: When light is absorbed, it creates a bound electron-hole pair called an . Because of high binding energies (
) screens the Coulombic attraction between them. In organic semiconductors, the weak dielectric screening means that absorbing a photon creates a strongly bound, localized electron-hole pair known as a . Frenkel excitons feature high binding energies ( physics of organic semiconductors pdf
Because the dielectric constant is low, organic semiconductors form . These excitons are tightly bound to a single molecule or a few monomer units, with a high binding energy of 0.1 eV to 1.0 eV. Splitting a Frenkel exciton into free charge carriers requires a strong internal electric field or an energy offset at a material interface. : When light is absorbed, it creates a