A carbon nanotube@silicon-based three-dimensional porous photo-supercapacitor for self-powered UV detection

Miniaturized self-powered energy devices are indispensable units for next-generation portable electronics. Photo-supercapacitors (PSCs), as a reliable energy harvesting device, have been explored for self-powered applications by utilizing the photovoltaic effect of micro-supercapacitors. In this paper, we propose a self-powered PSC with bulk micro-machined three-dimensional (3D) porous asymmetric electrodes with a high-aspect ratio via deep reactive-ion etching (DRIE) technique for the detection of ultra-violet (UV) radiance. The as-fabricated porous CNT@TiC/CNT@TiO2 PSC delivers an areal capacitance of 2.69 mF/cm2 (@5 mV/s) and 7.35 mF/cm2 (@20 μA/cm2) before and after photo-charge process, respectively. The optical response of the PSC is linearly proportional to the UV power intensity with a photoresponsivity of 14.8 mA/W. A photocurrent density of 354 μA/cm2 and a photo-to-dark current ratio of 12 are experimentally obtained under a UV power intensity of 15 mW/cm2. The as-prepared PSCs are further integrated on-chip to implement a UV leakage warning system that can drive a white LED for more than 60 s under a UV power intensity of 10 mW/cm2, fully demonstrating the practical application of the 3D silicon-based device in UV monitoring systems.