Liquid Crystal Molecule as “Binding Agent” Enables Superior Stable Perovskite Solar Cells with High Fill Factor

Hybrid perovskites have rapidly emerged as highly promising optoelectronic materials for perovskite solar cells (PSCs), whereas solution‐processed perovskite films usually contain a large amount of grain‐boundary network, which is unbeneficial for efficient film function, including charge transport and environmental stability. Herein, a liquid crystal (LC) molecule is first used as a “binding agent” to connect grains and fill grain boundaries of perovskite. The LC molecule (4′‐heptyl‐4‐biphenylcarbonitrile) interacts with PbI 2 to control the crystal orientation for fine and oriented perovskite grains, which accelerates electron transport and enhances environmental stability. Consequently, compared with the pristine devices, the power conversion efficiency of the LC‐based device increases from 17.14% to 20.19% with a high fill factor (over 80%). Remarkably, the LC‐based PSCs retain 92% of their initial efficiency at 25 °C, and a relative humidity of 70% after 500 h, whereas the control samples are almost degraded completely under the same conditions.