Lead halide perovskites (LHP) are well-known materials that have recently gained considerable attention in optoelectronics. Particularly LHP nanocrystals are very attractive as luminescent materials for potential applications in light-emitting diodes. They combine the advantages of bulk LHP – notably their defect tolerance, solution processability, and band-width tunability – with well-known features of colloidal quantum dots, like high photoluminescence quantum yield with narrow emission bandwidth as well as size and composition tunable colors. However, electroluminescent quantum dots often have the dilemma that high photoluminescence quantum yield and efficient charge injection and transport, which are the prerequisites for electroluminescence, are counteracting each other. For LHP nanocrystals similar problems may occur, but this has not been explored in detail yet. Thus the main goal of this project is to develop a novel ligand exchange strategy that simultaneously provides the required surface passivation of nanocrystals to yield high photoluminescence and at the same time induces sufficient electronic coupling between nanocrystals to enable good charge injection and transport in electroluminescent applications. Our unique approach will consist in using charge-neutral organic pi-conjugated ligand systems which induce covalent coupling of nanocrystals. In the course of the project we will address a number of scientific questions relevant to the fundamental understanding of LHP semiconductors.
