Perovskite materials have exhibited promising potential for universal applications including backlighting, color conversion, and anticounterfeiting 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 polyvinylpyrrolidone (PVP), precisely controlling the inkjet printing technique, and using a postprocessing 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 macroscale and high reproducibility on a microscale; 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 anticounterfeiting labels.

Perovskite quantum dots (PeQDs) have emerged as a new kind of nanomaterial in various applications, especially light-emitting diodes (LEDs). However, the synthesis of PeQDs is relatively complicated and the electron transport layer (ETL) is usually fabricated in a vacuum because of the dissolution of PeQDs films in organic solvents, which will increase the difficulty and cost in mass production. Here, a simple one-step "ultrasonic bath" treatment to synthesis PeQDs is adopted and applied into the PeQDs-LEDs. Meanwhile, an all-solution process is developed to fabricate PeQDs-LEDs based on the solvent engineering strategy. By using methyl acetate (MeOAc) as the solvent of ETL, the all-solution-processed PeQDs-LEDs exhibit bright luminance with the maximum current efficiency of 3.26 cd/A. This work is simple and easy to be scaled up, which will pave a new way to the low-cost all-solution processable PeQDs-LEDs.