Master of Engineering Science
Chemical and Biochemical Engineering
Dr. Paul Charpentier
Nanotechnology is allowing the solar energy industry to advance at an accelerating rate, although new materials and processes are required for developing new types of solar cells. Similar to other industries, it is desirable to develop the most environmentally friendly and cost-effective solutions on how to make these next generation materials. Of these new materials, quantum dots (QDs) are of current scientific interest which provide record-breaking increases in efficiency and a new approach for harnessing solar radiation. However, most previous QD work has focused on lead or cadmium based materials, which are not earth friendly and have low thresholds in both California and European legislation. For this reason, this work examines the earth friendly and abundant materials Copper Indium Sulfide (CIS) QDs, i.e. CIS-QDs, which have favorable emission properties. These materials were prepared and examined for use in solar harvesting in photovoltaic (PV) devices.
Copper Indium Sulfide (CIS) QDs were synthesized using three different synthesis techniques, then compared based on their optical and size-dependent properties. Two techniques followed a hydrothermal batch reaction process, referred to as hot injection (HI) and heat up (HU) techniques, that are differentiated by the time at which the sulfur component is added to the reaction medium. The third technique was based on a continuous microfluidic approach. Results showed that the QDs produced from the HU and HI methods have a chalcopyrite structure, with their optical properties being highly dependent on their size and elemental composition. QDs produced from the microfluidic approach were found to agglomerate quickly and had a resulting weak photoluminescent response.
This work examined these QDs in two separate solar applications, both for use in light spectrum conversion with solar films and for use in third generation solar cells. For application in light spectrum conversion, the QDs were melt-mixed with ethylene-vinyl-acetate plastic, using a twin-screw extruder and pressed into thin films using a Carver hydraulic press and Universal film maker. QDs were also reviewed for their use in third generation solar cell configurations. Based on the optimal configuration, QD sensitized solar cells were fabricated and tested. Resulting current-voltage (IV) curves and solar cell data showed a direct relation between QD composition and cell efficiency.
Ward, Harrison, "Copper Indium Sulfide Quantum Dots for Light Selective Nanocomposite Thin Films and Solar Cell Applications" (2016). Electronic Thesis and Dissertation Repository. 3474.