New Prospects in Built‐In Electric Fields for Electromagnetic Wave Absorption: from Fundamentals to Interdisciplinary Applications

Construction of built‐in electric fields (BIEFs) in nanohybrids has been corroborated as a robust strategy for modulating the electromagnetic response by manipulating the charge redistribution and built‐in electrostatic potential gradients, thereby enhancing the dielectric polarization attenuation. Nevertheless, substantial challenges persist in the comprehensively elucidation and reinforcement of BIEFs from both micro and macro perspectives. Herein, this review systematically elucidates the role of BIEFs in electromagnetic waves (EWs) protection. First, the fundamental principles of BIEFs are systematically outlined, including key concepts, response mechanisms, and characterization techniques. Then, the main optimization strategies‐particularly morphology regulation and defect engineering‐are critically examined to enhance BIEFs effect. The EWs absorption capabilities of representative BIEF‐based absorbers are further dissected, categorized by semiconductor–semiconductor junctions, metal–semiconductor heterostructures, and van der Waals interfaces. Subsequently, a concise summary highlights the effective strategies to optimize the overall performances of BIEFs type absorber. Furthermore, interdisciplinary perspectives are introduced by focusing on the integration of BIEFs with energy conversion, EWs responsive photocatalysts and smart detectors/sensors. Finally, current challenges and future development directions of BIEF engineering are rationally discussed, offering valuable insights for the design of high‐efficiency smart EWs absorbers.