Center for Functional Nanomaterials Seminar

The combination of advances in top-down lithography and bottom-up self-assembly techniques and optical spectroscopy has resulted in a wealth of novel nanoscale materials with unprecedented optical properties that can be spectrally tuned and specifically designed and engineered. Time-resolved optical spectroscopy has shown to be a powerful technique for fully exploiting the potential functionality of these materials and for understanding fundamental dynamic processes that are extremely fast in nanoscale systems (assemblies and molecules) because the distances involved are so small.
I will discuss dynamic processes in semiconductor nanostructures, specifically multiexciton interactions that lead to ultrafast Auger recombination and Auger heating. Such interactions are very strong in NCs because of their nanoscale size that confines carriers within a small volume. Another consequence of the nanoscale size of NCs is the possibility of assembling NCs into hybrid structures of different materials that interact. For example, we measured efficient energy transfer between an InGaN/GaN quantum well (QW) and NCs that are deposited within a few nanometers from the QW. Such a hybrid structure converts QW emission into NCs emission with high efficiency and, therefore, presents a new concept for color conversion in light emitting devices. Besides proof-of-principle studies based on ultrafast spectroscopy measurements, I will show a practical implementation of high-efficiency color conversion in an electrically pumped light-emitting diode using nonradiative energy transfer. I will discuss current research plans including interactions between excitons and plasmons in hybrid semiconductor/metal nanostructures. Local field enhancement effects caused by surface plasmon oscillations can result in increased absorption and emission of the NCs; therefore, these hybrid structures are potential building blocks for light harvesting or emitting devices with increased efficiency.