Self‐Aligned Non‐Centrosymmetric Conjugated Molecules Enable Electro‐Optic Perovskites

Abstract Solution‐processed organic electro‐optic (EO) chromophores are well suited for integration in optical modulators on silicon photonics chips. They contain highly conjugated molecules with polar functional groups offering large dipoles and a large nonlinear optical response. However, these molecules form centrosymmetric aggregates that hinder poling efficiency and the resultant macroscopic EO response. Furthermore, at elevated temperatures, the alignment of poled molecules can be lost, leading to a reduction in the EO response. Inorganic EO materials exhibit excellent thermal stability but lower performance. Here 2D metal halide perovskite scaffolds that align EO molecules are reported. The approach heralds a material design strategy that combines the features of organic and inorganic EO materials. The EO material exhibits promising thermal stability with a performance approaching that of organic EO materials. Anchor diammonium non‐centrosymmetric molecules are anchored inside a 2D metal halide perovskite scaffold, thereby avoiding aggregation. The authors lever the thermal stability of this compound and pole the organic molecules under an electric field at 533 K. The 2D perovskites exhibit a macroscopic EO coefficient of 68 pm V⁻¹—a twofold increase over LiNbO₃. Density functional theory calculations show that the in‐plane alignment of the molecular dipole moments can account for the EO response.