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Multipodal and Multilayer TiO2 Nanotube Arrays: Hierarchical Structures for Energy Harvesting and Sensing

  • Arash Mohammadpour (a1), Samira Farsinezhad (a1), Ling-Hsuan Hsieh (a1) and Karthik Shankar (a1) (a2)


Our ability to fabricate multipodal and multilayer TiO2 nanotube arrays enables us to increase performance and functionality in light harvesting devices such as excitonic solar cells and photocatalysts. Using a combination of simulations and experiments, we show that multilayer nanotube arrays enable photon management in the active toward enhancing the absorption and utilization of incident light. We show that the simultaneous utilization of TiO2 nanotubes with large (∼450 nm) and small (∼80 nm) diameters in stacked multilayer films increased light absorption and photocurrent in solar cells. Such enhanced light absorption is particularly desirable in the near-infrared region of the solar spectrum in which most excitonic solar cells suffer from poor quantum efficiencies and for blue photons at the TiO2 band-edge where significant room exists for improvement of photocatalytic quantum yields. Under AM 1.5 one sun illumination, multilayer nanotube arrays afforded us an approximately 20% improvement in photocurrent over single layer nanotube array films of the same thickness for N-719 sensitized liquid junction solar cells. Also, the possibility of multipodal TiO2 nanotube growth with different electrolyte recipes is presented.



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