Synthesis of oriented TiO2 nanocones with fast charge transfer for perovskite solar cells

Abstract One-dimensional (1D) rutile TiO 2 nanostructures on fluorine-doped tin oxide (FTO) substrates are interesting building blocks of solar cells, and they have been traditionally prepared under highly acidic conditions. In this article, a green, facile hydrothermal approach was exploited to grow oriented rutile TiO 2 nanocones on FTO under nearly neutral conditions in a high-control way. XRD, SEM, TEM, HRTEM, and Raman spectroscopy were used to characterize the nanocones, showing rutile phase with single-crystalline structure, and the length of nanocones can be tailored in the range of 700~1400 nm by varying the reaction durations. As building blocks of CH 3 NH 3 PbI 3 -based perovskite solar cells, 11.9% power conversion efficiency was achieved for the TiO 2 nanocone devices, which is significantly superior to the state-of-the-art efficiency for other 1D nanostructure counterparts (~10% for TiO 2 nanorods and 11% for ZnO nanorods, respectively). It was further revealed by time-resolved photoluminescence spectroscopy (TRPL) that electron transfer from CH 3 NH 3 PbI 3 to TiO 2 nanocones is significantly faster than to TiO 2 nanorods, an important factor to suppress charge recombination and improve device performance. These characteristics make nanocones to be a promising candidate as electron transport materials for photovoltaic devices.