WO3 Thin Films Active in the IR Region

This paper reports the enhancement of the electrochromic properties in the infrared, IR, region of radio frequency sputtered WO3 thin films thanks to a careful optimization of the deposition conditions. From the combination of various techniques of characterization, the optical performances, in particular, the contrast in reflectance between the inserted state and the deinserted one, upon cycling in H3PO4 liquid electrolyte, are correlated to the film morphology and composition. Films, grown in higher chamber pressure, exhibiting a lower density and a O/W ratio higher than 3, show the most promising behavior. Finally, first trends on the incorporation of the WO3 single layer in full electrochromic devices are discussed.