Dual-tunable MXene-VO ₂ hybrid metamaterials for solar energy harvesting and environmental monitoring via absorption modulation

Solar thermo-photovoltaics (STPV) offer a promising route to next-generation solar energy conversion by enhancing efficiency through photothermal mechanisms. However, achieving broadband tunability and long-term material stability remains a significant challenge in the design of functional photonic absorbers. In this work, we present a novel multifunctional metamaterial absorber that integrates plasmonic MXene (Ti₃C₂T_x) with thermochromic VO₂, encapsulated within a durable nanoscale Al₂O₃ framework. The proposed architecture combines optical tunability with robust environmental stability, addressing critical limitations of existing MXene-based designs. Using finite difference time domain (FDTD) simulations, we demonstrate that the absorber achieves an average solar absorption efficiency of 96.05% under AM (Air Mass) 1.5 conditions, with only 3.95% energy loss. A thermally activated phase transition in the VO₂ layer enables dynamic optical switching, reducing absorption from over 80% at low temperature to below 20% above 68°C. The broadband response is governed by hybridized localized surface plasmon resonances (LSPRs) within the MXene core, which can be tuned via temperature, voltage, and geometry. Operating across the 0.4-3 <i>μ</i>m spectral range, by tunining the voltage the absorber is uniquely suited for multifunctional applications including smart optical filters, reconfigurable photonic circuits, energy-efficient smart windows, and near-infrared biomedical imaging, offering dynamic light modulation in both the visible and NIR domains. Additionally, the device exhibits strong spectral sensitivity to gases like NH₃ and CO₂, enabling real-time environmental sensing. The dual functionality of optical modulation and gas detection makes this absorber a compelling platform for scalable smart photonic systems, with potential applications in solar energy harvesting, energy-efficient smart windows, optical switching, and environmental monitoring.