Quasi-linear CuX2 (X = Cl, Br) motif-built hybrid copper halides realizing encouraging nonlinear optical activities

Abstract

The emerging organic-inorganic hybrid metal halides feature unique optical and electronic properties, are easily grown and have flexible crystal structures, making them a class of promising next-generation nonlinear optical (NLO) and ferroelectric materials. Herein, we successfully synthesized two centimeter-level zero-dimensional copper halide organic-inorganic hybrids (C20H20P)CuX2 (X = Cl, Br) that are crystallized in the monoclinic noncentrosymmetric P21 space group. Their structures contain rare quasi-linear [CuX2]- anions and [C20H20P]+ cations. (C20H20P)CuCl2 and (C20H20P)CuBr2 crystals show phase-matchable NLO effects around 1.1 and 0.87 times that of benchmark KDP, respectively. These (C20H20P)CuX2 materials are the first NLO-active examples in the hybrid copper(i) halide family containing a quasi-linear CuX2 unit.