KCS

Electrochromic displays (ECDs), a reflective one by means of a color change induced by electrochemical reactions, has been attracting keen interest because of its potential application as strong candidate for low-cost, high-volume electronic papers. One of the advantages of the ECDs is the high reflectivity of its white state. We developed the synthesis method of the electrochromic nanoparticles of Prussian blue Fe[Fe(CN)6]x and its metal-substituted analogues. With the nanoparticle, we can control the dispersibility by the surface modification. We synthesized the nanoparticles dispersible into water, alcohols, and organic solvents, indicating that we can fabricate the ECDs with the nanoparticles by coating or printing. Another advantages of the nanoparticle is enhancement of stability in electrochemical reactions. For example, we have succeeded in synthesizing Zn[Fe(CN)6] nanoparticles showing stable electrochemical reactions by reducing its particle size less than 100 nm. Our ECD with Prussian blue nanoparticles exhibits color change between blue and white only with a 1.5 V dry battery even after operations of 1,000,000 times. The reflectivity of the white state is more than 50 %.