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Overall, this model breaks new ground in attempting to provide a universal synthesis of many of the transport models, which were oen system- or preparation-dependentin their predictive validity. The signature breakthrough in this study is describing the empirically observed relationship between the Seebeck coefficient and conductivity in polymers an alluringly simple S ~ E1/4
scaling that has eluded all insight untilnow. Researchers working on polymer thermoelectrics now have some access to what microstructural features of their system critically govern transport, based on accessible characterization data such as morphology and carrier concentration. Furthermore,this work uniquely introduces the useof Seebeck measurements to distinguish between transport models; for instance, the
key dierence between structural percolation (within a domain) and transport percolation (across a network of domains). This enables experimentalists to quickly spot the essential parameters to optimize in their systems, and further to understand how close they areto the fundamental limits for their polymer of choice.
As with any model that strives for comprehensiveness, there are certain limitations knowledge of the s parameter is vital, but hard to grasp or even measure, and the sheer number of new terms introduced may turn o some experimentalists who would benet from a distilled and more pragmatic application of these insights but without question this model sheds light on the dim confusion in understanding how charges move through polymers.
Jerey J.Urban is at the Molecular Foundry of the Lawrence Berkeley National Laboratory, Berkeley, California 94720USA.e-mail: mailto:[email protected]
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