2, Wageningen University & Research, Wageningen, , Netherlands
3, TU Delft, Delft, , Netherlands
4, Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grnberg Institute, Julich, , Germany
Solar devices based on semiconductor nanoparticles require the use of conductive ligands; however, replacing the native, insulating ligands with conductive metal chalcogenide complexes introduces structural defects within the crystalline nanostructure that act as traps for charge carriers. We utilize atomically thin semiconductor nanoplatelets (NPs) as a convenient platform for studying both microscopically, and spectroscopically, the development of defects during ligand exchange with conductive ligands Na4SnS4 and (NH4)4Sn2S6. Using calibrated HAADF STEM imaging we quantify the extent of ligand exchange induced damage on NPs. Remarkably, we show that these defects can be repaired via mild chemical or thermal routes, through the addition of L-type ligands or wet annealing, respectively. Photoluminescence quantum yield and conductivity studies confirm this picture and further stress the importance of choosing a non damaging ligand exchange protocol. This results in a higher quality, conductive, colloidally stable nanomaterial that can be used as active film in optoelectronic devices such as transistors, solar cells or light emitting diodes.
E. Marino, T. E. Kodger, R. W. Crisp, D. Timmerman, K. E. MacArthur, M. Heggen, P. Schall, Angew. Chem. 2017, 129, 13983.