Organic photovoltaics offer an opportunity to make solar cells more affordable and widely accessible using cheap, solution-processable light-absorbing layers. In order to realize new technologies, a fundamental understanding of organic chromophore photophysics is required to overcome efficiency limitations. Throughout this doctoral work, I investigated the kinetic and physical characteristics of various rylene diimide and tetrapyrrole macrocycles to gain insight into their individual suitability for use in energy technologies. I investigated many fundamental phenomena including symmetry-breaking charge separation in polycrystalline thin films of 1,6,7,12-tetra(phenoxy)perylene-3,4:9,10-bis-(dicarboximide) having either n-octyl groups (octyl-tpPDI) or hydrogen atoms (H-tpPDI) attached to its imide nitrogen atoms. We found that H-tpPDI films undergo rapid symmetry-breaking charge separation with a long-lived charge separated state, providing a new route to increase the open-circuit voltage and reduce recombination losses in organic solar cells. We also found that bis(3′-aminopentyl)-perylene-(3,4:9,10)-bis(dicarboximide) (C5PDI) undergoes quantitative singlet exciton fission in the solid-state despite lacking longitudinal slip-stacking in its crystal structure. Enhancement of the crystallinity of C5PDI films will improve the triplet quantum yield of this material for use in photovoltaic devices. I also studied various macrocycles including Zinc 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (t-Bu-ZnNc) and 13,23-diacetyl-8,8,18,18-tetra-methyl-12,22-diphenyl-bacteriochlorin (B-189) in the solid state and found that aggregation of such molecules slows internal conversion and enhances radiative decay from higher lying singlet excited states and allows faster intersystem crossing. Overall, these findings indicate a significant difference in dilute monomeric and aggregated molecular behavior, opening new pathways for energy technology applications.

Creator

• Ramirez, Carolyn E.

DOI

• https://doi.org/10.21985/n2-vhjg-kn36

Subject

• Physical chemistry
• Chemistry
• Energy

Language

• en

Alternate Identifier

• etdadmin_upload_916673
• http://dissertations.umi.com/northwestern:16153

Keyword

• non-linear spectroscopy
• charge separation
• singlet fission
• environmental justice
• organic photovoltaic

Date created

• 2022-01-01

Resource type

• Dissertation

Rights statement

• In Copyright