All MoS based 2D/0D localized unipolar heterojunctions as flexible broadband (UV-vis-NIR) photodetectors

This report demonstrates the fabrication of all MoS 2 based 2D/0D unipolar heterojunctions using a simple one pot hydrothermal process and their utilization in a flexible broadband photodetector covering the spectral range from the ultraviolet to the near infrared region. The discontinuous deposition of 0D MoS 2 , which has absorbance in the UV region, on 2D MoS 2 , having absorbance in the visible and near-infrared (NIR) regions, enables broadband detection. Further, contact engineering was performed wherein both the metal contacts were fabricated on 2D MoS 2 , thereby enabling the effective capture of photogenerated carriers. Also, a unipolar junction formed due to the Fermi level difference between 2D and 0D MoS 2 produces a localized electric field that helps in the efficacious separation of photogenerated electron-hole pairs. The responsivity values of the fabricated photodetector were calculated to be 7.56 mA W −1 , 12.8 mA W −1 , and 3.95 mA W −1 in the UV, visible and NIR regions, respectively, indicating that the fabricated device is more sensitive towards the visible region. A detailed understanding of the photodetection mechanism of this unique heterostructure is presented using bandgap theory and trap states. The successful demonstration of such a cost-effective, scalable 2D/0D based broadband photodetector should lead to potential applications in optoelectronics, security, and wearable electronics. In this work, we demonstrate, for the first time, a one-pot synthesized MoS2 based 2D/0D flexible broadband (UV-vis-NIR) photodetector.