Photovoltaics

METAL FINGERS ON GRAIN BOUNDARIES IN MULTICRYSTALLINE SILICON SOLAR CELLS

Rita Ebner^{a 1}, Michael Radike^a, Viktor Schlosser^b and Johann Summhammer^{a 2}

^a Atominstitut of the Austrian Universities, Stadionallee 2, A-1020 Vienna, Austria
^b Instiute of Material Physics, University of Vienna, A-1090 Vienna, Austria
¹Email: rita.ebner@ati.ac.at, ²Hompage of solar cells group at Atominstitut: www.ati.ac.at/~summweb

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ABSTRACT

We have developed a method of applying a net-like finger grid to the front side of multicrystalline (mc) silicon solar cells, which lies mainly on the grain boundaries (Grain Boundary Oriented Finger grid, GBOF grid). This net has no busbars. It is drawn by a plotter using screen printing paste.
The efficiency of cells contacted in this manner has been tested in a comparative study of pairs and triplets of cells of size 100x100mm² (Bayer) and 103x103mm² (Eurosolare). In the pairs-study pairs of neighbouring wafers of the original ingot were processed into solar cells. One wafer received a GBOF-grid, the other got the same grid rotated by 90 degrees and so had little coverage of grain boundaries. In the triplets study a third neighbouring wafer was added and equipped with a standard H-pattern of the same shading as the GBOF-grid. Many pairs and triplets were made. The pairs study showed that the GBOF-grid gives solar cells with 3.7% more output, on average, under approximately standard conditions. The triplets study shows that the GBOF-grid increases power output by 2.5%, on average, over the standard H-pattern.

Keywords:

multi-crystalline - 1: grain - 2: contact - 3.

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