Novel thermochromic (TC) and electrochromic (EC) characteristics of the V₄O₇ liquid crystal for LCDs and versatile optoelectronic applications

To form an electrochromic cell, the chemical reaction procedures were obeyed to prepare the V₄O₇ crystal suspended in a strong electrolytic HCl solution. Some of these suspended V₄O₇ crystals were injected between two sealed parallel ITOs/glass' slabs to construct an optoelectronic cell. A spray system technique was used to deposit the residue of the V₄O₇ solution as thin-film over glass' slabs. X-ray diffraction pattern (XRD), Field Emission Scanning electron microscopy (FESEM) with Energy Dispersive Analysis X-Ray (EDAX), and optical characterizations were used to inspect the obtained crystals. The structural investigations confirmed the hexagonal crystalline nature of the V₄O₇ crystal. The thermochromic (TC) and the electrochromic (EC) measurements showed that the studied V₄O₇ liquidus crystals have high sensitivity for the external either heat or the applied electric field. The applied thermal and electrical influences caused the direct optical band gap to change from 3.8 eV to 3.98 and 4.03 eV under EC and TC tests, respectively. The third-order nonlinear optical susceptibilities reached their maxima about 4.4 × 10⁻¹¹ esu and 5.9 × 10⁻¹¹ esu under TC and EC effects. The nonlinear refractive index was varied till reached 5.26 × 10⁻¹⁰ and 6.91 × 10⁻¹⁰ under TC and EC, respectively. Such properties plus optoelectronic response time about 1.5 mSec and high stability all qualifies this inorganic cell to be nominate for light modulation applications, i.e., optical filters, inorganic liquid crystals display (LCD), smart windows, optical switching, and optical fibers.