Solar power is the fastest-growing energy technology — and by a wide margin. In 2023, more than twice as much new electricity generation from solar was added globally as from coal. In fact, according to a recent report, both solar and wind are growing faster than any other source of electricity in history.

Much of this encouraging breakthrough in solar energy is thanks to silicon. This semiconductor comprises up to 95% of all solar panels across the world. However, manufacturing high-efficiency solar cells (over 25%) requires pure silicon that is heated to over 900 degrees Celsius to remove defects. It also has a fixed bandgap (range of light it can absorb) which is not ideal.

A new material for solar cells

In contrast, perovskite (a calcium titanium oxide mineral) is much better at absorbing light than crystalline silicon and can even be ‘tuned’ to use regions of the solar spectrum largely inaccessible to silicon photovoltaics. Perovskite holds a much better tolerance for defects and can function well with impurities and imperfections. Perovskites can also be produced more easily and more flexibly. In theory, solar panels made from this mineral could be made much cheaper than their silicon counterparts.

These cells have seen a dramatic rise in efficiency in recent years, jumping from a mere 3% in 2009 to over 25% today. This leapfrog in efficiency has captured the attention of researchers and industry leaders alike, raising hopes for a future powered by perovskites.

The problem is that naturally occurring perovskite is rare, while synthetic versions of perovskite have fleeting durability measured in months. Additionally, perovskite is rather fragile, prone to chemical and thermal damage.

But a breakthrough at Rice University could finally tip the scale in favor of perovskite to topple silicon’s dominance in the solar sector. The new study highlights a novel method to synthesize formamidinium lead iodide (FAPbI3) — the type of crystal currently used to make the highest-efficiency perovskite solar cells — into ultrastable, high-quality photovoltaic films. These films demonstrated remarkable stability, with a mere 3% decrease in efficiency after over 1,000 hours of operation at 85 degrees Celsius. This high temperature typically causes formamidinium iodide-based solar cells to collapse.

“Right now, we think that this is state of the art in terms of stability,” said Rice engineer Aditya Mohite, who is one of the most experienced perovskite researchers in the world. “Perovskite solar cells have the potential to revolutionize energy production, but achieving long-duration stability has been a significant challenge.”

Stability in Perovskite Solar Cells

The key to this breakthrough lies in “seasoning” the FAPbI3 precursor solution with specially designed two-dimensional (2D) perovskites. These 2D perovskites act as templates, guiding the growth of the bulk/3D perovskite and enhancing the crystal lattice structure’s stability.

The researchers explain that FAPbI3, although chemically stable, is structurally unstable. By using 2D perovskites as templates, they improved both the efficiency and durability of the FAPbI3 films. The addition of well-matched 2D crystals facilitated the formation of high-quality FAPbI3 crystals, which showed less internal disorder and a stronger response to illumination.

Solar cells with these 2D templates outperformed their counterparts. They maintained stability even after 20 days of generating electricity from sunlight. This stability was further enhanced by adding an encapsulation layer, bringing perovskite solar cells closer to commercial viability.

This advancement could transform photovoltaic technologies by reducing manufacturing costs and enabling lighter, more flexible solar panels. Unlike silicon-based solar cells, perovskite films can be processed at lower temperatures, allowing for production on plastic or flexible substrates, further driving down costs.

“It should be much cheaper and less energy-intensive to make high-quality perovskite solar panels compared to high-quality silicon panels, because the processing is so much easier,” said Isaac Metcalf, a Rice materials science and nanoengineering graduate student and a lead author on the study.

“If solar electricity doesn’t happen, none of the other processes that rely on green electrons from the grid, such as thermochemical or electrochemical processes for chemical manufacturing, will happen,” Mohite said. “Photovoltaics are absolutely critical.”

The findings appeared in the journal Science.