Mechanical, electronic and photocatalytic properties of binary Ge-based materials GeX2 (X = B, C, N) with a pentagonal structure

Abstract

Researchers have increasingly focused on 2D pentagonal materials due to their unique structure and physical properties. Here, based on density functional theory (DFT), we predicted novel 2D pentagonal binary compounds based on Ge with a low-symmetry puckered structure, namely penta-GeX₂ (X = B, C, N). The high stability (thermodynamic stability, dynamic stability and mechanical stability) and large critical strain make them attractive candidates for experimental implementation. Among them, the penta-GeB₂ monolayer is metallic, while others are indirect band gap semiconductors, whose band gaps can be adjusted under applied strain (−8% to 8%). Interestingly, the penta-GeX₂ (X = B, C, N) monolayer possesses highly anisotropic mechanical and electronic properties that make it suitable for next-generation anisotropic multifunctional devices. Moreover, the penta-GeC₂ monolayer exhibits an outstanding visible-ultraviolet optical absorption (∼10⁵ cm⁻¹) and remarkable hole mobility (∼1242 cm² V⁻¹ s⁻¹), making it a promising photocatalyst. This study predicted novel 2D Ge-based pentagonal binary compounds, broadened the territory of pentagonal structure families, and identified their potential application in anisotropic optoelectronics and photocatalysis.