Energy-Level Alignment at the Interface of Graphene Fluoride and Boron Nitride Monolayers: An Investigation by Many-Body Perturbation Theory

Abstract

Energy-level alignment at interfaces is important for understanding and optimizing optoelectronic and photocatalytic properties. In this work, we study the level alignment at the interface between graphene fluoride and boron nitride monolayers. These two-dimensional (2D) semiconductors are representative wide-bandgap components for van der Waals (vdW) heterostructures. We perform a systematic study on the structural and electronic properties of their interface, by using density functional theory and the <i>G</i>₀<i>W</i>₀ method of many-body perturbation theory. We adopt this interface as a prototypical system to investigate the impact of polarization effects on band gap and level alignment. We find a small but still notable polarization-induced reduction of the materials’ band gap by 250 meV that we interpret and analyze in terms of an image-potential model. Such effects stem from nonlocal correlations between electrons and cannot be captured by semilocal or standard hybrid density functionals. Our work provides a lower limit of band-gap renormalization in 2D systems caused by polarization effects, and demonstrates the importance of many-body perturbation theory for a reliable prediction of energy-level alignment in 2D vdW heterojunctions