Monocrystalline vs Polycrystalline Solar Panels

The rise in popularity of solar panels has resulted in several types of solar panels being developed. Each uses slightly different materials or technology to achieve the same goal: convert the sun’s energy into useable electricity. Of these, monocrystalline and polycrystalline solar panels are by far the most popular choices.

Both monocrystalline and polycrystalline solar panels consist of silicon-based photovoltaic (PV) cells. The difference is in the form of silicon within the PV cell. As their names suggest, monocrystalline PV cells are made using a single silicon crystal, whereas polycrystalline PV cells contain many silicon crystals.

The difference in their crystalline structure affects their performance, which can make them better suited to different installation locations.

At A Glance: Monocrystalline vs Polycrystalline Solar Panels

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The table below contains a brief comparison of monocrystalline solar panels vs. polycrystalline solar panels, including efficiencies, cost and lifespan.

Factor	Monocrystalline	Polycrystalline
Efficiency	15 to 23% efficiency	13 to 16% efficiency
Power Output Per m2	Over 160 watts	125 to 150 watts
Cost	£1 to £1.50 per watt ($1.20 to $2)	£0.90 to £1 per watt ($1 to $1.20)
Lifespan	25+ years	25+ years
Appearance	Black hue	Blue hue
Temperature Coefficient	-0.3 %/°C to -0.4 %/°C	-0.37 %/°C to -0.5 %/°C

Monocrystalline Solar Panels

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Monocrystalline solar panels are the most commonly installed solar panels. They are made from a single silicon ingot which is formed via the Czochralski (CZ) method, also known as crystal pulling.

The CZ method uses a seed crystal which is a rod of pure crystal silicon. The seed crystal is placed into a bath of molten silicon and slowly rotated. This creates a slight temperature drop which causes the molten silicon to crystalize onto the seed crystal.

The structure of the formed silicon crystal is identical to that of the seed crystal and is made up of perfectly organised molecules. The formed ingot is then cut into thin wafers to be used in solar panels and their surfaces are polished to allow them to refract more sunlight.

Electrons can flow more freely around ordered molecular structure hence monocrystalline solar panels have a higher efficiency than polycrystalline solar panels. Most monocrystalline solar panels have a power output above 320 watts.

Polycrystalline Solar Panels

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Polycrystalline solar panels are made from many fragments of disorganised silicon crystals.

Crystalline silicon ingots are formed by cooling molten silicon. The silicon naturally forms a fragmented, disordered structure as it cools. The formed silicon ingots are then cut into thin wafers that are used to make polycrystalline solar panels.

The disorganised molecular structure within the wafers is trickier for electrons to navigate through, hence polycrystalline solar panels have a lower efficiency than monocrystalline solar panels. Their typical power output it between 250 and 300 watts, although some polycrystalline solar panels can achieve higher.

The process of making polycrystalline solar panels is much easier meaning they can be manufactured quicker and less expensively.

How Do Monocrystalline and Polycrystalline Solar Panels Compare?

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At first glance, monocrystalline and polycrystalline solar panels may look the same but they actually differ in several performance factors including their efficiency, cost, power output. Their key differences are summarised below.

Efficiency

Solar panels generate electricity when sunlight causes electrons within the panel to become free flowing, producing an electrical current.

In polycrystalline solar panels, grain boundaries exist between the fragmented silicon crystals. These cause resistance against the free-flowing electrons within the solar cell. Electrons waste energy by overcoming this resistance, hence less energy is available to be converted into usable electricity.

The single crystal structure of monocrystalline solar panels makes them more efficient. This is because there are no grain boundaries for the electrons to travel through, allowing them to flow more freely and retain more of their energy.

The best monocrystalline solar panels have an efficiency of around 23%, which is considerable higher than the 14-16% achieved by most polycrystalline solar panels.

Overtime, the efficiency of both types of solar panels is likely to increase as research uncovers new materials such as perovskites that can better capture our sun’s energy.

Cost

Monocrystalline solar panels are more expensive to manufacture due to the extra steps needed to achieve the organised molecular structure. This means that the cost to install monocrystalline solar panels will be higher upfront.

Polycrystalline solar panels are cheaper to install but they are less efficient. This means that more panels are required to achieve the same energy output compared to monocrystalline solar panels. For areas with limited space available, it can be more cost effective in the long-run to install monocrystalline solar panels and maximise lifetime energy output.

Lifespan

Both polycrystalline and monocrystalline solar panels are highly durable. They are designed to withstand a wide range of weather conditions that may occur over their long lifespan.

As a result, both polycrystalline and monocrystalline solar panels can continue producing energy for 25 years or more. This is also the typical length of warranty given by solar panel manufacturers.

Appearance

The different crystal structures within polycrystalline and monocrystalline solar panels causes them to have slightly different appearances.

Monocrystalline solar panels are black and have a more uniform appearance. Polycrystalline solar panels have a blue hue which may become more obvious in bright sunlight.

Temperature Coefficient

Like most electrical equipment, solar panels become less efficient as the temperature increases. The temperature coefficient is an important metric which describes how well a solar panel will work in warm temperatures.

It is expressed as the percentage decrease in output for every 1°C increase in temperature over 25°C. The efficiency of solar panels is tested at 25 °C hence this is used as the reference point.

This means that a solar panel with a temperature coefficient of -0.4 %/°C will decrease in efficiency by 0.4% for every 1°C above 25°C. Therefore, a lower percentage represents a better performing solar panel.

Most polycrystalline solar panels have a temperature coefficient between -0.37 %/°C to -0.5 %/°C. Monocrystalline solar panels have a slightly lower temperature coefficient between -0.3 %/°C to -0.4 %/°C. This means that monocrystalline solar panels will perform better in warmer climates.

Further Reading

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