How efficient are solar panels?

Photovoltaic technology has been around since the 19th century and has made huge advancements since then. How efficient are solar cells in the 21st century?

Solar array on the ISS

The photovoltaic effect was first discovered in 1839 by Alexandre-Edmond Becquerel when he was 19 years old.

Becquerel’s early experiments involved silver and platinum and generated only tiny amounts of electricity. It wasn’t until decades later that the first true solar cell was built using selenium by Charles Fritt in 1883. Those first cells still weren’t very efficient, only converting about 1% of the incoming light into electricity, but were a significant advancement.

Many decades later in 1954, Bell Labs produced the first modern silicon-based solar cell. While there are competing technologies in use, silicon is still the most common material used for solar panels today.

That first silicon cell produced by Bell Labs was a big improvement over Fritt’s selenium-based cell, but still was only about 6% efficient. But research has continued non-stop, and many recent improvements in technology have helped to push the efficiency of consumer-oriented solar panels as high as 23%.

Still, if you nerdishly follow the development of photovoltaic technology, you probably hear about promising new technologies being developed in labs with radically higher efficiencies - up to 47% today.

It’s hard to predict which technologies will break out and hit mainstream adoption, but for now we’ll take a look at what is commonly available on the market now.

What is the highest efficiency polycrystalline silicon solar panel?

Polycrystalline silicon is a lower cost material that is used in budget solar panels. The highest efficiency polycrystalline solar panels you’ll find on the market today are about 20% efficient.

One example is the Canadian Solar HiKu5 polycrystalline panel, which is 20.6% efficient.

Canadian Solar recently announced a breakthrough polycrystalline silicon technology, hitting 23.81% efficiency.

It’s not yet known when Canadian Solar will bring this technology to market, and whether it will be price-competitive with existing monocrystalline panels that are already in this efficiency range. Nonetheless, it’s an exciting development because it promises a significant improvement for polycrystalline silicon.

What is the highest efficiency monocrystalline silicon solar panel?

Monocrystalline silicon is a more expensive material than poly, but it now dominates the residential market due to falling costs.

The current leader in monocrystalline panel efficiency is LG, with their NeON R series panels that hit 22.75% efficiency. However, other premium panel manufacturers aren’t far behind. The SunPower X-Series his 22.73% efficiency, and REC Solar, Silfab, and Canadian Solar aren’t too far behind.

You can see a list of current efficiency leaders in our article on highest efficiency solar panels.

What are the highest efficiency thin film solar panels on the market?

While crystalline silicon panels dominate the market, a small percentage of the solar market (about less than 10%) is taken up by thin-film solar.

Thin-film solar isn’t just one techonology, but a set of technologies using different materials. What they have in common is that thin-film solar cells are flexible and can be deposited on different materials, such as flexible plastics.

Lower cost is a potential advantage, although the vastly larger manufacturing volumes for crystalline solar have so far meant that the price advantage hasn’t materialized yet.

Still, at least one manufacturer is making mass market thin-film solar panels: Arizona-based First Solar.

First Solar makes conventional-sized solar panels using CdTe solar cells. Their Series 6 Plus panels achieves 18.3% efficiency, making them competitive with conventional crystalline solar panels.

What is the highest efficiency solar panel that you can buy?

The panels listed above are what you can get on the market if you’re shopping for solar for your home, or even larger commercial- or utility-scale installations. Millions of these panels are manufacturered and installed globally each year, so they are the best price-per-watt products on the market.

But what if price is no object? What if you have an application where high efficiency is the most important thing? What if you own - a space station?

If you have an International Space Station, a Mars rover, or interplanetary probe, you would turn to a company like Spectrolab, which specializes in just this sort of thing.

They make powerful solar cells that hit an amazing 32.2% efficiency - far higher than any product that you can install on your rooftop.

How does Spectrolab achieve this? They multi-junction silicon solar cells. The type of solar cells in common use are single junction, which means they have a single interface of semi-conducting materials that are designed to capture a single range of light wavelengths.

As you know, white light is a rainbow. The single junction solar panels used on your roof or a utility solar farm can only capture one slice of that rainbow.

However, multi-junction solar cells have multiple layers of semi-conducting materials, each of which is tuned to capture a different slice of that rainbow.

This means that multi-junction solar cells, like the kind that power the International Space Station or the Mars rovers, can use more of the light that hits their surface, which is why Spectrolab cells are about 50% more efficient than even the best solar panels you can buy for your home.

When will I be able to buy super-efficient solar panels for my house?

The price-per-watt of solar panels has dropped by amazing amount over the last few decades. This is partly due to improvements in solar cell technology, but most of this because of manufacturing scale.

With global solar panels manufacturing volumes now being measured in hundreds of gigawatts, its economies of scale that have driven the cost of solar down to the point where it’s often cheaper than fossil fuels.

But these panels are made with venerable single junction silicon cells, not exotic new technologies. Will a breakthrough technology come along soon so that, one day, you might be able to install 30% or even 40% efficient solar cells on your roof?

Maybe. You have to remember that to displace crystalline silicon, a new technology would not only have to have improved efficiency, but would need to be easy and cheap to manufacture. If a new technology can’t be manufactured at low cost, it won’t be able to supplant the massive existing manufacturing infrastructure.

Still - who knows? Photovoltaic technology has come a long way since 1839. You never know what might come next.

For further reading about the history of photovoltaics, check out the links below.

Further reading

https://www.researchgate.net/publication/274961489_Chapter_1_History_of_Solar_Cell_Development

https://www.nrel.gov/docs/fy04osti/33947.pdf

https://www.popsci.com/article/science/invention-solar-cell/

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