Date of Award
Ph.D. in Chemistry
Jared H. Delcamp
Nathan I. Hammer
Ryan C. Fortenberry
University of Mississippi
An urgent challenge limiting the improvement of dye-sensitized solar cell (DSC) technology is the availability of chromophores capable of harvesting the full spectrum of solar irradiation; this is especially evident at longer wavelengths. Therefore, the achievable power conversion efficiency (PCE) is effectively capped due to limited photocurrent generation. Molecular design strategies involving proaromaticity and cross-conjugation are employed in this work to facilitate access to low-energy near-infrared (NIR) photons. Utilizing the ubiquitous Donor–p-spacer–Acceptor (D–p–A) architecture, these concepts are studied by incorporating an indolizine donor (RR13 and RR14), and thieno[3,4-b]pyrazine (allowing additional substitution for cross-conjugation, JW1) and thieno[3,4-b]thiophene (AP25) p-spacers. The sensitizers are assessed computationally and systematically characterized. Proaromaticity is shown to reduce optical bandgaps relative to reference dyes in all cases, absorbing photons of energy as low as ~1.38 eV when immobilized on TiO2. As a result, optimized photovoltaic devices (via cosensitization and other photon management strategies) give outstanding photocurrent for allorganic DSCs in excess of 20 mA/cm2 and reach a record 25 mA/cm2 in the case of co-sensitized AP25. Subsequent integration within a sequential series multijunction device (SSM–DSC) results in a high 10.1% PCE and demonstrates practicality as a power source for the water-splitting reaction with 3.9% solar-to-hydrogen efficiency in a cost-effective, precious metal-free system. Finally, our champion NIR organic DSC is shown to be a competitive alternative to benchmark Ru DSCs and market-dominating Si and GaAs PVs as a back subcell in multijunction solar cells due to superior performance under filtered or reduced illumination.
Watson, Jonathon, "Achieving Record Photocurrent: Strategies for Harvesting and Utilizing Low Energy Photons in Organic Dye-Sensitized Photovoltaics" (2022). Electronic Theses and Dissertations. 2464.
Available for download on Friday, February 07, 2025