Intermolecular sequential energy transfer in thin films of a white emitting copolymer

Abstract

The authors investigated the energy transfer between the chromophors of a white emitting polyspirobifluorene copolymer containing a blue emitting backbone, a green, and a red emitting dye. They demonstrate that the green dye is mainly excited by blue→green Förster resonant energy transfer (FRET), with a Förster radius R0bg=35Å. The red dye is instead excited by direct blue→red FRET (R0br=21Å) and by sequential blue→green→red FRET (R0gr=31Å). Finally, the authors show that the FRET processes, fundamental to have white emission, are of intermolecular nature, while intramolecular energy migration and transfer are negligible.