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Plasmonic fluorescence enhancement of poly(3-hexylthiophene) for organic solar cell applications

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Jacklyn Claraine Bush (Creator)
Institution
Western Carolina University (WCU )
Web Site: http://www.wcu.edu/404.asp
Advisor
David Evanoff, Jr.

Abstract: Solar cells are becoming an attractive alternative energy source considering the need to lessen dependence on nonrenewable energy sources such as fossil fuels. Organic photovoltaics (PVs) are inexpensive to produce, flexible, and eliminate many potential environmental hazards. However, organic solar cells are greatly limited in their capacity to efficiently convert sunlight into usable energy. Herein, an approach to increase the efficiency of exciton formation of poly(3- hexylthiophene) (P3HT), a common polymer used in organic solar cell devices, is described. This enhancement occurred by adding silver nanoparticles to the polymer surface. The metal nanoparticles cause an increased exciton excitation rate within the polymer through a mechanism known as surface-enhanced fluorescence (SEF). Specifically, P3HT fluorescence is increased when molecules are within the near fields of a metallic nanoparticle under plasmon resonance conditions. Theoretically, the enhancement of polymer exciton formation should correlate to heightened efficiency when utilized within a PV device. Silver nanoparticles are an attractive choice for SEF, as these particles possess strongly scattering local fields, a highly-polarizing, non-radiative field that extends deep into the particles' environment, and a plasmon resonance that overlaps well with both the absorption of P3HT and the solar spectrum maximum. In this study, silver nanoparticles with diameters of 15-153 nm have been synthesized in order to optimize the fluorescence enhancement factor of P3HT films of comparable thickness to those used in organic solar cells. Another aspect of this work was the development of a basic and reliable methodology for the preparation and analysis of P3HT/silver films. This standard protocol allows for the future application of our findings into actual devices and is vital considering the lack of current literature reporting studies of fluorescence effects produced from particles in this size range. It was determined that the addition of silver nanoparticles to the P3HT surface produced a significant increase in fluorescence. Also observed were higher enhancement factors associated with increasing nanoparticle diameter due to the scattering properties associated with larger particles. The enhancement associated with increasing particle size occurred independently of spin-coating speed of the polymer or silver nanoparticle concentration, though additional studies in the future are required for better methods of P3HT film deposition and the accurate measurement of particles underneath the polymer layer. Once enhancement parameters are optimized, studies will also include the incorporation of these particles into a device.

Additional Information

Publication
Thesis
Language: English
Date: 2012
Keywords
Nanoparticle, Plasmon Resonance, Poly(3-hexylthiophene), Silver, Solar Cell, Surface-Enhanced Fluorescence
Subjects
Solar cells