LAUSR

Bi2O3 is a polymorphic material with δ phase most known for its highest oxide ion conductivity. In this work, Bi2O3 thin films were prepared by sol–gel technique with annealing temperature of 450 and 550 °C. Electrochromic performances of the films were inspected. It discovered that the color state of the Bi2O3 thin films switched between black and light yellow transparent when applying a voltage of −2 ~ 2 V. Electrochromic degradation was further observed in the thin films. However, steadier electrochromic efficiency was found in the film annealed at higher temperature. This could be related to the larger δ-Bi2O3 phase fraction which may contribute to higher conductivity and show positive electrochromic effect.Graphical abstractBi2O3 is a polymorphic material with δ phase most known for its highest oxide ion conductivity. In this work, Bi2O3 thin films were prepared by sol–gel technique with annealing temperature of 450 and 550 °C. Electrochromic (EC) performances of the films were inspected. It discovered that the color state of the Bi2O3 thin films switched between black and light yellow transparent when applying a voltage of −2 ~ 2 V. EC degradation was further observed in the thin films. However, steadier EC efficiency was found in the film annealed at higher temperature. This could be related to the larger δ-Bi2O3 phase fraction which may contribute to higher conductivity and give a positive EC result.