Investigation on the coloring and bleaching processes of WO_3−x photochromic thin films

Abstract

WO3−x (oxygen deficient tungsten oxide) thin films and WO3−x/Ta2O5 (tantalum oxide) composite films exhibit a huge photochromic effect with 60% near-infrared transmission modulation.

Cu-Doped and Un-Doped WO3 Photochromic Thin Films

“…Fig. 6a shows that powder in ethanol suspension with a Gaussian particle size distribution from the WOCu1 powder (similar curve is obtained for the WO powder) centered on an average size equal to 23 nm is obtained from the adequate protocol already experimented in previous work [18]. The suspension remained stable with no sedimentation observed over time.…”

“…As it was reported in our previous work [17], the as-prepared WO3-x nanoparticles (NPs) by polyol method have improved chemical, morphological, structural, and optical properties, such as improved photochromic behavior. Hitherto, it encouraged us to conduct a detailed photochromic (coloring or bleaching cycles) study on thin films obtained by dip-coating from non-stoichiometric WO3-X NPs in suspension [18]. In this latest study, we have found that the photochromism phenomenon was based on two kinetic components, the photoreduction of W 6+ ions in W 5+ defects at the particle surfaces and the diffusion of the W 5+ species within the bulk of the particles, which led to a coloration mechanism from the W 5+ -W 6+ intervalence charge transfer.…”

Realizing nondestructive luminescence readout in photochromic ceramics via deep ultraviolet excitation for optical information storage

“…[8][9][10][11][12] Although most reported photochromic materials are organic compounds by far, inorganic photochromic materials possess some inherent advantages over the organic-based materials in the aspects of thermal stability, chemical resistance and fatigue properties, and hence have attracted more attention in recent years. [13][14][15][16][17][18][19][20][21] Currently, the research on inorganic photochromic materials mainly focuses on transition metal oxides (WO3, MoO3, TiO2, Nb2O5 and V2O5), [22][23][24][25][26][27] ferroelectrics (Na0.5Bi4.5Ti4O15, Na0.5Bi2.5Nb2O9, Bi4Ti3O12, KSr2Nb5O15, SrBi2Nb2O9 and K0.5Na0.5NbO3), 10,11,18,20,21,[28][29][30][31][32][33][34][35][36][37] and other robust oxides (BaMgSiO4, Sr2SnO4 and (Ca,Sr,Ba)5(PO4)3F). [38][39][40][41][42][43][44] For these materials, light-induced changes in physical properties such as refractive index, electron conductivity, magnetic properties, refractive index or absorption spectrum can be regarded as the digital code of "0" and "1", respectively.…”

Inorganic–Organic Interfacial Electronic Effects in Ligand-Passivated WO3–x Nanoplatelets Induce Tunable Plasmonic Properties for Smart Windows

“…Importantly, an increase in the specific surface area exhibits better photoreactivity in thin films. 54,55 However, most of these studies utilized tungsten trioxide (WO 3 ) materials. 6,54,56 It has been reported that photochromism in tungsten oxide occurs due to the presence of oxygen vacancies.…”