The influence of crystallinity on the electrochromic properties and durability of NiO thin films

NiO films are prepared by sol-gel method. With the increasing of annealing temperature, the change from the amorphous to the crystalline nature of the NiO films is observed. Amorphous NiO films have higher electrochromic activity as well as poor reversibility. However, higher crystalline film annealed at 400 °C leads to better reversibility with lower optical modulation. The NiO film annealed at 350 °C exhibits noticeable electrochromic performance, such as the highest observed optical modulation of 50.7% at 550 nm, long-term durability, high coloration efficiency (71.4 cm2 C−1) and excellent reversibility (Qex/Qin = 92.3%).