N-doped MoS2 via assembly transfer on an elastomeric substrate for high-photoresponsivity, air-stable and stretchable photodetector

As a direct-bandgap semiconductor, single-layer MoS2 has gained great attention in optoelectronics, especially wearable photodetectors. However, MoS2 exhibits poor photoresponsivity on a stretchable substrate due to intrinsic low carrier density and a large number of scattering centers on polymer substrates. Few air-stable yet strong dopants on MoS2 has been reported. In addition, the roughness, hydrophobicity and susceptibility to organic solvents of polymer surface are critical roadblocks in the development of stretchable high-performance MoS2 photodetectors. Here, we realize a stretchable and stable photodetector with high photoresponsivity by combining n-type dopant ((4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl) phenyl) dimethylamine, N-DMBI) with MoS2 and assembly transfer technique. It is found electron tends to transfer from N-DMBI to MoS2 and the effect is maintained after the integrable photodetector transferred directly by elastic substrate styrene-ethylene-butylene-styrene (SEBS), even after being exposed to the air for 20 days, which benifits greatly from the encapsulation of SEBS. The increased carrier density greatly promotes carrier injection efficiency and photogenerated electron-hole separation efficiency at the metal-semiconductor interface, thus offering a significantly improved photoresponsivity in MoS2 photodetectors. Moreover, such photodetector shows great durability to stretch, which can remain functional after stretched 100 cycles within its stretch limit. Our strategy opens a new avenue to fabricate high-photoresponsivity stretchable electronics or optoelectronics of two-dimensional (2D) materials.