Prussian green films exhibiting typical four-colors electrochromic properties

Only utilizing hydrochloric acid and potassium ferricyanide as reaction reagents, Prussian Green (PG) films were facilely fabricated on fluorine doped tin dioxide glasses by a hydrothermal method. The amount of hydrochloric acid and the temperatures of hydrothermal treatment significantly affect the component and color of as-prepared films. The optimal preparation conditions are 0.5-1 mL of hydrochloric acid and hydrothermal temperature of 100-120 degree celsius. The hydrochloric acid plays the role of both as a reducing agent and providing acidic conditions. The PG devices based on as-prepared PG films firstly exhibited typical four-colors electrochromic properties: yellow, green, blue and colorless states, respectively, under different power supplies, which exhibit its potential application in nonemission display field.