An approach to increase the efficiency of europium-based OLEDs was proposed through the formation of a mixed-ligand complex. The design of a series of europium complexes, together with an optimization of the solution deposition, including the host selection, as well as the variation of the solvent and deposition parameters, resulted in a noticeable increase in OLED luminance. As a result, the maximum luminance of the Eu-based OLED reached up to 700 cd/m², which is one of the highest values for an Eu-based solution-processed OLED. Finally, its stability was investigated.

In recent years, hybrid manganese(II) halides (HMHs) have attracted wide attention due to their impressive optical properties, low toxicity, and facile synthetic processibility. Being effective reab-sorption-free phosphors, these compounds demonstrate the potential to be used as low-cost solu-tion-processable scintillators. However, most of the HMHs studied to date contain bulk organic cations and, as a result, are characterized by low density and low X-ray stopping power. For this reason, we studied manganese(II) halides with compact organic cations such as formamidinium (FA+) and acetamidinium (Ac+). In particular, we synthesized four new phases, two of which are characterized by octahedral coordination of manganese ions (FAMnBr3, AcMnBr3) and red emis-sion, whereas the other two have tetrahedrally coordinated Mn2+ ions (FA3MnBr5, Ac2MnBr4) and green emission. Photoluminescence (PL) and radioluminescence measurements demonstrated high PL quantum yields and reasonable scintillation light yields of acetamidinium-based compounds. In addition, unlike most known HMH-based scintillators, the discovered materials have a relatively high density, due to the small fraction of the volume occupied by organic cations, so their X-ray attenuation coefficients are comparable to the well-known oxide scintillators.