AC-driven multicolor electroluminescence from a hybrid WSe₂ monolayer/AlGaInP quantum well light-emitting device

Light-emitting diodes (LEDs) are used widely, but when operated at a low-voltage direct current (DC), they consume unnecessary power because a converter must be used to convert it to an alternating current (AC). DC flow across devices also causes charge accumulation at a high current density, leading to lowered LED reliability. In contrast, gallium-nitride-based LEDs can be operated without an AC-DC converter being required, potentially leading to greater energy efficiency and reliability. In this study, we developed a multicolor AC-driven light-emitting device by integrating a WSe₂ monolayer and AlGaInP-GaInP multiple quantum well (MQW) structures. The CVD-grown WSe₂ monolayer was placed on the top of an AlGaInP-based light-emitting diode (LED) wafer to create a two-dimensional/three-dimensional heterostructure. The interfaces of these hybrid devices are characterized and verified through transmission electron microscopy and energy-dispersive X-ray spectroscopy techniques. More than 20% energy conversion from the AlGaInP MQWs to the WSe₂ monolayer was observed to boost the WSe₂ monolayer emissions. The voltage dependence of the electroluminescence intensity was characterized. Electroluminescence intensity-voltage characteristic curves indicated that thermionic emission was the mechanism underlying carrier injection across the potential barrier at the Ag-WSe₂ monolayer interface at low voltage, whereas Fowler-Nordheim emission was the mechanism at voltages higher than approximately 8.0 V. These multi-color hybrid light-emitting devices both expand the wavelength range of 2-D TMDC-based light emitters and support their implementation in applications such as chip-scale optoelectronic integrated systems, broad-band LEDs, and quantum display systems.