Double Heterostructures for Monolayer Materials with Record Quantum Efficiency

2D semiconductor materials have shown great potential and advantages for a wide variety of optoelectronic devices, especially compact and integrated light-emitting diodes (LEDs) and lasers. However, the lack of a type-I double-heterostructure has severely hindered the development of efficient LEDs and lasers based on 2D materials. In this article, a lateral double-heterostructure is proposed based on a single type-I heterostructure composed of multilayer WSe2 and monolayer MoTe2 with double back-gates. This design synergizes the high mobility of the multilayer and the direct bandgap of the monolayer: carrier injection and transport are facilitated in the WSe2 barrier layer, while they are transferred and confined in the MoTe2 well layer for efficient radiative recombination through type-I band alignment. Therefore, the double-heterostructure reaches an external quantum efficiency of 1% level, a new record for p-n junctions based on transition metal dichalcogenides. Additionally, the heterostructure device achieves a 40-fold enhancement of the maximum electroluminescent intensity and a 24-fold enhancement of power efficiency compared with the single monolayer MoTe2 counterpart at room temperature. This promising strategy can also be extended to other 2D-semiconductor LEDs and could bring 2D-materials devices into practical applications of micro-LED displays, electrically injected 2D-materials lasers, and silicon-based on-chip light sources.