Fast, Highly Stable, and Low-Bandgap 2D Halide Perovskite Photodetectors Based on Short-Chained Fluorinated Piperidinium as a Spacer.

Ruddlesden-Popper (RP) two-dimensional (2D) halide perovskite (HP), with attractive structural and optoelectronic properties, has shown great potential in optoelectrical devices. However, the relatively wide bandgap () and stability, which cause inferior efficiency, prevent its feasibility from further applications. To tackle these issues, for the first time, a novel fluorine-containing piperidinium spacer, (3-HCFCFCHOCH-PPH), abbreviated as (4FH-PPH), has been designed for the stable and efficient = 1 2D HPs.