Application of 1/f current noise for quality and age monitoring of electrochromic devices

This is a continuation of an earlier study on 1/f noise in electrochromic (EC) devices undergoing discharge via a resistor. The EC devices comprised films of W oxide and Ni–V oxide joined by a polymer electrolyte, and with this three-layer stack positioned between transparent conducting In2O3:Sn films backed by polyester foils. We also investigated “symmetrical” devices with two identical films of W oxide or Ni–V oxide. The power spectral density Si at fixed frequency scaled with current (I) as Si∼I2. Color/bleach cycling for about 2500 times degraded the optical properties and homogeneity of the EC devices and increased the 1/f noise intensity by a factor of four, which confirms the earlier assumption that 1/f noise has a good potential to serve as quality and aging assessment for EC devices. Studies of “symmetrical” devices proved that the noise was mainly associated with the Ni oxide, and measurements on individual parts of an EC device indicated that the 1/f noise originated from localized areas.