Assessing the classicality of photon echo from excitons in lead halide perovskite nanocrystals - APS Journals

volume 15, Article number: 356 (2026) Cite this article AbstractLight irradiation in two-dimensional materials is well-known to excite tightly-bound many-body excitonic states that dominate optical responses. Recent theory analysis under intense laser conditions identifies the mechanisms and timescales through which excitons form, evolve, and dissociate. These findings open new opportunities for sensing and optically controlling many-body physics on ultrafast timescales.

Nanocrystals have become an important part of modern materials science, with quantum dots helping inspire the 2023 Nobel Prize in Chemistry. Yet despite their enormous potential, researchers have only been able to produce these microscopic crystals from a relatively narrow range of materials. Now, chemists at the University of Chicago and Argonne National Laboratory have developed a method for creating nanocrystals from metal nitrides, a technologically important group of materials that had resisted conventional nanocrystal synthesis. The study, published in Nature, could expand the possibilities for electronics and other applications, including flexible lighting and medical implants.

In a study published in Advanced Optical Materials, researchers at Vilnius University (VU) demonstrated perovskite-based laser structures that maintained stable performance over more than 400 million pulses. Their findings address one of the major challenges limiting the practical use of perovskites: their instability. These semiconductor materials could play an important role in next-generation optical technologies, but their tendency to degrade has long posed a challenge for researchers worldwide. In some sense, perovskites can be compared to graphene. Like perovskites, graphene spent years being studied in labs because of its potential before industry eventually began using it. Today, it's widely applied in solar energy, electronics and batteries. Perovskites may hold even greater potential, but they come with a major drawback: they're highly unstable and degrade quickly in the presence of moisture.

Researchers have uncovered a way to suppress halide segregation in tandem solar cells, improving both efficiency and stability. Their strategy works across multiple mixed-halide perovskite compositions, suggesting the approach may be broadly applicable to this important class of photovoltaic materials. Tandem solar cells stack two different light-absorbing materials on top of one another, allowing them to convert more sunlight into electricity than either material alone. Mixed-halide perovskites—crystals containing both iodide and bromide ions—are commonly used as the top layer because their composition can be tuned to absorb high-energy light while permitting longer wavelengths to pass through to the lower cell. However, because iodide and bromide crystallize at different rates, the resulting films tend to be uneven in composition, with bromide-rich regions forming near the surface.