When it comes to renewable energy, solar power is a forerunner for many countries. This popularity is due to the host of benefits that solar brings including ease of installation, panel efficiency and affordability.

Yet, like with all renewable energy sources, improvements need to be made to solar to make it a truly viable alternative to fossil fuels. One emerging technology which is promising to help do this is tandem solar cells. 

In this article, we explore what tandem solar cells are, how they are/can be applied and their benefits.  

Understanding Tandem Solar Cells

There is a clue in the name of tandem solar cells that helps us understand how they work. 

The basic principle behind this technology is the combining of two different materials in layers. This combination typically allows the sell to capture a broader range of sunlight. 

For example, the most common type of tandem solar cell combines perovskite cells with silicon cells. The perovskite cells help trap high-energy light (600–850 nanometers on the light spectrum - think ultraviolet), whilst the silicon cells help trap low-energy light (400-700 nanometers on the light spectrum - the infrareds). This drastically increases the amount of the sun's energy which can be caught and turned into electricity. 

In fact, one recent study found that perovskite-silicon tandem cells could increase solar panel efficiency by 50 to 75 percent compared to current, common PV solar panels. 

Types of Tandem Solar Cells

We have already mentioned how perovskite-silicon tandem cells are the most common, but they aren’t the only type of tandem cell. 

Perovskite-CIGS is another promising tandem cell technology which combines perovskite cells with Copper Indium Gallium Seledine (CIGS) cells. This cell works in a similar way to perovskite-silicon, with the perovskite cells capturing high-energy light and the CIG cells capturing low-energy light. One study predicts that perovskite-CIGS cells could increase the efficiency of solar panels by 29.7%. 

Although perovskite-silicon clearly wins the battle for the biggest increase in efficiency, there are benefits to both of these approaches to tandem solar cells. 

Perovskite-CIGS tandems benefit from the stability and scalability of CIGS technology. On the other hand, perovskite-silicon tandems leverage well-established and commercially mature silicon technology.

Silicon-heterojunction (SHJ) solar cells take a slightly different approach. They combine a thin layer of amorphous silicon with crystalline silicon. The interface between these two laters forms a heterojunction that separates photogenerated charged carriers. In turn, this improves cell performance and generates higher efficiency. 

Ultimately, all solar tandem cells need further development and research to understand which one offers the best option in terms of performance, stability and cost-effectiveness. 

Benefits and Applications

The primary benefit of tandem solar cells is obvious - increased energy yield. 

Using tandem cells offers greater access to solar energy, making it more viable as a replacement for fossil fuels. By increasing the efficiency of solar panels, tandem solar cells can also help minimise the space needed for solar arrays. This can free up land for other uses such as housing, crop growth or conversation. 

Fewer panels mean fewer material requirements. This helps reduce both costs and the negative impact that manufacturing solar panels can have on the environment. 

Tandem solar cells have many applications across residential, commercial and utility-scale solar installations. For example, a drastic increase in efficiency means that solar panels can be considerably smaller. This opens the door for the wider application of Building-Integrated Photovoltaic Panels (BIVP) such as in solar roof tiles. Commercially, businesses can also start to integrate smaller panels into portable electronics, making them self-sufficient. 

Challenges and Future Outlook

Without a doubt, tandem solar cells are a positive emerging technology for the solar industry, but they aren’t without their challenges. 

For example, the manufacturing process associated with combining two cells in layers is a complex one. This can increase their cost and make the manufacturing process longer. The layering of cells can also cause issues in terms of stability. Further testing will be required in order to ensure the longevity of cell structures such as perovskite-silicon and perovskite-CIGS. 

New materials being used in tandem solar cells may also not be considered as environmentally friendly as the current cells' structures. This could lead to more efficient technologies being deemed unsuitable in the search for suitable replacements for fossil fuels. 

Tandem Cell Success

Even though manufacturing is complex, we are already seeing companies starting to produce commercially viable tandem cells. In fact, South Korean company Qcells has recently announced the world's first production line dedicated to perovskite-silicon tandem solar cells. 

This is a major step in the production of tandem cells. The company plans to invest a massive US$100 million into moving the next generation of solar cell tech from the research/academic stage into production. 

Ultimately, this could mean that we will see tandem solar cells being applied widely within the next few years. 

Tandem solar cells: Summary 

We can see that tandem solar cells are an exciting emerging technology in the solar industry. The use of these new cell types has the potential to drastically increase the efficiency of solar panels, making them even better at generating electricity. In turn, this will help make solar a forerunner in the race to replace fossil fuel-powered energy production. 

With considerable investment being focused on tandem solar cell research, it is likely that we will start to see a drastic spike in development in this area in the coming years.

The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag

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