Transient photoluminescence measurements in poly(p-phenylene vinylene)
illustrate that exciton diffusion to quenching centers explains the n
onexponential decay dynamics. The structure of these defects is studie
d by vibrational spectroscopy and the reason they act as quenchers is
explained. In their absence, we observe nearly exponential photolumine
scence decay with lifetime >1 ns. The new picture of photoexcitations
which emerges and its implications for polymer electroluminescent devi
ces are discussed.