Solar cells made from cheap, printable materials are nearing top-tier performance, yet they still tend to fail when heated.
A new protection step matters now because getting clean electricity at scale requires devices that keep working through harsh conditions.
In many high-efficiency prototypes, the hardest moment comes during fabrication, when heat can ruin a promising solar layer.
Work at Xi’an Jiaotong University (XJTU) in China focused on stopping heat damage before it spread widely.
The project was led by Dr. Chao Liang. His research targets fragile interfaces in thin films.
By protecting the surface during heating, the team reduced the chance that tiny flaws would grow into long-term failures.
Many labs build solar cells from perovskites, crystal materials that absorb light extremely well. This is because they can reach high efficiencies using these materials.
Unlike silicon, their structure is held together by electric attraction, so heat can loosen key links.
As those links weaken, ion migration – charged atoms drifting through the material – becomes easier and electrical losses rise over time.
That same mobility helps explain why perovskite devices can fade quickly unless their surfaces stay orderly and chemically stable.
Making a smooth perovskite film usually needs annealing, controlled heating that helps crystals form smoothly, after the wet coating dries.
During that heat, iodine can escape from the top surface, and the remaining crystal becomes easier to damage.
With an iodine vacancy, a missing iodine atom in the crystal, nearby lead ions lose partners and the local structure distorts.
Defects that start at the surface can then spread inward through the perovskite, cutting electrical flow and setting up faster breakdown later.
To block the earliest damage, the team used molecular press annealing, a hot-press step that bonds molecules to the surface of the perovskite.
A thin template film was pressed onto the perovskite without solvent, creating a dense capping layer during heating.
That film carried 2-pyridylethylamine, a small nitrogen-rich organic molecule, and its two binding sites held the surface together.
The researchers framed the step as a way to prevent surface damage during heating, instead of fixing defects after they appear.
The key molecule clung to exposed lead atoms on the surface, giving the crystal stronger bonds during high heat.
By binding in two spots, it stabilized the lead-iodine framework, so fewer vacancies formed and fewer existing ones spread.
With a reduction in defects, charges moved more cleanly across the film, and more of the captured sunlight reached the electrodes as power.
That improvement depends on keeping the contact uniform, since gaps in the pressed layer could still leave escape routes for iodine.
For years, the National Renewable Energy Laboratory chart tracked perovskites climbing fast, and this result pushed near the top.
Using a standard certification, the group reported 26.5 percent efficiency in a tiny device and 23.0 percent in a 2.5-square-inch (16 square centimeter) module.
Those gains came mostly from smoother charge collection, because fewer defects meant less energy was wasted as heat inside the cell.
Even so, high performance on a press-ready film is only a step toward mass production on the full panel lines of solar cells.
Efficiency numbers matter less if a solar cell loses power after months, so the team stressed devices under tough heat and moisture.
During operation at 185 degrees Fahrenheit (85 degrees Celsius) and 60 percent relative humidity, the cells kept 98.6 percent of their starting output after 1,617 hours.
In dark storage at room conditions, they still held 97.2 percent after 5,280 hours, showing slow chemical change without light.
These tests cannot predict every outdoor stress, but they do show that fixing early defects can pay off later.
A technique that works once is not enough, so the team tested whether the imprinting film could be reused many times.
One 2-pyridylethylamine template made 30 consecutive devices, and the process cut surface-treatment material costs by more than 47 times.
Because the approach avoided extra solvent washes, it also reduced the risk of dissolving or roughening the delicate top layer.
Reuse helps with production costs of solar cells, but factories would still need reliable pressure tools and quality checks to keep every press even.
Perovskite devices still face hurdles outside the lab, especially when they must survive rain, dust, and daily temperature swings.
Protective packaging must block water and oxygen for years, and the seals must stay tight even as materials expand.
Most high-efficiency perovskites also contain lead, so manufacturers have to prevent leaks during use and handle waste responsibly.
Molecular press annealing improves one failure pathway, but real solar cell panels will need multiple protections working together under sunlight.
By pressing a protective molecule into place during heating, XJTU turned a risky fabrication moment into a controlled surface step.
If other groups can scale the press process and prove long outdoor lifetimes, this approach could help perovskites compete in markets.
The study is published in Science.
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