Influência da Dopagem com Molibdênio nas Propriedades Eletrocrômicas dos Filmes Finos de Nb2O5: Li+ preparados pelo Processo Sol-Gel e a Técnica de Spin-Coating

Abstract

This work consists of the study of the influence on structural, electrochemical and optical properties of doped molybdenum in thin films of Nb2O5: Li+ , and the relationship between structure and electrochromic performance of films obtained with different heat treatments for evaluation the application of these in electrochromic windows. The doping with molybdenum aims at improved electrochromic performance of Nb2O5, which has low staining efficiency, slow response time, small electrochromic memory, among others. The distinct temperatures used in heat treatment will probably lead to different structures and thus different electrochemical and optical properties. The sols were produced by the sol-gel process from a mixture of niobium pentachloride, n-butanol, acetic acid and lithium salt subjected to ultrasound for a few minutes, and further addition of the molybdenum alkoxide under magnetic stirring. The spin-coating technique was used for sun deposition on the glass substrate coated with conductive layer (ITO - Asahi). They obtained two groups, A and B, samples with group A undergoes heat treatment between layers 350 °C and final heat treatment of 450 °C and group B thermal treatment between layers 450 °C and final heat treatment of 560 °C, all in air atmosphere. The crystal structure of the xerogel were studied by X-ray diffraction and the film surface by microscopy, SEM and AFM. The performance of the films was studied by electrochemical cyclic voltammetry, chronocoulometry and impedance, as well as optical transmission from ultraviolet to visible measurements performed in-situ. The temperature used in Group B took crystalline structure, TT phase and films with low roughness, although films with high stability and good reversibility over the cycles. The doping with molybdenum was more favorable for lower temperatures, however led to positive contribution for the two groups, the transmittance values.