Multi-electrochromism behavior and electrochromic mechanism of electrodeposited molybdenum doped vanadium pentoxide films

摘要

Molybdenum doped vanadium pentoxide (Mo doped V_2O_5) films are prepared by cathodic electrode-position on indium tin oxide substrate from Mo doped V_2O_5 sol. As an anodic and cathodic coloration electrochromic material, the electrodeposited Mo doped V_2O_5 film presents a better cycling stability, reversibility and multi-electrochromic behavior (orange-yellow-green-blue) with an optical modulation of 60-90% in the spectral region 550-900 nm, which can be expected as a result of enhanced electron intervalence transfer between Mo~(6+) and V~(5+), V~(4+) states, in addition to V~(5+) and V~(4+) transition. The electrochromic mechanism of Mo doped V_2O_5 films is investigated with atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The surface roughness of the film increase at the different coloration states due to the increasing crystallinity degree. The change of the interlayer spacing for the host V_2O_5 and the change of the C and Li element states verify the insertion of organic solvent into the interlayer of the host V_2O_5 and some of the Li~+ ions into the sites in the V-O layers. The electrochromic kinetics process indicates that the electrochromism of Mo doped V_2O_5 films can be considered as a reversible reduction/oxidation process accompanying the insertion/extraction of Li~+ ions and electrons.