Charge Effects on Optoelectronic Properties of Nanorod Heterostructures

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Nontechnical Description: Reducing the sizes of semiconductor crystals to nanometer length scales can lead to useful optical and electrical properties that do not exist in large crystals. These tiny semiconductor nanocrystals are finding innovative applications in displays, lighting, and biomedical imaging. Important to developing such applications is the understanding of how electrical charges affect optical and electrical characteristics as well as the ability to control charging effects in nanocrystals. This project elucidates the effects of electrical charges in an emerging class of solution-processed semiconductor nanocrystals with shape, optical and compositional anisotropy, which offers novel means of manipulating electrical charges. The students participating in this project tackle multi-faceted challenges with ample educational and training opportunities necessary for becoming leaders in interdisciplinary science and engineering fields. The PI is committed to utilizing the research results generated in this research project to enhance teaching and promoting benefits of nanoscience to the general public.Technical Description: Recently achieved multi-composition semiconductor nanocrystals with complex yet well-defined epitaxial interfaces, especially those with rod shapes (or nanorods), represent an emerging class of colloidal semiconductor materials. Active heterojunctions and structural/optical anisotropy designed into these nanorods provide novel means of controlling separation, injection, extraction and recombination of charge carriers. However, surrounding induced charges, whether intentional or not, can lead to an entirely different behavior than one often assumed based on an intrinsic or charge neutral material. This project examines systematically how work functions of contacting charge transport layers and electrodes affect charging behavior and how pre-existing charges in these multi-heterojunction nanorods influence carrier injection, photoluminescence and electroluminescence. The project also investigates how structural/optical anisotropy and active heterojunctions can be utilized to control charging behavior. The knowledge gained through this project helps to identify critical parameters and means for achieving enhanced materials properties and device performance.