St. Albert Hall B-37
Department of Physics & St. John’s University Society
of Physics Students Chapter Seminar
Nanocrystals Physics, Engineering, and Future
Dr. Liangfeng Sun
School of Applied and Engineering PhysicsCornell University,
Supplies of clean energy are closely linked with global economic
growth, social stability and quality of life. Developing
energy-efficient devices and harnessing renewable energy (e.g.,
solar energy) are two solutions to meet this challenge.
Dr. Sun will discuss two areas of his research based on
(1)Nanocrystals based photovoltaic and
solid-state lighting devices.
The easily size-tunable energy gap of nanocrystals makes them
ideal photon-absorbing materials for solar-electricity devices.
High quantum yield makes them a good candidate material for
solid-state lighting. However, there are still challenging topics
in this field, such as control of exciton dissociation or formation
in a nanocrystal, control of charge transfer etc.
Dr. Sun will discuss some results about nanocrystal surface
modification and energy level alignments for nanocrystals-based
optoelectronic devices, which are closely related to the topics
(2) Interface electronic structures and charge dynamics
Since the interface-to-volume ratio of a nanocrystal increases
dramatically, the interface plays a critical role on material
properties. It greatly affects charge carrier generation,
transportation, and relaxation. Yet the microscopic nature,
electronic structure and relaxation dynamics of these interface
states are still poorly known, in part because of the lack of
effective experimental probes of these nano-interfaces.
In his recent research, Dr. Sun developed optical
second harmonic generation and electrogenerated chemiluminescence
spectroscopy to probe the interface electronic structure and
carrier relaxation dynamics of nano-interfaces. Combined with
photoluminescence measurements, we can obtain a more complete
picture of the electronic structure of a nanocrystal.
All interested students and faculty are invited.