Comparison of ultraviolet- and charge-induced degradation phenomena in blue fluorescent organic light emitting diodes
We compare the degradation of organic light emitting diodes (OLEDs) by UV light and by electrical driving. We prove that the exponential dependence of the half-lifetime on the current density known from electrical aging is also valid for UV-degradation. The influence of excitons on the degradation of OLEDs is determined and we experimentally distinguish between the influence of singlet and triplet excitons. We conclude that singlet excitons are the main cause of degradation for Spiro-DPVBi(2,2',7,7'-tetrakis(2,2-diphenylvinyl)spiro-9,9'-bifluorene)-based OLEDs by a comparison of the degradation of electrically driven and UV-excited OLEDs.