A High-Efficiency Wavelength-Tunable Monolayer LED with Hybrid Continuous-Pulsed Injection.

Yi Zhu,Juan F Torres,Yilin Tang,Jian Zhang,Lan Fu,Yuerui Lu,Ziyuan Li,Wojciech LipińSki,Bowen Wang

doi:10.1002/adma.202101375

Yi Zhu, Juan F Torres + Show 7 more

Open Access

https://doi.org/10.1002/adma.202101375

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Abstract

High-efficiency and wavelength-tunable light-emitting diode (LED) devices will play an important role in future advanced optoelectronic systems. Traditional semiconductor LED devices typically have a fixed emission wavelength that is determined by the energy of the emission states. Here, a novel high-efficiency and wavelength-tunable monolayer WS2 LED device, which operates in the hybrid mode of continuous-pulsed injection, is developed. This hybrid injection enables highly enhanced emission efficiency (>20 times) and effective size of emission area (>5 times) at room temperature. The emission wavelength of the WS2 monolayer LED device can be tuned over more than 40nm by driving AC voltages, from exciton emission to trion emission, and further to defect emission. The quantum efficiency of defect electroluminescence (EL) emission is measured to be more than 24.5 times larger than that from free exciton and trion EL emission. The separate carrier injection in the LED also demonstrates advantages in allowing defect species to be visualized and distinguished in real space. Those defects are assigned to be negatively charged defects. The results open a new route to develop high-performance and wavelength-tunable LED devices for future advanced optoelectronic applications.

Highlights

Layered transition metal dichalcogenide (TMD) monolayers have attracted considerable interest for their unique electronic and optical properties.[1,2,3,4,5,6] These monolayers exhibit direct bandgap nature with high quantum yield of light emission and are of particular interest for novel optoelectronic device applications, such as a light emitting diode (LED).[7, 8] Monolayer LED was demonstrated by forming a horizontal p-n junction using electrostatic gates.[8]
These two types of LED devices are based on direct current (DC) injection configuration and require complicated device structures
We developed a novel hybrid continuous-pulsed injection method in an alternating current (AC)-driving LED device, which enables electron-hole recombination to occur in areas far away from the metal-semiconductor contract edge

Summary

Introduction

Layered transition metal dichalcogenide (TMD) monolayers have attracted considerable interest for their unique electronic and optical properties.[1,2,3,4,5,6] These monolayers exhibit direct bandgap nature with high quantum yield of light emission and are of particular interest for novel optoelectronic device applications, such as a light emitting diode (LED).[7, 8] Monolayer LED was demonstrated by forming a horizontal p-n junction using electrostatic gates.[8]. We developed a novel hybrid continuous-pulsed injection method in an AC-driving LED device, which enables electron-hole recombination to occur in areas far away from the metal-semiconductor contract edge.

Results

Conclusion