Organic solar cells enhanced by cadmium sulfide nanoparticles and a carbon buckyball derivative (PCBM)

Abstract

Organic solar cells (a.k.a. organic photovoltaic cells, OPVs, polymer solar cells) offer a promising approach to inexpensive, lightweight, flexible, and environmentally friendly devices that can convert sunlight into useable electrical power. Major challenges in developing organic cells at the current stage include low power conversion efficiency (standing laboratory record a maximum of 6% in literature compared to a typical 15% efficiency of commercial polycrystalline Silicon solar cells), polymer degradation especially in ambient air and humidity in the presence of light, and relatively low mechanical durability. My research focuses on the fabrication and characterization of conjugated polymer solar cells incorporated with nanoscale structures, such as Carbon nanotubes, Cadmium Sulfide nanoparticles and Carbon Buckyballs (e.g. PCBM). The incorporation of certain nanostructures has proven to enhance exciton dissociation and charge transport utilizing their high surface-area and unique electrical properties (Le. high mobility, semiconductivity). Key factors including the type of nanomaterials, treatments, geometry, and concentration in the polymer matrix were studied. Relationships between these factors were established in terms of different facets of cell performance (e.g. power conversion efficiency, fill factor, Voc, Jsc, internal losses). Results showed that Cadmium Sulfide nanoparticles independently enhance Voc, and PCBM nanoparticles enhance Jsc. It was also shown, however, that these two materials cannot work together to augment both values in tandem. They do, in fact, impede each other's abilities to enhance organic solar cells. I will be presenting background information on organic photovoltaics, current status of the field, and my research at the Hawaii Nanotechnology Laboratory and Hawaii Natural Energy Institute's (HNEI) Thin Films Lab on improving specific aspects of performance of bulk-heterojunction solar cells based on poly(3-hexylthiophene) (P3HT), a conjugated polymer, embedded with nanomaterials like Carbon nanotubes, Cadmium Sulfide nanoparticles and Carbon Buckyballs.