Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Sean E. Shaheen

Second Advisor

Daniel S. Dessau

Third Advisor

Jao van de Lagemaat

Fourth Advisor

Garry Rumbles

Fifth Advisor

Matthew A. Glaser

Abstract

Photon upconversion, the process of combining multiple low-energy photons into one higher-energy photon, is a fundamental interaction of light and matter that has applications in fields ranging from cancer therapy to solar energy. However, all photon upconversion methods demonstrated thus far involve challenging aspects, including requirements of high excitation intensities, degradation in ambient air, requirements of exotic materials or phases, or involvement of inherent energy loss processes.

In this thesis I present the first experimental observations and characterization of Cooperative Energy Pooling (CEP), a photon upconversion mechanism that provides a pathway towards overcoming the aforementioned disadvantages. This singlet-based process utilizes a sensitizer-acceptor design in which multiple photoexcited sensitizer chromophores resonantly and simultaneously transfer their energies to a higher-energy state on a single acceptor. This thesis presents two generations of CEP systems along with steady-state and time-resolved spectroscopies verifying the upconversion process. This work is expanded with theoretical calculations and numerical simulations modeling the CEP process, the results of which are used to derive design guidelines for optimized CEP systems.

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