Tri‐functionalized Cation Assisted Crystallization of 2D Chiral&Polar Hybrid Lead Iodide Showing Bulk Photovoltaic Effect for Self‐Powered Circularly Polarized Light Detection

Abstract Chiral organic–inorganic hybrid metal halides (OIHMHs) are such a promising family of chiral semiconductors to directly sense circularly polarized light (CPL) due to inherent chiroptical activity, but face synthetic constraints due to a shortage of suitable chiral building blocks that generate chiral and 2D structures, which are a prerequisite for expected optoelectronic responses. Here, a halogen interaction assisted crystallization of a pair of chiral 2D OIHMHs, ( R / S ‐AMOL‐I) 2 PbI 4 ( 1 R / S ; AMOL‐I = 1‐amino‐4‐iodobutan‐2‐ol cation) is reported. In situ iodine substitution in the chiral cation forms halogen‐halogen bond, favoring crystallization of the chiral&polar 2D structure and efficient chirality transfer. The inherent polar structure of 1 S produces a significant bulk photovoltaic effect (0.48 V), which serves as a driving source for self‐powered CPL detection. When exposed to CPL, the fabricated single crystal‐based device shows a large response asymmetry factor (0.16) at a zero bias. Moreover, the prototypical device shows broadband photo‐responses in the wavelength range of 265–700 nm, which is attributed to the polar structure‐aroused pyroelectric effect. This study evidences how the substituted halogen group in the organic cation leads to the desired 2D chiral&polar OIHMHs which enable high‐sensitive self‐powered broadband CPL detection, offering new insights for the design of functional chiral semiconductors.