Electrically conductive thin-film color filters made of single-material indium-tin-oxide

Periodic multilayer thin-film color filters (CFs) entirely made of nano-porous indium-tin-oxide (ITO) with tunable refractive index are explored. The interference CFs are electrically conductive and transmit light in the pass-band spectral region without absorbing light outside of the pass-band region. The transfer matrix method, implemented in conjunction with a genetic algorithm optimization method, is used to design the optimal thickness and refractive index of layers for red, green, and blue (RGB) filters. RGB filters with 2 pairs (4 layers) are experimentally demonstrated by using a porosity-controlling deposition technique for a single material-ITO. A maximum transmittance of 95.2 and a minimum transmittance of 26.2 are demonstrated for the four pairs of a red filter structure. A light recycling structure using these RGB filters is proposed to reduce the optical loss occurring in conventional liquid-crystal display systems.