Jan 19
Cancelled - "Designing Solid State Materials from Quantum Dots:
Artificial Atomic Building Blocks' by Cherie R. Kagan,
University of Pennsylvania, Department of Electrical and Systems Engineering, Department of Materials Science and Engineering, Department of Chemistry
Chemistry Department Seminar: Cherie Kagan (U. Penn)
Quantum dots (QDs) are nanoscale, typically 2-20 nm diameter, fragments of bulk semiconductors. They
are also known as “artificial atoms” since electrons, holes, and excitons are quantum-mechanically
confined and occupy discrete electronic states in QDs, akin to those in atoms. Advances in wet-chemical
synthetic methods enable the preparation of QDs tailorable in size, shape, and composition. As-
synthetized, these QDs are typically capped by organic ligands and behave like colloids as they are
readily dispersed in solvents. QDs may be assembled or deposited from colloidal dispersion to forms
glassy or crystalline solids. Just as in atomic solids, the size and composition of the QDs, the average
interparticle distance, and the number of nearest neighbors govern their physical properties. In this talk,
I will build on the analogy between QDs and atoms and describe the design of solid state QD electronic
materials. In particular, I will focus on routes to manipulate the surface chemistry of QDs to strengthen
electronic coupling, by exchanging the ligands used in synthesis for more compact chemistries that
decrease interparticle distance; and to dope QD solids, by introducing atoms and ions that serve as
impurities or modify stoichiometry. Ultimately, I will connect QD material design to the physical
properties of these artificial solids that are being explored in electronic and optoelectronic devices.