2D NbOI2: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Abstract Exploring in‐plane anisotropic 2D materials is of great significance to the fundamental studies and further development of polarizationsensitive optoelectronics. Herein, chiral niobium oxide diiodide (NbOI 2 ) is introduced into the intriguing anisotropic 2D family with the experimental demonstration of anisotropic optical and electrical properties. 2D NbOI 2 crystals exhibit highly anisotropic dispersed band structures around the Fermi surface and strong in‐plane anisotropy of phonon vibrations owing to the different bonding modes of Nb atoms along the b ‐ and c ‐axes. Consequently, the anisotropic factors of optical absorbance and photoresponsivity in 2D NbOI 2 crystals reach up to 1.75 and 1.7, respectively. These anisotropic properties make 2D NbOI 2 an interesting platform for novel polarization‐sensitive optoelectronic applications.