Physical Properties of SnO2/WO3 Bilayers Prepared by Reactive DC Sputtering

Abstract

The combination of transparent and conductive SnO2 with colored WO3 thin films has interesting uses in electrochromic windows, photovoltaic cells and photocatalytic systems, where the SnO2/WO3 bilayer can improve the device efficiency by increasing the charge separation and extending the energy range of photoexcitation. In this work, SnO2 and WO3 thin films were prepared by reactive DC sputtering from Sn and W targets, respectively. Single layers and bilayers deposited on glass substrates have been analyzed by X-ray diffraction, atomic force microscopy, spectrophotometry, and electrical measurements. SnO2 crystallizes in the cassiterite structure, whereas amorphous WO3 is obtained on bare and SnO2-coated glasses, showing higher surface roughness on the SnO2 layer. Different oxygen vacancy defects have been identified in WO3 by analyzing photoconductivity transients. The oxygen vacancy defects are responsible for the sub-bandgap absorption that causes coloration in the WO3 films. Regarding SnO2, it shows a high transmittance of about 90% in the visible and near-infrared spectral ranges.

Scaling-Up of Solution-Processable Tungsten Trioxide (WO3) Nanoparticles as a Hole Transport Layer in Inverted Organic Photovoltaics

“…Interestingly, the Raman spectra collected upon the agglomerates show features compatible with a higher crystalline character, which is slightly improved by annealing, as confirmed by the sharp signal around 810 cm −1 and by the appearance of the small shoulder around 710 cm −1 after annealing at 120 °C and 150 °C (curves (C) and (D) in the left panel) [56]. It is worth mentioning that the intensity of the shoulder at 710 cm −1 is still very small and that the Raman spectra all share a common feature around 950 cm −1 , which is characteristic of amorphous WO3 films [57]. All these observations, together with the XRD suggest that the slot-die-deposited WO3 films are characterized by a prevalent amorphous general character.…”

Enhancing Electrical Properties and Seebeck Effects of WO3 Thin Films Using Spray Pyrolysis: Insights into the Conductivity and Carrier Type

“…Previous studies have reported the intrinsic reaction mechanism of WO 3 /elaectrolyte interfaces in various electrolytes [20][21][22][23]. The deposition of WO 3 thin films has been achieved through various techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD) [24], evaporation [25][26][27], electrodeposition [28], sputtering [29][30][31][32], sol-gel deposition [27,33], and spray pyrolysis technique [34][35][36][37]. The latter technique presents many advantages such as (i) short time deposition, (ii) simple technology, (iii) low-cost, (iv) no need for vacuum, and (v) large-scale area of thin film production.…”