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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Michael D. Barnes
Anthony D. Dinsmore
Materials Chemistry | Materials Science and Engineering | Polymer and Organic Materials | Semiconductor and Optical Materials
Control over concurrent transport of multiple carrier types is desired in both soft and hard materials. For both types of materials, I demonstrate ways to characterize and execute governance over both electronic and ionic transport, and apply these concepts in the fabrication of devices with applications in conducting composites, photovoltaics, electrochemical energy storage, and memristors.
In soft materials, such as polymers, the topology of the binary polymer mesoscale morphology has major implications on the charge/ion transport. Traditional approaches to co-continuous structures involve either using blends of polymers or diblock copolymers. In polymer blends, the structures are kinetically trapped and thus have poor long term stability. In diblock polymers, such morphologies are not universally accessible to non-random coil polymers. I discuss an approach to binary polymer mesoscale morphologies via the assembly of polymer nanoparticles. In this strategy, polymers are assembled into spherical nanoparticles, which are then assembled into hierarchical mesoscale structures. First, I demonstrate, experimentally and computationally, that the electrical transport in semiconducting/insulating polymer nanoparticle assemblies can be predictably tuned according to power law percolation scaling. Then I show that nanoparticle assemblies can be utilized for tunable concurrent transport of electrons and holes for photovoltaics, and for electronic and ionic charges aimed at applications in electrochemical energy storage.
For hard materials, I detail the characterization of mixed electronic and ionic transport in hybrid organic/inorganic lead triiodide perovskites. I used the understanding of mixed electronic and ionic transport in these materials to explain poorly understood phenomena such as photo-instability and current-voltage hysteresis. Then, I show several examples of interfacial materials, and the characterization and implications of their respective work functions, as charge transport materials to control selective charge extraction from perovskites. And finally, I show how interfacial charge transport materials with ionic functionality can be used to change the interfacial chemistry at perovskite/charge transport material interfaces to control both electronic and ionic transport. In this regard, I demonstrate how an adsorbing interface for mobile ions can be used to control current-voltage hysteresis and state-dependent resistance, introducing a novel paradigm of interfacial ion adsorption to fabricate novel perovskite-based memristor devices.
Renna, Lawrence A., "Characterization of Electronic and Ionic Transport in Soft and Hard Functional Materials" (2017). Doctoral Dissertations. 969.