Selective Ions Exchange Reactions Endow Defective Heterovalent Copper-Based Selenides With Enhanced Dielectric Polarization Response

Defective heterovalent selenides provide a spacious arena for creating emergent electromagnetic (EM) phenomena that are unattainable in the conventional constituent counterparts. However, there are still synthetic methodological challenges, and in-depth understanding of the EM properties, particularly correlation between tailored polarization sites and dielectric polarization response, are significantly inadequate. Herein, a selective ions exchange strategy driven by concentration-regulated (Case 1) and time-evoked (Case 2) approaches, is innovatively proposed to design series of defective heterovalent copper-based selenides. The controllable phase evolution tailored by concentration-regulated mixed cation/anion exchange is responsible for heterointerfaces levels (Case 1), while Cu⁺/Cu²⁺ electronic configurations controlled by time-evoked cation exchange accounted for further manipulating heterointerfaces/defects levels and enriching polarization sites (Case 2). The coupling of nonstoichiometric Cu_2−xSe-containing heterointerfaces, unsaturated Se vacancies and multi-valence configurations, rather than themselves alone even at a higher level, imparted abundant polarization sites to trigger boosted polarization response for defective heterovalent selenides. Consequently, this designed defective heterovalent selenide (ZnSe/CuSe/Cu_2-xSe) deliveres a broad bandwidth of 6.89 GHz compare to parent ZnSe without dielectric response, outperforming most reported metal selenides until now. This innovative strategy overcame the bottlenecks of conventional synthetic methodology, providing a paradigm for fabricating sophisticated defective heterovalent materials for versatile applications beyond EM absorption.