Robust embedded CsPbI ₃ perovskite-polymer films via in situ fabrication for high-performance underwater temperature sensing

Perovskite materials have garnered significant attention due to their exceptional optoelectronic properties. However, their susceptibility to moisture-induced degradation has severely limited their practical applications. In this study, we present an in situ fabrication strategy to embed all-inorganic CsPbI 3 perovskite quantum dots within a polyacrylonitrile (PAN) polymer matrix, resulting in a flexible, water-resistant composite film. The film exhibits a high photoluminescence quantum yield (PLQY) of over 60%, significantly surpassing that of bare perovskite films (∼22%), and maintains structural and optical stability after prolonged water immersion. Temperature-dependent photoluminescence (PL) studies from 80 K to 300 K reveal insights into exciton binding energy, phonon interactions, and thermal quenching behavior. Furthermore, the film functions as an excellent temperature sensor in aqueous environments from 20 °C to 100 °C, exhibiting high linearity (R 2 ≈ 0.96), sensitivity, and complete reversibility. The proposed synthesis method is versatile, applicable to various perovskite compositions and polymer matrices, and enables the production of freestanding films suitable for diverse optoelectronic applications, including sensing, displays, and wearable devices.