Temperature dependence of the photo- and electroluminescence of poly(p-phenylene vinylene) based polymers

We show that the exciton transport and decay processes in two poly(p-phenylene vinylene) (PPV) based semiconducting polymers exhibit distinct temperature dependence based on the energetic disorder of the polymer. Time-resolved photoluminescence (TRPL) spectroscopy and Monte Carlo exciton diffusion simulations are used to disentangle the contributions from radiative and non-radiative decay processes, with the latter including non-radiative decay due to exciton diffusion toward trap sites. In a highly disordered polymer, the exciton lifetime and quantum yield are nearly temperature independent. In the case of a less disordered polymer, the exciton lifetime and quantum yield increase with decreasing temperature, due to both freezing out vibrations and less exciton quenching by slowing down the diffusion toward trap sites. We further demonstrate that the temperature dependence of the electroluminescence of polymer light-emitting diodes comprising these polymers is directly correlated with the photoluminescence behavior.