Cottrell Scholar Awards - 2014
Valley Quantum Optoelectronics of Monolayer Semiconductors
The interaction of photons and electrons – a field of scientific research called quantum optoelectronics -- is at the center of innovation in developing new technologies for renewable energy, imaging and communications.
Xu is investigating a new class of quantum optoelectronic material known as “atomically thin transition metal dichalcogenides” (TMDs). These materials exhibit tremendous potential to become the next generation of transistors in electronic devices. TMDs include compounds such as molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2) and monolayer tungsten diselenide (WSe2).
TMDs are incredibly thin crystalline molecules – just three atoms thick -- with the atoms arranged in a honeycomb lattice like another miracle material, graphene. But unlike graphene, TMDs are good at absorbing visible light (photons); once TMD electrons are excited by absorbing photons, they exhibit what physicists call a strong “spin-orbit coupling.” This can boost the electron’s energy levels – important in photovoltaic devices that produce electricity directly from sunlight – due to electromagnetic interaction between the electron’s spin and the magnetic field generated by the electron’s orbit around the atomic nucleus.
In other words, among other things TMDs may allow us to create thin films that produce relatively large amounts of electricity when exposed to sunlight.