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Research Statement

In recent years, understanding physical and chemical properties of nanoscale materials such as carbon nanotubes, nanocrystals and nanowires has been at the center of intense research efforts, because of their unique scientific and application opportunities. These nanoscale structures often exhibit electrical and optical properties comparable and, in some cases superior, to traditional semiconductors while maintaining the processing advantages of organic materials. Moreover, the key electrical and optical parameters can be tuned simply by changing their size thus providing a rational route to optimize the device performances within the same material configuration. Several electrical and optoelectronic devices that demonstrate the potential of nanoscale structures have been realized thus far, including various logic gates, highly efficient photovoltaic cells, electrically and optically driven lasers, and quantum optical light sources. The performance of many of these devices is determined by the complex interplay between multiple processes occurring in differing length and time scales. For instance, the operation of a photovoltaic cell involves the efficient photon absorption, separation of an electron and a hole, charge transport through the nanostructures and at the interface, charge trapping, and energy relaxation. The design and optimization of electronic and optoelectronic devices therefore requires an experimental tool to investigate these complex, multi-scale processes at the system-wide level.

Our group's research interest is to develop an experimental platform that investigates electrical, optical and thermal properties of individual nanostructures and their assembly with an ultrahigh spatial, temporal and energy resolution that have been accessible only to their macroscopic counterparts. In particular, we are most interested in interrogating how the dynamics of fundamental physical quanta – photons, electrons and phonons are intertwined in complex nanoscale materials, while exploring advanced nanoscale device configurations that fully utilize the interplay among different physical processes. Through these studies, we would like to develop useful insights for basic questions regarding the nature of nanostructures and their interfaces, and ultimately pursue novel nanoscale electrical and optical devices with fundamentally different functionalities.
Under this central theme, we are currently developing several experimental research programs that address specific problems central to the understanding and optimization of the nanoscale materials and device properties. These problems include:

  • Spatially and temporally resolved carrier dynamics (injection, transport and recombination) in nanoscale optoelectronic devices based on nanocrystals, nanowires and inorganic/organic hybrid materials.

  • Energy conversion between charge carriers and other energy carrying quanta (phonons and photons) in nanoscale light sources and calorimeters.

  • Electronic band characterization and charge/energy flow at the nanomaterial/electrode interface and nano- and biomaterial interfaces


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