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Proceedings Paper

Kinetic behavior of WO3-doped Nb2O5 thin films
Author(s): Luciana O. Melo; Douglas C. Dragunski; Cesar O. Avellaneda; Agnieszka Pawlicka
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Paper Abstract

An electrochromic material (EC) reversibly changes its optical characteristics response, coloring and bleaching states when a small voltage or current is passed through it. This phenomenon is used to develop electrochromic devices like smart windows, which control the amount of heat and light entering in a building and optimize energy consumption. The change of the transparency of these devices involves the injection and extraction of small cations and electrons into the EC material and study of the kinetics of ions injection implies on operation understanding of these devices. Pure and doped niobium oxides (Nb2O5) are promising cathodic electrochromic materials and their electrooptical performance depends strongly of its structural morphology. The sol-gel process allows for facile fabrication of large area coatings at a low cost and offers advantages of controlling the composition and microstructure of the films. In order to study the solid sate diffusion of lithium into Nb2O5, Nb2O5:Li+ and Nb2O5:WO3, two electroanalytical techniques have been used i.e. galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). GITT have been applied in order to obtain the chemical diffusion coefficient of Lix in Nb2O5 doped and undoped films, where the values approaching were of the 2.5x10-11 cm2s-1 at x=0,83, 7.4x10-13 cm2s-1 at x=1.65 and 1.6x10-10 cm2s-1 at x=0.33 for Nb2O5, Nb2O5:Li+ and Nb2O5-WO3 respectively. From these measurements it was also observed that within each film, D increases as x increases.

Paper Details

Date Published: 25 July 2003
PDF: 7 pages
Proc. SPIE 4986, Physics and Simulation of Optoelectronic Devices XI, (25 July 2003); doi: 10.1117/12.500985
Show Author Affiliations
Luciana O. Melo, Univ. de Sao Paulo (Brazil)
Douglas C. Dragunski, Univ. de Sao Paulo (Brazil)
Cesar O. Avellaneda, Univ. Federal de Sao Carlos (Brazil)
Agnieszka Pawlicka, Univ. de Sao Paulo (Brazil)

Published in SPIE Proceedings Vol. 4986:
Physics and Simulation of Optoelectronic Devices XI
Marek Osinski; Hiroshi Amano; Peter Blood, Editor(s)

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