Solar Cells from Silicon and Germanium Nanocrystals Inks

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CBET-0756326 KortshagenSilicon-based solar cells are the dominant photovoltaic technology with a market share of ~90% of all cells manufactured in 2005. However, the cost of electricity from solar cells is still by a factor of 5-10 higher than that of electricity from fossil fuels. The goal this project is to perform the basic research required to develop efficient, low-cost solar cells based on a new paradigm of manufacturing solar cells from solution using silicon (Si) and germanium (Ge) nanocrystal inks. Solution processing of solar cells by known printing techniques such as ink-jet printing is believed to have the potential to lower the solar cell manufacturing cost by up to a factor of ten. Moreover, nanocrystals have exciting properties such as size-tunable absorption and the ability to efficiently generate multiple electron-hole pairs on absorbing only a single photon, which may ultimately lead to more efficient solar cells than devices made from bulk material. Additional advantages of Si and Ge nanocrystals lie in their non-toxicity, lack of environmental hazard, stability, and abundance. Hardly any other nanocrystal material offers this range of desirable attributes.Research under this grant has four thrusts: 1) The development of routes for the solution-phase assembly of conductive films from Si and Ge nanocrystal inks; 2) the electrical doping of Si and Ge nanocrystal films and the study of their electrical properties; 3) the detailed investigation of the basic optical absorption properties of Si and Ge nanocrystal inks and of solution-processed conducting films thereof; and 4) the evaluation of the properties of Si and Ge nanocrystal films in actual solar cells. The intellectual merit of this project lies in new methods to form conductive films from Si and Ge nanocrystals that will be developed through the proposed research. This project will also elucidate how electrical doping of Si and Ge nanocrystal films can be achieved and how doping affects the electronic and optical properties of the films. Finally it will develop, for the first time, solar cells made exclusively from Si and/or Ge nanocrystal inks.The broader impacts of this project are significant. The proposed research may ultimately enable a new approach to the manufacture of low-cost nanocrystal solar cells, whose efficiencies may potentially exceed those of bulk material cells. Leverage provided by an NSF-IGERT for "Nanoparticle Science and Engineering" will enhance educational opportunities for graduate students supported by this project. The involvement of graduate students and minority undergraduate students will foster the integration of research and training, and the participation of underrepresented groups. Outreach collaboration with the Science Museum of Minnesota will communicate results of this research to a broad public. A close collaboration with an industrial partner will ensure rapid knowledge transfer to industry.