THE ROLE OF CARBONYL GROUPS IN THE PHOTOLUMINESCENCE OF POLY(P-PHENYLENEVINYLENE)

This paper reports that carbonyl moieties are present as defects, formed during the thermal conversion of a precursor to poly(p-phenylenevinylene) (PPV), a polymer used in light-emitting diodes. The increase in carbonyl groups can be correlated with a dramatic reduction of PPV photoluminescence. We have discovered that if the conversion is carried out in a reducing atmosphere, e.g., 15% hydrogen in nitrogen, the amount of carbonyls is substantially reduced and the photoluminescence intensity of the polymer increases as much as 5-fold. These results also have important implications for theories, advanced by other authors, of the effect of conjugation length or chain alignment on photoluminescence and electroluminescence in these systems.