High-Capacity Optical Fingerprinting Using Dual-Peak Photoluminescence of Quantum Dots

Counterfeiting and unauthorized duplication continue to pose significant threats across industries, ranging from electronics to pharmaceuticals. In response to this challenge, we present a novel optical fingerprinting platform based on cadmium-free CuInS₂/ZnS quantum dots (QDs), which exhibit a distinctive dual-peak photoluminescence (PL) signature. Time-resolved PL (TRPL) analysis confirms the distinct recombination origins of the two peaks, supporting the assignment to core- and interfacial/shell-related states. Our approach extracts two intrinsically coupled emissions from a single QD type, where both peaks originate within the same nanostructure, making the fingerprint inherently unclonable. This phenomenon enables the generation of rich tunable spectral profiles across a selected range of excitation wavelengths. Using spectral-to-digital processing, we extracted three features from both emission peaks under 10 excitation wavelengths to generate binary fingerprints. The resulting theoretical encoding capacity is estimated to be 1.2 × 10¹⁸ compared to an experimental error probability of ∼3 × 10^-17. These findings validate the strength and security of the proposed fingerprinting system, highlighting its practical potential for anticounterfeiting applications.