Designing a novel family of 2D B12X2 (X = N, P, As) based on B12 superatoms for optoelectronic application

Among two-dimensional (2D) materials, boron-based materials have garnered significant attention due to their unique electronic structures, multi-center bonding characteristics, and structural tunability, showcasing immense development potential. In this study, based on first-principles calculations, we successfully designed six highly stable 2D borides by cleaving bulk B 12 X 2 (X = N, P, As) crystals along different crystal planes. These include three hexagonal phases ( h -B 12 X 2 ) and three orthorhombic phases ( o -B 12 X 2 ). Electronic structure calculations revealed that, except for o -B 12 N 2 , the other five are narrow-bandgap semiconductors with bandgap ranging from 0.995 to 1.423 eV. Calculations of carrier mobility demonstrated that these materials exhibit excellent electron mobility, with o -B 12 P 2 achieving an exceptionally high electron mobility of 6.9 × 10 4 cm 2 V −1 s −1 . Notably, o -B 12 N 2 simultaneously exhibits axial negative Poisson's ratio characteristics (−0.025/-0.045), Dirac semimetallic properties (with a Fermi velocity as high as 2.149 × 10 5 m/s), and a high infrared light absorption coefficient (∼20%). This study not only confirms that 2D B 12 X 2 are promising candidates for high-performance 2D optoelectronic materials but also provides theoretical support and a design paradigm for research on similar 2D borides.