Predictive and Tractable GW Approach for Energy Level Alignment at Organic-Inorganic Interfaces with Significant Charge Transfer*

The energy level alignment (ELA) at organic-inorganic interfaces is critical for determining charge injection barriers in organic and molecular electronic devices. Many-body perturbation theory in the GW approximation enables the quantitative prediction of ELA in many systems, but can be computationally challenging for large interfaces. We have recently developed an approach [1] to perform GW calculations on large interface systems, which involves the eXpansion of the polarizability (chi) matrix from a unit cell to the supercell, the Addition of chi from the two subsystems, and the use of wavefunctions from the Full interface to compute the self-energies. This XAF-GW method has been shown to work even in the presence of interface hybridization to form bonding and anti-bonding orbitals. Here, we show that the XAF-GW method fails in some cases with significant interface charge transfer. We modify the XAF-GW approach to specifically account for charge transfer effects, and obtain good agreement between the modified XAF-GW method and a regular full GW calculation for F4TCNQ on bilayer graphene. We further discuss the application of our new approach to other experimentally relevant systems.

[1] J. Chem. Theory Comput. 15, 3824 (2019)