Electrochromic properties of undoped and Ti-doped MoO3 converted from vertical nanowall MoS2 thin films

Using radio frequency magnetron sputtering (RFMS), the undoped and Ti-doped vertical nanowall structured MoS2 thin films were grown. In order to benefit from the chromic properties of the MoO3 and inherited surface/volume ratio of the vertical nanowall structures of the MoS2, these films thermally oxidized to α-MoO3 while retaining the morphology. Measurements of in-situ transmittance during the oxidation process revealed that the MoS2 samples with a highTi content oxidized more quickly. On the other hand, the presence of Ti has led to denser nanowall formations. Optical modulation (OM) in the visible region improved with increasing Ti concentration within the coloring potential range of -0.2 to -0.45 V, which are relatively low working voltages that indicate energy efficient electrochromic materials. The highest Ti-doped MoO3 (MTO40) and undoped (MBO) samples exhibit 52.2 % and 37.6 % OM at 700 nm (47.8 % and 25.7 %, respectively, at 550 nm) under -0.45 V applied potential. On the other hand, the coloring times for MBO, MTO20, MTO30, and MTO40 are 4.7, 4.1, 6.2, and 2.9 s, respectively, while the bleaching durations are 3.1, 1.4, 1.1, and 1.2 s for samples. These Ti-doped MoO3 electrochemical characteristics demonstrate the suitability of the proposed technique for device applications.