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

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)₂PbCl₄ (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.