Charge carrier dynamics in heterostructured semiconductor nanocrystals and nanocrystal solids – Michail Zamkov

Date: Mon. November 21st, 2011, 12:30 pm-1:30 pm
Location: Rockefeller 221

In the first part, I will present a novel strategy for processing of colloidally stable semiconductor nanoparticles (also known as nanocrystals or quantum dots) into all-inorganic solid films, deployable for photovoltaic applications. The method relies on encapsulation of semiconductor nanocrystal arrays within a matrix of a wide-band gap inorganic material, which preserves optoelectronic properties of individual nanoparticles, yet, renders the nanocrystal film photoconductive. The photovoltaic performance of fabricated nanocrystal solids is demonstrated through the development of prototype solar cells exhibiting stable and efficient operation in ambient conditions.
The second part of the presentation will focus on ultrafast electron processes taking place in heterostructured nanocrystals comprising metal (Au) and semiconductor (CdS) material domains. The study employs ultrafast transient absorption technique to explore the interaction between plasmons of metal nanoparticles and excitons in semiconductor nanocrystals. Present measurements indicate that the formation of excitons and corresponding band gap emission in CdS are suppressed as a result of ultrafast carrier trapping by the interfacial states. We also show that charging of gold domains under illumination effectively decreases the quantum confinement of CdS nanorods, which explains previously observed modification of CdS spectra in metal-semiconductor nanocomposites.