Flexible light valves using polymer-dispersed liquid crystals and TiO2/Ag/TiO2 multilayers

Abstract

The era of flexible optoelectronics demands development of wearable and bendable structures, foldable touch screens, paper-like displays, and curved and flexible solid-state lighting devices. Here, we demonstrate the fabrication of highly flexible light valves using polymer-dispersed liquid crystal (PDLC) and TiO₂/Ag/TiO₂ transparent conductive films. TiO₂/Ag/TiO₂ multilayers were prepared by magnetron sputtering technique on polyethylene terephthalate (PET) substrates at room temperature. By keeping the equivalent TiO₂ layers and varying the deposition time of the Ag layer, proper metal nanograins on TiO₂ planar plane were formed, providing the best tradeoff between the transmittance, sheet resistance and bending ability. The results are validated by numerical simulations that suggest the best match between the deposition time and individual layer thickness. Based on the performed characteristics of TiO₂/Ag/TiO₂/PET structures, several flexible light valves are fabricated and characterized. The sheet resistance values of TiO₂/Ag/TiO₂/PET remain unchanged over 1000 bending cycles. The measured driving voltage and response time values open great potential of TiO₂/Ag/TiO₂/PET for integration into next-generation ITO-free flexible and stretchable devices.