Inch‐Size Single Crystals of Lead‐Free Chiral Perovskites with Bulk Photovoltaic Effect for Stable Self‐Driven X‐Ray Detection

Abstract Lead halide perovskites have made great advance in direct X‐ray detection, however the presence of toxic lead and the requirement of high working voltages severely limit their applicability and operational stability. Thus, exploring “green” lead‐free hybrid perovskites capable of detecting X‐rays at zero bias is crucial but remains toughly challenging. Here, utilizing chiral R / S ‐1‐phenylpropylamine ( R / S ‐PPA) cations, a pair of 0D chiral‐polar perovskites, ( R / S ‐PPA) 2 BiI 5 ( 1 R / 1 S ) are constructed. Their intrinsic spontaneous electric polarization induces a large bulk photovoltage of 0.63 V, which acts as a driving force to separate and transport photogenerated carriers, thus endowing them with the capability of self‐driven detection. Consequently, self‐driven X‐ray detectors with a low detection limit of 270 nGy s −1 are successfully constructed based on high‐quality, inch‐sized single crystals of 1 R . Notably, they show suppressed baseline drift under the self‐driven mode, exhibiting superior operational stability. This study realizes self‐driven X‐ray detection in a single‐phase lead‐free hybrid perovskite by exploiting the intrinsic bulk photovoltaic effect, which sheds light on future explorations of lead‐free hybrid perovskites toward “green” self‐driven radiation detectors with high performance.