Push-Pull functional compounds consisting of dicyanorhodanine derivatives have attracted a lot of interest because their optical, electronic, and charge transport properties make them useful as building blocks for organic photovoltaic implementations.The analysis of the frontier molecular orbitals shows that the vertical transitions of electronic absorption are characterized as intramolecular charge transfer; furthermore, we show that the analyzed compounds exhibit bathochromic displacements when comparing the presence (or absence) of solvent as an interacting medium. In comparison with materials defined by their energy of reorganization of electrons (holes) as electron (hole) transporters, we find a transport hierarchy whereby the molecule (Z)-2-((1,1-Dicyanomethylene)-5-(4-dimethylamino)benzylidene)-1,3-thiazol-4 is better at transporting holes than molecule (Z)-2-((1,1-Dicyanomethylene)-5-(tetrathiafulvalene-2-ylidene)-1,3-thiazol-4.
Understanding electron transfer in organic molecules is of great interest in quantum materials for light harvesting, energy conversion and integration of molecules into solar cells. This, however, poses the challenge of designing specific optimal molecular structure for which the processes of ultrafast quantum coherence and electron transport are not so well understood. In this work, we investigate subpicosecond time scale quantum dynamics and electron transfer in an efficient electron acceptor Rhodanine chromophoric complex. We consider an open quantum system approach to model the complex-solvent interaction, and compute the crossover from weak to strong dissipation on the reduced system dynamics for both a polar (Methanol) and a non polar solvent (Toluene). We show that the electron transfer rates are enhanced in the strong chromophore-solvent coupling regime, being the highest transfer rates those found at room temperature. Even though the computed dynamics are highly non-Markovian, and they may exhibit a quantum character up to hundreds of femtoseconds, we show that quantum coherence does not necessarily optimise the electron transfer in the chromophore.
Photoinduced
electron transfer in multichromophore molecular systems
is defined by a critical interplay between their core unit configuration
(donor, molecular bridge, and acceptor) and their system–solvent
coupling; these lead to energy and charge transport processes that
are key in the design of molecular antennas for efficient light harvesting
and organic photovoltaics. Here, we quantify the ultrafast non-Markovian
dissipative dynamics of electron transfer in D−π–A
molecular photosystems comprising 1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene
(BODIPY), Zn–porphyrin, fulleropyrrolidine, and fulleroisoxazoline.
We find that the stabilization energy of the charge transfer states
exhibits a significant variation for different polar (methanol, tetrahydrofuran
(THF)) and nonpolar (toluene) environments and determine such sensitivity
according to the molecular structure and the electron–vibration
couplings that arise at room temperature. For the considered donor–acceptor
(D–A) dyads, we show that the stronger the molecule–solvent
coupling, the larger the electron transfer rates, regardless of the
dyads’ electronic coherence properties. We find such coupling
strengths to be the largest (lowest) for methanol (toluene), with
an electron transfer rate difference of 2 orders of magnitude between
the polar and nonpolar solvents. For the considered donor–bridge–acceptor
(D–B–A) triads, the molecular bridge introduces an intermediate
state that allows the realization of Λ or cascaded-type energy
mechanisms. We show that the latter configuration, obtained for BDP-ZnP-[PyrC60] in methanol, exhibits the highest
transfer rate of all of the computed triads. Remarkably, and in contrast
with the dyads, we show that the larger charge transfer rates are
obtained for triads that exhibit prolonged electron coherence and
population oscillations.
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