Modulation of Built‐In Electric Fields via Doping Strategy for Efficient Electromagnetic Response

ABSTRACT Developing the built‐in electric field (BIEF) to enhance dielectric loss is a promising approach for optimizing electromagnetic (EM) response and absorption efficiency. However, the mechanistic links between BIEF and dielectric responses remain elusive, and the effective strategies for precisely tuning BIEF intensity and charge distribution are still limited, hindering the rational design of EM wave attenuation materials. Herein, hierarchical nanoflower‐like MoSe 2 /C and X‐doped MoSe 2 /C (N, P, F, and Cl) heterojunctions are synthesized via a facile one‐step solvothermal method. Experimental and theoretical results demonstrate that the spontaneous formation of BIEF, induced by the work function difference between MoSe 2 and carbon, significantly elevates dielectric loss. Atomic‐scale doping enables interfacial engineering through bidirectional work function modulation, allowing for precise control over local charge density and BIEF intensity. This tunable BIEF directionally confines interfacial charges, thereby exhibiting enhanced polarization relaxation. The findings demonstrate that coupling BIEF generation with intensity tunability leads to a significant enhancement in EM wave absorption from pure MoSe 2 to MoSe 2 /C and doped heterostructures. Specifically, the optimized N‐doped MoSe 2 /C exhibits an outstanding effective absorption bandwidth of 6.40 GHz and a minimum reflection loss of −50.78 dB. Generally, this BIEF modulation via doping offers a generalizable paradigm for constructing high‐performance EM wave absorbers.