Linking microstructure to transport at several lengthscales in conjugated polymers – Alberto Salleo, Stanford University

March 9, 2021 @ 4:00 pm – 5:00 pm
Where: Meeting ID: 917 9401 4655 Passcode: 080277
Mengxia Liu

Carrier mobility in conjugated polymers continues to increase with recent reports of field-effect mobilities exceeding 10 cm2/V.s. Charge transport is intrinsically dependent on processes occurring across multiple lengthscales. In order to access order parameters at the molecular scale we use charge modulation spectroscopy (CMS) combined with theory. This technique allows us to further differentiate field-induced and doping-induced charges and study how their delocalization depends on local structure and disorder. CMS of a model polythiophene system highlights how transport depends on both local order and mesoscale connectivity. As a result, we study the mesoscale organization of polymers using new techniques in the transmission electron microscope. By combining 4D STEM and HRTEM we are able to study the microstructure across a range of length-scales in real space and reciprocal space. These techniques are used on homopolymers and donor-acceptor copolymers and allow to extract information about the microstructure that is typically not visible by inspection. Microstructural analysis at these lengthscales coupled with charge transport theory allows to better understand the role of defects. Thus, such multiscale studies of microstructure are instrumental in guiding our understanding of charge transport in conjugated polymers.

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