Controllable Preparation of Rutile TiO₂ Nanorod Array for Enhanced Photovoltaic Performance of Perovskite Solar Cells

A vertically oriented rutile TiO2 nanorod (NR) array, as an efficient electron transport layer (ETL), has been used in the perovskite solar cells (PSCs), and its microstructure has a great impact on the corresponding photovoltaic conversion efficiency (PCE). Here we employ a facile control strategy to modulate the microstructures of rutile TiO2 NR arrays hydrothermally grown on the fluorine tin oxide (FTO) glass from a water–HCl solution of titanium n-butoxide (TBOT). It was found that introducing commercial TiO2 nanoparticles (P25, Degussa) into the hydrothermal reaction system can efficiently slow down the growth rate of rutile TiO2 NRs, thus causing the controllable preparation of an NR array on the FTO substrate. The device fabricated with an optimized NR array derived from the hydrothermal reaction solution containing P25 exhibits an improvement of 26.5% in PCE compared with the device fabricated with the NR array from the hydrothermal solution without P25, which is mainly attributed to the reduced charge recombination and the enhanced fill factor stemming from the better contact at the NRs array/perovskite interface. This successful finding demonstrates that the introduction of TiO2 nanoparticles into the hydrothermal reaction solution of TBOT slows down the growth rate and the electron recombination process of the rutile TiO2 NRs array, and thus acts as a facile control strategy for improving the photovoltaic performance of the rutile TiO2 NRs array film-based PSCs.