Enhanced electrochromic performance on novel W@NiO doped composite electrode via pre-annealing

To improve the electrochromic properties of traditional sputtering NiO films, we prepare a novel W@NiO composite films depending on dual impact of doping and pre-annealing. The small quantity of doping tungsten is guaranteed by unique stacked targets sputtering mode. On this basis, different substrate temperature is set to obtain a series of samples. The obtained 200 °C W@NiO films show obvious improvement compared with room-temperature pure NiO films and literature results. Specially, the charge density can get ∼60 mC/cm 2 , the optical modulation can realize ∼83% at 550 nm, the coloration efficiency can up to 65.27 cm 2 /C at 550 nm, while the specific capacitance can achieve ∼30 mF/cm 2 . Additionally, the W@NiO-200 shows potential in prominent cyclic reversibility, rapid response time, prolonging cycle lifespan. This study provides a new strategy for preparation of high-quality electrochromic NiO films by sputtering technology. • Micro-doping of tungsten elements into nickel oxide films by target perforation. • Optimized W@NiO films have improved charge capacity, optical modulation and coloration efficiency. • Enhanced charge storage capacity (∼30 mF/cm 2 ) was realized by optimized W@NiO films.