Mechano-Chemical Synthesis, Structural Features and Optical Gap of Hybrid CH₃NH₃CdBr₃ Perovskite

Hybrid methyl-ammonium (MA:CH₃NH₃⁺) lead halide MAPbX₃ (X = halogen) perovskites exhibit an attractive optoelectronic performance that can be applied to the next generation of solar cells. To extend the field of interest of these hybrid materials, we describe the synthesis by a solvent-free ball-milling procedure, yielding a well crystallized, pure and moisture stable specimen of the Cd tribromide counterpart, MACdBr₃, which contains chains of face-sharing CdBr₆ octahedra in a framework defined in the Cmc2₁ (No 36) space group. The details of the structural arrangement at 295 K have been investigated by high angular resolution synchrotron x-ray diffraction (SXRD), including the orientation of the organic MA units, which are roughly aligned along the c direction, given the acentric nature of the space group. UV-vis spectra unveil a gap of 4.6 eV, which could be useful for ultraviolet detectors.