Red, Green, and Blue Reflections Enabled in an Electrically Tunable Helical Superstructure

Materials with tunable optical properties in the visible spectrum are intriguingly important in science and technology. Such desired tunability can be conveniently accomplished by controlling optical materials with electric field. Now an organic film of self-organized helical superstructure producing electrically tunable reflection of visible light is introduced in this work. The composite is a dual-frequency thermosensitive cholesteric (DFTC) material consisting of a liquid crystal host doped with a binary chiral-dopant mixture including a thermosensitive chiral switch. The red, green, and blue reflections in the DFTC film can be obtained by varying the frequencies of a 45 Vrms applied voltage to induce dielectric heating. The resulting variation in temperature and, in turn, in helical pitch length, enables various wavelengths of reflection to render full-color display in a single film without the need of film stacking. As far as it is known, this is the first work to demonstrate broad electrical tuning of cholesteric reflection in red, green, and blue.