Metal fingers on grain boundaries in multicrystalline silicon solar cells

We have developed a method of applying a net-like finger grid to the front of multi-crystalline (mc) silicon solar cells, which lies mainly on the grain boundaries (grain-boundary-oriented-finger GBOF grid). This net has no busbars. It is drawn by a plotter, using screen printing paste dispensed through a fine tube. The power output of cells contacted in this manner has been tested in a statistical study of pairs and triplets of cells of size 100 × 100 mm2 (Bayer) and 103 × 103 mm2 (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°, and so had little coverage of grain boundaries. In the study of triplets the third wafer of each triplet was equipped with a standard H-pattern of the same shading as the GBOF grid. In the pairs study, we find that under approximately standard conditions there is an 89% chance that the GBOF grid increases power output over cells with an identical, but 90° rotated, grid, the most probable increase being 2.6%. The triplets study shows that there is an 87% chance that the GBOF grid increases power output over cells with the standard H-pattern, the most probable increase being 2.5%. Copyright Œ 2002 John Wiley & Sons, Ltd.