Polycrystalline Solar Panels

A polycrystalline solar panel (sometimes called multicrystalline) is made from polycrystalline solar cells like this one:

A poly cell that makes up polycrystalline solar panels

Polycrystalline solar cells are cheaper to make than monocrystalline cells. To make a polycrystalline ingot, you simply melt a load of silicon and then pour the molten liquid into a big box where it solidifies; creating an ingot that looks like this:

A polycrystalline ingot
Picture: pveducation.org

This is a lot simpler than growing a monocrystalline ingot on a multi million dollar crystal growth machine from a tiny seed over days or weeks until you have a beautiful shiny cylinder made of a single crystal of silicon!

The big ugly polycrystalline ingot is cut into square blocks, like these ones being handled by our German lady friend:

Sawn polycrystalline ingots
Picture: Schott solar

These blocks are then sliced up into very thin, square wafers like this.

polycrystalline wafer
Picture: Schott Solar

To convert this wafer into a solar cell, they have to be processed in almost exactly the same way as monocrystalline wafers, i.e. they are cleaned, textured, diffused and anti-reflection coated before the electrical conductors are printed on.

The only real differences between a mono and polycrystalline solar cell are:

1) Polycrystalline solar cells are perfectly square
2) Polycrystalline solar cells have grain boundaries (clearly visible) which slightly reduce the solar efficiency by making it a bit harder for the electrons to flow.

So does (2) mean polycrystalline solar panels are inferior to monocrystalline? Not really, because the multicrystalline cells' square shape means that when they are laid up into the panel, there is no wasted space. This makes the efficiency of a typical polycrystalline solar panel almost identical to a typical monocrystalline module these days.

Here's a finished polycrystalline solar panel:

polycrystalline solar panel

 

If you want to see a list of polycrystalline solar panels on the Australian market along with independent performance figures, then you can use my solar panel comparison chart, just select only “polycrystalline” in the options and hit "GO":

how to see only multicrystalline solar panels in my compare tool

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