Enhanced electrochromic performances and cycle stability of NiO-based thin films via Li–Ti co-doping prepared by sol–gel method

• Li–Ti co-doped NiO films were prepared by sol–gel process.
• Li–Ti co-doped NiO films exhibit good optical variation and cycle stability.
• Electrochromic devices combined organic PProDOT-Me2 and inorganic Li–Ti–NiO films.
• Electrochromic devices showed excellent optical modulation and high stability.

Nickel oxide (NiO) has great application prospects as a counter electrode in electrochromic devices, such as smart windows and displays. However, the cycle stability and electrochromic properties of pure NiO films are rather poor in lithium ion based non-aqueous electrolyte. To improve these properties, Li–Ti co-doped NiO films were prepared by sol–gel spin coating technique. Compared with undoped NiO films, Li and Ti doping deteriorate the symmetry of NiO cubic phase, increase lattice disorder and change the valence state of nickel in the films. The investigations of NiO-based films in LiClO4/PC electrolyte reveal enhancement of electrochromic properties and cycle stability with Li–Ti co-doping. Finally, electrochromic devices assembled with poly(3,4-(2,2-dimethylpropylenedioxy)thiophene) and Li–Ti–NiO films exhibit rapid color change within 1 s, excellent optical variation for about 56% at 580 nm and high stability up to 1,000,000 cycles.

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