Magnetic field effects on photoluminescence in PPP. Investigation of the influence of chain length and degree of order

The effect of weak static magnetic fields on the photoluminescence quantum yield in poly(para-phenylene) films, which differ in chain length and degree of crystallinity, were investigated in the temperature range between 100 and 300 K. Applying a magnetic field enhances the photoluminescence quantum yield, the relative photoluminescence increase being about a factor 10−4. On the basis of the magnetic field sensitivity, it is proposed that the emission of photoluminescence is partially due to geminate recombination of charge carriers. The formation of intermediate charge transfer states after photoexcitation is responsible for the appearance of the magnetic field effect. Properties of these states are investigated in terms of magnetic field effects, and the influence of the structure of the polymer films is discussed.