Features of photoluminescence of oxygen-saturated films of methoxypolyphenylene vinylene (MEH-PPV)

The effects of the influence of the magnetic field on the luminescence intensity of methoxypolyphenylene vinylene (MEH-PPV) films at various air pressures above the samples are investigated. An inversion of the sign of the magnetic field effect was detected with a smooth change in the oxygen concentration in the system. Based on the balance equations, a theoretical model of processes is proposed that takes into account the formation of populations of triplet $(T)$ excitons of MEH-PPV and singlet oxygen during the reactions of triplet-triplet annihilation, $T-{}^3\Sigma_g$(O$_2$)-quenching and $T-{}^1\Delta_g$(O$_2$)-cross-annihilation of electronic excitations. According to the proposed theoretical model, the magnetic field effects of delayed fluorescence at different concentrations of O$_2$ molecules in MEH-PPV films are calculated, consistent with the experimental results.