Effects of oxygen addition on electrochromic properties in low temperature plasma-enhanced chemical vapor deposition-synthesized MoOxCy thin films for flexible electrochromic devices

Electrochromic organomolybdenum oxide (MoOxCy) films are deposited onto 60 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates by low temperature plasma-enhanced chemical vapor deposition (PECVD) using a precursor of molybdenum carbonyl vapor, which is carried by argon gas, mixed with oxygen gas and synthesized by radio frequency power at room temperature (23 oC). The MoOxCy films with modified surface morphology and compositions of varying oxygen contents are proven to offer noteworthy electrochromic performance. Porous surface of the MoOxCy film (398 nm thick) provides Li+ ion diffusion coefficient value of 1.7 x 10-10 cm2/s for Li+ de-intercalation at a potential scan rate of 2 mV/s. High x/y value at high surface composition of oxygen to carbon in the MoOxCy film offers light modulation with transmittance variation of up to 63% and coloration efficiency of 36 cm2/C at a wavelength of 800 nm for 200 cycles of Li+ intercalation and de-intercalation. PECVD-synthesized MoOxCy thin films show promising electrochromic properties for applications in flexible electrochromic devices.