Abstract
Natural light harvesting as well as optoelectronic and photovoltaic devices depend on efficient transport of energy following photoexcitation. Using common spectroscopic methods, however, it is challenging to discriminate one-exciton dynamics from multi-exciton interactions that arise when more than one excitation is present in the system. Here we introduce a coherent two-dimensional spectroscopic method that provides a signal only in case that the presence of one exciton influences the behavior of another one. Exemplarily, we monitor exciton diffusion by annihilation in a perylene bisimide-based J-aggregate. We determine quantitatively the exciton diffusion constant from exciton–exciton-interaction 2D spectra and reconstruct the annihilation-free dynamics for large pump powers. The latter enables for ultrafast spectroscopy at much higher intensities than conventionally possible and thus improves signal-to-noise ratios for multichromophore systems; the former recovers spatio–temporal dynamics for a broad range of phenomena in which exciton interactions are present.
Highlights
Natural light harvesting as well as optoelectronic and photovoltaic devices depend on efficient transport of energy following photoexcitation
We demonstrate how the EEI2D spectra of a perylene bisimide J-aggregate can be experimentally acquired and how they can be used to characterize exciton diffusion properties
Before providing a formal treatment of EEI2D, we describe the essence of the technique on a more intuitive level
Summary
Natural light harvesting as well as optoelectronic and photovoltaic devices depend on efficient transport of energy following photoexcitation. We determine quantitatively the exciton diffusion constant from exciton–exciton-interaction 2D spectra and reconstruct the annihilation-free dynamics for large pump powers The latter enables for ultrafast spectroscopy at much higher intensities than conventionally possible and improves signal-to-noise ratios for multichromophore systems; the former recovers spatio–temporal dynamics for a broad range of phenomena in which exciton interactions are present. The exciton delocalization over several molecular constituents[1,2] together with the exciton mobility across the system highly increases the chance that the presence of one exciton influences the behavior of another one In this case we speak about exciton–exciton interaction (EEI). Some information on double excitations is contained in the third-order double-quantum coherence signal k1 + k2 − k316–20
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