Ultrapure and efficient electroluminescence in alkali metal doped inorganic perovskite quantum wires arrays

Alkali metal doping has been widely utilized to regulate metal halide perovskites and improve their luminescence performance. However, due to the discordant tolerance factor caused by the smaller size of potassium and rubidium ions, it is still debatable whether they can be incorporated in the cesium perovskite crystal lattice. Here we provide unambiguous evidence for the formation of Rb+ and K+ substitutionally doped stable perovskite cubic crystal structure in the form of quantum wires embedded in nanoporous alumina template. The suppressed inner defects and enhanced exciton binding energy lead to a reduced non-radiative recombination in the co-doped perovskite quantum wires. The perovskite light-emitting diodes with a maximum external quantum efficiency of 17.5%, 21.2%, 24.9% and 30.1% and a maximum luminance of 1638 cd m−2, 3365 cd m−2, 13,483 cd m−2 and 31,706 cd m−2 for electroluminescence peak of 476 nm (primary-blue), 483 nm (sky-blue), 490 nm (sky-blue) and 512 nm (green) are fabricated respectively. Surprisingly, all devices emit high-color purity light with narrow linewidth of ≤16 nm. Cao et al. report an A-site co-doping strategy by substituting Cs+ cation by alkali metals for perovskite quantum wires embedded in nanoporous alumina template, stabilising the crystal structure and enabling high-colour purity LEDs spanning from blue to green spectral region.