MoSe2/single-walled carbon nanotube n-p heterojunction for broadband photodetection and ambient stability improvement with surface engineering

Abstract

Transition metal dichalcogenides (TMDCs) have a tremendous capability of visible/infrared light absorption and conversion to electrical signals. On the other hand, single-walled carbon nanotubes (SWCNTs) are popularly used as efficient carrier transporting layers rather than light absorption and carrier generation. In the current study, we are reporting an excellent heterojunction of MoSe2 (TMDC) and SWCNT for a wide range (532–1064 nm) photodetection. Hydrothermally grown 2D sheets (∼34 nm) assembled nanoflower-like spongy structure of MoSe2 was interlinked by semiconducting SWCNTs and utilized for broadband detection. The p-n heterojunction between SWCNT and MoSe2 facilitates the excess hole transfer from MoSe2 to SWCNT under illumination that is eventually responsible for high-performance photoresponse with a responsivity of 152.6 mA/W and detectivity of 1.66 × 1010 Jones in 1064 nm light. Unfortunately, the photoresponse of MoSe2/SWCNT heterojunction was deteriorated nearly after four weeks due to the strong reactivity of MoSe2 chalcogenide towards ambient oxygen. The Raman and UV–visible-NIR absorbance spectra ensured substantial transformation of MoSe2 to MoOx in the air. To achieve essential ambient stability, the MoSe2/SWCNT surface was encapsulated with a thin transparent layer of polymethyl methacrylate. The surface-engineered photodetector exhibited extremely stable photoresponse after eight weeks, but the photoresponsivity was declined almost ten times.