Highly efficient polaritonic light emitting diodes with angle-independent narrowband emission

Abstract: 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.