25 March 2013 Effect of grain boundary on nanoscale electronic properties of hydrogenated nanocrystalline silicon studied by Kelvin probe force microscopy
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Abstract
Hydrogenated nanocrystalline silicon (nc-Si:H) based alloys have strong potential in cost-effective and flexible photovoltaics. However, nc-Si:H undergoes light induced degradation (LID), which degrades the device efficiency by over 15%. The microstructural processes responsible for the LID are still under debate. Several recent studies suggest that the generation of metastable defects at grain/ grain-boundary (GB) interface enhances density of traps, which limits the charge collection efficiency. Conventional characterization techniques can measure transport properties such as electrical conductivity or carrier mobility averaged over large sample volumes. However, nanoscale characterization tools, such as Scanning Kelvin probe Force Microscopy (KFM), reveal local electronic properties of grains and GBs which may lead to better understanding of microscopic process of metastability. The optoelectronic properties of nc-Si:H films were measured in dark and under illumination to study the effect of LID at the nanoscale. The surface potential and charge distribution were measured in as-deposited and photo-degraded samples using a custom-designed scanning probe microscopy tool installed in an environment controlled glove-box. Photodegradation resulted in an upward bending of the conduction band edge, suggesting accumulation of photo-generated charges at GBs. This effect is attributed to the generation of acceptor like defects (traps) at GBs during illumination. Density of defects is estimated from grain/GB width and absolute value of band bending.
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Rubana Bahar Priti, Rubana Bahar Priti, Sandeep Mahat, Sandeep Mahat, Venkat Bommisetty, Venkat Bommisetty, } "Effect of grain boundary on nanoscale electronic properties of hydrogenated nanocrystalline silicon studied by Kelvin probe force microscopy", Proc. SPIE 8620, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices II, 862020 (25 March 2013); doi: 10.1117/12.2005367; https://doi.org/10.1117/12.2005367
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