Picosecond fluorescence decay and exciton dynamics in a new far-red molecular J-aggregate system

We present and characterize a new J-aggregate-type nanostructure formed by self-assembling of 3,3'-diethylthiadicarbocyanine iodide molecules in a solution. We measure picosecond kinetics of fluorescence from the lowest exciton band, lying in the far-red wavelength range around 810-830 nm. At temperatures 4-300 K we observe a non-exponential fluorescence decay and show that this is a result of exciton-exciton annihilation in a small exciton domain regime. We also measure the temperature dependence of single-exciton radiative lifetime and give a consistent description of it in terms of a self-trapping of exciton in a discrete one-dimensional chain. (C) 2000 Elsevier Science B.V. All rights reserved.