Published on: 2026-07-20
Source: Peter the Great St. Petersburg Polytechnic University –
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Scientists at SPbPU have monitored the birth and growth of perovskite CsPbBr3 nanocrystals directly inside glass in real time. The new method paves the way for creating glass-crystalline materials for photonics, laser technology, LEDs, and radiation detectors. The results were published in the journal Ceramics International. The research is conducted with the support of the federal program “Priority-2030”.
“We have obtained a tool that allows us to track the kinetics of nanocrystal growth in glass from 7 to 12 nanometers, which enables us to produce material with a tunable position of the luminescence band for optoelectronic devices” — said the head of the scientific laboratory “Laboratory of Optical Materials Science” at the National Research Center “Nanotechnologies and Coatings” of the Institute of Mechanical Engineering, Materials and Transport, Viktor Klinkov.
Halide perovskites are materials that the global optoelectronics industry is currently focusing on. These are compounds with a three-dimensional crystal structure based on lead and halogens — chlorine, bromine, or iodine — with cesium or methylammonium cations. Iodide perovskites are already setting efficiency records in solar cells, while bromide perovskites, such as CsPbBr3, exhibit intense luminescence — it is precisely this emission that predicts their use as the basis for next-generation light-emitting diodes and lasers.
However, perovskites have a vulnerability: they degrade quickly in air. One way to improve their stability and protect them from atmospheric exposure is to grow nanocrystals directly inside the glass, where they are securely sealed. This is done as follows: during the glass synthesis, cesium and lead bromides are added to the initial mixture, the melt is cooled, and then the batch is held at a constant temperature—an isothermal annealing is performed. During this time, CsPbBr3 nanocrystals grow within the volume of the glass. The process can be monitored even with the naked eye: the colorless glass gradually turns yellow because the growing crystals absorb the blue-green part of the spectrum.
But for researchers, the process of crystal growth at the initial stage in glass long remained a “black box.” The concentration of crystals in the glass was low, and the classical tool — X-ray structural analysis — was almost powerless here: weak diffraction signals from nanocrystals were drowned in the diffuse “halo” of the glass matrix. A clear picture only appeared at the later stages of annealing, when crystals had already outgrown the sizes at which quantum size effects manifest, that is, when the properties of the material stop depending on their size. It turned out that the growth of crystals from units to tens of nanometers remained out of researchers’ sight.
Scientists from Polytechnic found a way to bypass this limitation: instead of X-rays, they used absorption spectroscopy. Nanocrystals of CsPbBr3 have a characteristic exciton absorption peak, a kind of optical fingerprint, the position of which is strictly related to the size of the crystal due to quantum confinement effects. By measuring absorption spectra after each annealing, the authors for the first time tracked the evolution of the crystals in real time (in situ) from the first minutes of the process, when their size was only 7–8 nanometers, that is, about ten thousand times smaller than the thickness of a human hair. Then the classical theory of crystallization (the Johnson–Mehl–Avrami–Kolmogorov kinetic formalism) was applied to the optical data to extract the fundamental crystallization parameters of CsPbBr3 in borosilicate glass.
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