“…Among the metal oxides, NiO with its high chemical stability, low cost, and high optical contrast is a promising EC anode. 23 Moreover, NiO is used as an anodic complementary layer to the cathodic WO 3 layer in EC devices yielding a complete opaque state of windows. It has been shown that the EC performance of NiO depends on thickness, 24 porosity, 25 annealing, 26 etc.…”