Strong exciton-photon coupling in organic microcavity electroluminescence devices with thiophene/phenylene co-oligomer derivatives

Organic electroluminescence (EL) devices with surface-emitting microcavity structure were fabricated using vapor-deposited films of thiophene/phenylene co-oligomer derivatives, aiming at polariton formation under electrical excitation. Owing to strong coupling between excitons and photons in the device, we demonstrated the formation of cavity polaritons with a large Rabi-splitting energy (2h Omega = 250 meV). Furthermore, efficient relaxation into the bottom of lower polariton branch was confirmed from angle-resolved EL spectra. In excitation-density dependence, the luminance of microcavity EL devices showed a superlinear increase with an elevation of current density indicating a contribution of triplet excitons. (C) 2019 The Japan Society of Applied Physics