Design Rules for Complex Emulsion Targets in Resonant Infrared, Matrix-Assisted Pulsed Laser Evaporation of Polymer Thin Films
Polymer thin films used in many modern technologies, such as light emitting diodes, solar cells, flexible electronics, and sensors, are fabricated in numerous ways. Of these methods, solution-based processing techniques are the most common with established commercial manufacturing and high throughput. However, these approaches face multiple disadvantages when applied to device heterostructures that are essential for optoelectronic devices. In contrast, vacuum-based techniques are amenable to multi-layer films with varying composition, regardless of polymer solubility. Resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) allows for the deposition of finely tuned polymer structures, such as uniquely graded heterostructures, which solution processing techniques cannot achieve. The primary contribution of this dissertation is to bring to light general design rules for complex emulsions that comprise the targets used in RIR-MAPLE to deposit polymer thin films containing crystalline domains.
Initially, design rules are discussed that lead to the formation of pinhole-free polymer films that also contain crystalline domains. This work addresses a fundamental challenge to promote the crystalline phase, as opposed to the more prevalent amorphous phase, while also maintaining high-quality film surfaces. These design rules are then expanded to include the effects of overall emulsion composition on the resulting emulsion morphology. In order to maximize the content of the crystalline polymer phase in thin films, the use of various surfactants (not yet applied to RIR-MAPLE emulsion targets) is investigated due to the unique interactions that occur, thereby determining the emulsion morphology. As a result, the impact of surfactant molecular structure on the resultant film properties is described for the first time. Finally, the design rules identified for complex emulsions are used in a fundamentally different emulsion chemistry to verify the extent to which these rules are generally applicable.
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