  Angle-independent, narrowband emission is required for many optoelectronic
devices, ranging from high-definition displays to sensors. However, emerging
materials for electroluminescent devices, such as organics and perovskites,
show spectrally broad emission due to intrinsic disorder. Coupling this
emission to an optical resonance reduces the linewidth, but at the cost of
inheriting the severe angular dispersion of the resonator. Strongly coupling a
dispersionless exciton state to a narrowband optical microcavity could overcome
this issue; however, electrically pumped emission from the resulting polaritons
has been hampered by poor efficiencies. Here, we present a universal concept
for polariton-based emission from state-of-the-art organic LEDs (OLEDs) by
introducing an assistant strong coupling layer, thus avoiding quenching-induced
efficiency losses. We realize red- and green-emitting, narrowband (FWHM <20 nm)
and spectrally tuneable polaritonic OLEDs with up to 10% external quantum
efficiency and high luminance (>20,000 cd m$^{-2}$ at 5 V). Optimizing cavity
detuning and coupling strength allows to achieve emission with
ultralow-dispersion (<10 nm spectral shift at 60{\deg} tilt). These results
have significant implications for on-demand polariton emission and demonstrate
the practical relevance of strong light-matter coupling for next-generation
optoelectronics, particularly display technology.
