The Energy Frontier Research Center (EFRC) for Excitonics is a collaboration between MIT, Harvard and Brookhaven National Laboratory. The Center for Excitonics is based in the Research Laboratory of Electronics (RLE) at MIT and funded by the US Department of Energy with $19M spread over five years.

The Excitonics Center’s objective is to supersede traditional electronics with devices that use excitons to mediate the flow of energy. Motivated by photosynthesis, nature’s two-billion-year-optimized energy system that uniquely controls excitons, the work of the Center is to understand and exploit the energy conversion processes between photons and electrons.

Excitons are quasi-particle excitations consisting of a bound electron and hole that mediate the absorption and emission of light, especially in disordered and low-dimensional materials. The work of the Center’s researchers will tackle how excitons are created and destroyed, how migration of excitons can be controlled, how excitons move through interfaces, and ultimately with this understanding will make it possible to build excitonic devices to meet society’s needs for a new generation of energy technologies.

EECS professor Marc Baldo, director of the Center for Excitonics, and a large multidisciplinary research group including four EECS faculty members and seven EECS graduate students, are exploring materials with only short-range order. These nanostructured materials are composed of nano-engineered elements such as organic molecules, polymers, or quantum dots and wires, in films bound together by weak van der Waals bonds. These materials are characterized by the excitons that are localized within the ordered nanostructures.

Due to localization of excitons, the optical properties of the films are relatively immune to longer-range structural defects and disorder. In contrast with the painstaking growth requirements of conventional semiconductors, weak van der Waals bonds allow excitonic materials to be readily deposited on a variety of materials at room temperature. Researchers at the EFRC address two grand challenges in excitonics: (1) to understand, control and exploit exciton transport, and (2) to understand and exploit the energy conversion processes between excitons and electrons, and excitons and photons.

Conventional electronic devices can be difficult to manufacture; their constituent materials require very high levels of order and achieving such low entropy in a semiconductor requires expensive and energy intensive fabrication. For example, the energy payback time for a crystalline silicon solar cell is on the order of 2 years, and at current manufacturing growth rates, it is expected to take at least 20 years to produce enough silicon-based solar cells to make a significant impact on the global energy supply.

Potential outcomes from the Center’s activities include the development of efficient synthetic and room-temperature reconfigurable light absorbing antennas with sub 5-nm feature sizes for solar cells; stable organic light emitting devices exploiting spin orbit coupling to reach 100% efficiencies in internal fluorescence, and novel nanowire, nanowire heterostructure and nanowire-quantum dot aggregate materials for solid state lighting; and thin film, non-tracking solar concentrators with power efficiencies over 30%. Take a few minutes to see the video about Marc Baldo and the Center’s research. (video credit to Gren Hren/RLE-MIT).