Temperature-tunability of perovskite quasi-bound states in the continuum-metastructure for enhanced terahertz performance and CO2 sensing.

This study explores the optical and mechanical properties, along with the thermodynamical and thermal stability of methylammonium lead iodide (MAPbI3), specifically for terahertz (THz) applications, utilizing first-principles density functional theory and finite element analysis. The refractive index of MAPbI3 remains stable in the THz region, showing no dispersion or loss, and can be finely tuned by temperature, exhibiting pronounced changes around the 60 °C phase transition. We propose a tunable metastructure that integrates MAPbI3, featuring periodic circular slot rings, to investigate bound states in the continuum (BICs) and quasi-BICs. By employing symmetry-breaking techniques, we effectively convert BICs into quasi-BICs, revealing temperature-tunable frequency shifts and quality factors that highlight the potential for innovative THz optoelectronic devices. Furthermore, our research examines the structure's capability for carbon dioxide gas sensing, achieving impressive results with a maximum sensitivity of 0.301 THz/RIU and a figure of merit of 1.911 × 105.