Photonic Ink (P-Ink) technology comprises an active photonic crystal that reflects a band of color that can be tuned by controlling the applied current or voltage. All the individual spectral colors in the visible range can be reflected by a single P-Ink material. This technology provides an opportunity to create a wider range of primary colors than the conventional RGB system, given the same numbers of pixels for color mixing.
Hai Wang, Fergal Kerins, Ulrich Kamp, Leonardo Bonifacio, André C. Arsenault, Geoffrey A. Ozin, "Photonic Crystal Display Materials" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP27), 2011, pp 12 - 15, https://doi.org/10.2352/ISSN.2169-4451.2011.27.1.art00006_1