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Coherent Dynamics of Mixed Frenkel and Charge-Transfer Excitons in Dinaphtho[2,3‑b:2′3′‑f]thieno[3,2‑b]‑thiophene Thin Films: The Importance of Hole Delocalization
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posted on 2016-04-25, 19:13 authored by Takatoshi Fujita, Sule Atahan-Evrenk, Nicolas P. D. Sawaya, Alán Aspuru-GuzikCharge-transfer states in organic
semiconductors play crucial roles
in processes such as singlet fission and exciton dissociation at donor/acceptor
interfaces. Recently, a time-resolved spectroscopy study of dinaphtho[2,3-b:2′3′-f]thieno[3,2-b]-thiophene (DNTT) thin films provided evidence for the
formation of mixed Frenkel and charge-transfer excitons after the
photoexcitation. Here, we investigate optical properties and excitation
dynamics of the DNTT thin films by combining ab initio calculations
and a stochastic Schrödinger equation. Our theory predicts
that the low-energy Frenkel exciton band consists of 8–47%
CT character. The quantum dynamics simulations show coherent dynamics
of Frenkel and CT states in 50 fs after the optical excitation. We
demonstrate the role of charge delocalization and localization in
the mixing of CT states with Frenkel excitons as well as the role
of their decoherence.