Transient uv electroluminescence from poly(p-phenylenevinylene) conjugated polymer induced by strong voltage pulses

We present time-resolved and spectral measurements of electroluminescence from poly((Formula presented) phenylenevinylene) (PPV) thin films upon application of high-voltage pulses. Above some threshold voltage of 100 V, we observe an uv-violet emission centered at 390 nm, in addition to the characteristic yellow-green luminescence of PPV. We explain this emission as being induced by a generation of hot carriers in the strong electric field, which inhibits the formation of singlet excitons and enhances the probability for direct interband transitions of the relaxed carriers.