Engineered Nanoparticles for Advanced Photovoltaic, Photonic, and Imaging Applications

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Advances being made on the synthesis of nano-structured materials and on the ability to engineer their properties emanating from their dimensions and structure will have a strong and positive impact on advanced energy conversion, light-emitting, and imaging applications. Quantum dots (QD) demonstrate extraordinary optoelectronic and photonic properties due to their very nature of quantum confinement. Highly tunable properties can be achieved in such nanocrystals fabricated with controlled architectures. By exploiting these structures and their interfaces new generations of optoelectronic devices can be conceived and new frontiers can be reached in related applications. In the proposed research QDs and nanowires with desired properties will be synthesized and novel applications will be demonstrated in photovoltaic (PV), photonic, and imaging devices. By employing oil-in-water micro-emulsion processes colloidal solutions of QD solutions will be synthesized. Different architectures and size control will be achieved in fabricating the core/shell/shell and core/shell structures with high luminous quantum efficiency, stability, and lifetime. The QD structures to be fabricated include CdSe/ZnS, CdSe/ZnS/silica, PbS, CuInS2/ZnS. Nanowires of ZnO will be grown by hydrothermal method and also by top-down RIE etching, and will be used in specific device designs, in combination with the QD layers. QD materials with narrow absorbtion band in the UV region will be employed as photonic down-converters, or as luminescent down-shifters in PV devices. By embedding the QDs in polymeric host media integrable optical converter layers will also be achieved. In addition to their use of optical converters, QDs will also be implemented as active electrical components in QD-sensitized solar cell structures as planar ZnO film/QD structures, and as ZnO nanowire/QD structures with high conversion efficiencies. New light emitting device prototypes employing the synthesized ZnO nanowires in combination with QD layers will be demonstrated to yield white light LEDs. Furthermore, in the firld of detectors, the ability of the QDs to down-convert UV into higher (near infrared) wavelength photons will also be utilized to fabricate advanced detector devices, demonstrating extension of the detection band to include UV capability. The project will demonstrate applicability to novel imaging devices (CCD-based) with integrated layer of QDs with the required absorption/emission bands. Overall, the project involves fabrication methodologies and characterization of nanostructures with tunable properties, and demonstrates, through relatively simple fabrication technologies, advanced devices for future energy, light emission, and imaging applications.