Excitonics

Excitonics is a subfield of condensed-matter physics and device engineering that studies excitons—bound states of electrons and holes—and their use for information processing, energy transport and light–matter interactions. Excitons behave as charge-neutral quasiparticles with characteristic binding energy, size and lifetime determined by the host material and dimensionality. Two common types are Wannier–Mott excitons (large-radius, weakly bound, typical in inorganic semiconductors and quantum wells) and Frenkel excitons (tightly bound, common in organic crystals and molecular solids).

Research in excitonics covers exciton generation, transport, scattering, recombination and conversion to free charges or photons. It includes investigation of energy-transfer mechanisms such as Förster resonance energy transfer and Dexter exchange, and of coherent phenomena like exciton-polaritons that arise under strong coupling to optical cavities. Materials of interest range from bulk semiconductors and quantum wells to organic semiconductors, hybrid perovskites and atomically thin two-dimensional materials (e.g., transition-metal dichalcogenides), the latter notable for large exciton binding energies that enable room-temperature effects.

Experimental methods include photoluminescence, ultrafast pump–probe spectroscopy, transient absorption and near-field imaging. Theoretical approaches employ many-body techniques (GW and Bethe–Salpeter equation), time-dependent density functional theory and transport models. Potential applications span photovoltaics, light-emitting devices, excitonic transistors, low-threshold polariton lasers and components for optoelectronic and quantum technologies. Challenges for practical devices include short diffusion lengths, controlled exciton dissociation, nonradiative losses and integration with electronic architectures.