Versatile Papertronics: Photo‐Induced Synapse and Security Applications on Papers

Paper is a readily available material in nature. Its recyclability, eco‐friendliness, portability, flexibility, and affordability make it a favored substrate for researchers seeking cost‐effective solutions. Electronic devices based on solution process are fabricated on paper and banknotes using PVK and SnO2 nanoparticles. The devices manufactured on paper substrates exhibit photosynaptic behavior under ultraviolet pulse illumination, stemming from numerous interactions on the surface of the SnO2 nanoparticles. A light‐modulated artificial synapse device is realized on a paper at a low voltage bias of −0.01 V, with an average recognition rate of 91.7% based on the Yale Face Database. As a security device on a banknote, 400 devices in a 20 × 20 array configuration exhibited random electrical characteristics owing to the local morphology of the SnO2 nanoparticles and differences in the depletion layer width at the SnO2/PVK interface. The security Physically Unclonable Functions (PUF) key based on the current distribution extracted at −1 V show unpredictable reproducibility with 50% uniformity, 48.7% inter‐Hamming distance, and 50.1% bit‐aliasing rates. Moreover, the device maintained its properties for more than 210 days under a curvature radius of 8.75 mm and bias and UV irradiation stress conditions. Electronic devices based on paper and banknotes are successfully developed using a solution process with PVK and SnO2 NPs. These devices display photosynaptic behavior under UV pulse illumination and achieved a 91.7% recognition rate using the Yale Face Database. For security applications, the 20 × 20 array configuration exhibits excellent performance, maintaining the same code under long‐term storage and bending conditions.