Abstract
The optical functionalities such as exciton recurrence and migration for dendritic systems, e.g., dendrimers, are investigated using the quantum master equation (QME) approach based on the ab initio molecular orbital configuration interaction (MO-CI) method, which can treat both the coherent and incoherent exciton dynamics at the first principle level. Two types of phenylacetylene dendrimers, Cayley-tree dendrimer and nanostar dendrimer with anthracene core, are examined to elucidate the features of excion recurrence and migration motions in relation to their structural dependences. It is found that the nanostar dendrimer exhibits faster exciton migration from the periphery to the core than Cayley-tree dendrimer, which alternatively exhibits exciton recurrence motion among dendron parts in case of small relaxation parameters. Such strong structural dependence of exciton dynamics demonstrates the advantage of dendritic molecular systems for future applications in nano-optical and light-harvesting devices.
Highlights
A great deal of attention has focused on the electronic, optical and magnetic functionalities of dendrimers – a new class of supermolecules characterized by branched tree-like architectures – due to their promising applications in future electronics, photonics and spintronics [1-17]
In this study, using the ab initio molecular orbital (MO) quantum master equation (MOQME) approach, we have investigated incoherent and coherent exciton dynamics, i.e., exciton migration and exciton recurrence, in two kinds of phenylacetylene dendrimers, with Cayley-tree and nanostar structures, respectively
Nanostar dendrimers exhibit faster exciton migration than Cayley-tree one though both systems give muti-step exciton states with energy gradient from periphery to the core region. This feature is found to be explained by the difference in the energy interval between exciton states and the overlap of exciton distributions between adjacent exciton states, which significantly affect the exciton relaxation factors
Summary
A great deal of attention has focused on the electronic, optical and magnetic functionalities of dendrimers – a new class of supermolecules characterized by branched tree-like architectures – due to their promising applications in future electronics, photonics and spintronics [1-. Shortreed et al have reported that extended phenylacetylene dendrimers with Cayley-tree structure transport excitation energy absorbing in the periphery region to the central region of the molecule [15] This energy migration process is found to be highly efficient and directional, in contrast to typical energy transport observed in most of supramolecular antennas in green plants and their artificial polymeric mimics, where the energy transport is partially carried out by random walk and thermal activation due to their disordered structures. The present results will contribute to a novel development of energy transfer/transport and the creation and control schemes of superposition states in dendrimers
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