ScholarWorks@성균관대학교

초록

With the increase in the demand for wearable devices, temperature-sensing capability is an essential function for flexible and transparent applications. Particularly, the long-term stability of a device is highly desirable for use in daily life. In this study, a flexible and transparent self-powered temperature sensor with remarkable air stability was developed by employing a one-atom-thick monolayer graphene encapsulated with an extremely thin metal oxide layer. Graphene thermocouples were constructed by inducing p- and n-type doping on a high-quality monolayer graphene placed on a transparent polymer film. The entire graphene film was treated by a modulated oxygen plasma, which induced p-type doping with minimal defects on graphene. Half of the graphene was coated with polyethylenimine to form n-type graphene. The graphene p–n junction was encapsulated with a 14-nm-thick ultrathin Al2O3 using atomic layer deposition (ALD). The graphene thermocouple exhibited a high Seebeck coefficient of 81.6 ± 2.4 μV/K, high linearity with a coefficient of determination of 0.999, rapid response with a time constant of 0.59 s, low thermal hysteresis, and wide operating temperature range. Owing to the ALD-Al2O3 layer, the graphene thermocouple exhibited exceptional air stability, maintaining the Seebeck coefficient for 1028 days. Furthermore, the ultimate thinness of the graphene thermocouple rendered it with an extreme optical transmittance of 94.8 % at a wavelength of 550 nm and a small critical bending radius of 5.71 mm. © 2025

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