Cationic doping induced sulfur vacancy formation in polyionic sulfide for enhanced electromagnetic wave absorption

Vacancy engineering has been shown to be an effective way to tune the electromagnetic parameters of electromagnetic wave (EMW) absorbers and improve their absorption properties. However, the current methods to induce the formation of sulfur vacancies are not enough, and the contribution of sulfur vacancies to EMW absorption has not been clearly described. This work proposes a method to induce sulfur vacancies generation in the Cu₂ZnSnS₄ (CZTS) system by cation doping. It is found that the formation of sulfur vacancies depends on reactivity with doping cations and the less reactive cation is more favorable for the formation of sulfur vacancies. Benefiting from the improved sulfur vacancies concentration, the defect-induced polarization and dipole polarization are greatly enhanced, which allows the EMW absorber to exhibit excellent EMW absorption performance. Therefore, the minimum reflection loss of the cation-doped CZTS reaches −61.80 dB at a thickness of 2.00 mm, and the effective absorption bandwidth reaches 6.29 GHz at 2.30 mm. This work not only expounds on the significant roles of sulfur vacancies in EMW absorption mechanism, but also presents a novel idea for defect construction of copper-based chalcogenide semiconductor materials.