Temperature dependence of current-voltage characteristics of poly(p-pyridine) light-emitting diodes

We investigate the dependence of the current-voltage characteristics of single layer light-emitting diodes fabricated with the electron transporting polymer poly(p-pyridine) (PPY). The characteristics are found to vary with temperature and are compared with results obtained for MEH-PPV devices. It is found that the barrier to injection deduced from UPS measurements is not the current limiting factor in these devices but that space charge effects resulting from n-type doping of the material give rise to the characteristics observed.