Seminars

2012-10-30

Dislocation-Driven Nanomaterial Growth and Solar Energy Conversion Using Earth-Abundant Semiconductor Nanomaterials

Prof. Song Jin, University of Wisconsin-Madison - Dept. of Chemistry
Speaker's Website
Prof. Guozhong Cao, Dept. of Material Science and Engineering

I will first discuss a nanowire formation mechanism that is different from the well-known vapor-liquid-solid (VLS) growth, in which axial screw dislocations provide the self-perpetuating steps to enable 1-dimensional (1D) crystal growth. This mechanism was initially found in hierarchical nanowire structures with helically rotating branches resembling �pine trees�. Dislocations can further result in the spontaneous formation of nanotubes, 2D plates, and other morphologies. Many recently established new examples show that dislocation-driven growth is general to many materials grown in vapor or solution phase. We have used classical crystal growth theory to guide the rational design of dislocation-driven nanomaterial growth. These discoveries can create a new dimension in the rational design and synthesis of nanomaterials. They have enabled the scalable and low-cost synthesis of earth-abundant nanomaterials for large scale renewable energy applications, such as in solar and thermoelectric energy conversion, and nanostructured battery electrodes. This will be illustrated by the growth of 1D nanomaterials of earth-abundant semiconductors, such as hematite (?-Fe2O3), pyrite (FeS2), and cuprous oxide (Cu2O). The photoelectrochemical properties of these nanomaterials and various doping and nanostructuring strategies using 3D hierarchical nanocomposites are investigated to overcome the challenges of light harvesting and carrier collection.