Researchers have developed electrically tunable excitonic light-emitting diodes (LEDs) based on monolayer WSe₂ p-n junctions. The study demonstrates that by using a thin boron nitride layer as a dielectric and multiple metal gates, efficient and tunable electroluminescence can be achieved. The structure allows effective injection of electrons and holes, and combined with the high optical quality of WSe₂, it yields bright electroluminescence with significantly smaller injection current and linewidth compared to MoS₂. The system enables tuning of electroluminescence between regimes of impurity-bound, charged, and neutral excitons, making it suitable for new optoelectronic devices such as spin- and valley-polarized LEDs, on-chip lasers, and two-dimensional electro-optic modulators. Monolayer transition metal dichalcogenides (TMDs) are promising for optoelectronic applications due to their strong electron-hole interactions and unique optical properties. In this study, monolayer WSe₂ is used with a p-n junction architecture to create efficient and electrically tunable LEDs. The device consists of a monolayer WSe₂ sheet on a hexagonal boron nitride (BN) layer, with two palladium gate electrodes and gold/vanadium source and drain contacts. The BN layer serves as a smooth, disorder-free substrate and a high-quality gate dielectric. The p-n junction is created electrostatically by applying voltages to the gate electrodes, resulting in two separate doped regions separated by an undoped strip. The device shows bright electroluminescence when configured as a p-n junction, with a current as low as 200 pA. The electroluminescence spectrum is tunable by adjusting the injection bias, allowing for control over the excitonic states. The EL spectrum shows three main features: a narrow higher-energy peak, a broad central peak, and a lower-energy peak, corresponding to different excitonic species. The study also demonstrates that the EL is from valley excitons in monolayer WSe₂, which are formed in the ±K valleys. The EL is unpolarized, as both valleys are equally populated. The results suggest that using ferromagnetic contacts could enable spin- and valley-polarized LEDs. The device efficiency could be improved by reducing contact resistance, improving WSe₂ crystal quality, and using better membrane transfer techniques. The findings highlight the potential of monolayer TMDs for next-generation optoelectronic devices.Researchers have developed electrically tunable excitonic light-emitting diodes (LEDs) based on monolayer WSe₂ p-n junctions. The study demonstrates that by using a thin boron nitride layer as a dielectric and multiple metal gates, efficient and tunable electroluminescence can be achieved. The structure allows effective injection of electrons and holes, and combined with the high optical quality of WSe₂, it yields bright electroluminescence with significantly smaller injection current and linewidth compared to MoS₂. The system enables tuning of electroluminescence between regimes of impurity-bound, charged, and neutral excitons, making it suitable for new optoelectronic devices such as spin- and valley-polarized LEDs, on-chip lasers, and two-dimensional electro-optic modulators. Monolayer transition metal dichalcogenides (TMDs) are promising for optoelectronic applications due to their strong electron-hole interactions and unique optical properties. In this study, monolayer WSe₂ is used with a p-n junction architecture to create efficient and electrically tunable LEDs. The device consists of a monolayer WSe₂ sheet on a hexagonal boron nitride (BN) layer, with two palladium gate electrodes and gold/vanadium source and drain contacts. The BN layer serves as a smooth, disorder-free substrate and a high-quality gate dielectric. The p-n junction is created electrostatically by applying voltages to the gate electrodes, resulting in two separate doped regions separated by an undoped strip. The device shows bright electroluminescence when configured as a p-n junction, with a current as low as 200 pA. The electroluminescence spectrum is tunable by adjusting the injection bias, allowing for control over the excitonic states. The EL spectrum shows three main features: a narrow higher-energy peak, a broad central peak, and a lower-energy peak, corresponding to different excitonic species. The study also demonstrates that the EL is from valley excitons in monolayer WSe₂, which are formed in the ±K valleys. The EL is unpolarized, as both valleys are equally populated. The results suggest that using ferromagnetic contacts could enable spin- and valley-polarized LEDs. The device efficiency could be improved by reducing contact resistance, improving WSe₂ crystal quality, and using better membrane transfer techniques. The findings highlight the potential of monolayer TMDs for next-generation optoelectronic devices.