Electrochromism of Sn-Modified WO[sub 3] Electrodes Prepared from Sol-Gel Method

Abstract

Effects of SnO 2 addition on the structural, electrochemical, and electrochromic properties of WO 3 electrodes were investigated, in which both the WO 3 and SnO 2 -WO 3 were synthesized via a sol-gel method. The SnO 2 -WO 3 composite electrode, whose chemical states were identified through X-ray photoelectron spectroscopy analysis, gave the optical modulation of 38.3-99.5% and faster response times of 0.7 and 3.3 s. The coloration efficiencies of the SnO 2 -WO 3 electrode were greater ͑49.7 cm 2 C −1 ͒ by 14% than the WO 3 alone, together with the improved memory effect and durability during the electrochromic cycling tests up to 300 cycles.Electrochromic materials represent a reversible change in color under an applied electric field; thus, their devices are of considerable interest for the potential applications in information displays, light shutters, smart windows, and variable-emittance radiators with their low power consumption, high coloration efficiency ͑CE͒, and memory effect. [1][2][3] Among various transition metal oxides with the electrochromic properties ͑e.g., W, Ni, V, Mn, Mo, Cr, Ti, Nb, Co, Rh, and Ir oxides͒, tungsten oxide ͑WO 3 ͒ and nickel oxide ͑NiO͒ have been widely used as cathodic and anodic coloration electrochromic materials, respectively. 2-5 In particular, WO 3 has been extensively studied because it has a relatively fast response time and high CE compared to other electrochromic materials. The electronic structure of WO 3 can be readily modified by injection and extraction of ions with electrons, accompanying reversible optical changes from transparent states to visible light absorbing states, as represented by the following electrochemical reactions on the WO 3 in an acidic condition 1,4Various methods, such as sputtering, chemical vapor deposition, and electroplating, have been employed to improve electrochromic properties of oxide-based materials. For example, Avendano et al. 6 used a reactive dc magnetron sputtering system to prepare Ni-based oxides with compositions of Ni, NiV 0.08 , NiAl 0.56 , and NiMg 0.8 . They showed that Al-and Mg-containing Ni oxide films produced significantly increased luminous transmittances as compared to the Ni oxide alone, making them suitable for applications requiring a high bleached-state transmittance. Meda et al. 7 reported that porous nanocrystalline W oxide films prepared by organometallic chemical vapor deposition showed a fast response time with CE of 22 cm 2 C −1 at 630 nm. Also, a radio frequency ͑rf͒ magnetron cosputtering to prepare NiO-Ta 2 O 5 nanocomposite electrodes was demonstrated with high optical-transmittance modulation of 41-95%, high CE ͑ca. 30.5 cm 2 C −1 at 633 nm͒, and good durability. 3 A sol-gel technique has been regarded as an efficient method to synthesize ceramics via intermediate sol and gel states; 8 thereby, the sol-gel prepared electrochromic materials have received much attention because of simple fabrication with low cost. For example, a sol-gel prepared W oxide film was demonstrated by Biswas et al. 9 that ...

Electrochromic properties of tungsten oxide nanowires fabricated by electrospinning method

“…The electrochemical and optical properties of the electrospun WO 3 NWs prepared on the ITO-coated glass substrates were investigated and compared with that of thin film WO 3 electrode which was prepared on the ITO-coated glass by the conventional sol-gel process [26,27]. Fig.…”

Electrochromic Metal Oxides: Recent Progress and Prospect

“…[10] Researches on metal doping have been performed on Nb, [20] Mo, [17] Ni, [46,47] Ti, [48] Ru, [49] V, [50] Ce, [51] and Sn, [52] and the results have shown that WO 3 with metal doping can have superior properties in one way or another. [10] Researches on metal doping have been performed on Nb, [20] Mo, [17] Ni, [46,47] Ti, [48] Ru, [49] V, [50] Ce, [51] and Sn, [52] and the results have shown that WO 3 with metal doping can have superior properties in one way or another.…”

“…In practice, considerable attention has been given to the metal‐doped WO 3 , expecting to further improve the coloration efficiency, reaction kinetics as well as optical modulation of WO 3 by introducing the metal ions with lower oxidizing capacity than the host WO 3 . Researches on metal doping have been performed on Nb, Mo, Ni, Ti, Ru, V, Ce, and Sn, and the results have shown that WO 3 with metal doping can have superior properties in one way or another . For example, the addition of Ti to WO 3 was reported to stabilize the structure and can significantly promote the cycling performance .…”

Aqueous synthesis of tin- and indium-doped WO3 films via evaporation-driven deposition and their electrochromic properties

“…Doping with metal ions (such as Ni and Ti, among others) has been widely investigated as another strategy for making high-performance WO 3 electrochromic materials. [24][25][26][27] Bathe et al investigated the inuence of Ti doping on the electrochromic properties of WO 3 thin lms prepared by pulsed spray pyrolysis, and suggested that doping WO 3 with Ti induced a phase transformation from monoclinic to amorphous and a rough surface morphology, resulting in improvement in the cycle stability, charge storage capacity, and reversibility of the lms. 24 Cai et al prepared Ti-doped WO 3 lms with a hierarchical star-like structure by a hydrothermal method, where the star-like structure had a low charge-transfer resistance and ion diffusion resistance, leading to fast switching speed and high coloration efficiency.…”