In this article, a set of Prussian Blue (PB) thin films with different electrodeposition times (25 s, 50 s, 75 s, 100 s and 150 s) in air at ambient temperature was prepared. The layers were characterized by a variety of techniques which include, field effect scanning electron microscopy, energy-dispersive X-ray spectrometer, X-ray diffraction, Fourier transform infared spectroscopy, UV-Vis spectrophotometry, and electrochemical analysis. A simple and exact electrochemical method was used to estimate the optimal voltages for coloring and bleaching of different PB layers. Controlling electrodeposition time along with applying suitable voltage enabled us to investigate and improve electrochromic properties of PB layer. The sample prepared under 75 s deposition time showed probably a composition intermediate between the insoluble and soluble form. Furthermore, this sample (S75) shows a better electrochromic properties. High value of electrochromic contrast 55.36 % at 555 nm and well stability of ion exchange by cycling are the characteristics of this layer. The control of the deposition time resulted in an increase of 9.38 times of the contrast ratio and corresponding values for optical density (DOD) of the PB layers.

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It has been long recognized that solid polymer electrolytes (SPEs) are potentially interesting for solid‐state electrochemical devices. Gellan gum (Ge)‐based SPEs, plasticized with glycerol (Gly) and doped with lithium bis(trifluoromethanesulfone)imide (LiTFSI) were prepared by the solvent casting technique, and their properties were evaluated. LiTFSI‐based SPE systems exhibit, on the average, higher conductivities than similar systems with other lithium salts. The structure, morphology, complex impedance spectroscopy, cyclic voltammetry and thermal stability of the new electrolyte system were characterized. Electrochromic devices (ECDs) were built with optimized electrolyte samples and their performance was analyzed. The samples were applied in small ECDs with glass/ITO/CeO2‐TiO2/SPE/Prussian blue/ITO/glass configuration. The devices presented a two‐modulation operation: a semi‐bright mode (−2.5 V) and a dark mode (+0.5 V). The best results were obtained with the ECD containing the GeGly1Li2.4 electrolyte, for which the transmittance (T) values in the bleached and colored states were ca. 33.4/43.0 % and 5.4/8.8 % at 555/1000 nm, respectively. These results correspond to ΔT and ΔOD values of 28.0/34.2 % and 0.79/0.69, respectively, which give quite high CEin and CEout values of −4925 cm2 C−1 for bleaching (Qin=−272.1 μC cm−2), and 2062 cm2 C−1 for coloring (Qout=650.0 μC cm−2), at 630 nm. This electro‐optical performance suggests that the proposed SPE systems are promising materials to be further investigated and applied in ECDs.