Synergistic engineering of multivariate heterointerfaces and multiple built-in electric fields for high-performance electromagnetic wave absorption

Multivariate heterostructure engineering has emerged as a promising paradigm for designing high-performance microwave absorbing materials (MAMs). Conventional dielectric absorbers often suffer from narrow bandwidths, limited polarization loss, and impedance mismatch, which restrict their practical utility. In this study, we demonstrate a rational multi-step synthesis strategy that integrates electrostatic adsorption, in-situ reduction, and selenization to construct a novel semiconductor–semiconductor–metal heterostructure (Co₃Se₄/TiO₂/Ti₃C₂T_x, denoted as CSTT). Comprehensive experimental characterization, coupled with first-principles calculations, indicates that the synergistic band alignment at the semiconductor heterojunction (Co₃Se₄/TiO₂) and the Mott–Schottky junction (TiO₂/Ti₃C₂T_x) leads to the formation of multiple built-in electric fields (BIEFs) at the interfaces, which collectively enhance the electromagnetic wave (EMW) absorption performance. This innovative interface engineering not only significantly strengthens interfacial polarization effects to improve dielectric loss capability, but also achieves optimal impedance matching through gradient impedance characteristics derived from the multi-heterogeneous interfaces. The optimized CSTT-2 composite exhibits exceptional microwave absorption (MA) properties, achieving a minimum reflection loss (RL_min) of −54.7 dB and an effective absorption bandwidth (EAB) of 5.4 GHz. Additionally, radar cross-section (RCS) simulations demonstrate that a metal plate coated with this composite realizes a remarkable radar signal attenuation of 24.9 dB·m² under vertical EMW incidence (θ = 0°), indicating superior radar stealth performance. The proposed strategy of modulating multiple BIEFs provides a novel design principle for developing advanced MAMs with integrated “broadband–strong absorption” and radar stealth characteristics.