New tandem solar cells break efficiency records; they could eventually speed up the way we get energy from the sun

The sight of rooftop solar panels and large energy farms has become commonplace in many parts of the world. Even in the UK, where the weather is grey and rainy, solar power is becoming a major player in electricity generation.

This rise of solar energy is fueled by two major developments. First, scientists, engineers and manufacturers are learning how to make billions of solar panels. Each manufacturing step is meticulously optimized to produce them at very low cost. Second, and most importantly, the constant increase in the energy conversion efficiency of the panels, which measures the amount of sunlight that can be transformed into electricity.

The more efficient the solar panels, the cheaper the electricity. So, how efficient can solar energy be? And will it have an impact on our electricity bills?

Currently commercially available solar panels convert about 20 to 22 percent of sunlight into electrical energy. However, new research published in Nature Researchers have shown that future solar panels could achieve efficiencies of up to 34% by exploiting a new technology called tandem solar cells. The research demonstrates record energy conversion efficiency for tandem solar cells.

What are tandem solar cells?

Traditional solar cells are made from a single material to absorb sunlight. Currently, almost all solar panels are made from silicon, the same material used in microchips. Although silicon is a mature and reliable material, its efficiency is limited to about 29%.

To overcome this limitation, scientists have turned to tandem solar cells, which stack two solar materials on top of each other to capture more solar energy.

In a new report published in the journal Nature, a team of researchers from energy giant LONGi has presented a new tandem solar cell that combines silicon and perovskite materials. Thanks to their improved sunlight capture, the new perovskite-silicon tandem achieved a world-record efficiency of 33.89%.

Perovskite solar materials, discovered less than twenty years ago, have become the ideal complement to established silicon technology. The secret lies in their ability to tune light absorption. Perovskite materials can capture high-energy blue light more efficiently than silicon.

In this way, energy losses are avoided and the overall efficiency of the tandem increases. Other materials, called III-V semiconductors, have also been used in tandem cells and have made it possible to achieve higher efficiencies. The problem is that they are difficult to produce and expensive, so only small solar cells can be manufactured in combination with focused light.

The scientific community is devoting considerable effort to perovskite solar cells. They have maintained a phenomenal pace of development, with efficiencies (for a single cell in the laboratory) increasing from 14% to 26% in just 10 years. These advances have enabled their integration into very high-efficiency tandem solar cells, showing the way forward for scaling photovoltaic technology to the trillions of watts the world needs to decarbonize our energy production.

The cost of solar electricity

The new record-breaking tandem cells can capture 60% more solar energy. This means that fewer panels are needed to produce the same amount of energy, reducing installation costs and the amount of land (or roof) required for solar farms.

This also means that power plant operators will be producing solar energy more efficiently. However, due to the way electricity prices are set in the UK, consumers may never notice a difference on their electricity bills. The real difference comes when you consider rooftop solar installations, where surface area is limited and space needs to be used efficiently.

The price of rooftop solar is calculated based on two key factors. First, the total cost of installing the solar panels on your roof, and second, the amount of electricity they will produce over their 25 years of operation. While the installation cost is easy to come by, the revenue from home solar power generation is a little more nuanced. You can save money by consuming less energy from the grid, especially during times when it is expensive, and you can also sell some of your excess electricity back to the grid.

However, grid operators will pay you a very low price for this electricity, so sometimes it is better to use a battery and store the energy so that you can use it at night. Based on average considerations for a typical UK household, I have calculated how much money consumers would save from rooftop solar based on the efficiency of the panels.

If we can improve panel efficiency from 22% to 34% without increasing the cost of installation, the savings on electricity bills will increase from £558 per year to £709 per year. A 20% increase in cash savings that would make solar roofs extremely attractive, even in a grey and cloudy Britain.

So when can we buy these new solar panels?

As research continues, considerable effort is being made to develop this technology and ensure its long-term sustainability. The record-breaking tandem cells are manufactured in the laboratory and are smaller than a postage stamp. Translating such high performance to surfaces of several square meters remains a huge challenge.

And yet, we are making progress. Earlier this month, Oxford PV, a solar panel manufacturer at the forefront of perovskite technology, announced the first sale of its new tandem solar panels. They have successfully addressed the challenges of integrating two solar materials and making panels durable and reliable. While still a long way from 34% efficiency, their work shows a promising path for next-generation solar cells.

Another consideration is the sustainability of the materials used in tandem solar panels. Mining and processing some of the minerals in solar panels can be extremely energy intensive. In addition to silicon, perovskite solar cells require elements like lead, carbon, iodine, and bromine to function properly. Combining perovskite and silicon also requires rare materials containing an element called indium, so there is still a lot of research to be done to solve these challenges.

Despite the challenges, the scientific and industrial community remains committed to developing tandem solar devices that could be integrated into almost anything: cars, buildings and airplanes.

Recent developments in high-efficiency perovskite-silicon tandem cells point to a promising future for solar energy, ensuring that solar continues to play a larger role in the global transition to renewable energy.

This article is republished from The Conversation under a Creative Commons license. Read the original article.