Thematically, this work focuses on developing solution blending processes that result in the formation of interconnected polymer networks for enhanced electronic properties. This research follows a bottom-up approach to develop process-structure-property relationships using the "fruit fly" of conjugated polymers, poly(3-hexylthiophene) (P3HT). Herein, we demonstrate facile solution processing methods that focus on blending multiple components to target the formation of interconnected assemblies. P3HT is the canonical semicrystalline conjugated polymer, and was used to investigate the mechanism of self-assembly in solution. The polymer molecular weight distribution, solute-solvent interactions, and quantity of seed nuclei are shown to be tunable parameters impacting the degree of interconnectivity. These approaches were investigated using a wide array of strategies to induce nucleation, including exposure to low dose UV, microfluidic flow processing, and poor solvent addition. A particularly promising approach involves the selective mixing of a nucleated polymer solution with a non-nucleated sample via seed nucleation. These processing approaches have improved the charge carrier mobility from a base of ~10-3 cm2/V-s to values exceeding 2x10-1 cm2/V-s. Process-structure-property relationships were developed to quantitatively describe the tradeoffs between polymer network formation and grain boundaries on charge transport. All examined cases suggest an optimal processing window for long range interconnectivity, in which a moderate level of crystallinity is associated with the highest mobility. Finally, materials informatics approaches were leveraged to develop process-property relationships to help guide the next level of experimental efforts. A database of 218 data points from 19 publications on P3HT was created with mobility values ranging from 1.0x10-6 to 2.8 x10-1 cm2/V-s. A classification technique in which devices were sorted into high performing and low performing was applied. A reduced design space containing all high performing points, as well as some having poor performance, is identified for the purpose of focusing future experiments.
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MATIN Development Team