Investigation of the growth of nickel oxide films using atomic layer deposition of NiCp2 and O3 for electrochromic applications

The development of smart electrochromic windows capable of adjusting the transmission of optical radiation has the potential to reduce peak energy consumption for the cooling and heating of buildings. Nevertheless, this technology still requires further development and the implementation of new approaches to mass production. For this purpose, a novel approach to obtain electrochromic material by the atomic layer deposition (ALD) method has been demonstrated in this research. This study explores the ALD method for NiO synthesis using bis(cyclopentadienyl) nickel (II) and ozone by comparing two evaporator types: “Bubbler” and “Vapor.” The “Bubbler type” showed better performance, with a growth rate of 0.025 nm/cycle (0.019 nm/cycle for “Vapor type”) and lower non-uniformity (19 %) at 250 °C. Optimal deposition occurred between 225 and 275 °C, yielding a stable growth rate of 0.024–0.025 nm/cycle. The films consisted mainly of NiO crystals (Fm3m) with traces of Ni(OH)₂/NiOOH. A 15 nm thick NiO layer on porous ITO demonstrated promising electrochromic properties: 37 % transmittance modulation, 42.6 cm²/C colouring efficiency, and response times of 3.6 s (colouring) and 5.4 s (bleaching). These results highlight the potential for scalable ALD-based production of high-performance electrochromic materials.