Monolayer-to-Multilayer Dimensionality Reconstruction in Hybrid Perovskite for Exploring 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 remains great challenge to realize passive X-ray detection without external power supply. Bulk photovoltaic effect (BPVE) in ferroelectrics promotes the independent separation of photoexcited carriers, which offer an unprecedented opportunity in this regard. Herein, by dimensionality reconstruction of a pure-two-dimensional (P-2D) monolayered perovskite (CH 3 OC 3 H 9 N) 2 PbBr 4 ( 1 ), we successfully obtained a quasi-two-dimensional (Q-2D) ferroelectric (CH 3 OC 3 H 9 N) 2 CsPb 2 Br 7  ( 2 ), which is composed of bilayered perovskites sheets of corner-sharing PbBr 6 octahedra. Emphatically, converting P-2D into Q-2D perovskite arouses a significant BPVE associated with robust ferroelectricity, as well as enhanced mobility lifetime product. These features promise the fabrication 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 much superior to the value of state-of-the-art α -Se detector operated at relatively high bias. Our work demonstrates vast perspectives for the application of the ferroelectric semiconductors for photovoltaic electronic devices.