Spin Relaxation and the Structure and Dynamics of Defects in Materials

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A joint theoretical and experimental study will be made of defects in materials. Nuclear magnetic resonance (NMR) investigations will be carried out in amorphous semiconductors, hydrogen-metal systems, and in very small samples at high pressures. The NMR measurements will be correlated with studies via infrared spectroscopy, electron scattering, mass spectrometry, electrical conductivity, etc. A principle goal is to examine the role of hydrogen rearrangements in changing the properties of amorphous semiconductors and metallic alloys. The theoretical work still include first principles molecular dynamics simulations of large supercells of amorphous silicon, hydrogenated amorphous silicon, and amorphous silicon with a range of dopants. These experimental and theoretical studies are intended to provide information that will allow a microscopic understanding of degradations of photovoltaic properties which accompany exposure to light of a dark-annealed amorphous hydrogenated silicon film. These degradations currently limit the wide commercial usage of hydrogenated amorphous silicon solar cells.