Advancing Hybrid Solar Technology by New Nano-Material InvestigationEPA Grant Number: F5B20284
Title: Advancing Hybrid Solar Technology by New Nano-Material Investigation
Investigators: Wadia, Cyrus
Institution: University of California - Berkeley
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2005 through August 31, 2008
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
The objective of this project is to advance the role of hybrid solar photovoltaics (PV) in our global energy markets. This will be achieved by investigating novel materials and processing techniques that will both increase hybrid cell efficiency and drive down overall processing costs.
Today, PV power represents less than 0.1% of worldwide energy consumed. Even at the current annual growth rate of 30%, solar will still only meet about 2% of our global supply by 2020. I believe this can be cost-effectively doubled or even tripled by market penetration of hybrid photovoltaics over the next 5 years. Hybrid cells are blended composites that embed an active layer of thin film semiconducting nanoparticles in a matrix of conducting polymer. These cells combine favorable material properties of the bulk organic polymers (i.e. abundant, non-toxic, low cost to manufacture) with the favorable conductive properties of the nanoparticles. Advantageous over traditional Silicon (Si) solar cells because of material flexibility and low cost potential, hybrid PV could serve different energy markets from those of traditional Si solar cells. Before such technology and application advancement is possible, hybrid PV performance improvements must be resolved.
The foundation of this project is new material engineering, namely synthetic methods for growing one-dimensional nanowires. Nanostructure assembly is a challenge because the length scales prevent direct mechanical manipulation. Steady progress has been made with numerous vapor phase techniques, such as chemical vapor deposition, molecular beam epitaxy, and sputtering. Yet these high temperature processes may be too costly for industrial scale production. A more promising synthetic process for hybrid PV is the vapor-liquid-solid mechanism (VLS) which favors high throughput and lower cost. This technique combined with epitaxial crystal growth (VLSE) has been used successfully to control growth properties of ZnO nanowires. However, these ZnO nanowires have sub-optimal conductive properties. This is an opportunity to investigate new materials more favorable for hybrid cell use. I plan to apply the VLSE techniques to new composite blends varying both the bulk polymer and nanowire materials. Most published work on hybrid photovoltaic material has been with TiO2 or CdSe nanoparticles suspended in a conjugated polymer like poly-3(hexylthiophene). These materials have had reasonable conductive properties but unfavorable morphology for photovoltaic applications. Moreover, the toxicity of materials like cadmium raises some concern as to their viability in the marketplace. This requirement will be a major consideration for the material choices I make. Furthermore, as part of my research, I intend to explore alternative VLS and VLSE processes that can be optimized for new composites under investigation.