A paper in ACS Nano by the U.S. Naval Research Lab confirms the identification of new semiconductor nanocrystals with exciting ground-state excitons, a major achievement in optoelectronics.

The development of additional technologies, such as extremely efficient light-emitting devices, could be revolutionized by the innovative theoretical study.

The term "dark" exciton refers to the lowest-energy exciton that is typically poorly emitting in nanocrystals. The dark exciton restricts the functionality of devices based on advanced nanocrystals, such as lasers and light-emitting diodes (LEDs), by slowing down light emission. The dark exciton is a problem that scientists have long tried to solve.

The goal, according to John Lyons, Ph.D., of the Theory of Advanced Functional Materials Section, was to discover new materials with an inverted exciton ordering, meaning that the lowest-energy exciton would be light. He continued by saying that they found more than 150 targets by sifting through open-source material databases using criteria derived from their theoretical modeling. Using sophisticated first-principles calculations, they further reduced this list until they had 28 potential bright-exciton nanomaterial possibilities.

At least four of these materials can produce brilliant ground-state excitons in advanced nanocrystals, according to more thorough modeling of these materials. According to Lyons, this discovery, which was made in cooperation with Peter Sercel, Ph.D., of the Center for Hybrid Organic-Inorganic Semiconductors for Energy (CHOISE) and Prof. David Norris from the Federal Institute of Technology (ETH) Zurich, could open the door for the creation of lasers, ultrabright and highly efficient light-emitting devices, and other technologies.

Scientists at NRL hope that by solving the dark-exciton puzzle, they will encourage the large nanomaterial community to tackle the too-long-stalled problem of bright-exciton nanostructures through these nanocrystal research findings. Three of these materials are currently being developed at NRL as part of the Bright Nanocrystal Emitters effort of the Nanoscience Institute Program, which aims to use bright-exciton behavior for future naval technologies and provide a definitive demonstration of it in the lab.