Photovoltaic solar cell technologies will play a vital role in efforts to reduce carbon emissions and to provide clean and secure sources of energy. However, to be competitive with abundant, nonrenewable fuels such as coal for electric power production, solar panel efficiencies must be improved, and production costs must be reduced in order to deliver a lower unit cost of electric power production. One trend is to reduce the thickness of the solar cell, which decreases distances for charge transport, reduces materials usage, and speeds up the deposition time. Another trend is to use inexpensive materials such as TiO2 or polymers. Thinning cells to improve performance and reduce costs has its limits, since thinner solar cells absorb less light. To address this problem, plasmon-supporting metal particles offer significant promise to increase the ability of thin solar cells to absorb light. Plasmon-supporting metal particles can be used to efficiently couple light into a broad range of photovoltaic materials, without the need to radically redesign devices.
Intellectual Merit
This research will develop nanostructured materials for plasmon-mediated solar energy conversion, and gain fundamental understanding of this process. Ligand-passivated colloidal metal nanoparticles will be used as the model plasmonic material, since their optical, electronic, and chemical properties can be independently tuned by the core and ligand shell. The colloidal approach also allows the particles to be mixed or spread in a wide number of materials by a variety of strategies. Using plasmons to improve light absorption in solar cells is expected to have performance enhancing features. Specifically, the high light absorptivity of plasmons produces electrons closer to the photoanode, shortening the charge transfer path and improving photocurrent collection. The decrease in the necessary thickness for the solar cell device stack could also reduce material and processing costs. Furthermore, plasmons enable the use of new materials and strategies that would otherwise be unable to absorb light efficiently.
The research has three aims. The first aim is to develop novel synthesis strategies for making nanocomposite materials and hybrid structures for plasmonic light capture. The second aim is establish the fundamental principles governing energy transfer between metal nanoparticles and different photovoltaic media. The third aim is understand the impact of metal nanoparticles on charge transport within these materials in working devices. All of these activities seek to understand the basic science of how plasmon-supporting metal nanoparticles function in photovoltaic energy capture and transfer systems.
The novelty and intellectual merit of this research is that it will provide basic understanding of how core-shell plasmonic metal nanoparticles affect light and absorption and charge transfer in photovoltaic devices. This research is potentially transformative because plasmon-mediated solar energy conversion offers a completely new and tunable approach to enhance light absorption and increase charge transport photovoltaic devices, leading to enhanced efficiency and thinner devices that in turn have the potential to reduce unit electrical power generation costs.
Broader Impacts
Outcomes of this research have the potential to improve the efficiency and reduce costs of solar cells. These outcomes could also make collateral advancements in related areas such as nanomaterials synthesis, nanostructured thin film growth, and metal-enhanced fluorescence for biological imaging and sensing.
The educational activities are designed to integrate alternative energy and nanotechnology research into the education of graduate, undergraduate, and high school students, as well as high school teachers. The first broader impact on education will be the integration of alternative energy and nanotechnology into the undergraduate and graduate curriculum. The second broader impact will result from the involvement of undergraduate and high school students and teachers in chemical and materials research. The third broader impact is the education of the public on general energy concepts, especially in the context of current energy related issues, through a set of modules in a web-based video format.
