Trap-Assisted Recombination in Disordered Organic Semiconductors

Abstract

The trap-assisted recombination of electrons and holes in organic semiconductors is investigated. The extracted capture coefficients of the trap-assisted recombination process are thermally activated with an identical activation energy as measured for the hole mobility ${\mu }_p$. We demonstrate that the rate limiting step for this mechanism is the diffusion of free holes towards trapped electrons in their mutual Coulomb field, with the capture coefficient given by $(q/\epsilon ){\mu }_p$. As a result, both the bimolecular and trap-assisted recombination processes in organic semiconductors are governed by the charge carrier mobilities, allowing predictive modeling of organic light-emitting diodes. DOI: http://dx.doi.org/10.1103/PhysRevLett.107.256805 © 2011 American Physical Society