Concannon, Nolan2023-02-162023-02-162022-12https://hdl.handle.net/11299/252554University of Minnesota Ph.D. dissertation. December 2022. Major: Chemical Engineering. Advisor: Russell Holmes. 1 computer file (PDF); xi, 144 pages.To prevent the most harmful effects of the present climate crisis, development ofhigher performance energy conversion devices is needed to accelerate the adoption of renewable energy and energy efficiency technologies. Organic semiconductor materials have demonstrated exciting efficiency gains in a variety of emerging and in-production devices. These materials exhibit a variety of emergent material and device physics, requiring additional research to understand and design next-generation energy conversion technologies. Thin films of organic semiconductors, common in large-area optoelectronics such as consumer displays, present rich photophysics due to forming room-temperature stable excitons, unlike silicon or III-V semiconductors. A plethora of emergent phenomena of excitons at organic semiconductor interfaces requires a detailed understanding of such processes to optimally design devices such as energy-efficient lighting, flexible or transparent solar cells, photodetectors and displays. This dissertation focuses on investigating the novel optical physics of excited states at organic donor-acceptor interfaces through emission spectroscopy of organic mixtures and bilayer devices. In one study, exciplex diffusion is investigated in several donor-acceptor pairings toward an improved understanding of the mechanism of nanoscale energy transport in organic semiconductor mixtures. Additionally, the effect of electric field on exciplex emission spectra is studied to detail the effect of field on exciplex energy and electron-hole separation. Finally, preliminary data displaying the effect of binary dilution on exciplex energy in a two-component mixture is presented. All together, these findings present new insights into the behavior of key device properties such as exciton diffusion length and excited state energies to aid further study of device performance.enCharge transfer statesExciplexesExcitonsOptoelectronicsOrganic semiconductorsThesis or Dissertation