Hybrid Germanium Bromide Perovskites with Tunable Second Harmonic Generation

Liu Y., Gong Y.-P., Geng S., Feng M.-L., Manidaki D., Deng Z., Stoumpos C. C., Canepa P., Xiao Z., Zhang W.-X., and Mao L.; Angew. Chem.Int. Ed. 61, e202208875 (2022).


Ge-based hybrid perovskite materials have demonstrated great potential for second harmonic generation (SHG) due to the geometry and lone-pair induced non-centrosymmetric structures. Here, we report a new family of hybrid 3D Ge-based bromide perovskites AGeBr3, A=CH3NH3 (MA), CH(NH2)2 (FA), Cs and FAGe0.5Sn0.5Br3, crystallizing in polar space groups. These compounds exhibit tunable SHG responses, where MAGeBr3 shows the strongest SHG intensity (5×potassium dihydrogen phosphate, KDP). Structural and theoretical analysis indicate the high SHG efficiency is attributed to the displacement of Ge2+ along [111] direction and the relatively strong interactions between lone pair electrons of Ge2+ and polar MA cations along the c-axis. This work provides new structural insights for designing and fine-tuning the SHG properties in hybrid metal halide materials.