Stepwise Engineering of Van der Waals Heterostructures for High Current Density in Light Emitting Devices

Abstract

Van der Waals (vdW) heterostructures of transition metal dichalcogenides (TMDs) have been widely employed in optoelectronic applications, including photodetectors, photovoltaic cells, and light-emitting devices (LEDs). Among these, PN-junction-based heterostructures are critical for advanced LED and laser applications, where achieving high current density is essential. However, the development of PN-junction-type LEDs using vdW heterostructures has been significantly hindered by the lack of effective doping techniques, resulting in devices with limited current densities. In this study, we propose a novel strategy for high-density carrier doping and reduced device resistance in vdW heterostructures by combining stepwise engineering of vdW stacking with electric double-layer (EDL) carrier doping. The stepwise-engineered heterostructure, based on WS₂/WSe₂, takes advantage of this configuration to facilitate efficient charge transport and enhanced carrier injection, as both P-type and N-type materials are in direct contact with the electrolyte, enabling high-density doping in both materials. Through EDL doping, clear electroluminescence was observed at the interface, with a peak current density of 9.4 × 10⁴ A/cm². This result marks a significant advancement over previous reports, demonstrating a promising pathway toward vdW heterostructure-based laser applications.