SYNTHESIS TECHNOLOGY AND PRACTICAL USE OF PbS AND PbSe QUANTUM DOTS (REVIEW)

This review is dedicated to quantum dots (QDs) based on lead sulfide (PbS) and lead selenide (PbSe). These semiconductor nanocrystals exhibit unique electronic and optical properties due to the quantum confinement effect, which differ from the properties of bulk materials. The properties of QDs depend on their size, shape, and composition, allowing for the tuning of the band gap energy and the wavelength of absorption/emission. PbS and PbSe QDs are valuable due to their small effective charge carrier mass, large exciton Bohr radius, and the ability to operate in the near and mid-infrared (NIR and MIR) spectral regions. This makes them promising for applications in solar cells, light-emitting diodes (QLEDs), photodetectors, biosensors, and thermoelectric devices. The review discusses synthesis methods in detail. The hot injection method is highlighted as one of the most established methods for obtaining high-quality QDs with a narrow size distribution. A classical protocol for the synthesis of PbS QDs by this method using oleic acid and lead oxide/bis(trimethylsilyl)sulfide precursors is described. The "heat-up synthesis" method is also mentioned. Photochemical, bacterial, and microwave-activated approaches are also noted. For the synthesis of PbSe QDs, the hot injection method is also widely used with various selenium precursors. Size control is critically important and depends on temperature, reaction time, precursor type, and ligands. Various characterization methods are used to understand the properties of QDs. Practical applications of PbS and PbSe QDs are discussed. PbS QDs are promising for solar cells due to broad absorption, including the NIR region. Research has shown the dependence of the efficiency of solar cells based on them on synthesis conditions and precursors. PbS QDs are also used to create infrared light-emitting diodes (NIR- QLEDs), where charge carrier diffusion and photoluminescence quantum yield are important. The influence of ligands and a perovskite matrix on QLEDs efficiency is shown. Furthermore, PbS QDs are used in photodetectors and single-electron transistors. PbSe QDs also have potential in solar cells, QLEDs, and photodetectors for the longer NIR region. To improve the properties of QDs, the formation of core-shell structures (PbS/CdS, PbSe/CdSe) is used. This increases PL QY and stability. Cation exchange and SILAR methods for shell formation are discussed. Surface modification and ligand exchange play a crucial role in stability, solubility, and charge transport. Stability is a critical factor for applications, and shell formation and appropriate ligands help protect QDs from degradation. Despite significant progress, challenges exist related to stability, toxicity, and production scaling. Further research in the development of new synthesis methods and surface passivation remains important.