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Fluctuations in the Emission Polarization and Spectrum in Single Chains of a Common Conjugated Polymer for Organic Photovoltaics
Author(s) -
Hedley Gordon J.,
Steiner Florian,
Vogelsang Jan,
Lupton John M.
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201804312
Subject(s) - materials science , photoluminescence , polymer , conjugated system , polarization (electrochemistry) , chromophore , organic solar cell , polyfluorene , optoelectronics , nanoscopic scale , photovoltaics , dipole , nanotechnology , chemical physics , photovoltaic system , spectroscopy , photochemistry , physics , chemistry , organic chemistry , ecology , composite material , biology , quantum mechanics
Abstract Measuring the nanoscale organization of conjugated polymer chains used in organic photovoltaic (OPV) blends is vital if one wants to understand the materials. This is made very difficult with high efficiency OPV polymers such as PTB7 that form aggregates, as a lack of periodicity and a high degree of disorder make understanding of the nanoscale organization challenging. Here, single molecule spectroscopy is used to observe single chains and aggregates of PTB7. Using four detectors the photoluminescence intensity, wavelength, polarization, and lifetime are simultaneously monitored. Fast (milliseconds) and slow (seconds) fluctuations are observed over a time window of 30 s in all of these observables from single aggregates and chains as individual chromophores activate and deactivate, leading to dynamical changes in the emission spectrum and dipole orientation. This information can be used to help reconstruct the spatial and spectral organization of disordered aggregates of PTB7, thereby adding valuable new information on how the chains are arranged in space.