Solid-State Polarization, Charge-Transfer Excitations and Transport Levels at Organic Interfaces from a Screened Range-Separated Hybrid Functional

We present a robust approach for the description of the energetics of charge-transfer (CT) excitations and transport levels at organic interfaces based on a screened range-separated hybrid (SRSH) functional.[1] We show that SRSH functionals correctly capture the effect of solid-state electronic polarization on the renormalization of the transport gap and on screening of the electron–hole interaction. Compared to calculations based on nonscreened optimally-tuned RSH (long-range corrected) functionals, the SRSH-based calculations can be performed for both isolated molecular complexes and systems embedded in a dielectric medium with the same range-separation parameter. This allows a clear physical interpretation of the results in terms of solid-state polarization without further perturbation of the molecular electronic structure. Results obtained with this approach for CT-state energies of the weakly interacting donor/acceptor complexes of pentacene/C₆₀ and poly-3-hexylthiophene (P3HT)/PCBM compare very well with experimental data.
[1] Zheng et al., J. Phys. Chem. Lett. 8, 3277 (2017)