Charge-transfer excitations in molecular donor-acceptor complexes within the many-body Bethe-Salpeter approach

We study within the perturbative many-body GW (Green's function G and the screened Coulomb interaction W) and Bethe-Salpeter approach the low lying singlet charge-transfer excitations in molecular donor-acceptor complexes associating benzene, naphthalene, and anthracene derivatives with the tetracyanoethylene acceptor. Our calculations demonstrate that such techniques can reproduce the experimental data with a mean average error of 0.1-0.15 eV for the present set of dimers, in excellent agreement with the best time-dependent density functional studies with optimized range-separated functionals. The present results pave the way to the study of photoinduced charge transfer processes in photovoltaic devices with a parameter-free ab initio approach showing equivalent accuracy for finite and extended systems. (C) 2011 American Institute of Physics. [doi:10.1063/1.3655352]