Enhanced coloration for hybrid niobium-based electrochromic devices

Issam Mjejri (1) , Romain Grocassan (1) , Aline Rougier (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Niobium pentoxide, Nb2O5, exists in many polymorphs with diverse properties and morphologies that are dependent on the synthesis route. In this work, we design a new approach to fabricate and stabilize the metastable polymorph hexagonal nano-niobium pentoxide using soft chemistry and in particular the polyol synthesis. The electrochromic properties of homogeneous niobium pentoxide thin films deposited by dip coating, from as-synthesized hexagonal powder, are studied in lithium trifluoromethanesulfonimide (LiTFSI) in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) ionic liquid electrolyte versus Pt as counter electrode. The structure and morphology of the Nb2O5 thin films before and after cycling are characterized by ex-situ XRD and SEM while their optical and electrochemical properties are investigated by in-situ transmittance and cyclic voltammetry (CV), respectively. Thin films made from hexagonal Nb2O5 with a sphere architecture exhibit good cycling stability, high transmittance modulations (ΔT ≈ 33% at 550 nm), fast switching speeds (2–3 s for coloration and bleaching at 550 nm), and high coloration efficiency (CE ≈ 26 cm2 C–1) with a good quality factor G(λ) = 10.4 cm2 C–1 s–1. Finally, novel electrochromic devices based on hybrid thin films combining poly(ethylene-3,4-dioxythiophene):poly(styrenesulfonicacid) (PEDOT:PSS) and oxides are assembled showing enhanced coloration and simultaneous color change due to their double-sided configuration.

Mots clés: polyol synthesis; hybrid device; nanoparticles; dip coating; niobium oxide; electrochromic performances

Domaines: Matériaux

Issam Mjejri, Romain Grocassan, Aline Rougier. Enhanced coloration for hybrid niobium-based electrochromic devices. ACS Applied Energy Materials, 2018, 1 (8), pp.4359-4366. ⟨10.1021/acsaem.8b00967⟩. ⟨hal-01865041⟩