Compatible Ferroelectricity, Antiferroelectricity and Broadband Emission for a Multi-Functional 2D Organic-Inorganic Hybrid Perovskite

Two-dimensional (2D) organic-inorganic hybrid perovskites with multifunctional characteristics have potential applications in many fields, such as, solar cells, microlasers and light-emitting diodes (LEDs), etc. Here, a 2D organic-inorganic lead halide perovskite, [Br(CH₂)₃NH₃]₂PbBr₄ (BPA-PbBr₄, BPA = Br(CH₂)₃NH₃, 3-Bromopropylamine), is examined for its photophysical properties. Interestingly, BPA-PbBr₄ reveals five successive phase transitions with decreasing temperature, including successive paraelectric-ferroelectric-antiferroelectric phases. Besides, BPA-PbBr₄ displays ferroelectricity and antiferroelectricity throughout a wide temperature range (<376.4 K) with accompanying saturation polrization (P_s) values of 4.35 and 2.32 μC/cm², respectively, and energy storage efficiency of 28.2%, and also exhibits superior second harmonic generation (SHG) with maximum value accounts for 95 % of the standard KDP due to the great deformation of structure (3.2302*10^-4). In addition, the photoluminescence (PL) of the BPA-PbBr₄ exhibits abnormal red-shift and blue-shift in different phases due to a consequence of competition between electron-phonon interaction and the lattice expansion. Further, BPA-PbBr₄ reveals a broadband emission accompanied by bright white light at room temperature (293 K), which is supposed to be due to self-trapped excitons. In short, the versatility of BPA-PbBr₄ originates from molecular reorientation of dynamic organic cations, as well as significant structural distortion of PbBr₆ octahedra. This work paves an avenue to design new hybrid multifunctional perovskites for potential applications in the photoelectronic field.