Energy Transfer By Excited States

The absorption of a photon or an electron-hole recombination event in an organic solid creates an electronic excitation, 

In conventional solid-state physics, an exciton is considered as an electron-hole pair separated by a medium with a well-defined dielectric constant, s. The time-independent Schrodinger equation with the inter-carrier Coulomb 

This type of exciton is envisaged by Wannier [125] and Mott [132a], thus known commonly as a Wannier-Mott exciton. In this exciton, the electron and the hole revolve around each other resembling the simple (Bohr) structure of the hydrogen atom. The energies (45) and inter-carrier distances 

The exciton binding energy is related directly to the ionization energy of the hydrogen atom, ZH = 13.5 eV, according to 

In the random walk description, the energy transfer rate constant is related to the number of hops made by the exciton without revisiting any site in its lifetime. The nearest-neighbor random walk in an isotropic medium may be approximated by a random walk on a simple cubic lattice [145] 

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