Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Energy Harvesting & Storage Monday Sessions
       Session EH-MoM

Invited Paper EH-MoM1
Thin Film Solar Cells from Colloidal Nanoparticle Dispersions

Monday, December 8, 2014, 8:40 am, Room Lehua

Session: Nano-based Approaches for Photovoltaics
Presenter: Eray Aydil, University of Minnesota
Authors: E. Aydil, University of Minnesota
B. Chernomordik, University of MInnesota
N. Trejo, University of Minnesota
Correspondent: Click to Email

The global installed capacity to generate electricity using solar cells has doubled every 2.5 years since 1975, an exponential growth similar to the Moore’s law which states that the number of transistors on a computer chip doubles every 2 years.1 Maintaining this aggressive Moore-like growth requires sustainable, high-throughput low-cost production of thin film solar cells. Copper zinc tin sulfide (Cu2ZnSnS4 or CZTS), copper zinc tin selenide (Cu2ZnSnSe4 or CZTSe) and their alloys (Cu2ZnSn(SxSe1-x)4 or CZTSSe) are emerging as promising solar absorber materials for thin-film solar cells because they are comprised of earth abundant elements and can potentially help increase the solar electricity production to terawatt levels without the concerns associated with the toxicity and low abundance of the elements in the current commercial thin-film solar cells. A potentially high-throughput and low-cost approach to making thin polycrystalline CZTSSe films is through annealing of coatings cast from colloidal dispersions (inks) of CZTS nanocrystals in sulfur and/or selenium vapor. In this way, the nanocrystal coatings are transformed into polycrystalline films with micrometer size grains, a suitable morphology for making solar cells. The transformation of the nanocrystal coating to a polycrystalline coating is driven by the high surface area of the nanocrystals and, consequently, the high total surface energy of the nanocrystal coating. This approach is well suited for high throughput low-cost roll-to-roll manufacturing. However, many scientific and technical challenges remain. In this talk we will review the advances made towards this end and the remaining challenges. Specifically, we will describe our most recent findings on the effects of sulfidation/selenization time, temperature, sulfur and selenium vapor pressures, presence of alkali and carbon impurities on the microstructure of CZTSSe films.

1 D. J. Norris and E. S. Aydil, “Getting Moore from Solar Cells,” Science 338, 625-626 (2012).