In this work, we explore the effects of the ultrastrong coupling regime between light and molecular excitons on the electrical and optical properties of microcavity-OLEDs. We studied two different samples having a coupling value of 31% and 48%. The main effect of the ultrastrong interaction is on the electroluminescent emission linewidth which was only 28 meV, that is about 12-fold narrower than that of the corresponding photoluminescence of the uncoupled material and even half the linewidth of photonic (weak-coupled) microcavity working at the same wavelength.