Marisa Di Sabatino

Surface Passivation Properties of

Atomic layer deposited hafnium oxide is shown to provide good surface passivation of low resistivity, n-type crystalline Si wafers after a low temperature anneal. The surface passivation is related to a fixed negative charge, as well as an excellent interface with the crystalline Si wafer. In this paper, the influence of four deposition parameters on the HfO2 passivation properties, namely precleaning, precursors, deposition temperature, and postannealing temperature, is discussed. Minority carrier lifetimes of 1.9 ms (surface recombination velocity (SRV) 7.7 cm/s) on float zone n-type wafers and 1.7 ms (SRV 11 cm/s) on Czochralski n-type wafers, under optimized deposition conditions and a postannealing process, have been measured. A significant improvement of the surface passivation is observed after 100 h light soaking, resulting in a carrier lifetime of 2.5 ms. Fitting of the results by a two-defect charge trapping/detrapping model indicates that additional light-induced negative charges enhance the field effect passivation, which is also consistent with the experimental results. Due to its high refractive index and the obtained good surface passivation of Si wafers, HfO2 has a great potential as a surface passivation material, e.g., in the fabrication of high-efficiency Si solar cells.

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Silicon is the dominating material in solar cells. Monocrystalline and multicrystalline cells have approximately equal market shares and are produced from wafers, cut from single crystals produced by Czochralski (CZ) pulling or from polycrystalline ingots made by directional solidification, respectively. The present paper reviews how demands for lower cost, better yield, higher efficiency and use of less pure silicon in solar cells are addressed by advanced solidification processing. In monocrystalline solar silicon, careful growth control results in less point defects, and better efficiency. Continuous- or semi-continuous CZ growth processes are being developed for better productivity and lower cost. In multicrystalline solar silicon, extended defects such as dislocations and grain boundaries decrease efficiency, particularly in combination with new, less expensive, but more contaminated silicon feedstock. This problem is addressed by control of nucleation and growth of ingots with larger grains, preferred grain orientation and lower dislocation density.

Thin Film on n-Type Crystalline Si

In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditio ...

Solidification of Silicon for Solar Cells

A study of the spatial occurrence of iron precipitation in a high performance multicrystalline silicon (HPMC-Si) sample is presented. The separated effects of grain-boundaries, sparse intra-granular dislocations, and dislocation clusters are investigated by combining the Fei imaging method with glow discharge mass spectroscopy, electron backscatter diffraction, and two iron precipitation models. While the area-averaged precipitation at grain boundaries is relatively minor, almost the whole iron precipitation occurs within the grains, despite the very low intra-granular dislocation density. The fraction of non-precipitated iron in the studied HPMC-Si material was found to be one to two orders of magnitude higher than that reported previously for standard materials.

Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing

The surface passivation quality of plasma-enhanced chemical vapor-deposited silicon oxynitride/silicon nitride (a-SiO

High performance multicrystalline silicon: Grain structure and iron precipitation

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Electronic Properties of a-SiO

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