Secondary Hydrothermally Processed Engineered Titanium Dioxide Nanostructures for Efficient Perovskite Solar Cells

A secondary hydrothermal process was used to synthesize exotic hollow nanostructures of rutile TiO2 as an electron-transport layer for perovskite solar cells. The prepared nanostructures were used in combination with methylammonium lead iodide (MAPbI(3)) perovskite, and their photovoltaic properties were studied. This core-shell architecture of a perovskite enveloped by TiO2 provides an enhanced surface area, better contact with the perovskite because of the larger adsorption area, and effective light penetration. Our results revealed that the hollow nanoflowers exhibit a photocurrent density of 21.05 mAcm(-2), an open-circuit voltage of 0.916 V, and a fill factor of 0.66, which leads to a power conversion efficiency of 12.72%. These results were also verified by electrochemical impedance spectroscopy and time-resolved photoluminescence spectroscopy. Furthermore, the effect of the wetting time was studied, and our results revealed that a minimum time of 100 s is required for good penetration of a MAPbI(3)/gamma-butyrolactone solution.