Probing of molecular aggregates with exciton annihilation

It is characteristic for the kinetics of singlet–singlet exciton annihilation in a finite-size molecular aggregate to approach with time the steady state corresponding to the very last single excitation. The elimination of corresponding signal from the kinetic trace exposes the dominance of the exponential decay. The characteristic time constant representing the slowest annihilation mode is related to the number of exciton hopping sites and the pairwise hopping time by solving the single excitation trapping problem. The relevance of proposed approach for the analysis of annihilation kinetics is demonstrated for the bacterial light-harvesting complex LH1, the reaction center complex D1–D2 and C60 structures.