 Such a value of the high frequency dielectric constant should then conform the relation formula_28, where formula_29 is the refractive index of the material.Although many progresses have been made on the topic since the classical work of Frenkel,
the Poole-Frenkel formula has been spreadly used to interpret several non-ohmic experimental currents observed in dielectrics and also semiconductors.The debate about the underlying assumptions of the classical Poole-Frenkel model has given life to several improved Poole-Frenkel models.