Multilayer WSe 2 /MoS 2 Heterojunction Phototransistors through Periodically Arrayed Nanopore Structures for Bandgap Engineering.

While 2D transition metal dichalcogenides (TMDs) are promising building blocks for various optoelectronic applications, limitations remain for multilayered TMD-based photodetectors: an indirect bandgap and a short carrier lifetime by strongly bound excitons. Accordingly, multilayered TMDs with a direct bandgap and an enhanced carrier lifetime are required for the development of various optoelectronic devices. Here, periodically arrayed nanopore structures (PANS) are proposed for improving the efficiency of multilayered p-WSe 2 /n-MoS 2 phototransistors. Density functional theory calculations as well as photoluminescence and time-resolved photoluminescence measurements are performed to characterize the photodetector figures of merit of multilayered p-WSe 2 /n-MoS 2 heterostructures with PANS. The characteristics of the heterojunction devices with PANS reveal an enhanced responsivity and detectivity measured under 405 nm laser excitation, which at 1.7 × 10 4 A W -1 and 1.7 × 10 13 Jones are almost two orders of magnitude higher than those of pristine devices, 3.6 × 10 2 A W -1 and 3.6 × 10 11 Jones, respectively. Such enhanced optical properties of WSe 2 /MoS 2 heterojunctions with PANS represent a significant step toward next-generation optoelectronic applications.