Fluorescent Microarrays of in-Situ Crystallized Perovskite Nanocomposites Fabricated for Patterned Applications by Using Inkjet Printing.

Perovskite materials have exhibited promising potential for universal applications including backlighting, color conversion, and anti-counterfeiting labels fabricated using solution processes. However, owing to the tendency of those materials to have uncontrollable morphologies and to form large crystals, they cannot be utilized in discontinuous microminiaturization, which is crucial for practical optoelectronic applications. In this research, combining the effects of adding polyvinyl pyrrolidone (PVP), precisely controlling the inkjet printing technique, and using a post-processing procedure, we were able to fabricate in-situ crystallized perovskite-PVP nanocomposite microarrays with perfect morphologies. The viscosity of the perovskite precursor increased with the addition of PVP, eliminating the outward capillary flow that induces the coffee-ring effect. In addition, because of the presence of metallic bonds with the C=O groups in PVP and the spatial confinement of such a polymer, we were able to fabricate regulated CsPbBr3 nanocrystals capped with PVP and with a uniform size distribution. The as-printed patterns showed excellent homogeneity on a macro scale and high reproducibility on a micro scale; furthermore, those patterns were invisible in the ambient environment, compatible with flexible substrates, and cost efficient to produce, indicating that this technique holds promising potential for applications such as anti-counterfeiting labels.