Tandem cells using perovskites and silicon make solar power more efficient and affordable

Research into 'miracle material' perovskite in the past decade is now bearing fruit with more labs crossing the 30 percent barrier for solar cells.
Ameya Paleja
The Bolero PV project in Región de Antofagasta, Chile

Antonio Garcia / Unsplash 

Researchers working on solar panels worldwide now consistently breach the 30 percent energy conversion mark, once considered an important threshold for the technology.

This week alone, two research groups published results showcasing energy conversion efficiencies of 32.5 percent and 31.25 percent, respectively, when using tandem cells.

LONGi, the China-based manufacturer of solar cells, also reported an energy conversion efficiency of 33.5 percent last month.

This significant advance for the technology is expected to make green energy more affordable in the near future.

Solar is already a cost-effective method for harnessing renewable energy and is deployed across large parts of the planet in a bid to move away from fossil fuels.

Countries like China are also co-adopting the technology with other renewable energy approaches, such as hydel power to tide over the intermittency issues.

Earlier this year, a Czech utility company was forced to unplug solar panels at its energy farm after the panels produced more energy than the grid could handle.

Nevertheless, traditional solar panels can convert less than a third of incident light (the light that falls onto the panel) into energy, and scientists have been working to improve these numbers.

Crossing the 30 percent barrier

Conventional solar panels have been built using silicon-based cells, with a theoretical maximum of 29 percent for their energy conversion efficiency.

However, researchers have been experimenting with various materials to overcome this limit and have found some success with perovskites.

Like silicon, perovskites are also semiconductor materials but they can absorb the blue light from the visible spectrum and convert it into electric energy.

Silicon, on the other hand, absorbs red light. By using these two materials in tandem, it's possible to boost the total light absorbed by the panel and cross the 30 percent energy conversion barrier.

Tandem cells using perovskites and silicon make solar power more efficient and affordable
Illustration of a perovskite-silicon tandem cell

Perovskite is usually placed on top of the silicon layer, and these types of solar cells are referred to as perovskite-silicon, or simply 'tandem cells'.

Interesting Engineering has previously reported how researchers have been able to break the energy conversion thresholds using tandem solar cells.

While these were the first few attempts in this direction, they have now become regular in research circles.

Silicon-only solar cells have an energy conversion efficiency of 27 percent under laboratory conditions, which decreases to 24.5 percent in real-world settings.

In real-life situations, tandem solar cells would also convert smaller amounts of incident energy. However, it would still be higher than those of silicon-only cells.

Size matters

The solar industry is racing to adopt tandem cells into their production cycles. The bottleneck, though, is the small size of tandem cells, typically 1 cm x 1 cm (0.39" x 0.39") in size, while silicon cells on commercial solar panels measure 15 cm x 15 cm (5.9" x 5.9").

The size scale-up will likely make tandem cell production much more expensive than silicon-only cells.

However, experts believe that these higher costs will be offset by the increased energy production from the cells, which will further reduce the costs of generating solar energy.

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