Halogenated‐Methylammonium Based 3D Halide Perovskites

3D perovskites with typical structure of ABX₃ are emerging as key materials to achieve high-performance optoelectronic devices. The variation of A-site cation is promising to achieve enhanced properties; however, is limited to a few available choices of methylamine, formamidine, and cesium. In this work, halogenated-methylammoniums are developed as A cation to broaden the family of hybrid perovskites. Single crystals and colloidal nanocrystals of halogenated-methylammoniums based perovskites are successfully synthesized, showing bright future as alternatives for device exploration. In particular, the improved thermal stability and low exciton binding energy from single crystals measurements are demonstrated and bright tunable emission from blue to green for colloidal nanocrystals is achieved.