Boosting the electrochromic performance of TiO2 nanowire film via successively evolving surface structure

• Published in: Science China. Chemistry 2021-05, Vol.64 (5), p.745-752
• Main Authors: Dai, Baohu, Wu, Changzheng, Xie, Yi
• Format: Article
• Language: English
• Subjects: Amorphization; Atomic layer epitaxy; Bleaching; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Color; Diffusion coefficient; Efficiency; Electrochromism; Evolution; Ion diffusion; Nanowires; Optical density; Order disorder; Performance enhancement; Surface structure; Titanium; Titanium dioxide; Transition metal oxides
• ISSN: 1674-7291; 1869-1870
• DOI: 10.1007/s11426-020-9941-4

Electrochromic transition metal oxides (ETMOs) are useful in energy saving devices and smart indicators. Among these ETMO candidates, titanium dioxide (TiO 2 ) is intriguing for its abundance and environmental safety, but the low color efficiency and slow coloring rate are still barricades to promote its electrochromic application. Herein, we demonstrate an amorphization strategy to comprehensively enhance the performance of TiO 2 nanowire film (TNF) via atomic layer deposition (ALD) of an additional TiO 2 conformal layer onto TNF surface, of which the layer structure evolves successively from ordered to disordered, achieving tunable electrochromism by controlling ALD cycles. Besides the remarkable increment of charging efficiency by ∼35% and color efficiency by ∼40%, bleached transmittance rectified optical density (BTR density) and ion diffusion coefficient are boosted by ∼90% and over 15 times, respectively for TNF deposited with 150 cycles. A large number of self-doped Ti 3+ defects and hydroxyl units together with order-disorder interconnections in the ALD TiO 2 layer are responsible for the performance enhancement. The concept for successively evolving surface structure shares the feasibility of upgrading conventional ETMOs as well as designing new electrochromic materials.