Improvement of electrochromic performance of nickel oxide porous films by Sn doping

In order to alleviate some disadvantages such as slow switch speed, small light modulation, and poor cycle stability, which hinder the large-scale application of electrochromic (EC) materials, element doping has become one of important routes to improve their microstructure and performance. In this work, tin-doped nickel oxide (Sn-doped NiO) porous EC films were prepared, and the influence of Sn-doping amount on the microstructure and EC performance of NiO films was investigated by comparing with undoped NiO film. Based on the electrochemical tests and energy-band structure analyses, the influence mechanism of Sn doping was discussed. The results show that the Sn doping changed the surface energy of NiO nanoparticles, and then changed the microstructure, increased the diffusion rate of ions, and improved the light modulation of NiO films obviously. And the Sn doping reduced the interface barrier of FTO/NiO heterojunction, resulting into the rapid EC response. The Sn-doped NiO film with doping amount of 10.0 mol.% showed the best EC properties, including large light modulation (64.1% at 550 nm), short response time (0.4 s for bleaching time and 3.0 s for coloring time), high coloration efficiency (48.9 cm2 C−1), and long cycle life (30000 cycles), and its semiconductor type changed into n-type from the p-type of undoped NiO film.