Cs3 Pb2 (CH3 COO)2 X5 (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, Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br), have been rationally synthesized by introducing acetate groups into lead halide perovskites under moderate solvothermal conditions. Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br) feature highly oriented anionic chains constructed by distorted [PbX4 O2 ] (X=I, Br) polyhedrons. Both the theoretical studies and the dipole moment calculations uncover that their SHG effects are mainly originated from the distorted [PbX4 O2 ] (X=I, Br) polyhedrons. Remarkably, Cs3 Pb2 (CH3 COO)2 I5 exhibits strong phase-matching SHG response (8×KDP) and large birefringence (0.26@ 1064 nm). Moreover, Cs3 Pb2 (CH3 COO)2 X5 (X=I, Br) also possess high laser damage threshold (LDT) which are almost 27 and 41 times that of AgGaS2 , respectively.