Extensive study of hybrid organic-inorganic perovskites became one of the most rapid-developing research topics in materials science during the past decade. Hybrid halide perovskites have a general formula ABHal₃, where A⁺ is an organic cation, B²⁺ is a metal cation usually represented by Pb, Sn or Ge and Hal^– is a halogen anion. For 25 years only methylammonium (perovskites discovered in 1978) and formamidinium (perovskites discovered in 1997) were known to be suitable organic cations to support the formation of 3D hybrid perovskites with all three Cl^–, Br^– and I^– anions. Simultaneously, it is worth mentioning, that methylhydrazinium and fluoromethylammonium can stabilize 3D perovskite structures with Cl or Br anions.

Our study shows that aziridinium cation (AzrH) is able to stabilize 3D perovskite structure of (ArzH)PbHal₃ (Hal = Cl^–, Br^–, I^–). We describe the synthesis of the first aziridinium-based compounds, namely hybrid perovskites (AzrH)PbHal₃. Highly reactive species of aziridinium was stabilized in 3D lead halide frameworks and was found to be an organic cation which is small enough to promote the formation of semiconducting organo-inorganic materials. All three perovskites crystallize in cubic Pm-3m space group at room temperature. Optical bandgaps of 2.99 eV (Cl), 2.27 eV (Br) and 1.52 eV (I) were determined for new hybrids.[1]

In addition, by employing the antisolvent precipitation technique and stabilization with a cationic surfactant we succeeded in obtaining quantum dots of (ArzH)PbBr₃ with the average size of 8.6 nm that display green (520 nm) luminescence. The obtained nanoparticles are characterized by green emission luminescence (520 nm) and display good chemical and photostability. It was shown that the quantum dots’ emission can be blue-shifted via bromide substitution with chloride by 58 nm and red-shifted via substitution with iodide by 122 nm. This study shows the perspective of aziridinium-based materials for the elaboration of advanced photonic nanostructures.[2]

Moreover, we have managed to obtain new 3D tin-based (lead-free) hybrid perovskites with aziridinium cation (AzrH)SnHal₃ (where Hal = Cl, Br or I). All of the obtained perovskites undergo temperature-dependent crystallographic phase transitions at low temperature. UV-vis measurements showed that (AzrH)SnHal₃ perovskites display absorption edges, characteristic for semiconducting materials. The optical band gaps of the obtained compounds were found to be 3.48 eV (Cl), 2.46 eV (Br) and 1.54 eV (I). Similar aziridinium perovskites have also been obtained with germanium.

In addition, the possibility to fine-tune the bandgap of obtained perovskites through mixing halogen or Sn/Pb sites was investigated. Thus, the discovered compounds form a new group of 3D semiconducting lead-free perovskites that can widen the range of suitable materials for solar cells and light-emitting diodes production.