Photoluminescence excitation spectra of pristine and photo-oxidised poly(p-phenylenevinylene)

We present photoluminescence excitation (PLE) spectra for pristine and photo-oxidised samples of poly(p-phenylenevinylene) (PPV). In pristine PPV we observe a constant photoluminescnce efficiency for excitation wavelengths in the range 500-250 nm. In contrast, in photo-oxidised PPV samples the PLE spectrum is very sensitive to the degree of oxidation. In particular the PL efficiency decreases at short excitation wavelengths in an oxidised sample.