Photonic crystals based on titanium oxide are important for modern photonics and solar energy systems. In particular, bamboo-like nanotubes made of titanium dioxide increase the efficiency of solar cells sensitized by a dye [1]. The absence of a reproducible, scalable, and inexpensive technology for creating photonic crystals based on titanium dioxide hinders the practical use of such materials. In our group, an anodizing technique has been developed that allows one to accurately specify the morphology of porous films of anodic oxides of valve metals. The potential of the developed approach was demonstrated by the formation of photonic crystals obtained by the anodic oxidation of titanium [2]. As a result of changing the anodization voltage across the sinusoid in the range 40-60 V, depending on the charge density, nanotubes of anodic titanium oxide having constant outer diameter and inner diameter, periodically varying with a film thickness, were obtained. Varying the position of the photonic band gap in the entire visible spectral range was achieved by changing the charge density spent during each anodization cycle.
The work is supported by Russian Science Foundation (Grant № 17-73-10471).
[1] D. Kim, A. Ghicov, S.P. Albu, P.Shmuki. Bamboo-type TiO2 nanotubes: improved conversion efficiency in dye-sensitized solar cell // J. Am. Chem. Soc., 130 (2008), pp. 16454-16455. doi: 10.1021/ja805201v.
[2] N.A. Sapoletova, S.E. Kushnir, K.S. Napolskii. Anodic titanium oxide photonic crystals prepared by novel cyclic anodizing with voltage versus charge modulation // Electrochem. Commun., 91 (2018), pp. 5-9. doi: 10.1016/j.elecom.2018.04.018.