Interfacial and Defective Construction from Diverse Cu_<i>x</i>S_<i>y</i> Quantum Dots toward Broadband Carbon-Based Microwave Absorber

In this study, highly monodisperse copper sulfide (Cu_<i>x</i>S_<i>y</i>) quantum dots (QDs) have been successfully obtained using a ligand-chemistry strategy, and then a variety of S-deficient Cu_<i>x</i>S_<i>y</i>/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_<i>x</i>S_<i>y</i> QDs and N-doped domains of carbon synergistically enhance the electron transfer from Cu_<i>x</i>S_<i>y</i> to NC. In addition, the finite element simulations demonstrate that the diverse Cu_<i>x</i>S_<i>y</i> QDs exhibit their intrinsic size and dielectric confinement effects to precisely manipulate the electric field distortion and improve the relaxation polarization. Consequently, Cu_<i>x</i>S_<i>y</i>@NC achieves excellent impedance matching and a strong loss mode dominated by dielectric polarization. Among them, Cu_<i>x</i>S_<i>y</i>@NC-650 has a maximum effective absorption bandwidth of 7.7 GHz at 2.5 mm, while Cu_<i>x</i>S_<i>y</i>@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_<i>x</i>S_<i>y</i>@NC series is promising in the field of radar stealth.