UC Santa Cruz

Natural photosynthetic systems achieve remarkable light-harvesting efficiency through the precise supramolecular organization of chromophores, where non-covalent interactions govern excitonic energy capture and directional transport. Conjugated polyelectrolytes (CPEs), semiconducting polymers bearing pendant ionic side chains, offer a synthetic platform capable of replicating these design principles in aqueous environments. Their tunable electronic structure, combined with electrostatic and hydrophobic driving forces for self-assembly, enables the formation of conjugated polyelectrolyte complexes (CPECs) that support long-range exciton migration on timescales comparable to biological antenna systems. Despite this promise, the fundamental exciton dynamics governing energy transfer and charge generation in these materials remain insufficiently understood, limiting the rational design of CPE-based light-harvesting architectures.This dissertation pursues a two-pronged investigation addressing both the mechanistic photophysics of CPECs and their application in aqueous-processed organic photovoltaic (aOPV) devices. The first thrust examines how the molecular architecture of CPEs governs electronic energy transfer (EET) in CPECs. Because excitonic wavefunctions in these systems are spatially delocalized over length scales commensurate with donor-acceptor separations, the point-dipole approximation underlying conventional Förster theory becomes physically inadequate. This work therefore investigates how the real-space distribution of π-electron density along conjugated backbones modulates interchain excitonic coupling and EET rate constants, with complementary studies exploring the relationships between morphological organization, electronic structure, and excited-state dynamics in complex fluid phases.The second thrust demonstrates a novel fabrication methodology for organic photovoltaic devices processed entirely in aqueous media. Conventional device fabrication relies on halogenated or toxic organic solvents, fundamentally undermining the environmental promise of organic solar technologies. By exploiting the directed self-assembly of oppositely charged CPEs in water, this work establishes the proof-of-concept viability of constructing functional photovoltaic devices using water as the exclusive processing solvent. Together, these investigations advance a mechanistic foundation for the rational design of CPE-based light-harvesting systems and delineate a pathway toward environmentally responsible manufacturing of thin-film solar technologies.