Thousand-atom ab initio calculations of excited states at organic/organic interfaces: toward first-principles investigations of charge photogeneration

Abstract

Electron and hole wave functions of low-lying and hybridized interfacial charge-transfer states across the pentacene/C60 interface.

Charge-transfer excited states in the donor/acceptor interface from large-scale GW calculations

“…The expression denotes that electron correlation and orbital relaxation within a target fragment are treated at the GW level, whereas the associated induced polarization energy of an entire system is computed at the static COHSEX level. We have shown that the static COHSEX can appropriately describe the solid-state effects on electronic states 9 and expect that the combined GW and static COHSEX approach can provide a reasonable approximation for a weakly interacting molecular system. The FMO-GW quasiparticle energy of the fragment is calculated in a perturbation manner as follows:…”

“…Therefore, we employed the atomic structure of the edge-on configuration of the PEN/C 60 bilayer heterojunction, which was prepared using molecular dynamics (MD) simulations. 9 respectively. The local interface structure is composed of 36 PEN and 15 C 60 molecules and thus contains 2196 atoms.…”

“…The PEN/C 60 bilayer heterojunction is one of the most prototypical organic solar cells; 52,53 the electronic structures of the PEN/C 60 interfaces have been investigated in numerous studies, including ultraviolet photoelectron spectroscopy, [54][55][56] external quantum efficiency (EQE) measurements, 57,58 microelectrostatic calculations, 59 and ab initio methods. 8,9 According to the X-ray diffraction measurement, 57 the PEN/C 60 interface morphology is dominantly an edge-on orientation. Therefore, we employed the atomic structure of the edge-on configuration of the PEN/C 60 bilayer heterojunction, which was prepared using molecular dynamics (MD) simulations.…”

“…Figure 4(a) shows the CT energy as a function of the e-h separation (R eh ), where R eh was defined as the center-of-mass distance between the electron and hole wave functions. 9 The CT states of the nearest-neighbor PEN-C 60 pairs, which contribute slightly to the CT absorption spectrum, 9 were obtained in the energy range of 0.8-1.1 eV. According to the EQE measurement of the PEN/C 60 bilayer heterojunction, 57 the low-energy CT absorption can be fitted to a Gaussian peak at 0.96 eV with 0.20 eV reorganization energy.…”

“…Theoretical investigations on organic/organic interfaces have provided microscopic information regarding the energies and wave function properties of the CT states. [6][7][8][9] Nevertheless, first-principles computations of the CT states in an organic/organic interface remain challenging because both electron correlation and polarizable environmental effects must be incorporated.…”