Achievement

In collaboration with the Wise group at Cornell, IGERT Fellow Carmella Calabrese conducted experiments in ultrafast pump-probe spectroscopy--measuring relaxation dynamics of free electrons in PbS quantum dots (QDs)--to improve understanding of electron transfer at interfaces. Most alternative solar cell designs rely on interfacial electron transfer to separate photogenerated excitons into free carriers. Though interfacial electron transfer is of fundamental importance, this process is not well understood. Heterogeneity of nanostructured samples and difficulty of tracking photogenerated free electrons complicate analysis. Carmella has employed a new continuum IR probe, which covers the entire vibrational spectrum in a sub-100 fs pulse, to track generation and relaxation of free carrier electrons in PbS QDs. She is now studying the charge injection from QDs into semiconductor surfaces using nonlinear optical spectroscopic techniques.