Sequential Deposition of Electrochromic MoO3 Thin Films with High Coloration Efficiency and Stability

Effect of thin film deposition route on the morphology and performance of molybdenum oxide (MoO3) based electrochromic devices was investigated. For the deposition of thin films, a sequential deposition method, which includes ultrasonic spray pyrolysis (USP) and thermal evaporation methods was used. Films deposited solely using either USP or thermal evaporation method were used as control samples. Following deposition, MoO3 thin films were then characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. Surface characteristics and chemical structure of the deposited thin films were found to depend extensively on the deposition route. Electrochromic performance and reversibility of the samples were evaluated using ultraviolet-visible spectrophotometer and cyclic voltammetry. Sample prepared by USP method showed low coloration efficiency (16 cm(2) C-1), but high stability. In contrast, sample prepared by thermal evaporation had high coloration efficiency (30 cm(2) C-1), but low stability. Sample prepared by sequential deposition method showed the highest coloration efficiency (33 cm(2) C-1) among other samples and maintained its stability with cycling. The sequential deposition route investigated in this work is highly promising and might be extended to other metal oxide systems. (c) 2017 The Electrochemical Society.