Seminar on
Modern Optics and Spectroscopy


Moungi Bawendi, MIT

Nanocrystal quantum dot science and technology: The importance of spectroscopy

March 6, 2007

12:00 noon - 1:00 p.m. Grier Room 34-401


Abstract:

This talk will review the background chemistry and photophysics of nanocrystal quantum dots that is relevant to their application in opto-electronic devices and biomedical and biological imaging. We will begin by discussing the spectroscopy of excitons and multiexcitons in single quantum dots. Most device applications of quantum dots thus far involve either the generation of excitons followed by light emission, such as in a light emitting device, or the generation of excitons followed by exciton ionization and harvesting of carriers, such as in a photoconductive device or a solar cell. Multiexciton physics in quantum dots is important for potential lasing applications and for probing the possibility of carrier multiplication from quantum dots, which has been proposed as a route to increasing the efficiency of quantum dot based solar cells. We will report on the use of correlation spectroscopy to unambiguously determine multiexciton emission. We will also assess carrier multiplication in CdSe quantum dots. We will give an overview of photoconduction in quantum dot films and the parameters that describe and modify its efficiency. Finally, we will give examples of the application of quantum dots as the emitters in layered hybrid inorganic/organic light emitting devices and in devices where the charge transport layers are inorganic oxides. For biological imaging and biomedical imaging, we will show that quantum dots can be engineered to be more than passive reporters of their location; that they can also act as sensors of their microenvironment. We will provide an example of a quantum dot based pH sensor that is ratiometric and self-referencing and that is optimized for the biological environment.

TUESDAYS, 12:00-1:00, GRIER ROOM (34-401)
Refreshments served following the seminar

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Co-sponsored by the George R. Harrison Spectroscopy Laboratory,
the Department of Electrical Engineering and Computer Science and
the School of Science, Massachusetts Institute of Technology.