Morphology, luminescence and the gravity sedimentation effect of flexible and highly stable CsPbBr3 nanocrystal patterns by the inkjet printing method

Abstract

All-inorganic CsPbBr₃ perovskites possess exceptional optoelectronic properties, with emerging applications in light-emitting diodes (LEDs), solar cells, photodetectors, etc. Particularly, high-resolution patterning of halide perovskites is highly demanded for flexible and wearable optical devices, owing to the advantages of high integration and compatibility. Nevertheless, improving the stability of CsPbBr₃ perovskites remains a big challenge, impeding the practical applications. To address this issue, a series of CsPbBr₃ perovskite solutions were inkjet-printed into the viscous polyvinylpyrrolidone (PVP) substrate to induce the in situ crystallization of CsPbBr₃ within the soft and transparent matrix. The underlying relationship between the luminescence and the crystalline morphologies is discussed in details. With controlled crystal growth, fine and well-defined rectangular CsPbBr₃ nanocrystals are favorable for the highly luminescent patterns, demonstrating strong green emission under excitation at 365 nm and 480 nm. The gravity sedimentation effect is evidenced as the main cause of the encapsulation of CsPbBr₃ nanocrystals within the PVP matrix. Along with the space confinement effect of the PVP layer, these flexible and transparent CsPbBr₃ nanocrystal patterns display excellent ambient stability, retaining over 80% of the fluorescence intensity even after 210 days of storage under ambient conditions. This work not only provides a deeper understanding of the crystallization mechanism of CsPbBr₃ within the soft polymer matrix, but also offers a novel approach for preparing wearable and flexible optical devices for LEDs and anticounterfeiting labels.