  Lead-halide perovskites have been attracting attention for potential use in
solid-state lighting. Following the footsteps of solar cells, the field of
perovskite light-emitting diodes (PeLEDs) has been growing rapidly. Their
application prospects in lighting, however, remain still uncertain due to a
variety of shortcomings in device performance including their limited levels of
luminous efficiency achievable thus far. Here we show high-efficiency PeLEDs
based on colloidal perovskite nanocrystals (PeNCs) synthesized at room
temperature possessing dominant first-order excitonic radiation (enabling a
photoluminescence quantum yield of 71% in solid film), unlike in the case of
bulk perovskites with slow electron-hole bimolecular radiative recombination (a
second-order process). In these PeLEDs, by reaching charge balance in the
recombination zone, we find that the Auger nonradiative recombination, with its
significant role in emission quenching, is effectively suppressed in low
driving current density range. In consequence, these devices reach a record
high maximum external quantum efficiency of 12.9% reported to date and an
unprecedentedly high power efficiency of 30.3 lm W-1 at luminance levels above
1000 cd m-2 as required for various applications. These findings suggest that,
with feasible levels of device performance, the PeNCs hold great promise for
their use in LED lighting and displays.
