The study of solid-state organic chromophores has been soaring in the last decade owing to their wide applications in organic photovoltaics. These organic chromophores can absorb light in the visible region and form free charge carriers with proper design in molecular structure and device fabrication. In solid state, chromophores are immobilized and tend to form ordered structure. Ordered structures of organic chromophores provides better charge conduits than they are in amorphous state, thus improving the efficiency of charge transfer for harvesting solar energy.This dissertation mainly investigates three kinds of organic chromophores, perylene, tetraphenoxy-substituted perylenediimide (tpPDI), and pyromellitimide (PI). Two different tpPDIs were investigated on thin films and in single crystals. They show slip-stack packing in solid state. Photophysical studies of tpPDIs deposited on thin films reveal that tpPDI with octyl tail forms excimer after photoexcitation, while tpPDI with hydrogen tail undergoes symmetry-breaking charge separation (SB-CS). Solid-state SB-CS is rare and potentially useful for organic photovoltaic device fabrication. In addition to single crystals and thin films, we also take advantage of the ordered structure of nanoporous anodic aluminum oxide (AAO) membrane to assemble perylene and tpPDI chromophores. When covalently attached to the wall of AAO membranes, a perylene chromophore exhibits properties of J-aggregates, and form excimers with different degree and extent of charge-transfer characters as loading concentration and solvent polarity changes. While for a tpPDI chromophore, they show similar properties as stacked tpPDIs in cyclophanes, and undergo SB-CS with different rates as concentration of chromophore and solvent polarity varies. Not only the packing pattern can affect the properties of chromophores, but the morphology also plays an important role. A molecular hexagon based on PI is studied. In both solvents and in solid state, the PI-based hexagon folds into a double-ring structure held by intramolecular hydrogen bonds and carbonyl-carbonyl interactions. This folded double-ring scaffold also shows robustness at high temperature. This structure allows orbital overlap between PI units resulting electronic coupling between them.

Creator

• Chen, Su

DOI

• https://doi.org/10.21985/n2-600b-j698

Subject

• Chemistry

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:15882
• etdadmin_upload_864439

Date created

• 2021-01-01

Resource type

• Dissertation

Rights statement

• In Copyright