Electrochromic Nanomaterials Based on Hybrid Molybdenum-Tungsten Oxide: Synthesis, Wet Coating and Structural / Optoelectronic Characterizations

Hybrid Molybdenum-Tungsten oxides nanomaterials are obtained by solvothermal synthesis. In comparaison with undoped WO3-x, a boost in the optical signature has been observed, which can be linked to a concentration increase of reduced species and oxygen vacancies in the material. The « MoWOx » powder is then wet-processed as thin film by spin coating and succesfully used as plasmonic EC material, dispalying a selective and independent modulation of both visible and NIR wavelengths as a function of the applied potential.PLASMON_E

Comparative investigation of the Ti and Mo additives influence on the opto-electronic properties of the spray deposited WO3 thin films

In this paper we compare the optical and electrical properties of the WO3 thin films containing 2, 5 and 10 at.% of Ti and Mo additives, deposited by spray pyrolysis. The influence of the type and additive concentration on the nanostructure, topography and composition of the WO3 layers are mainly related to the surface tension energy changes, and further correlated with the (photo)electrical and optical properties. The FTO/WO3 junction through its characteristic, namely barrier height, ideality factor, flat band potential, and series resistance, served as a tool for associating the before mentioned characteristics.The morphology of the WO3 thin films densifies and the roughness is reduced with increasing Ti and Mo concentration, in good agreement with solution surface tension reduction. WO3 based films exhibit a p-type semiconducting behavior, as confirmed also by the Mott–Schottky analysis, with a lower p-type conductivity for the Ti–WO3 films, as higher number of oxygen vacancies are generated by Ti addition. Changes in conductivity are mainly attributed to the oxygen vacancies concentration evolution at the film surface due to oxygen/water adsorption. For heavily doped WO3 thin films the contribution of these surface processes to the overall conductivity is reduced since surface reactivity is lost by densification.As opposed to Ti-doping which has a detrimental effect on layers structure, Mo addition, even in high concentrations, has a positive effect on layers crystallinity; hence higher conductivity and ideality factors close to 1 are obtained for these films. Surprisingly, Ti and Mo–WO3 films contain cation additives also in lower oxidation states, 3+ and 5+, respectively, compared to the ones in the precursor salt. A 2 at.% Ti concentration is enough to significantly improve the photoconductivity of the WO3 films, whereas for Mo addition higher levels are needed (10 at.%). The Ti and Mo–WO3 films have high transparency with average transmission values of 85% and 75%, respectively. The thin films reflectance decreases with increasing doping concentration along with roughness diminution

Nano-vanadium pentoxide films for electrochromic displays

We demonstrate the benefit of homemade nanopowder precursors on the electrochromism of V2O5 films deposited by the “Doctor Blade” method. Using the polyol process, nanostructured V2O5 powder were synthesized. Orthorhombic V2O5 thin films deposited from as-synthesized powder exhibit good cycling stability associated with significant reflectance modulation in both lithium- and sodium-based electrolytes. The orange to green reversible color change appears well suitable for display application. To conclude, the electrochromic performances of complete devices using WO3 as complementary electrode and 0.3 M Lithium Bis(Trifluoromethanesulfonyl)Imide LiTFSI in BMITFSI plastified with polymethylmetacrylate (PMMA) membrane electrolyte are reported

Heterostructured ZnO/RuO2 photocatalyst: influence of sputtering temperature on the photocatalytic and photoelectrochemical properties

Influence of thermal conditions on the performance of heterostructured ZnO/RuO2 in their photocatalytic and photoelectrochemical properties Photocatalytic materials are highly investigated due its vital role in wide variety of applications that could help in tackling present day environmental problems. Inspite of wide and basic investigation for several decades on promising materials, the best photocatalyst is still under research. But the decades long research helped in better understanding of the materials and mechanisms involved. This led to the improvement of materials under examination from homostructured to modified materials. One of the major limiting factors of homostructured (single) photocatalyst is the fast recombination of excited charge carriers. Among several modification techniques used to enhance the lifetime of charge carriers, heterostructure formation with two different materials is very promising. Here, we report the formation of ZnO/RuO2 by involving two steps: ZnO nanorods are grown on FTO by hydrothermal method, followed by physical deposition of RuO2 (At room temperature [RT], At RT followed by Insitu-Post Annealing at 250° & At High Temperature [HT] 400°), resulting in the formation of a heterostructure. The influence of different thermal conditions on the course of RuO2 deposition has been characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS) and Photo Luminescence (PL). The crystallinity of the material and its orientation was examined by XRD. Morphological studies by SEM revealed the growth of randomly oriented ZnO nanorods on FTO, whereas images of ZnO/RuO2 resulted in no structural difference. A very thin layer of RuO2 covering the surface of ZnO nanorods was observed through TEM. This displayed the core-shell type of heterostructure formation. XPS studies of ZnO/RuO2 under varying conditions implied the shift towards lower binding energy, which indicates the bond sharing between both materials. Interface studies by step-wise deposition of RuO2 on ZnO, showed the evidence for formation of band bending between two materials, which play an important role in enhancing the charge carrier separation. PL of homostructured and heterostructured materials led to the understanding with carrier recombination process. There was evidence of significant quenching for ZnO/RuO2, compared to that of ZnO. Among ZnO/RuO2 (At RT, RT-PAd, HT) – deposition at 400° disclosed higher quenching, i.e., reduced rate of recombination. Photocatalytic and Photoelectrochemical investigations was clearly correlating to the characterizational studies, confirming the enhancement in performance with heterostructure, especially with the ZnO/RuO2 (400°).Metal oxides heterostructured films with controlled architecture for enhanced photocatalytic propertie

Bimodal titanium oxide photoelectrodes with tuned porosity for improved light harvesting and polysiloxane-based polymer electrolyte infiltration

In this article, we discuss the effect of the polysiloxane-based poly(ionic liquid) (PIL) electrolytes viscosity on the infiltration into mesoporous and bimodal TiO2 thin films with different thickness, and consequently on the DSSC performance. The mesoporous films contain small mesopores of 8–10 nm, resulted from the use of Pluronic P123 surfactant (SOFT), resulting in high surface area. The DUAL (soft/hard) templated films have unique bimodal porous structures comprising 8–10 nm mesopores and 60–70 nm macropores resulted from the use of P123 and 130 nm polystyrene beads, which encouraged the electrolyte pore infiltration and light harvesting. Electrochemical impedance spectroscopy confirms the lower charge transfer resistance of the DUAL templated TiO2 films as opposed to SOFT TiO2 electrodes which corresponds to higher DSSC efficiency, despite having lower dye adsorption thanks to the improved PIL electrolyte infiltration within larger pores. The addition of ionic liquids to PIL significantly lowers the viscosity, increases the ionic conductivity and I3 − diffusion rate, resulting in noticeable improvement in photovoltaic performance in both SOFT and DUAL templated photoanodes for all the observed thickness