How do you protect perovskite solar cells from frost and heat? These modules are particularly efficient, especially in tandem with silicon solar cells. However, they react sensitively to temperature changes and therefore lose capacity very quickly. But certain organic molecules could provide a remedy by holding the fragile crystal lattice together like a molecular framework and making the solar cells significantly more robust.
More and more countries are relying on the sun instead of coal or gas to reduce CO₂ emissions and protect the climate. In order to meet the growing demand, more solar modules are needed as well as particularly efficient and long-lasting technology that reliably supplies electricity under real weather conditions. Perovskite solar cells, for example, are made of special crystalline materials that convert sunlight into electricity particularly efficiently, but are not yet robust enough to permanently withstand temperature fluctuations on roofs.
But what mechanisms cause perovskite cells to be damaged when used in sun, heat and frost? And what can you do about it? A research team led by Kun Sun from the Technical University of Munich has now addressed this question in two studies.
Breathing material
The researchers focused on the upper layers of so-called tandem solar cells – special solar modules in which perovskite solar cells lie on top of classic silicon solar cells. The upper layer particularly captures light in the shorter-wave blue spectral range, while the silicon cell underneath primarily uses the longer-wave red and infrared components of sunlight. This means that sunlight is used more efficiently and more electricity can be generated than with conventional solar modules.
To find out why the cells lose performance when there are temperature fluctuations, the researchers used X-ray measurements to observe how the crystal lattice of the upper layer behaves during rapid changes in heat and cold. This showed that the perovskite expands and contracts – almost as if the material was “breathing”. These movements create microscopic tensions that, in the long term, reduce the performance of the cells.
The burn-in phase – a weak start
What’s special about the discovery is that most of the reduction in performance happens right at the beginning – the cells lose up to 60 percent of their original capacity during the “run-in”, also known as the burn-in phase. “We were able to show that a kind of microscopic tug of war triggers this loss,” explains Sun. “Stresses arise inside the material and its structure changes. This costs performance.”
But how can you prevent the material from literally falling apart due to this constant stress? In a second study, the researchers compared special organic molecules that act as spacers and hold the crystal lattice together like a molecular framework. This showed that some candidates only stabilized the material slightly, but a more voluminous molecule called PDMA ensured that the solar cells remained stable even during rapid temperature changes.
A step towards the future
The findings are an important step towards more robust solar cells that can also convert sunlight particularly efficiently. “The future of photovoltaics has the prefix tandem,” says senior author Peter Müller-Buschbaum. “By understanding the microscopic mechanisms, we are paving the way for a new generation of solar modules that are both highly efficient and robust enough to last for decades in the field.”
Source: Technical University of Munich; Specialist article: Nature Communications, doi: 10.1038/s41467-025-68219-w