Laboratoire de Chimie et Physique Quantiques - UMR5626

The GW and Bethe-Salpeter formalisms are popular approaches for calculating charged and neutral excitations in condensed matter systems, belonging to the family of many-body Green’s function perturbation theories. Developed originally for the electron gas and applied to inor- ganic solids at the ab initio level since the mid-80s, applications to organic systems are bloom- ing, benefiting in particular from recent implementations using standard Gaussian basis sets and resolution-of-identity techniques allowing direct comparison with other quantum chemistry techniques. After reviewing some of the merits of the GW and BSE formalisms for gaz phase molecules, we present the merging of the GW and Bethe-Salpeter equation (BSE) formalisms with continuous or discrete polarisable models1−3 allowing the study of the electronic and op- tical properties of molecular systems embedded in complex electrostatic and dielectric environ- ments. We show in particular that the absolute position with respect to the vacuum level of the band edges of organic semiconductors can be obtained with accuracy both in the bulk and at the surface.4 We further demonstrate that the combination of BSE with polarisable models allows to account simultaneously for "state specific" and "linear response" effects, solving a long stand- ing problem faced by time-dependent DFT calculations. As a first application, we discuss the mechanisms allowing to understand the doping mechanisms in organic semiconductors where donor/acceptor levels are in general very deep.5
(1) I. Duchemin, D. Jacquemin, X. Blase, J. Chem. Phys. 144, 164106 (2016).
(2) J. Li, G. D’Avino, I. Duchemin, D. Beljonne, X. Blase, J. Phys. Chem. Lett. 7, 2814 (2016). (3) I. Duchemin, C.A. Guido, D. Jacquemin, X. Blase, Chem. Sci., 9, 4430 (2018).
(4) J. Li, G. D’Avino, I. Duchemin, D. Beljonne, X. Blase, Phys. Rev. B 97, 035108 (2018). (5) J. Li, G. D’Avino, A. Pershin, D. Jacquemin, I. Duchemin, D. Beljonne, X. Blase, Phys. Rev. Materials 1, 025602 (2017).