Impact of the Ligands’ Electronic Dipole Moment on Electrochemical p-Doping of CsPbBr3 Nanocrystals

Lead halide perovskite nanocrystals (NCs) are promising materials for light-emitting diodes (LEDs) due to their wavelength tunability, narrow emission line width, and high photoluminescence quantum yield. Oftentimes, these devices suffer from charge carrier imbalance and reduced charge injection because as-synthesized NCs are covered by long aliphatic ligands. Here, we show a ligand exchange to small electron-withdrawing or electron-donating cinnamate ligands. We probe the influences of the ligands’ dipole moment on hole injection by photoluminescence spectroelectrochemistry (PL SEC). We find that hole injection into NCs covered by electron-withdrawing ligands is facilitated and that these NCs exhibit a superior LED performance. Our results emphasize the importance of kinetic hinderance for charge carrier injection into NC films, a feature that is more accurately derived by SEC compared to other techniques like photoelectron spectroscopy.