New synthesis method yields bright perovskite nanocrystals that can also sense temperature

Researchers at ITMO University, the Kurchatov Institute's Institute of Macromolecular Compounds, and Harbin Institute of Technology have developed a solvothermal synthesis route for cesium lead halide (CsPbX₃, where X is chlorine, bromine, or iodine) perovskite nanostructures that gives precise control over both chemical composition and morphology, producing nanocrystals and nanoplatelets with tailored optical properties for optoelectronic and sensing applications.

Conventional methods for making perovskite nanocrystals, such as hot-injection and ligand-assisted reprecipitation, can produce high-quality emitters but tend to have narrow processing windows and fast, hard-to-control nucleation, making it difficult to reliably produce monodisperse one- or two-dimensional nanostructures at scale. Solvothermal synthesis, carried out at moderate temperatures of 100–200°C and elevated pressure inside sealed autoclaves, instead shifts crystal growth from a kinetically driven to a thermodynamically controlled process. The team used this approach as a multi-variable toolkit, adjusting reaction temperature, time, and precursor ratios to steer crystal growth along specific crystallographic facets.

Using this method, the researchers produced highly emissive CsPbBr₃ nanocrystals with a photoluminescence quantum yield of 88% and narrow emission, along with CsPbCl₃ nanocrystals. By adjusting the ratio of halide content to lead content in the precursors, they also produced monodisperse CsPbBr₃ and CsPbI₃ nanoplatelets just two to three monolayers thick with ultranarrow emission spectra.

The team further synthesized Mn²⁺-doped CsPbCl₃ nanocrystals with varying manganese content and studied how doping level affects their temperature-dependent photoluminescence. The Mn²⁺ concentration could be tuned to create dual-band, self-referencing temperature sensors with an extended operational range and balanced quantum yield, reaching a relative sensitivity of 7.22%/K at 265 K -  a demonstration the researchers point to as evidence for the scalability of solvothermal synthesis in producing perovskite nanostructures for optoelectronic and sensing applications.