Excitonrelated

Exciton-related refers to phenomena and properties tied to excitons, which are bound states of an electron and a hole bound by Coulomb attraction in insulators and semiconductors. Excitons form when a material absorbs energy that promotes an electron across the band gap, leaving a hole behind; the electron and hole remain bound as an excited state below the conduction band edge. They may also form via charge-transfer at donor–acceptor interfaces.

Two broad classes are recognized. Frenkel excitons are localized on a molecule or lattice site, typical in organic crystals with high binding energy. Wannier-Mott (or Wannier) excitons are delocalized over many lattice constants, typical in inorganic semiconductors with smaller binding energy. In two-dimensional materials, including monolayer transition metal dichalcogenides, excitons exhibit large binding energies and strong optical transitions.

Exciton dynamics include diffusion, recombination, and dissociation into free carriers; lifetimes range from picoseconds to nanoseconds depending on material and environment. Properties such as binding energy, radius, and diffusion length influence optical absorption and emission. Their behavior affects both fundamental light-matter interactions and device performance in optoelectronic systems.

Exciton-related phenomena include exciton-polaritons in optical microcavities, where strong light-matter coupling yields hybrid quasiparticles; energy transfer mechanisms such as Förster resonance energy transfer and Dexter transfer; and exciton condensation under certain conditions. These effects underpin devices like organic and inorganic light-emitting diodes, solar cells, and photodetectors, as well as proposed excitonic lasers and quantum information platforms.

Measurement and study rely on spectroscopy, including photoluminescence, absorption, and time-resolved or transient techniques, to extract exciton binding energy, lifetimes, diffusion lengths, and transport properties.