Complex structural-optical property relationships in ternary and quaternary copper-indium-(zinc)-chalcogenide quantum dots at the ensemble and single particle level

by Heyes, Colin D.

Ternary CuInS2 quantum dots (QDs) have been proposed as a less toxic alternative to binary cadmium-based QDs for a wide range of applications, including bioimaging, photovoltaics and optoelectronics. While they offer similar tunability in terms of visible emission, these applications are hindered by the fact that there is a much poorer understanding the relationships between structure and optical properties. For example, CuInS2 have much wider emission spectra, much longer emission lifetimes and more complex blinking dynamics. Addnl., when the common process of shelling QDs with wider bandgap materials, such as ZnS or ZnSe is performed, a blue shift in the emission spectra rather than a red-shift is observed, resulting from some degree of ion exchange and/or interfacial alloying in addition to some shelling, leading to a mixture of ternary and quaternary composition In this talk, I will present our recent progress at attempting to control and quantify how the balance of ion exchange, alloying and shelling affects the optical properties such as quantum yield, emission spectral shape, blinking and emission lifetimes. Our goal is to develop a comprehensive physiochem. model of how the QD composition and local structure of the emitting centers affects charge carrier trapping and recombination in order to gain more control over such processes. Such control should allow us to tailor such QDs for several applications, particularly in various bioimaging and environmental modalities.