Review on Ribbon Silicon Techniques for Cost Reduction in PV

Abstract

The shortage of Si feedstock and the goal of reducing Wp costs in photovoltaics (PV) is the driving force to look for alternatives to ingot grown multicrystalline (mc) Si wafers which have the highest share in the PV market. Ribbon Si seems to be a very promising candidate as no kerf losses occur, resulting in reduced Si costs per Wp. In addition, there is no need for the energy consuming crystallization of the ingot and therefore energy payback times can be significantly reduced. The higher defect density in ribbon Si materials has to be taken into account during cell processing, but ribbon materials already commercially available show excellent efficiencies, while for the most promising techniques efficiencies are significantly lower, but very promising. In this presentation an overview of ribbon Si technologies currently under research will be given, based on available data on crystal growth as well as solar cell processing and cell parameters.

State-of-the-art growth of silicon for PV applications

“…3 shows a schematic of some of the ribbon processes currently in use, namely EFG, SR, RGS, and RST. A summary of the process parameters, such as pull speed and throughput, for these ribbon techniques is given in Table 1 [14]. A critical driving parameter in technology development for ribbon methods is the productivity per furnace.…”

Solidification of silicon for electronic and solar applications

“…A summary of the process parameters, such as pull speed and throughput, for these ribbon techniques is given in Table I. 14 A critical driving parameter in technology development for ribbon methods is the productivity per furnace. One of the major drawbacks with ribbon silicon materials is their high defect density and gen- …”

Gas phase considerations for the growth of device quality nanocrystalline silicon at high rate

“…Both bulk Si as well as thin films have increased their markets, however the share of thin film silicon has actually fallen and it is at present around 7%. The efforts towards thinner wafers, especially for HIT type of cells shown by Sanyo for thicknesses down to 70 m [2] and thin cells (50 m) by transfer technology [3] and the progress in ribbon type silicon technology [4] are going to take away some of the advantages of thin film based solar cells as far as material cost is concerned. On the other hand, thin film silicon solar cells have to also compete with other types of thin film materials such as CdTe and CIS.…”