Achieving strong second harmonic generation effects induced via dimensional increase of PbX6 octahedra and halogen substitutes in (C10H11N3)PbX4 (X = Cl or Br)

Abstract

Obtaining noncentrosymmetric structures and achieving desired performance indicators in nonlinear optics (NLO) are ongoing challenges. In this work, the rational design of an A-site cation (di(pyridin-4-yl)amine cation, [C₁₀H₁₁N₃]), stereochemically active lone pair cation (Pb²⁺) and halogen substitutes in hybrid metal halide perovskites (ABX₃) was utilized to obtain two novel NLO crystals, (C₁₀H₁₁N₃)PbX₄ (X = Cl or Br), achieving desirable NLO performance, including pronounced anisotropy of second harmonic generation (SHG). Through the introduction of PbX₆ octahedrons in the (C₁₀H₁₁N₃)BX₄ system, compounds transformed from zero-dimensional to one-dimensional structures, resulting in significantly enhanced SHG activity. By controlling the halogen atoms, the SHG effect and birefringence of (C₁₀H₁₁N₃)PbX₄ were further improved. Experimental and theoretical studies validated that the improved NLO performance in the (C₁₀H₁₁N₃)PbX₄ system is closely related to the modulation of the octahedral distortion of PbX₆. The successful utilization of such structural dimension evolution and halogen substitution strategy offers a universal way for the rational regulation of crystal structures and optoelectronic performance of hybrid metal halide perovskites.