Linking colloidal and optical properties of I-III-VI-based semiconductor nanoplatelets and their assemblies

• Applicants: Professor Dr. Tobias Kraus; Dr. Fabian Paulus, since 10/2025
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Synthesis and Properties of Functional Materials ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565032385

In this joint project, we will develop a colloidal synthesis of Cu-Zn-In-S (CZIS)-based nanoplatelets (NPLs) and study their self-assembly in order to elucidate relationships between their optical properties, surface ligands, and arrangement in ordered structures. It will combine complementary expertise and efforts of Dresden and Saarbrücken groups. The work will consist of two main parts: 1) development of the colloidal synthesis of CZIS-based NPLs towards a more precise tuning of their dimensions, in particular thickness, followed by their comprehensive characterization (the Dresden group), and 2) study of their self-assembly at three different hierarchical levels (the Saarbrücken group). Semiconductor NPLs possess unique anisotropic properties due to their strong quantum confinement in one dimension, because the thickness of the NPLs is typically significantly smaller than the corresponding exciton Bohr radius of the material. The most studied and developed member of 2D semiconductors so far is CdSe, whose practical applications in electronics face serious restrictions due to the presence of toxic Cd. Therefore, in recent years the focus of the research community shifts towards less toxic alternatives, one of which is I-III-VI-based semiconductor nanocrystals, such as CIS. 2D shaped I-III-VI-based nanocrystals are scarcely studied due to the lack of synthetic protocols, caused by the complexity of reaction mixtures and a lack of control over the nucleation and growth processes. Here, the Dresden group will make the main contribution, exploiting our newly developed synthetic approach based on cation exchange. Thus, synthesized NPLs will undergo ligand exchange to a wide range of organic, inorganic, and hybrid organic-inorganic ligands. Tuning their surface properties will play a paramount role in controlling their self-assembly behavior, which will be studied mainly by the Saarbrücken group. The self-assembly of the NPLs will be investigated at three different levels of complexity: 1) agglomeration of the NPLs in solution forming stacks, 2) assembly into thin monolayer films with edge-up or face-down orientation, and 3) formation of NPL multilayers. Each assembly type will be thoroughly characterized by state-of-the-art methods supported by molecular dynamic simulations to find correlations between the ligand shell, its impact on the arrangement of the NPLs, and, in turn, on the optical properties of the resulting assemblies. This work is expected to have impact not only on the fundamentals of chemistry of colloidal 2D semiconductor nanomaterials, their synthetic methodology and self-assembly behavior, but also to provide a reliable way of controlling optical properties of macroscopic samples via tunable electronic coupling between the NPLs. The resulting materials and structures with tunable photophysical properties will be very promising candidates for applications in LEDs, solar cells, luminescent solar concentrators, and photodetectors.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Privatdozent Dr. Vladimir Lesnyak, until 9/2025