Local Phonon Environment as a Design Element for Long-lived Excitonic Coherence: Dithia-anthracenophane Revisited

Excitonic energy transfer in light harvesting complexes, the primary process of photosynthesis, operates with near-unity efficiency. Experimental and theoretical studies suggest that quantum mechanical wave-like motion of excitons in the pigment-protein complex may be responsible for this quantum efficiency. Observed coherent exciton dynamics can be modelled completely only if we consider the interaction of the exciton with its complex environment. While it is known that the relative orientation of the chromophore units and reorganisation energy are important design elements, the role of a structured phonon environment is often not considered. The purpose of this study is to investigate the role of a structured immediate phonon environment in determining the exciton dynamics and the possibility of using it as an optimal design element. Through the case study of dithia-anthracenophane, a bichromophore using the Hierarchical Equations Of Motion formalism, we show that the experimentally observed coherent exciton dynamics can be reproduced only by considering the actual structure of the phonon environment. While the slow dephasing of quantum coherence in dithia-anthracenophane can be attributed to strong vibronic coupling to high-frequency modes, vibronic quenching is the source of long oscillation periods in population transfer. This study sheds light on the crucial role of the structure of the immediate phonon environment in determining the exciton dynamics. We conclude by proposing some design principles for sustaining long-lived coherence in molecular systems.

FB-REDA: fragment-based decomposition analysis of the reorganization energy for organic semiconductors

We present a fragment-based decomposition analysis tool (FB-REDA) for the reorganisation energy (λ) in the framework of fragment-mode analysis. FB-REDA provides useful insight into rational design low-λ organic semiconductors.

Structural and electronic characterisation of π-extended tetrathiafulvalene derivatives as active components in field-effect transistors

The rigidification of the molecule in π-extended tetrathiafulvalenes is beneficial for reducing the reorganisation energy but has an unfavorable impact on the electronic dimensionality, as observed in the resulting transistors.

Influence of a nearby substrate on the reorganization energy of hole exchange between dye molecules

The outer-sphere reorganisation energy for hole transfer between dye molecules in polar solvents is reduced by around 20% by dielectric substrates.