First-principles Studies of Second-Order Nonlinear Optical Properties of Organic-Inorganic Hybrid Halide Perovskites

Organic-inorganic hybrid halide perovskites have ignited tremendous interest for photovoltaic applications. However, their nonlinear optical response has not been studied although many of these structures lack the centrosymmetry and exhibit ferroelectricity. In this work, we employ our developed large-scale parallel, first-principles simulation tool (ArchNLO) to explore second-order nonlinear optical properties of a typical family of organic-inorganic hybrid halide perovskites, CH₃NH₃M X₃ (M = Ge , Sn , Pb ; X = Cl , Br , I ). We find that these hybrid perovskites exhibit second harmonic generation and a linear electro-optic effect. The nonlinear optical effects are strongly influenced by the types and positions of cations and anions, and the corresponding band gaps. In particular, the distorted cubic phase, which is essentially triclinic, of CH₃NH₃Sn_{I 3} shows significant second harmonic generation and an electro-optic effect, which are comparable with more widely used materials, such as Ga As . These second-order optical properties of organic-inorganic hybrid halide perovskites and their low-temperature, solution-based fabrication pave the way for achieving and implementing nonlinear optical devices with low cost.