Recently, lead halide perovskites (LHP) have attracted a lot of attention in the field of optoelectronics, inter alia, the application in light emitting devices (LED) is of enormous interest.^[1,2] One promising approach to increase the efficiency is the utilization of nanocrystals (NC) due to their ability of tailoring the ligand shell to specific needs.^[3]

Therefore, the ligand dynamics at the NC surface was examined on soy-lecithin covered LHPs and a highly dynamic surface equilibrium was discovered. It was found that depending on the surface ligand density the lateral diffusion, i.e., the movement of the ligand along the NC surface can be tuned. This behavior can be rationalized by the zwitterionic nature of lecithin and the binding situation at the surface. Precisely, as more ligand is added, less surface area per ligand is available and, thus, the molecules can only attach with one functional group rather than both, which results in significantly faster dynamics.

In a subsequent step, ligand exchange on CsPbBrI₂@SiO_x LHPs was performed utilizing organic semiconductors, namely metal derivatives of mono-carboxy tetraphenylporphyrin (mMTPP). By tethering the novel ligand to the NCs, the electronic conductivity could be increased whilst simultaneously suppressing ionic currents. The underlying phenomenon of this effect was the decrease of the charging energy. Upon examining the NCs in electroluminescent devices it was found that the current efficacy and turn-on voltage was improved by the semiconducting ligand almost fivefold.^[4]

However, an especially important downside of perovskite-based devices is the stability of the material against environmental influences. From the temperature-dependent conductivity of CsPbBrI₂ NCs an increased phase stability was found by introducing mZnTPP as a ligand.^[4] Upon exposing the system to X-ray radiation, we found a radiation-induced, isotropic contraction of the crystal lattice which in turn resulted in an altered electrostatic potential. This could be correlated to a characteristic shift in X-ray photoelectron spectroscopy signals, i.e., the electronic structure. Furthermore, these structural changes could be identified as a very likely driving force for the decomposition, which appears to be ligand dependent. For an oleic acid / oleylamine ligand shell, the decomposition into the corresponding salts was found, whereas the exchanged system exhibited a novel, significantly slower decay in the form of a disproportionation of Pb²⁺ to Pb⁰ and Pb³⁺.