Applications of Ba doped rutile TiO2 nanorod arrays in carbon-based all-inorganic perovskite solar cells

The electron transport layer (ETL) plays an important part in perovskite solar cell (PSC) devices. TiO2 nanorod arrays (TiO2 NAs) is widely used as ETL for perovskite solar cells because of its excellent energy level matching. Furthermore, TiO2 NAs provide the directed 1-D electron transmission channel. In this work, rutile TiO2 NAs synthesized by one-step hydrothermal method were used as the ETL of carbon-based perovskite solar cells to improve the performance. The interface between the ETL and perovskite was modified by barium acetate to reduce interface defects, non-radiative recombination and improve the electron transport rate. The perovskite film based on the Ba@TiO2 NAs exhibited larger grains and fewer grain boundaries, which was of positive significance for improving the power conversion efficiency (PCE) of devices. At the same time, we replaced the precious metal electrode and unstable organic hole transport layer (HTL) with carbon electrode, which reduces the manufacturing cost and improves the stability of the device. Finally, all inorganic HTL-free carbon-based perovskite solar cells based on Ba@TiO2 NAs showed a champion PCE of 10.74%, which is 14.74% higher than the control device.