Coupling vanadium oxide and lead-free perovskite for sustainable passive daytime radiative cooling

A key factor in effectively integrating passive daytime radiative coolers (PDRC) into the built environment is conferring them the ability to adapt to external stimuli. Vanadium Dioxide (VO2) has been proposed for radiative cooling applications due to its reversible insulator-to-metal transition, which induces significant changes in optical properties. However, the aesthetic limitations of black VO2 and highly reflective metallic substrates have hindered widespread adoption in urban contexts. This study introduces a novel approach by coupling the temperature-dependent switchable behavior of VO2 with the tunable bandgap properties of lead-free perovskite nanocrystals to develop scalable, self-regulating radiative coolers. VO2 was synthesized via two strategies — polyol and hydrothermal (Ttransition=66 °C–64 °C)— and incorporated into a polymer matrix to produce PMMA films with varying VO2 concentrations. Comprehensive thermo-optical and morphological analyses were conducted to identify the most suitable configurations for integration into PDRC devices (τsol=0.90, ϵMIR=0.76). Additionally, incorporating lead-free perovskites into PMMA resulted in scalable colored layers with excellent photoluminescent emissions (λemission=420,525,580 nm). The combination of VO2-perovskite multilayers with reflective substrates offers an innovative strategy for PDRC applications. The resulting structures exhibit dynamically adaptive thermal emission and a twofold shortwave radiation rejection mechanism — reflection and photoluminescence — positioning them as promising solutions for urban environments.