Title | Morphology controls the thermoelectric power factor of a doped semiconducting polymer. |
Publication Type | Journal Article |
Year of Publication | 2017 |
Authors | Patel, Shrayesh N., Anne M. Glaudell, Kelly A. Peterson, Elayne M. Thomas, Kathryn A. O'Hara, Eunhee Lim, and Michael L. Chabinyc |
Journal | Sci Adv |
Volume | 3 |
Issue | 6 |
Pagination | e1700434 |
Date Published | 2017 Jun |
ISSN | 2375-2548 |
Abstract | The electrical performance of doped semiconducting polymers is strongly governed by processing methods and underlying thin-film microstructure. We report on the influence of different doping methods (solution versus vapor) on the thermoelectric power factor (PF) of PBTTT molecularly p-doped with F n TCNQ (n = 2 or 4). The vapor-doped films have more than two orders of magnitude higher electronic conductivity (σ) relative to solution-doped films. On the basis of resonant soft x-ray scattering, vapor-doped samples are shown to have a large orientational correlation length (OCL) (that is, length scale of aligned backbones) that correlates to a high apparent charge carrier mobility (μ). The Seebeck coefficient (α) is largely independent of OCL. This reveals that, unlike σ, leveraging strategies to improve μ have a smaller impact on α. Our best-performing sample with the largest OCL, vapor-doped PBTTT:F4TCNQ thin film, has a σ of 670 S/cm and an α of 42 μV/K, which translates to a large PF of 120 μW m(-1) K(-2). In addition, despite the unfavorable offset for charge transfer, doping by F2TCNQ also leads to a large PF of 70 μW m(-1) K(-2), which reveals the potential utility of weak molecular dopants. Overall, our work introduces important general processing guidelines for the continued development of doped semiconducting polymers for thermoelectrics. |
DOI | 10.1126/sciadv.1700434 |
Alternate Journal | Sci Adv |
PubMed ID | 28630931 |
PubMed Central ID | PMC5473677 |