Extraction of Radiative and Nonradiative Rate Constants of Super-Radiant J-Aggregates from Emission Spectra.

Equations relating the radiative and nonradiative decay rate constants of singlet excitons in super-radiant aggregates to the relative intensities of the 0-0 and 0-1 peaks in the emission spectrum were derived and tested against experimental data. In many instances, these equations eliminate the need for a time-dependent fluorescence decay measurement. They can also be useful in determining the fluorescence quantum yield.

New insights on the nature of two-dimensional polarons in semiconducting polymers: infrared absorption in poly(3-hexylthiophene).

Infrared absorption of positively charged polarons in conjugated polymer chains and π-stacked aggregates is investigated theoretically, employing a Holstein-based Hamiltonian which treats electronic coupling, electron-vibrational coupling, and disorder on equal footing. The spectra evaluated from the Hamiltonian expressed in a one- and two-particle basis set are essentially exact, insofar as the main, aromatic-quinoidal vibrational mode is treated fully nonadiabatically. Diagonal and off-diagonal ("paracrystalline") disorder are resolved along the polymer axis (x) and the aggregate stacking axis (y).

Contrasting photophysical properties of star-shaped vs linear perylene diimide complexes.

The absorption line shapes of a series of linear and star-shaped perylene diimide (PDI) complexes are evaluated theoretically and compared to experiment. The cyclic trimer and tetrahedral complexes are part of the symmetric series, characterized by a single interchromophoric coupling, J(0), between any two PDI chromophores. The measured spectra of all complexes show pronounced vibronic progressions based on the symmetric ring stretching mode at ~1400 cm(-1).