Temperature dependent electron-hole recombination in polymer light-emitting diodes

The current density–voltage characteristics of poly(dialkoxy $p$ -phenylene vinylene) based polymer are investigated as a function of temperature. Model calculations show that the differences between single and double carrier devices can be well understood by taking into account a bimolecular recombination process. It is found that the bimolecular recombination is thermally activated with an identical activation energy as measured for the charge carrier mobility. This demonstrates that the recombination process is of the Langevin type, and explains why the conversion efficiency (photon/carrier) of a polymer light-emitting diode is temperature independent.