Studies on covalent functionalization of single layer black phosphorus from GW calculations based on the many body perturbation theory

The major challenge of black phosphorus (BP) is its fast-oxidative degradation in air. Organic covalent chemical modification of BP flakes could suppress the chemical degradation. Here we focus on the effects of covalent chemical modification on the electronic structures of single layer BP. We employed the state-of-the-art first principles GW method, which is based on the many body green functions, to study the covalent modification of single layer BP by forming P-C bonds. Our results show that the functional group chemisorbed at perfect lattice site results in deep in-gap state, which may deteriorate its performance, while the P-C bonds forming at single vacancies are electrically inactive. In addition, our results show that functional groups at low concentration would be preferably chemisorbed at single vacancies. At high concentration, functional groups would lead to the breaking of P-P bonds, and hence, oxygen impurity will easily insert in the interstitial position. Finally, we propose that functional groups at low concentration would protect BP from deterioration, and at high concentrations, functional groups would accelerate the deterioration of BP performance.