Cs3Pb2(CH3COO)2X5 (X=I, Br): Halides with Strong Second‐Harmonic Generation Response Induced by Acetate Groups

Nonlinear optical (NLO) crystals are the key component in solid‐state lasers. New second‐harmonic generation (SHG) effective halides, Cs3Pb2(CH3COO)2X5 (X=I, Br), have been rationally synthesized by introducing acetate groups into lead halide perovskites under moderate solvothermal conditions. Cs3Pb2(CH3COO)2X5 (X=I, Br) feature highly oriented anionic chains constructed by distorted [PbX4O2] (X=I, Br) polyhedrons. Both the theoretical studies and the dipole moment calculations uncover that their SHG effects are mainly originated from the distorted [PbX4O2] (X=I, Br) polyhedrons. Remarkably, Cs3Pb2(CH3COO)2I5 exhibits strong phase‐matching SHG response (8×KDP) and large birefringence (0.26@ 1064 nm). Moreover, Cs3Pb2(CH3COO)2X5 (X=I, Br) also possess high laser damage threshold (LDT) which are almost 27 and 41 times that of AgGaS2, respectively. Cs3Pb2(CH3COO)2X5 (X=I, Br) featuring 1D highly oriented chain with strong second harmonic generation response are designed by rationally converting the idealized [PbX6] octahedron into the distorted [PbX4O2] polyhedron.