Room-Temperature Processing of TiOx Electron Transporting Layer for Perovskite Solar Cells

In order to realize high-throughput roll-to-roll manufacturing of flexible perovskite solar cells, low-temperature processing of all device components must be realized. However, the most commonly used electron transporting layer in high-performance perovskite solar cells is based on TiO2 thin films processed at high temperature (>450 degrees C). Here, we demonstrate room temperature solution processing of the TiOx layer that performs as well as the high temperature TiO2 layer in perovskite solar cells, as evidenced by a champion solar cell efficiency of 16.3%. Using optical spectroscopy, electrical measurements, and X-ray diffraction, we show that the room-temperature processed TiOx is amorphous with organic residues, and yet its optical and electrical properties are on par with the high-temperature TiO2. Flexible perovskite solar cells that employ a room-temperature TiOx layer with a power conversion efficiency of 14.3% are demonstrated.