Modeling ligand crosslinking for interlocking quantum dots in thin-films

When integrating quantum dots (QDs) into thin-film photonic through solution process, dissolution of QD films should be prevented against exposure to various solvents in the post-processing steps. Amongst various approaches, exploiting ligand-crosslinkers to form crosslinked QD network has shown great promise. Such a crosslinked network interlocks the neighboring QDs, and increases the QD thin-film resistance during post-processing. For this method, crosslinker structure, and the number of crosslinkers have significant effects on the crosslinking performance. However, experiments could not fully ascertain the mechanism of the crosslinking process. To this end, a kinetic Monte Carlo (kMC) model is developed to elucidate the mechanism and kinetics of the crosslinking process. Specifically, the ligand crosslinking reaction is broken down in two steps (i.e., radical formation, and a C-H insertion reaction). Then, the surface reaction kinetics for these two steps is modeled and integrated with a 2D kMC lattice. In the model, different spatial crosslinking configurations between the crosslinkers and ligands are reflected considering the geometry, dimensions and structure of the crosslinkers. The simulation results showcase the temporal evolution of the crosslinking process for different crosslinkers and are in good agreement with experimental observations.