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jahono's avatar

Effects of Grain Orientation in Solar Cells?

Asked by jahono (145 points ) January 5th, 2010

In n-p solar cells (photovoltaic) does the orientation of the doped silicon crystals (obviously in multi-crystal layers) have any effect on the productivity of the cell?

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9 Answers

jahono's avatar

THanks chazmaz, that absrtact measures the stress tensors within the cell. I don’t have access to J. of App. Physics to read the whole thing either. I don’t know much about n-p doping to generate the solar effect (? – not sure what the effect is actually called) , can you tell me if its related to stress tensors?

jahono's avatar

this link says “effect of particular grain boundaries on possibly reducing the photoresponse of a cell according to the dislocation content” (where dislocations are around grain boudaries due to merging of grains of different orientations). This link says the same, and is an invention to reduce the effect of the grain boundaries.

The process to make it favours a certain orientation <110> (crystallographic planes miller indices)

For Monocrystalline crystals, link says “Generally, for photovoltaics, the crystal is grown with a prefered orientation so that the wafers which are sliced from the crystal perpendicular to the growth axis have surfaces parallel to the {100}” but doesn’t go on to say why.

link says “The silicon is tested for crystallographic orientation”

You can buy it with (100) orientation.

Still not sure which is best

stranger_in_a_strange_land's avatar

Only in a grown-crystal types of photovoltaic cells. These are favored for highest efficiency (current per unit area). The amorphous and film-type PV’s don’t have a strong dependency on internal structure, only orientation toward the light source. In higher lattitudes, the n-p silicon arrays have to be moved almost hourly to take best advantage of their higher efficiency (tracker mounts).

jahono's avatar

THanks @stranger_in_a_strange_land, when you say orientation towards the light source are you talking about light scattering and reflection etc diminshing the performance?

stranger_in_a_strange_land's avatar

@jahono Yes, the array has to be as close as possible to perpendicular to the suns rays. In the winter at high lattitudes there is less energy available (solar radiation passing through much more atmosphere), so automatic tracking allows the collection of as much of it as possible. The cost-effectiveness of this is questionable and the tracker equipment I use (Zomeworks) has been out of production for some years. I tend to look at it as every kilowatt I grab from the sun is that much less carbon footprint I leave, machts nicht on the cost, I paid for the equipment 15+ years ago.

CMaz's avatar

“I paid for the equipment 15+ years ago.”

Did it pay for itself? And if so. How long did it take?

stranger_in_a_strange_land's avatar

It’s repaid itself, but with a lot of effort on my part. I also run wind turbines and a diesel generator. I’m off-grid.

CMaz's avatar

@stranger_in_a_strange_land – You are the man!

To be off the grid. :-)

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