Excitons in Molecular Aggregates of 3,3‘-Bis-[3-sulfopropyl]-5,5‘-dichloro-9- ethylthiacarbocyanine (THIATS): Temperature Dependent Properties

J-aggregates of the dye THIATS (triethylammonium salt of 3,3‘-bis-[3-sulfopropyl]-5,5‘-dichloro-9-ethylthiacarbocyanine) with a two-component Davydov splitting of the exciton band were investigated in the temperature range from 5 to 130 K and at room temperature. A wide set of excitonic and optical characteristics (absorption line broadening, fluorescence line broadening, Stokes shift, coherence length, exciton migration rate, and wavelength dependence of the fluorescence decay time) of the same J-aggregates is presented. The exciton migration rate was found to be the most temperature sensitive property. The temperature dependence of a whole set of exciton properties reveals two critical temperatures:  30 and 70 K. The observed phenomena are described qualitatively as an interplay of static and dynamic disorder effects. At low temperature (T < 20 K) static disorder is the main factor which limits the coherence length and exciton−exciton annihilation rate and determines the absorption width. An intraband, ...