Color-tunable triple state 'smart' window

Materials that rapidly change their optical properties in response to external stimuli are crucial for displays and ‘smart’ window applications. In this work, we describe a fluorescent red dye modified with liquid crystal side chains to be interactive with a liquid crystal host resulting in a color-tunable triple state smart window. The dye solubilizes in the liquid crystal matrix with increasing temperature, resulting in a red colored, absorbing state, recovering transparency again by re-aggregation of the dye within minutes upon cooling. This dye is used to fabricate a device that can be electrically switched from a red colored, absorbing state to an intermediate scattering state, and at greater electrical fields, a transparent state. Using a second dichroic fluorescent dye, heating the device transitions the window’s color from yellow/green to red. The multi-responsive optical changes could find applications in many fields including displays, smart windows, electricity generation and signage.