Viologen-based electrochromic compositions which can be formulated and applied at room temperature

The invention relates to electrochromic compositions comprising: (a) a viologen derivative of formula (I) (b) an electron mediator; (c) a polymer compound of formula (II) (d) a plasticizer of formula (III): and (e) a mixture of at least two miscible solvents which dissolve components (a) to (d) at room temperature, at least one of them being a solvent with a high boiling point. Said electrochromic compositions can be formulated and applied at room temperature, therefore they allow preparing electrochromic devices with heat-sensitive substrates, particularly with fully plastic substrates, with a high degree of transparency and with a high optical contrast.