An Unprecedented Biaxial Trilayered Hybrid Perovskite Ferroelectric with Directionally Tunable Photovoltaic Effects

Multiaxial molecular ferroelectrics, in which multiple-directional switching of spontaneous polarization creates diverse properties, have shown many intriguing advantages, making them indispensable complements to conventional inorganic oxides. Despite recent blooming advances, multi­axial molecular ferro­electric with bulk photo­voltaic effects still remains a huge blank. Herein, we report a biaxial lead halide ferro­electric, EA4Pb3Br10 (1, EA = ethyl­ammonium), which adopts the unique trilayered perovskite motif with a high Curie temperature of ∼384 K. Particularly, for 1, the distinct symmetry breaking with 4/mmm­Fmm2 species leads to the emergence of four equivalent polarization directions in the ferroelectric phase. Based on its biaxial nature, the bulk photo­voltaic effect of 1 can be facilely tuned between such multiple directions through electric poling. As far as we know, this is the first report on biaxial hybrid perovskite ferro­electric showing directionally tunable photo­voltaic activity. This work provides an avenue to control the bulk physical properties of multi­axial molecular ferro­electrics, and highlights their potential for further applications in the field of smart devices.