Coherent Mechanism of Exciton Transport in Disordered J-Aggregates

Abstract

Using a luminescent exciton trap, a mechanism of the exciton migration in disordered J-aggregates of amphiphilic analogue of pseudoisocyanine (amphi-PIC) dye has been investigated in the temperature range of 80−300 K. Due to a strong topological disorder in amphi-PIC J-aggregates observed in a binary dimethylformamide−water (DMF/W) solution with a low water content, two types of excitonic states have been revealed, delocalized exciton state that forms the main part of the J-aggregates absorption band (J-band) and a state of strongly localized excitons that forms the long-wavelength edge of the J-band. These excitonic states are characterized by the different mechanism of the exciton transport: a coherent mechanism for delocalized excitons and an incoherent one for localized excitons. As localized excitons provide a small contribution to the J-band and appear only at high degree of topological disorder, the coherent mechanism of the exciton transport in amphi-PIC J-aggregates has been concluded. Such a result is nontrivial due to a small delocalization length of excitons in amphi-PIC J-aggregates (11 monomers at 80 K) provided by the moderate energetic disorder and strong exciton−phonon coupling.

Exciton diffusion in organic photovoltaic cells

“…Since the exciton is extended along the length of the aggregate, more research is needed to determine the precise interplay between coherent and incoherent motion for exciton transport in such aggregates. 105,106 More exotic structures have also been suggested for enhancing exciton diffusion. [107][108][109][110] Poulsen et al report a nanostructured host-guest system that orders an oligophenylene vinylene LC into well-ordered channels separated by an organic host material.…”

Excitons in Carbonic Nanostructures

“…The disruption of the electron-hole radiative recombination resulting in quenching occurs locally, but the whole nanoparticle may provide the mechanistic framework in harvesting of the photo-generated electrons for productive purposes [279]. The observed superquenching effect is likely a result of an amplified energy transfer occurring in the C-dot due to the exciton propagation, analogous to another system exhibiting Frenkel excitons, the conjugated polymer nanoparticles [280,281] and J-aggregates of cyanine dyes [282,283].…”

Exciton delocalization and dynamics in helical π-stacks of self-assembled perylene bisimides

“…6 For instance, one-dimensional (1D) structures composed of single-stranded p-stacked monomers are of particular interest due to their potential advantages of superior charge transport along the long axis of aggregates, which is prerequisite for applications in nanoscale transistors, sensors, power sources, battery anodes and organic light-emitting displays. [7][8][9][10][11][12][13] On the other hand, in contrast with charge transport phenomena, far less studies are available on exciton transport along 1D p-stacked aggregate structures, although this property is of equal importance. In this regard, it is necessary to elucidate the nature of molecular excitons generated in self-assembled molecular aggregates for their practical applications.…”

“…In this regard, it is necessary to elucidate the nature of molecular excitons generated in self-assembled molecular aggregates for their practical applications. 8,11,12,[14][15][16][17][18][19] Among various p-conjugated molecules, self-assembled pstacks composed of perylene tetracarboxylic acid bisimide (PBI) dyes with high chemical robustness and inherent high uorescence quantum yield can be ideal candidates for the investigation of photodynamic processes in self-assembled molecular architectures. 20,21 Since the single strand of PBI monomers can be easily fabricated by controlling the intermolecular forces such as hydrogen bonding and p-p stacking interactions, there have been various approaches to construct novel self-assembled supramolecular structures with characteristic photophysical properties.…”