2016/12/09 by Thomas Stangl, Stangl, Thomas, Philipp Wilhelm +9
Engineering · Materials Science · #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Luminescence and Fluorescent Materials #Molecular Junctions and Nanostructures #Organic Electronics and Photovoltaics
paper · pdf · doi:10.48550/arxiv.1612.02976
openalex publication_date 2016/12/09 · openalex created_date 2022/08/15 · openalex updated_date 2026/07/28
An appealing definition of the term "molecule" arises from consideration of\nthe nature of fluorescence, with discrete molecular entities emitting a stream\nof single photons. We address the question of how large a molecular object may\nbecome by growing deterministic aggregates from single conjugated polymer\nchains. Even particles containing dozens of individual chains still behave as\nsingle quantum emitters due to efficient excitation energy transfer, while the\nbrightness is raised due to the increased absorption cross-section of the\nsuprastructure. Excitation energy can delocalize between individual polymer\nchromophores in these aggregates by both coherent and incoherent coupling,\nwhich are differentiated by their distinct spectroscopic fingerprints. Coherent\ncoupling is identified by a ten-fold increase in excited-state lifetime and a\ncorresponding spectral red shift. Exciton quenching due to incoherent FRET\nbecomes more significant as aggregate size increases, resulting in\nsingle-aggregate emission characterized by strong blinking. This mesoscale\napproach allows us to identify intermolecular interactions which do not exist\nin isolated chains and are inaccessible in bulk films where they are present\nbut masked by disorder.\n