The main goal of this bilateral collaboration between the Ruđer Bošković Institute (RBI), Croatia and the Institute for Chemistry and Technology of Materials (ICTM), Graz University of Technology, Austria is to investigate perovskite solar cells based on titanium dioxide nanotube arrays and to optimize their properties. Perovskite solar cells are currently in the focus of international research as they combine high efficiency with the potential to be a real low cost solar cell technology. In this research project, defined TiO₂ nanotube arrays will be introduced as electron transport layer in this type of solar cells. The RBI group will focus on the development of these TiO₂ nanotube arrays by electrochemical anodization of thin titanium films deposited by magnetron sputtering on a transparent conductive oxide. Structural and electrical characterization of the obtained layers by scanning and transmission electron microscopy as well as X-ray diffraction and Raman spectroscopy will be done at RBI. Structural characterization, in particular, grazing incidence small and wide angle X-ray scattering of the nanotube arrays will be done in collaboration with the SAXS beamline at the synchrotron Elettra in Trieste. The obtained TiO₂ nanotube arrays will be used by ICTM as structured electron transport layer in solution processed perovskite solar cells via infiltration of the perovskite precursor solution into the nanotube arrays and the conversion of the precursors into the lead halide perovskite. The structural, morphological and optoelectronic properties of the formed heterojunctions will be thoroughly characterized and in a final step, complete solar cells will be prepared and optimized. The solar cells will be tested by recording current density/voltage curves under standard testing conditions (dark and illuminated) and by external quantum efficiency spectra. It is expected that the photocurrent and power conversion efficiencies of the devices will be significantly improved by the introduction of the TiO₂ nanotube arrays, which will lead to an improved charge extraction and a reduced recombination in the absorber layer.