Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Molecular Electronics and Excited State Properties

CPP 3.12: Vortrag

Montag, 1. April 2019, 12:45–13:00, H13

What is the impact of the donor length on the electronic and optical properties of charge-transfer complexes? — •Ana M Valencia and Caterina Cocchi — Physics Department, Humboldt-Universität zu Berlin und IRIS Adlershof

The size ratio between donor and acceptor moieties in organic semiconductors is know to effectively influence the doping mechanism [1]. Here, we investigate a series of charge transfer complexes formed by oligothiophene molecules of increasing length doped by the acceptor F4TCNQ. Using hybrid DFT as a starting point, we assess the electronic and optical properties of these systems from many-body perturbation theory (GW and the Bethe-Salpeter equation). We find that the frontier orbitals (HOMO and LUMO) are hybridized in all complexes, while the distribution of deeper occupied and higher virtual states depend on the nT length. The first bright excitation is dominated by the HOMO-LUMO transition occurring approximately at the same energy in all systems. At increasing donor length, higher-energy peaks exhibit different character depending on the donor conjugation length [2]. We also consider how the relative concentration of donor and acceptor molecules impacts these properties. The rationale offered by our results contributes to clarify the excitation processes in organic donor/acceptor complexes. [1] H. Mendez, et al., Nat. Comm. 6, 8560 (2015). [2] A.M. Valencia and C. Cocchi submitted (2018).