Self-powered gas sensor based on SiNWs/ITO photodiode.

Silicon nanowires (SiNWs) with a large surface-to-volume ratio and a low reflectivity are exceedingly attractive building blocks for developing high performance light harvesting devices. Herein, a SiNW/ITO heterojunction was fabricated easily by just compressing the SiNWs and ITO electrode together with a suitable pressure. Under light illumination, the SiNWs/ITO with an optimized structure can generate more than 20 μA photocurrent at zero bias voltage. In the mean time, the photocurrent is very sensitive to NO infiltration into the forest of SiNWs and displays a non-linear relationship with the concentration of NO from 0 to 1000 ppb. In comparison with chemiresistive sensors based on SiNWs only, the sensitivity of the self-powered sensor was improved obviously, showing a limit of detection at ∼5 ppb. The excellent light trapping and sensing performance was attributed to the heterojunction formed between SiNWs and ITO. Since the nano-photodiode device can monitor the surrounding gas without an external power supply, it will ensure that sensor networks can operate independently and sustainably without a battery or at least by extending the life time of a battery. This work may push forward the development of self-powered microsensors using rationally designed nanojunctions.