Low-Temperature TiO_x Compact Layer for Planar Heterojunction Perovskite Solar Cells

Here, we demonstrate an effective low-temperature approach to fabricate a uniform and pinhole-free compact TiO₂ layer for enhancing photovoltaic performance of perovskite solar cells. TiCl₄ was used to modify TiO₂ for efficient charge generation and significantly reduced recombination loss. We found that a TiO₂ layer with an appropriate TiCl₄ treatment possesses a smooth surface with full coverage of the conductive electrode. Further studies on charge carrier dynamics confirmed that the TiCl₄ treatment improves the contact of the TiO₂/perovskite interface, facilitating charge extraction and suppressing charge recombination. On the basis of the treatment, we improved the open circuit voltage from 1.01 V of the reference cell to 1.08 V, and achieved a power conversion efficiency of 16.4%.