ZnO) nano particles (NPs) in NPs-LC mixture, a high quality vertically aligned liquid crystal (VALC) was achieved in cells without compromising physical properties of LC. Results reveal much improved morphological and E-O characteristics of display cells by lowering the threshold voltage to 1.68 V for NPs induced VALC compared with 1.86 V for polyimide induced vertically aligned liquid crystal (PIVALC) cell. The operating voltages were observed 1.96 V and 2.2 V for NPs induced VALC and PIVALC cells, respectively. The contrast ratio (CR) was obtained ∼12.4% better for NPs induced VALC cell compared with PIVALC cell. Further, isotropic temperature (Tiso) behavior was studied with polarized optical microscope (POM) and found in same order of value of temperature for both NPs induced VALC as well as PIVALC cells. Additionally, using UV–Visible spectroscopy study, optical band gap (Eg) was calculated and found in agreement with reported values of LC system.