Composition‐Dependent Photoluminescence Properties and Anti‐Counterfeiting Applications of A₂AgX₃ (A = Rb, Cs; X =  Cl, Br, I)

Abstract

Copper(I) halides are emerging as attractive alternatives to lead halide perovskites for optical and electronic applications. However, blue-emitting all-inorganic copper(I) halides suffer from poor stability and lack of tunability of their photoluminescence (PL) properties. Here, the preparation of silver(I) halides A 2 AgX 3 (A = Rb, Cs; X = Cl, Br, I) through solid-state synthesis is reported. In contrast to the Cu(I) analogs, A 2 AgX 3 are broad-band emitters sensitive to A and X site substitutions. First-principle calculations show that defect-bound excitons are responsible for the observed main PL peaks in Rb 2 AgX 3 and that self-trapped excitons (STEs) contribute to a minor PL peak in Rb 2 AgBr 3 . This is in sharp contrast to Rb 2 CuX 3 , in which the PL is dominated by the emission by STEs. Moreover, the replacement of Cu(I) with Ag(I) in A 2 AgX 3 significantly improves photostability and stability in the air under ambient conditions, which enables their consideration for practical applications. Thus, luminescent inks based on A 2 AgX 3 are prepared and successfully used in anti-counterfeiting applications. The excellent light emission properties, significantly improved stability, simple preparation method, and tunable light emission properties demonstrated by A 2 AgX 3 suggest that silver(I) halides may be attractive alternatives to toxic lead halide perovskites and unstable copper(I) halides for optical applications.

High-Performance Copper-Doped Perovskite-Related Silver Halide X-ray Imaging Scintillator

“…In addition, the long carrier decay time of copper halide scintillators (i.e., on the order of microseconds) also restricts their real-time detection capability. , Since the ability to attenuate X-rays is mainly determined by the effective atomic number of a material, lead-free silver halides, which possess a higher atomic number and exhibit a shorter decay time than copper halides, could be exploited as excellent alternatives . Several polycrystalline silver halide powders and single crystals with tunable emission have been synthesized recently, albeit through expensive solid-state techniques. , Unfortunately, polycrystalline powders have exhibited extra Cs-related peaks in their X-ray diffraction patterns, implying poor phase purity. Moreover, Cu-doped silver halide single crystals have demonstrated an unsatisfactory light yield of ∼27 000 photons/MeV, which lags far behind the yield of the commercial X-ray scintillators mentioned above .…”

Bright Cyan‐Emissive Copper(I)‐Halide Single Crystals for Multi‐Functional Applications

“…[35] For instance, the emission of A 2 AgX 3 (A = Rb, Cs; X = Cl, Br, I) could be facilely regulated by changing the composition, showing the application potential in fluorescence anti-counterfeiting. [36] Nevertheless, the limited response range makes traditional UV light-activated anti-counterfeiting fluorescence tags unsatisfactory for the requirements of high-level anticounterfeiting applications. Therefore, exploring complicated anti-counterfeiting fluorescent materials whose response range can be broadened from UV to near-infrared (NIR) light and even X-rays are urgently needed.…”

Zero‐Dimensional Zn‐Based Halides with Ultra‐Long Room‐Temperature Phosphorescence for Time‐Resolved Anti‐Counterfeiting

“…Over the past decades, the ever‐increasing prevalence of banknote counterfeiting, document forgery, and product counterfeiting have prompted us to develop advanced anti‐counterfeiting technologies [1–3] . Fluorescence‐tag‐based anti‐counterfeiting technology has been highlighted with a facile decryption process, simple device requirement, and low preparation cost [4, 5] . Nevertheless, the clonable decryption of conventional spatial‐resolved fluorescence tags largely restricts their application in high‐security‐level anti‐counterfeiting.…”

“…[1][2][3] Fluorescence-tag-based anticounterfeiting technology has been highlighted with a facile decryption process, simple device requirement, and low preparation cost. [4,5] Nevertheless, the clonable decryption of conventional spatial-resolved fluorescence tags largely restricts their application in high-security-level anti-counterfeiting.…”