Strain-modulation-assisted enhanced broadband photodetector based on large-area, flexible, few-layered Gr/MoS₂ on...

Electronic structure and carrier behavior in semiconductor junctions can be effectively modulated on the application of strain. This work represents the first demonstration of a large-area, flexible, paper-based graphene-molybdenum disulfide (Gr/MoS₂) broadband photodetector using a low-cost solution-processed hydrothermal method and enhancement in photodetection through strain modulation by assembling the device on polydimethylsiloxane. Optimization, in terms of process parameters, was carried out to obtain trilayer MoS₂ over Gr-cellulose paper. Under strain, potential barrier variation and piezopotential induced in MoS₂ leads to 79.41% enhancement in photodetection in the visible region. Piezopotential induced in MoS₂ lowers the conduction-band energy thereby increasing the effective electric field favoring easy electron-hole separation. The advantage of vertically stacked Gr/MoS₂ for the photodetector is the utilization of the entire area as a junction where effective separation of electron-hole pairs occurs. Detailed studies of the mechanism in terms of potential barrier variation in Gr/MoS₂ and an energy-band diagram are presented to help understand the proposed phenomenon. The present work demonstrates the significance of few-layer MoS₂ or Gr in relation to strain-modulated photosensing in comparison to their counterparts grown via chemical vapor deposition. The results provide an excellent approach for the fabrication of low-cost heterojunctions for improved optoelectronic performance, which can be further extended to similar 2D-material heterojunctions for analog, digital and optoelectronic applications.