Exciton trapping in π-conjugated materials:: A quantum-chemistry-based protocol applied to perylene bisimide dye aggregates

Access to excited-state structures and dynamics of pi-chromophor aggregates is needed to understand their fluorescence behavior and the properties of related materials. A quantum-chemistry-based protocol that provides quantitative and qualitative insight into fluorescence spectra has been applied to perylene bisimide dimers and provides excellent agreement with measured fluorescence spectra. Both dispersion and dipol-dipole interactions determine the preferred relative arrangements of the chromophores in ground and excited states of the dimer. An exciton trappping mechanism is identified, which may limit the energy transfer properties of perylene bisimide and other dye materials.