Prediction of the lowest charge-transfer excited-state energy at the donor-acceptor interface in a condensed phase using ground-state DFT calculations with generalized Kohn-Sham functionals.

Abstract

Knowledge of the charge (electron) transfer process at the donor-acceptor interface is required to understand the working mechanisms of different organic photovoltaic materials. Investigating the lowest charge-transfer state in organic donor-acceptor solar cells is important as it allows the destruction/formation of excitons and polarons to be studied, and is directly related to the open circuit voltage. By performing low-cost and feasible calculations of ground-state electronic structures using the Mulliken rule as well as the optimally tuned range-separated hybrid (OTRSH) density functional and a regular long-range corrected functional, the lowest charge-transfer (CT) state energies of a series of dimers containing functionalized anthracene (the donor) and tetracyanoethylene (the acceptor) were obtained. The jumping distances of excited electrons during CT were calculated. The polarizable continuum model was applied to account for the effects of the solvent methylene chloride (CH2Cl2) on the lowest CT state energies obtained from gas-phase calculations. The calculated lowest CT state energies of the dimers were close to the corresponding experimental results, with a root mean square deviation (RMSD) of 0.22eV.