Monolayer‐to‐Multilayer Dimensionality Reconstruction in a Hybrid Perovskite for Exploring the Bulk Photovoltaic Effect Enables Passive X‐ray Detection

Halide hybrid perovskites are attracting considerable attention as highly promising candidates for directly sensing X-ray radiation, but it is challenging to realize passive X-ray detection without an external power supply. However, the bulk photovoltaic effect (BPVE) in ferroelectrics promotes the independent separation of photoexcited carriers. Herein, by dimensionality reconstruction of a pure-two-dimensional (P-2D) monolayered perovskite (CH₃ OC₃ H₉ N)₂ PbBr₄ , we obtained a quasi-two-dimensional (Q-2D) ferroelectric (CH₃ OC₃ H₉ N)₂ CsPb₂ Br₇ . Converting P-2D into Q-2D perovskite stimulates a significant BPVE associated with robust ferroelectricity, as well as an enhanced mobility lifetime product. These features show the potential of the first passive X-ray detector based on ferroelectrics with an impressive sensitivity up to 410 μC Gy^-1 cm^-2 at zero bias, which is even superior to the value of the state-of-the-art α-Se detector operated at relatively high bias.