EP02.04.07 : What Role Does Driving Force Play in CdSe Nanocrystals for Photon Up Conversion

5:00 PM–7:00 PM Apr 3, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Emily Moses1 Narek Megerdich1 Beverly Ru1 MingLee Tang1

1, University of California, Riverside, Riverside, California, United States

The upconversion system involving CdSe nanocrystals (NC) light absorbers and organic emitter molecules has shown advances in efficiency and holds promise for robust applications where ultraviolet light is generated from the visible. Further advances in efficiencies will rely heavily on a thorough understanding of the underlying energy transfer systems. This work explores the charge, and triplet energy transfer from five differently sized nanocrystals, ranging from 2.2 to 4.2 nm in diameter, corresponding to decreasing band gap. First, by using dynamic and static quenching of benzoquinone, a known probe of photo-induced electron transfer, as well as transient absorption measurements of the triplet energy transfer (TET) to bound 9-anthracene carboxylic acid (9-ACA) ligands, we can directly calculate the rate of charge and energy transfer from CdSe NCs. We can compare the transfer mechanism of triplets on NCs to the two electron Dexter energy transfer rates. Second, by synthesizing a range of NC sizes, we can vary the driving force for electron and energy transfer in the CdSe-9-ACA system. This allows us to determine the mechanism, as either Marcus-Hush, which treats the NC as a sphere and the solvent as a dielectric, or Marcus-Jortner, which considers the coupling between the NC and the vibrational mode of the solvent. Determining the mechanisms can guide us to design a better system with improved energy transfer for engineering photon upconversion systems.