Reinforced Nonlinear Optical Performances Induced by P‐P Homoatomic Bond in Phosphide SrIn ₃ Si ₄ P ₁₁

Abstract Phosphides exhibit great promise as a nonlinear optical (NLO) material system; however, the challenge of simultaneously achieving robust second‐harmonic generation (SHG) response, wide band gap, and large birefringence within a single structure remains daunting. Herein, by leveraging the design concept of “multi‐asymmetric‐module integration”, we have successfully harvested a brand‐new non‐centrosymmetric phosphide SrIn 3 Si 4 P 11 , which showcases the characteristics of a three‐dimensional framework constructed by diverse [Si 3 P 10 ] and [In 3 P 10 ] trimers, as well as P−P homoatomic bonds. The introduction of P−P bond distinguishes SrIn 3 Si 4 P 11 from the kindred SrIn 3 Si 4 P 9 , ultimately resulting in “killing three birds with one stone”, including a remarkable 30‐fold enhancement in SHG intensity, a 2.5‐fold increase in birefringence, as well as a 0.50 eV broadening in band gap compared to SrIn 3 Si 4 P 9 . Theoretically calculated analysis reveals that the π interactions and the significant polarization anisotropy of the P−P bond are critical factors contributing to the enhancement of NLO performances. The present study uncovers the pivotal significance of P−P bond in structural design and NLO properties optimization, and delineates a clear research direction for the extensive advancement of phosphides NLO materials.