Methylpiperazine based 0D chiral hybrid lead halides for second harmonic generation

Hybrid organic–inorganic metal halides (HOMHs) have recently attracted broad research interest for their structural tunability and remarkable optoelectronic properties. Among them, chiral HOMHs have demonstrated promising applications in second-order nonlinear optics (NLO) on account of their inherent noncentrosymmetric structures. Herein, we synthesized two new chiral HOMHs, (S-/R-2-C₅H₁₄N₂)₂PbI₆, based on S-/R-2-methylpiperazine chiral amines. They feature a band gap close to 2.9 eV with high phase purity as well as environmental and thermal stability. The induction of the chiral optical properties of (S-/R-2-C₅H₁₄N₂)₂PbI₆ by chiral organic cations was verified by circular dichroism (CD) spectroscopy. Moreover, the resulted HOMHs materials demonstrate a strong second harmonic generation response with a large laser damage threshold (∼2.97 mJ cm⁻²), showing promising applications in NLO photonic devices.