Crystals in the lab aren't gemstones. They're materials built from atoms arranged in precise, repeating patterns. That atomic order lets crystals absorb light, move charge and convert energy, enabling technologies from LEDs and solar cells to the sensors in everyday cameras.
Perovskites are lab-grown crystals that push those abilities even further, absorbing and emitting light with remarkable efficiency, but only when their atomic structure forms cleanly. Even tiny defects can scatter charge and drain energy, reducing efficiency and shortening device lifetimes.
In new research, scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory helped develop a volatile low-melting mechanism that uses salt additives to tailor perovskite crystallization at the atomic scale, giving researchers far greater control over how these crystals assemble.
The result is perovskite crystalline layers with dramatically fewer defects and far more stable performance. This enables reliable, high-efficiency optoelectronic devices - devices that use the interaction between light and electronic charge.
"Defects have been the bottleneck for perovskites for almost a decade," said study author Yanqi Luo, a beamline scientist in Argonne's X-ray Science division. "If we can remove the major defects, we can finally start building devices that last longer and perform more reliably."
The innovation could help drive brighter screens, better solar panels and more reliable technologies in everyday life.
The research, published in Science, was conducted with researchers at U.S. and international institutions and universities. Researchers conducted much of the experimental analysis at the Advanced Photon Source (APS) and Center for Nanoscale Materials (CNM), both DOE Office of Science user facilities at Argonne.
How the Low-Melting Mechanism Works
Understanding how the mechanism works begins with the moment the perovskite film first starts to melt and reorganize. The eutectic method (meaning a mixture that melts at a temperature lower than any of the individual components do) lowers the melting point of the perovskite chemicals that supply the atoms needed to form the crystal.
Luo compares the process to spreading salt on an icy road.
"Adding salt lowers the melting point of ice, causing it to melt," she said. "Our approach behaves the same way: It creates a lower-melting environment that helps the crystal reorganize into a more stable form."
These changes occur within perovskite films - thin layers of material deposited onto a glass or metal substrate. Crystallization is the moment when those films take shape, and it's also the step that most determines device performance.
In the lab, scientists added two salts - zinc bromide and methylammonium chloride - to lower the melting point of the perovskite materials. As the film heats, parts of the material briefly liquefy, slowing crystallization and giving atoms time to settle into a more uniform structure.
In the volatile mechanism, these chemicals evaporate during heating, guiding the crystal's formation and then disappearing - leaving behind a more stable film with fewer defects.
Seeing the Process with APS X-Rays
Scientists analyzed the salt-treated films on an X-ray beamline jointly operated by the APS and CNM.
The ultrabright X-ray nanoprobe captured a series of snapshots at different stages of the process, showing how the eutectic mechanism melts, flows and guides the perovskite into a smoother, more uniform crystal structure. These measurements examine samples after they have been removed or paused at specific stages, rather than observing the transformation continuously as it happens.
As crystallization continued, the X-ray data revealed another critical motion: zinc atoms drifting toward grain boundaries - tiny fault lines where defects typically gather. Once there, the zinc smoothed out those defects, neutralizing them so they no longer trap charge or waste light.
"What makes this work unique is that we could map chemical composition and performance at the exact same time, in the exact same place," said Tao Zhou, a scientist at the CNM. "That type of correlated X-ray and optical microscopy is extremely rare - and it's what allowed us to link zinc migration directly to better device behavior."
Advancing Toward Scalable, High-Efficiency Devices
The eutectic method produced films with much stronger optoelectronic performance, enabling LEDs that reach new performance records - brighter output, higher efficiency and longer lifetimes. At scale, the process produces large, uniform perovskite layers with the consistency needed for high-efficiency modules and manufacturable, next-generation devices.
"The breakthrough isn't just about making a better crystal - it's about making a better crystal over a large area, which is the key requirement for real-world manufacturing," Zhou said.
What the APS will Unlock Next
Argonne scientists conducted the research before the recent APS upgrade, which transformed the facility into the brightest synchrotron X-ray source in the world, producing beams up to 500 times brighter.
The upgraded APS will elevate this research a step further. With its new storage ring and the newly constructed In-Situ Nanoprobe beamline, researchers will be able to move from step-by-step snapshots to continuous, movie-like views of how crystals form and defects evolve in real time.
Luo describes it as the difference between watching cookies bake in stages versus seeing the entire bake unfold in real time.
"The upgraded APS lets us see the full process, which is exactly what's needed to design materials at scale," she said. "Argonne gives us the bridge between discovery and deployment."