  Modifying the energy landscape of existing molecular emitters is an
attractive challenge with favourable outcomes in chemistry and organic
optoelectronic research. It has recently been explored through strong
light-matter coupling studies where the organic emitters were placed in an
optical cavity. Nonetheless, a debate revolves around whether the observed
change in the material properties represents novel coupled system dynamics or
the unmasking of pre-existing material properties induced by light-matter
interactions. Here, for the first time, we examined the effect of strong
coupling in polariton organic light-emitting diodes via time-resolved
electroluminescence studies. We accompanied our experimental analysis with
theoretical fits using a model of coupled rate equations accounting for all
major mechanisms that can result in delayed electroluminescence in organic
emitters. We found that in our devices the delayed electroluminescence was
dominated by emission from trapped charges and this mechanism remained
unmodified in the presence of strong coupling.
