Picosecond time-resolved photoluminescence of PPV derivatives

We report some time-resolved luminescence measurements on the conjugated polymer, MEH-PPV, that show a marked dependence on the intensity of the excitation light. At low laser powers the excited state lifetime is longer than has been reported previously and is consistent with emission from an interchain excitation that has low oscillator strength and hence a long natural radiative lifetime. We rationalise these data with a simple scheme that summarises the excited state kinetics in this and other conjugated, electroluminescent polymers.