Cs₄CuSb₂Cl₁₂ Nanostructured Layered Films for Humidity and Temperature Sensing Applications

We report the humidity and temperature sensing capabilities of Cs4CuSb2Cl12 (CCSC) vacancy-ordered double perovskite nanostructured layered films along with their reversible thermochromic behavior. CCSC-based two-probe devices demonstrate strong temperature current sensitivity and stable electrical responses over multiple heating and cooling cycles. UV–vis absorption measurements reveal a high absorption coefficient near the visible range, which decreases with increasing temperature. The band gap shows a reversible shift from a narrow to a wider value, accompanied by a visible color change from black to yellow. Temperature-dependent X-ray diffraction (XRD) and Raman spectroscopy measurements indicate a structural transformation from a monoclinic phase to a mixture of orthorhombic and trigonal phases at elevated temperatures with stability maintained up to 140 °C under ambient conditions. Under varying humidity (20–80%RH), the films exhibit fast response and recovery times, stable operation over 10 days, and high current sensitivity. These results underscore the potential of CCSC films for multifunctional sensing and chromic applications.