Functional materials for flexible sensing applications

Recent advances in sensing technologies are enabling devices that combine high sensitivity, mechanical flexibility, and compatibility with scalable, large-area manufacturing. This thesis explores innovative flexible sensors based on emerging functional materials, targeting high-performance platforms for real-world applications. Two classes of devices are investigated: ionizing radiation detectors and pressure sensors. The first part focuses on ionizing radiation detectors employing lead-halide perovskites as active materials. These materials offer strong radiation absorption, efficient charge transport, and low-temperature, solution-based fabrication, making them highly attractive for flexible detection systems. A multi-scale study is conducted on solution-processed two-dimensional layered single crystals and polycrystalline films, combining macroscopic optoelectronic characterization and thermal spectroscopy of defect states with microscopic analysis of local structural and electronic properties. The results clarify charge transport and trapping mechanisms, including the first investigation of out-of-plane conduction, the nonlinear response to incident photon flux in flexible photoconductors, and the role of grain boundaries in polycrystalline thin films. Beyond solution processing, two dry fabrication approaches are developed. Perovskite–polymer dry-pressed composites enable thick, flexible active layers up to hundreds of micrometers, increasing interaction volume with radiation and achieving state-of-the-art detection of high-energy photons and protons using a single flexible device. In parallel, vacuum-deposited perovskite photodiodes demonstrate promising passive-mode X-ray detection, highlighting their potential for compact, low-power systems. The second part addresses flexible pressure sensors for monitoring industrial molding processes in collaboration with SACMI IMOLA S.C.. Two sensor types, a reduced graphene oxide piezoresistive device and a strain-based sensor, are compared for in situ pressure monitoring under harsh conditions. The results provide the first direct measurement of pressure during cellulose cap molding, with cross-validated reliability between the two sensing approaches.