Solar cells

TiO2 nanotubular structures of optimized morphology (tube width and length, aspect-ratio)[1,2] proved to be excellent scaffolds for solar cell devices in various configurations.
Nanotube arrays were used, for example, to design interdigitated electron collector scaffold-light absorber assemblies based e.g. on methylammonium lead halide (MAPI) perovskites.[3] Besides nanotubular structures, we fabricated efficient perovskite solar cells with other 1D oxide arrays such as single crystalline TiO2 rutile nanorods synthesized via hydrothermal methods. A combination of different surface modification strategies, aiming at engineering the oxide/perovskite interface, was found to suppress charge recombination and improve interfacial charge transfer, thereby enabling cell efficiencies as high as > 19%.[4]
Oxide nanotubes were used also as photo-anode architectures in dye-sensitized (Graetzel type) solar cells (DSSCs).[5,6] Enhanced cell efficiencies (e.g. > 10%) were reached by improving charge transport in the oxide nanotubes by controlled thermal treatments (temperature, ramping rate, atmosphere)[7] or doping with donors (e.g. Nb, Ta),[8,9] or by maximizing dye loading by hierarchical photo-anode designs.[10]

Some literature citations:
[1] K. Lee, A. Mazare, P. Schmuki, Chem. Rev. 2014, 114, 9385.
[2] P. Roy, S. Berger, P. Schmuki, Angew. Chemie Int. Ed. 2011, 50, 2904.
[3] R. Salazar, M. Altomare, K. Lee, J. Tripathy, R. Kirchgeorg, N. T. Nguyen, M. Mokhtar, A. Alshehri, S. A. Al-Thabaiti, P. Schmuki, ChemElectroChem 2015, 2, 824.
[4] F. Shahvaranfard, M. Altomare, Y. Hou, S. Hejazi, W. Meng, B. Osuagwu, N. Li, C. J. Brabec, P. Schmuki, Adv. Funct. Mater. 2020, 30, 1909738.
[5] F. Mohammadpour, M. Moradi, K. Lee, G. Cha, S. So, A. Kahnt, D. M. Guldi, M. Altomare, P. Schmuki, Chem. Commun. 2015, 51, 1631.
[6] F. Mohammadpour, M. Moradi, G. Cha, S. So, K. Lee, M. Altomare, P. Schmuki, ChemElectroChem 2015, 2, 204.
[7] S. So, I. Hwang, J. Yoo, S. Mohajernia, M. Mačković, E. Spiecker, G. Cha, A. Mazare, P. Schmuki, Adv. Energy Mater. 2018, 8, 1800981.
[8] M. Yang, D. Kim, H. Jha, K. Lee, J. Paul, P. Schmuki, Chem. Commun. 2011, 47, 2032.
[9] K. Lee, P. Schmuki, Electrochem. commun. 2012, 25, 11.
[10] S. So, I. Hwang, P. Schmuki, Energy Environ. Sci. 2015, 8, 849.