108 High Performance Nanowire Photovoltaic Materials

Wednesday, November 4, 2009: 2:30 PM
Charolais (Camino Real Hotel)
Usha Philipose, Ph.D , Department of Physics, University of North Texas, Denton, TX
This talk will focus on the use of light absorbing nanowires that can function as efficient photovoltaic materials that will substantially reduce the cost of solar cell technology and accelerate the onset of the next generation solar cells. The inherent properties of nanowires allow for engineering of both the energy band structure and oscillator strengths and thus lead to the development of materials that can absorb virtually the entire solar spectrum and convert it into photogenerated carriers. The use nanowires as photovoltaic materials holds promise for significant enhancement of the efficiency of photovoltaic devices. We will consider two material systems: Indium (Gallium) Nitride and Silicon/Germanium. We believe that several of the key issues that exist with traditional photovoltaic materials like Silicon can be addressed by the use of nanostructured materials with improved absorption and improved charge collection efficiency. Absorption of light by materials is governed by two fundamental factors: (a) energy band structure and oscillator strengths and (b) distribution of the electromagnetic modes in frequency and space. Modern nanostructure fabrication techniques allow engineering of both of these aspects. The electronic structure can be engineered to enhance absorption by concentration of oscillator strengths into the frequency region of interest. The electromagnetic mode structure can also be manipulated to increase the effective interaction time between matter and light using ordered structures such as photonic crystal architectures or even using fully disordered dielectrics where multiple scattering can lead to diffusive and thus slow propagation of light.