Nanotube (NT) layers of TiO2 are important one-dimensional nanostructures for advanced applications. ZnO nanowire arrays prepared through electrochemical deposition with tuned morphological properties are converted into anatase TiO2 NTs by using a titanate solution adjusted to an ad hoc pH. The tubes are polycrystalline and their diameter and length can be tuned to obtain nanostructures of tailored dimensions. The layers are integrated in CH3 NH3 PbI3 perovskite solar cells (PSCs). Their morphology is optimized for maximum performance and is compared to mesoscopic TiO2 PSCs. As compared to the latter, the use of NTs improved the perovskite absorbance in the green-to-near-infrared solar spectral region. Moreover, it is shown that the surface treatment of the TiO2 NTs with TiCl4 optimizes the interface between the oxide and CH3 NH3 PbI3 , which leads to better charge injection between the perovskite layer and the TiO2 NTs. The current density-voltage curve hysteresis index is low for the best NT morphology and significantly increases with tube length and diameter.
Keywords: TiO2 nanotubes; electrochemical deposition; hybrid perovskites; hysteresis index; solar cells.
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