Stable Ultrathin Perovskite/Polyvinylidene Fluoride Composite Films for Imperceptible Multi‐Color Fluorescent Anti‐Counterfeiting Labels

Abstract

techniques have been proposed and developed. [10][11][12][13][14] Among them, the fluorescent label may be more prominent with its easy fabrication, low cost, and high yield. Diverse fluorescent materials have been introduced to fabricate fluorescent labels, including organic quantum dots (QDs), [15][16][17] inorganic QDs, [18,19] and rareearth compounds. [20][21][22] Owing to their exotic photo-physical characteristics: tunable bandgap, [23] high visible-light absorption, [24] and high quantum yield, [25,26] perovskite materials have been the promising candidate for optoelectronic devices, which could help the fluorescent label with its value in the anti-counterfeiting of information security. However, the poor stability of perovskite materials within the ambient conditions, especially under humidity, remains the obstacle to their widespread applications. Several strategies have been put forward to improve the stability, such as composition modulation, [27] surface passivation, [28] and matrix encapsulation. [29,30] Thereinto, the matrix encapsulation with compact polymer chain could effectively shelter perovskite materials from water molecular. Zhou and co-workers have enhanced the humidity stability and thermal stability of perovskite composite film by embedding perovskite nanocrystals (NCs) in polymer matrix. [30] Meantime, the photoluminescence (PL) was also enhanced due to the in-situ formation of perovskite NCs in polymer matrix. [31] Hydrophobic polyvinylidene fluoride (PVDF) was introduced to improve the stability of perovskite fluorescent labels in water, saline, ethanol, dichloromethane and so on. After 120 h in water, the fabricated fluorescent labels still maintained the almost original fluorescent intensity, which exhibited its high stability.In addition, the fabrication of well-patterned perovskite arrays remains to be challenging, which sets limits in the applications of those flexible and ultrathin fluorescent labels. Generally, patterned perovskite arrays could be synthesized via anodized aluminum (AAO) template, [32] epitaxial growth, [33] and chemical vapor deposition, [34,35] which are not suitable for perovskite/PVDF composite films due to the decomposition under severe environment such as organic solvent or high temperature in the fabrication process. Therefore, a feasible fabrication protocol for patterned perovskite arrays of flexible and ultrathin fluorescent labels is most expected.As an essential part of information security in the Internet of Things (IoT), fluorescent labels possess a principal portion of anti-counterfeiting due to its easy fabrication, low cost, and high yield. Here an ultrathin, stable, and patterned multi-color fluorescent label with perovskite/polyvinylidene fluoride composite film is presented, which registers a resolution of 56.4 dpi and almost maintains its original fluorescent intensity after being immersed in water for 120 h. The variable color of fluorescent labels will improve the anticounterfeiting dimensions for the information security due to precise hal...

Recent Patterning Methods for Halide Perovskite Nanoparticles

“…Many researchers have attempted to overcome this problem by fabricating a template for patterning perovskites via photolithography. [34][35][36][37][38] Research into patterning via additional templates is ongoing. A significant factor in template-based Halide perovskites emerge as attractive materials because of their superior optical and optoelectrical properties.…”

“…The research demonstrates that concentric morphologies can be effectively applied to lasers. Template-assisted patterning CsPbX 3 (X = Cl/Br, Br, Br/I) Laser [40] Template-assisted patterning MAPbBr 3 Laser [41] Template-assisted patterning MAPbI 3 Laser [42] Template-assisted patterning MAPbBr 3 Laser [43] Template-assisted patterning MAPbI 3 Laser [44] Template-assisted patterning PEA 2 PbBr 4 X-ray [34] Template-assisted patterning MAPbI 3 Solar cell [48] Template-assisted patterning MAPbI 3 Solar cell [45] Template-assisted patterning MAPbI 3 Solar cell [46] Template-assisted patterning MAPbI 3 Solar cell [47] Template Template-assisted patterning CsPbX 3 (X = Cl/Br, Br, Br/I) Fluorescent label [36] Template-assisted patterning FAPbI 3 Image sensor [54] Template-assisted patterning MAPbI 3 Image sensor [55] Template-assisted patterning CsPbBr 3 Photodetector [35] Template-assisted patterning MAPbX 3 (X = Br, I) LED, photodetector [56] Template-assisted patterning MAPbI 3 Field-effect transistor, Photodetector [57] Template-assisted patterning MAPbI 3 Terahertz device [37] Template-assisted patterning MAPbI 3 Thin film transistor [58] Template-assisted patterning CsPbBr 3 Electrochemical cell [38] Template-assisted patterning MAPbBr As mentioned earlier, the stability of perovskite patterning is limited. If the stability is low, the device is easily degraded by external conditions and the overall device characteristics (e.g., the light emission characteristics) deteriorate.…”

“…Many researchers have attempted to overcome this problem by fabricating a template for patterning perovskites via photolithography. [ 34–38 ] Research into patterning via additional templates is ongoing. A significant factor in template‐based patterning is determining whether the perovskites can be destroyed by contact with the template.…”

Bidirectional Photoresponse in Perovskite‐ZnO Heterostructure for Fully Optical‐Controlled Artificial Synapse

“…Regarding the photoresponsive materials, halide perovskites have attracted great attention because of their excellent optoelectronic properties, [14][15][16] and can be applied in sensor, memory, photovoltaic unit and light-emitting diode [17][18][19][20] for artificial intelligence, humanoid robotics, and flexible electronic etc. [21][22][23][24][25][26][27][28][29][30][31][32][33] Not only the phenomenon of negative photoresponse in halide perovskites has also been observed [34][35][36][37][38] but halide perovskites based synaptic devices have also been fabricated and studied.…”

High‐Resolution Patterning of 2D Perovskite Films through Femtosecond Laser Direct Writing

“…[14,15] In addition, with the reserved remarkable optoelectronic properties, the 2D perovskites tend to be promising candidates for stable and efficient optoelectronic devices. [16,17] For many practical applications, such as pixel arrays for displays, [18,19] image sensor arrays, and fluorescent anti-counterfeiting labels, [20][21][22][23][24] it is critical to develop an efficient technique to achieve controllable and precise fabrication of patterned 2D perovskite films. [25,26] To date, several methods have been proposed to fabricate patterned perovskites, such as photolithography, [26,27] micro/nanoimprinting, and inkjet printing.…”