We investigate the rate constant for Langevin-type bimolecular recombination using a Monte Carlo model. It is found that filamentary transport, mobility anisotropy, restriction of transport in one dimension, and confinement of electrons and holes to one transporting component within a blend can cause significant deviations from classical Langevin behavior. We discuss in detail the reasons for the failure of the Langevin model for these instances, provide alternative formula, and comment upon the implications for polymer transistors, LEDs, and photovoltaics.

• Received 15 July 2008

DOI:https://doi.org/10.1103/PhysRevB.78.155205