Fast switching thermally treated nickel-tungsten oxide thin films for energy efficient smart windows

초록

Anodic electrochromic (EC) materials like nickel oxide are vital as counter electrodes for smart window applications due to their distinctive optical characteristics during charge intercalation and deintercalation. The current research aims to explore the influence of substrate temperature (ST) on the electrochromic efficiency of RF sputtered nickel- tungsten oxide (NW) against room temperature (RT) fabricated NW films. Low temperature prepared films showed amorphous nature while crystallization commenced at high temperature. Surface roughness increased with ST. Nickel vacancies decreased with increasing ST. The grain size of the film increased with increasing substrate temperature. Favourable columnar nano structural morphology is observed. Raman analysis affirmed the existence of nickel defects. We discovered that low-temperature deposition (150 degrees C) enhanced the optical modulation to 65 % with the rapid switching speed of 0.89 s for bleaching and 1.0 s for colouring without permanent structural degradation. The advantageous amorphous structure, along with adequate nickel vacancies, facilitates the unobstructed rapid intercalation and de-intercalation of Li-ions, hence enhancing the device's efficiency. The study findings indicate that the prepared nickel tungsten oxide film is appropriate to be employed for the counter electrode in energy-efficient smart windows.

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