The growing complexity of artificial intelligence-driven devices requires multifunctional materials that exhibit nonlinear responses to address key challenges in adaptive signal processing and energy-efficient computing. To meet these demands, hexagonal Bi₂Se₃ ceramics are synthesized with controlled thicknesses via a chemical reduction synthesis method. The aggregated Bi₂Se₃ nanosheets exhibit remarkable capacitance tunability under an applied bias voltage. Moreover, a significant increase in the electromagnetic interference (EMI) shielding performance was achieved at a bias voltage, which was attributed primarily to improved electrical conductivity. At a bias voltage of 15 V and an optical power density of 200 mW/cm², the average total EMI shielding effectiveness (SE_T) of Bi₂Se₃ nanosheets increases to 62.8 from 23.9 dB. The collaborative combination of multiple superior functionalities within a single material platform with tunable capacitance, dynamically tunable EMI shielding, and excellent light response endows Bi₂Se₃ nanosheets with great potential for applications in intelligent storage, microelectronics, and low-light photodetectors.