All solid-state solar cells based on CH3NH3PbI3-sensitized TiO2 nanotube arrays

TiO₂ nanotube arrays (TiO₂ NTAs) were firstly used as photoanode in methylammonium lead iodide (CH₃NH₃PbI₃) perovskite/TiO₂ NTAs heterojunction solar cell, where CH₃NH₃PbI₃ functions as both light absorber and hole conductor. The composition, structure and photoelectrochemical properties of the as-prepared samples were characterized by x-ray diffractometer (XRD), field-emission scanning electron microscope (FE-SEM), ultraviolet-visible (UV-vis) spectrophotometer and electrochemical workstation. The results indicate that the as-prepared CH₃NH₃PbI₃ belongs to the cubic crystal system, and TiO₂ NTAs sensitized by 0.3 M CH₃NH₃I and PbI₂ exhibit the best photoelectrochemical properties with an open-circuit voltage of 0.422 V and a short-circuit current density of 173.4 μA cm^-2. The EIS result shows that the extremely large resistance at CH₃NH₃PbI₃/FTO interface contributes to the low current density of the perovskite solar cell.