A europium ion doped WO3 film with the bi-functionality of enhanced electrochromic switching and tunable red emission

We first doped europium (Eu) ions into WO3 using a hydrothermal method. The effects of Eu ions on the structure, morphology, and electrochromic and photoluminescence performances of WO3 films have been systematically investigated. It is found that a WO3 film doped with Eu ions exhibits the bi-functionality of electrochromic switching and red emission. Compared with an undoped WO3 film, a WO3 film doped with 10% Eu ions shows a remarkably enhanced optical contrast of 80.7% at 680 nm, a faster coloration response of 7.2 s, and more than 3 times higher coloration efficiency of about 57.85 cm(2) C-1. Moreover, a WO3 film doped with Eu ions could be excited by 260 nm ultraviolet light and exhibit a tunable red emission as a response to the applied electric field. This novel and bifunctional WO3 film shows potential in preparation of illuminable smart windows''.