Trap-limited electron transport in disordered semiconducting polymers

Abstract

The electron transport in diodes of poly(dialkoxy-$p$-phenylene vinylene) (PPV) derivatives is strongly reduced as compared to the hole transport. A recent reexamination [M. M. Mandoc et al., Phys. Rev. B 73, 155205 (2006)] revealed that the room-temperature electron current shows the fingerprints of trap-limited transport with a distribution of traps in energy. Here, we report on the measured temperature dependence of the electron current in these PPV derivatives. This dependence is weak and seems to be in contradiction with existing trap-limited models. We demonstrate that the presence of a Gaussian density of states (DOS) for the mobile carriers, being characteristic for disordered semiconductors, reduces the temperature dependence of the trap-limited charge transport. The reduction is governed by the width of the Gaussian DOS and originates from the equilibrium concentrations of the mobile and trapped carriers.