Perovskite ligand binding

Lead-halide perovskite nanocrystals are promising candidates for light emitting applications due to their defect-tolerant surface, which allows them to emit cleanly in imperfect environments. Optical properties are typically controlled by ligands on the surface of the nanocrystal. Experimentalists in the Bawendi group at MIT identified that dicationic quaternary ammonium ligands bind strongly to the surface and yield excellent optical properties. There are two degrees of freedom that need to be optimized in these ligands: the length of the side chains, and the length of the carbon chain linking the ammonium groups.

Using density functional theory simulations, I identified the optimal dicationic quaternary ammonium ligand for CsPbBr3 nanocrystals as having a 3-carbon chain linking the two ammonium groups. The ligands replace two adjacent Cs cations, and the 3-carbon chain allows the ligand binding sites to align well with these Cs sites in the perovskite with minimal disruption to the perovskite structure, leading to the lowest root mean squared displacement of perovskite atoms compared to the crystal structure of any linker size. These results were in good agreement with experiment, where 3-carbon chain showed the best properties.

This work was done in close collaboration with Matthias Ginterseder. You can read about this project:

1. Ginterseder, M.; Sun, W.; Shcherbakov-Wu, W.; McIsaac, A.R.; Berkinsky, D.B.; Kaplan, A.E.K.; Wang, L.; Krajewska, C.; Šverko, T.; Perkinson, C.F.; Utzat, U.; Tisdale, W.A.; Van Voorhis, T.; Bawendi, M.G. Lead Halide Perovskite Nanocrystals with Low Inhomogeneous Broadening and High Coherent Fraction through Dicationic Ligand Engineering. Nano Lett., 2023, 23 (4), 1128-1134. link