Amorphous Metal Oxide Blocking Layers for Highly Efficient Low-Temperature Brookite TiO2-Based Perovskite Solar Cells

A fully low-temperature-processed perovskite solar cell was fabricated with an ultrathin amorphous TiO x hole-blocking layer in combination with brookite TiO 2 prepared at temperature <150 °C. Structured with TiO x /brookite TiO 2 bilayer electron collector, the perovskite solar cells exhibit high efficiency up to 21.6% being supported by high open-circuit voltage and fill factor up to 1.18 V and 0.83, respectively. Compared to SnO x hole-blocking layer, TiO x has better electron band alignment with brookite TiO 2 and hence, results in higher efficiency.