Geminate-pair dissociation yield in systems with exponential energetic disorder — A Monte Carlo study

Abstract Geminate electron–hole recombination in systems with exponential energetic disorder is studied by Monte Carlo method. The field and temperature dependencies of geminate-pair dissociation probability are calculated. It is established that the dissociation yield of carrier pairs depends mainly on the extent of carrier thermalization, which influences the Einstein relationship. The approximate limiting temperature is given by T e = e 0 /2 k B , where e 0 determines the decay rate of exponential distribution of localized states. For systems in approximate thermal equilibrium, at T > T e , the yield of free carriers is almost independent of disorder degree and its temperature dependence at zero field has an Arrhenius form. These simulation results are well described by classical Onsager theory. For non-equilibrium systems, at T T e , the free-carrier yield significantly increases with growing disorder and temperature dependence of zero-field carrier yield is sub-Arrhenius one. At sufficiently low temperatures the carrier yield approaches constant value. These results are described with good accuracy by modified Onsager theory, with T replaced by T e . It is concluded that experimental investigations of geminate-carrier dissociation yield in disordered materials may be a valuable tool for verifying the Einstein relation and determining the energy distribution of localized states.