Lead‐Free Semiconductors: Soft Chemistry, Dimensionality Control, and Manganese‐Doping of Germanium Halide Perovskites

摘要： Lead halide perovskites have drawn enormous interest due to their exceptional photovoltaic and optoelectronic properties. However, the toxic heavy metal lead is harmful to humans and the environment resulting in a need for strategies to replace this toxic element. Herein, we report a facile aqueous synthesis of CsGeX3 (X = I, Br) perovskite nanocrystals with size control achieved by varying the cysteammonium halide ligand concentration. We observe a variety of morphologies including pyramidal, hexagonal, and spheroidal. CsGeX3 nanocrystals undergo a lattice expansion due to partial replacement of Cs+ with larger cysteNH3+ cations into the lattice. We successfully dope Mn2+ into the CsGeX3 lattice for the first time with incorporation up to 29% in bulk and 16% in nano samples. XRD peak shifts and EPR hyperfine splitting strongly indicate that Mn2+ is doped into the lattice. Our results introduce a new member to the lead-free halide perovskite family and set the fundamental stage for their use in optoelectronic devices.