MONO CRYSTAL CELLS ARE MORE EFFICIENT THAN POLY CRYSTAL CELLS AND
WILL GIVE BETTER PERFORMANCE IN ALL CONDITIONS INCLUDING CLOUDY DAYS
WITH LOW LIGHT CONDITIONS. MONO CELLS ARE DARK IN COLOR, POLY CELLS ARE
LIGHTER BLUE AND SHOW MULTIPLE CRYSTAL FORMATIONS ON THEIR SURFACE.
The lifespan of a monocrystalline cell is a minimum of twenty-five years and can be
more than fifty, making them a worthwhile investment for long term use.
Monocrystalline vs Polycrystalline Photovoltaic Cells
You may have heard the terms monocrystalline and polycrystalline used to describe
photovoltaic cells, but what does that mean and how does it affect a cell’s performance?
The main ingredient in most photovoltaic cells is silicon – the same element that makes
computer chips possible. Silicon is the second most abundant element in the Earth’s
crust, but unfortunately it is normally found in the form of silica (the chemical symbol for
silica is SiO2) – you might know it as sand.
Various methods exist to extract the pure silicon, but the most common is carbothermic
reduction, where the silica is heated to 1700°C in the presence of carbon. As the silicon
cools it forms crystals.
The speed at which the silicon cools is one of the critical factors that determine the
crystal size: the slower the silicon cools, the larger the crystals. With care the silicon can
be extracted as one large crystal. As you might imagine, that’s more difficult, which
means it’s more expensive.
The difference between monocrystalline vs polycrystalline solar cells is simply that one is
produced from a single crystal of silicon and the other is produced from a piece of silicon
consisting of many crystals.
So what is the impact on cell performance?
Since polycrystalline cells contain many crystals, they have a less perfect surface than
monocrystalline cells. This means that they absorb less solar energy and produce less
electricity per square metre. On the plus side, the process of creating the silicon for a
polycrystalline cell is much simpler, so these cells are generally cheaper per square
metre.
On balance, the cost of monocrystalline vs polycrystalline based panels per Watt of
power output works out about the same, but the polycrystalline panels will be larger than
equivalent monocrystalline panels. This is a problem if you have a very limited area
available for the installation, in which case you will want to maximise the power output
per square metre so you might as well buy monocrystal.
Monocrystalline and polycrystalline also look different. Monocrystalline cells will
usually have a perfectly uniform appearance, but polycrystalline cells will appear
“grainy” – think of how a granite worktop looks and you’ll get the idea.