Interfacial and Defective Construction from Diverse CuxSy Quantum Dots toward Broadband Carbon-Based Microwave Absorber

In this study, highly monodisperse copper sulfide (Cu_xS_y) quantum dots (QDs) have been successfully obtained using a ligand-chemistry strategy, and then a variety of S-deficient Cu_xS_y/nitrogen-doped carbon (NC) heterointerfaces are constructed by compositional fine-tuning (Cu₉S₅ → Cu_1.96S → Cu). First-principles calculations show that the S-deficient domains of Cu_xS_y QDs and N-doped domains of carbon synergistically enhance the electron transfer from Cu_xS_y to NC. In addition, the finite element simulations demonstrate that the diverse Cu_xS_y QDs exhibit their intrinsic size and dielectric confinement effects to precisely manipulate the electric field distortion and improve the relaxation polarization. Consequently, Cu_xS_y@NC achieves excellent impedance matching and a strong loss mode dominated by dielectric polarization. Among them, Cu_xS_y@NC-650 has a maximum effective absorption bandwidth of 7.7 GHz at 2.5 mm, while Cu_xS_y@NC-700 features a minimum reflection loss of -66.7 dB at 13.7 GHz, respectively. Furthermore, the simulations of radar cross-sections have confirmed that the Cu_xS_y@NC series is promising in the field of radar stealth.