Cs 3 Pb 2 (CH 3 COO) 2 X 5 (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, Cs 3 Pb 2 (CH 3 COO) 2 X 5 (X=I, Br), have been rationally synthesized by introducing acetate groups into lead halide perovskites under moderate solvothermal conditions. Cs 3 Pb 2 (CH 3 COO) 2 X 5 (X=I, Br) feature highly oriented anionic chains constructed by distorted [PbX 4 O 2 ] (X=I, Br) polyhedrons. Both the theoretical studies and the dipole moment calculations uncover that their SHG effects are mainly originated from the distorted [PbX 4 O 2 ] (X=I, Br) polyhedrons. Remarkably, Cs 3 Pb 2 (CH 3 COO) 2 I 5 exhibits strong phase‐matching SHG response (8×KDP) and large birefringence (0.26@ 1064 nm). Moreover, Cs 3 Pb 2 (CH 3 COO) 2 X 5 (X=I, Br) also possess high laser damage threshold (LDT) which are almost 27 and 41 times that of AgGaS 2 , respectively.