Monocrystalline vs Polycrystalline Solar Panels

The article explains the difference between the two major crystalline silicon (C-Si) solar panels.

Mono means one while poly means many - just as in romantic relationships. 

But what do they mean in terms of solar panels? 

The difference starts during the process of creation.  Monocrystalline silicon is created by slowly pulling a monocrystalline silicon seed crystal out of melted monocrystalline silicon using the Czochralski method to form an ingot of silicon.  A seed crystal is a small piece of silicon which is used as a foundation for the molten molecules.  By having a foundation, the molten molecules are able to connect together faster to form an ingot.  While the seed crystal is being withdrawn, it is rotated slowly and temperature is lowered slowly.  This helps form the cylindrical shape until it has the right diameter which is when temperature remains constant. 

 

 

Polycrystalline silicon is made through a simpler method.  Instead of going through the slow and more expensive process of creating a single crystal, molten silicon is just put into a cast and cooled with a seed crystal.  By using the casting method, the crystal surrounding the seed isn’t uniform and branches into many, smaller crystals, thus "polycrystalline". 

 

 

If the videos above, posted by youtube user globalchampion, are more information than required, here are the bullet point differences between the two methods:

  • Price

Monocrystalline solar cells cost more than polycrystalline for the same size.

  • Efficiency

Monocrystalline cells have a higher efficiency than polycrystalline cells due to the structure being made from one large crystal as opposed to many small ones.  In addition to having an overall better efficiency, monocrystalline panels can perform up to 10% better than polycrystalline panels in high ambient temperatures.

  • Size

Since monocrystalline panels are more efficient per area, the size of the solar panel is less than a polycrystalline solar panel for the same wattage.  If you are limited on size and want to get the most energy possible, monocrystalline panels are the better choice. 

  • Looks

In terms of looks, monocrystalline panels have a nice uniform color and have a more circular cell shape.  Polycrystalline cells are in squares and have inconsistencies in the color sort of like granite. 

  • Longevity

Even though a monocrystalline panel has the potential to last up to 50 years, most warranties only go up to 25 years which polycrystalline panels are able to reach just fine.

Overall, the production process for monocrystalline silicon is mature, and the process for polycrystalline in still maturing. As purity and process tolerances for polycrystalline Si improves, the performance gaps between the two are narrowing.

Take a look at our monocrystalline panels.

Take a look at our polycrystalline panels.

Comments

Great article. I've always wondered what a polygamus crystal was - now I know.

Take a look at the specs of the new Suntech Pluto245-Wde Solar Panel. 

To me it appears that SunTech's new poly Pluto technology lets this poly panel exceed the performance of most mono panels offered today.

Your thoughts?   

dorcse,

This looks like a perfect example of the author's (keventai) statement that the prformance gap between the two technologies seems to be narrowing...

I heard that mono panels have a "burn in" period; that within the first 12 to 24 months, their charge outputs drop to a lower, more permanent level.  I had heard this was one of the problems with sizing early systems and why so many early adopters were frustrated by the long-term performance of their heavy-panel monocrystalline systems.  Any thoughts?

Tinman200,

I've never witnessed a Burn-In period for production Mono panels. I know that very early modules were composed of cells that were sawn fairly thickly by today's standards and that they could experience higher thermal gain (maybe) and thus greater thermal degredation. I'm pretty sure you aren't talking about the Staebler-Wronski effect, because it's related to Amorphous cells:

Staebler–Wronski effect

The efficiency of an amorphous silicon solar cell typically drops during the first six months of operation. This drop may be in the range from 10% up to 30% depending on the material quality and device design. Most of this loss comes in the fill factor of the cell. After this initial drop, the effect reaches an equilibrium and causes little further degradation. The equilibrium level shifts with operating temperature so that performance of modules tend to recover some in the summer months and drop again in the winter months.[4] Most commercially available a-Si modules have SWE degradation in the 10–15% range and suppliers typically specify efficiency based on performance after the SWE degradation has stabilized. In a typical amorphous silicon solar cell the efficiency is reduced by up to 30% in the first 6 months as a result of the Staebler–Wronski effect, and the fill factor falls from over 0.7 to about 0.6. This light induced degradation is the major disadvantage of amorphous silicon as a photovoltaic material.*

*From Wikipedia

 

  1. 4^ Uchida,Y and Sakai,H. Light Induced Effects in a-Si:H Films and Solar Cells, Mat. Res. Soc. Symp. Proc., Vol. 70,1986
  2. 5^ Nelson, Jenny (2003). The Physics of Solar Cells. Imperial College Press.

Never mind.  Civic Solar does not even stock the Suntech Pluto245-Wde.

They list it on their website as if it is available.  But when you e-mail them they try to sell you a non-SunTech panel instead. 

Thanks for all of your feedback.  We do have the Suntech Pluto245-Wde available not sure what the confusion was.  Suntech is moving to the 240W version for the remainder of the year.    Feel free to contact us and we can get you updated pricing for your project.  

Best regards-   Michael


I recall hearing that polycrystalline cells fare slightly better in partial shading situations than monocrystalline. Can anyone comment on this? Thanks, Art
Art,
I don't think you would see any difference in the built environment. What kind of shading are you referring to? Clouds or obstructions? In cloudy conditions, Mono is anecdotally better (in my experience).  For obstructions, it's more a factor of the cell strings and how the module diodes are arranged in relation to the amount and direction of the shading.

I think Amorphous or Thin Film modules beat both for shade resistance, even though they are less efficient overall.