Unusual bendable soft molecule‐based ferroelectric crystals enabling the flexible photo‐pyroelectric detection

Abstract Soft molecule‐based ferroelectrics with unique structural flexibility hold a promise for versatile applications of non‐volatile memory, imaging and photovoltaic devices. Except for few polymers (e.g., polyvinylidene fluoride, PVDF), it is challenging to exploit soft ferroelectric crystals toward free‐standing flexible photoactive devices. We here report a multiaxial soft molecule‐based ferroelectric, ( n‐ PA) 2 PbCl 4 ( 1 , where n‐ PA + is n ‐pentylammonium), of which spontaneous polarization can be reversibly switched in both crystal and powder forms. Strikingly, single crystals of 1 have unusual structural flexibility and bendability, achieving the self‐standing bending with a bending radius of ~0.22 mm. Besides, the pyroelectric activities are also preserved for these single crystals after several bending cycles. Further, the bendable crystal‐based photodetector of 1 allows broadband photoactivities via the photo‐pyroelectric effect, covering a wide range from 405 to 940 nm spectral region, breaking through the limit of optical absorption bandgap. As the first study of bendable free‐standing photo‐pyroelectric detectors in ferroelectric crystals, our work sheds light on the assembly of flexible smart photoelectric devices. image