Study could Lead to a New Class of Materials for LEDs

Electroluminescence from vertically stacked GaN–Al2O3–MoS2–Al2O3-graphene heterostructures.

1st demo of electroluminescence from multilayer molybdenum disulfide, or MoS2, a discovery that could lead to a new class of materials for making LEDs. In its single-layer form, Mos2 is optically active, meaning that it emits light when electric current is run through it or when it is shot with a nondestructive laser. Multilayer molybdenum disulfide, by contrast, is easier and less expensive to produce, but it is not normally luminescent. In the new study, Duan and Dehui, created the 1st multilayer device that shows strong luminescence when electrical current is passed through it.

“It was rather surprising for us to discover that similar vertical devices made of multilayer MoS2 somehow showed very strong electroluminescence, which was completely unexpected since the multilayer MoS2 is generally believed to be optically inactive. So we followed this new lead to investigate the underlying mechanism and the potential of multilayer MoS2 in light-emitting devices.”

Duan and his team used a technique called electric field-induced enhancement, which relocates the electrons from a dark state to a luminescent state, thereby increasing the material’s ability to convert electrons into light particles, or photons. With this technique, the multilayer MoS2 semiconductors are at least as efficient as monolayer ones.
Duan’s team is currently moving forward to apply this approach to similar materials, including tungsten diselenide, molybdenum diselenide and tungsten disulphide, with the goal of helping to create a new generation of light-emitting devices from two-dimensional layered materials, which are less expensive and easier to use in manufacturing.
http://newsroom.ucla.edu/releases/ucla-study-could-lead-to-a-new-class-of-materials-for-making-leds