Light-Ferroelectricity Interaction at the Nanoscale in 2D Layered Halide Perovskite

Two-dimensional (2D) layered metal halide perovskites have emerged with unique physical properties of anisotropic charge transport, excellent optical properties and spontaneous polarization (ferroelectricity) arising from non-centrosymmetric structures, which makes them suitable for multifunctional applications. Such ferroelectric perovskites also qualify as piezo- and pyroelectrics. Specifically, the intricate coupling of photoexcitation and the spontaneous polarization arising from ferro- and pyro-electricity significantly influences the photocurrent behaviour by creating localized electric field. Here, we have employed piezoresponse force microscopy (PFM) to investigate the coupling between light and polarized domains at the nanoscale in a lead-free 2D halide perovskite single crystal of fluorobenzylammonium copper(II) chloride ((3-FbaH)₂CuCl₄), with a non-centrosymmetric structure. This investigation leads to the conclusion of decrement of polarization under illumination, which is also related to the rise in temperature of the perovskite during illumination. However, the polarized domains recovered upon withdrawal of illumination and cooling of the crystal. By leveraging this three-way coupling of photoexcitation, temperature fluctuation and polarization, we have utilized the 2D halide perovskite in self-powered photodetection for UV and visible light. This mechanism gives rise to the possibility of simultaneous harvesting of light and stray heat using the 2D halide perovskites in photodetectors and thermal sensors.