Low-Symmetry 2D Perovskite CaNb₂O₆ for Polarization-Sensitive UV Photodetection

Polarization-sensitive photodetection in ultraviolet (UV) range has demonstrated broad applications in both military and civilian fields. As the key component of polarized UV photodetectors, semiconducting materials with wide bandgaps and intrinsic low-symmetry are highly desired. Herein, perovskite calcium niobate (CaNb₂O₆) is re-introduced to the family of two-dimensional (2D) layered materials for UV-polarized photodetection. Using a simple vapor phase epitaxy growth process, CaNb₂O₆ nanosheets are successfully synthesized, which can be scaled down to monolayers with thickness of about 0.8 nm. The anisotropic structural, vibrational, and optical properties of CaNb₂O₆ are systematically investigated. Photodetectors based on 2D CaNb₂O₆ present a large dichroic ratio of 2.1 at 375 nm light irradiation, exceeding most of reported UV photodetectors, and the large anisotropic ratio also contributes to a high-resolution polarization imaging. This work demonstrates that the 2D CaNb₂O₆ has promising potential for developing next-generation polarized UV detecting and imaging technology.