ULTRAFAST EXCITATION RELAXATION IN COLLOIDAL PARTICLES OF CHLOROALUMINUM PHTHALOCYANINE - ONE-DIMENSIONAL EXCITON-EXCITON ANNIHILATION

The excited-state dynamics of crystalline ClAl phthalocyanine colloida l particles have been studied by means of picosecond and femtosecond a bsorption spectroscopy. In the measured relaxation dynamics, the initi al excited-state evolution, taking place during the first picosecond a fter excitation, was distinguished from the overall exciton decay. Exc itation transfer between different molecular species is suggested to b e the most probable reason to the initial (less than or equal to 1 ps) excited-state dynamics. Exciton decay was found to be dominated by ex citon-exciton annihilation with a t(-1/2) time dependence of the excit ed-state population, suggesting a one-dimensional exciton diffusion. A 0.2-1 ps intermolecular exciton hopping time was determined from the annihilation dynamics.