All solution processed flexible p-NiO/n-CdS rectifying junction: Applications towards broadband photodetector and human breath monitoring

Abstract Solution processable flexible devices meet the rising demand of sensors in wearable electronics owing to their cost-effective fabrication process with large area and throughput. This report demonstrates the multifunctional sensor based on p-NiO/n-CdS rectifying junction on ITO coated PET flexible substrate using low-temperature all solution processed deposition technique for UV–vis photodetection and breath monitoring applications. Under UV and visible light, the fabricated device exhibited strong current rectifying activity of approximately four orders. The responsivity (R) of the device underneath UV and visible illuminations found to be ~40.43 mAW−1 and ~25.96 mAW−1, respectively. Further, the device showed a response time of ~3.2 sec and detectivity of 1.4 × 1010 Jones under UV illumination. The internal electric field created at the p-NiO and n-CdS interface due to the formation of excellent rectifying junction assists in the efficient separation of photo-generated electron-hole pairs, thus improving the responsivity. Furthermore, the fabricated device was used as a breath sensor, and it was evaluated for different breath patterns of an individual. Interestingly, the device was able to distinguish between the different breath patterns (slow, fast, deep, etc.) The fabricated device displayed a negligible change in performance even after harsh deformations, indicating the flexibility and robustness of the device.