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. 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%.
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) or doping with donors (e.g. Nb, Ta),[8,9] or by maximizing dye loading by hierarchical photo-anode designs.
Some literature citations:
 K. Lee, A. Mazare, P. Schmuki, Chem. Rev. 2014, 114, 9385.
 P. Roy, S. Berger, P. Schmuki, Angew. Chemie Int. Ed. 2011, 50, 2904.
 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.
 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.
 F. Mohammadpour, M. Moradi, K. Lee, G. Cha, S. So, A. Kahnt, D. M. Guldi, M. Altomare, P. Schmuki, Chem. Commun. 2015, 51, 1631.
 F. Mohammadpour, M. Moradi, G. Cha, S. So, K. Lee, M. Altomare, P. Schmuki, ChemElectroChem 2015, 2, 204.
 S. So, I. Hwang, J. Yoo, S. Mohajernia, M. Mačković, E. Spiecker, G. Cha, A. Mazare, P. Schmuki, Adv. Energy Mater. 2018, 8, 1800981.
 M. Yang, D. Kim, H. Jha, K. Lee, J. Paul, P. Schmuki, Chem. Commun. 2011, 47, 2032.
 K. Lee, P. Schmuki, Electrochem. commun. 2012, 25, 11.
 S. So, I. Hwang, P. Schmuki, Energy Environ. Sci. 2015, 8, 849.