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Effect of humidity on structure and electrochromic properties of sol-gel-derived tungsten oxide films

IR@NPL: CSIR-National Physical Laboratory, New Delhi

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Title Effect of humidity on structure and electrochromic properties of sol-gel-derived tungsten oxide films
 
Creator Deepa, M
Singh, P.
Sharma, S. N.
Agnihotry, S. A.
 
Subject Energy Fuels
Materials Science
Applied Physics/Condensed Matter
 
Description The influence of varying relative humidity (RH similar to 55 and 75%) during thin film deposition from an oxalato-acetylated peroxotungstic acid sol by dip coating, on the microstructure and electrochromic properties of pristine tungsten oxide (WO3) films obtained upon annealing is presented. The films fabricated under a relative humidity of 55% are amorphous whereas the ones cast under a substantially humid atmosphere (RH similar to 75%) are characterized by interconnected nanocrystallites with a triclinic phase and a nanoporous surface morphology as well. Upon lithium insertion, larger integrated values of transmission modulation and coloration efficiency are observed over the photopic and solar regions, for the films prepared under a RH-75% as compared to that observed for the films deposited under a RH of 55%. Functional improvements are due to the larger surface area of nanocrystallites and a porous microstructure, a consequence of a higher degree of hydration and hydroxylation in the former films in contrast to the non-porous and a rather featureless structure of the latter films. Faster switching kinetics between the clear and blue states, a greater current density for lithium intercalation, a higher diffusion coefficient for lithium and a superior cycling stability, again shown by the film fabricated under a 75% RH confirm that the WO3 film microstructure is most conducive for a more facile ion insertion-extraction process, which hints at its potential for electrochromic window applications.
 
Publisher Elsevier
 
Date 2006
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://npl.csircentral.net/2458/1/45.pdf
Deepa, M and Singh, P. and Sharma, S. N. and Agnihotry, S. A. (2006) Effect of humidity on structure and electrochromic properties of sol-gel-derived tungsten oxide films. Solar Energy Materials and Solar Cells, 90 (16). pp. 2665-2682. ISSN 0927-0248
 
Relation http://npl.csircentral.net/2458/