A Reflective Color Filter Based on ITO-Ba0.5Sr0.5TiO3-ITO Nanofilms Capitalizing on a Black Layer

A reflective color filter was proposed based on ITO (Indium Tin Oxide)-Ba0.5Sr0.5TiO-ITO multiple nanofilms. A black layer was capitalized on to absorb the incoherent scattered light and to enhance the contrast ratio of the reflected light. While the thickness of BST (Ba0.5Sr0.5TiO) thin film changed from 100 nm to 140 nm, the peak wavelength of the reflected light shifted from 380 nm to 500 nm as the refractive index of BST thin film was set as 2.4. Meanwhile, the visualized color of the multiple nanofilms was changed from purple to turquoise. The measured reflected spectra fitted well with the simulation results based on transfer matrix method. The fabricated samples proved that the black layer played an important role in the contrast ratio increase. When the BTO thin film was 170 nm thick, the reflected peak wavelength shifted from 595 nm to 510 nm as its refractive index was tuned from 2.4 to 2.0 under a driven DC voltage. The unique characteristics show great potential in selectively reflective chromatic systems.