Center for Functional Nanomaterials Seminar

Efficiencies of energy conversion processes in renewable energy devices are in many cases limited by device/material properties whose control by conventional schemes is being becoming extremely difficult. The device nanostructuring and use of nanomaterials provide alternative ways to address such issues, potentially permitting much improved device energy conversion efficiency. In this talk, I exemplify such cases by discussing nanostructured thin film organic solar cells and inorganic semiconductor nanowires. In the first part, two examplary nanostructured device concepts, namely nanostructured electrical contacts and blend parallel tandem architecture, are elaborated in order to address inefficient charge transport and large optical bandgap of organic semiconductors that hinder efficient photovoltaic energy conversion in organic solar cells. The structures are implemented using carbon-nanotube-dispersed polythiophene-fullerene bulk heterojunction solar cells and phthalocyanine-based multi-dye blend devices. In the second part, I explain schemes to control structural and physical properties of GaN nanowires and their potential application in efficient nanowire-based thermoelectric energy conversion devices. GaN nanowires are grown by thermal chemical vapor deposition with controlled growth orientation and surface morphology. Nanowires' electrical and diameter-dependent electromechanical resonance properties are studied in conjunction with their significantly reduced thermal conductivity which is driven by the dimensional confinement and increased phonon scattering with internal planar defects and high concentration of doping impurities. I discuss the implication of these findings in developing efficient nanowire-based thermoelectric components.