Two-Dimensional Hybrid Perovskite-Type Ferroelectric for Highly Polarization-Sensitive Shortwave Photodetection

Two-dimensional (2D) materials have been well developed for polarization-sensitive photodetection, while new 2D members used in shortwave region (>2.5 eV) still remain scarce. The family of 2D hybrid perovskite ferroelectrics, in which the coupling of spontaneous polarization ( P_s) and light benefits dissociation of photoinduced carriers, has shown great potential in this portfolio. Here, we report a new 2D hybrid perovskite ferroelectric, [CH₃(CH₂)₃NH₃]₂(CH₃NH₃)Pb₂Br₇ (1), which exhibits a superior P_s of 3.6 μC/cm² and a relatively wide bandgap (∼2.55 eV). The unique 2D perovskite motif results in an intrinsic anisotropy of optical absorption (the ratio α_c/α_a ≈ 1.9 at 405 nm), involving its polarization-sensitive activity. As expected, the strongest photoresponses were observed along the c-axis (i.e., parallel to P_s), along with a large dichroism ratio ( I_ph^c/ I_ph^a ≈ 2.0) and highly sensitive detectivity up to ∼10⁹ Jones. Further, crystal-device of 1 shows a fast responding rate (∼20 μs) and excellent antifatigued merits. As pioneering work, 1 is the first polarization-sensitive ferroelectric in the new branch of 2D hybrid perovskites. Such intriguing behaviors make 1 a potential candidate for the shortwave polarized-light detection, which also sheds light on new functionalities for future optoelectronic application of hybrid perovskites.