Chain conformation and disorder in high mobility semiconducting polymers : understanding charge transport in complex microstructures
Abstract/Contents
- Abstract
- A critical step to understanding charge transport in complex systems is being able to characterize them accurately and extensively. In particular, the microstucture of conjugated polymers exhibits a coexistence of ordered and amorphous regions, with the size of the ordered regions being smaller than the length of individual polymer chains. In order to study the ordered regions we use advanced X-ray diffraction analysis in combination with computational modeling and measurements of optical and electrical properties. It was possible to uncover fundamental relationships between short-range order in pi-aggregates, aggregate connectivity and macroscopic charge transport in semiconducting polymers. An unusually high and materials-independent amount of paracrystalline disorder was found in all high-performing polymers. Computer simulations and analytical models made the connection between fluctuations in molecular arrangement and electronic traps. Charge transport studies elucidated the predominant role of paracrystallites in semicrystalline and strongly disordered polymer films. The other component of the microstructure -- the amorphous regions -- deserves our attention as well since aggregate connectivity depends on it. A model for charge transport in strongly disordered polymers was developed for this reason. The morphology of individual polymer chains can be determined by well-known statistical models. Likewise, the electronic coupling between units along a polymer chain and on different molecules can be determined by Marcus theory. Combining knowledge from both areas into an analytical and computational model that incorporates the structural and electronic properties of polymers, it is possible to explain observations that previously relied on phenomenological models. The multi-scale behavior of charges in these materials (high mobility at short scales, low mobility at long scales) is naturally described with this framework. Additionally, the dependence of mobility with electric field and temperature is explained in terms of conformational fluctuations and correlations. Bringing all these concepts together it is possible to provide a more complete description of the way in which charges move in conjugated polymers, a set of materials that occupies an intermediate region between ordered and disordered systems, with a great amount of complexity at various length scales. Doing so will facilitate the feedback cycle between molecular design, microstructure optimization, and device performance.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Noriega-Manez, Rodrigo Javier |
|---|---|
| Associated with | Stanford University, Department of Applied Physics |
| Primary advisor | Fisher, Ian R. (Ian Randal) |
| Primary advisor | Salleo, Alberto |
| Thesis advisor | Fisher, Ian R. (Ian Randal) |
| Thesis advisor | Salleo, Alberto |
| Thesis advisor | Stebbins, Jonathan Farwell |
| Advisor | Stebbins, Jonathan Farwell |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Rodrigo Javier Noriega-Manez. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Rodrigo Javier Noriega-Manez
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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