Photoluminescence quantum efficiency (PLQE) and PL decay characteristics of polymeric light emitting materials

We report photoluminescence quantum efficiency (PLQE) measurements on thin films of a variety of in-house synthesized conjugated polymers such as PPV, MEH-PPV and CN-PPV with improved techniques using integrating sphere and synchronous detection. Our method allows use of low level of excitation avoiding problems due to degradation during measurement. Time correlated single photon counting (TCSPC) has been used to study PL decay to obtain radiative lifetime controlling efficiency in these materials. The measured PL efficiency in PPV synthesized by xanthate precursor route is measured to be 0.07 ± 0.01, which is lower than reported for similar films owing to presence of intrinsic defects. The measured PL quantum efficiency of CN-PPV and MEH-PPV are 0.24 ± 0.07 and 0.17 ± 0.01, respectively. These values are comparable to the ones reported by others [N.C. Greenham, I.D. Samuel, G.R. Hayes, R.T. Phillips, Y.A.R.R. Kessener, S.C. Moratti, A.B. Holmes, R.H. Friend, Chem. Phys. Lett. 89 (1995) 241]. We suggest a reliable method of obtaining the radiative lifetime from PL decay curves using time domain spectroscopic technique.