MSE Seminar Series: Joseph G. Tischler
Friday, February 21, 2014
1:00 p.m.-2:00 p.m.
Room 2110 Chemical and Nuclear Engineering Building
301 405 5240
Tailoring Optoelectronic Properties of PbSe Nanostructures: 0D to 1D
Joseph G. Tischler
U.S. Naval Research Laboratory
Advances in the fabrication and understanding of colloidally grown nanocrystal quantum dots, nanorods and nanowires have been driven by intense interest in their potential applications. These applications include biological labels, as well as tunable optoelectronic devices such as light emitting diodes, lasers, detectors and photovoltaics.
In this talk we show that by controlling the size and shape of our nanostructures, it is possible to tailor optoelectronic properties such as, bandgap, anisotropic absorption, electron and hole mobility as well as the exciton (i.e. electron-hole pair) dynamics. In particular, we report a significant enhancement of multiple exciton generation in PbSe nanorods over nanocrystal quantum dots characterized by a reduction of the threshold energy to 2.3Eg, which approaches the theoretical limit of 2Eg. We find that while the MEG efficiency is constant for rod aspect ratios between 4 and 11, the Auger recombination rate decreases linearly with increasing rod length. The apparent contradiction between the length dependence of Auger recombination and the inverse-Auger process of MEG is attributed to differences in the final density-of-states for each process. These results point to a means of suppressing Auger recombination without affecting the MEG efficiency, which is the ideal situation for optoelectronic devices.
Realization of high efficient nanostructure based optoelectronics require further improvements in the electron and hole transport as well as nanostructure passivation. Current accomplishments in these matters will also be discussed.
About the Speaker
Dr. Joseph G. Tischler obtained his undergraduate degree in Physics from the University of Buenos Aires (Argentina) in 1994, and his Ph.D. degree in Physics from The University at Buffalo-State University of New York in January of 2000. In 2000 he joined the Naval Research Laboratory as a National Research Council Postdoctoral Fellow until 2003, in which he became a permanent staff member. Dr. Tischler is also an Adjunct Professor at The University at Buffalo since 2012.
As a Research Physicist in the Photovoltaics Section of the Solid State Branch in the Electronics Technology Division at the Naval Research Laboratory, Dr. Tischler has strong interests in novel materials for photovoltaic applications (solution synthesized nanocrystals, InP lattice matched III-Vs, CIGS, perovskites, etc.). He is also pursuing research in antimonide based superlattices, plasmonics and phononics, as well as physics in 2D materials, all of these with applications for infrared/THz imaging.