Researchers disentangle two competing mechanisms that govern how a promising semiconductor material responds to light

Red and blue light splitting (Courtesy: Shutterstock/Iscatel)

When light is absorbed by a semiconductor, it first creates an electron-hole pair before free charges can be generated. The electron and hole can remain bound together in a quasiparticle known as an exciton. This intermediate stage is important because excitons determine how light is absorbed and emitted, and how efficiently a material can convert light into electrical current.

Monolayer tungsten diselenide (WSe₂) is a material that researchers are investigating for use in photodetectors, optical computing and quantum technologies. It is an atom-thick semiconductor that interacts very strongly with light. The excitons formed in WSe₂ are unusually stable, allowing quantum effects to be observed particularly strongly.…