Solution-Processed Uniform MoSe₂–WSe₂ Heterojunction Thin Film on Silicon Substrate for Superior and Tunable Photodetection

Abstract

2-D transition metal dichalcogenide (TMDC)-based heterostructures are promising active materials for high-performance optoelectronic devices. The low-cost, large-area, and high-quality fabrication of TMDC heterojunctions is essential for the efficient output of the device. Here, we demonstrate thin films of MoSe2–WSe2 nanocrystals deposited on a silicon substrate for enhanced photodetection. A MoSe2–WSe2 film, deposited by the electrophoretic deposition method, is initially transferred on the water surface and then prudently transferred on the p-Si (100) substrate. Scanning electron microscopy reveals the continuous and compact distribution of assembled nanocrystals with no pinhole. Energy-dispersive analysis of X-ray confirms the presence of MoSe2 and WSe2 in the transferred heterojunction film. The MoSe2–WSe2/p-Si fabricated heterojunction achieves a peak responsivity and external quantum efficiency of 336 mAW–1 and 80% (520 nm, 0.122 mW/cm2), respectively, which are ∼4 times higher in magnitude than those of pristine TMDC/Si fabricated heterojunctions. The enhanced photoresponse behavior is attributed to the superior absorbance in the visible region and type-II band alignment between MoSe2 and WSe2 nanocrystals, which facilitates improved generation and separation of charge carriers. Further, the photoresponse of MoSe2–WSe2/Si heterojunction is recorded in the temperature range of 45–300 K. The excellent heterojunction characteristic and photoresponse behavior of liquid exfoliated TMDC nanocrystals are the future gateways of highly efficient hybrid optoelectronic devices.