Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.
Author ORCID Identifier
N/A
AccessType
Open Access Dissertation
Document Type
dissertation
Degree Name
Doctor of Philosophy (PhD)
Degree Program
Polymer Science and Engineering
Year Degree Awarded
2018
Month Degree Awarded
September
First Advisor
Alejandro L. Briseno
Second Advisor
Samuel P. Gido
Subject Categories
Polymer and Organic Materials | Semiconductor and Optical Materials
Abstract
This thesis focuses on tuning molecular packing of organic semiconductors through processing or chemical modifications to increase performance and establish structure-property relationships. Chapter 2 utilizes differing processing techniques to alter the molecular packing of bistetracene in the thin film and thorough polymorph characterization to relate the modification of molecular packing to the increase in charge mobility and mechanism. Chapter 3 introduces the oligomer as a model system to resolve issues that would be difficult or impossible using polymeric systems, due to their monodispersity and increased crystallinity allows for more detailed structural characterization. In this chapter we determine a crystal packing and melting point alternation in BTTT monomers, a trend well documented within organic small molecules, yet largely ignored within the organic semiconductor community. A series of BTTT dimers with various side chains lengths were synthesized in Chapter 4 to quantify the effect of side chain length on bimolecular crystal formation with PCBM using smaller side chains, outside the solubility limit of the parent polymer, and discovered and characterized a phase transition from a bimolecular crystal to amorphous blend upon decreasing side chain length, greatly influencing the electronic properties of the blends. Chapter 5 expands on the knowledge of the previous chapter, designing BTTT dimers with variable side chains using side chains that fall on both sides of the phase transition to investigate the influence of side chain position and size on molecular packing and blended morphology. In Chapter 6, using the benchmark BTTT dimer, we explore the effect of dopant chemical structure on morphology and conductivity of blended films. Surprisingly, the doping mechanism differs from that of the parent polymer, and by tuning the dimer/dopant interactions, demonstrate a differing morphology and large variation in conductivity dependent on dopant choice.
DOI
https://doi.org/10.7275/12748309
Recommended Citation
Burnett, Edmund, "INCREASING ORGANIC SEMICONDUCTOR PERFORMANCE THROUGH CHEMICAL AND PROCESSING MODIFICATIONS" (2018). Doctoral Dissertations. 1328.
https://doi.org/10.7275/12748309
https://scholarworks.umass.edu/dissertations_2/1328