Organic Light‐Emitting Physically Unclonable Functions

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Abstract The development of novel physically unclonable functions (PUFs) is of growing interest and fluorescent organic semiconductors ( f ‐OSCs) offer unique advantages of structural versatility, solution‐processability, ease of processing, and great tuning ability of their physicochemical/optoelectronic/spectroscopic properties. The design and ambient atmosphere facile fabrication of a unique organic light‐emitting physically unclonable function (OLE‐PUF) based on a green‐emissive fluorescent oligo( p ‐phenyleneethynylene) molecule is reported. The OLE‐PUFs have been prepared by one‐step, brief (5 min) thermal annealing of spin‐coated nanoscopic films (≈40 nm) at a modest temperature (170 °C), which results in efficient surface dewetting to form randomly positioned/sized hemispherical features with bright fluorescence. The random positioning of molecular domains generated the unclonable surface with excellent uniformity (0.50), uniqueness (0.49), and randomness ( p > 0.01); whereas the distinctive photophysical and structural properties of the molecule created the additional security layers (fluorescence profile, excited‐state decay dynamics, Raman mapping/spectrum, and infrared spectrum) for multiplex encoding. The OLE‐PUFs on substrates of varying chemical structures, surface energies and flexibility, and direct deposition on goods via drop‐casting are demonstrated. The OLE‐PUFs immersed in water, exposed to mechanical abrasion, and read‐out repeatedly via fluorescence imaging showed great stability. These findings clearly demonstrate that rationally engineered solution‐processable f ‐OSCs have a great potential to become a key player in the development of new‐generation PUFs.