Mechanism of exciton migration of dendritic molecular aggregate: a master equation approach including weak exciton–phonon coupling

Exciton dynamics in nanostar dendritic systems using a quantum master equation approach: core monomer effects and possibility of energy transport control

“…Before investigating the exciton dynamics of the nanostar aggregate models, we briefly explain our calculation scheme [25][26][27][28] using a quantum master equation approach including exciton-phonon coupling. We consider a molecular aggregate composed of two-state monomers with excitation energies {E i } and magnitudes of transition dipole moments {m i } (i ¼ 1; 2; .…”

“…These features are predicted to provide multistep exciton states, in which the exciton distribution is spatially well localized in each generation from higher exciton states (distributed in the periphery region) to lower exciton states (distributed in the core region) [19,[22][23][24]. In our previous studies using the dipole-coupled dendritic aggregate models [25][26][27], we have also pointed out the necessity of the relaxation effect between exciton states, originating in exciton--phonon coupling, for such efficient exciton migration in addition to multistep exciton states. The efficient multistep relaxation is found to require partial spatial overlaps of exciton distributions between neighboring exciton states, which are distributed in adjacent generations linked with meta-branching points.…”

“…Using the standard method of relaxation theory [30], we obtain a quantum master equation [26,27] for the exciton density matrix r under the Born-Markov approximation:…”

“…In order to elucidate the relaxation pathway and relative relaxation rate, we employ a relative relaxation factor, Dg(a-b) [26,27]:…”

Transport of optical excitations on dendrimers in the continuum approximation

“…Later Ranasinghe confirmed this by performing fluorescence anisotropy measurements at low temperatures (4 K) [22]. Thus, the alternative approach of coherent excitons extending over several dendrimer units has also been considered, in particular to describe energy transport from the periphery to the core [23][24][25][26][27].…”