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

摘要

Electrochromic organomolybdenum oxide (MoO_xC_y) 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 °C). The MoO_xC_y films with modified surface morphology and compositions of varying oxygen contents are proven to offer noteworthy electrochromic performance. Porous surface of the MoO_xC_y film (398 nm thick) provides Li~+ ion diffusion coefficient value of 1.7 x 10~(-10) cm~2/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 MoO_xC_y film offers light modulation with transmittance variation of up to 63% and coloration efficiency of 36 cm~2/C at a wavelength of 800 nm for 200 cycles of Li~+ intercalation and de-intercalation. PECVD-synthesized MoO_xC_y thin films show promising electrochromic properties for applications in flexible electrochromic devices.