The microstructure and energy-band structure coupling regulation of Ti-doped seed layer for the NiO electrochromic composite films

Abstract

Structure regulation and doping modification are important means to enhance the electrochemical and electrochromic performance of anode NiO electrochromic films. How to improve cycle stability is crucial for the application of NiO electrochromic films. In this work, we prepared Ti-doped seed layers with varying precise chemical stoichiometry ratios through the sol–gel spin coating method. Subsequently, NiO composite films were successfully fabricated on these seed layers through a simple hydrothermal process. Notably, among all the samples, the A 1/8 sample exhibits superior electrochromic performance, including a large optical modulation amplitude (69.61 % at 550 nm), faster response time (5.0 and 6.2 s), high coloring efficiency (33.87 cm²/C), and excellent cycle stability (3300 cycles). The seed layer plays a crucial role in preventing direct contact between the electrolyte and the electrode, inducing the growth of self-assembled structures, and enhancing adhesion between the film and the electrode. The Ti-doped seed layer can regulate the composite film microstructure and band structure, impacting the film electrochromic properties. In this work, we demonstrate that the cycle stability of the NiO composite films is improved through dual regulation of structure and doping. The A 1/8 sample exhibits superior cycle stability, attributed to the coupling effect of multi-channel nanostructure, and reduces interface barrier with FTO.