Performance degradation mechanism of the light-activated room temperature NO2 gas sensor based on Ag-ZnO nanoparticles

• Published in: Applied surface science 2021-03, Vol.541, p.148418, Article 148418
• Main Authors: Zhang, Qiuping, Pang, Zemei, Hu, Wenyu, Li, Jing, Liu, Yutong, Liu, Yiliang, Yu, Fei, Zhang, Chuanwu, Xu, Ming
• Format: Article
• Language: English
• Subjects: Ag-ZnO nanoparticles; Dark conductivity; Light-activated NO2 sensors; Performance degradation; Photoconductivity
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.148418

[Display omitted] •Performance of the light-activated NO2 sensor degraded by long-term operation.•Superior long-term stability of sensor under visible light than that under UV light.•Deteriorated crystal quality and increased oxygen vacancy defects are main reasons.•Elucidation of the performance degradation mechanism. The chemiresistor-type sensors based on Ag-ZnO nanostructures have shown excellent sensing properties to NO2 under visible light irradiation, however, they cannot escape from the destiny of the performances degraded by long-term operation. So, aiming at improving the long-term stability, the revelation of the essence of performance degradation is crucial and also a great challenge. Here, we comparatively investigated the change rules of NO2 sensing properties after running the as-fabricated Ag-ZnO nanoparticles-based sensor multiple times during 60 days under UV and visible light irradiation. It is demonstrated that the room temperature light-activated (especially UV light) NO2 sensing performances (response and sensitivity) of the sensor degrade after running multiple times. The degraded performances can be attributed to the deteriorated crystal quality and increased oxygen vacancy defects of the sensing materials, and oxidization of more Ag0 into Ag+ on the ZnO surfaces, which greatly increase the free charge carrier concentration in the dark and decrease photogenerated charge carrier concentration under light irradiation. Correspondingly, the photoconductivity of the device declines and its output resistance signal weakens. This work offers not only a fundamental understanding of the performance degradation of the light-activated room temperature NO2 gas sensor, but also a strategy for the study on the performance degradation mechanism of other devices.