about

Solar cells and light emitting diodes are vital to our energy future. Solar cells are needed to generate renewable energy, and light emitting diodes are needed to reduce the energy used for lighting. But solar cells and light emitting diodes are still too expensive, limiting their benefit to society. Fundamentally, the expense of solar cells and light emitting diodes is due to the use of highly-ordered semiconductor materials. We must learn instead to exploit disordered materials. In turn, this means we must master the exciton—a localized excited state characteristic of disordered and low-dimensional materials.

We propose a comprehensive Center for Excitonics comprising investigators at MIT, Harvard and the Center for Functional Nanomaterials at Brookhaven National Laboratory. We will address the science and applications of these crucial intermediates for energy transduction in low cost, disordered semiconductors.

Compared to the electron-hole pair states in conventional inorganic semiconductors, the dynamics and behavior of excitons are poorly understood. We will answer the following questions: How are excitons created and destroyed? How can we control the migration of excitons? How do they move through interfaces and around defects? How can we control the transition between coherence and incoherence, or localization and delocalization? And finally, how can we build excitonic devices that address society's needs for a new generation of energy technologies?

We expect the following major scientific outcomes from the center:

1. We will understand and exploit exciton transport in complex nanostructures, incorporating environmental effects and coherence;
2. We will understand and exploit novel excitonic states of matter, including hybrid organic-inorganic excitons, strongly coupled exciton-polaritons and exciton plasmon polaritons;
3. We will perform spectroscopy of individual excitons using superconducting nanowire single-photon detectors, observing exciton formation, dissociation, fission and annihilation.

We expect the following major technological outcomes from the center:

1. Efficient synthetic and room-temperature-reconfigurable light absorbing antennas with sub-5-nm feature sizes for solar cells;
2. Stable organic light emitting devices exploiting spin orbit coupling to achieve internal fluorescent efficiencies approaching 100%, and novel nanowire, nanowire heterostructure and nanowire-quantum dot aggregate materials for solid state lighting;
3. Thin film, non-tracking solar concentrators with power efficiencies exceeding 30%.