Interplay of exciton annihilation and transport in fifth order electronic spectroscopy

Intrachain and Interchain Exciton–Exciton Annihilation in Donor–Acceptor Copolymers

“…Exciton–exciton annihilation (EEA) in polymers and aggregates has been attracting both theoretical and experimental research interest not only because it can severely reduce the exciton lifetime, especially under strong illumination, but also because EEA dynamics could provide a wealth of information on the exciton diffusion and exciton–exciton interaction. − EEA in polymers takes place when two excitons are in close proximity, where one of them recombine by pumping the other one to a higher excited state. The exciton that gained energy from EEA quickly relaxes to the lowest exciton state by emitting phonons.…”

From wavelike to sub-diffusive motion: exciton dynamics and interaction in squaraine copolymers of varying length

“…An extended nonlinear spectroscopy such as 2DES can in higher orders directly observe the biexciton dynamics in time. 24,[31][32][33][34][35][36] Next to power-dependent annihilation, spectroscopy methods to observe the long-range exciton transport include spatially resolved transient absorption or emission 37,38 and surface or bulk quenching. 39,40 Despite being powerful and widespread, all these techniques have their limitations.…”

Annihilation Dynamics of Molecular Excitons Measured at a Single Perturbative Excitation Energy

“…Fifth-order 2D-electronic spectroscopy (R 5 -2D) line shapes detected along the k⃗ S = ± 2 k⃗ 1 ∓ 2 k⃗ 2 + k⃗ 3 phase matching directions overcome this problem as biexciton dynamics, such as EEA, contribute to the signal already at perturbative level of excitation density. − The general temporal evolution of the R 5 -2D signal still contains both exciton transport and annihilation contributions. In a recent publication, we formally proved that spectral integration of fifth-order signals over both excitation and emission frequencies eliminates the dependence on single exciton transport rates for homo-aggregates with aligned transition dipole moment geometry of arbitrary length. The spectrally integrated R 5 -2D signal of such aggregates is thus a measure for tracking and pinpointing annihilation dynamics of molecular excitons at a single perturbative excitation density.…”