Electrochromic smart windows benefits include among others energy efficiency and indoor comfort [1]. However, on a daily use, the temperature is a key factor that may affect the device durability. Among materials, WO₃ and NiO thin films are often combined for the realization of electrochromic devices with high color efficiency, short switching time, low cost and good stability [2]. Nevertheless, in the literature, the influence of the temperature is scarcely addressed [3].

In this study, the influence of temperature between 80 °C and -40 °C on the EC properties of WO₃ and NiO based devices either in complementary WO₃/electrolyte/NiO or in symmetrical structure WO₃/electrolyte/WO₃ and NiO/electrolyte/NiO, is discussed. WO₃ and NiO thin films were deposited on ITO coated glasses (~25Ω/□) by reactive direct current (DC) magnetron sputtering. Laminated devices were prepared using lithium based composite polymer gel. The electrochromic properties of complementary devices and symmetrical devices were characterized in temperatures, both after storage for few hours and upon cycling. As a general trend, the device capacity decreases in low temperature and increase in high temperature, while intermediate cycling at room temperature shows slight degradation above 45 °C, and good recovery after cycling at low temperature (T < 0 °C). Interestingly, symmetrical devices behave differently in respect of NiO or WO₃nature. In this presentation, further investigations on the evolution of the EC behavior with temperature will be discussed.

References

[1] C. G. Granqvist, Electrochromics for smart windows: Oxide-based thin films and devices, Thin Solid Films 564 (2014) 1–38

[2] H. Moulki, D.H. Park, B.K. Min, H. Kwon, S.J. Hwang, J.H. Choy, T. Toupance, G. Campet, A. Rougier, Electrochimica Acta, 2012, 74, 46

[3] M. Da Rocha, A. Rougier, Electrochromism of non-stoichiometric NiO thin film: as single layer and in full device, Applied Physics A, 2016, 122:370