Temperature dependence of the electrochromic properties of complementary NiO//WO3 based devices

The influence of the cycling temperature, up to 80 degrees C and down to -10 degrees C, on the performances of the electrochromic device ITO/NiO/electrolyte/WO3/ITO (NiO//WO3) and symmetrical devices ITO/LixWO(3) (colored)/ electrolyte/WO3 (bleached)/ITO (WO3//WO3), ITO/LiyNiO (colored)/electrolyte/NiO (bleached)/ITO (NiO// NiO) is studied. At 60 degrees C, the charge capacity of NiO//WO3 device increases from 2.59 mC/cm(2) to 3.22 mC/cm2 compared with that at room temperature, and the chromaticity difference between colored and bleached state could reach similar to 36. When working at 80 degrees C, although the charge capacity of the device reaches 4.20 mC/cm(2), the poor reversibility of the reaction of the NiO layer results in the irreversible attenuation of the device performance. Interestingly, after degradation associated with cycling at low temperature (56% capacity decrease at 10 degrees C), a recovery of the electrochromic properties at room temperature is observed. It can be considered that the low temperature within 10 degrees C basically has no non-recoverable damage to the devices. During the bleaching and coloring process, NiO layer mainly presents pseudocapacitance, while WO3 layer exhibits the ion diffusion control behavior (i.e, (de)insertion mechanism). A comparison with symmetrical devices, WO3//WO3 and NiO//NiO points out that performance change of complementary device NiO//WO3 is mainly affected by the cathodically colored electrochromic layer WO3.

Automated summary

The study found that cycling temperature affects the performance of the electrochromic devices, and cycling at low temperatures as low as -10 degrees Celsius can even lead to some performance recovery.